WorldWideScience

Sample records for attitude control

  1. Optimal magnetic attitude control

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Markley, F.L.

    1999-01-01

    Magnetic torquing is attractive as means of control for small satellites. The actuation principle is to use the interaction between the earth's magnetic field and a magnetic field generated by a coil set in the satellite. This control principle is inherently time-varying, and difficult to use...... because control torques can only be generated perpendicular to the local geomagnetic field vector. This has been a serious obstacle for using magnetorquer based control for three-axis stabilization of a low earth orbit satellite. The problem of controlling the spacecraft attitude using only magnetic...

  2. Attitude control and stabilization technology discipline

    Science.gov (United States)

    Sunkel, John W.

    1990-01-01

    Viewgraphs on attitude control and stabilization technology discipline for the Space Station Freedom are presented. Topics covered include: attitude control technologies for multi-user accommodation; flexible dynamics and control; computational control techniques; and automatic proximity operations.

  3. Satellite Attitude Control System Simulator

    Directory of Open Access Journals (Sweden)

    G.T. Conti

    2008-01-01

    Full Text Available Future space missions will involve satellites with great autonomy and stringent pointing precision, requiring of the Attitude Control Systems (ACS with better performance than before, which is function of the control algorithms implemented on board computers. The difficulties for developing experimental ACS test is to obtain zero gravity and torque free conditions similar to the SCA operate in space. However, prototypes for control algorithms experimental verification are fundamental for space mission success. This paper presents the parameters estimation such as inertia matrix and position of mass centre of a Satellite Attitude Control System Simulator (SACSS, using algorithms based on least square regression and least square recursive methods. Simulations have shown that both methods have estimated the system parameters with small error. However, the least square recursive methods have performance more adequate for the SACSS objectives. The SACSS platform model will be used to do experimental verification of fundamental aspects of the satellite attitude dynamics and design of different attitude control algorithm.

  4. Optimal magnetic attitude control

    OpenAIRE

    Wisniewski, Rafal; Markley, F.L.

    1999-01-01

    Magnetic torquing is attractive as means of control for small satellites. The actuation principle is to use the interaction between the earth's magnetic field and a magnetic field generated by a coil set in the satellite. This control principle is inherently time-varying, and difficult to use because control torques can only be generated perpendicular to the local geomagnetic field vector. This has been a serious obstacle for using magnetorquer based control for three-axis stabilization of a ...

  5. Nonlinear Robust Control for Spacecraft Attitude

    Directory of Open Access Journals (Sweden)

    Wang Lina

    2013-07-01

    Full Text Available Nonlinear robust control of the spacecraft attitude with the existence of external disturbances is considered. A robust attitude controller is designed based on the passivity approach the quaternion representation, which introduces the suppression vector of external disturbance into the control law and does not need angular velocity measurement. Stability conditions of the robust attitude controller are given. And the numerical simulation results show the effectiveness of the attitude controller.

  6. Noise screen for attitude control system

    Science.gov (United States)

    Rodden, John J. (Inventor); Stevens, Homer D. (Inventor); Hong, David P. (Inventor); Hirschberg, Philip C. (Inventor)

    2002-01-01

    An attitude control system comprising a controller and a noise screen device coupled to the controller. The controller is adapted to control an attitude of a vehicle carrying an actuator system that is adapted to pulse in metered bursts in order to generate a control torque to control the attitude of the vehicle in response to a control pulse. The noise screen device is adapted to generate a noise screen signal in response to the control pulse that is generated when an input attitude error signal exceeds a predetermined deadband attitude level. The noise screen signal comprises a decaying offset signal that when combined with the attitude error input signal results in a net attitude error input signal away from the predetermined deadband level to reduce further control pulse generation.

  7. Three axis attitude control system

    Science.gov (United States)

    Studer, Philip A. (Inventor)

    1988-01-01

    A three-axis attitude control system for an orbiting body comprised of a motor driven flywheel supported by a torque producing active magnetic bearing is described. Free rotation of the flywheel is provided about its central axis and together with limited angular torsional deflections of the flywheel about two orthogonal axes which are perpendicular to the central axis. The motor comprises an electronically commutated DC motor, while the magnetic bearing comprises a radially servoed permanent magnet biased magnetic bearing capable of producing cross-axis torques on the flywheel. Three body attitude sensors for pitch, yaw and roll generate respective command signals along three mutually orthogonal axes (x, y, z) which are coupled to circuit means for energizing a set of control coils for producing torques about two of the axes (x and y) and speed control of the flywheel about the third (z) axis. An energy recovery system, which is operative during motor deceleration, is also included which permits the use of a high-speed motor to perform effectively as a reactive wheel suspended in the magnetic bearing.

  8. Torque equilibrium attitude control for Skylab reentry

    Science.gov (United States)

    Glaese, J. R.; Kennel, H. F.

    1980-01-01

    The method of torque equilibrium attitude control used to control the reentry of Skylab to an altitude below 150 km without the use of thruster fuel once the attitude was established is discussed. The Skylab attitude and pointing control system, which included rate gyros, sun sensors, star tracker, the Apollo telescope mount digital computer, control moment gyros and cold-gas attitude thrusters, is presented. The 12 torque equilibrium attitudes found at which aerodynamic, gravity gradient and gyroscopic torques would balance are indicated, and the three of those at which the solar power supply would be adequate for attitude control are illustrated. The equilibrium seeking method employed is then examined, and the operation and performance of the torque equilibrium attitude control system during the three weeks prior to Skylab reentry are discussed. It is concluded that the torque equilibrium attitude control method developed for Skylab was successful in performing its assigned mission, and will be valuable for the design of future, low-altitude spacecraft or tethered vehicles.

  9. Attitude control with active actuator saturation prevention

    Science.gov (United States)

    Forbes, James Richard

    2015-02-01

    Spacecraft attitude control in the presence of actuator saturation is considered. The attitude controller developed has two components: a proportional component and an angular velocity component. The proportional control has a special form that depends on the attitude parameterization. The angular velocity control is realized by a strictly positive real system with its own input nonlinearity. The strictly positive real system can filter noise in the angular velocity measurement. With this control architecture the torques applied to the body are guaranteed to be below a predetermined value, thus preventing saturation of the actuators. The closed-loop equilibrium point corresponding to the desired attitude is shown to be asymptotically stable. Additionally, the control law does not require specific knowledge of the body's inertia properties, and is therefore robust to such modelling errors.

  10. Solar Sail Attitude Control Performance Comparison

    Science.gov (United States)

    Bladt, Jeff J.; Lawrence, Dale A.

    2005-01-01

    Performance of two solar sail attitude control implementations is evaluated. One implementation employs four articulated reflective vanes located at the periphery of the sail assembly to generate control torque about all three axes. A second attitude control configuration uses mass on a gimbaled boom to alter the center-of-mass location relative to the center-of-pressure producing roll and pitch torque along with a pair of articulated control vanes for yaw control. Command generation algorithms employ linearized dynamics with a feedback inversion loop to map desired vehicle attitude control torque into vane and/or gimbal articulation angle commands. We investigate the impact on actuator deflection angle behavior due to variations in how the Jacobian matrix is incorporated into the feedback inversion loop. Additionally, we compare how well each implementation tracks a commanded thrust profile, which has been generated to follow an orbit trajectory from the sun-earth L1 point to a sub-L1 station.

  11. Fundamentals of spacecraft attitude determination and control

    CERN Document Server

    Markley, F Landis

    2014-01-01

    This book explores topics that are central to the field of spacecraft attitude determination and control. The authors provide rigorous theoretical derivations of significant algorithms accompanied by a generous amount of qualitative discussions of the subject matter. The book documents the development of the important concepts and methods in a manner accessible to practicing engineers, graduate-level engineering students and applied mathematicians. It includes detailed examples from actual mission designs to help ease the transition from theory to practice, and also provides prototype algorithms that are readily available on the author’s website. Subject matter includes both theoretical derivations and practical implementation of spacecraft attitude determination and control systems. It provides detailed derivations for attitude kinematics and dynamics, and provides detailed description of the most widely used attitude parameterization, the quaternion. This title also provides a thorough treatise of attitu...

  12. A magnetic control system for attitude acquisition

    Science.gov (United States)

    Stickler, A. C.

    1972-01-01

    A spacecraft magnetic attitude acquisition system is reported that is capable of automatically despinning a satellite from arbitrarily high rates around any axis and provides terminal orientation that makes capture by conventional fine control attitude control systems routine. The system consists of a 3-axis magnetometer, a set of 3 orthogonal magnets, and appropriate control logic. A well-configured system results in despin times of the order of 5 orbits per rpm for spacecraft in low earth orbits. Following despin, terminal orientation is achieved after another one to three orbits, depending on the capture range of the associated fine control system.

  13. Experiment D010: Ion sensing attitude control

    Science.gov (United States)

    Sagalyn, R. C.; Smiddy, M.

    1971-01-01

    The feasibility of an attitude control system that uses environmental positive ions and an electrostatic detection system to measure spacecraft pitch and yaw is studied. The secondary objective was to measure the spatial and temporal variations of ambient positively charged particles along the orbital path of the Gemini 10 and 12 spacecrafts. The results proved that the use of a horizon detector in conjunction with pitch and yaw sensors would facilitate complete description of the spacecraft position and attitude. Furthermore, with the addition of a servosystem, the unit could be used as a complete automatic attitude-control system that would be applicable from the lowest satellite altitudes up to at least 10 earth radii. Also, results established that the charge density along the trajectory of the satellite could be determined by transmission of output voltages from the individual electrometers.

  14. Modular Attitude Control System for Microsatellites with Stringent Pointing Requirements

    OpenAIRE

    Grocott, Simon

    2000-01-01

    Advancing technology has allowed for the development of low cost attitude control hardware for microsatellites. However, the attitude control design and software development remain a significant cost driver. The Dynacon High Performance Attitude Control system is a modular control system that makes use of reusable algorithm modules enabling the attitude control system to be applied to several different spacecraft missions with very different performance requirements. The High Performance Atti...

  15. Attitude Determination and Control Systems

    Science.gov (United States)

    Starin, Scott R.; Eterno, John

    2011-01-01

    designing and operating spacecraft pointing (i.e. attitude) systems.

  16. Modular Attitude Determination and Control System for Small Satellites

    OpenAIRE

    Selby, Vaughn

    1990-01-01

    In order to meet the cost goals of small satellites, attitude determination and control problems must be solved using standardized components. Small satellite attitude control systems must feature performance, versatility, and above all, low cost Large, custom designed, high cost attitude control systems have no place in the small satellite community. A modular concept of attitude control is presented which will allow ambitious performance and cost goals to be attained. Basic building blocks ...

  17. Flexible Satellite Attitude Control via Adaptive Fuzzy Linearization

    Institute of Scientific and Technical Information of China (English)

    GUAN Ping; LIU Xiang-dong; CHEN Jia-bin; LIU Xiao-he

    2005-01-01

    The adaptive fuzzy control is combined with input-output linearization control to constitute the hybrid controller. The control method is then applied to the attitude maneuver control of the flexible satellite.The basic control structure is given. The rules of the controller parameter selection, which guarantee the attitude stabilization of the satellite with parameter uncertainties, have been analyzed. Simulation results show that the precise attitude control is accomplished in spite of the uncertainty in the system.

  18. Spacecraft attitude control momentum requirements analysis

    Science.gov (United States)

    Robertson, Brent P.; Heck, Michael L.

    1987-01-01

    The relationship between attitude and angular momentum control requirements is derived for a fixed attitude, Earth orbiting spacecraft with large area articulating appendages. Environmental effects such as gravity gradient, solar radiation pressure, and aerodynamic forces arising from a dynamic, rotating atmosphere are examined. It is shown that, in general, each environmental effect contributes to both cyclic and secular momentum requirements both within and perpendicular to the orbit plane. The gyroscopic contribution to the angular momentum control requirements resulting from a rotating, Earth oriented spacecraft is also discussed. Special conditions are described where one or more components of the angular momentum can be made to vanish, or become purely cyclical. Computer generated plots for a candidate space station configuration are presented to supplement the analytically derived results.

  19. The Magnetic Attitude Control of ABRIXAS

    OpenAIRE

    Komgsmann, Hans; Wiegand, Matthias; Matthews, Oliver

    1995-01-01

    ABRIXAS is a small astronomical satellite planned by the Astrophysical Institute Potsdam (AIP) and the German Space Agency DARA. Its main scientific objective is to survey the total hemisphere; the satellite rotates once per orbit along the sun line, and after half a year the survey mission will be fulfilled. The attitude control system is one of the most critical subsystems with respect to cost and mission success, and an independent study was done. With a momentum biased system, three magne...

  20. Low cost attitude control system scanwheel development

    Science.gov (United States)

    Bialke, William; Selby, Vaughn

    1991-01-01

    In order to satisfy a growing demand for low cost attitude control systems for small spacecraft, development of low cost scanning horizon sensor coupled to a low cost/low power consumption Reaction Wheel Assembly was initiated. This report addresses the details of the versatile design resulting from this effort. Tradeoff analyses for each of the major components are included, as well as test data from an engineering prototype of the hardware.

  1. Spacecraft Attitude Control in Hamiltonian Framework

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    2000-01-01

    The objective of this paper is to give a design scheme for attitude control algorithms of a generic spacecraft. Along with the system model formulated in the Hamilton's canonical form the algorithm uses information about a required potential energy and a dissipative term. The control action is the...... sum of the gradient of the potential energy and the dissipative force. It is shown that this control law makes the system uniformly asymptotically stable to the desired reference point. Three problems were addressed in the paper: spacecraft stabilization in the inertial frame, libration damping with...

  2. Lorentz Force Based Satellite Attitude Control

    Science.gov (United States)

    Giri, Dipak Kumar; Sinha, Manoranjan

    2016-07-01

    Since the inception of attitude control of a satellite, various active and passive control strategies have been developed. These include using thrusters, momentum wheels, control moment gyros and magnetic torquers. In this present work, a new technique named Lorentz force based Coulombic actuators for the active control is proposed. This method uses electrostatic charged shells, which interact with the time varying earth's magnetic field to establish a full three axes control of the satellite. It is shown that the proposed actuation mechanism is similar to a satellite actuated by magnetic coils except that the resultant magnetic moment vanishes under two different conditions. The equation for the required charges on the the Coulomb shells attached to the satellite body axes is derived, which is in turn used to find the available control torque for actuating the satellite along the orbit. Stability of the proposed system for very high initial angular velocity and exponential stability about the origin are proved for a proportional-differential control input. Simulations are carried out to show the efficacy of the proposed system for the attitude control of the earth-pointing satellite.

  3. Chaotic attitude control of satellite using impulsive control

    International Nuclear Information System (INIS)

    Nowadays, attitude control systems of satellites demand better performance, resulting in the application of new advanced nonlinear control theory. In this paper, impulsive control is applied to a six-dimensional system which describes the attitude dynamics of a satellite subjected to deterministic external perturbations which induce chaotic motion when no control is affected. Several theorems on the stability of impulsive control systems are presented. These theorems are then used to find the conditions under which the chaotic systems can be asymptotically controlled to the origin by using impulsive control. Given the parameters of the chaotic system and the impulsive control law, an estimation of the upper bound of the impulse interval is given. Finally, we give some simulations results to visualize the effectiveness and feasibility of the proposed method.

  4. Observer-based Satellite Attitude Control and Simulation Researches

    Institute of Scientific and Technical Information of China (English)

    王子才; 马克茂

    2002-01-01

    Observer design method is applied to the realization of satellite attitude control law baaed on simplified control model. Exact mathematical model of the satellite attitude control system is also constructed, together with the observer-based control law, to conduct simulation research. The simulation results justify the effectiveness andfeasibility of the observer-based control method.

  5. Advanced Attitude Control af Pico Sized Satellites

    DEFF Research Database (Denmark)

    Larsen, Jesper A.; Amini, Rouzbeh; Izadi-Zamanabadi, Roozbeh

    2005-01-01

    The AAU-Cubesat project started in 2001 and led to the launch of the rst AAU-Cubesat and followed up with the second Cubesat project, AAUSAT-II, which carries a combined gamma and X-Ray detector. Due to the precision pointing requirement in the X-Ray sensor it is necessary to realize a pointing...... accuracy of better than 5 degrees. Cost, size, weight and power requirements, on the other hand, impose selecting relative simple sensors and actuators which leads to an attitude control requirement of less than 1 degree. This precision is obtained by a combination of magnetorquers and momentum wheels. The...

  6. Attitude control of a nano satellite

    OpenAIRE

    2010-01-01

    The CubeSTAR satellite is a student satellite project at the University of Oslo. The main mission is to measure the turbulence in the electron plasma using a novel Multi Needle Langmuir Probe system developed at the University of Oslo. In order to get correct measurements, it’s important that the probes are located in the front of the satellite in the orbit velocity direction. In this thesis, the attitude control problem of the CubeSTAR nano-satellite is the main topic. The satellite wil...

  7. Local Vertical/Local Horizontal Attitude Control for Spartan Spacecraft

    OpenAIRE

    Morrissey, James; Olney, David

    1996-01-01

    A Spartan spacecraft attitude control system was reconfigured to provide attitude pointing with respect to a Local Vertical/Local Horizontal reference frame even though the baseline system uses only an initial start attitude, sun sensors, and star tracker/gyros for defining the spacecraft attitude. No earth sensors of any kind are used. Deployed from the orbiter for two days, usually for solar and stellar inertial pointing, Spartan missions use pointing programs that must be written months pr...

  8. Robust Adaptive Attitude Control for Airbreathing Hypersonic Vehicle with Attitude Constraints and Propulsive Disturbance

    OpenAIRE

    Jian Fu; Liangming Wang; Mou Chen; Sijiang Chang

    2015-01-01

    A robust adaptive backstepping attitude control scheme, combined with invariant-set-based sliding mode control and fast-nonlinear disturbance observer, is proposed for the airbreathing hypersonic vehicle with attitude constraints and propulsive disturbance. Based on the positive invariant set and backstepping method, an innovative sliding surface is firstly developed for the attitude constraints. And the propulsive disturbance of airbreathing hypersonic vehicle is described as a differential ...

  9. Optimal Sliding Mode Controllers for Attitude Stabilization of Flexible Spacecraft

    Directory of Open Access Journals (Sweden)

    Chutiphon Pukdeboon

    2011-01-01

    Full Text Available The robust optimal attitude control problem for a flexible spacecraft is considered. Two optimal sliding mode control laws that ensure the exponential convergence of the attitude control system are developed. Integral sliding mode control (ISMC is applied to combine the first-order sliding mode with optimal control and is used to control quaternion-based spacecraft attitude manoeuvres with external disturbances and an uncertainty inertia matrix. For the optimal control part the state-dependent Riccati equation (SDRE and optimal Lyapunov techniques are employed to solve the infinite-time nonlinear optimal control problem. The second method of Lyapunov is used to guarantee the stability of the attitude control system under the action of the proposed control laws. An example of multiaxial attitude manoeuvres is presented and simulation results are included to verify the usefulness of the developed controllers.

  10. Attitude Control System for the Extreme Ultraviolet Explorer Satellite

    Science.gov (United States)

    Wong, E. C.

    1984-01-01

    The requirements, design, and expected performance of the Attitude Control Subsystem for the spin-stabilized Extreme Ultraviolet Explorer Satellite are presented. In the sky-mapping phase, closed-loop magnetic control keeps the spin axis pointed toward the sun. In the spectroscopy phase, the attitude control loop is closed via the ground. The satellite's attitude and spin rate are determined using periodically downlinked star data. An attitude control algorithm generates commands to be uplinked to the satellite for spin axis precession and spin rate control. Computer simulations of the satellite dynamic response, pointing error, and stability during spin axis precession are presented, and parameters that affect the pointing performance are evaluated.

  11. Attitude Controller-Observer Design for the NTNU Test Satellite

    OpenAIRE

    Alvenes, Fredrik

    2013-01-01

    This report presents the results from the development and design of an Attitude Controller-Observer for the NTNU Test Satellite (NUTS). It gives an insight to mathematical modeling of satellite attitude dynamics for 3 degrees of freedom. By the different limitations of how the NUTS operates, these models are adjusted accordingly.A strategy for controlling the attitude is presented. Through an explanation of the magnetic actuators, the control laws are also adapted to work with the NUTS satell...

  12. Three-axis active magnetic attitude control asymptotical study

    Science.gov (United States)

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Penkov, V. I.

    2015-05-01

    Active magnetic attitude control system providing given inertial attitude is considered. Control algorithm is constructed on the basis of a planar motion model. It decreases attitude discrepancy. Alternative approach is based on the PD-controller design. System behavior is analyzed for specific motion cases and sometimes for specific inertia tensor (axisymmetrical satellite) using averaging technique. Overall satellite angular motion is covered. Necessary attitude is found to be accessible for some control parameters. Stability is proven and optimal algorithm parameters are obtained. Floquet-based analysis is performed to verify and broaden analytical results.

  13. Attitude Control Performance of IRVE-3

    Science.gov (United States)

    Dillman, Robert A.; Gsell, Valerie T.; Bowden, Ernest L.

    2013-01-01

    The Inflatable Reentry Vehicle Experiment 3 (IRVE-3) launched July 23, 2012, from NASA Wallops Flight Facility and successfully performed its mission, demonstrating both the survivability of a hypersonic inflatable aerodynamic decelerator in the reentry heating environment and the effect of an offset center of gravity on the aeroshell's flight L/D. The reentry vehicle separated from the launch vehicle, released and inflated its aeroshell, reoriented for atmospheric entry, and mechanically shifted its center of gravity before reaching atmospheric interface. Performance data from the entire mission was telemetered to the ground for analysis. This paper discusses the IRVE-3 mission scenario, reentry vehicle design, and as-flown performance of the attitude control system in the different phases of the mission.

  14. Architecture for Combined Energy and Attitude Control System

    Directory of Open Access Journals (Sweden)

    Ibrahim M. Mehedi

    2005-01-01

    Full Text Available Combining the energy and attitude control system is a feasible technology for small satellites to improve the space missions. In this Combined Energy and Attitude Control System (CEACS a double rotating flywheel is used to replace the conventional battery for energy storage as well as to control the attitude of an earth oriented satellite. Each flywheel is to be controlled in the torque mode. The energy and attitude inputs for the flywheels' control architecture are also in the torque mode. All related mathematical representation along with the relevant transfer functions and the required numerical calculation are developed. The goals are to analyze the attitude performance with respect to the ideal and non-ideal test cases for a chosen reference mission.

  15. Adaptive Jacobian Fuzzy Attitude Control for Flexible Spacecraft Combined Attitude and Sun Tracking System

    Science.gov (United States)

    Chak, Yew-Chung; Varatharajoo, Renuganth

    2016-07-01

    Many spacecraft attitude control systems today use reaction wheels to deliver precise torques to achieve three-axis attitude stabilization. However, irrecoverable mechanical failure of reaction wheels could potentially lead to mission interruption or total loss. The electrically-powered Solar Array Drive Assemblies (SADA) are usually installed in the pitch axis which rotate the solar arrays to track the Sun, can produce torques to compensate for the pitch-axis wheel failure. In addition, the attitude control of a flexible spacecraft poses a difficult problem. These difficulties include the strong nonlinear coupled dynamics between the rigid hub and flexible solar arrays, and the imprecisely known system parameters, such as inertia matrix, damping ratios, and flexible mode frequencies. In order to overcome these drawbacks, the adaptive Jacobian tracking fuzzy control is proposed for the combined attitude and sun-tracking control problem of a flexible spacecraft during attitude maneuvers in this work. For the adaptation of kinematic and dynamic uncertainties, the proposed scheme uses an adaptive sliding vector based on estimated attitude velocity via approximate Jacobian matrix. The unknown nonlinearities are approximated by deriving the fuzzy models with a set of linguistic If-Then rules using the idea of sector nonlinearity and local approximation in fuzzy partition spaces. The uncertain parameters of the estimated nonlinearities and the Jacobian matrix are being adjusted online by an adaptive law to realize feedback control. The attitude of the spacecraft can be directly controlled with the Jacobian feedback control when the attitude pointing trajectory is designed with respect to the spacecraft coordinate frame itself. A significant feature of this work is that the proposed adaptive Jacobian tracking scheme will result in not only the convergence of angular position and angular velocity tracking errors, but also the convergence of estimated angular velocity to

  16. The Submillimeter Wave Astronomy Satellite Attitude Control Software Design

    OpenAIRE

    Anderson, Mark; Wennersten, Miriam; Bonnett, Joseph; Hill, Adrian

    1995-01-01

    The Submilimeter Wave Astronomy Satellite (SWAS) was selected for flight by NASA in 1989 as a part of the Small Explorer (SMEX) program. SWAS's primary science objective is to conduct high spectral resolution surveys of galactic molecular clouds. The SWAS Attitude Control System (ACS) is three-axis controlled, zero momentum stabilized, and is capable of performing subarcminute pointing. This paper will discuss the design of the software components which comprise the Attitude Control System So...

  17. Pulsed Electrogasdynamic Thruster for Attitude Control and Orbit Maneuver Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A new pulsed electric thruster, named "pulsed electrogasdynamic thruster," for attitude control and orbit maneuver is proposed. In this thruster, propellant gas is...

  18. Pulsed Electrogasdynamic Thruster for Attitude Control and Orbit Maneuver Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In the Phase I program we successfully demonstrated the feasibility of the Pulsed ElectroGasdynamic (PEG) thruster for attitude control and orbital maneuvering. In...

  19. Variable structure attitude maneuver and vibration control of flexible spacecraft

    Institute of Scientific and Technical Information of China (English)

    HU Qing-lei; MA Cuang-fu

    2008-01-01

    A dual-stage control system design method is presented for the three-axis-rotational maneuver and vibration stabilization of a spacecraft with flexible appendages embedded with piezoceramics as sensor and actuator.In this design approach,the attitude control and the vibration suppression sub-systems ale designed separately using the lower order model.The design of attitude controller is based on the variable structure control (VSC)theory leading to a discontinuous control law.This controller accomplishes asymptotic attitude maneuvering in the closed-loop system and is insensitive to the interaction of elastic modes and uncertainty in the system.To actively suppress the flexible vibrations,the modal velocity feedback control method is presented by using piezoelectric materials as additional sensor and actuator bonded on the surface of the flexible appendages.In addition,a special configuration of actuators for three-axis attitude control is also investigated:the pitch attitude controlled by a momentum wheel,and the roll/yaw control achieved by on-off thrustem.which is modulated by pulse width pulse frequency modulation technique to construct the proper control torque history.Numerical simulations performed show that the rotational maneuver and vibration suppression ale accomplished in spite of the presence of disturbance torque and parameter uncertainty.

  20. The Design of the OPAL Attitude Control System

    OpenAIRE

    Jung, Jaewoo; Kuzuya, Naoki; Alvarez, Jaime

    1996-01-01

    OPAL's attitude is controlled by using two pairs of magnetic coils and a three axis magnetometer. One pair of coils is mounted on the side panel where the picosatellite launch window is located. The other pair is mounted on the bottom panel. The primary requirements of the attitude control system are to decease spin of the satellite with respect to its body axis to minimize disturbances during picosatellite launch, and to spin up the satellite once the picosatellite is launched to meet therma...

  1. Autonomous spacecraft attitude control using magnetic torquing only

    Science.gov (United States)

    Musser, Keith L.; Ebert, Ward L.

    1989-01-01

    Magnetic torquing of spacecraft has been an important mechanism for attitude control since the earliest satellites were launched. Typically a magnetic control system has been used for precession/nutation damping for gravity-gradient stabilized satellites, momentum dumping for systems equipped with reaction wheels, or momentum-axis pointing for spinning and momentum-biased spacecraft. Although within the small satellite community there has always been interest in expensive, light-weight, and low-power attitude control systems, completely magnetic control systems have not been used for autonomous three-axis stabilized spacecraft due to the large computational requirements involved. As increasingly more powerful microprocessors have become available, this has become less of an impediment. These facts have motivated consideration of the all-magnetic attitude control system presented here. The problem of controlling spacecraft attitude using only magnetic torquing is cast into the form of the Linear Quadratic Regulator (LQR), resulting in a linear feedback control law. Since the geomagnetic field along a satellite trajectory is not constant, the system equations are time varying. As a result, the optimal feedback gains are time-varying. Orbit geometry is exploited to treat feedback gains as a function of position rather than time, making feasible the onboard solution of the optimal control problem. In simulations performed to date, the control laws have shown themselves to be fairly robust and a good candidate for an onboard attitude control system.

  2. The development and demonstration of hybrid programmable attitude control electronics

    Science.gov (United States)

    Smith, L. S.; Kopf, E. H., Jr.

    1973-01-01

    In the course of extended life attitude control system (ELACS) research sponsored by NASA a hybrid programable attitude control electronics (HYPACE) concept was developed and demonstrated. The wide variety of future planetary missions demanded a new control approach to accommodate the automatic fault tolerance and long the life requirements of such missions. HYPACE provides an adaptable, analog/digital design approach that permits preflight and in-flight accommodation of mission changes, component performance variations, and spacecraft changes, through programing. This enabled broad multimission flexibility of application in a cost effective manner. Previously, flight control computers have not been not flown on planetary missions because of weight and power problems. These problems were resolved in the design of HYPACE. The HYPACE design, which was demonstrated in breadboard form on a single-axis gas-bearing spacecraft simulation, uses a single control channel to perform the attitude control functions sequentially, thus significantly reducing the number of component parts over hard-wired designs.

  3. Robustness and Actuator Bandwidth of MRP-Based Sliding Mode Control for Spacecraft Attitude Control Problems

    Science.gov (United States)

    Keum, Jung-Hoon; Ra, Sung-Woong

    2009-12-01

    Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters (MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

  4. ISS Contingency Attitude Control Recovery Method for Loss of Automatic Thruster Control

    Science.gov (United States)

    Bedrossian, Nazareth; Bhatt, Sagar; Alaniz, Abran; McCants, Edward; Nguyen, Louis; Chamitoff, Greg

    2008-01-01

    In this paper, the attitude control issues associated with International Space Station (ISS) loss of automatic thruster control capability are discussed and methods for attitude control recovery are presented. This scenario was experienced recently during Shuttle mission STS-117 and ISS Stage 13A in June 2007 when the Russian GN&C computers, which command the ISS thrusters, failed. Without automatic propulsive attitude control, the ISS would not be able to regain attitude control after the Orbiter undocked. The core issues associated with recovering long-term attitude control using CMGs are described as well as the systems engineering analysis to identify recovery options. It is shown that the recovery method can be separated into a procedure for rate damping to a safe harbor gravity gradient stable orientation and a capability to maneuver the vehicle to the necessary initial conditions for long term attitude hold. A manual control option using Soyuz and Progress vehicle thrusters is investigated for rate damping and maneuvers. The issues with implementing such an option are presented and the key issue of closed-loop stability is addressed. A new non-propulsive alternative to thruster control, Zero Propellant Maneuver (ZPM) attitude control method is introduced and its rate damping and maneuver performance evaluated. It is shown that ZPM can meet the tight attitude and rate error tolerances needed for long term attitude control. A combination of manual thruster rate damping to a safe harbor attitude followed by a ZPM to Stage long term attitude control orientation was selected by the Anomaly Resolution Team as the alternate attitude control method for such a contingency.

  5. Fuzzy robust attitude controller design for hydrofoil catamaran

    Institute of Scientific and Technical Information of China (English)

    Ren Junsheng; Yang Yansheng

    2005-01-01

    A robust attitude controller for hydrofoil catamaran throughout its operating envelope is proposed, based on Tagaki-Sugeno (T-S) fuzzy model. Firstly, T-S fuzzy model and robust attitude control strategy for hydrofoil catamaran is presented by use of linear matrix inequality (LMI) techniques. Secondly, a nonlinear mathematical model of hydrofoil catamaran is established, acting as the platform for further researches. The specialty in interpolation of T-S fuzzy model guarantees that feedback gain can be obtained smoothly, while boat's speed is shifting over the operating envelope. The external disturbances are also attenuated to achieve H∞ control performance, meanwhile. Finally, based on such a boat,HC200B-A1, simulation researches demonstrate the design procedures and the effectiveness of fuzzy robust attitude controller.

  6. Global Observer-based Attitude Controller Using Direct Inertial Measurements

    Directory of Open Access Journals (Sweden)

    Saâdi Bouhired

    2014-04-01

    Full Text Available In this work, we address the problem of global attitude control using direct inertial measurements. When using direct inertial measurement to observe the rigid body attitude, it is shown that due to a geometrical obstruction, it is impossible to achieve global asymptotic stability. In fact, for a particular initial condition the tracking error quaternion converges to a pure imaginary quaternion formed by an eigenvector of a characteristic matrix related to the inertial constant and known vectors. Our proposition consists of adding a dynamic signal to force the rigid body to escape from such a situation. The proposed observer-based controller is synthesized based on a single Lyapunov function and a stability analysis shows that the controller stabilizes globally and asymptotically the rigid body attitude at the desired one. The effectiveness of the proposed observer-based controller is confirmed by simulation results.

  7. Sliding Mode Attitude Control for Magnetic Actuated Satellite

    OpenAIRE

    Wisniewski, Rafal

    1998-01-01

    Magnetic torquing is attractive as a control principle on small satellites. The actuation principle is to use the interaction between the earth's magnetic field and magnetic field generated by a coil set in the satellite. This control principle is inherently nonlinear, and difficult to use because control torques can only be generated perpendicular to the local geomagnetic field vector. This has been a serious obstacle for using magnetorquer based control for three-axis attitude control. This...

  8. NASA Workshop on Hybrid (Mixed-Actuator) Spacecraft Attitude Control

    Science.gov (United States)

    Dennehy, Cornelius J.; Kunz, Nans

    2014-01-01

    At the request of the Science Mission Directorate Chief Engineer, the NASA Technical Fellow for Guidance, Navigation & Control assembled and facilitated a workshop on Spacecraft Hybrid Attitude Control. This multi-Center, academic, and industry workshop, sponsored by the NASA Engineering and Safety Center (NESC), was held in April 2013 to unite nationwide experts to present and discuss the various innovative solutions, techniques, and lessons learned regarding the development and implementation of the various hybrid attitude control system solutions investigated or implemented. This report attempts to document these key lessons learned with the 16 findings and 9 NESC recommendations.

  9. Applications software supporting the Spartan Attitude Control System

    Science.gov (United States)

    Stone, R. W.

    1986-01-01

    The native software supporting a single mission for the Spartan Attitude Control System can require up to 40,000 lines of code. Most of this must be rewritten for each mission. Control system engineers use an array of Applications Software Packages residing in ground computers to write each mission's flight software. These Applications Packages are written in the 'C' programming language and run under the UNIX Operating System. This paper discusses each of the Attitude Control Applications Software Packages, and describes the purpose and design of each.

  10. Precision Attitude Control for the BETTII Balloon-Borne Interferometer

    Science.gov (United States)

    Benford, Dominic J.; Fixsen, Dale J.; Rinehart. Stephen

    2012-01-01

    The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared interferometer to fly on a high altitude balloon. Operating at wavelengths of 30-90 microns, BETTII will obtain spatial and spectral information on science targets at angular resolutions down to less than half an arcsecond, a capability unmatched by other far-infrared facilities. This requires attitude control at a level ofless than a tenth of an arcsecond, a great challenge for a lightweight balloon-borne system. We have designed a precision attitude determination system to provide gondola attitude knowledge at a level of 2 milliarcseconds at rates up to 100Hz, with accurate absolute attitude determination at the half arcsecond level at rates of up to 10Hz. A mUlti-stage control system involving rigid body motion and tip-tilt-piston correction provides precision pointing stability to the level required for the far-infrared instrument to perform its spatial/spectral interferometry in an open-loop control. We present key aspects of the design of the attitude determination and control and its development status.

  11. SDRE Based Attitude Control Using Modified Rodriguez Parameters

    CERN Document Server

    Doruk, R Ozgur

    2011-01-01

    The purpose of this paper is to present an application of the State Dependent Riccati Equation (SDRE) method to satellite attitude control where the satellite kinematics is modeled by Modified Rodriguez Parameters (MRP). The SDRE methodology is applicable on special forms of nonlinear systems where satellite model is one of the candidates. It is not easy to find an analytical solution from the SDRE. Thus point wise solutions are interpolated with respect to the operating conditions. The point wise solutions are obtained from the MATLAB algorithms which are derived from the positive definite solutions of the SDRE. The global stability analysis is difficult due to the nature of the methodology. The resultant attitude controllers outside the breakpoints (the selected operating conditions for interpolation) are suboptimal. The performance of the designs is examined by simulations on MATLAB - Simulink environment. The simulation results show that, the designed attitude controllers are working satisfactorily even i...

  12. Sliding Mode Attitude Control for Magnetic Actuated Satellite

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    1998-01-01

    Magnetic torquing is attractive as a control principle on small satellites. The actuation principle is to use the interaction between the earth's magnetic field and magnetic field generated by a coil set in the satellite. This control principle is inherently nonlinear, and difficult to use because...... control torques can only be generated perpendicular to the local geomagnetic field vector. This has been a serious obstacle for using magnetorquer based control for three-axis attitude control. This paper deals with three-axis stabilization of a low earth orbit satellite. The problem of controlling the...... spacecraft attitude using only magnetic torquing is realized in the form of the sliding mode control. A three dimensional sliding manifold is proposed, and it is shown that the satellite motion on the sliding manifold is asymptotically stable...

  13. Prospects of Relative Attitude Control Using Coulomb Actuation

    Science.gov (United States)

    Schaub, Hanspeter; Stevenson, Daan

    2013-12-01

    The relative attitude is studied between two charge controlled spacecraft being held at a fixed separation distance. While one body has a spherical shape, the 2nd body is assumed to be non-spherical and tumbling. The attitude control goal is to arrest the rotation of the 2nd body. While prior work has identified the existence of torques between charged bodies, this is the first analytical study on a charged feedback attitude control. Using the recently developed multi-sphere method to provide a simplified electrostatic force and torque model between non-spherical shapes, Lyapunov theory is used to develop a stabilizing attitude control using spacecraft potential as the control variable. Zero and non-zero equilibrium potentials are considered, with the later suitable for the electrostatic tug concept. With a pulling configuration, the cylinder will come to rest with the long axis aligned with the inter-vehicle axis in a stable configuration. For a pusher, the cylinder will settle 90 degrees rotated from this axis. Numerical simulations illustrate the control performance.

  14. A novel single thruster control strategy for spacecraft attitude stabilization

    Science.gov (United States)

    Godard; Kumar, Krishna Dev; Zou, An-Min

    2013-05-01

    Feasibility of achieving three axis attitude stabilization using a single thruster is explored in this paper. Torques are generated using a thruster orientation mechanism with which the thrust vector can be tilted on a two axis gimbal. A robust nonlinear control scheme is developed based on the nonlinear kinematic and dynamic equations of motion of a rigid body spacecraft in the presence of gravity gradient torque and external disturbances. The spacecraft, controlled using the proposed concept, constitutes an underactuated system (a system with fewer independent control inputs than degrees of freedom) with nonlinear dynamics. Moreover, using thruster gimbal angles as control inputs make the system non-affine (control terms appear nonlinearly in the state equation). This necessitates the control algorithms to be developed based on nonlinear control theory since linear control methods are not directly applicable. The stability conditions for the spacecraft attitude motion for robustness against uncertainties and disturbances are derived to establish the regions of asymptotic 3-axis attitude stabilization. Several numerical simulations are presented to demonstrate the efficacy of the proposed controller and validate the theoretical results. The control algorithm is shown to compensate for time-varying external disturbances including solar radiation pressure, aerodynamic forces, and magnetic disturbances; and uncertainties in the spacecraft inertia parameters. The numerical results also establish the robustness of the proposed control scheme to negate disturbances caused by orbit eccentricity.

  15. Active Vibration Control of Satellite Flexible Structures during Attitude Maneuvers

    OpenAIRE

    Saeed Hemmati; Morteza Shahravi; Keramat Malekzadeh

    2013-01-01

    The purpose of this study is controlling active vibration of satellite flexible structures during attitude maneuvers. A smart structure is a structure which is able to sense and control active reaction to any external factors and stimulation. As it comes from the definition of smart structures, development of this knowledge depends on the materials science development, theories and strategies for control. In materials science, smart materials are developed in such a way that they are able to ...

  16. Research on Attitude System of Active Magnetic Control Small Satellite

    OpenAIRE

    Zhaowei, Sun; Di, Yang

    1998-01-01

    When enter orbit, small satellite often tumble as a result of disturbance. How to capture it promptly with finite magnetic torque is an important problem. Because of the coupling of dynamics and control, the small satellite control system is a nonlinear attitude control system with bounds. For high direction and steady precision, an effective method must be found. In this paper, combining with the bound conditions of magnetic torque, two methods are researched. The first is energy method. It ...

  17. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    Science.gov (United States)

    Burk, Thomas A.

    2013-01-01

    The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

  18. Low cost attitude control system reaction wheel development

    Science.gov (United States)

    Bialke, William

    1991-01-01

    In order to satisfy a growing demand for low cost attitude control systems for small spacecraft, development of a low power and low cost Reaction Wheel Assembly was initiated. The details of the versatile design resulting from this effort are addressed. Tradeoff analyses for each of the major components are included, as well as test data from an engineering prototype of the hardware.

  19. Feedforward attitude control for a TDRS with mobile antennas

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, feedforward attitude control law for a Tracking and Data Relay Satellite (TDRS) with mobile antennas is proposed. To track or point the target spacecraft with median/law orbit, the large mobile antennas have to move in a wide range. The movement of such mobile antennas disturbs the satellite attitude consequently. Conventionally, the main body of the satellite and the mobile antennas are controlled independently.The proposed controller first estimates the angular momentum which the mobile antennas will produce based on the momentum conservation equation. Next, it computes the desired velocity of reaction wheels to compensate the disturbance due to the antenna motion. It then adds the error of the wheels' velocity between a desired one and a current value as a feedforward signal to the control system. The proposed controller is demonstrated using a mathematical simulation, of which these results coincide well with analytical results.

  20. Orbit and attitude control of spacecraft formation flying

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-guo; LI Jun-feng

    2008-01-01

    Formation flying is a novel concept of distributing the flmctionality of large spacecraft among several smaller, less expensive, cooperative satellites. Some applica-tions require that a controllable satellite keeps relative position and attitude to observe a specific surface of another satellite among the cluster. Specially, the target space vehi- cle is malfunctioning. The present paper focuses on the problem that how to control a chaser satellite to fly around an out-of-work target satellite closely in earth orbit and to track a specific surface. Relative attitude and first approximate relative orbital dynamics equations are presented. Control strategy is derived based on feedback linearization and Lyapunov theory of stability. Further, considering the uncertainty of inertia, an adaptive control method is developed to obtain the correct inertial ratio. The numerical simulation is given to verify the validity of proposed control scheme.

  1. Attitude Control on the Pico Satellite Solar Cell Testbed-2

    OpenAIRE

    Janson, Siegfried; Hardy, Brian; Chin, Andrew; Rumsey, Daniel; Ehrlich, Daniel; Hinkley, David

    2012-01-01

    The Pico Satellite Solar Cell Testbed-2 (PSSCT-2) was a 5” x 5” x 10”, 3.7-kg mass nanosatellite ejected from the Space Shuttle Atlantis during the final STS-135 mission on July 20, 2011. PSSCT-2 had a three-axis attitude control system to enable firing of solid rockets for orbit raising, pointing of solar cells normal to the sun for on-orbit performance monitoring, and pointing of a GPS antenna in the anti-flight direction for radio-occultation measurements. Attitude determination and contro...

  2. The SAS-3 attitude control system

    Science.gov (United States)

    Mobley, F. F.; Konigsberg, R.; Fountain, G. H.

    1975-01-01

    SAS-3 uses a reaction wheel to provide torque to control the spin rate. If the wheel speed becomes too great or too small, it must be restored to its nominal rate by momentum dumping which is done by magnetic torquing against the earth's magnetic field by the satellite's magnetic coils. A small rate-integrating gyro is used to sense the spin rate so that closed loop control of the spin rate can be achieved. These various systems are described in detail including the reaction wheel system, the gyro system, along with control modes (spin rate control and the star lock mode).

  3. Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters

    Science.gov (United States)

    Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith

    2016-01-01

    NASA is providing preliminary design and requirements for the Space Launch System Exploration Upper Stage (EUS). The EUS will provide upper stage capability for vehicle ascent as well as on-orbit control capability. Requirements include performance of on-orbit burn to provide Orion vehicle with escape velocity. On-orbit attitude control is accommodated by a on-off Reaction Control System (RCS). Paper provides overview of approaches for design and stability of an attitude control system using a RCS.

  4. Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter

    Science.gov (United States)

    Calhoun, Philip C.; Garrick, Joseph C.

    2007-01-01

    The Lunar Reconnaissance Orbiter (LRO) mission is the first of a series of lunar robotic spacecraft scheduled for launch in Fall 2008. LRO will spend at least one year in a low altitude polar orbit around the Moon, collecting lunar environment science and mapping data to enable future human exploration. The LRO employs a 3-axis stabilized attitude control system (ACS) whose primary control mode, the "Observing mode", provides Lunar Nadir, off-Nadir, and Inertial fine pointing for the science data collection and instrument calibration. The controller combines the capability of fine pointing with that of on-demand large angle full-sky attitude reorientation into a single ACS mode, providing simplicity of spacecraft operation as well as maximum flexibility for science data collection. A conventional suite of ACS components is employed in this mode to meet the pointing and control objectives. This paper describes the design and analysis of the primary LRO fine pointing and attitude re-orientation controller function, known as the "Observing mode" of the ACS subsystem. The control design utilizes quaternion feedback, augmented with a unique algorithm that ensures accurate Nadir tracking during large angle yaw maneuvers in the presence of high system momentum and/or maneuver rates. Results of system stability analysis and Monte Carlo simulations demonstrate that the observing mode controller can meet fine pointing and maneuver performance requirements.

  5. Voyager Saturn encounter attitude and articulation control experience

    Science.gov (United States)

    Carlisle, G.; Hill, M.

    1981-01-01

    The Voyager attitude and articulation control system is designed for a three-axis stabilized spacecraft; it uses a biasable sun sensor and a Canopus Star Tracker (CST) for celestial control, as well as a dry inertial reference unit, comprised of three dual-axis dry gryos, for inertial control. A series of complex maneuvers was required during the first of two Voyager spacecraft encounters with Saturn (November 13, 1980); these maneuvers involved rotating the spacecraft simultaneously about two or three axes while maintaining accurate pointing of the scan platform. Titan and Saturn earth occulation experiments and a ring scattering experiment are described. Target motion compensation and the effects of celestial sensor interference are also considered. Failure of the CST, which required an extensive reevaluation of the star reference and attitude control mode strategy, is discussed. Results analyzed thus far show that the system performed with high accuracy, gathering data deeper into Saturn's atmosphere than on any previous planetary encounter.

  6. Preliminary Attitude Control Studies for the ASTER Mission

    International Nuclear Information System (INIS)

    This work discusses an attitude control study for the ASTER mission, the first Brazilian mission to the deep space. The study is part of a larger scenario that is the development of optimal trajectories to navigate in the 2001 SN263 asteroid system, together with the generation of orbit and attitude controllers for autonomous operation. The spacecraft attitude is defined from the orientation of the body reference system to the Local Vertical Local Horizontal (LVLH) of a circular orbit around the Alpha asteroid. The rotational equations of motion involve the dynamic equations, where the three angular speeds are generated from a set of three reaction wheels and the gravitational torque. The rotational kinematics is represented in the Euler angles format. The controller is developed via the linear quadratic regulator approach with output feedback. It involves the generation of a stability augmentation (SAS) loop and a tracking outer loop, with a compensator of desired structure. It was chosen the feedback of the p, q and r angular speeds in the SAS, one for each reaction wheel. In the outer loop, it was chosen a proportional integral compensator. The parameters are tuned using a numerical minimization that represents a linear quadratic cost, with weightings in the tracking error and controls. Simulations are performed with the nonlinear model. For small angle manoeuvres, the linear results with reaction wheels or thrusters are reasonable, but, for larger manoeuvres, nonlinear control techniques shall be applied, for example, the sliding mode control

  7. Attitude-Control Algorithm for Minimizing Maneuver Execution Errors

    Science.gov (United States)

    Acikmese, Behcet

    2008-01-01

    A G-RAC attitude-control algorithm is used to minimize maneuver execution error in a spacecraft with a flexible appendage when said spacecraft must induce translational momentum by firing (in open loop) large thrusters along a desired direction for a given period of time. The controller is dynamic with two integrators and requires measurement of only the angular position and velocity of the spacecraft. The global stability of the closed-loop system is guaranteed without having access to the states describing the dynamics of the appendage and with severe saturation in the available torque. Spacecraft apply open-loop thruster firings to induce a desired translational momentum with an extended appendage. This control algorithm will assist this maneuver by stabilizing the attitude dynamics around a desired orientation, and consequently minimize the maneuver execution errors.

  8. Satellite Attitude Control Using Only Electromagnetic Actuation

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    The primary purpose of this work was to develop control laws for three axis stabilization of a magnetic actuated satellite. This was achieved by a combination of linear and nonlinear system theory. In order to reach this goal new theoretical results were produced in both fields. The focus of the ...

  9. Fully magnetic sliding mode control for acquiring three-axis attitude

    Science.gov (United States)

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Penkov, V. I.; Tkachev, S. S.; Mashtakov, Y. V.

    2016-04-01

    Satellite equipped with purely magnetic attitude control system is considered. Sliding mode control is used to achieve three-axis satellite attitude. Underactuation problem is solved for transient motion. Necessary attitude is acquired by proper sliding manifold construction. Satellite motion on the manifold is executed with magnetic control system. One manifold construction approach is proposed and discussed. Numerical examples are provided.

  10. Locus of Control and Attitude toward Eating in a Female College Population.

    Science.gov (United States)

    Groth-Marnat, Gary; Scumaker, Jack F.

    1988-01-01

    Investigated relationship between locus of control and attitude to food intake in 101 female college students. Results indicated that locus of control was unable to predict attitudes toward eating and fear of becoming overweight. Thesis that locus of control would be related to attitude toward food intake was not supported. (Author/NB)

  11. Flexible Dynamics and Attitude Control of a Square Solar Sail

    Science.gov (United States)

    Choi, Mirue

    This thesis presents a comprehensive analysis of attitude and structural dynamics of a square solar sail. In particular, this research examines the use of corner-attached reflective vanes to control the attitude of the spacecraft. An introduction to known solar sail designs is given, then the mathematics involved in calculating solar radiation pressure forces are presented. A detailed derivation and implementation of the unconstrained nonlinear flexible structural dynamics with Finite Element Method (FEM) models are explored, with several sample simulations of published large deflection experiments used as verification measures. To simulate the inability of a thin membrane to resist compression, the sail membrane elements are augmented with a method that approximates the wrinkling and the slacking dynamics, which is followed by a simulation of another well-known experiment as a verification measure. Once the structural dynamics are established, the usage of the tip vanes is explored. Specifically, a control allocation problem formed by having two degrees of freedom for each tip vane is defined and an efficient solution to this problem is presented, allowing desired control torques to be converted to appropriate vane angles. A randomized testing mechanism is implemented to show the efficacy of this algorithm. The sail shadowing problem is explored as well, where a component of the spacecraft casts shadow upon the sail and prevents solar radiation pressure force from being produced. A method to calculate the region of shadow is presented, and two different shadowing examples are examined --- due to the spacecraft bus, and due to the sail itself. Combining all of the above, an attitude control simulation of the sail model is presented. A simple PD controller combined with the control allocation scheme is used to provide the control torque for the sail, with which the spacecraft must orient towards a number of pre-specified attitude targets. Several attitude

  12. Satellite Attitude Control Using Only Electromagnetic Actuation

    OpenAIRE

    Wisniewski, Rafal

    1997-01-01

    The primary purpose of this work was to develop control laws for three axis stabilization of a magnetic actuated satellite. This was achieved by a combination of linear and nonlinear system theory. In order to reach this goal new theoretical results were produced in both fields. The focus of the work was on the class of periodic systems reflecting orbital motion of the satellite. In addition to a theoretical treatment, the thesis contains a large portion of application considerations. The con...

  13. Attitude Control System Design for Fast Rest-to-Rest Attitude Maneuver

    Science.gov (United States)

    Sakai, S.-I.; Bando, N.; Hashimoto, T.; Murata, Y.; Mochizuki, N.; Nakamura, T.; Kamiya, T.; Ogura, N.; Maeda, K.

    2009-08-01

    The VSOP-2 project is a new space VLBI (very long baseline interferometer) radio astronomy mission, proposed to inherit the fruitful success of the VSOP mission with the HALCA satellite. One of the most important advances of VSOP-2 is the use of higher observation frequency, which requires fast alternating observation of a target and calibrator in order to remove the phase changes caused by the atmosphere. Typically, both sources must be observed within 60 sec, and this switching must be carried out over many hours. ``ASTRO-G" is a satellite planned for this VSOP-2 project, and one of technical challenges is to achieve such fast rest-to-rest maneuvers, and the proper hardware must be selected to account for this fast attitude maneuver. The controlled momentum gyro (CMG) is an actuator that provides high torque with small power consumption, and the fiber optical gyro is a sensor able to measure the high angular velocity with excellent accuracy. This paper first describes these components for attitude control. Another challenge of the ASTRO-G's attitude control system is to design the switching for the flexible mode of the satellite structure, containing a large deployable reflector and a large solar panel. These produce resonances with fast switching and these must be attenuated. To achieve high agility in a flexible satellite, the controller design is crucial. One design feature is a novel robust input shaper named ``nil mode exciting profiler". Another feature is the feedback controller design. The paper describes these features and other potential problems with fast switching..

  14. Satellite Attitude Control Utilizing the Earth's Magnetic Field

    Science.gov (United States)

    White, John S.; Shigemoto, Fred H.; Bourquin, Kent

    1961-01-01

    A study was conducted to determine the feasibility of a satellite attitude fine-control system using the interaction of the earth's magnetic field with current-carrying coils to produce torque. The approximate intensity of the earth's magnetic field was determined as a function of the satellite coordinates. Components of the magnetic field were found to vary essentially sinusoidally at approximately twice orbital frequency. Amplitude and distortion of the sinusoidal components were a function of satellite orbit. Two systems for two-axis attitude control evolved from this study, one using three coils and the other using two coils. The torques developed by the two systems differ only when the component of magnetic field along the tracking line is zero. For this case the two-coil system develops no torque whereas the three-coil system develops some effective torque which allows partial control. The equations which describe the three-coil system are complex in comparison to those of the two-coil system and require the measurement of all three components of the magnetic field as compared with only one for the two-coil case. Intermittent three-axis torquing can also be achieved. This torquing can be used for coarse attitude control, or for dumping the stored momentum of inertia reaction wheels. Such a system has the advantage of requiring no fuel aboard the satellite. For any of these magnetic torquing schemes the power required to produce the magnetic moment and the weight of the coil seem reasonable.

  15. Geometric Tracking Control of the Attitude Dynamics of a Rigid Body on SO(3)

    OpenAIRE

    Lee, Taeyoung

    2010-01-01

    This paper provides new results for a tracking control of the attitude dynamics of a rigid body. Both of the attitude dynamics and the proposed control system are globally expressed on the special orthogonal group, to avoid complexities and ambiguities associated with other attitude representations such as Euler angles or quaternions. By selecting an attitude error function carefully, we show that the proposed control system guarantees a desirable tracking performance uniformly for nontrivial...

  16. Attitude and Translation Control of a Solar Sail Vehicle

    Science.gov (United States)

    Singh, Gurkirpal

    2008-01-01

    A report discusses the ability to control the attitude and translation degrees-of-freedom of a solar sail vehicle by changing its center of gravity. A movement of the spacecraft s center of mass causes solar-pressure force to apply a torque to the vehicle. At the compact core of the solar-sail vehicle lies the spacecraft bus which is a large fraction of the total vehicle mass. In this concept, the bus is attached to the spacecraft by two single degree-of-freedom linear tracks. This allows relative movement of the bus in the sail plane. At the null position, the resulting solar pressure applies no torque to the vehicle. But any deviation of the bus from the null creates an offset between the spacecraft center of mass and center of solar radiation pressure, resulting in a solar-pressure torque on the vehicle which changes the vehicle attitude. Two of the three vehicle degrees of freedom can be actively controlled in this manner. The third, the roll about the sunline, requires a low-authority vane/propulsive subsystem. Translation control of the vehicle is achieved by directing the solar-pressure-induced force in the proper inertial direction. This requires attitude control. Attitude and translation degrees-of-freedom are therefore coupled. A guidance law is proposed, which allows the vehicle to stationkeep at an appropriate point on the inertially-rotating Sun-Earth line. Power requirements for moving the bus are minimal. Extensive software simulations have been performed to demonstrate the feasibility of this concept.

  17. Stepping through versatile attitude control system design for stratospheric platforms

    OpenAIRE

    Boscaleri, A.; Baldi, M; F. CALONACI; Rissone, P.; Rotini, F.

    2005-01-01

    In addition to stepping through the typical hardware parts of an Attitude Control System borne for stratospheric platform, the paper describes some fast position sensors. The use of two axis magnetometers at high latitude, even though with a lower accuracy, is analyzed. A high-accuracy motorized sun tracker based on a Position Sensitive Detector photodiode capable of driving the gondola in pointing or scanning mode in any given arbitrary anti-sun direction is also presented. Lastly, as an imp...

  18. Entry Attitude Controller for the Mars Science Laboratory

    Science.gov (United States)

    Brugarolas, Paul B.; SanMartin, A. Miguel; Wong, Edward C.

    2007-01-01

    This paper describes the preliminary concept for the RCS 3-axis attitude controller for the exo-atmospheric and guided entry phases of the Mars Science Laboratory Entry, Descend and Landing. The entry controller is formulated as three independent channels in the control frame, which is nominally aligned with the stability frame. Each channel has a feedfoward and a feedback. The feedforward path enables fast response to large bank commands. The feedback path stabilizes the vehicle angle of attack and sideslip around its trim position, and tracks bank commands. The feedback path has a PD/D structure with deadbands that minimizes fuel usage. The performance of this design is demonstrated via simulation.

  19. Colloid Thruster for Attitude Control Systems (ACS) and Tip-off Control Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop and test key technologies needed for an integrated, high thrust colloid thruster system with no moving parts, for spacecraft attitude control...

  20. Position and attitude tracking control for a quadrotor UAV.

    Science.gov (United States)

    Xiong, Jing-Jing; Zheng, En-Hui

    2014-05-01

    A synthesis control method is proposed to perform the position and attitude tracking control of the dynamical model of a small quadrotor unmanned aerial vehicle (UAV), where the dynamical model is underactuated, highly-coupled and nonlinear. Firstly, the dynamical model is divided into a fully actuated subsystem and an underactuated subsystem. Secondly, a controller of the fully actuated subsystem is designed through a novel robust terminal sliding mode control (TSMC) algorithm, which is utilized to guarantee all state variables converge to their desired values in short time, the convergence time is so small that the state variables are acted as time invariants in the underactuated subsystem, and, a controller of the underactuated subsystem is designed via sliding mode control (SMC), in addition, the stabilities of the subsystems are demonstrated by Lyapunov theory, respectively. Lastly, in order to demonstrate the robustness of the proposed control method, the aerodynamic forces and moments and air drag taken as external disturbances are taken into account, the obtained simulation results show that the synthesis control method has good performance in terms of position and attitude tracking when faced with external disturbances. PMID:24534327

  1. Local controllability and stabilization of spacecraft attitude by two single-gimbal control moment gyros

    Institute of Scientific and Technical Information of China (English)

    Gui Haichao; Jin Lei; Xu Shijie

    2013-01-01

    The attitude control problem of a spacecraft underactuated by two single-gimbal control moment gyros (SGCMGs) is investigated. Small-time local controllability (STLC) of the attitude dynamics of the spacecraft-SGCMGs system is analyzed via nonlinear controllability theory. The conditions that guarantee STLC of the spacecraft attitude by two non-coaxial SGCMGs are obtained with the momentum of the SGCMGs as inputs, implying that the spacecraft attitude is STLC when the total angular momentum of the whole system is zero. Moreover, our results indi-cate that under the zero-momentum restriction, full attitude stabilization is possible for a spacecraft using two non-coaxial SGCMGs. For the case of two coaxial SGCMGs, the STLC property of the spacecraft cannot be determined. In this case, an improvement to the previous full attitude stabiliz-ing control law, which requires zero-momentum presumption, is proposed to account for the singu-larity of SGCMGs and enhance the steady state performance. Numerical simulation results demonstrate the effectiveness and advantages of the new control law.

  2. Backstepping-Based Inverse Optimal Attitude Control of Quadrotor

    Directory of Open Access Journals (Sweden)

    An Honglei

    2013-05-01

    Full Text Available Input saturation must be taken into account for applying rapid reorientation in the large angle manoeuvre of a quadrotor. In this paper, a backstepping‐based inverse optimal attitude controller (BIOAC is derived which has the property of a maximum convergence rate in the sense of a control Lyapunov function (CLF under input torque limitation. In the controller, a backstepping technique is used for handling the complexity introducing by the unit quaternion representation of the attitude of a quadrotor with four parameters. Moreover, the inverse optimal approach is employed to circumvent the difficulty of solving the Hamilton‐Jacobi‐Bellman (HJB equation. The performance of BIOAC is compared with a PD controller in which the input torque limitation is not considered under the same unit quaternion representation using numerical simulation while the results show that BIOAC gains faster convergence with less control effort. Next, BIOAC is realized on a test bed and the effectiveness of the control law is verified by experimental studies.

  3. Satellite Attitude Control System Design considering the Fuel Slosh Dynamics

    Directory of Open Access Journals (Sweden)

    Luiz Carlos Gadelha de Souza

    2014-01-01

    Full Text Available The design of the satellite attitude control system (ACS becomes more complex when the satellite structure has different type of components like, flexible solar panels, antennas, mechanical manipulators, and tanks with fuel. A crucial interaction can occur between the fuel slosh motion and the satellite rigid motion during translational and/or rotational manoeuvre since these interactions can change the satellite centre of mass position damaging the ACS pointing accuracy. Although, a well-designed controller can suppress such disturbances quickly, the controller error pointing may be limited by the minimum time necessary to suppress such disturbances thus affecting the satellite attitude acquisition. As a result, the design of the satellite controller needs to explore the limits between the conflicting requirements of performance and robustness. This paper investigates the effects of the interaction between the liquid motion (slosh and the satellite dynamics in order to predict what the damage to the controller performance and robustness is. The fuel slosh dynamics is modelled by a pendulum which parameters are identified using the Kalman filter technique. This information is used to design the satellite controller by the linear quadratic regulator (LQR and linear quadratic Gaussian (LQG methods to perform a planar manoeuvre assuming thrusters are actuators.

  4. Observer Based Sliding Mode Attitude Control: Theoretical and Experimental Results

    Directory of Open Access Journals (Sweden)

    U. Jørgensen

    2011-07-01

    Full Text Available In this paper we present the design of a sliding mode controller for attitude control of spacecraft actuated by three orthogonal reaction wheels. The equilibrium of the closed loop system is proved to be asymptotically stable in the sense of Lyapunov. Due to cases where spacecraft do not have angular velocity measurements, an estimator for the generalized velocity is derived and asymptotic stability is proven for the observer. The approach is tested on an experimental platform with a sphere shaped Autonomous Underwater Vehicle SATellite: AUVSAT, developed at the Norwegian University of Science and Technology.

  5. Multimode attitude and orbit control for the Atmosphere Explorer spacecraft

    Science.gov (United States)

    Stewart, B.

    1975-01-01

    The orbit profile for the Atmosphere Explorer requires a velocity adjust capability of 2000 ft/sec/sec and individual maneuvers of up to 24 ft/sec in magnitude. This requirement is met by a monopropellant hydrazine propulsion subsystem which also provides, by virtue of the tank arrangement, a means of adjusting the spacecraft center of mass in orbit, thereby minimizing external disturbance torques. The attitude control subsystem is of the momentum bias type. A large internal flywheel furnishes gyroscopic stiffness and permits rapid changes in operating mode (despun to spinning mode) by controlled interchange of momentum between the flywheel and the spacecraft main body.

  6. Design of Attitude Control System for UAV Based on Feedback Linearization and Adaptive Control

    Directory of Open Access Journals (Sweden)

    Wenya Zhou

    2014-01-01

    Full Text Available Attitude dynamic model of unmanned aerial vehicles (UAVs is multi-input multioutput (MIMO, strong coupling, and nonlinear. Model uncertainties and external gust disturbances should be considered during designing the attitude control system for UAVs. In this paper, feedback linearization and model reference adaptive control (MRAC are integrated to design the attitude control system for a fixed wing UAV. First of all, the complicated attitude dynamic model is decoupled into three single-input single-output (SISO channels by input-output feedback linearization. Secondly, the reference models are determined, respectively, according to the performance indexes of each channel. Subsequently, the adaptive control law is obtained using MRAC theory. In order to demonstrate the performance of attitude control system, the adaptive control law and the proportional-integral-derivative (PID control law are, respectively, used in the coupling nonlinear simulation model. Simulation results indicate that the system performance indexes including maximum overshoot, settling time (2% error range, and rise time obtained by MRAC are better than those by PID. Moreover, MRAC system has stronger robustness with respect to the model uncertainties and gust disturbance.

  7. Cosmic Background Explorer (COBE) transfer orbit attitude control system

    Science.gov (United States)

    Placanica, Samuel J.; Flatley, Thomas W.

    1986-01-01

    The Cosmic Background Explorer (COBE) spacecraft will be launched by the Shuttle from Vandenberg AFB into a 300 km altitude, 99 deg inclination, 6 a.m. or 6 p.m. ascending node orbit. After release from the Remote Manipulator System (RMS) arm, an on-board monopropellant hydrazine propulsion system will raise the orbit altitude to 900 km. The spacecraft continuously spins during transfer orbit operations with the spin axis nominally horizontal and in or near the orbit plane. The blowdown propulsion system consists of twelve 5 lb thrusters (3 'spin', 3 'despin', and 6 'axial') with the latter providing initially 30 lb of force parallel to the spin axis for orbit raising. The spin/despin jets provide a constant roll rate during the transfer orbit phase of the mission and the axials control pitch and yaw. The axial thrusters are pulsed on for attitude control during coast periods and are normally on- and off-modulated for control during orbit raising. Attitude sensors employed in the control loops include an array of two-axis digital sun sensors and three planar earth scanners for position measurements, as well as six gyroscopes for rate information. System redundancy is achieved by means of unique three-axes-in-a-plane geometry. This triaxial concept results in a fail-safe operational system with no performance degradation for many different component failure modes.

  8. AttSim, Attitude Simulation with Control Software in the Loop

    OpenAIRE

    Koenigsmann, Hans; Gurevich, Gwynne

    1999-01-01

    AttSim is a spacecraft attitude simulator that has been specifically developed to design and verify attitude control concepts and flight software architectures and algorithms. Its primary goal is to provide a generic approach to small satellite attitude control development by allowing scalable performance. AttSim specifically allows the user to develop software modules that can be used as flight code, and to verify control logic, controller gains, and other mission-critical elements. The code...

  9. Implicit and Explicit Attitudes and Interracial Interaction: The Moderating Role of Situationally Available Control Resources

    OpenAIRE

    Hofmann, Wilhelm; Gschwendner, Tobias; Castelli, Luigi; Schmitt, Manfred

    2008-01-01

    Abstract The present research examined whether implicit and explicit racial attitudes predict interracial interaction behavior differently as a function of situationally available control resources. Specifically, we investigated how implicit attitudes (Implicit Association Test) and explicit attitudes (Blatant/Subtle prejudice) were related to interracial interaction behaviors of Italians toward an African ...

  10. Controlled comparison of attitudes of psychiatrists, general practitioners, homosexual doctors and homosexual men to male homosexuality.

    OpenAIRE

    Bhugra, D.; King, M

    1989-01-01

    A controlled analysis of the attitudes of doctors and homosexual men to male homosexuality is reported. Not surprisingly the homosexual men held the most liberal attitudes which served as a yard-stick against which the doctors' attitudes could be assessed. The implications of these data, collected before the AIDS era, are discussed in terms of the current needs of homosexual patients.

  11. Magnetic Attitude Control System for Spinning Small Spacecraft

    OpenAIRE

    Pal, Parimal; Selby, Vaughn

    1990-01-01

    A magnetic Attitude Control Subsystem (ACS) designed for minimum power weight, and cost is presented. The ACS subsystem was designed and built by ITHACO for the Small Communications Satellite Cluster (SCSC), integrated by Defense Systems Incorporated for the Defense Advanced Research Projects Agency. The basic spacecraft configuration is a flat cylinder, having a mass of 22.7 Kg with a diameter of 47.2 cm and 17.0 cm height. Hardware for the ACS design includes a two-axis magnetometer, two TO...

  12. The TUBSAT-1 Attitude Control and Stabilization System

    OpenAIRE

    Ginati, Amnon

    1989-01-01

    TUBSAT-1 (Technical University Berlin Satellite) is an experimental low-cost satellite being financed by the German BMFT. The dimensions and weight are determined by the NASA Gas-Program and it will be ejected from the Space Shuttle within the German spacelab mission D2 by December 19, 1991, into a 298 km circular orbit and at a 28.5° inclination. To enable a large variety of useful experiments to fly with TUSSAT, it was necessary to develop a rather precise attitude control and stabilization...

  13. Coordinated Multiple Spacecraft Attitude Control with Communication Time Delays and Uncertainties

    Institute of Scientific and Technical Information of China (English)

    LI Guiming; LIU Liangdong

    2012-01-01

    In this paper,we consider the coordinated attitude control problem of spacecraft formation with communication delays,model and disturbance uncertainties,and propose novel synchronized control schemes.Since the attitude motion is essential in non-Euclidean space,thus,unlike the existing designs which describe the delayed relative attitude via linear algorithm,we treat the attitude error and the local relative attitude on the nonlinear manifold-Lie group,and attempt to obtain coupling attitude information by the natural quatemion multiplication.Our main focus is to address two problems:1) Propose a coordinated attitude controller to achieve the synchronized attitude maneuver,i.e.,synchronize multiple spacecraft attitudes and track a time-varying desired attitude; 2) With known model information,we achieve the synchronized attitude maneuver with disturbances under angular velocity constraints.Especially,if the formation does not have any uncertainties,the designer can simply set the controller via an appropriate choice of control gains to avoid system actuator saturation.Our controllers are proposed based on the Lyapunov-Krasovskii method and simulation of a spacecraft formation is conducted to demonstrate the effectiveness of theoretical results.

  14. Fault Reconstruction Approach for Distributed Coordinated Spacecraft Attitude Control System

    Directory of Open Access Journals (Sweden)

    Mingyi Huo

    2015-01-01

    Full Text Available This work presents a novel fault reconstruction approach for a large-scale system, that is, a distributed coordinated spacecraft attitude control system. The attitude of all the spacecrafts in this distributed system is controlled by using thrusters. All possible faults of thruster including thrust magnitude error and alignment error are investigated. As a stepping stone, the mathematical model of thruster is firstly established based on the thruster configuration. On the basis of this, a sliding mode observer is then proposed to reconstruct faults in each agent of the coordinated control system. A Lyapunov-based analysis shows that the observer asymptotically converges to the actual faults. The key feature of this fault reconstruction approach is that it can achieve a faster reconstruction of the fault in comparison with the conventional fault reconstruction schemes. It can globally reconstruct thruster faults with zero reconstruction error, and this is accomplished within finite time. The effectiveness of the proposed approach is analytically authenticated via simulation study.

  15. Estimating Friction Parameters in Reaction Wheels for Attitude Control

    Directory of Open Access Journals (Sweden)

    Valdemir Carrara

    2013-01-01

    Full Text Available The ever-increasing use of artificial satellites in both the study of terrestrial and space phenomena demands a search for increasingly accurate and reliable pointing systems. It is common nowadays to employ reaction wheels for attitude control that provide wide range of torque magnitude, high reliability, and little power consumption. However, the bearing friction causes the response of wheel to be nonlinear, which may compromise the stability and precision of the control system as a whole. This work presents a characterization of a typical reaction wheel of 0.65 Nms maximum angular momentum storage, in order to estimate their friction parameters. It used a friction model that takes into account the Coulomb friction, viscous friction, and static friction, according to the Stribeck formulation. The parameters were estimated by means of a nonlinear batch least squares procedure, from data raised experimentally. The results have shown wide agreement with the experimental data and were also close to a deterministic model, previously obtained for this wheel. This model was then employed in a Dynamic Model Compensator (DMC control, which successfully reduced the attitude steady state error of an instrumented one-axis air-bearing table.

  16. An Attitude Control of Flexible Spacecraft Using Fuzzy-PID Controller

    Science.gov (United States)

    Park, Jong-Oh; Im, Young-Do

    This primary objective of this study is to demonstrate simulation and ground-based experiment for the attitude control of flexible spacecraft. A typical spacecraft structure consists of the rigid body and flexible appendages which are large flexible solar panels, parabolic antennas built from light materials in order to reduce their weight. Therefore the attitude control has a big problem because these appendages induce structural vibration under the excitation of external forces. A single-axis rotational simulator with a flexible arm is constructed with on-off air thrusters and reaction wheel as actuation. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The experiment of flexible spacecraft attitude control is performed using only the reaction wheel. Using the reaction wheel the performance of the fuzzy-PID controller is illustrated by simulation and experimental results for a single-axis rotational simulator.

  17. Framework of Combined Adaptive and Non-adaptive Attitude Control System for a Helicopter Experimental System

    Institute of Scientific and Technical Information of China (English)

    Akira Inoue; Ming-Cong Deng

    2006-01-01

    This paper presents a framework of a combined adaptive and non-adaptive attitude control system for a helicopter experimental system. The design method is based on a combination of adaptive nonlinear control and non-adaptive nonlinear control. With regard to detailed attitude control system design, two schemes are shown for different application cases.

  18. Periodic H-2 Synthesis for Spacecraft Attitude Control with Magnetometers

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Stoustrup, Jakob

    2004-01-01

    A control synthesis for a spacecraft equipped with a set of magnetorquer coils is addressed. The electromagnetic actuation is particularly attractive for small low-cost spacecraft missions, due to their relatively low price, high reliability, light weight, and low power consumption. The interacti....... A linear matrix inequality-based algorithm is proposed for attitude control synthesis. Simulation results are provided, showing the prospect of the concept for onboard implementation.......A control synthesis for a spacecraft equipped with a set of magnetorquer coils is addressed. The electromagnetic actuation is particularly attractive for small low-cost spacecraft missions, due to their relatively low price, high reliability, light weight, and low power consumption. The interaction...

  19. Backup Attitude Control Algorithms for the MAP Spacecraft

    Science.gov (United States)

    ODonnell, James R., Jr.; Andrews, Stephen F.; Ericsson-Jackson, Aprille J.; Flatley, Thomas W.; Ward, David K.; Bay, P. Michael

    1999-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The MAP spacecraft will perform its mission, studying the early origins of the universe, in a Lissajous orbit around the Earth-Sun L(sub 2) Lagrange point. Due to limited mass, power, and financial resources, a traditional reliability concept involving fully redundant components was not feasible. This paper will discuss the redundancy philosophy used on MAP, describe the hardware redundancy selected (and why), and present backup modes and algorithms that were designed in lieu of additional attitude control hardware redundancy to improve the odds of mission success. Three of these modes have been implemented in the spacecraft flight software. The first onboard mode allows the MAP Kalman filter to be used with digital sun sensor (DSS) derived rates, in case of the failure of one of MAP's two two-axis inertial reference units. Similarly, the second onboard mode allows a star tracker only mode, using attitude and derived rate from one or both of MAP's star trackers for onboard attitude determination and control. The last backup mode onboard allows a sun-line angle offset to be commanded that will allow solar radiation pressure to be used for momentum management and orbit stationkeeping. In addition to the backup modes implemented on the spacecraft, two backup algorithms have been developed in the event of less likely contingencies. One of these is an algorithm for implementing an alternative scan pattern to MAP's nominal dual-spin science mode using only one or two reaction wheels and thrusters. Finally, an algorithm has been developed that uses thruster one shots while in science mode for momentum management. This algorithm has been developed in case system momentum builds up faster than anticipated, to allow adequate momentum management while minimizing interruptions to science. In this paper, each mode and

  20. Pushing the Limits of Cubesat Attitude Control: A Ground Demonstration

    Science.gov (United States)

    Sanders, Devon S.; Heater, Daniel L.; Peeples, Steven R.; Sules. James K.; Huang, Po-Hao Adam

    2013-01-01

    A cubesat attitude control system (ACS) was designed at the NASA Marshall Space Flight Center (MSFC) to provide sub-degree pointing capabilities using low cost, COTS attitude sensors, COTS miniature reaction wheels, and a developmental micro-propulsion system. The ACS sensors and actuators were integrated onto a 3D-printed plastic 3U cubesat breadboard (10 cm x 10 cm x 30 cm) with a custom designed instrument board and typical cubesat COTS hardware for the electrical, power, and data handling and processing systems. In addition to the cubesat development, a low-cost air bearing was designed and 3D printed in order to float the cubesat in the test environment. Systems integration and verification were performed at the MSFC Small Projects Rapid Integration & Test Environment laboratory. Using a combination of both the miniature reaction wheels and the micro-propulsion system, the open and closed loop control capabilities of the ACS were tested in the Flight Robotics Laboratory. The testing demonstrated the desired sub-degree pointing capability of the ACS and also revealed the challenges of creating a relevant environment for development testin

  1. Spacecraft attitude control using neuro-fuzzy approximation of the optimal controllers

    Science.gov (United States)

    Kim, Sung-Woo; Park, Sang-Young; Park, Chandeok

    2016-01-01

    In this study, a neuro-fuzzy controller (NFC) was developed for spacecraft attitude control to mitigate large computational load of the state-dependent Riccati equation (SDRE) controller. The NFC was developed by training a neuro-fuzzy network to approximate the SDRE controller. The stability of the NFC was numerically verified using a Lyapunov-based method, and the performance of the controller was analyzed in terms of approximation ability, steady-state error, cost, and execution time. The simulations and test results indicate that the developed NFC efficiently approximates the SDRE controller, with asymptotic stability in a bounded region of angular velocity encompassing the operational range of rapid-attitude maneuvers. In addition, it was shown that an approximated optimal feedback controller can be designed successfully through neuro-fuzzy approximation of the optimal open-loop controller.

  2. Attitude control system of the Delfi-n3Xt satellite

    OpenAIRE

    Reijneveld, J.; Choukroun, D.

    2013-01-01

    This work is concerned with the development of the attitude control algorithms that will be implemented on board of the Delfi-n3xt nanosatellite, which is to be launched in 2013. One of the mission objectives is to demonstrate Sun pointing and three axis stabilization. The attitude control modes and the associated algorithms are described. The control authority is shared between three body-mounted magnetorquers (MTQ) and three orthogonal reaction wheels. The attitude information is retrieved ...

  3. Design of the Active Attitude Determination and Control System for the e-st@r cubesat

    OpenAIRE

    Stesina, Fabrizio; Corpino, Sabrina; Mozzillo, Raffaele; Obiols Rabasa, Gerard

    2012-01-01

    One of the most limiting factors which affects pico/nano satellites capabilities is the poor accuracy in attitude control. To improve mission performances of this class of satellites, the capability of controlling satellite's attitude shall be enhanced. The paper presents the design, development and verification of the Active Attitude Determination and Control System (A-ADCS) of the E-ST@R Cubesat developed at Politecnico di Torino. The heart of the system is an ARM9 microcontroller that mana...

  4. Reaction Wheel Installation Deviation Compensation for Overactuated Spacecraft with Finite-Time Attitude Control

    OpenAIRE

    2013-01-01

    A novel attitude tracking control scheme is presented for overactuated spacecraft to address the attitude stabilization problem in presence of reaction wheel installation deviation, external disturbance and uncertain mass of moment inertia. An adaptive sliding mode control technique is proposed to track the uncertainty. A Lyapunov-based analysis shows that the compensation control law can guarantee that the desired attitude trajectories are followed in finite-time. The key feature of the prop...

  5. A comparing design of satellite attitude control system based on reaction wheel

    Institute of Scientific and Technical Information of China (English)

    CHENG Hao; GE Sheng-min; SHEN Yi

    2008-01-01

    The disturbance caused by the reaction wheel with a current controller greatly influences the accuracy and stability of the satellite attitude control system.To solve this problem,the idea of speed feedback compensation control reaction wheel is put forward.This paper introduces the comparison on design and performance of two satellite attitude control systems,which are separately based on the current control reaction wheel and the speed feedback compensation control reaction wheel.Analysis shows that the speed feedback compensation control flywheel system may effectively suppress the torque fluctuation.Simulation results indicate that the satellite attitude control system with the speed feedback compensation control flywheel has improved performance.

  6. Gaining control over responses to implicit attitude tests: Implementation intentions engender fast responses on attitude-incongruent trials.

    Science.gov (United States)

    Webb, Thomas L; Sheeran, Paschal; Pepper, John

    2012-03-01

    The present research investigated whether forming implementation intentions could promote fast responses to attitude-incongruent associations (e.g., woman-manager) and thereby modify scores on popular implicit measures of attitude. Expt 1 used the Implicit Association Test (IAT) to measure associations between gender and science versus liberal arts. Planning to associate women with science engendered fast responses to this category-attribute pairing and rendered summary scores more neutral compared to standard IAT instructions. Expt 2 demonstrated that forming egalitarian goal intentions is not sufficient to produce these effects. Expt 3 extended these findings to a different measure of implicit attitude (the Go/No-Go Association Task) and a different stereotypical association (Muslims-terrorism). In Expt 4, managers who planned to associate women with superordinate positions showed more neutral IAT scores relative to non-planners and effects were maintained 3 weeks later. In sum, implementation intentions enable people to gain control over implicit attitude responses. PMID:22435844

  7. Robust attitude control design for spacecraft under assigned velocity and control constraints.

    Science.gov (United States)

    Hu, Qinglei; Li, Bo; Zhang, Youmin

    2013-07-01

    A novel robust nonlinear control design under the constraints of assigned velocity and actuator torque is investigated for attitude stabilization of a rigid spacecraft. More specifically, a nonlinear feedback control is firstly developed by explicitly taking into account the constraints on individual angular velocity components as well as external disturbances. Considering further the actuator misalignments and magnitude deviation, a modified robust least-squares based control allocator is employed to deal with the problem of distributing the previously designed three-axis moments over the available actuators, in which the focus of this control allocation is to find the optimal control vector of actuators by minimizing the worst-case residual error using programming algorithms. The attitude control performance using the controller structure is evaluated through a numerical example. PMID:23618744

  8. Motor Control of Two Flywheels Enabling Combined Attitude Control and Bus Regulation

    Science.gov (United States)

    Kenny, Barbara H.

    2004-01-01

    This presentation discussed the flywheel technology development work that is ongoing at NASA GRC with a particular emphasis on the flywheel system control. The "field orientation" motor/generator control algorithm was discussed and explained. The position-sensorless angle and speed estimation algorithm was presented. The motor current response to a step change in command at low (10 kRPM) and high (60 kRPM) was discussed. The flywheel DC bus regulation control was explained and experimental results presented. Finally, the combined attitude control and energy storage algorithm that controls two flywheels simultaneously was presented. Experimental results were shown that verified the operational capability of the algorithm. shows high speed flywheel energy storage (60,000 RPM) and the successful implementation of an algorithm to simultaneously control both energy storage and a single axis of attitude with two flywheels. Overall, the presentation demonstrated that GRC has an operational facility that

  9. Deploying process modeling and attitude control of a satellite with a large deployable antenna

    OpenAIRE

    Zhigang Xing; Gangtie Zheng

    2014-01-01

    Modeling and attitude control methods for a satellite with a large deployable antenna are studied in the present paper. Firstly, for reducing the model dimension, three dynamic models for the deploying process are developed, which are built with the methods of multi-rigid-body dynamics, hybrid coordinate and substructure. Then an attitude control method suitable for the deploying process is proposed, which can keep stability under any dynamical parameter variation. Subsequently, this attitude...

  10. Attitude Control on TET-1 - Experiences from the First Year of Operations

    OpenAIRE

    Hobsch, Markus; Cossavella, Fabiana; Löw, Sebastian; Herman, Jacobus

    2014-01-01

    The micro-satellite TET-1 carries several technology experiments. It is the first in a series offering the possibility of in-orbit verification of new equipment made in Germany by the industrial and scientific aerospace community. TET-1 was launched 22nd July 2012 and is operated by the German Space Operations Center. Attitude and attitude control is influenced by several of the experiments. Special attitude control modes are required for a number of experiments in order to point the sate...

  11. Attitude control system of the Delfi-n3Xt satellite

    NARCIS (Netherlands)

    Reijneveld, J.; Choukroun, D.

    2013-01-01

    This work is concerned with the development of the attitude control algorithms that will be implemented on board of the Delfi-n3xt nanosatellite, which is to be launched in 2013. One of the mission objectives is to demonstrate Sun pointing and three axis stabilization. The attitude control modes and

  12. Magnetic Attitude Control System for Low-Earth Orbit Satellites

    International Nuclear Information System (INIS)

    A small spacecraft (SC) under consideration is intended for performing a scientific mission on the low-Earth orbit for a long time (a year or more). A control system of the SC provides the construction of regime of three-axis orientation of the SC in the orbital coordinate system and the stabilization of that regime, and must be autonomous, low-weight and low-cost. The magnetic control system that consists of the information subsystem based solely on three-axis magnetometer measuring and the magnetic actuators satisfies in the best way requirements mentioned above. Such system can estimate both orbital motion parameters and attitude ones of the SC. But the absence of the additional instruments and damping devices complicates the estimation since the range of initial conditions uncertainly is wide and the problem of estimating becomes essentially nonlinear. To get over these difficulties a recursive state estimation algorithm with enhanced convergence is proposed. The magnetic control moment is synthesized byte vector function Lyapunov method

  13. Orion Launch Abort Vehicle Attitude Control Motor Testing

    Science.gov (United States)

    Murphy, Kelly J.; Brauckmann, Gregory J.; Paschal, Keith B.; Chan, David T.; Walker, Eric L.; Foley, Robert; Mayfield, David; Cross, Jared

    2011-01-01

    Current Orion Launch Abort Vehicle (LAV) configurations use an eight-jet, solid-fueled Attitude Control Motor (ACM) to provide required vehicle control for all proposed abort trajectories. Due to the forward position of the ACM on the LAV, it is necessary to assess the effects of jet-interactions (JI) between the various ACM nozzle plumes and the external flow along the outside surfaces of the vehicle. These JI-induced changes in flight control characteristics must be accounted for in developing ACM operations and LAV flight characteristics. A test program to generate jet interaction aerodynamic increment data for multiple LAV configurations was conducted in the NASA Ames and NASA Langley Unitary Plan Wind Tunnels from August 2007 through December 2009. Using cold air as the simulant gas, powered subscale models were used to generate interaction data at subsonic, transonic, and supersonic test conditions. This paper presents an overview of the complete ACM JI experimental test program for Orion LAV configurations, highlighting ACM system modeling, nozzle scaling assumptions, experimental test techniques, and data reduction methodologies. Lessons learned are discussed, and sample jet interaction data are shown. These data, in conjunction with computational predictions, were used to create the ACM JI increments for all relevant flight databases.

  14. Control synthesis for polynomial nonlinear systems and application in attitude control

    Institute of Scientific and Technical Information of China (English)

    Chang-fei TONG; Hui ZHANG; You-xian SUN

    2008-01-01

    A method for positive polynomial validation based on polynomial decomposition is proposed to deal with control synthesis problems. Detailed algorithms for decomposition are given which mainly consider how to convert coefficients of a polynomial to a matrix with free variables. Then, the positivity of a polynomial is checked by the decomposed matrix with semidefinite programming solvers. A nonlinear control law is presented for single input polynomial systems based on the Lyapunov stability theorem. The control synthesis method is advanced to multi-input systems further. An application in attitude control is finally presented. The proposed control law achieves effective performance as illustrated by the numerical example.

  15. Fixed-Star Tracking Attitude Control of Spacecraft Using Single-Gimbal Control Moment Gyros

    OpenAIRE

    Sangwon Kwon; Yuki Tani; Hiroshi Okubo; Takashi Shimomura

    2010-01-01

    Problem statement: A cluster of small-sized Single-Gimbal Control Moment Gyros (SGCMGs) is proposed as an attitude control actuator for high-speed maneuver of small satellites. There exists a singularity problem what is peculiar to the CMG system. Approach: This study presented a simple singularity avoidance steering law using the Singular Value Decomposition (SVD) algorithm. Results: Capability of the present steering method in singularity avoidance was demonstrated with numerical simulation...

  16. Spacecraft methods and structures with enhanced attitude control that facilitates gyroscope substitutions

    Science.gov (United States)

    Li, Rongsheng (Inventor); Kurland, Jeffrey A. (Inventor); Dawson, Alec M. (Inventor); Wu, Yeong-Wei A. (Inventor); Uetrecht, David S. (Inventor)

    2004-01-01

    Methods and structures are provided that enhance attitude control during gyroscope substitutions by insuring that a spacecraft's attitude control system does not drive its absolute-attitude sensors out of their capture ranges. In a method embodiment, an operational process-noise covariance Q of a Kalman filter is temporarily replaced with a substantially greater interim process-noise covariance Q. This replacement increases the weight given to the most recent attitude measurements and hastens the reduction of attitude errors and gyroscope bias errors. The error effect of the substituted gyroscopes is reduced and the absolute-attitude sensors are not driven out of their capture range. In another method embodiment, this replacement is preceded by the temporary replacement of an operational measurement-noise variance R with a substantially larger interim measurement-noise variance R to reduce transients during the gyroscope substitutions.

  17. Finite-time output feedback attitude coordination control for formation flying spacecraft without unwinding

    Science.gov (United States)

    Guo, Yong; Song, Shen-Min; Li, Xue-Hui

    2016-05-01

    In this paper, two finite-time attitude coordinated controllers for formation flying spacecraft are investigated based on rotation matrix. Because rotation matrix can represent the set of attitudes both globally and uniquely, the two controllers can deal with unwinding that can result in extra fuel consumption. To address the lack of angular velocity measurement, the second attitude coordinated controller is given by using a novel filter. Through homogeneous method and Lyapunov theories, it is shown that the proposed controllers can achieve the finite-time stability. Numerical simulations also demonstrate that the proposed control schemes are effective.

  18. General Attitude Control Algorithm for Spacecraft Equipped with Star Camera and Reaction Wheels

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    realized on an integrated circuit. This paper considers two issues: slew maneuver with a feature of avoiding direct exposure of the camera's CCD chip to the Sun %, three-axis attitude control and optimal control torque distribution in a reaction wheel assembly. The attitude controller is synthesized...... applying the energy shaping technique, where the desired potential function is carefully designed using a physical insight into the nature of the problem. The system stability is thoroughly analyzed and the control performance simulated...

  19. New one-axis one-sensor magnetic attitude control theoretical and in-flight performance

    Science.gov (United States)

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Tkachev, S. S.; Karpenko, S. O.

    2014-12-01

    New one-axis magnetic attitude control is proposed. Only one attitude sensor providing any inertial direction measurements is necessary, magnetometer is not used. The control may be used as a backup capability in case main actuators or some attitude sensors fail. Sun pointing is achievable using only three-axis Sun sensor, so the control may be used to lower the power consumption during battery charging. Asymptotic stability of different equilibria depending on the satellite inertia tensor is summarized. In-flight results from "Chibis-M" microsatellite are provided proving general control performance.

  20. The Relationship between Religious Attitudes, Locus of Control and Tendency to Substace Abuse in University Students

    Directory of Open Access Journals (Sweden)

    Farhad Asghari

    2013-05-01

    Full Text Available Aim: The purpose of this study was the study of relationship between religious attitudes, locus of control and tendency to substance abuse among students of Guilan University. Method: The research design was correlational design. For this purpose, 340 university students of Guilan University selected through Morgan table by cluster randome sampling. Allport religious orientation, Ratter locus of control and addiction potential scale administered among selected sample. Results: The results showed significant relationship between religious attitude, locus of control and tendency to substance abuse. That is religious attitude, locus of control entered in regression model as significant predictors. Also there was significant relationship between religious attitude, and locus of control. Altogheder, results showed that people with internal religious attitude have internal locus of control and lower tendency to substance abuse. Also, people with external religious attitude have external locus of control and higher tendency to substance abuse. Conclusion: According to the results, we can conclude that religious attitude and locus of control play important role on tendency to substance abuse.

  1. Attitude Stabilization Control of a Quadrotor UAV by Using Backstepping Approach

    Directory of Open Access Journals (Sweden)

    Xing Huo

    2014-01-01

    Full Text Available The modeling and attitude stabilization control problems of a four-rotor vertical takeoff and landing unmanned air vehicle (UAV known as the quadrotor are investigated. The quadrotor’s attitude is represented by the unit quaternion rather than Euler angles to avoid singularity problem. Taking dynamical behavior of motors into consideration and ignoring aerodynamic effect, a nonlinear controller is developed to stabilize the attitude. The control design is accomplished by using backstepping control technique. The proposed control law is based on the compensation for the Coriolis and gyroscope torques. Applying Lyapunov stability analysis proves that the closed-loop attitude system is asymptotic stable. Moreover, the controller can guarantee that all the states of the system are uniformly ultimately bounded in the presence of external disturbance torque. The effectiveness of the proposed control approach is analytically authenticated and also validated via simulation study.

  2. Decentralized sliding-mode control for spacecraft attitude synchronization under actuator failures

    Science.gov (United States)

    Wu, Baolin; Wang, Danwei; Poh, Eng Kee

    2014-12-01

    This paper examines attitude synchronization and tracking problems with model uncertainties, external disturbances, actuator failures and control torque saturation. Two decentralized sliding mode control laws are proposed and analyzed based on algebraic graph theory. Using Barbalat's Lemma, it is shown that the control laws guarantee each spacecraft approaches the desired time-varying attitude and angular velocity while maintaining attitude synchronization among the other spacecraft in the formation. The first controller is designed in the presence of model uncertainties, external disturbances, and actuator failures. The results are extended to the case with control input saturation in the second controller. Both control laws do not require online identification of failures. Numerical simulations are presented to show the effectiveness of the proposed attitude synchronization and tracking approaches.

  3. Propellantless Attitude Control of Solar Sail Technology Utilizing Reflective Control Devices

    Science.gov (United States)

    Munday, Jeremy

    2016-01-01

    Solar sails offer an opportunity for a CubeSatscale, propellant-free spacecraft technology that enables long-term and long-distance missions not possible with traditional methods. Solar sails operate using the transfer of linear momentum from photons of sunlight reflected from the surface of the sail. To propel the spacecraft, no mechanically moving parts, thrusters, or propellant are needed. However, attitude control, or orientation, is still performed using traditional methods involving reaction wheels and propellant ejection, which severely limit mission lifetime. For example, the current state of the art solutions employed by upcoming missions couple solar sails with a state of the art propellant ejection gas system. Here, the use of the gas thruster has limited the lifetime of the mission. To solve the limited mission lifetime problem, the Propellantless Attitude Control of Solar Sail Technology Utilizing Reflective Control Devices project team is working on propellantless attitude control using thin layers of material, an optical film, electrically switchable from transparent to reflective. The technology is based on a polymer-dispersed liquid crystal (PDLC), which allows this switch upon application of a voltage. This technology removes the need for propellant, which reduces weight and cost while improving performance and lifetime.

  4. Algorithm of Attitude Control and Its Simulation of Free-Flying Space Robot

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Reaction wheel or reaction thruster is employed to maintain the attitude of the base of space robot fixed in attitude control of free-flying space robot.However, in this method, a large amount of fuel will be consumed, and it will shorten the on-orbit life span of space robot, it also vibrate the system and make the system unsteady.The restricted minimum disturbance map (RMDM) based algorithm of attitude control is presented to keep the attitude of the base fixed during the movement of the manipulator.In this method it is realized by planning motion trajectory of the end-effector of manipulator without using reaction wheel or reaction thruster.In order to verify the feasibility and effectiveness of the algorithm attitude control presented in this paper, computer simulation experiments have been made and the experimental results demonstrate that this algorithm is feasible.

  5. Attitude dynamics and control of spacecraft using geomagnetic Lorentz force

    International Nuclear Information System (INIS)

    Attitude stabilization of a charged rigid spacecraft in Low Earth Orbit using torques due to Lorentz force in pitch and roll directions is considered. A spacecraft that generates an electrostatic charge on its surface in the Earth's magnetic field will be subject to perturbations from the Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft's orientation. We assume that the spacecraft is moving in the Earth's magnetic field in an elliptical orbit under the effects of gravitational, geomagnetic and Lorentz torques. The magnetic field of the Earth is modeled as a non-tilted dipole. A model incorporating all Lorentz torques as a function of orbital elements has been developed on the basis of electric and magnetic fields. The stability of the spacecraft orientation is investigated both analytically and numerically. The existence and stability of equilibrium positions is investigated for different values of the charge to mass ratio (α*). Stable orbits are identified for various values of α*. The main parameters for stabilization of the spacecraft are α* and the difference between the components of the moment of inertia for the spacecraft. (research papers)

  6. Nonlinear Attitude Control of Planar Structures in Space Using Only Internal Controls

    Science.gov (United States)

    Reyhanoglu, Mahmut; Mcclamroch, N. Harris

    1993-01-01

    An attitude control strategy for maneuvers of an interconnection of planar bodies in space is developed. It is assumed that there are no exogeneous torques and that torques generated by joint motors are used as means of control so that the total angular momentum of the multibody system is a constant, assumed to be zero. The control strategy utilizes the nonintegrability of the expression for the angular momentum. Large angle maneuvers can be designed to achieve an arbitrary reorientation of the multibody system with respect to an inertial frame. The theoretical background for carrying out the required maneuvers is summarized.

  7. Chattering-Free Adaptive Sliding Mode Control for Attitude Tracking of Spacecraft with External Disturbance

    Directory of Open Access Journals (Sweden)

    Xuxi Zhang

    2014-01-01

    Full Text Available The attitude tracking problem of spacecraft in the presence of unknown disturbance is investigated. By using the adaptive control technique and the Lyapunov stability theory, a chattering-free adaptive sliding mode control law is proposed for the attitude tracking problem of spacecraft with unknown disturbance. Simulation results are employed to demonstrate the effectiveness of the proposed control design technique in this paper.

  8. Measuring Public Attitudes Toward Natural Resource Issues: Coyote Control

    OpenAIRE

    Arthur, Louise M.

    1981-01-01

    A method to obtain quantitative information on public attitudes toward natural resource issues is described.1 The quantification depends on the structure of the entire survey instrument as well as on individual items in the survey. Items are designed and organized to facilitate (1) the summarizing of measured attitudes toward very complex resource issues, and (2) meaningful comparisons of the summary attitudinal measures to other quantified impacts --economic and physical --for policy analysi...

  9. Semi-active Attitude Control and Off-line Attitude Determination for the SEETI-Express Student Micro-satellite

    OpenAIRE

    Alminde, Lars

    2005-01-01

    This paper concerns the development of the Attitude Determination and Control System (ADCS) for the SSETI-Express micro-satellite mission. The mission is an educational project involving 14 universities and the European Space Agency (ESA). The satellite has been designed and built, by students, over a period of only 18 months. This paper emphasises on the trade-offs required to build an operational ADCS system within such a rapidly developing project.

  10. Semi-active Attitude Control and Off-line Attitude Determination for the SEETI-Express Student Micro-satellite

    DEFF Research Database (Denmark)

    Alminde, Lars

    This paper concerns the development of the Attitude Determination and Control System (ADCS) for the SSETI-Express micro-satellite mission. The mission is an educational project involving 14 universities and the European Space Agency (ESA). The satellite has been designed and built, by students, o......, over a period of only 18 months. This paper emphasises on the trade-offs required to build an operational ADCS system within such a rapidly developing project....

  11. Semi-active Attitude Control and Off-line Attitude Determination for the SSETI-Express Student Micro-satellite

    DEFF Research Database (Denmark)

    Alminde, Lars

    2005-01-01

    This paper concerns the development of the Attitude Determination and Control System (ADCS) for the SSETI-Express micro-satellite mission. The mission is an educational project involving 14 universities and the European Space Agency (ESA). The satellite has been designed and built, by students, o......, over a period of only 18 months. This paper emphasises on the trade-offs required to build an operational ADCS system within such a rapidly developing project....

  12. Plug-and-Play Compatibility for CubeSat Attitude Determination and Control Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of Plug-and-play Compatibility for CubeSat Attitude Determination and Control Systems (ADACS) is proposed. Existing Maryland Aerospace (MAI) ADACS...

  13. The results of flight tests of an attitude control system for the Chibis-M microsatellite

    Science.gov (United States)

    Ivanov, D. S.; Ivlev, N. A.; Karpenko, S. O.; Ovchinnikov, M. Yu.; Roldugin, D. S.; Tkachev, S. S.

    2014-05-01

    The attitude control system of the Chibis-M microsatellite is described. Results of flight experiments on damping the initial angular velocity (made using magnetorquers) are considered, as well as stabilization in the orbital referece frame, and orientation of solar arrays toward the Sun using reaction wheels. The operation of algorithms of satellite attitude determination on sunlit and shadow segments of the orbit is also under study. The general logic of operation of the attitude control system in automatic mode is presented and discussed.

  14. Analysis of a magnetic three-axis stabilized attitude control system for the NPSAT1 spacecraft

    OpenAIRE

    Zirkle, Todd A.

    2001-01-01

    The NPSAT1 satellite uses an active magnetic torque rod system, with a magnetometer for attitude determination, to maintain 3-axis stabilization, with a slightly gravity gradient friendly structure. This thesis will examine the performance of three combinations of programs and simulation models for the NPSAT1 satellite attitude control system. The models include a magnetic control law with a reduced order estimator to generate torque commands to achieve spacecraft nadir pointing and a magneti...

  15. THREE-AXIS AIR-BEARING BASED PLATFORM FOR SMALL SATELLITE ATTITUDE DETERMINATION AND CONTROL SIMULATION.

    OpenAIRE

    Contreras, F.; de Vicente, E; Reyes, L.; G. Bisiacchi; Prado, J; M. Mesinas; Juárez, A

    2005-01-01

    A frictionless environment simulation platform, utilized for accomplishing three-axis attitude control tests in small satellites,is introduced. It is employed to develop, improve, and carry out objective tests of sensors, actuators, and algorithms in theexperimental framework. Different sensors (i.e. sun, earth, magnetometer, and an inertial measurement unit) are utilizedto assess three-axis deviations. A set of three inertial wheels is used as primary actuators for attitude control, together...

  16. Magnetic and Momentum Bias Attitude Control Design for the HETE Small Satellite

    OpenAIRE

    Chang, Daniel

    1992-01-01

    A design study of the attitude control system for the High Energy Transient Experiment (RETE) small satellite is presented. The satellite is 3-axis stabilized and sun pointing, with stringent pointing stability requirements. For actuation, magnetic torquers and a momentum wheel are chosen for their technological maturity and lack of consumables. One science instrument (CCD UV camera) and sun sensors provide attitude measurement. Two complimentary control strategies are implemented to maximize...

  17. Attitude and Vibration Control of Flexible Spacecraft Using Singular Perturbation Approach

    OpenAIRE

    Morteza Shahravi; Milad Azimi

    2014-01-01

    This paper addresses a composite two-time-scale control system for simultaneous three-axis attitude maneuvering and elastic mode stabilization of flexible spacecraft. By choosing an appropriate time coordinates transformation system, the spacecraft dynamics can be divided into double time-scale subsystems using singular perturbation theory (SPT). Attitude and vibration control laws are successively designed by considering a time bandwidths separation between the oscillatory flexible parts mot...

  18. Design and Implementation of Attitude Control for 3-axes Magnetic Coil Stabilization of a Spacecraft

    OpenAIRE

    Tudor, Zdenko

    2011-01-01

    Spacecrafts, especially satellites, play an ever greater rolein our daily lives as we increasingly depend on the services they provide,which in turn, more often than not, critically depend on maintainingcorrect payload attitude. As smaller educational satellites pavethe way for organization, group and privately owned pico-satellites, weexplore the possibilities of attitude control through magnetic coil actuation.We approach the whole problem, from control theory developmentto first prototype ...

  19. Attitude-Tracking Control with Path Planning for Agile Satellite Using Double-Gimbal Control Moment Gyros

    Directory of Open Access Journals (Sweden)

    Peiling Cui

    2012-01-01

    Full Text Available In view of the issue of rapid attitude maneuver control of agile satellite, this paper presents an attitude-tracking control algorithm with path planning based on the improved genetic algorithm, adaptive backstepping control as well as sliding mode control. The satellite applies double gimbal control moment gyro as actuator and is subjected to the external disturbance and uncertain inertia properties. Firstly, considering the comprehensive mathematical model of the agile satellite and the double gimbal control moment gyro, an improved genetic algorithm is proposed to solve the attitude path-planning problem. The goal is to find an energy optimal path which satisfies certain maneuverability under the constraints of the input saturation, actuator saturation, slew rate limit and singularity measurement limit. Then, the adaptive backstepping control and sliding mode control are adopted in the design of the attitude-tracking controller to track accurately the desired path comprised of the satellite attitude quaternion and velocity. Finally, simulation results indicate the robustness and good tracking performance of the derived controller as well as its ability to avert the singularity of double gimbal control moment gyro.

  20. Improved optimal steering law for SGCMG and adaptive attitude control of flexible spacecraft

    Institute of Scientific and Technical Information of China (English)

    Lu Wang; Yu Guo; Liping Wu; Qingwei Chen

    2015-01-01

    The issue of attitude maneuver of a flexible spacecraft is investigated with single gimbaled control moment gyroscopes (SGCMGs) as an actuator. To solve the inertia uncertainty of the system, an adaptive attitude control algorithm is designed by ap-plying a radial basis function (RBF) neural network. An improved steering law for SGCMGs is proposed to achieve the optimal out-put torque. It enables the SGCMGs not only to avoid singularity, but also to output more precise torque. In addition, global, uniform, ultimate bounded stability of the attitude control system is proved via the Lyapunov technique. Simulation results demonstrate the effectiveness of the new steering law and the algorithm of attitude maneuver of the flexible spacecraft.

  1. Adaptive variable structure control based on backstepping for spacecraft with reaction wheels during attitude maneuver

    Institute of Scientific and Technical Information of China (English)

    SONG Bin; MA Guang-fu; LI Chuan-jiang

    2009-01-01

    An adaptive variable structure control method based on backstepping is proposed for the attitude maneuver problem of rigid spacecraft with reaction wheel dynamics in the presence of uncertain inertia matrix and external disturbances. The proposed control approach is a combination of the backstepping and the adaptive variable structure control. The cascaded structure of the attitude maneuver control system with reaction wheel dynamics gives the advantage for applying the backstepping method to construct Lyapunov functions. The robust stability to external disturbances and parametric uncertainty is guaranteed by the adaptive variable structure control. To validate the proposed control algorithm, numerical simulations using the proposed approach are performed for the attitude maneuver mission of rigid spacecraft with a configuration consisting of four reaction wheels for actuator and three magnetorquers for momentum unloading. Simulation results verify the effectiveness of the proposed control algorithm.

  2. Precision Integrated Power and Attitude Control System (IPACS) in the Presence of Dynamic Uncertainty

    Science.gov (United States)

    Kim, D.; MacKunis, W.; Fitz-Coy, N.; Dixon, W. E.

    2011-01-01

    An adaptive robust integrated power and attitude control system (IPACS) is presented for a variable speed control moment gyroscope (VSCMG)-actuated satellite. The developed IPACS method is capable of achieving precision attitude control while simultaneously achieving asymptotic power tracking for a rigid-body satellite in the presence of uncertain friction in the VSCMG gimbals and wheels. In addition, the developed controller compensates for the effects of uncertain, time-varying satellite inertia properties. Some challenges encountered in the control design are that the control input is premultiplied by a nonsquare, time-varying, nonlinear, uncertain matrix and is embedded in a discontinuous nonlinear. Globally uniformly ultimately bounded attitude tracking and asymptotic power tracking results are proven via Lyapunov stability analyses, and simulation results are provided to demonstrate the performance of the controller.

  3. Attitude stabilization of electrodynamic tethers in elliptic orbits by time-delay feedback control

    Science.gov (United States)

    Iñarrea, Manuel; Lanchares, Víctor; Pascual, Ana Isabel; Salas, José Pablo

    2014-03-01

    It is well known that libration motion of electrodynamic tethers operating in inclined orbits is affected by dynamic instability due to the electromagnetic interaction between the tether and the geomagnetic field. We study the application of two feedback control methods in order to stabilize the periodic attitude motions of electrodynamic tethers in elliptic inclined orbits. Both control schemes are based on the time-delayed autosynchronization of the system. Numerical simulations of the controlled libration motion show that both control techniques are able to transform the uncontrolled unstable periodic motions into asymptotically stable ones. Such stabilized periodic attitude motions can be taken as starting points for the operation of the tether. The control domains of both methods have been computed for different values of the system parameters, as functions of the two control parameters shared by both control schemes. The relative effectiveness of the two techniques in the stabilization of the periodic attitude motion has also been studied.

  4. Student Compliance and Attitude: A Function of Classroom Control Technique.

    Science.gov (United States)

    Houser, Betsy B.

    This paper examines the effects of a teacher's classroom utilization of certain means of social influence or bases of social power (reward, coercive, referent, legitimate, and informational) upon: (1) level of student compliance, and (2) attitude of the student toward the teacher. A total of 588 white, middle-class fourth, fifth, and sixth grade…

  5. On-orbit attitude control of the Cosmic Background Explorer (COBE)

    Science.gov (United States)

    Bramberg, B.; Croft, J.

    1985-01-01

    The way in which COBE (launched by the SS in late 1982) performs its attitude control is described, along with the design of its on-orbit system. COBE, to be situated in a 900 km high, sun-synchronous orbit, contains two unique control features: (1) the orientation of the spinning satellite is controlled to a sun-normal attitude in the sun/local vertical plane; and (2) pitch and roll control is maintained by a unique triaxial arrangement of reaction wheels, magnetic torque bars and sensors, located in the body's tranverse plane. Inherent in this triaxial configuration concept is a built-in redundancy that will maintain attitude control in the event of any single-point sensor/actuator component failure. Each of the three control drive electronics operates independently and directly of a system of dedicated sensors. This system functions independently of a computer or an ephemeris communication link, leading to greater reliability.

  6. Fixed-Star Tracking Attitude Control of Spacecraft Using Single-Gimbal Control Moment Gyros

    Directory of Open Access Journals (Sweden)

    Sangwon Kwon

    2010-01-01

    Full Text Available Problem statement: A cluster of small-sized Single-Gimbal Control Moment Gyros (SGCMGs is proposed as an attitude control actuator for high-speed maneuver of small satellites. There exists a singularity problem what is peculiar to the CMG system. Approach: This study presented a simple singularity avoidance steering law using the Singular Value Decomposition (SVD algorithm. Results: Capability of the present steering method in singularity avoidance was demonstrated with numerical simulations for fixed-star tracking control of a small satellite using four SGCMGs. Conclusion: The proposed steering law utilizes the singular value decomposition to obtain singular vectors and generates the command gimbal rate that keeps the command torque in the direction orthogonal to the singular direction with a maximum gain.

  7. Exploiting environmental torques for attitude control and determination of spin stabilized satellites

    Science.gov (United States)

    Gluck, R.

    1974-01-01

    Design techniques are presented which exploit environmental torques for attitude control and determination of spin stabilized satellites. The techniques are applicable to satellite missions where the dominant environmental torques are well understood and lend themselves to accurate analytical modeling. The techniques were applied to the Particles and Fields subsatellites of the Apollo 15 and 16 spacecraft and the flight results show good agreement with the attitude determination estimates obtained.

  8. Micro Sun Sensor with CMOS Imager for Small Satellite Attitude Control

    OpenAIRE

    Yoshihara, Keisuke; Hashimoto, Hidekazu; Yamamoto, Toru; Saito, Hirobumi; HIROKAWA, Eiji; Mita, Makoto; Magoshi, Kota

    2005-01-01

    A new type of Micro Sun Sensor (MSS) was started development for use on JAXA’s small satellites and space exploring spacecraft as attitude sensor. In recent years, small satellites are used for various missions, such as the Earth observation and science observation, and high functional attitude control system for small satellite is also required. Therefore, the sun sensor for small satellite is required to be good balance of its dimension, mass, power consumption and performance. The detector...

  9. A Precise Attitude Determination and Control Strategy for Small Astrometry Satellite “Nano-JASMINE”

    OpenAIRE

    Hosonuma, Takayuki

    2012-01-01

    Intelligent Space Systems Laboratory (ISSL) Universityof Tokyo has developed a 35 kgastrometry satellite,“Nano-JASMINE”(Nano JAPAN Astrometry Satellite Mission for INfraredExploration)in cooperation with National Astronomical Observatoryof Japan (NAOJ). In the Nano-JASMINE mission, the satellite attitude spin rate should be controlled to an accuracy of 4 × 10−7 rad/s duringthe observation. To accomplish such severe attitude stabilization, we have developed two novelmethods. The first method i...

  10. A comparison of dysfunctional attitudes in substance abusers and control group and its psychological outcome

    OpenAIRE

    2008-01-01

    Objectives: Addiction researchers find that addictive processes are influenced by patient beliefs and attitudes. This research was carried out to assess the role of dysfunctional attitudes, outcomes of psychology in substance abuse behaviors of subject were referred to addiction treatment center in the city of Bandar Abbas, and to compare the with the control group. Methods: This is a retrospective study in which 100 subject substance abusers were compared with 100 subject s of c...

  11. A computed torque method based attitude control with optimal force distribution for articulated body mobile robots

    International Nuclear Information System (INIS)

    This paper introduces an attitude control scheme based in optimal force distribution using quadratic programming which minimizes joint energy consumption. This method shares similarities with force distribution for multifingered hands, multiple coordinated manipulators and legged walking robots. In particular, an attitude control scheme was introduced inside the force distribution problem, and successfully implemented for control of the articulated body mobile robot KR-II. This is an actual mobile robot composed of cylindrical segments linked in series by prismatic joints and has a long snake-like appearance. These prismatic joints are force controlled so that each segment's vertical motion can automatically follow the terrain irregularities. An attitude control is necessary because this system acts like a system of wheeled inverted pendulum carts connected in series, being unstable by nature. The validity and effectiveness of the proposed method is verified by computer simulation and experiments with the robot KR-II. (author)

  12. A computed torque method based attitude control with optimal force distribution for articulated body mobile robots

    Energy Technology Data Exchange (ETDEWEB)

    Fukushima, Edwardo F.; Hirose, Shigeo [Tokyo Inst. of Tech. (Japan)

    2000-05-01

    This paper introduces an attitude control scheme based in optimal force distribution using quadratic programming which minimizes joint energy consumption. This method shares similarities with force distribution for multifingered hands, multiple coordinated manipulators and legged walking robots. In particular, an attitude control scheme was introduced inside the force distribution problem, and successfully implemented for control of the articulated body mobile robot KR-II. This is an actual mobile robot composed of cylindrical segments linked in series by prismatic joints and has a long snake-like appearance. These prismatic joints are force controlled so that each segment's vertical motion can automatically follow the terrain irregularities. An attitude control is necessary because this system acts like a system of wheeled inverted pendulum carts connected in series, being unstable by nature. The validity and effectiveness of the proposed method is verified by computer simulation and experiments with the robot KR-II. (author)

  13. Crew exploration vehicle (CEV) attitude control using a neural-immunology/memory network

    Science.gov (United States)

    Weng, Liguo; Xia, Min; Wang, Wei; Liu, Qingshan

    2015-01-01

    This paper addresses the problem of the crew exploration vehicle (CEV) attitude control. CEVs are NASA's next-generation human spaceflight vehicles, and they use reaction control system (RCS) jet engines for attitude adjustment, which calls for control algorithms for firing the small propulsion engines mounted on vehicles. In this work, the resultant CEV dynamics combines both actuation and attitude dynamics. Therefore, it is highly nonlinear and even coupled with significant uncertainties. To cope with this situation, a neural-immunology/memory network is proposed. It is inspired by the human memory and immune systems. The control network does not rely on precise system dynamics information. Furthermore, the overall control scheme has a simple structure and demands much less computation as compared with most existing methods, making it attractive for real-time implementation. The effectiveness of this approach is also verified via simulation.

  14. Direct Lyapunov-based control law design for spacecraft attitude maneuvers

    Institute of Scientific and Technical Information of China (English)

    HU Likun; ANG Qingchao

    2006-01-01

    A direct Lyapunov-based control law is presented to perform on-orbit stability for spacecraft attitude maneuvers. Spacecraft attitude kinematic equations and dynamic equations are coupled, nonlinear, multi-input multi-output(MIMO), which baffles controller design. Orbit angular rates are taken into account in kinematic equations and influence of gravity gradient moments and disturbance moments on the spacecraft attitude in dynamic equations is considered to approach the practical environment, which enhance the problem complexity to some extent. Based on attitude tracking errors and angular rates, a Lyapunov function is constructed, through which the stabilizing feedback control law is deduced via Lie derivation of the Lyapunov function. The proposed method can deal with the case that the spacecraft is subjected to mass property variations or centroidal inertia matrix variations due to fuel assumption or flexibility, and disturbance moments, which shows the proposed controller is robust for spacecraft attitude maneuvers. The unlimited controller and the limited controller are taken into account respectively in simulations. Simulation results are demonstrated to validate effectiveness and feasibility of the proposed method.

  15. Attitude control of a space structure using a 3-R rigid manipulator

    Science.gov (United States)

    Mukherjee, Ranjan; Zurowski, Mary

    The attitude control of space structures is an important problem. There has been considerable research in this area that has focussed on the use of momentum exchange devices. In this paper, we propose to control the attitude of space structures using a serial three-link PUMA-type manipulator that can be mounted on the space structure. This unconventional method of attitude control exploits the nonholonomic nature of the constraints that arise due to the conservation of angular momentum. We adopt a surface integral approach for the motion planning of the manipulator that will reorient the space structure in any desired way. The salient features of our algorithm are: (a) it is possible to mathematically prove the controllability of the system; (b) The motion of the manipulator can be planned amidst additional constraints like joint limits of the manipulator; and (c) the algorithm can be easily extended for application to flexible space structures.

  16. Design and simulation of satellite attitude control system based on Simulink and VR

    Science.gov (United States)

    Zhang, Yang; Gan, Qingbo; Kang, Jingshu

    2016-01-01

    In order to research satellite attitude control system design and visual simulation, the simulation framework of satellite dynamics and attitude control using Simulink were established. The design of satellite earth-oriented control system based on quaternion feedback was completed. The 3D scene based on VR was created and models in the scene were driven by simulation data of Simulink. By coordinate transformation. successful observing the scene in inertial coordinate system, orbit coordinate system and body coordinate system. The result shows that application of simulation method of Simulink combined with VR in the design of satellite attitude control system field, has the advantages of high confidence level, hard real-time property, multi-perspective and multi-coordinate system observing the scene, and improves the comprehensibility and accuracy of the design.

  17. Combined control of fast attitude maneuver and stabilization for large complex spacecraft

    Science.gov (United States)

    Zhang, Yao; Zhang, Jing-Rui

    2013-12-01

    In remote sensing or laser communication space missions, spacecraft need fast maneuver and fast stabilization in order to accomplish agile imaging and attitude tracking tasks. However, fast attitude maneuvers can easily cause elastic deformations and vibrations in flexible appendages of the spacecraft. This paper focuses on this problem and deals with the combined control of fast attitude maneuver and stabilization for large complex spacecraft. The mathematical model of complex spacecraft with flexible appendages and momentum bias actuators on board is presented. Based on the plant model and combined with the feedback controller, modal parameters of the closed-loop system are calculated, and a multiple mode input shaper utilizing the modal information is designed to suppress vibrations. Aiming at reducing vibrations excited by attitude maneuver, a quintic polynomial form rotation path planning is proposed with constraints on the actuators and the angular velocity taken into account. Attitude maneuver simulation results of the control systems with input shaper or path planning in loop are separately analyzed, and based on the analysis, a combined control strategy is presented with both path planning and input shaper in loop. Simulation results show that the combined control strategy satisfies the complex spacecraft's requirement of fast maneuver and stabilization with the actuators' torque limitation satisfied at the same time.

  18. Robust attitude control for rapid multi-target tracking in spacecraft formation flying

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A robust attitude tracking control scheme for spacecraft formation flying is presented.The leader spacecraft with a.rapid mobile antenna and a camera is modeled.While the camera is tracking the ground target,the antenna is tracking the follower spacecraft.By an angular velocity constraint and an angular constraint,two methods are proposed to compute the reference attitude profiles of the camera and antenna,respectively.To simplify the control design problem,this paper first derives the desired inverse system (DIS),which can convert the attitude tracking problem of 3D space into the regulator problem.Based on DIS and sliding mode control (SMC),a robust attitude tracking controller is developed in the presence of mass parameter uncertainties and external disturbance.By Lyapunov stability theory,the closed loop system stability can be achieved.The numerical simulations show that the proposed robust control scheme exhibits significant advantages for the multi-target attitude tracking of a two-spacecraft formation.

  19. New optimal control laws for attitude of a rigid body motion without angular velocity measurements

    Energy Technology Data Exchange (ETDEWEB)

    El-Gohary, Awad [Department of Statistics and Operational Research, Faculty of Science King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)] e-mail: aigohary@ksu.edu.sa

    2005-08-01

    In this paper we shall use the passive properties of Euler dynamic equations as well as the structural properties of kinematic equations in terms of Cayley-Rodrigues and Modified Rodrigues parameters to derive optimal control laws without any information about the angular velocity of the rigid body. The interesting difference in the current study is the assumption that only the kinematics attitude parameters are available for the control process. The optimal control laws ensure the optimal asymptotic stability of the rigid body motion and minimize a selecting performance are obtained in terms of the kinematics attitude parameters and their estimates. Numerical examples are presented to demonstrate the theoretical results.

  20. The Development of a Low Cost, Modular Attitude Determination and Control System

    OpenAIRE

    Surka, Derek; Paluszek, Michael

    1997-01-01

    In an attempt to reduce the cost of future satellites, new technologies are being pursued to develop a modular attitude determination and control system that will provide three-axis control and cost less than ten percent of present systems. The low cost and modularity of this system make it especially attractive to a wide variety of small satellites. This paper will present the design and developmental status of this "plug and play" attitude control system. The general idea is to provide a co...

  1. Spacecraft Hybrid (Mixed-Actuator) Attitude Control Experiences on NASA Science Missions

    Science.gov (United States)

    Dennehy, Cornelius J.

    2014-01-01

    There is a heightened interest within NASA for the design, development, and flight implementation of mixed-actuator hybrid attitude control systems for science spacecraft that have less than three functional reaction wheel actuators. This interest is driven by a number of recent reaction wheel failures on aging, but what could be still scientifically productive, NASA spacecraft if a successful hybrid attitude control mode can be implemented. Over the years, hybrid (mixed-actuator) control has been employed for contingency attitude control purposes on several NASA science mission spacecraft. This paper provides a historical perspective of NASA's previous engineering work on spacecraft mixed-actuator hybrid control approaches. An update of the current situation will also be provided emphasizing why NASA is now so interested in hybrid control. The results of the NASA Spacecraft Hybrid Attitude Control Workshop, held in April of 2013, will be highlighted. In particular, the lessons learned captured from that workshop will be shared in this paper. An update on the most recent experiences with hybrid control on the Kepler spacecraft will also be provided. This paper will close with some future considerations for hybrid spacecraft control.

  2. Near minimum-time feedback attitude control with multiple saturation constraints for agile satellites

    Institute of Scientific and Technical Information of China (English)

    Liu Xiangdong; Xin Xing; Li Zhen; Chen Zhen; Sheng Yongzhi

    2016-01-01

    Agile satellites are of importance in modern aerospace applications, but high mobility of the satellites may cause them vulnerable to saturation during attitude maneuvers due to limited rating of actuators. This paper proposes a near minimum-time feedback control law for the agile satellite attitude control system. The feedback controller is formed by specially designed cascaded sub-units. The rapid dynamic response of the modified Bang–Bang control logic achieves the near optimal property and ensures the non-saturation properties on three-axis. To improve the dynamic performance, a model reference control strategy is proposed, in which the on-line near optimal attitude maneuver path is generated by the cascade controller and is then tracked by a nonlinear back-stepping controller. Furthermore, the accuracy and the robustness of the control system are achieved by momentum-based on-line inertial identification. The rapid attitude maneuvering can be applied for tasks including the move to move case. Numerical simulations are conducted to verify the effectiveness of the proposed control strategy in terms of the saturation-free property and rapidness.

  3. Maternal and Paternal Psychological Control as Moderators of the Link between Peer Attitudes and Adolescents’ Risky Sexual Behavior

    OpenAIRE

    Oudekerk, Barbara A.; Allen, Joseph P.; Hafen, Christopher A.; Hessel, Elenda T.; Szwedo, David E.; Spilker, Ann

    2013-01-01

    Maternal and paternal psychological control, peer attitudes, and the interaction of psychological control and peer attitudes at age 13 were examined as predictors of risky sexual behavior before age 16 in a community sample of 181 youth followed from age 13 to 16. Maternal psychological control moderated the link between peer attitudes and sexual behavior. Peer acceptance of early sex predicted greater risky sexual behaviors, but only for teens whose mothers engaged in high levels of psycholo...

  4. An Attitude Control System for SumbandilaSAT an Earth Observation Satellite

    Science.gov (United States)

    Steyn, W. H.

    2008-08-01

    This paper describes the attitude determination and control system to support the multi-spectral earth observation main payload of the SumbandilaSAT microsatellite. The satellite has only a single main Y- body mounted solar panel and the attitude control system must ensure a nominal sun-pointed attitude under all non-imaging conditions during the sunlit part of the orbit. The control actuators employed are 3- axis magnetic torquer rods and reaction wheels. During initial detumbling and safe mode operations a simple new magnetic control law is used to bring the satellite to a sun-pointed Y-spinning attitude for maximum solar power collection. From this sun-pointed, spinning attitude an intermediate control mode is entered when the Y-reaction wheel is utilised as a momentum wheel, to absorb the body spin rate and to inertially stabilise the angular momentum vector towards the sun direction. During the intermediate mode the magnetic rods are used to maintain the momentum vector size and direction and to do nutation damping. The pitch angle is also controlled using the Y-wheel, to keep the main imager payload as close as possible to an earth-pointed attitude and to thermally stabilise the imager telescope. The final and nominal attitude control mode is entered when a zero biased 3-axis reaction wheel controller is enabled, for: 1) sun tracking for optimal solar power collection, 2) target tracking during viewfinder use or during imaging download communication with a ground station and 3) pushbroom imager scanning with a forward motion compensation capability. During the nominal mode the magnetic rods are used to dump the angular momentum from the reaction wheels during sun tracking periods. A short introduction to the Sumbandila satellite will be given. All the control modes, the attitude sensors and estimators utilised, will be introduced in the paper. Specifically, a unique agile viewfinder control mode to manually select targets for subsequent high resolution image

  5. Quaternion-based adaptive output feedback attitude control of spacecraft using Chebyshev neural networks.

    Science.gov (United States)

    Zou, An-Min; Dev Kumar, Krishna; Hou, Zeng-Guang

    2010-09-01

    This paper investigates the problem of output feedback attitude control of an uncertain spacecraft. Two robust adaptive output feedback controllers based on Chebyshev neural networks (CNN) termed adaptive neural networks (NN) controller-I and adaptive NN controller-II are proposed for the attitude tracking control of spacecraft. The four-parameter representations (quaternion) are employed to describe the spacecraft attitude for global representation without singularities. The nonlinear reduced-order observer is used to estimate the derivative of the spacecraft output, and the CNN is introduced to further improve the control performance through approximating the spacecraft attitude motion. The implementation of the basis functions of the CNN used in the proposed controllers depends only on the desired signals, and the smooth robust compensator using the hyperbolic tangent function is employed to counteract the CNN approximation errors and external disturbances. The adaptive NN controller-II can efficiently avoid the over-estimation problem (i.e., the bound of the CNNs output is much larger than that of the approximated unknown function, and hence, the control input may be very large) existing in the adaptive NN controller-I. Both adaptive output feedback controllers using CNN can guarantee that all signals in the resulting closed-loop system are uniformly ultimately bounded. For performance comparisons, the standard adaptive controller using the linear parameterization of spacecraft attitude motion is also developed. Simulation studies are presented to show the advantages of the proposed CNN-based output feedback approach over the standard adaptive output feedback approach. PMID:20729168

  6. A distributed system adaptive control strategy. [for attitude control of large spacecraft

    Science.gov (United States)

    Johnson, C. R., Jr.; Montgomery, R. C.

    1979-01-01

    One attitude control device being studied for large spacecraft consists of two counter-rotating rings, each designated as an annular momentum control device (AMCD), that are attached to a spacecraft using several magnetic bearings distributed along the circumference of the rings. For large spacecraft large rings are desirable. Unfortunately, for large rings flexibility is appreciable and it becomes necessary to account for the distributed nature of the rings in the design of the magnetic bearing controllers. Also ring behavior is unpredictably sensitive to ring temperature, spin rate, manufacturing imperfections, and other variables. For that reason a distributed adaptive microcomputer-based control system is being sought for ring stabilization and maneuvering. An original adaptive-control methodology for distributed-parameter systems is detailed and application to spinning ring, i.e., AMCD, stabilization is used as an illustration. The proposed methodology, presented as a step-by-step procedure, combines a lumped-parameter expansion description of distributed parameter systems with a fundamental simultaneous identification and control strategy. Simulations are presented providing preliminary evidence of the capabilities of the proposed procedure.

  7. Structural control interaction for an LSS attitude control system using thrusters and reaction wheels

    Science.gov (United States)

    da Fonseca, Ijar M.; Bainum, Peter M.; da Silva, Adenilson R.

    2007-05-01

    This work provides some important information about control structure interaction (CSI) for a large space structure (LSS) attitude control subsystem (ACS) comprised of thrusters and reaction wheels. The LSS physical model is assumed as a rigid long tubular beam as the main bus with two attached long flexible solar panels. Two thrusters (one at each tip of the LSS) are used for large amplitude maneuvers and the reaction wheels for fine control. Lagrange's formulations for generalized and quasi-coordinates were used to derive the equations of motion. The gravity gradient, the solar pressure and the drag were included in the mathematical model as external perturbations. The assumed modes discretization method has been used to model the solar array elastic displacements so as to obtain a set of ordinary differential equations to describe the LSS motion. Different control strategies were implemented to analyze the CSI for two configurations, fine and coarse control. The MatLab/Simulink platform has been used for the computational simulations. The results are in agreement with the CSI theory in that thruster firings excite the solar panel vibrations and that the elastic vibration is an important issue to be taken into account for LSS ACS performance evaluation for both fine and coarse control. In spite of the CSI the maneuver objectives have been accomplished with results that meet the mission criteria.

  8. Weight Control Beliefs, Body Shape Attitudes, and Physical Activity among Adolescents

    Science.gov (United States)

    Martin, Scott B.; Rhea, Deborah J.; Greenleaf, Christy A.; Judd, Doryce E.; Chambliss, Heather O.

    2011-01-01

    Background: Relatively little is known about how perceived weight controllability influences important psychological health factors among adolescents. Thus, the purpose of this study is to explore adolescents' weight controllability beliefs and how those beliefs influence weight-related attitudes and behaviors. Methods: Adolescents (N = 369, mean…

  9. Methods for attitude guidance and precise robust gyromoment control of large-scale agile observation spacecraft

    Science.gov (United States)

    Somov, Sergey; Butyrin, Sergey; Somov, Yevgeny

    2012-11-01

    Problems on guidance and robust gyromoment attitude control of agile information satellite for remote sensing the Earth surface are considered. Elaborated methods for dynamic research of the spacecraft programmed angular motion at principle modes under external and parametric disturbances, partial discrete measurement of the state and digital control of the gyro moment cluster by the excessive gyrodine schemes, are presented.

  10. Attitude Control of Quad-rotor by Improving the Reliability of Multi-Sensor System

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Dong Hyeon; Chong, Kil To [Chon-bok National University, Jeonju (Korea, Republic of); Park, Jong Ho [Seonam University, Namwon (Korea, Republic of); Ryu, Ji Hyoung [ETRI, Daejeon (Korea, Republic of)

    2015-05-15

    This paper presents the results of study for improving the reliability of quadrotor attitude control by applying a multi-sensor along with a data fusion algorithm. First, a mathematical model of the quadrotor dynamics was developed. Then, using the quadrotor mathematical model, simulations were performed using the improved reliability multi-sensor data as the inputs. From the simulation results, we designed a Gimbal-equipped quadrotor system. With the quadrotor in a hover state, we performed experiments according to the angle change of the user's specifications . We then calculated the attitude control data from the actual experimental data. Furthermore, with additional simulations, we verified the performance of the designed quadrotor attitude control system with multiple sensors.

  11. Attitude Control of Quad-rotor by Improving the Reliability of Multi-Sensor System

    International Nuclear Information System (INIS)

    This paper presents the results of study for improving the reliability of quadrotor attitude control by applying a multi-sensor along with a data fusion algorithm. First, a mathematical model of the quadrotor dynamics was developed. Then, using the quadrotor mathematical model, simulations were performed using the improved reliability multi-sensor data as the inputs. From the simulation results, we designed a Gimbal-equipped quadrotor system. With the quadrotor in a hover state, we performed experiments according to the angle change of the user's specifications . We then calculated the attitude control data from the actual experimental data. Furthermore, with additional simulations, we verified the performance of the designed quadrotor attitude control system with multiple sensors

  12. Small satellite attitude control for sun-oriented operations utilizing a momentum bias with magnetic actuators

    OpenAIRE

    Wolfe, Scott Michael

    1995-01-01

    The feasibility of using a three axis control, momentum bias system with magnetic actuators for sun-oriented operations is explored. Relevant equations of motion are developed for a sun-oriented coordinate system and control laws are developed for: initial spacecraft capture after launch vehicle separation; reorientation from Earth oriented to a sun oriented operations mode; sun-oriented attitude control; and momentum wheel control. Simulations demonstrating the stability and time responsiven...

  13. Microsatellite Attitude Determination and Control Subsystem Design and Implementation: Software-in-the-Loop Approach

    Directory of Open Access Journals (Sweden)

    Ho-Nien Shou

    2014-01-01

    Full Text Available The paper describes the development of a microsatellite attitude determination and control subsystem (ADCS and verification of its functionality by software-in-the-loop (SIL method. The role of ADCS is to provide attitude control functions, including the de-tumbling and stabilizing the satellite angular velocity, and as well as estimating the orbit and attitude information during the satellite operation. In Taiwan, Air Force Institute of Technology (AFIT, dedicating for students to design experimental low earth orbit micro-satellite, called AFITsat. For AFITsat, the operation of the ADCS consists of three modes which are initialization mode, detumbling mode, and normal mode, respectively. During the initialization mode, ADCS collects the early orbit measurement data from various sensors so that the data can be downlinked to the ground station for further analysis. As particularly emphasized in this paper, during the detumbling mode, ADCS implements the thrusters in plus-wide modulation control method to decrease the satellite angular velocity. ADCS provides the attitude determination function for the estimation of the satellite state, during normal mode. The three modes of microsatellite adopted Kalman filter algorithm estimate microsatellite attitude. This paper will discuss using the SIL validation ADCS function and verify its feasibility.

  14. Design and Integration of an All-Magnetic Attitude Control System for FASTSAT-HSV01's Multiple Pointing Objectives

    Science.gov (United States)

    DeKock, Brandon; Sanders, Devon; Vanzwieten, Tannen; Capo-Lugo, Pedro

    2011-01-01

    The FASTSAT-HSV01 spacecraft is a microsatellite with magnetic torque rods as it sole attitude control actuator. FASTSAT s multiple payloads and mission functions require the Attitude Control System (ACS) to maintain Local Vertical Local Horizontal (LVLH)-referenced attitudes without spin-stabilization, while the pointing errors for some attitudes be significantly smaller than the previous best-demonstrated for this type of control system. The mission requires the ACS to hold multiple stable, unstable, and non-equilibrium attitudes, as well as eject a 3U CubeSat from an onboard P-POD and recover from the ensuing tumble. This paper describes the Attitude Control System, the reasons for design choices, how the ACS integrates with the rest of the spacecraft, and gives recommendations for potential future applications of the work.

  15. Control, Attitudes de se and Immunity to Error Through Misidentification

    Directory of Open Access Journals (Sweden)

    Gaetano Fiorin

    2014-08-01

    Full Text Available In his work on attitudes de se, James Higginbotham has observed that the silent subject of the infinitival complements of verbs such as remember and imagine is (i unambiguously de se and (ii immune to error through misidentification relatively to the subject of the matrix clause. In this article, we review and criticize Higginbotham’s reflexive analysis of these infinitival complements. We also show that the type of criticism we raise against Higginbotham’s account applies likewise to analyses based on the use of acquaintance relations and centered possible worlds. Finally, following recent ideas in cognitive science, we propose an amendment to Higginbotham’s account based on the idea that the thematic-role “Experiencer” corresponds to a function mapping events into “minimal selves”, in the sense of Shaun Gallagher.

  16. Finite-Time Anti-Disturbance Inverse Optimal Attitude Tracking Control of Flexible Spacecraft

    Directory of Open Access Journals (Sweden)

    Chutiphon Pukdeboon

    2013-01-01

    Full Text Available We propose a new robust optimal control strategy for flexible spacecraft attitude tracking maneuvers in the presence of external disturbances. An inverse optimal control law is designed based on a Sontag-type formula and a control Lyapunov function. An adapted extended state observer is used to compensate for the total disturbances. The proposed controller can be expressed as the sum of an inverse optimal control and an adapted extended state observer. It is shown that the developed controller can minimize a cost functional and ensure the finite-time stability of a closed-loop system without solving the associated Hamilton-Jacobi-Bellman equation directly. For an adapted extended state observer, the finite-time convergence of estimation error dynamics is proven using a strict Lyapunov function. An example of multiaxial attitude tracking maneuvers is presented and simulation results are included to show the performance of the developed controller.

  17. Design and analysis of a moment control unit for agile satellite with high attitude stability requirement

    Science.gov (United States)

    Zhang, Yao; Li, Mou; Song, Zhuoyue; Shan, Jinjun; Guan, Xin; Tang, Liang

    2016-05-01

    A moment control unit is developed and verified by numerical simulation. This moment control unit is employed as an actuator for the satellite attitude control. It contains four control moment gyroscopes (CMGs) to realize the rapid attitude maneuver and a vibration isolation system for each CMG. This unit can not only reduce the required electronics for each CMG and thus the weight, but also improve the stability of the satellite attitude. The design of the structure is presented first. This structure not only holds and protects the CMGs, but also isolates the vibrations caused by each CMG. Then, a dynamic model of a single CMG with a vibration isolation system is formulated, and the time- and frequency-domain characteristics of this dynamic model are discussed. Numerical simulations of a satellite attitude control example are then used to evaluate the system. The new moment control unit occupies less volume than previous designs, and the results show that the new design improves satellite pointing performance because of the vibration isolation.

  18. Multivariable control theory applied to hierarchial attitude control for planetary spacecraft

    Science.gov (United States)

    Boland, J. S., III; Russell, D. W.

    1972-01-01

    Multivariable control theory is applied to the design of a hierarchial attitude control system for the CARD space vehicle. The system selected uses reaction control jets (RCJ) and control moment gyros (CMG). The RCJ system uses linear signal mixing and a no-fire region similar to that used on the Skylab program; the y-axis and z-axis systems which are coupled use a sum and difference feedback scheme. The CMG system uses the optimum steering law and the same feedback signals as the RCJ system. When both systems are active the design is such that the torques from each system are never in opposition. A state-space analysis was made of the CMG system to determine the general structure of the input matrices (steering law) and feedback matrices that will decouple the axes. It is shown that the optimum steering law and proportional-plus-rate feedback are special cases. A derivation of the disturbing torques on the space vehicle due to the motion of the on-board television camera is presented. A procedure for computing an upper bound on these torques (given the system parameters) is included.

  19. Finite-Time Reentry Attitude Control Using Time-Varying Sliding Mode and Disturbance Observer

    Directory of Open Access Journals (Sweden)

    Xuzhong Wu

    2015-01-01

    Full Text Available This paper presents the finite-time attitude control problem for reentry vehicle with redundant actuators in consideration of planet uncertainties and external disturbances. Firstly, feedback linearization technique is used to cancel the nonlinearities of equations of motion to construct a basic mode for attitude controller. Secondly, two kinds of time-varying sliding mode control methods with disturbance observer are integrated with the basic mode in order to enhance the control performance and system robustness. One method is designed based on boundary layer technique and the other is a novel second-order sliding model control method. The finite-time stability analyses of both resultant closed-loop systems are carried out. Furthermore, after attitude controller produces the torque commands, an optimization control allocation approach is introduced to allocate them into aerodynamic surface deflections and on-off reaction control system thrusts. Finally, the numerical simulation results demonstrate that both of the time-varying sliding mode control methods are robust to uncertainties and disturbances without chattering phenomenon. Moreover, the proposed second-order sliding mode control method possesses better control accuracy.

  20. Hierarchical structured robust adaptive attitude controller design for reusable launch vehicles

    Institute of Scientific and Technical Information of China (English)

    Guangxue Yu; Huifeng Li

    2015-01-01

    Reentry attitude control for reusable launch vehicles (RLVs) is chal enging due to the characters of fast nonlinear dy-namics and large flight envelop. A hierarchical structured attitude control system for an RLV is proposed and an unpowered RLV con-trol model is developed. Then, the hierarchical structured control frame consisting of attitude control er, compound control strategy and control al ocation is presented. At the core of the design is a robust adaptive control (RAC) law based on dual loop time-scale separation. A radial basis function neural network (RBFNN) is implemented for compensation of uncertain model dynamics and external disturbances in the inner loop. And then the robust op-timization is applied in the outer loop to guarantee performance robustness. The overal control design frame retains the simplicity in design while simultaneously assuring the adaptive and robust performance. The hierarchical structured robust adaptive con-trol er (HSRAC) incorporates flexibility into the design with regard to control er versatility to various reentry mission requirements. Simulation results show that the improved tracking performance is achieved by means of RAC.

  1. Attitude Control of a Six-Legged Robot in Consideration of Actuator Dynamics by Optimal Servo Control System

    OpenAIRE

    Uchida, H.; Nonami, K.

    2007-01-01

    In the present study, we examined the attitude control method considering the delay of the hydraulic actuator whereby the mine detection six-legged robot can realize stable walking on irregular terrain without to make an orbit of the foot for irregular terrain. The following results were obtained. (1) As an attitude control method considering the delay of the actuator of the thigh links, we derive a mathematical model in which the inputs are the driving torque of the thigh links in the suppor...

  2. Attitude Controller for the Atmospheric Entry of the Mars Science Laboratory

    Science.gov (United States)

    Brugarolas, Paul B.; San Martin, A. Miguel; Wong, Edward C.

    2008-01-01

    This paper describes the attitude controller for the atmospheric entry of the Mars Science Laboratory (MSL). The controller will command 8 RCS thrusters to control the 3- axis attitude of the entry capsule. The Entry Controller is formulated as three independent channels in the control frame, which is nominally aligned with the stability frame. Each channel has a feedfoward and a feedback path. The feedforward path enables fast response to large bank commands. The feedback path stabilizes the vehicle angle of attack and sideslip around its trim position, and tracks bank commands. The feedback path has a PD/D control structure with deadbands that minimizes fuel usage. The performance of this design is demonstrated via computer simulations.

  3. Attitude Estimation and Position Control of VTOL UAVs using IMU and GPS Measurements

    CERN Document Server

    Roberts, Andrew

    2011-01-01

    We address two fundamental problems associated with the control of vertical take-off and landing (VTOL) unmanned airborne vehicles (UAVs): attitude estimation and position control. We propose two velocity-aided attitude observers which utilize a global-positioning system (GPS) in addition to an inertial measurement unit (IMU). The `velocity-aided' class of observer uses an accelerometer to measure the system \\emph{apparent acceleration} (instead of the gravity vector), and is therefore better suited for applications where the rigid-body (aircraft) is subjected to significant linear accelerations (which is to be expected for VTOL UAVs). We also propose a position controller which utilizes the accelerometer in a similar fashion. More precisely, rather than using the system orientation (as is usually done in the existing position controllers), we use the vector measurements (accelerometer and magnetometer measurements) directly in the position control law. Consequently, the proposed position controller does not ...

  4. THREE-AXIS AIR-BEARING BASED PLATFORM FOR SMALL SATELLITE ATTITUDE DETERMINATION AND CONTROL SIMULATION.

    Directory of Open Access Journals (Sweden)

    F. Contreras

    2005-12-01

    Full Text Available A frictionless environment simulation platform, utilized for accomplishing three-axis attitude control tests in small satellites,is introduced. It is employed to develop, improve, and carry out objective tests of sensors, actuators, and algorithms in theexperimental framework. Different sensors (i.e. sun, earth, magnetometer, and an inertial measurement unit are utilizedto assess three-axis deviations. A set of three inertial wheels is used as primary actuators for attitude control, together withthree mutually perpendicular magnetic coils intended for desaturation purposes, and as a backup control system. Accuratebalancing, through the platform’s center of mass relocation into the geometrical center of the spherical air-bearing,significatively reduces gravitational torques, generating a virtually torque-free environment. A very practical balancingprocedure was developed for equilibrating the table in the local horizontal plane, with a reduced final residual torque. Awireless monitoring system was developed for on-line and post-processing analysis; attitude data are displayed and stored,allowing properly evaluate the sensors, actuators, and algorithms. A specifically designed onboard computer and a set ofmicrocontrollers are used to carry out attitude determination and control tasks in a distributed control scheme.The main components and subsystems of the simulation platform are described in detail.

  5. TRMM Re-Entry Planning: Attitude Determination and Control During Thruster Modes

    Science.gov (United States)

    DeWeese, Keith

    2005-01-01

    The Tropical Rainfall Measuring Mission (TRMM) spacecraft has been undergoing design for a controlled re-entry to Earth. During simulation of the re-entry plan, there was evidence of errors in the attitude determination algorithms during thruster modes. These errors affected the bum efficiency, and thus planning, during re-entry. During thruster modes, the spacecraft attitude is controlled off of integrated Gyro Error Angles that were designed to closely follow the nominal spacecraft pointing frame (Tip Frame). These angles, however, were not exactly mapped to the Tip Frame from the Body Frame. Additionally, in the initial formulation of the thruster mode attitude determination algorithms, several assumptions and approximations were made to conserve processor speed. These errors became noticeable and significant when simulating bums of much longer duration (-10 times) than had been produced in flight. A solution is proposed that uses attitude determination information from a propagated extended Kalman filter that already exists in the TRMM thruster modes. This attitude information is then used to rotate the Gyro Error Angles into the Tip Frame. An error analysis is presented that compares the two formulations. The new algorithm is tested using the TRMM High-Fidelity Simulator and verified with the TRMM Software Testing and Training Facility. Simulation results for both configurations are also presented.

  6. Attitude Control of a Small Coaxial Helicopter with a Bell Type Stabilizer Bar

    Science.gov (United States)

    Sunada, Shigeru; Hirosue, Wataru; Kawashima, Kenta

    We analyzed the small coaxial helicopter recently developed for entertainment. The upper rotor is connected with a stabilizer bar alone and the lower rotor is not connected with it. The cyclic pitch of the upper rotor is controlled by this stabilizer bar, and that of the lower rotor is controlled by servo motors. We investigated how this stabilizer bar varies the cyclic pitch of the upper rotor and how it contributes to attitude control of a fuselage.

  7. Attitude control system of the Delfi-n3Xt satellite

    Science.gov (United States)

    Reijneveld, J.; Choukroun, D.

    2013-12-01

    This work is concerned with the development of the attitude control algorithms that will be implemented on board of the Delfi-n3xt nanosatellite, which is to be launched in 2013. One of the mission objectives is to demonstrate Sun pointing and three axis stabilization. The attitude control modes and the associated algorithms are described. The control authority is shared between three body-mounted magnetorquers (MTQ) and three orthogonal reaction wheels. The attitude information is retrieved from Sun vector measurements, Earth magnetic field measurements, and gyro measurements. The design of the control is achieved as a trade between simplicity and performance. Stabilization and Sun pointing are achieved via the successive application of the classical Bdot control law and a quaternion feedback control. For the purpose of Sun pointing, a simple quaternion estimation scheme is implemented based on geometric arguments, where the need for a costly optimal filtering algorithm is alleviated, and a single line of sight (LoS) measurement is required - here the Sun vector. Beyond the three-axis Sun pointing mode, spinning Sun pointing modes are also described and used as demonstration modes. The three-axis Sun pointing mode requires reaction wheels and magnetic control while the spinning control modes are implemented with magnetic control only. In addition, a simple scheme for angular rates estimation using Sun vector and Earth magnetic measurements is tested in the case of gyro failures. The various control modes performances are illustrated via extensive simulations over several orbits time spans. The simulated models of the dynamical space environment, of the attitude hardware, and the onboard controller logic are using realistic assumptions. All control modes satisfy the minimal Sun pointing requirements allowed for power generation.

  8. Bounded attitude control of rigid bodies: Real-time experimentation to a quadrotor mini-helicopter

    OpenAIRE

    Guerrero-Castellanos, Fermi; Marchand, Nicolas; Hably, Ahmad; Lesecq, Suzanne; Delamare, Jérôme

    2011-01-01

    A quaternion-based feedback is developed for the attitude stabilization of rigid bodies. The control design takes into account a priori input bounds and is based on nested saturation approach. It results in a very simple controller suitable for an embedded use with low computational resources available. The proposed method is generic not restricted to symmetric rigid bodies and does not require the knowledge of the inertia matrix of the body. The control law can be tuned to force closed-loop ...

  9. Attitude control of geostationary satellites with double gimballed momentum wheels

    Science.gov (United States)

    Schulz, G.; Lange, T.

    1981-11-01

    Conventional control methods are generalized using state vector feedback design procedures. Alternatively, a decoupled control method using a nondiagonal inertia tensor was derived. These are confronted to modern control theory design method with observer, where especially the insensitivity with respect to variants of the moments of inertia was demonstrated.

  10. Tobacco Control Policy Advocacy Attitudes and Self-Efficacy among Ethnically Diverse High School Students

    Science.gov (United States)

    Ramirez, Amelie G.; Velez, Luis F.; Chalela, Patricia; Grussendorf, Jeannie; McAlister, Alfred L.

    2006-01-01

    This study applied self-efficacy theory to assess empowerment to advocate on behalf of tobacco control policies. The Youth Tobacco Survey with added policy advocacy self-efficacy, attitudes, and outcome expectations scales was given to 9,177 high school students in Texas. Asians showed the lowest prevalence of experimentation and current smoking,…

  11. Community Involvement, Perceived Control, and Attitudes toward Aging among Lesbians and Gay Men

    Science.gov (United States)

    Hostetler, Andrew J.

    2012-01-01

    A person-environment approach was used to explore the relationship between community involvement and attitudes toward aging among middle-age and older lesbians and gay men. Specifically, this study investigated the relationships between participation in gay community activities, perceived control, and aging-related concerns among two…

  12. The Attitudes & Beliefs on Classroom Control Inventory-Revised and Revisited: A Continuation of Construct Validation

    Science.gov (United States)

    Martin, Nancy K.; Yin, Zenong; Mayall, Hayley

    2008-01-01

    The purpose of this study was to report the psychometric properties of the revised Attitudes and Beliefs of Classroom Control Inventory (ABCC-R). Data were collected from 489 participants via the ABCC-R, Teacher Efficacy Scale, Problems in School Questionnaire, and a demographic questionnaire. Results were in keeping with the construct. The…

  13. A comparison of dysfunctional attitudes in substance abusers and control group and its psychological outcome

    Directory of Open Access Journals (Sweden)

    2008-11-01

    This research was carried out to assess the role of dysfunctional attitudes, outcomes of psychology in substance abuse behaviors of subject were referred to addiction treatment center in the city of Bandar Abbas, and to compare the with the control group. Methods: This is a retrospective study in which 100 subject substance abusers were compared with 100 subject s of control group who were selected using convenience sampling and were also demographically matched. Data were gathered using a demographic questionnaire, clinical interview, dysfunctional attitudes scale (DAS, Depression Anxiety Stress Scale (DASS. The data were analyzed via descriptive statistic method, T- Test and chi-square and variance analysis. Findings: Findings indicated that in comparison with control group, subject of substance abusers had experienced more stress, anxiety, depression, had shown a cognitively more percent of them dysfunctional attitudes in comparison with control group. Results: The results suggested that the dysfunctional attitudes could be as a Vulnerability Factor that increase abuse of substance consequently use of cognitive therapy could be helpful and effective in prevention and treatment of the addicts.

  14. Using Automatic Code Generation in the Attitude Control Flight Software Engineering Process

    Science.gov (United States)

    McComas, David; O'Donnell, James R., Jr.; Andrews, Stephen F.

    1999-01-01

    This paper presents an overview of the attitude control subsystem flight software development process, identifies how the process has changed due to automatic code generation, analyzes each software development phase in detail, and concludes with a summary of our lessons learned.

  15. CHAOTIC ATTITUDE MOTION OF A MAGNETIC RIGID SPACECRAFT IN AN ELLIPTIC ORBIT AND ITS CONTROL

    Institute of Scientific and Technical Information of China (English)

    刘延柱; 陈立群

    2003-01-01

    This paper deals with the chaotic attitude motion of a magnetic rigid spacecraft with internal damping in an elliptic orbit. The dynamical model of the spacecraft is established. The Melnikov analysis is carried out to prove the existence of a complicated nonwandering Cantor set. The dynamical behaviors are numerically investigated by means of time history, Poincare map, Lyapunov exponents and power spectrum. Numerical simulations demonstrate the chaotic motion of the system.The input-output feedback linearization method and its modified version are applied, respectively, to control the chaotic attitude motions to the given fixed point or periodic motion.

  16. Adaptive Integral-type Sliding Mode Control for Spacecraft Attitude Maneuvering Under Actuator Stuck Failures

    Institute of Scientific and Technical Information of China (English)

    HU Qinglei; ZHANG Youmin; HUO Xing; XIAO Bing

    2011-01-01

    A fault tolerant control (FTC) design technique against actuator stuck faults is investigated using integral-type sliding mode control (ISMC) with application to spacecraft attitude maneuvering control system. The principle of the proposed FTC scheme is to design an integral-type sliding mode attitude controller using on-line parameter adaptive updating law to compensate for the effects of stuck actuators. This adaptive law also provides both the estimates of the system parameters and external disturbances such that a prior knowledge of the spacecraft inertia or boundedness of disturbances is not required. Moreover, by including the integral feedback term, the designed controller can not only tolerate actuator stuck faults, but also compensate the disturbances with constant components. For the synthesis of controller, the fault time, patterns and values are unknown in advance, as motivated from a practical spacecraft control application. Complete stability and performance analysis are presented and illustrative simulation results of application to a spacecraft show that high precise attitude control with zero steady-error is successfully achieved using various scenarios of stuck failures in actuators.

  17. Attitude Control of Satellite With Pulse-Width Pulse- Frequency (PWPF Modulator Using Generalized Incremental Predictive Control

    Directory of Open Access Journals (Sweden)

    Ehsan Chegeni

    2014-09-01

    Full Text Available In this paper, we use generalized incremental predictive control (GIPC to stabilize attitude of satellite. We compare Generalized Predictive Control (GPC with GIPC algorithm and present that GIPC has better performance. The three-axis attitude control systems are activated in pulse mode. Consequently, a modulation of the torque command is compelling in order to avoid high non-linear control action. This work considers the Pulse-Width Pulse-Frequency modulator (PWPF is composed of a Schmitt trigger, a first order filter, and a feedback loop. PWPF modulator has several advantages over classical bang-bang controllers such as close to linear operation, high accuracy, and reduced propellant consumption

  18. Spacecraft attitude maneuver using two single-gimbal control moment gyros

    Science.gov (United States)

    Kasai, Shinya; Kojima, Hirohisa; Satoh, Mitsunori

    2013-03-01

    In this paper, arbitrary rest-to-rest attitude maneuver problems for a satellite using two single-gimbal control moment gyros (2SGCMGs) are considered. Although single-gimbal control moment gyros are configured in the same manner as the traditional pyramid-array CMG, only two CMGs are assumed to be available. Attitude maneuver problems are similar to problems involving two reaction wheels (RWs) from the viewpoint of the number of actuators. In other words, the problem treated herein is a kind of underactuated problem. Although 2SGCMGs can generate torques around all axes, they cannot generate torques around each axis independently. Therefore, control methods designed for a satellite using two reaction wheels cannot be applied to three-axis attitude maneuver problems for a satellite using 2SGCMGs. In this paper, for simplicity, maneuvers around the x- and z-axes are first considered, and then a maneuver around the y-axis due to the corning effect resulting from the maneuver around the x- and z-axes is considered. Since maneuvers around each axis are established by the proposed method, arbitrary attitude maneuvers can be achieved using 2SGCMGs. In addition, the maneuvering angles around the z- and x-axes, which are required in order to maneuver around the y-axis, are analytically determined, and the total time required for maneuvering around the y-axis is then analyzed numerically.

  19. Delay Depending Decentralized Adaptive Attitude Synchronization Tracking Control of Spacecraft Formation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jiakang; MA Guangfu; HU Qinglei

    2012-01-01

    This paper deals with the problem of cooperative attitude tracking with time-varying communication delays as well as the delays between inter-synchronization control parts and self-tracking control parts in the spacecraft formation flying.First,we present the attitude synchronization tracking control algorithms and analyze the sufficient delay-dependent stability condition with the choice of a Lyapunov function when the angular velocity can be measured.More specifically,a class of linear filters is developed to derive an output feedback control law without having direct information of the angular velocity,which is significant for practical applications with low-cost configurations of spacecraft.Using a well-chosen Lyapunov-Krasovskii function,it is proven that the presented control law can make the spacecraft formation attitude tracking system synchronous and achieve exponential stability,in the face of model uncertainties,as well as non-uniform time-varying delays in communication links and different control parts.Finally,simulation results are presented to demonstrate the effectiveness of the proposed control schemes.

  20. Stabilization of rotational motion with application to spacecraft attitude control

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    2000-01-01

    force. It is shown that this control law makes the system uniformly asymptotically stable to the desired reference point. The concepet is very straightforward in the Euclidean space however a global rotation control cannot be tackled.An additional modification is made to address a system which flow lies...... for global stabilization of a rotary motion. Along with a model of the system formulated in the Hamilton's canonical from the algorithm uses information about a required potential energy and a dissipation term. The control action is the sum of the gradient of the potential energy and the dissipation...

  1. Stabilization of rotational motion with application to spacecraft attitude control

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    2001-01-01

    force. It is shown that this control law makes the system uniformly asymptotically stable to the desired reference point. The concepet is very straightforward in the Euclidean space however a global rotation control cannot be tackled.An additional modification is made to address a system which flow lies...... for global stabilization of a rotary motion. Along with a model of the system formulated in the Hamilton's canonical from the algorithm uses information about a required potential energy and a dissipation term. The control action is the sum of the gradient of the potential energy and the dissipation...

  2. A Comparative Study of Actuator Configurations for Satellite Attitude Control

    OpenAIRE

    Raymond Kristiansen; Olav Egeland; Per Johan Nicklasson

    2005-01-01

    In this paper a controllability study of different actuator configurations consisting of magnetic torquers, reaction wheels and a gravity boom is presented. The theoretical analysis is performed with use of controllability gramians, and simulation results with the different configurations are presented and compared regarding settling time and power consumption to substantiate the theoretical analysis. A reference model is also introduced to show how the power consumption can he lowered to the...

  3. Time-Optimal Magnetic Attitude Control for Earth-Pointing Spacecraft: Open-Loop and Continuous Optimization Approaches

    OpenAIRE

    Fullmer, Rees; Liang, Jinsong; Chen, YangQuan

    2004-01-01

    Spacecraft attitude control using only magnetic coils suffers from a slowly varying uncontrollable axis. This lack of controllability results in marginal stability, slow slew maneuvering and convergence to equilibrium positions. In this paper the open-loop time-optimal control and continuous optimization solutions for magnetic attitude control of a nadir-pointing satellite are presented. Nonlinear time-varying models with constrained inputs are considered instead of the linearized model gener...

  4. Adaptive attitude controller for a satellite based on neural network in the presence of unknown external disturbances and actuator faults

    Science.gov (United States)

    Fazlyab, Ali Reza; Fani Saberi, Farhad; Kabganian, Mansour

    2016-01-01

    In this paper, an adaptive attitude control algorithm is developed based on neural network for a satellite. The proposed attitude control is based on nonlinear modified Rodrigues parameters feedback control in the presence of unknown terms like external disturbances and actuator faults. In order to eliminate the effect of the uncertainties, a multilayer neural network with a new learning rule will be designed appropriately. In this method, asymptotic stability of the proposed algorithm has been proven in the presence of unknown terms based on Lyapunov stability theorem. Finally, the performance of the designed attitude controller is investigated by simulations.

  5. Magnetic attitude control system for dual-spin satellites

    Science.gov (United States)

    Alfriend, K. T.

    1975-01-01

    A closed-loop control law is developed for a dual-spin satellite control system which utilizes the interaction of the geomagnetic field with the satellite dipole parallel to the spin axis. The control law consists of the linear combination of the pitch axis component of the rate of change of the geomagnetic field and the product of the roll angle and roll axis component of the geomagnetic field. Application of the method of multiple time scales yields approximate solutions for the feedback gains in terms of the system parameters. Approximate solutions are also obtained for the response of the system to disturbance torques. A comparison of the approximate solutions and numerical solutions obtained by numerical integration of the exact equations of motion is then given.

  6. The combined energy and attitude control system for small satellites—Earth observation missions

    Science.gov (United States)

    Varatharajoo, Renuganth; Fasoulas, Stefanos

    2005-01-01

    Small satellites are becoming the preferred option for low-cost Earth observation missions. However, the projected requirements have increased for the missions, which require more sophisticated and additional payloads nowadays. As a result, this would most probably be cumbersome and critical for the overall satellite mass/volume budgets. In this article, the idea of combining the energy storage and attitude control systems is presented in order to reduce the number of subsystems onboard. Such a system consists of a double counterrotating flywheel unit serving simultaneously for the satellite energy and attitude management. First, numerical treatments were conducted for the rotors to determine a failure-free condition corresponding to their stresses and natural frequencies. Further, the mathematical models describing the energy and attitude control are established, and the system onboard architecture is implemented. Numerical simulations for the developed architecture were conducted taking into account the ideal and non-ideal cases. The simulation results are discussed especially from the energy and attitude standpoints. The system performance complies with the mission requirements. Thus, this end-to-end system demonstration indicates that the combined system is judiciously feasible, and is a potential combined subsystem for small satellites.

  7. Adaptive Attitude Control of the Crew Launch Vehicle

    Science.gov (United States)

    Muse, Jonathan

    2010-01-01

    An H(sub infinity)-NMA architecture for the Crew Launch Vehicle was developed in a state feedback setting. The minimal complexity adaptive law was shown to improve base line performance relative to a performance metric based on Crew Launch Vehicle design requirements for all most all of the Worst-on-Worst dispersion cases. The adaptive law was able to maintain stability for some dispersions that are unstable with the nominal control law. Due to the nature of the H(sub infinity)-NMA architecture, the augmented adaptive control signal has low bandwidth which is a great benefit for a manned launch vehicle.

  8. A Comparative Study of Actuator Configurations for Satellite Attitude Control

    Directory of Open Access Journals (Sweden)

    Raymond Kristiansen

    2005-10-01

    Full Text Available In this paper a controllability study of different actuator configurations consisting of magnetic torquers, reaction wheels and a gravity boom is presented. The theoretical analysis is performed with use of controllability gramians, and simulation results with the different configurations are presented and compared regarding settling time and power consumption to substantiate the theoretical analysis. A reference model is also introduced to show how the power consumption can he lowered to the same magnitude as when magnetic torquers are used, without degrading the satellite response significantly.

  9. A hybrid attitude controller consisting of electromagnetic torque rods and an active fluid ring

    Science.gov (United States)

    Nobari, Nona A.; Misra, Arun K.

    2014-01-01

    In this paper, a novel hybrid actuation system for satellite attitude stabilization is proposed along with its feasibility analysis. The system considered consists of two magnetic torque rods and one fluid ring to produce the control torque required in the direction in which magnetic torque rods cannot produce torque. A mathematical model of the system dynamics is derived first. Then a controller is developed to stabilize the attitude angles of a satellite equipped with the abovementioned set of actuators. The effect of failure of the fluid ring or a magnetic torque rod is examined as well. It is noted that the case of failure of the magnetic torque rod whose torque is along the pitch axis is the most critical, since the coupling between the roll or yaw motion and the pitch motion is quite weak. The simulation results show that the control system proposed is quite fault tolerant.

  10. Linear Time Varying Approach to Satellite Attitude Control Using only Electromagnetic Actuation

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    2000-01-01

    , lightweight, and power efficient actuators is therefore crucial and viable. This paper discusser linear attitude control strategies for a low earth orbit satellite actuated by a set of mutually perpendicular electromagnetic coils. The principle is to use the interaction between the Earth's magnetic field and...... the magnetic field generated by the coils. A key challenge is the fact that the mechanical torque can only be produced in a plane perpendicular to the local geomagnetic field vector, therefore the satellite is not controllable at fixed time. Avaliability of design methods for time varying systems is...... limited, nevertheless, a solution of the riccati equation gives an excellent frame for investigations provided in this paper. An observation that geomagnetic field changes approximately periodically when satellite is on a near polar orbit is used throughout this paper. Three types of attitude controllers...

  11. [Attitude and perceived control of the elderly towards the consumption of anxiolytic, sedative and hypnotic medications].

    Science.gov (United States)

    Guindon, Marilyn; Cappeliez, Philippe

    2011-03-01

    This study examines the importance of variables from the Theory of Planned Behaviour (i.e., attitudes toward behaviour, subjective norms, and perceived control) for the prediction of consumption of anxiolytic and sedative-hypnotic (ASH) medications in a sample of older persons, aged 69 years on average, 62 consumers and 92 non-consumers. A favourable attitude toward ASH and a sense of having less control regarding these drugs predict both current usage and intention to continue. Perceived control predicts intention to start consumption of ASH in current non-consumers. This study underlines the importance of considering the role of the older person's decisional power in the consumption of these medications. PMID:21470438

  12. Design of the EO-1 Pulsed Plasma Thruster Attitude Control Experiment

    Science.gov (United States)

    Zakrzwski, Charles; Sanneman, Paul; Hunt, Teresa; Blackman, Kathie; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    The Pulsed Plasma Thruster (PPT) Experiment on the Earth Observing 1 (EO-1) spacecraft has been designed to demonstrate the capability of a new generation PPT to perform spacecraft attitude control. The PPT is a small, self-contained pulsed electromagnetic Propulsion system capable of delivering high specific impulse (900-1200 s), very small impulse bits (10-1000 micro N-s) at low average power (less than 1 to 100 W). EO-1 has a single PPT that can produce torque in either the positive or negative pitch direction. For the PPT in-flight experiment, the pitch reaction wheel will be replaced by the PPT during nominal EO-1 nadir pointing. A PPT specific proportional-integral-derivative (PID) control algorithm was developed for the experiment. High fidelity simulations of the spacecraft attitude control capability using the PPT were conducted. The simulations, which showed PPT control performance within acceptable mission limits, will be used as the benchmark for on-orbit performance. The flight validation will demonstrate the ability of the PPT to provide precision pointing resolution. response and stability as an attitude control actuator.

  13. Attitude control system design using a flywheel suspended by two gimbals

    Science.gov (United States)

    Peres, R. W.; Ricci, M. C.

    2015-10-01

    This work presents the attitude control system design procedures for a three axis stabilized satellite in geostationary orbit, which contains a flywheel suspended by two gimbals. The use of a flywheel with two DOFs is an interesting option because with only one device it's possible to control the torques about vehicle's three axes; through the wheel speed control and gyrotorquing phenomenon with two DOFs. If the wheel size and speed are determined properly it's possible to cancel cyclic torques using gas jets only periodically to cancel secular disturbance torques. The system, based on a flywheel, takes only one pitch/roll (earth) sensor to maintain precise attitude, unlike mass expulsion based control systems, which uses propellants continuously, beyond roll, pitch and yaw sensors. It is considered the satellite is in nominal orbit and, therefore, that the attitude's acquisition phase has already elapsed. Control laws and system parameters are determined in order to cancel the solar pressure radiation disturbance torque and the torque due to misalignment of the thrusters. Stability is analyzed and step and cyclic responses are obtained.

  14. Robust Adaptive Geometric Tracking Controls on SO(3) with an Application to the Attitude Dynamics of a Quadrotor UAV

    CERN Document Server

    Lee, Taeyoung

    2011-01-01

    This paper provides new results for a robust adaptive tracking control of the attitude dynamics of a rigid body. Both of the attitude dynamics and the proposed control system are globally expressed on the special orthogonal group, to avoid complexities and ambiguities associated with other attitude representations such as Euler angles or quaternions. By designing an adaptive law for the inertia matrix of a rigid body, the proposed control system can asymptotically follow an attitude command without the knowledge of the inertia matrix, and it is extended to guarantee boundedness of tracking errors in the presence of unstructured disturbances. These are illustrated by numerical examples and experiments for the attitude dynamics of a quadrotor UAV.

  15. Decentralized diagnosis in a spacecraft attitude determination and control system

    OpenAIRE

    Pérez, Carlos Gustavo; Travé-Massuyès, Louise; Chanthery, Elodie; Sotomayor, Javier

    2015-01-01

    In model-based diagnosis (MBD), structural models can provide useful information for fault diagnosis and fault-tolerant control design. In particular, they are known for supporting the design of analytical redundancy relations (ARRs) which are widely used to generate residuals for diagnosis. On the other hand, systems are increasingly complex whereby it is necessary to develop decentralized architectures to perform the diagnosis task. Decentralized diagnosis is of interest for on-board system...

  16. Inertial attitude control of a bat-like morphing-wing air vehicle

    International Nuclear Information System (INIS)

    This paper presents a novel bat-like unmanned aerial vehicle inspired by the morphing-wing mechanism of bats. The goal of this paper is twofold. Firstly, a modelling framework is introduced for analysing how the robot should manoeuvre by means of changing wing morphology. This allows the definition of requirements for achieving forward and turning flight according to the kinematics of the wing modulation. Secondly, an attitude controller named backstepping+DAF is proposed. Motivated by biological evidence about the influence of wing inertia on the production of body accelerations, the attitude control law incorporates wing inertia information to produce desired roll (φ) and pitch (θ) acceleration commands (desired angular acceleration function (DAF)). This novel control approach is aimed at incrementing net body forces (Fnet) that generate propulsion. Simulations and wind-tunnel experimental results have shown an increase of about 23% in net body force production during the wingbeat cycle when the wings are modulated using the DAF as a part of the backstepping control law. Results also confirm accurate attitude tracking in spite of high external disturbances generated by aerodynamic loads at airspeeds up to 5 ms−1. (paper)

  17. Analysis of Pan-European attitudes to the eradication and control of bovine viral diarrhoea.

    Science.gov (United States)

    Heffernan, C; Misturelli, F; Nielsen, L; Gunn, G J; Yu, J

    2009-02-01

    At present, national-level policies concerning the eradication and control of bovine viral diarrhoea (BVD) differ widely across Europe. Some Scandinavian countries have enacted strong regulatory frameworks to eradicate the disease, whereas other countries have few formal policies. To examine these differences, the attitudes of stakeholders and policy makers in 17 European countries were investigated. A web-based questionnaire was sent to policy makers, government and private sector veterinarians, and representatives of farmers' organisations. In total, 131 individuals responded to the questionnaire and their responses were analysed by applying a method used in sociolinguistics: frame analysis. The results showed that the different attitudes of countries that applied compulsory or voluntary frameworks were associated with different views about the attribution or blame for BVD and the roles ascribed to farmers and other stakeholders in its eradication and control. PMID:19202168

  18. Attitudes towards smoking and tobacco control among pre-clinical medical students in Malaysia.

    Science.gov (United States)

    Tee, G H; Hairi, N N; Hairi, F

    2012-08-01

    Physicians should play a leading role in combatting smoking; information on attitudes of future physicians towards tobacco control measures in a middle-income developing country is limited. Of 310 future physicians surveyed in a medical school in Malaysia, 50% disagreed that it was a doctor's duty to advise smokers to stop smoking; 76.8% agreed that physicians should not smoke before advising others not to smoke; and 75% agreed to the ideas of restricting the sale of cigarettes to minors, making all public places smoke-free and banning advertising of tobacco-related merchandise. Future physicians had positive attitudes towards tobacco regulations but had not grasped their responsibilities in tobacco control measures. PMID:22668450

  19. Attitudes and practices adopted by hypertensive workers on the disease’s control

    OpenAIRE

    Zélia Maria de Sousa Araújo Santos; Helder Pádua Lima

    2005-01-01

    Systemic arterial hypertension (HAS) consists of a major public health problem, with a prevalence of 20 to 25% in the population above 18 years old. In the professional practice, the lack of treatment adhesion is frequently observed, being manifested not only by the medicamental treatment’s suspension or irregularity, but also by the adoption of inadequate life style. This work had the aim of identifying the attitudes and practices of hypertensive workers on the diseases’ control. The researc...

  20. Attitudes Toward Financial Control Systems in the United States and Japan†

    OpenAIRE

    Lane Daley; James Jiambalvo; Gary Sundem; Yasumasa Kondo

    1985-01-01

    Recently researchers have begun to investigate issues of differences in the use of managerial accounting tools across differing national environments. Much of this research is of the case study approach documenting actual practices for a small group of firms, or a distillation from numerous observations but using anecdotal evidence to support various conjectures.The study uses a survey of attitudes toward various aspects of budgeting and control systems to gain insight into the existence of d...

  1. Innovation Approach Based Sensor FDI in LEO Satellite Attitude Determination and Control System

    OpenAIRE

    Hajiyev, Chingiz

    2009-01-01

    Fault detection and isolation algorithms for LEO satellite attitude determination and control system using an approach for checking the statistical characteristics of EKF innovation sequence are proposed. The fault detection algorithm is based on statistic for the mathematical expectation of the spectral norm of the normalized innovation matrix of the EKF. This approach permits simultaneous real-time checking of the mathematical expectation and the variance of the innovation sequence and does...

  2. Magnetic Attitude Control for Small Satellites with Orbit-Independent Missions and Modest Pointing Constraints

    OpenAIRE

    Jensen, Scott

    2007-01-01

    As the need for small satellite missions increases, the practice of launching multiple satellites from a single launch vehicle is also likely to increase. Small satellite missions are often flexible enough that a variety of orbits will be satisfactory, which increases the possibility of coordinated, multi-satellite launches; unfortunately, various satellite subsystems may impose restrictions on the possible orbit parameters. Since magnetic attitude control algorithms are typically tuned to a ...

  3. The Attitude Control System Design for the Submillimeter Wave Astronomy Satellite

    OpenAIRE

    Clagett, Charles; Correll, Thomas; Fennell, Michael; Niles, Frederick; Untalan III, Victoriano; Chen, Roger; Daniel, Walter

    1995-01-01

    The Submillimeter Wave Astronomy Satellite (SWAS), the third Small Explorer spacecraft, has a sophisticated three-axis stellar pointing attitude, control subsystem. This mission requires slewing the satellite up to 3 degrees and settling on target within 15 seconds to a 57 arc-second accuracy once per minute. Hardware and software configuration will be briefly described. The spacecraft has many modes and submodes of increasing complexity and accuracy. These modes use a variety of routines inc...

  4. Linear Time Varying Approach to Satellite Attitude Control Using only Electromagnetic Actuation

    OpenAIRE

    Wisniewski, Rafal

    2000-01-01

    Recently small satellite missions have gained considerable interest due to low-cost launch opportunities and technological improvement of micro-electronics. Required pointing accuracy of small, inexpensive satellites is often relatively loose, within a couple of degrees. Application of cheap, lightweight, and power efficient actuators is therefore crucial and viable. This paper discusses linear attitude control strategies for a low earth orbit satellite actuated by a set of mutually perpendic...

  5. On the Elastic Vibration Model for High Length-Diameter Ratio Rocket with Attitude Control System

    Institute of Scientific and Technical Information of China (English)

    朱伯立; 杨树兴

    2003-01-01

    An elastic vibration model for high length-diameter ratio spinning rocket with attitude control system which can be used for trajectory simulation is established. The basic theory of elastic dynamics and vibration dynamics were both used to set up the elastic vibration model of rocket body. In order to study the problem more conveniently, the rocket's body was simplified to be an even beam with two free ends. The model was validated by simulation results and the test data.

  6. A computer simulation of Skylab dynamics and attitude control for performance verification and operational support

    Science.gov (United States)

    Buchanan, H.; Nixon, D.; Joyce, R.

    1974-01-01

    A simulation of the Skylab attitude and pointing control system (APCS) is outlined and discussed. Implementation is via a large hybrid computer and includes those factors affecting system momentum management, propellant consumption, and overall vehicle performance. The important features of the flight system are discussed; the mathematical models necessary for this treatment are outlined; and the decisions involved in implementation are discussed. A brief summary of the goals and capabilities of this tool is also included.

  7. Analytic investigation of the AEM-A/HCMM attitude control system performance. [Application Explorer Missions/Heat Capacity Mapping Mission

    Science.gov (United States)

    Lerner, G. M.; Huang, W.; Shuster, M. D.

    1977-01-01

    The Heat Capacity Mapping Mission (HCMM), scheduled for launch in 1978, will be three-axis stabilized relative to the earth in a 600-kilometer altitude, polar orbit. The autonomous attitude control system consists of three torquing coils and a momentum wheel driven in response to error signals computed from data received from an infrared horizon sensor and a magnetometer. This paper presents a simple model of the attitude dynamics and derives the equations that determine the stability of the system during both attitude acquisition (acquisition-mode) and mission operations (mission-mode). Modifications to the proposed mission-mode control laws which speed the system's response to transient attitude errors and reduce the steady-state attitude errors are suggested. Numerical simulations are performed to validate the results obtained with the simple model.

  8. Indirect Adaptive Attitude Control for a Ducted Fan Vertical Takeoff and Landing Microaerial Vehicle

    Directory of Open Access Journals (Sweden)

    Shouzhao Sheng

    2015-01-01

    Full Text Available The present paper addresses an attitude tracking control problem of a ducted fan microaerial vehicle. The proposed indirect adaptive controller can greatly reduce tracking error in the initial stage of the adaptive learning process by using an error compensation strategy and can achieve good capability to eliminate the adverse effect of measurement noises on the convergence of adjustable parameters. Moreover, the learning rate adaptation strategy is proposed to further minimize the adverse effect of large learning rates on the convergence of adjustable parameters. The experimental tests have illustrated the effectiveness of the proposed adaptive controller.

  9. Cassini Attitude Control Flight Software: from Development to In-Flight Operation

    Science.gov (United States)

    Brown, Jay

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Flight Software (FSW) has achieved its intended design goals by successfully guiding and controlling the Cassini-Huygens planetary mission to Saturn and its moons. This paper describes an overview of AACS FSW details from early design, development, implementation, and test to its fruition of operating and maintaining spacecraft control over an eleven year prime mission. Starting from phases of FSW development, topics expand to FSW development methodology, achievements utilizing in-flight autonomy, and summarize lessons learned during flight operations which can be useful to FSW in current and future spacecraft missions.

  10. The Implementation of Satellite Attitude Control System Software Using Object Oriented Design

    Science.gov (United States)

    Reid, W. Mark; Hansell, William; Phillips, Tom; Anderson, Mark O.; Drury, Derek

    1998-01-01

    NASA established the Small Explorer (SNMX) program in 1988 to provide frequent opportunities for highly focused and relatively inexpensive space science missions. The SMEX program has produced five satellites, three of which have been successfully launched. The remaining two spacecraft are scheduled for launch within the coming year. NASA has recently developed a prototype for the next generation Small Explorer spacecraft (SMEX-Lite). This paper describes the object-oriented design (OOD) of the SMEX-Lite Attitude Control System (ACS) software. The SMEX-Lite ACS is three-axis controlled and is capable of performing sub-arc-minute pointing. This paper first describes high level requirements governing the SMEX-Lite ACS software architecture. Next, the context in which the software resides is explained. The paper describes the principles of encapsulation, inheritance, and polymorphism with respect to the implementation of an ACS software system. This paper will also discuss the design of several ACS software components. Specifically, object-oriented designs are presented for sensor data processing, attitude determination, attitude control, and failure detection. Finally, this paper will address the establishment of the ACS Foundation Class (AFC) Library. The AFC is a large software repository, requiring a minimal amount of code modifications to produce ACS software for future projects.

  11. Predicting healthcare employees' participation in an office redesign program: Attitudes, norms and behavioral control

    Directory of Open Access Journals (Sweden)

    Lukas Carol

    2008-11-01

    Full Text Available Abstract Background The study examined the extent to which components based on a modified version of the theory of planned behavior explained employee participation in a new clinical office program designed to reduce patient waiting times in primary care clinics. Methods We regressed extent of employee participation on attitudes about the program, group norms, and perceived behavioral control along with individual and clinic characteristics using a hierarchical linear mixed model. Results Perceived group norms were one of the best predictors of employee participation. Attitudes about the program were also significant, but to a lesser degree. Behavioral control, however, was not a significant predictor. Respondents with at least one year of clinic tenure, or who were team leaders, first line supervisor, or managers had greater participation rates. Analysis at the clinic level indicated clinics with scores in the highest quartile clinic scores on group norms, attitudes, and behavioral control scores were significantly higher on levels of overall participation than clinics in the lowest quartile. Conclusion Findings suggest that establishing strong norms and values may influence employee participation in a change program in a group setting. Supervisory level was also significant with greater responsibility being associated with greater participation.

  12. Nurses' Perceptions and Attitudes Toward Use of Oral Patient-Controlled Analgesia.

    Science.gov (United States)

    Riemondy, Susan; Gonzalez, Lorie; Gosik, Kirk; Ricords, Amy; Schirm, Victoria

    2016-04-01

    Patient-controlled analgesia (PCA) administered intravenously is a generally well-accepted therapy by nurses and patients. PCA devices are now available for oral medications, allowing patients to self-administer pain pills without requesting them from the nurse. Successful introduction of new pain medication delivery devices can depend on nurses' knowledge and attitudes. The aim of this institutional review board approved project was to evaluate nurses' perceptions and attitudes toward using an oral PCA device for patients' pain. A 4-week study was designed and conducted at an academic medical center on an orthopedic unit and a women's health unit. Nurse participants received education on using the oral PCA device and were invited to complete a pre- and poststudy knowledge and attitude survey regarding pain management. Nurses and patients also completed a questionnaire about perceptions related to using the oral PCA device. Findings showed that nurses' attitudes toward using the oral PCA device were less favorable than those of patients, suggesting that nurses may require additional education for acceptance of this device. Results from 37 nurses showed improvement in overall knowledge and attitudes, from 70.8% pretest to 74.2% post-test. Although improvement was not statistically significant (p = .1637), two items showed significant improvement. Knowledge about the effectiveness of NSAIDS was 27.5% pretest compared with 60.0% post-test (p = .0028); and understanding about use of opioids in patients with a history of substance abuse was 50% pretest compared with 70% post-test (p = .0531). Helping nurses overcome the perceived barriers to use of an oral PCA device has potential implications for better pain management as well as enhanced patient satisfaction. PMID:27091584

  13. Nonlinear control of marine vehicles using only position and attitude measurements

    Energy Technology Data Exchange (ETDEWEB)

    Paulsen, Marit Johanne

    1996-12-31

    This thesis presents new results on the design and analysis of nonlinear output feedback controllers for auto pilots and dynamic positioning systems for ships and underwater vehicles. Only position and attitude measurements of the vehicle are used in the control design. The underlying idea of the work is to use certain structural properties of the equations of motion in the controller design and analysis. New controllers for regulation and tracking have been developed and the stability of the resulting closed-loop systems has been rigorously established. The results are supported by simulations. The following problems have been investigated covering design of passive controller for regulation, comparison of two auto pilots, nonlinear damping compensation for tracking, tracking control for nonlinear ships, and output tracking control with wave filtering for multivariable models of possibly unstable vehicles. 97 refs., 32 figs.

  14. Tobacco control education, attitudes and beliefs of Nigerian health profession students

    Directory of Open Access Journals (Sweden)

    Oluwatunmise Awojobi

    2012-08-01

    Full Text Available Objectives: The purpose of this study is to explore tobacco control-related education of health profession students and demonstrate variations according to course of study. Methods: This was a cross-sectional survey of 154 of third year nursing, pharmacy, medical and dental students in a tertiary institution in Lagos, Nigeria. The validated Global Health Professional Students survey questionnaire was used to collect data on recall of tobacco-related training, attitudes to tobacco control and beliefs about the role of health professionals in tobacco control. This was voluntary and anonymous. Descriptive and univariate analysis were conducted. Results: Only 11.8(n=18 of all respondents recalled being trained on all possible items of formal tobacco-related training. Pharmacy students had significantly low levels of training recall (χ[sup]2[/sup][sub](3[/sub]=9.88; p=0.02. Nursing students were reported to have the most positive attitudes to tobacco control with the highest mean score of 4.27 (95= 3.88-4.66. However, there was no significant difference in attitudes to tobacco control. Compared to other students, Nursing students were significantly less likely to believe that as health professionals they had a role in tobacco-control (χ[sup]2[/sup][sub](3[/sub] = 8.06; p=0.045. Conclusions: Many respondents believed they have a role in providing cessation interventions and that specific training should be part of the education they receive. However, fewer respondents report receiving such training. The education and training of these samples of health profession students needs to place more emphasis on their role in tobacco control if they are to effectively function as health promoting health professionals in preventing tobacco-related diseases.

  15. A study of attitude control concepts for precision-pointing non-rigid spacecraft

    Science.gov (United States)

    Likins, P. W.

    1975-01-01

    Attitude control concepts for use onboard structurally nonrigid spacecraft that must be pointed with great precision are examined. The task of determining the eigenproperties of a system of linear time-invariant equations (in terms of hybrid coordinates) representing the attitude motion of a flexible spacecraft is discussed. Literal characteristics are developed for the associated eigenvalues and eigenvectors of the system. A method is presented for determining the poles and zeros of the transfer function describing the attitude dynamics of a flexible spacecraft characterized by hybrid coordinate equations. Alterations are made to linear regulator and observer theory to accommodate modeling errors. The results show that a model error vector, which evolves from an error system, can be added to a reduced system model, estimated by an observer, and used by the control law to render the system less sensitive to uncertain magnitudes and phase relations of truncated modes and external disturbance effects. A hybrid coordinate formulation using the provided assumed mode shapes, rather than incorporating the usual finite element approach is provided.

  16. Infrared horizon sensor modeling for attitude determination and control: Analysis and mission experience

    Science.gov (United States)

    Phenneger, M. C.; Singhal, S. P.; Lee, T. H.; Stengle, T. H.

    1985-01-01

    The work performed by the Attitude Determination and Control Section at the National Aeronautics and Space Administration/Goddard Space Flight Center in analyzing and evaluating the performance of infrared horizon sensors is presented. The results of studies performed during the 1960s are reviewed; several models for generating the Earth's infrared radiance profiles are presented; and the Horizon Radiance Modeling Utility, the software used to model the horizon sensor optics and electronics processing to computer radiance-dependent attitude errors, is briefly discussed. Also provided is mission experience from 12 spaceflight missions spanning the period from 1973 to 1984 and using a variety of horizon sensing hardware. Recommendations are presented for future directions for the infrared horizon sensing technology.

  17. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    Science.gov (United States)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  18. Attitudes toward Placebo-Controlled Clinical Trials of Patients with Schizophrenia in Japan.

    Directory of Open Access Journals (Sweden)

    Norio Sugawara

    Full Text Available Although the use of placebo in clinical trials of schizophrenia patients is controversial because of medical and ethical concerns, placebo-controlled clinical trials are commonly used in the licensing of new drugs.The objective of this study was to assess the attitudes toward placebo-controlled clinical trials among patients with schizophrenia in Japan.Using a cross-sectional design, we recruited patients (n = 251 aged 47.7±13.2 (mean±SD with a DSM-IV diagnosis of schizophrenia or schizoaffective disorder who were admitted to six psychiatric hospitals from December 2013 to March 2014. We employed a 14-item questionnaire specifically developed to survey patients' attitudes toward placebo-controlled clinical trials.The results indicated that 33% of the patients would be willing to participate in a placebo-controlled clinical trial. Expectations for improvement of disease, a guarantee of hospital treatment continuation, and encouragement by family or friends were associated with the willingness to participate in such trials, whereas a belief of additional time required for medical examinations was associated with non-participation.Fewer than half of the respondents stated that they would be willing to participate in placebo-controlled clinical trials. Therefore, interpreting the results from placebo-controlled clinical trials could be negatively affected by selection bias.

  19. Mission management, planning, and cost: PULSE Attitude And Control Systems (AACS)

    Science.gov (United States)

    1990-01-01

    The Pluto unmanned long-range scientific explorer (PULSE) is a probe that will do a flyby of Pluto. It is a low weight, relatively low costing vehicle which utilizes mostly off-the-shelf hardware, but not materials or techniques that will be available after 1999. A design, fabrication, and cost analysis is presented. PULSE will be launched within the first decade of the twenty-first century. The topics include: (1) scientific instrumentation; (2) mission management, planning, and costing; (3) power and propulsion systems; (4) structural subsystem; (5) command, control, and communication; and (6) attitude and articulation control.

  20. Star Tracker Algorithms and a Low-Cost Attitude Determination and Control System for Space Missions

    OpenAIRE

    Delabie, Tjorven

    2016-01-01

    The attitude determination and control system determines and controls the orientation of the spacecraft. This system is crucial in the majority of space missions to e.g. point a camera to a star or direct an antenna to a ground station. Increasingly complex missions drive the need for higher accuracy, while the growing number of small spacecraft requires high robustness and low computational cost. This work focusses on the star tracker, a sensor that takes an image of the stars and compares i...

  1. Motion coordination for VTOL unmanned aerial vehicles attitude synchronisation and formation control

    CERN Document Server

    Abdessameud, Abdelkader

    2013-01-01

    Motion Coordination for VTOL Unmanned Aerial Vehicles develops new control design techniques for the distributed coordination of a team of autonomous unmanned aerial vehicles. In particular, it provides new control design approaches for the attitude synchronization of a formation of rigid body systems. In addition, by integrating new control design techniques with some concepts from nonlinear control theory and multi-agent systems, it presents  a new theoretical framework for the formation control of a class of under-actuated aerial vehicles capable of vertical take-off and landing. Several practical problems related to the systems’ inputs, states measurements, and  restrictions on the interconnection  topology  between the aerial vehicles in the team  are addressed. Worked examples with sufficient details and simulation results are provided to illustrate the applicability and effectiveness of the theoretical results discussed in the book. The material presented is primarily intended for researchers an...

  2. Composite control method for stabilizing spacecraft attitude in terms of Rodrigues parameters

    Institute of Scientific and Technical Information of China (English)

    Sun Haibin; Li Shihua

    2013-01-01

    In this paper,the attitude stabilization problem of a rigid spacecraft described by Rodrigues parameters is investigated via a composite control strategy,which combines a feedback control law designed by a finite time control technique with a feedforward compensator based on a linear disturbance observer (DOB) method.By choosing a suitable coordinate transformation,the spacecraft dynamics can be divided into three second-order subsystems.Each subsystem includes a certain part and an uncertain part.By using the finite time control technique,a continuous finite time controller is designed for the certain part.The uncertain part is considered to be a lumped disturbance,which is estimated by a DOB,and a corresponding feedforward design is then implemented to compensate the disturbance.Simulation results are employed to confirm the effectiveness of the proposed approach.

  3. The Software Design for the Wide-Field Infrared Explorer Attitude Control System

    Science.gov (United States)

    Anderson, Mark O.; Barnes, Kenneth C.; Melhorn, Charles M.; Phillips, Tom

    1998-01-01

    The Wide-Field Infrared Explorer (WIRE), currently scheduled for launch in September 1998, is the fifth of five spacecraft in the NASA/Goddard Small Explorer (SMEX) series. This paper presents the design of WIRE's Attitude Control System flight software (ACS FSW). WIRE is a momentum-biased, three-axis stabilized stellar pointer which provides high-accuracy pointing and autonomous acquisition for eight to ten stellar targets per orbit. WIRE's short mission life and limited cryogen supply motivate requirements for Sun and Earth avoidance constraints which are designed to prevent catastrophic instrument damage and to minimize the heat load on the cryostat. The FSW implements autonomous fault detection and handling (FDH) to enforce these instrument constraints and to perform several other checks which insure the safety of the spacecraft. The ACS FSW implements modules for sensor data processing, attitude determination, attitude control, guide star acquisition, actuator command generation, command/telemetry processing, and FDH. These software components are integrated with a hierarchical control mode managing module that dictates which software components are currently active. The lowest mode in the hierarchy is the 'safest' one, in the sense that it utilizes a minimal complement of sensors and actuators to keep the spacecraft in a stable configuration (power and pointing constraints are maintained). As higher modes in the hierarchy are achieved, the various software functions are activated by the mode manager, and an increasing level of attitude control accuracy is provided. If FDH detects a constraint violation or other anomaly, it triggers a safing transition to a lower control mode. The WIRE ACS FSW satisfies all target acquisition and pointing accuracy requirements, enforces all pointing constraints, provides the ground with a simple means for reconfiguring the system via table load, and meets all the demands of its real-time embedded environment (16 MHz Intel

  4. Improving psychology students' attitudes toward people with schizophrenia: A quasi-randomized controlled study.

    Science.gov (United States)

    Magliano, Lorenza; Rinaldi, Angela; Costanzo, Regina; De Leo, Renata; Schioppa, Giustina; Petrillo, Miriam; Read, John

    2016-01-01

    Despite scientific evidence that the majority of people with schizophrenia (PWS) have personal histories of traumatic life events and adversities, their needs for psychological support often remain unmet. Poor availability of nonpharmacological therapies in schizophrenia may be partly because of professionals' attitudes toward people diagnosed with this disorder. As future health professionals, psychology students represent a target population for efforts to increase the probability that PWS will be offered effective psychological therapies. This quasi-randomized controlled study investigated the effect of an educational intervention, addressing common prejudices via scientific evidence and prerecorded audio-testimony from PWS, on the attitudes of psychology students toward PWS. Students in their fifth year of a master's degree in Psychology at the Second University of Naples, Italy were randomly assigned to an experimental group-which attended two 3-hr sessions a week apart-or to a control group. Compared with their baseline assessment, at 1-month reassessment the 76 educated students endorsed more psychosocial causes and more of them recommended psychologists in the treatment of schizophrenia. They were also more optimistic about recovery, less convinced that PWS are recognizable and unpredictable, and more convinced that treatments, pharmacological and psychological, are useful. No significant changes were found, from baseline to 1-month reassessment, in the 112 controls. At 1-month reassessment, educated students were more optimistic about recovery and less convinced that PWS are unpredictable than controls. These findings suggest that psychology students' attitudes toward PWS can be improved by training initiatives including education and indirect contact with users. (PsycINFO Database Record PMID:26963178

  5. Body-fixed orbit-attitude hovering control over an asteroid using non-canonical Hamiltonian structure

    Science.gov (United States)

    Wang, Yue; Xu, Shijie

    2015-12-01

    The orbit-attitude hovering means that both the position and attitude of the spacecraft are kept to be stationary in the asteroid body-fixed frame. The orbit-attitude hovering is discussed in the framework of the gravitationally coupled orbit-attitude dynamics, also called the full dynamics, in which the spacecraft is modeled as a rigid body to take into account the gravitational orbit-attitude coupling naturally. A feedback hovering control law is proposed by using the non-canonical Hamiltonian structure of the problem, which is consisted of two potential shapings and one energy dissipation. The first potential shaping is to create an artificial equilibrium at the desired hovering position-attitude. Then, the second potential shaping modifies the potential further so that the artificial equilibrium is a minimum of the modified Hamiltonian on the invariant manifold. Finally, the energy dissipation leads the motion to converge asymptotically to the minimum of the modified Hamiltonian, i.e., the artificial equilibrium for hovering. The feasibility of the hovering control law is verified through numerical simulations. The proposed hovering control law has a simple form and can be implemented by the spacecraft autonomously with little computation. This feature can be attributed to the utilization of the Hamiltonian structure and natural dynamical behaviors of the system in the control law design.

  6. Electric propulsion. [pulsed plasma thruster and electron bombardment ion engine for MSAT attitude control and stationkeeping

    Science.gov (United States)

    1982-01-01

    An alternative propulsion subsystem for MSAT is presented which has a potential of reducing the satellite weight by more than 15%. The characteristics of pulsed plasma and ion engines are described and used to estimate of the mass of the propellant and thrusters for attitude control and stationkeeping functions for MSAT. Preliminary estimates indicate that the electric propulsion systems could also replace the large momentum wheels necessary to counteract the solar pressure; however, the fine pointing wheels would be retained. Estimates also show that either electric propulsion system can save approximately 18% to 20% of the initial 4,000 kg mass. The issues that require further experimentation are mentioned.

  7. Linear Time Varying Approach to Satellite Attitude Control Using only Electromagnetic Actuation

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    1997-01-01

    varying systems is limited, nevertheless, a solution of the Riccati equation gives an excellent frame for investigations provided in this paper. An observation that geomagnetic field changes approximately periodically when a satellite is on a near polar orbit is used throughout this paper. Three types of......, lightweight, and power efficient actuators is therefore crucial and viable. This paper discusses linear attitude control strategies for a low earth orbit satellite actuated by a set of mutually perpendicular electromagnetic coils. The principle is to use the interaction between the Earth's magnetic field and...

  8. Structural dynamics and attitude control study of early manned capability space station configurations

    Science.gov (United States)

    Ayers, J. Kirk; Cirillo, William M.; Giesy, Daniel P.; Hitchcock, Jay C.; Kaszubowski, Martin J.; Raney, J. Philip

    1987-01-01

    A study was performed to determine the vibration and attitude control characteristics of critical space station configurations featuring early manned capability during buildup from initial user support through the operations capability reference station. Five configurations were selected and were examined thus determining the changes that are likely to occur in the characteristics of the system as the station progresses from a single boom structure to a mature, dual keel, operations capability reference station. Both 9 foot and 5 meter truss bay sizes were investigated. All configurations analyzed were stable; however, the 5 meter truss bay size structure exhibited superior stability characteristics.

  9. Cassini Attitude Control Fault Protection Design: Launch to End of Prime Mission Performance

    Science.gov (United States)

    Meakin, Peter C.

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Fault Protection (FP) has been successfully supporting operations for over 10 years from launch through the end of the prime mission. Cassini's AACS FP is complex, containing hundreds of error monitors and thousands of tunable parameters. Since launch there have been environmental, hardware, personnel and mission event driven changes which have required AACS FP to adapt and be robust to a variety of scenarios. This paper will discuss the process of monitoring, maintaining and updating the AACS FP during Cassini's lengthy prime mission as well as provide some insight into lessons learned during tour operations.

  10. Platform for Attitude Control Experiment (PACE): An Experimental Three-Axis Stabilized CubeSat

    OpenAIRE

    Tu, Jung-Kuo; Wu, Shi-Hua; Chu, Chen-Chi

    2004-01-01

    Owing to their low cost, fast development time, and multi-discipline educational purpose, CubeSats have been widely advocated by universities in recent years. However, few have employed three-axis stabilization schemes due mainly to the limitation of power and mass. The PACE, Platform for Attitude Control Experiment for short, is a three-axis stabilizing CubeSat developed at the National Cheng Kung University. It is a 20x10x10 cm3 double cube satellite weight less than 2-kg. A miniature momen...

  11. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    Science.gov (United States)

    Woronowicz, Michael

    2011-01-01

    We have learned it is conceivable that the Neutral Mass Spectrometer on board the Lunarr Atmosphere Dust Environment Explorer (LADEE) could measure gases from surface-reflected Attitude Control System (ACS) thruster plume. At minimum altitude, the measurement would be maximized, and gravitational influence minimized ("short" time-of-flight (TOF) situation) Could use to verify aspects of thruster plume modeling Model the transient disturbance to NMS measurements due to ACS gases reflected from lunar surface Observe evolution of various model characteristics as measured by NMS Species magnitudes, TOF measurements, angular distribution, species separation effects

  12. Angular Velocity Observer on the Special Orthogonal Group for Velocity-Free Rigid-Body Attitude Tracking Control

    OpenAIRE

    Wu, Tse-Huai; Lee, Taeyoung

    2015-01-01

    This paper studies a rigid body attitude tracking control problem with attitude measurements only, when angular velocity measurements are not available. An angular velocity observer is constructed such that the estimated angular velocity is guaranteed to converge to the true angular velocity asymptotically from almost all initial estimates. As it is developed directly on the special orthogonal group, it completely avoids singularities, complexities, or discontinuities caused by minimal attitu...

  13. Farmer attitudes and livestock disease: exploring citizenship behaviour and peer monitoring across two BVD control schemes in the UK

    OpenAIRE

    Claire Heffernan; Lena Azbel-Jackson; Joe Brownlie; George Gunn

    2016-01-01

    The eradication of BVD in the UK is technically possible but appears to be socially untenable. The following study explored farmer attitudes to BVD control schemes in relation to advice networks and information sharing, shared aims and goals, motivation and benefits of membership, notions of BVD as a priority disease and attitudes toward regulation. Two concepts from the organisational management literature framed the study: citizenship behaviour where actions of individuals support the colle...

  14. Farmer attitudes and livestock disease:Exploring citizenship behaviour and peer monitoring across two BVD control schemes in the UK

    OpenAIRE

    Heffernan, Claire; Azbel-Jackson, Lena; Brownlie, Joe; Gunn, George

    2016-01-01

    The eradication of BVD in the UK is technically possible but appears to be socially untenable. The following study explored farmer attitudes to BVD control schemes in relation to advice networks and information sharing, shared aims and goals, motivation and benefits of membership, notions of BVD as a priority disease and attitudes toward regulation. Two concepts from the organisational management literature framed the study: citizenship behaviour where actions of individuals support the colle...

  15. EFFECT OF SHORT TERM YOGA PRACTICES ON COGNITIVE FUNCTION AND ATTITUDE TOWARDS VIOLENCE IN SCHOOL CHILDREN- A RANDOMIZED CONTROL STUDY

    OpenAIRE

    G. K. Reddy; Sony Kumari

    2015-01-01

    The effectiveness of short term yoga practice on cognitive function and attitude towards violence in school children (n = 100) was examined. The participants were divided into two groups -Yoga and Control group. Yoga group was given 10 days yoga intervention programme for one hour every day. Results indicated that yoga intervention contributed significant result in cognitive function and no significant result in ATV (attitude towards violence) in school children. Key words: School children, c...

  16. Farmer attitudes to vaccination and culling of badgers in controlling bovine tuberculosis.

    Science.gov (United States)

    Warren, M; Lobley, M; Winter, M

    2013-07-13

    Controversy persists in England, Wales and Northern Ireland concerning methods of controlling the transmission of bovine tuberculosis (bTB) between badgers and cattle. The National Trust, a major land-owning heritage organisation, in 2011, began a programme of vaccinating badgers against bTB on its Killerton Estate in Devon. Most of the estate is farmed by 18 tenant farmers, who thus have a strong interest in the Trust's approach, particularly as all have felt the effects of the disease. This article reports on a study of the attitudes to vaccination of badgers and to the alternative of a culling programme, using face-to-face interviews with 14 of the tenants. The results indicated first that the views of the respondents were more nuanced than the contemporary public debate about badger control would suggest. Secondly, the attitude of the interviewees to vaccination of badgers against bTB was generally one of resigned acceptance. Thirdly, most respondents would prefer a combination of an effective vaccination programme with an effective culling programme, the latter reducing population of density sufficiently (and preferably targeting the badgers most likely to be diseased) for vaccination to have a reasonable chance of success. While based on a small sample, these results will contribute to the vigorous debate concerning contrasting policy approaches to bTB control in England, Wales and Northern Ireland. PMID:23775132

  17. Improved ITOS attitude control system with Hall generator brushless motor and earth-splitting technique

    Science.gov (United States)

    Peacock, W. M.

    1971-01-01

    The ITOS with an improved attitude control system is described. A Hall generator brushless dc torque motor will replace the brush dc torque motor on ITOS-I and ITOS-A (NOAA-1). The four attitude horizon sensors will be replaced with two CO2 sensors for better horizon definition. An earth horizon splitting technique will be used to keep the earth facing side of the satellite toward earth even if the desired circular orbit is not achieved. The external appearance of the pitch control subsystem differs from TIROS-M (ITOS-1) and ITOS-A (NOAA-1) in that two instead of one pitch control electronics (PCE) boxes are used. Two instead of four horizon sensors will be used and one instead of two mirrors will be used for sensor scanning. The brushless motor will eliminate the requirement for brushes, strain gages and the telemetry for the brush wear. A single rotating flywheel, supported by a single bearing provides the gyroscopic stability and the required momentum interchange to keep one side of the satellite facing the earth. Magnetic torquing against the earth's magnetic field eliminates the requirement for expendable propellants which would limit satellite life in orbit.

  18. A spectral identification technique for adaptive attitude control and pointing of the Space Telescope

    Science.gov (United States)

    Teuber, D. L.

    1976-01-01

    The Space Telescope is a 2.4 m class aperture optical telescope having near-diffraction-limited performance. It will be placed into earth orbit by 1980 via the Space Shuttle. The problem considered is how to achieve negligible degradation of the astronomy imaging capability (to 0.005 arc second) due to smearing by pointing motions during observations. Initially, pointing instability sources were identified and a linear stability was used to assess the magnitude of elastic body modes and to design control system compensation regions necessary for subsequent adaptive control. A spectral identification technique for this adaptive attitude control and pointing has been investigated that will alleviate requirements for comprehensive dynamic ground testing. Typical all-digital simulation results describing motions of the telescope line of sight are presented.

  19. Distributed event-triggered cooperative attitude control of multiple rigid bodies with leader-follower architecture

    Science.gov (United States)

    Weng, Shengxuan; Yue, Dong

    2016-02-01

    In this note, the distributed event-triggered cooperative attitude control of multiple rigid bodies with leader-follower architecture is investigated, where both the cases of static and dynamic leaders are all considered. Two distributed triggering procedures are first introduced for the followers and leaders, and then the distributed cooperative controllers are designed under the proposed triggering schemes. Under the designed controllers with the event-triggered strategies, it is shown that the orientations of followers converge to the convex hull formed by the desired leaders' orientations with zero angular velocities. Moreover, the communication pressure in network is reduced and the energy of each agent is saved. Simulation results show the effectiveness of the proposed method.

  20. Carrier-phase GNSS Attitude Determination and Control System for Unmanned Aerial Vehicle Applications

    Directory of Open Access Journals (Sweden)

    Roberto Sabatini, Leopoldo Rodríguez, Anish Kaharkar, Celia Bartel, Tesheen Shaid

    2012-12-01

    Full Text Available This paper presents the results of a research activity performed by Cranfield University to assess the potential of carrierphase Global Navigation Satellite Systems (GNSS for attitude determination and control of small to medium size Unmanned Aerial Vehicles (UAV. Both deterministic and recursive (optimal estimation algorithms are developed for combining multiple attitude measurements obtained from different observation points (i.e., antenna locations, and their efficiencies are tested in various dynamic conditions. The proposed algorithms converge rapidly and produce the required output even during high dynamics manoeuvres. Results of theoretical performance analysis and simulation activities are presented in this paper, with emphasis on the advantages of the GNSS interferometric approach in UAV applications (i.e., low cost, high data-rate, low volume/weight, low signal processing requirements, etc.. Modelling and simulation activities focussed on the AEROSONDE UAV platform and considered the possible augmentation provided by interferometric GNSS techniques to a low-cost and low-weight/volume integrated navigation system recently developed at Cranfield University, which employs a Vision-based Navigation (VBN system, a Micro-Electro-mechanical Sensor (MEMS based Inertial Measurement Unit (IMU and code-range GNSS (i.e., GPS and GALILEO for position and velocity computations. The integrated VBN-IMU-GNSS (VIG system is augmented by using the inteferometric GNSS Attitude Determination(GAD and a comparison of the performance achievable with the VIG and VIG/GAD integrated Navigation and Guidance Systems (NGS is presented. Finally, the data provided by these NGS are used to optimise the design of an hybrid controller employing Fuzzy Logic and Proportional-Integral-Derivative (PID techniques for the AEROSONDE UAV.

  1. Racism, gun ownership and gun control: biased attitudes in US whites may influence policy decisions.

    Directory of Open Access Journals (Sweden)

    Kerry O'Brien

    Full Text Available OBJECTIVE: Racism is related to policies preferences and behaviors that adversely affect blacks and appear related to a fear of blacks (e.g., increased policing, death penalty. This study examined whether racism is also related to gun ownership and opposition to gun controls in US whites. METHOD: The most recent data from the American National Election Study, a large representative US sample, was used to test relationships between racism, gun ownership, and opposition to gun control in US whites. Explanatory variables known to be related to gun ownership and gun control opposition (i.e., age, gender, education, income, conservatism, anti-government sentiment, southern vs. other states, political identification were entered in logistic regression models, along with measures of racism, and the stereotype of blacks as violent. Outcome variables included; having a gun in the home, opposition to bans on handguns in the home, support for permits to carry concealed handguns. RESULTS: After accounting for all explanatory variables, logistic regressions found that for each 1 point increase in symbolic racism there was a 50% increase in the odds of having a gun at home. After also accounting for having a gun in the home, there was still a 28% increase in support for permits to carry concealed handguns, for each one point increase in symbolic racism. The relationship between symbolic racism and opposition to banning handguns in the home (OR1.27 CI 1.03,1.58 was reduced to non-significant after accounting for having a gun in the home (OR1.17 CI.94,1.46, which likely represents self-interest in retaining property (guns. CONCLUSIONS: Symbolic racism was related to having a gun in the home and opposition to gun control policies in US whites. The findings help explain US whites' paradoxical attitudes towards gun ownership and gun control. Such attitudes may adversely influence US gun control policy debates and decisions.

  2. Investigations of an integrated angular velocity measurement and attitude control system for spacecraft using magnetically suspended double-gimbal CMGs

    Science.gov (United States)

    Zheng, Shiqiang; Han, Bangcheng

    2013-06-01

    This paper presents an integrated angular velocity measurement and attitude control system of spacecraft using magnetically suspended double-gimbal control moment gyros (MSDGCMGs). The high speed rotor of MSDGCMG is alleviated by a five-degree-of-freedom permanent magnet biased AMB control system. With this special rotor supported manner, the MSDGCMG has the function of attitude rate sensing as well as attitude control. This characteristic provides a new approach to a compact light-weight spacecraft design, which can combine these two functions into a single device. This paper discusses the principles and implementations of AMB-based angular velocity measurement. Spacecraft dynamics with DGMSCMG actuators, including the dynamics of magnetically suspended high-speed rotor, the dynamics of inner gimbal and outer gimbal, as well as the determination method of spacecraft angular velocity are modeled, respectively. The effectiveness of the proposed integrated system is also validated numerically and experimentally.

  3. Integrated Orbit and Attitude Control for a Nanosatellite with Power Constraints

    Science.gov (United States)

    Berry, Matthew M.; Naasz, Bo J.; Kim, Hye-Young; Hall, Christopher D.

    2002-01-01

    HokieSat is a NASA Goddard sponsored spacecraft currently being built by students at Virginia Tech. HokieSat is part of the Ionospheric Observation Nanosatellite Formation (ION-F) project. The project involves spacecraft built by three schools: Virginia Tech (VT), Utah State University (USU), and University of Washington (UW). The three spacecraft are similar in design and will perform formation flying demonstrations, and make ionospheric measurements. HokieSat uses Pulsed Plasma Thrusters (PPTs) to maintain its position in the formation. There are two pairs of PPTs on HokieSat; their position on HokieSat's hexagonal cross-section is shown. Thrusters T(sub 2) and T(sub 3) provide translation control, and Thrusters TI and T4 can provide yaw steering. Any thruster can be fired individually. However because they share a capacitor, thrusters T(sub 1) and T(sub 2) or thrusters T(sub 3) and T(sub 4) cannot be fired simultaneously. Thrusters T(sub 2) T(sub 3) can be fired simultaneously, as well as thrusters T(sub 1) and T(sub 4). Each thruster provides an impulse-bit of 56 micronN-s and fires at a rate of 1 Hz. For translation control thrusters T2 and T3 are fired together providing an impulse-bit of 112 micronN-s. All four thrusters are positioned slightly above the center of mass, and therefore exert a torque on the spacecraft. Because there are no thrusters in the zenith-nadir directions, and the communication system requires that the spacecraft remain nadir-pointing, there is no way to thrust in the radial direction. The attitude of HokieSat is controlled by 3 orthogonal magnetic torque coils. Attitude control is achieved by forcing a current through the torque coils, which interacts with the Earth's magnetic field and creates a torque. Due to magnetic field interactions between the coils and PPTs, the two actuator systems cannot be used simultaneously, and any attitude or orbit control must be performed in a piecewise fashion. Power limitations place an additional

  4. Estimation of Gravitation Parameters of Saturnian Moons Using Cassini Attitude Control Flight Data

    Science.gov (United States)

    Krening, Samantha C.

    2013-01-01

    A major science objective of the Cassini mission is to study Saturnian satellites. The gravitational properties of each Saturnian moon is of interest not only to scientists but also to attitude control engineers. When the Cassini spacecraft flies close to a moon, a gravity gradient torque is exerted on the spacecraft due to the mass of the moon. The gravity gradient torque will alter the spin rates of the reaction wheels (RWA). The change of each reaction wheel's spin rate might lead to overspeed issues or operating the wheel bearings in an undesirable boundary lubrication condition. Hence, it is imperative to understand how the gravity gradient torque caused by a moon will affect the reaction wheels in order to protect the health of the hardware. The attitude control telemetry from low-altitude flybys of Saturn's moons can be used to estimate the gravitational parameter of the moon or the distance between the centers of mass of Cassini and the moon. Flight data from several low altitude flybys of three Saturnian moons, Dione, Rhea, and Enceladus, were used to estimate the gravitational parameters of these moons. Results are compared with values given in the literature.

  5. Fault tolerant attitude control for small unmanned aircraft systems equipped with an airflow sensor array

    International Nuclear Information System (INIS)

    Inspired by sensing strategies observed in birds and bats, a new attitude control concept of directly using real-time pressure and shear stresses has recently been studied. It was shown that with an array of onboard airflow sensors, small unmanned aircraft systems can promptly respond to airflow changes and improve flight performances. In this paper, a mapping function is proposed to compute aerodynamic moments from the real-time pressure and shear data in a practical and computationally tractable formulation. Since many microscale airflow sensors are embedded on the small unmanned aircraft system surface, it is highly possible that certain sensors may fail. Here, an adaptive control system is developed that is robust to sensor failure as well as other numerical mismatches in calculating real-time aerodynamic moments. The advantages of the proposed method are shown in the following simulation cases: (i) feedback pressure and wall shear data from a distributed array of 45 airflow sensors; (ii) 50% failure of the symmetrically distributed airflow sensor array; and (iii) failure of all the airflow sensors on one wing. It is shown that even if 50% of the airflow sensors have failures, the aircraft is still stable and able to track the attitude commands. (paper)

  6. Venusian atmospheric and Magellan properties from attitude control data. M.S. Thesis

    Science.gov (United States)

    Croom, Christopher A.; Tolson, Robert H.

    1994-01-01

    Results are presented of the study of the Venusian atmosphere, Magellan aerodynamic moment coefficients, moments of inertia, and solar moment coefficients. This investigation is based upon the use of attitude control data in the form of reaction wheel speeds from the Magellan spacecraft. As the spacecraft enters the upper atmosphere of Venus, measurable torques are experienced due to aerodynamic effects. Solar and gravity gradient effects also cause additional torques throughout the orbit. In order to maintain an inertially fixed attitude, the control system counteracts these torques by changing the angular rates of three reaction wheels. Model reaction wheel speeds are compared to observed Magellan reaction wheel speeds through a differential correction procedure. This method determines aerodynamic, atmospheric, solar pressure, and mass moment of inertia parameters. Atmospheric measurements include both base densities and scale heights. Atmospheric base density results confirm natural variability as measured by the standard orbital decay method. Potential inconsistencies in free molecular aerodynamic moment coefficients are identified. Moments of inertia are determined with a precision better than 1 percent of the largest principal moment of inertia.

  7. Design, dynamics and control of an Adaptive Singularity-Free Control Moment Gyroscope actuator for microspacecraft Attitude Determination and Control System

    Science.gov (United States)

    Viswanathan, Sasi Prabhakaran

    Design, dynamics, control and implementation of a novel spacecraft attitude control actuator called the "Adaptive Singularity-free Control Moment Gyroscope" (ASCMG) is presented in this dissertation. In order to construct a comprehensive attitude dynamics model of a spacecraft with internal actuators, the dynamics of a spacecraft with an ASCMG, is obtained in the framework of geometric mechanics using the principles of variational mechanics. The resulting dynamics is general and complete model, as it relaxes the simplifying assumptions made in prior literature on Control Moment Gyroscopes (CMGs) and it also addresses the adaptive parameters in the dynamics formulation. The simplifying assumptions include perfect axisymmetry of the rotor and gimbal structures, perfect alignment of the centers of mass of the gimbal and the rotor etc. These set of simplifying assumptions imposed on the design and dynamics of CMGs leads to adverse effects on their performance and results in high manufacturing cost. The dynamics so obtained shows the complex nonlinear coupling between the internal degrees of freedom associated with an ASCMG and the spacecraft bus's attitude motion. By default, the general ASCMG cluster can function as a Variable Speed Control Moment Gyroscope, and reduced to function in CMG mode by spinning the rotor at constant speed, and it is shown that even when operated in CMG mode, the cluster can be free from kinematic singularities. This dynamics model is then extended to include the effects of multiple ASCMGs placed in the spacecraft bus, and sufficient conditions for non-singular ASCMG cluster configurations are obtained to operate the cluster both in VSCMG and CMG modes. The general dynamics model of the ASCMG is then reduced to that of conventional VSCMGs and CMGs by imposing the standard set of simplifying assumptions used in prior literature. The adverse effects of the simplifying assumptions that lead to the complexities in conventional CMG design, and

  8. Analysis of state-of-the-art single-thruster attitude control techniques for spinning penetrator

    Science.gov (United States)

    Raus, Robin; Gao, Yang; Wu, Yunhua; Watt, Mark

    2012-07-01

    The attitude dynamics and manoeuvre survey in this paper is performed for a mission scenario involving a penetrator-type spacecraft: an axisymmetric prolate spacecraft spinning around its minor axis of inertia performing a 90° spin axis reorientation manoeuvre. In contrast to most existing spacecraft only one attitude control thruster is available, providing a control torque perpendicular to the spin axis. Having only one attitude thruster on a spinning spacecraft could be preferred for spacecraft simplicity (lower mass, lower power consumption etc.), or it could be imposed in the context of redundancy/contingency operations. This constraint does yield restrictions on the thruster timings, depending on the ratio of minor to major moments of inertia among other parameters. The Japanese Lunar-A penetrator spacecraft proposal is a good example of such a single-thruster spin-stabilised prolate spacecraft. The attitude dynamics of a spinning rigid body are first investigated analytically, then expanded for the specific case of a prolate and axisymmetric rigid body and finally a cursory exploration of non-rigid body dynamics is made. Next two well-known techniques for manoeuvring a spin-stabilised spacecraft, the Half-cone/Multiple Half-cone and the Rhumb line slew, are compared with two new techniques, the Sector-Arc Slew developed by Astrium Satellites and the Dual-cone developed at Surrey Space Centre. Each technique is introduced and characterised by means of simulation results and illustrations based on the penetrator mission scenario and a brief robustness analysis is performed against errors in moments of inertia and spin rate. Also, the relative benefits of each slew algorithm are discussed in terms of slew accuracy, energy (propellant) efficiency and time efficiency. For example, a sequence of half-cone manoeuvres (a Multi-half-cone manoeuvre) tends to be more energy-efficient than one half-cone for the same final slew angle, but more time-consuming. As another

  9. Cassini Spacecraft In-Flight Swap to Backup Attitude Control Thrusters

    Science.gov (United States)

    Bates, David M.

    2010-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 and arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. In order to meet the challenging attitude control and navigation requirements of the orbit profile at Saturn, Cassini is equipped with a monopropellant thruster based Reaction Control System (RCS), a bipropellant Main Engine Assembly (MEA) and a Reaction Wheel Assembly (RWA). In 2008, after 11 years of reliable service, several RCS thrusters began to show signs of end of life degradation, which led the operations team to successfully perform the swap to the backup RCS system, the details and challenges of which are described in this paper. With some modifications, it is hoped that similar techniques and design strategies could be used to benefit other spacecraft.

  10. Magnetic Attitude Control System for a Small Satellite. Impact on the Thermal Performance

    OpenAIRE

    Farrahi, Assal

    2015-01-01

    El principal objetivo de la tesis es estudiar el acoplamiento entre los subsistemas de control de actitud y de control térmico de un pequeño satélite, con el fin de buscar la solución a los problemas relacionados con la determinación de los parámetros de diseño. Se considera la evolución de la actitud y de las temperaturas del satélite bajo la influencia de dos estrategias de orientación diferentes: 1) estabilización magnética pasiva de la orientación (PMAS, passive magnetic attitude stabiliz...

  11. Optimality of incompletely measurable active and passive attitude control systems. [for satellites

    Science.gov (United States)

    Schiehlen, W.; Popp, K.

    1973-01-01

    Passive attitude control systems and active systems with incomplete state measurements are only suboptimal systems in the sense of optimal control theory, since optimal systems require complete state measurements or state estimations. An optimal system, then, requires additional hardware (especially in the case of flexible spacecraft) which results in higher costs. Therefore, it is a real engineering problem to determine how much an optimal system exceeds the suboptimal system, or in other words, what is the suboptimal system's degree of optimality. The problem will be treated in three steps: (1) definition of the degree of optimality for linear, time-invariant systems; (2) a computation method using the quadratic cost functional; (3) application to a gravity-gradient stabilized three-body satellite and a spinning flexible satellite.

  12. Development of helicopter attitude axes controlled hover flight without pilot assistance and vehicle crashes

    Science.gov (United States)

    Simon, Miguel

    In this work, we show how to computerize a helicopter to fly attitude axes controlled hover flight without the assistance of a pilot and without ever crashing. We start by developing a helicopter research test bed system including all hardware, software, and means for testing and training the helicopter to fly by computer. We select a Remote Controlled helicopter with a 5 ft. diameter rotor and 2.2 hp engine. We equip the helicopter with a payload of sensors, computers, navigation and telemetry equipment, and batteries. We develop a differential GPS system with cm accuracy and a ground computerized navigation system for six degrees of freedom (6-DoF) free flight while tracking navigation commands. We design feedback control loops with yet-to-be-determined gains for the five control "knobs" available to a flying radio-controlled (RC) miniature helicopter: engine throttle, main rotor collective pitch, longitudinal cyclic pitch, lateral cyclic pitch, and tail rotor collective pitch. We develop helicopter flight equations using fundamental dynamics, helicopter momentum theory and blade element theory. The helicopter flight equations include helicopter rotor equations of motions, helicopter rotor forces and moments, helicopter trim equations, helicopter stability derivatives, and a coupled fuselage-rotor helicopter 6-DoF model. The helicopter simulation also includes helicopter engine control equations, a helicopter aerodynamic model, and finally helicopter stability and control equations. The derivation of a set of non-linear equations of motion for the main rotor is a contribution of this thesis work. We design and build two special test stands for training and testing the helicopter to fly attitude axes controlled hover flight, starting with one axis at a time and progressing to multiple axes. The first test stand is built for teaching and testing controlled flight of elevation and yaw (i.e., directional control). The second test stand is built for teaching and

  13. Electrospray Thrusters for Attitude Control of a 1-U CubeSat

    Science.gov (United States)

    Timilsina, Navin

    With a rapid increase in the interest in use of nanosatellites in the past decade, finding a precise and low-power-consuming attitude control system for these satellites has been a real challenge. In this thesis, it is intended to design and test an electrospray thruster system that could perform the attitude control of a 1-unit CubeSat. Firstly, an experimental setup is built to calculate the conductivity of different liquids that could be used as propellants for the CubeSat. Secondly, a Time-Of-Flight experiment is performed to find out the thrust and specific impulse given by these liquids and hence selecting the optimum propellant. On the other hand, a colloidal thruster system for a 1-U CubeSat is designed in Solidworks and fabricated using Lathe and CNC Milling Machine. Afterwards, passive propellant feeding is tested in this thruster system. Finally, the electronic circuit and wireless control system necessary to remotely control the CubeSat is designed and the final testing is performed. Among the propellants studied, Ethyl ammonium nitrate (EAN) was selected as the best propellant for the CubeSat. Theoretical design and fabrication of the thruster system was performed successfully and so was the passive propellant feeding test. The satellite was assembled for the final experiment but unfortunately the microcontroller broke down during the first test and no promising results were found out. However, after proving that one thruster works with passive feeding, it could be said that the ACS testing would have worked if we had performed vacuum compatibility tests for other components beforehand.

  14. Knowledge, Attitude, Practice, and Status of Infection Control among Iranian Dentists and Dental Students: A Systematic Review

    Science.gov (United States)

    Moradi Khanghahi, Behnam; Jamali, Zahra; Pournaghi Azar, Fatemeh; Naghavi Behzad, Mohammad; Azami-Aghdash, Saber

    2013-01-01

    Background and aims Infection control is an important issue in dentistry, and the dentists are primarily responsible for observing the relevant procedures. Therefore, the present study evaluated knowledge, attitude, practice, and status of infection control among Iranian dentists through systematic review of published results. Materials and methods In this systematic review, the required data was collected searching for keywords including infection, infection control, behavior, performance, practice, attitude, knowledge, dent*, prevention, Iran* and their Persian equivalents in PubMed, Science Direct, Iranmedex, SID, Medlib, and Magiran databases with a time limit of 1985 to 2012. Out of 698 articles, 15 completely related articles were finally considered and the rest were excluded due to lake of relev-ance to the study goals. The required data were extracted and summarized in an Extraction Table and were analyzed ma-nually. Results Evaluating the results of studies indicated inappropriate knowledge, attitude, and practice regarding infection control among Iranian dentists and dental students. Using personal protection devices and observing measures required for infection control were not in accordance with global standards. Conclusion The knowledge, attitudes, and practice of infection control in Iranian dental settings were found to be inadequate. Therefore, dentists should be educated more on the subject and special programs should be in place to monitor the dental settings for observing infection control standards. PMID:23875081

  15. Roles of superconducting magnetic bearings and active magnetic bearings in attitude control and energy storage flywheel

    International Nuclear Information System (INIS)

    Compared with conventional energy storage flywheel, the rotor of attitude control and energy storage flywheel (ACESF) used in space not only has high speed, but also is required to have precise and stable direction. For the presented superconducting magnetic bearing (SMB) and active magnetic bearing (AMB) suspended ACESF, the rotor model including gyroscopic couples is established originally by taking the properties of SMB and AMB into account, the forces of SMB and AMB are simplified by linearization within their own neighbors of equilibrium points. For the high-speed rigid discal rotor with large inertia, the negative effect of gyroscopic effect of rotor is prominent, the radial translation and tilting movement of rotor suspended by only SMB, SMB with equivalent PMB, or SMB together with PD controlled AMB are researched individually. These analysis results proved originally that SMB together with AMB can make the rotor be stable and make the radial amplitude of the vibration of rotor be small while the translation of rotor suspended by only SMB or SMB and PM is not stable and the amplitude of this vibration is large. For the stability of the high-speed rotor in superconducting ACESF, the AMB can suppress the nutation and precession of rotor effectively by cross-feedback control based on the separated PD type control or by other modern control methods.

  16. Attitude Dynamics and Tracking Control of Spacecraft in the Presence of Gravity Oblateness Perturbations

    Directory of Open Access Journals (Sweden)

    Achim IONITA

    2016-03-01

    Full Text Available The orbital docking represents a problem of great importance in aerospace engineering. The paper aims to perform an analysis of docking maneuvers between a chaser vehicle and a target vehicle in permanent LEO (low earth orbit. The work begins with a study of the attitude dynamics modeling intended to define the strategy that facilitates the chaser movement toward a docking part of the target. An LQR (linear quadratic regulator approach presents an optimal control design that provides linearized closed-loop error dynamics for tracking a desired quaternion. The control law formulation is combined with the control architecture based on SDRE (State Dependent Riccati equation technique for rotational maneuvers, including the Earth oblateness perturbation. The chaser body-fixed frame must coincide with the target body-fixed frame at the docking moment. Then the implementation of the control architecture based on LQR technique using the computational tool MATLAB is carried out. In simulation of the docking strategy V-R bar operations are analyzed and the minimum accelerations needs the control of chaser vehicle. The simulation analysis of those maneuvers considered for a chaser vehicle and a target vehicle in LEO orbit is validated in a case study.

  17. Attitude and orbit control of small satellites for autonomous terrestrial target tracking

    Science.gov (United States)

    Ibrahim, Najmus S.

    Terrestrial target tracking using low Earth orbit satellites provides essential daily services and vital scientific data. In this thesis, the Attitude and Orbit Control System of such a terrestrial tracking satellite, Nanosatellite for Earth Monitoring and Observation Aerosol Monitor, is presented in detail. The satellite is a new generation Earth observation mission with the objective of detecting global atmospheric aerosol content through sub-degree pointing. The design is presented from initial hardware selection and budget development to operation definition and mission operation. The efficacy of performing precise autonomous Earth-pointing on a small satellite platform is validated through high fidelity simulations involving satellite and environmental dynamics, test-characterized hardware models and flight software-in-the-loop. The results provide practical target tracking methodologies which in the past have been publicly inaccessible to the author's best knowledge and which can be now be applied to a broad range of precise Earth-pointing satellites.

  18. Attitude control of a space platform/manipulator system using internal motion

    Science.gov (United States)

    Fernandes, Chris; Gurvits, Leonid; Li, Zexiang

    1994-08-01

    Attitude control of a space platform/manipulator system, using internal motion, is an example of a nonholonomic motion planning (NMP) problem arising from symmetry and conservation laws. Common to NMP problems are that an admissible configuration space path is constrained to a given nonholonomic distribution. We formulate the dynamic equations of a system consisting of a 3-DOF PUMA-like manipulator attached to a space platform (e.g., a space station or a satellite) as an NMP problem and discuss the cotrollability of the system. Then we describe the application of a simple algorithm for obtaining approximate optimal solutions. We conclude with a description of simulation software implementing the algorithm and simulation results for two experiments.

  19. Space Satellite Dynamics with Applications to Sunlight Pressure Attitude Control. Ph.D. Thesis

    Science.gov (United States)

    Stuck, B. W.

    1972-01-01

    A research program into three aspects of space satellite dynamics was carried out. First, a four-dimensional space-time formulation of Newtonian mechanics is developed. This theory allows a new physical interpretation of the conservation theorems of mechanics first derived rigorously by Noether. Second, a new concept for estimating the three angles which specify the orientation in space of a rigid body is presented. Two separate methods for implementing this concept are discussed, one based on direction cosines, the other on quaternions. Two examples are discussed: constant orientation in space, and constant rate of change of the three angles with time. Third, two synchronous equatorial orbit communication satellite designs which use sunlight pressure to control their attitude are analyzed. Each design is equipped with large reflecting surfaces, called solar sails, which can be canted in different directions to generate torques to correct pointing errors.

  20. Spacecraft attitude control systems with dynamic methods and structures for processing star tracker signals

    Science.gov (United States)

    Liu, Yong (Inventor); Wu, Yeong-Wei Andy (Inventor); Li, Rongsheng (Inventor)

    2001-01-01

    Methods are provided for dynamically processing successively-generated star tracker data frames and associated valid flags to generate processed star tracker signals that have reduced noise and a probability greater than a selected probability P.sub.slctd of being valid. These methods maintain accurate spacecraft attitude control in the presence of spurious inputs (e.g., impinging protons) that corrupt collected charges in spacecraft star trackers. The methods of the invention enhance the probability of generating valid star tracker signals because they respond to a current frame probability P.sub.frm by dynamically selecting the largest valid frame combination whose combination probability P.sub.cmb satisfies a selected probability P.sub.slctd. Noise is thus reduced while the probability of finding a valid frame combination is enhanced. Spacecraft structures are also provided for practicing the methods of the invention.

  1. Cassini Attitude Control Operations - Guidelines Levied on Science to Extend Reaction Wheel Life

    Science.gov (United States)

    Mittelsteadt, Carson O.

    2011-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. Cassini deployed the European-built Huygens probe, which descended through the Titan atmosphere (Saturn's largest moon) and landed on its surface on January 14, 2005. The Cassini mission has recently been approved by NASA to continue through September of 2017. This 7-year extension is called the Solstice mission and it presents challenges to the spacecraft operations team and its ability to maintain the health of the spacecraft. To keep the spacecraft healthy for 7 more years, the spacecraft team must carefully manage hydrazine use (about 48% of the 132 kg launch load remains as of January 2011). A vital part of conserving hydrazine is to use the reaction wheel assembly (RWA) control system for precise pointing and slews wherever possible. In any given week, the Cassini spacecraft is commanded to use RWA control about 99% of the time, with about 1% of the time requiring reaction control system (RCS) thruster control (to perform Delta V course corrections or to bias the RWA momentum). Such extensive use of the RWA hardware throughout the mission requires that the RWAs be operated in a way that minimizes degradation in the RWA electronics, DC motor, and spin bearing for each reaction wheel. Three consumables in particular have been identified for the RWAs: (1) Total number of revolutions for each RWA. (2) Time spent at very low wheel speeds. At these low speeds, good elasto-hydrodynamic (EHD) film lubrication may be compromised. (3) Total number of on/off power cycles. The second of these consumables, minimizing the time spent at very low wheel speeds, is especially important to keep the spin bearing healthy and well-lubricated. These consumables are actively managed by the attitude control operations team throughout the mission. One vital management

  2. Knowledge, Attitude, Practice, and Status of Infection Control among Iranian Dentists and Dental Students: A Systematic Review

    OpenAIRE

    Moradi Khanghahi, Behnam; Jamali, Zahra; Pournaghi Azar, Fatemeh; Naghavi Behzad, Mohammad; Azami-Aghdash, Saber

    2013-01-01

    Background and aims Infection control is an important issue in dentistry, and the dentists are primarily responsible for observing the relevant procedures. Therefore, the present study evaluated knowledge, attitude, practice, and status of infection control among Iranian dentists through systematic review of published results. Materials and methods In this systematic review, the required data was collected searching for keywords including infection, infection control, behavior, performance, p...

  3. Docking Offset Between the Space Shuttle and the International Space Station and Resulting Impacts to the Transfer of Attitude Reference and Control

    Science.gov (United States)

    Helms, W. Jason; Pohlkamp, Kara M.

    2011-01-01

    The Space Shuttle does not dock at an exact 90 degrees to the International Space Station (ISS) x-body axis. This offset from 90 degrees, along with error sources within their respective attitude knowledge, causes the two vehicles to never completely agree on their attitude, even though they operate as a single, mated stack while docked. The docking offset can be measured in flight when both vehicles have good attitude reference and is a critical component in calculations to transfer attitude reference from one vehicle to another. This paper will describe how the docking offset and attitude reference errors between both vehicles are measured and how this information would be used to recover Shuttle attitude reference from ISS in the event of multiple failures. During STS-117, ISS on-board Guidance, Navigation and Control (GNC) computers began having problems and after several continuous restarts, the systems failed. The failure took the ability for ISS to maintain attitude knowledge. This paper will also demonstrate how with knowledge of the docking offset, the contingency procedure to recover Shuttle attitude reference from ISS was reversed in order to provide ISS an attitude reference from Shuttle. Finally, this paper will show how knowledge of the docking offset can be used to speed up attitude control handovers from Shuttle to ISS momentum management. By taking into account the docking offset, Shuttle can be commanded to hold a more precise attitude which better agrees with the ISS commanded attitude such that start up transients with the ISS momentum management controllers are reduced. By reducing start-up transients, attitude control can be transferred from Shuttle to ISS without the use of ISS thrusters saving precious on-board propellant, crew time and minimizing loads placed upon the mated stack.

  4. A Confirmatory Factor Analysis of Preservice Teachers' Responses to the Attitudes and Beliefs on Classroom Control Inventory.

    Science.gov (United States)

    Henson, Robin K.; Roberts, J. Kyle

    This study examined the factorial invariance of scores from the Attitudes and Beliefs on Classroom Control Inventory (ABCC) (Martin and others, 1998) for 243 undergraduate preservice teachers. Although the original ABCC was developed with inservice teachers, use of the instrument to study the classroom beliefs of preservice teachers had not been…

  5. Predicting Participation in Group Parenting Education in an Australian Sample: The Role of Attitudes, Norms, and Control Factors

    Science.gov (United States)

    White, Katherine M.; Wellington, Larne

    2009-01-01

    We examined the theory of planned behavior (TPB) in predicting intentions to participate in group parenting education. One hundred and seventy-six parents (138 mothers and 38 fathers) with a child under 12 years completed TPB items assessing attitude, subjective norms, perceived behavioral control (PBC), and two additional social influence…

  6. Relations of Children's Effortful Control and Teacher-Child Relationship Quality to School Attitudes in a Low-Income Sample

    Science.gov (United States)

    Silva, Kassondra M.; Spinrad, Tracy L.; Eisenberg, Nancy; Sulik, Michael J.; Valiente, Carlos; Huerta, Snjezana; Edwards, Alison; Eggum, Natalie D.; Kupfer, Anne S.; Lonigan, Christopher J.; Phillips, Beth M.; Wilson, Shauna B.; Clancy-Menchetti, Jeanine; Landry, Susan H.; Swank, Paul R.; Assel, Michael A.; Taylor, Heather B.

    2011-01-01

    Research Findings: The purpose of this study was to examine the relations of children's effortful control and quality of relationships with teachers to school attitudes longitudinally in an ethnically diverse and economically disadvantaged sample. Data were collected as part of a larger intervention project during mid-fall, winter, and late spring…

  7. Knowledge and attitude towards the health effects of tobacco and measures of tobacco control

    Directory of Open Access Journals (Sweden)

    Shrestha Mohan

    2014-10-01

    Full Text Available Background: Tobacco is a major public health threat the world has ever faced. It is a risk factor for six of the eight leading causes of death in the world. Without the effective implementation of tobacco regulation policy, the risk itself cannot be minimized. The aim of this study is to provide the adolescents knowledge of the health effects of active and passive smoking, and knowledge and attitudes towards tobacco control measures. Materials and Methods: A descriptive type of study was conducted in December 2013 in one of the government school of Palpa district, one of the rural areas of the Western region. Data entry and analysis was done using SPSS 17 version. Microsoft Excel 2007 is also used for the data processing. Results: There is substantial support for the government taking measure towards tobacco control (96%. Furthermore, strong supports are there regarding ban of smoking in public places and public transport (95% followed by increasing price of tobacco products (87%, banning sales of tobacco to and by minors (82% and ban of tobacco advertising, promotion and sponsorship (73%. Conclusion: The study focuses the effective implementation of the Tobacco Control and Regulation Act 2011, Nepal and health education should be provided to the adolescents with the facts and skills that will enable them to protect themselves from the harmful effects of tobacco related exposure.

  8. Satellite Attitude Control System Design Taking into Account the Fuel Slosh and Flexible Dynamics

    Directory of Open Access Journals (Sweden)

    Alain G. de Souza

    2014-01-01

    Full Text Available The design of the spacecraft Attitude Control System (ACS becomes more complex when the spacecraft has different type of components like, flexible solar panels, antennas, mechanical manipulators and tanks with fuel. The interaction between the fuel slosh motion, the panel’s flexible motion and the satellite rigid motion during translational and/or rotational manoeuvre can change the spacecraft center of mass position damaging the ACS pointing accuracy. This type of problem can be considered as a Fluid-Structure Interaction (FSI where some movable or deformable structure interacts with an internal fluid. This paper develops a mathematical model for a rigid-flexible satellite with tank with fuel. The slosh dynamics is modelled using a common pendulum model and it is considered to be unactuated. The control inputs are defined by a transverse body fixed force and a moment about the centre of mass. A comparative investigation designing the satellite ACS by the Linear Quadratic Regulator (LQR and Linear Quadratic Gaussian (LQG methods is done. One has obtained a significant improvement in the satellite ACS performance and robustness of what has been done previously, since it controls the rigid-flexible satellite and the fuel slosh motion, simultaneously.

  9. A Control Moment Gyro for Dynamic Attitude Control of Small Satellites

    OpenAIRE

    Clark, Craig; Worrall, Kevin; Yavuzoğlu, Emre

    2010-01-01

    Control Moment Gyroscopes (CMGs) are not often considered for use on small satellites and, as a result few small satellite missions have implemented CMGs as on-board actuators. There are many reasons for this, but mainly this is due the complexity of the mechanical and control system needed to implement an effective CMG, and also because off-the-shelf CMG systems are generally made for the larger satellite market. .CMGs offer many advantages over reaction wheel systems. When used on a small s...

  10. Changes in Eating Attitudes, Body Esteem and Weight Control Behaviours during Adolescence in a South African Cohort

    OpenAIRE

    Gitau, Tabither M.; Micklesfield, Lisa K.; PETTIFOR, John M; Norris, Shane A.

    2014-01-01

    Failure to consume an adequate diet or over consumption during adolescence can disrupt normal growth and development, resulting in undesirable weight change. This leads to an increase in unhealthy weight control practices related to eating and exercise among both adolescent girls and boys to meet the societal ‘ideal’ body shape. This study therefore aims to examine the longitudinal changes in eating attitudes, body-esteem and weight control behaviours among adolescents between 13 and 17 years...

  11. Changes in Eating Attitudes, Body Esteem and Weight Control Behaviours during Adolescence in a South African Cohort

    OpenAIRE

    Tabither M Gitau; Micklesfield, Lisa K.; Pettifor, John. M.; Norris, Shane A

    2014-01-01

    Failure to consume an adequate diet or over consumption during adolescence can disrupt normal growth and development, resulting in undesirable weight change. This leads to an increase in unhealthy weight control practices related to eating and exercise among both adolescent girls and boys to meet the societal 'ideal' body shape. This study therefore aims to examine the longitudinal changes in eating attitudes, body-esteem and weight control behaviours among adolescents between 13 and 17 years...

  12. A Near-Hover Adaptive Attitude Control Strategy of a Ducted Fan Micro Aerial Vehicle with Actuator Dynamics

    OpenAIRE

    Shouzhao Sheng; Chenwu Sun

    2015-01-01

    The aerodynamic parameters of ducted fan micro aerial vehicles (MAVs) are difficult and expensive to precisely measure and are, therefore, not available in most cases. Furthermore, the actuator dynamics with risks of potentially destabilizing the overall system are important but often neglected consideration factors in the control system design of ducted fan MAVs. This paper presents a near-hover adaptive attitude control strategy of a prototype ducted fan MAV with actuator dynamics and witho...

  13. Integrated Orbit, Attitude, and Structural Control System Design for Space Solar Power Satellites

    Science.gov (United States)

    Woods-Vedeler, Jessica (Technical Monitor); Moore, Chris (Technical Monitor); Wie, Bong; Roithmayr, Carlos

    2001-01-01

    The major objective of this study is to develop an integrated orbit, attitude, and structural control system architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control system architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an o.set of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

  14. Integrated Orbit, Attitude, and Structural Control Systems Design for Space Solar Power Satellites

    Science.gov (United States)

    Wie, Bong; Roithmayr, Carlos M.

    2001-01-01

    The major objective of this study is to develop an integrated orbit, attitude, and structural control systems architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 x 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control systems architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an offset of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

  15. CONTROLE MULTI-AGENTS D’ATTITUDE D’UN SATELLITE PAR GYROSCOPES

    OpenAIRE

    BRAHAMI, Mustapha Anwar

    2013-01-01

    Ce mémoire de magistère porte sur le contrôle d’attitude des micro-satellites. Après avoir montré l’importance et la nécessité du contrôle d’attitude ainsi que les différents dispositifs utilisées pour la détermination et la commande d’attitude, nous présenterons les notions et les outils mathématiques essentiels à la modélisation d’attitude d’un micro-satellite. La seconde partie concerne la simulation d’attitude du premier satellite Algérien Alsat-1, il s’agira dans un pre...

  16. Simulation of Attitude and Trajectory Dynamics and Control of Multiple Spacecraft

    Science.gov (United States)

    Stoneking, Eric T.

    2009-01-01

    Agora software is a simulation of spacecraft attitude and orbit dynamics. It supports spacecraft models composed of multiple rigid bodies or flexible structural models. Agora simulates multiple spacecraft simultaneously, supporting rendezvous, proximity operations, and precision formation flying studies. The Agora environment includes ephemerides for all planets and major moons in the solar system, supporting design studies for deep space as well as geocentric missions. The environment also contains standard models for gravity, atmospheric density, and magnetic fields. Disturbance force and torque models include aerodynamic, gravity-gradient, solar radiation pressure, and third-body gravitation. In addition to the dynamic and environmental models, Agora supports geometrical visualization through an OpenGL interface. Prototype models are provided for common sensors, actuators, and control laws. A clean interface accommodates linking in actual flight code in place of the prototype control laws. The same simulation may be used for rapid feasibility studies, and then used for flight software validation as the design matures. Agora is open-source and portable across computing platforms, making it customizable and extensible. It is written to support the entire GNC (guidance, navigation, and control) design cycle, from rapid prototyping and design analysis, to high-fidelity flight code verification. As a top-down design, Agora is intended to accommodate a large range of missions, anywhere in the solar system. Both two-body and three-body flight regimes are supported, as well as seamless transition between them. Multiple spacecraft may be simultaneously simulated, enabling simulation of rendezvous scenarios, as well as formation flying. Built-in reference frames and orbit perturbation dynamics provide accurate modeling of precision formation control.

  17. Full quaternion based finite-time cascade attitude control approach via pulse modulation synthesis for a spacecraft.

    Science.gov (United States)

    Mazinan, A H; Pasand, M; Soltani, B

    2015-09-01

    In the aspect of further development of investigations in the area of spacecraft modeling and analysis of the control scheme, a new hybrid finite-time robust three-axis cascade attitude control approach is proposed via pulse modulation synthesis. The full quaternion based control approach proposed here is organized in association with both the inner and the outer closed loops. It is shown that the inner closed loop, which consists of the sliding mode finite-time control approach, the pulse width pulse frequency modulator, the control allocation and finally the dynamics of the spacecraft is realized to track the three-axis referenced commands of the angular velocities. The pulse width pulse frequency modulators are in fact employed in the inner closed loop to accommodate the control signals to a number of on-off thrusters, while the control allocation algorithm provides the commanded firing times for the reaction control thrusters in the overactuated spacecraft. Hereinafter, the outer closed loop, which consists of the proportional linear control approach and the kinematics of the spacecraft is correspondingly designed to deal with the attitude angles that are presented by quaternion vector. It should be noted that the main motivation of the present research is to realize a hybrid control method by using linear and nonlinear terms and to provide a reliable and robust control structure, which is able to track time varying three-axis referenced commands. Subsequently, a stability analysis is presented to verify the performance of the overall proposed cascade attitude control approach. To prove the effectiveness of the presented approach, a thorough investigation is presented compared to a number of recent corresponding benchmarks. PMID:26142216

  18. Active control of the attitude motion and structural vibration of a flexible satellite by jet thrusters

    Science.gov (United States)

    Lee, Mokin

    A Lagrangian formulation is used to obtain the equations of motion of a flexible satellite in a tree-type geometry. The flexible satellite model is the geosynchronous INSAT-II type satellite with a flexible balance beam and a flexible solar panel attached to the rigid main body. In deriving the equations of motion, the orbital motion, the librational motion, and the structural motion of flexible bodies are involved. The assumed-modes method is used to express the deflections of the flexible structures in the form of a finite series of space-dependent admissible functions multiplied by time-dependent amplitudes. The kinetic energy, potential energy, strain energy, and virtual work of the flexible satellite are evaluated as functions of time in terms of the generalized coordinates. Then, by substituting them into Lagrange's equations for discrete systems, the governing equations of motion of the flexible satellite are obtained as a set of second-order nonlinear ordinary differential equations. The attitude motion and the structural motion of the flexible satellite are coupled motions with one another. Uncontrolled dynamics show that the librational and structural motions are oscillatory and undamped motions. The stability and performance of the flexible satellite needs to be improved by designing control systems. A control objective is proposed to improve the stability and performance for pointing accuracy maneuver by controlling the librational motions and flexible modes simultaneously. For the control objective, a control system is synthesized, using feedback linearization control, thrust determination, thrust management, and pulse-width pulse-frequency modulation. Feedback linearization for second-order nonlinear systems is used to obtain a stable feedback control system for the pointing-accuracy control. A stable feedback control system is obtained by adjusting the diagonal matrices of the linear second-order system. Jet thrusters are used as the primary

  19. Cassini Attitude Control Operations Flight Rules and How They are Enforced

    Science.gov (United States)

    Burk, Thomas; Bates, David

    2008-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. Cassini deployed the European-built Huygens probe which descended through the Titan atmosphere and landed on its surface on January 14, 2005. Operating the Cassini spacecraft is a complex scientific, engineering, and management job. In order to safely operate the spacecraft, a large number of flight rules were developed. These flight rules must be enforced throughout the lifetime of the Cassini spacecraft. Flight rules are defined as any operational limitation imposed by the spacecraft system design, hardware, and software, violation of which would result in spacecraft damage, loss of consumables, loss of mission objectives, loss and/or degradation of science, and less than optimal performance. Flight rules require clear description and rationale. Detailed automated methods have been developed to insure the spacecraft is continuously operated within these flight rules. An overview of all the flight rules allocated to the Cassini Attitude Control and Articulation Subsystem and how they are enforced is presented in this paper.

  20. Attitude Determination and Control Subsystem (ADCS) Preparations for the EPOXI Flyby of Comet Hartley 2

    Science.gov (United States)

    Luna, Michael E.; Collins, Steven M.

    2011-01-01

    On November 4, 2010 the former "Deep Impact" spacecraft, renamed "EPOXI" for its extended mission, flew within 700km of comet 103P/Hartley 2. In July 2005, the spacecraft had previously imaged a probe impact of comet Tempel 1. The EPOXI flyby was the fifth close encounter of a spacecraft with a comet nucleus and marked the first time in history that two comet nuclei were imaged at close range with the same suite of onboard science instruments. This challenging objective made the function of the attitude determination and control subsystem (ADCS) critical to the successful execution of the EPOXI flyby.As part of the spacecraft flyby preparations, the ADCS operations team had to perform meticulous sequence reviews, implement complex spacecraft engineering and science activities and perform numerous onboard calibrations. ADCS contributions included design and execution of 10 trajectory correction maneuvers, the science calibration of the two telescopic instruments, an in-flight demonstration of high-rate turns between Earth and comet point, and an ongoing assessment of reaction wheel health. The ADCS team was also responsible for command sequences that included updates to the onboard ephemeris and sun sensor coefficients and implementation of reaction wheel assembly (RWA) de-saturations.

  1. Attitude Determination and Control Subsystem (ADCS) Preparations for the EPOXI Flyby of Comet Haley 2

    Science.gov (United States)

    Luna, Michael E.; Collins, Stephen M.

    2011-01-01

    On November 4, 2010 the already "in-flight" Deep Impact spacecraft flew within 700km of comet 103P/Hartley 2 as part of its extended mission EPOXI, the 5th time to date any spacecraft visited a comet. In 2005, the spacecraft had previously imaged a probe impact comet Tempel 1. The EPOXI flyby marked the first time in history that two comets were explored with the same instruments on a re-used spacecraft-with hardware and software originally designed and optimized for a different mission. This made the function of the attitude determination and control subsystem (ADCS) critical to the successful execution of the EPOXI flyby. As part of the spacecraft team preparations, the ADCS team had to perform thorough sequence reviews, key spacecraft activities and onboard calibrations. These activities included: review of background sequences for the initial conditions vector, sun sensor coefficients, and reaction wheel assembly (RWA) de-saturations; design and execution of 10 trajectory correction maneuvers; science calibration of the two telescope instruments; a flight demonstration of the fastest turns conducted by the spacecraft between Earth and comet point; and assessment of RWA health (given RWA problems on other spacecraft).

  2. Eating attitudes, weight control behaviors and risk factors for eating disorders among Chinese female dance students

    Directory of Open Access Journals (Sweden)

    Zhuoli Tao

    2015-12-01

    Full Text Available Background and Objectives: Along with the economic development, eating disorders begin to appear in China. In this context, we study potential risks for eating disorders. Methods: 1,199 Chinese students, aged 12-25 years, were randomly selected in spring 2006 from a survey with a series of scales (EAT-26, EDI that were used as a screening examination for eating attitudes, weight control behaviors and risk factors. Among them were 31 female Chinese dance students. The dancer students were compared with the female high risk group of eating disorders (EAT ≥ 20 and the female low risk group (EAT 0-9 according to their scores on EAT-26 and EDI. Results: There were just 3 dancers (10% with scores on the EAT-26 who were over the cut-off point of 20 for high risk of an eating disorder. The dance group also showed significantly higher scores than the low risk group (EAT 0-9 not only on the subscales Dieting, and EAT-26 total scores on the EAT-26, but also on the subscales Perfectionism and Maturity Fears on the EDI. Conclusions: Among the group of female Chinese dance students, most participants did not show a high risk for eating disorders and their high scores on some subscales on the EAT-26 and EDI could be caused by their occupation.

  3. Integration and Testing of the Lunar Reconnaissance Orbiter Attitude Control System

    Science.gov (United States)

    Simpson, Jim; Badgley, Jason; McCaughey, Ken; Brown, Kristen; Calhoun, Philip; Davis, Edward; Garrick, Joseph; Gill, Nathaniel; Hsu, Oscar; Jones, Noble; Oritz-Cruz, Gerardo; Raymond, Juan; Roder, Russell; Shah, Neerav; Wilson, John

    2010-01-01

    Throughout the Lunar Reconnaissance Orbiter (LRO) Integration and Testing (I&T) phase of the project, the Attitude Control System (ACS) team completed numerous tests on each hardware component in ever more flight like environments. The ACS utilizes a select group of attitude sensors and actuators. This paper chronicles the evolutionary steps taken to verify each component was constantly ready for flight as well as providing invaluable trending experience with the actual hardware. The paper includes a discussion of each ACS hardware component, lessons learned of the various stages of I&T, a discussion of the challenges that are unique to the LRO project, as well as a discussion of work for future missions to consider as part of their I&T plan. LRO ACS sensors were carefully installed, tested, and maintained over the 18 month I&T and prelaunch timeline. Care was taken with the optics of the Adcole Coarse Sun Sensors (CSS) to ensure their critical role in the Safe Hold mode was fulfilled. The use of new CSS stimulators provided the means of testing each CSS sensor independently, in ambient and vacuum conditions as well as over a wide range of thermal temperatures. Extreme bright light sources were also used to test the CSS in ambient conditions. The integration of the two SELEX Galileo Star Trackers was carefully planned and executed. Optical ground support equipment was designed and used often to check the performance of the star trackers throughout I&T in ambient and thermal/vacuum conditions. A late discovery of potential contamination of the star tracker light shades is discussed in this paper. This paper reviews how each time the spacecraft was at a new location and orientation, the Honeywell Miniature Inertial Measurement Unit (MIMU) was checked for data output validity. This gyro compassing test was performed at several key testing points in the timeline as well as several times while LRO was on the launch pad. Sensor alignment tests were completed several

  4. The effect of family climate on risky driving of young novices: The moderating role of attitude and locus of control

    OpenAIRE

    Carpentier, Aline; BRIJS, Kris; Declercq, Katrien; Brijs, Tom; Daniels, Stijn; Wets, Geert

    2014-01-01

    The aim of the study was to examine the relative importance of young novice drivers’ family climate on their driving behavior. A sample of young novice drivers (N = 171) between the age of 17 and 24, who held their permanent (or temporary) driver's license for no longer than one year, participated. The questionnaire included items related to the participants’ family climate, 3 socio-cognitive determinants (i.e., attitude, locus of control and social norm), and risky driving behaviors. We expe...

  5. Impact of an Oral Health Education Workshop on Parents’ Oral Health Knowledge, Attitude, and Perceived Behavioral Control among African Immigrants

    OpenAIRE

    Maryam Amin; Pawan Nyachhyon; Maryam Elyasi; Muhammed Al-Nuaimi

    2014-01-01

    Purpose. To evaluate the impact of an educational workshop on parental knowledge, attitude, and perceived behavioral control regarding their child’s oral health. Materials and Methods. A one-time oral health education workshop including audio/visual and hands-on components was conducted by a trained dentist and bilingual community workers in community locations. Participants were African parents of children who had lived in Canada for less than ten years. The impact of the workshop was evalua...

  6. Attitudes towards obesity in the Swedish general population: the role of one's own body size, weight satisfaction, and controllability beliefs about obesity.

    Science.gov (United States)

    Hansson, Lena M; Rasmussen, Finn

    2014-01-01

    This study examined the associations of different socio-demographic and psychological factors with attitudes towards obesity. Individuals with different weight status (N=2436) were drawn from an annual population-based survey in Sweden, and data on attitudes towards obesity (ATOP) and predictor variables were assessed in 2008. The strongest predictor of ATOP was controllability beliefs about obesity (β=0.83). Thus, greater controllability beliefs about obesity predicted more negative attitudes. Sex and weight satisfaction were also independently associated with ATOP. However, there was no, or only a weak, association between weight satisfaction and ATOP among individuals with normal weight or overweight. And the higher the weight satisfactions of individuals with obesity, the more positive were their attitudes. It seems that stigma-reduction strategies in the general public should address the uncontrollable factors in the aetiology of obesity. However, more research is needed to understand the underlying causes of people's attitudes towards obesity. PMID:24268600

  7. Magnetic bearing momentum wheels with magnetic gimballing capability for 3-axis active attitude control and energy storage

    Science.gov (United States)

    Sindlinger, R. S.

    1977-01-01

    Magnetic bearings used for the suspension of momentum wheels provide conclusive advantages: the low friction torques and the absence of abrasion allow the realization of lightweight high speed wheels with high angular momentum and energy storage capacity and virtually unlimited lifetime. The use of actively controlled bearings provides a magnetic gimballing capability by applying the external signals to the two servo loops controlling the rotational degrees of freedom. Thus, an attitude control system can be realized by using only one rotating mass for 3-axis active satellite stabilization.

  8. Impact of an Oral Health Education Workshop on Parents’ Oral Health Knowledge, Attitude, and Perceived Behavioral Control among African Immigrants

    Directory of Open Access Journals (Sweden)

    Maryam Amin

    2014-01-01

    Full Text Available Purpose. To evaluate the impact of an educational workshop on parental knowledge, attitude, and perceived behavioral control regarding their child’s oral health. Materials and Methods. A one-time oral health education workshop including audio/visual and hands-on components was conducted by a trained dentist and bilingual community workers in community locations. Participants were African parents of children who had lived in Canada for less than ten years. The impact of the workshop was evaluated by a questionnaire developed based on the theory of planned behavior. Results. A total of 105 parents participated in this study. Participants were mainly mothers (mean age 35.03±5.4 years who came to Canada as refugee (77.1% and had below high school education (70%. Paired t-test showed a significant difference in participants’ knowledge of caries, preventive measures, and benefits of regular dental visits after the workshop (P value<0.05. A significant improvement was also found in parental attitudes toward preventive measures and their perceived behavioral control (P<0.05. Parents’ intention to take their child to a dentist within six months significantly altered after the workshop (P value<0.05. Conclusions. A one-time hands-on training was effective in improving parental knowledge, attitude, perceived behavioral control, and intention with respect to their child’s oral health and preventive dental visits in African immigrants.

  9. Programmable scan/read circuitry for charge coupled device imaging detectors. [spcecraft attitude control and star trackers

    Science.gov (United States)

    Salomon, P. M.; Smilowitz, K.

    1984-01-01

    A circuit for scanning and outputting the induced charges in a solid state charge coupled device (CCD) image detector is disclosed in an image detection system for use in a spacecraft attitude control system. The image detection system includes timing control circuitry for selectively controlling the output of the CCD detector so that video outputs are provided only with respect to induced charges corresponding to predetermined sensing element lines of the CCD detector. The timing control circuit and the analog to digital converter are controlled by a programmed microprocessor which defines the video outputs to be converted and further controls the timing control circuit so that no video outputs are provided during the delay associated with analog to digital conversion.

  10. Attitudes and attitude change

    DEFF Research Database (Denmark)

    Scholderer, Joachim

    2010-01-01

    attitude theory. Why is this important? Attitudinal concepts can be found in every area of marketing. Concepts like ad liking, brand attitude, quality perception, product preference, perceived benefit, perceived risk, perceived value, and customer satisfaction can all be understood as particular types of...... attitudes. This is the reason why a thorough understanding of attitudes is one of the most important skills a marketer can have. That same is true in related areas such as communications research: concepts like public opinion, corporate reputation, and corporate image are nothing more than particular types...

  11. Acoustic-Modal Testing of the Ares I Launch Abort System Attitude Control Motor Valve

    Science.gov (United States)

    Davis, R. Benjamin; Fischbach, Sean R.

    2010-01-01

    The Attitude Control Motor (ACM) is being developed for use in the Launch Abort System (LAS) of NASA's Ares I launch vehicle. The ACM consists of a small solid rocket motor and eight actuated pintle valves that directionally allocate.thrust_- 1t.has-been- predicted-that significant unsteady. pressure.fluctuations.will.exist. inside the-valves during operation. The dominant frequencies of these oscillations correspond to the lowest several acoustic natural frequencies of the individual valves. An acoustic finite element model of the fluid volume inside the valve has been critical to the prediction of these frequencies and their associated mode shapes. This work describes an effort to experimentally validate the acoustic finite model of the valve with an acoustic modal test. The modal test involved instrumenting a flight-like valve with six microphones and then exciting the enclosed air with a loudspeaker. The loudspeaker was configured to deliver broadband noise at relatively high sound pressure levels. The aquired microphone signals were post-processed and compared to results generated from the acoustic finite element model. Initial comparisons between the test data and the model results revealed that additional model refinement was necessary. Specifically, the model was updated to implement a complex impedance boundary condition at the entrance to the valve supply tube. This boundary condition models the frequency-dependent impedance that an acoustic wave will encounter as it reaches the end of the supply tube. Upon invoking this boundary condition, significantly improved agreement between the test data and the model was realized.

  12. Auto Code Generation for Simulink-Based Attitude Determination Control System

    Science.gov (United States)

    MolinaFraticelli, Jose Carlos

    2012-01-01

    This paper details the work done to auto generate C code from a Simulink-Based Attitude Determination Control System (ADCS) to be used in target platforms. NASA Marshall Engineers have developed an ADCS Simulink simulation to be used as a component for the flight software of a satellite. This generated code can be used for carrying out Hardware in the loop testing of components for a satellite in a convenient manner with easily tunable parameters. Due to the nature of the embedded hardware components such as microcontrollers, this simulation code cannot be used directly, as it is, on the target platform and must first be converted into C code; this process is known as auto code generation. In order to generate C code from this simulation; it must be modified to follow specific standards set in place by the auto code generation process. Some of these modifications include changing certain simulation models into their atomic representations which can bring new complications into the simulation. The execution order of these models can change based on these modifications. Great care must be taken in order to maintain a working simulation that can also be used for auto code generation. After modifying the ADCS simulation for the auto code generation process, it is shown that the difference between the output data of the former and that of the latter is between acceptable bounds. Thus, it can be said that the process is a success since all the output requirements are met. Based on these results, it can be argued that this generated C code can be effectively used by any desired platform as long as it follows the specific memory requirements established in the Simulink Model.

  13. 控制分配在平流层飞艇姿态控制中的应用%Control allocation approach for stratospheric airship attitude control

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    针对平流层飞艇一般采用多控制机构的特点,将广义逆控制分配方法应用到飞艇姿态控制系统中,并根据飞艇控制机构特性采用了加权伪逆控制分配算法。飞艇姿态控制仿真结果表明:设计的控制分配方法可以有效实现多控制机构的协调操纵,对姿态角控制效果良好,避免了单一操纵舵面过早进入饱和状态的情况;合理调整控制分配权值可减少能量损耗,增强实时性,便于工程实现。%The stratospheric airships generally act with the redundant control effectors,thus a control allocation approach based on generalized inverse was applied to the airship attitude control system and the weighted pseudo-inverse control allocation method was adopted on the basis of characteristics of airship control effectors.The simulation results of a stratospheric airship attitude control show that:the designed control allocation approach can realize the coordinated operation of redundant control effectors effectively and its control effect on attitude angle is good,which avoids the premature saturation of control surface when using single effector;the reasonable adjustment of control allocation weights can reduce energy consumption,enhance instantaneity and provide convenience in engineering.

  14. Control allocation approach for stratospheric airship attitude control%控制分配在平流层飞艇姿态控制中的应用

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    针对平流层飞艇一般采用多控制机构的特点,将广义逆控制分配方法应用到飞艇姿态控制系统中,并根据飞艇控制机构特性采用了加权伪逆控制分配算法。飞艇姿态控制仿真结果表明:设计的控制分配方法可以有效实现多控制机构的协调操纵,对姿态角控制效果良好,避免了单一操纵舵面过早进入饱和状态的情况;合理调整控制分配权值可减少能量损耗,增强实时性,便于工程实现。%The stratospheric airships generally act with the redundant control effectors,thus a control allocation approach based on generalized inverse was applied to the airship attitude control system and the weighted pseudo-inverse control allocation method was adopted on the basis of characteristics of airship control effectors.The simulation results of a stratospheric airship attitude control show that:the designed control allocation approach can realize the coordinated operation of redundant control effectors effectively and its control effect on attitude angle is good,which avoids the premature saturation of control surface when using single effector;the reasonable adjustment of control allocation weights can reduce energy consumption,enhance instantaneity and provide convenience in engineering.

  15. Relationship of credit attitude and debt to self-esteem and locus of control in college-age consumers.

    Science.gov (United States)

    Pinto, Mary Beth; Mansfield, Phylis M; Parente, Diane H

    2004-06-01

    College-age consumers are one of the groups most highly targeted by credit card marketers. While some college students use their credit cards wisely, others are unable to control their spending. The objective of this study was to investigate differences in attitude toward credit cards and the psychological factors of self-esteem and locus of control among college students who possess one or more credit cards. Attitude was operationalized to include three underlying components: cognitive, affective, and behavioral. We separated credit users into subcategories based on amount of installment debt. Convenience users were defined as those consumers who paid the credit-card balance in full each month. Installment users were classified as consumers who carried a balance month-to-month. Convenience users were compared to mild and heavy installment users to assess significance of differences in attitudinal and psychological factors. There were no significant differences in the psychological factors across the credit-card user groups. In addition, there was a statistically significant difference on each of the attitude components (knowledge/beliefs, affect, and behavior) across user groups; convenience users, mild installment, and heavy installment users. PMID:15362425

  16. A low-noise, high-bandwidth magnetically-levitated momentum-wheel for 3-axis attitude control from a single wheel

    OpenAIRE

    Seddon, Jon; Pechev, Alexandre

    2009-01-01

    This paper proposes a new concept for attitude actuation for small satellites that uses active magnetic bearings to support and tilt a spinning rotor to provide 3-axis attitude control of the satellite using a single actuator. A controlled 3D motion in the spinning rotor provides a conventional torque output about the momentum axis and a gyroscopic torque output about any direction in the plane normal to the spinning axis. Therefore, a single tilting momentum-wheel can generate torque along t...

  17. Power, thermal, and attitude control design interactions of the CCE/AMPTE spacecraft. [Charge Composition Explorer/Active Magnetospheric Particle Tracer Explorers

    Science.gov (United States)

    Wingate, C. A., Jr.; Allen, W. E.; Smola, J. F.; Ray, J. C.

    1982-01-01

    The power, thermal and attitude control interactions of the CCE spacecraft and the design compromises resulting from these interactions are described. These compromises result from the conflict between the plane change maneuver requirements and the final on station requirements. The resolution of these conflicts to arrive at an acceptable final design, is given and the resulting power, thermal and attitude control systems are described in some detail.

  18. Evaluating the effect of Focus Farms on Ontario dairy producers' knowledge, attitudes, and behavior toward control of Johne's disease.

    Science.gov (United States)

    Roche, S M; Jones-Bitton, A; Meehan, M; Von Massow, M; Kelton, D F

    2015-08-01

    This study evaluated a participatory-based, experiential learning program, Ontario Focus Farms (FF), which aimed to change dairy producer behavior to control Johne's disease (JD) in Ontario, Canada. The goals were to (1) assess the effect of FF on participating dairy producers' knowledge, attitudes, and behavior with regard to JD control; (2) compare changes in these factors among FF participants to changes among a group of nonparticipating dairy producers; and (3) describe the characteristics of producers who made at least one on-farm management change. Pre- and post-FF intervention questionnaires collected data on respondents' knowledge, attitudes, behavior, herd production, and demographic information; before and after JD-risk assessments were used to assess respondents' on-farm risk of JD transmission. Overall, 176 dairy producers participated in the FF process; 39.8% (70/176) of FF and 14.6% (52/357) of control participants responded to both the pre- and postintervention questionnaires. Upon comparison, FF respondents were more likely to be younger, have larger herds, and have higher management scores. The proportion of FF participants who reported making at least one on-farm change (81%) was significantly higher than that of control respondents (38%). Overall, FF respondents significantly changed their risk score in 4 out of 5 risk areas and had an average reduction of 13 points in their overall risk score between before and after risk assessments. Control respondents' risk assessment scores did not significantly change during the study period. In a JD knowledge assessment, FF and control respondents exhibited a moderate knowledge score before the intervention period, with median scores of 75.9% (22/29) in each group. The FF respondents significantly increased their score at the postintervention assessment, with a median of 82.8% (24/29); control-respondent scores did not significantly change. Both FF and control respondents held strong positive attitudes

  19. Knowledge, awareness, and attitude regarding infection prevention and control among medical students: a call for educational intervention

    Science.gov (United States)

    Ibrahim, Awab Ali; Elshafie, Sittana Shamseldin

    2016-01-01

    Background Medical students can be exposed to serious health care-associated infections, if they are not following infection prevention and control (IPC) measures. There is limited information regarding the knowledge, awareness, and practices of medical students regarding IPC and the educational approaches used to teach them these practices. Aim To evaluate the knowledge, awareness, and attitude of medical students toward IPC guidelines, and the learning approaches to help improve their knowledge. Methods A cross-sectional, interview-based survey included 73 medical students from Weill Cornell Medical College, Qatar. Students completed a questionnaire concerning awareness, knowledge, and attitude regarding IPC practices. Students’ knowledge was assessed by their correct answers to the survey questions. Findings A total of 48.44% of the respondents were aware of standard isolation precautions, 61.90% were satisfied with their training in IPC, 66.13% were exposed to hand hygiene training, while 85.48% had sufficient knowledge about hand hygiene and practiced it on a routine basis, but only 33.87% knew the duration of the hand hygiene procedure. Conclusion Knowledge, attitude, and awareness of IPC measures among Weill Cornell Medical Students in Qatar were found to be inadequate. Multifaceted training programs may have to target newly graduated medical practitioners or the training has to be included in the graduate medical curriculum to enable them to adopt and adhere to IPC guidelines.

  20. Advanced Materials and Fabrication Techniques for the Orion Attitude Control Motor

    Science.gov (United States)

    Gorti, Sridhar; Holmes, Richard; O'Dell, John; McKechnie, Timothy; Shchetkovskiy, Anatoliy

    2013-01-01

    Rhenium, with its high melting temperature, excellent elevated temperature properties, and lack of a ductile-to-brittle transition temperature (DBTT), is ideally suited for the hot gas components of the ACM (Attitude Control Motor), and other high-temperature applications. However, the high cost of rhenium makes fabricating these components using conventional fabrication techniques prohibitive. Therefore, near-net-shape forming techniques were investigated for producing cost-effective rhenium and rhenium alloy components for the ACM and other propulsion applications. During this investigation, electrochemical forming (EL-Form ) techniques were evaluated for producing the hot gas components. The investigation focused on demonstrating that EL-Form processing techniques could be used to produce the ACM flow distributor. Once the EL-Form processing techniques were established, a representative rhenium flow distributor was fabricated, and samples were harvested for material properties testing at both room and elevated temperatures. As a lower cost and lighter weight alternative to an all-rhenium component, rhenium- coated graphite and carbon-carbon were also evaluated. The rhenium-coated components were thermal-cycle tested to verify that they could withstand the expected thermal loads during service. High-temperature electroforming is based on electrochemical deposition of compact layers of metals onto a mandrel of the desired shape. Mandrels used for electro-deposition of near-net shaped parts are generally fabricated from high-density graphite. The graphite mandrel is easily machined and does not react with the molten electrolyte. For near-net shape components, the inner surface of the electroformed part replicates the polished graphite mandrel. During processing, the mandrel itself becomes the cathode, and scrap or refined refractory metal is the anode. Refractory metal atoms from the anode material are ionized in the molten electrolytic solution, and are deposited

  1. Attitudes, norms and controls influencing lifestyle risk factor management in general practice

    Directory of Open Access Journals (Sweden)

    McKenzie Suzanne H

    2009-08-01

    patient's motivation, and cost and accessibility of services to patients. Conclusion General practitioner attitudes, normative influences from both patients and the profession, and perceived external control factors (time, cost, availability and practice capacity all influence management of behavioural risk factors. Provider education, community awareness raising, support and capacity building may improve the uptake of lifestyle modification interventions.

  2. Stroke patients and their attitudes toward mHealth monitoring to support blood pressure control and medication adherence

    Science.gov (United States)

    Jenkins, Carolyn; Burkett, Nina-Sarena; Ovbiagele, Bruce; Mueller, Martina; Patel, Sachin; Brunner-Jackson, Brenda; Saulson, Raelle; Treiber, Frank

    2016-01-01

    Background Mobile health, or mHealth, has increasingly been signaled as an effective means to expedite communication and improve medical regimen adherence, especially for patients with chronic health conditions such as stroke. However, there is a lack of data on attitudes of stroke patients toward mHealth. Such information will aid in identifying key indicators for feasibility and optimal implementation of mHealth to prevent and/or decrease rates of secondary stroke. Our objective was to ascertain stroke patients’ attitudes toward using mobile phone enabled blood pressure (BP) monitoring and medication adherence and identify factors that modulate these attitudes. Methods Sixty stroke patients received a brief demonstration of mHealth devices to assist with BP control and medication adherence and a survey to evaluate willingness to use this technology. Results The 60 participants had a mean age of 57 years, were 43.3% male, and 53.3% were White. With respect to telecommunication prevalence, 93.3% owned a cellular device and 25% owned a smartphone. About 70% owned a working computer. Regarding attitudes, 85% felt comfortable with a doctor or nurse using mHealth technologies to monitor personal health information, 78.3% believed mHealth would help remind them to follow doctor’s directions, and 83.3% were confident that technology could effectively be used to communicate with health care providers for medical needs. Conclusions Mobile device use is high in stroke patients and they are amenable to mHealth for communication and assistance in adhering to their medical regimens. More research is needed to explore usefulness of this technology in larger stroke populations.

  3. Modeling Attitude Dynamics in Simulink: A Study of the Rotational and Translational Motion of a Spacecraft Given Torques and Impulses Generated by RMS Hand Controllers

    Science.gov (United States)

    Mauldin, Rebecca H.

    2010-01-01

    In order to study and control the attitude of a spacecraft, it is necessary to understand the natural motion of a body in orbit. Assuming a spacecraft to be a rigid body, dynamics describes the complete motion of the vehicle by the translational and rotational motion of the body. The Simulink Attitude Analysis Model applies the equations of rigid body motion to the study of a spacecraft?s attitude in orbit. Using a TCP/IP connection, Matlab reads the values of the Remote Manipulator System (RMS) hand controllers and passes them to Simulink as specified torque and impulse profiles. Simulink then uses the governing kinematic and dynamic equations of a rigid body in low earth orbit (LE0) to plot the attitude response of a spacecraft for five seconds given known applied torques and impulses, and constant principal moments of inertia.

  4. Don't give me attitude: Can perceptions of social norms, behavioral control and moral intensity help bridge the attitude-behavior gap in ethical consumer behavior?

    OpenAIRE

    Gloukhovtsev, Alexei

    2014-01-01

    The last couple of decades have seen a significant increase in positive attitudes towards ethical products and services. However, this increase is has yet to lead to a marked growth in the sales of such products. This thesis looks at the consumer decision-making process in situations where a moral issue or dilemma is present, and examines possible reasons for the disconnect between consumers' attitudes and behavioral intentions. Drawing on Icek Ajzen's (1985) theory of planned behavior, t...

  5. A summary of the mechanical design, testing and performance of the IMP-H and J attitude control systems

    Science.gov (United States)

    Metzger, J. R.

    1974-01-01

    The main aspects of the attitude control system used on both the IMP-H and J spacecraft are presented. The mechanical configuration is described. Information on all the specific components comprising the flight system is provided. The acceptance and qualification testing of both individual components and the installed system are summarized. Functional information regarding the operation and performance in relation to the orbiting spacecraft and its mission is included. Related topics which are discussed are: (1) safety requirements, (2) servicing procedures, (3) anomalous behavior, and (4) pyrotechnic devices.

  6. Scout fourth stage attitude and velocity control (AVC) system feasibility study

    Science.gov (United States)

    Byars, L. B.

    1975-01-01

    The feasibility of incorporating a guidance system in the Scout fourth stage to achieve a significant improvement in expected payload delivery accuracy is studied. The technical investigations included the determination of the AVC equipment performance requirements, establishment of qualification and acceptance test levels, generation of layouts illustrating design approaches for the upper D and payload transition sections to incorporate the hardware, and the preparation of a vendor bid package. Correction concepts, utilizing inertial velocity and attitude, were identified and evaluated. Fourth stage attitude adjustments as determined from inertial velocity variation through the first three stages and a final velocity correction based upon the measured in-plane component errors at injection were employed. Results show radical reductions in apogee-perigee deviations.

  7. Farmer Attitudes and Livestock Disease: Exploring Citizenship Behaviour and Peer Monitoring across Two BVD Control Schemes in the UK.

    Science.gov (United States)

    Heffernan, Claire; Azbel-Jackson, Lena; Brownlie, Joe; Gunn, George

    2016-01-01

    The eradication of BVD in the UK is technically possible but appears to be socially untenable. The following study explored farmer attitudes to BVD control schemes in relation to advice networks and information sharing, shared aims and goals, motivation and benefits of membership, notions of BVD as a priority disease and attitudes toward regulation. Two concepts from the organisational management literature framed the study: citizenship behaviour where actions of individuals support the collective good (but are not explicitly recognised as such) and peer to peer monitoring (where individuals evaluate other's behaviour). Farmers from two BVD control schemes in the UK participated in the study: Orkney Livestock Association BVD Eradication Scheme and Norfolk and Suffolk Cattle Breeders Association BVD Eradication Scheme. In total 162 farmers participated in the research (109 in-scheme and 53 out of scheme). The findings revealed that group helping and information sharing among scheme members was low with a positive BVD status subject to social censure. Peer monitoring in the form of gossip with regard to the animal health status of other farms was high. Interestingly, farmers across both schemes supported greater regulation with regard to animal health, largely due to the mistrust of fellow farmers following voluntary disease control measures. While group cohesiveness varied across the two schemes, without continued financial inducements, longer-term sustainability is questionable. PMID:27023269

  8. Attitude control system design and on-orbit performance analysis of nano-satellite—“Tian Tuo 1”

    Directory of Open Access Journals (Sweden)

    Ran Dechao

    2014-06-01

    Full Text Available “Tian Tuo 1” (TT-1 nano-satellite is the first single-board nano-satellite that was successfully launched in China. The main objective of TT-1 is technology demonstration and scientific measurements. The satellite carries out the significant exploration of single-board architecture feasibility validation, and it is tailored to the low-cost philosophy by adopting numerous commercial-off-the-shelf (COTS components. The satellite is featured with three-axis stabilization control capability. A pitch bias momentum wheel and three magnetic coils are adopted as control actuators. The sun sensors, magnetometers and a three-axis gyro are employed as the measurement sensors. The quaternion estimator (QUEST and unscented Kalman filter (UKF method are adopted for the nano-satellite attitude determination. On-orbit data received by ground station is conducted to analysis the performance of attitude determination and control system (ADCS. The results show that the design of ADCS for TT-1 is suitable, robust and feasible.

  9. A close examination of under-actuated attitude control subsystem design for future satellite missions' life extension

    Science.gov (United States)

    Lam, Quang M.; Barkana, Itzhak

    2014-12-01

    Satellite mission life, maintained and prolonged beyond its typical norm of their expectancy, are primarily dictated by the state of health of its Reaction Wheel Assembly (RWA), especially for commercial GEO satellites since torquer bars are no longer applicable while thruster assistant is unacceptable due to pointing accuracy impact during jet firing. The RWA is the primary set of actuators (as compared to thrusters for orbit maintenance and maneuvering) mainly responsible for the satellite mission for accurately and precisely pointing its payloads to the right targets to conduct its mission operations. The RWA consisting of either a set of four in pyramid or three in orthogonal is the primary set of actuators to allow the satellite to achieve accurate and precise pointing of the satellite payloads towards the desired targets. Future space missions will be required to achieve much longer lives and are currently perceived by the GEO satellite community as an "expected norm" of 20 years or longer. Driven by customers' demands/goals and competitive market have challenged Attitude Control Subsystems (ACS) engineers to develop better ACS algorithms to address such an emerging need. There are two main directions to design satellite's under-actuated control subsystem: (1) Attitude Feedback with Zero Momentum Principle and (2) Attitude Control by Angular Velocity Tracking via Small Time Local Controllability concept. Successful applications of these control laws have been largely demonstrated via simulation for the rest to rest case. Limited accuracy and oscillatory behaviors are observed in three axes for non-zero wheel momentum while realistic loss of a wheel scenario (i.e., fully actuated to under-actuated) has not been closely examined! This study revisits the under-actuated control design with detailed set ups of multiple scenarios reflecting real life operating conditions which have put current under-actuated control laws mentioned earlier into a re-evaluation mode

  10. A Near-Hover Adaptive Attitude Control Strategy of a Ducted Fan Micro Aerial Vehicle with Actuator Dynamics

    Directory of Open Access Journals (Sweden)

    Shouzhao Sheng

    2015-09-01

    Full Text Available The aerodynamic parameters of ducted fan micro aerial vehicles (MAVs are difficult and expensive to precisely measure and are, therefore, not available in most cases. Furthermore, the actuator dynamics with risks of potentially destabilizing the overall system are important but often neglected consideration factors in the control system design of ducted fan MAVs. This paper presents a near-hover adaptive attitude control strategy of a prototype ducted fan MAV with actuator dynamics and without any prior information about the behavior of the MAV. The proposed strategy consists of an online parameter estimation algorithm and an adaptive gain scheduling algorithm, with the former accommodating parametric uncertainties, and the latter approximately eliminating the coupling among axes and guaranteeing the control quality of the MAV. The effectiveness of the proposed strategy is verified numerically and experimentally.

  11. Sexual and contraceptives attitudes, the locus of health control and self-esteem among higher education students

    Directory of Open Access Journals (Sweden)

    José Manuel da Silva Vilelas Janeiro

    2014-09-01

    Full Text Available Objective: To analyze the relationship between sexual and contraceptive attitudes, the locus of health control and self-esteem among students of a private institution of higher education. Methods: Descriptive and correlational study with a quantitative approach, performed in a higher education school in Lisbon, with 152 students, from the 1st to the 4th year of undergraduate courses in Nursing, Physiotherapy, Cardiopneumology and Radiology. As research instrument, it was used a questionnaire with rating scales on ‘sexual attitudes’, ‘contraception attitudes’, ‘locus of health control’ and ‘self-esteem’. The data obtained was analyzed using descriptive and inferential statistics. Results: The majority of students (90.7% have already had sexual intercourse. Sexual attitudes were influenced by gender (p=0.0035, but not by the start of sexual activity or by the course’s year (p>0.05. Contraceptive attitudes were related to the year that students attended (p=0.031 and to gender (p=0.029. The external locus of control, on average, was higher among girls (29.2 than boys (30.1. The self-esteem increased with the student’s age (p=0.003. Conclusion: Investment in the area of sexual education is needed in the undergraduate programs, since the young people live their days in the school setting, spending little time with their families. The university should assume a special position in the development of the concept of sexuality based on the holistic perspective of the human being, promoting sexual education as essential in the construction of human identity and fundamental for health promotion doi: http://dx.doi.org/10.5020/18061230.2013.p505

  12. A controlled experiment to evaluate the impact of summer research experiences on attitudes towards science in high school aged students

    Science.gov (United States)

    White, M. A.; Tcherednichenko, I.; Hamar, M.; Taylor, M. J.; Litizzette, L.

    2006-12-01

    United States funding agencies increasingly are supporting activities designed to increase the enrollment of United States high school students in science, math, or engineering careers. However, in many cases, the likely outcomes of educational activities are unknown. A common approach within the physical and natural sciences is to provide high school aged students with a summer research experience, with the expectation that such experiences will increase student interest in science, possibly as a career choice. With funding support from the National Aeronautics and Space Administration New Investigator Grant program, we conducted a controlled experiment to test this assumption. In collaboration with Mountain Crest High School in Logan, UT, we recruited 40 students currently enrolled in science courses, assessed attitudes towards science (with informed consent), and randomly assigned 20 students to a control group and 20 students to an experimental group. Students in the experimental group were paired with faculty and graduate students in a wide range of field and laboratory research groups in natural resources and biology. Students were employed in at least two different research groups for an average of 30-40 hours per week for eight weeks in the summer of 2006. Following the completion of the summer work experience, we again assessed attitudes towards science in both groups and gathered additional information from the experimental group on satisfaction with the work experience and reasons for participating. Results are presented and discussed.

  13. Opportunities for improved chagas disease vector control based on knowledge, attitudes and practices of communities in the yucatan peninsula, Mexico.

    Directory of Open Access Journals (Sweden)

    Kathryn Rosecrans

    2014-03-01

    Full Text Available BACKGROUND: Chagas disease is a vector-borne parasitic disease of major public health importance. Current prevention efforts are based on triatomine vector control to reduce transmission to humans. Success of vector control interventions depends on their acceptability and value to affected communities. We aimed to identify opportunities for and barriers to improved vector control strategies in the Yucatan peninsula, Mexico. METHODOLOGY/PRINCIPAL FINDINGS: We employed a sequence of qualitative and quantitative research methods to investigate knowledge, attitudes and practices surrounding Chagas disease, triatomines and vector control in three rural communities. Our combined data show that community members are well aware of triatomines and are knowledgeable about their habits. However, most have a limited understanding of the transmission dynamics and clinical manifestations of Chagas disease. While triatomine control is not a priority for community members, they frequently use domestic insecticide products including insecticide spray, mosquito coils and plug-in repellents. Families spend about $32 US per year on these products. Alternative methods such as yard cleaning and window screens are perceived as desirable and potentially more effective. Screens are nonetheless described as unaffordable, in spite of a cost comparable to the average annual spending on insecticide products. CONCLUSION/SIGNIFICANCE: Further education campaigns and possibly financing schemes may lead families to redirect their current vector control spending from insecticide products to window screens. Also, synergism with mosquito control efforts should be further explored to motivate community involvement and ensure sustainability of Chagas disease vector control.

  14. Solar-sail attitude control based on moving masses and roll stabilizer bars%采用滑块和RSB的太阳帆姿态控制

    Institute of Scientific and Technical Information of China (English)

    罗超; 郑建华

    2011-01-01

    本文研究以滑块和滚转轴稳定条RSB(Roll Stabilizer Bars)作为执行机构的太阳帆航天器的姿态控制,分析了姿态控制机构的物理模型,利用欧拉方程建立了太阳帆的姿态动力学模型.针对此类模型,设计了太阳帆航天器三轴姿态控制系统,通过数值仿真研究了三轴姿态控制的短期响应特性.最后以中科院空间中心提出的SPORT(Solar Polar Orbit Radio Telescope)任务为背景,研究了在轨道转移过程中太阳帆的姿态控制效果.仿真结果表明,基于滑块和滚转轴稳定条控制的太阳帆能够满足大角度快速的姿态机动要求,从而实现任务要求的目标轨道.%In this paper, solar-sail attitude control system which employed moving masses for pitch/yaw trim control and roll stabilizer bars for roll control was studied. Physical model of solar-sail attitude control system had been analyzed, and the dynamical model was establishe d using Euler' s attitude dynamical equations. According to the model, a nonlinear PID controller was found to control the three-axis attitudes. Finally, a series of simulations, including the Solar Polar Orbit Radio Telescope misson' s trajectory transfer, were run to determine the effectiveness of the attitude controller and characterize the behavior of attitude control method using moving masses and RSB.

  15. Sexual Risk Attitudes and Intentions of Youth Aged 12-14 Years: Survey Comparisons of Parent-Teen Prevention and Control Groups

    Science.gov (United States)

    Lederman, Regina P.; Chan, Wenyaw; Roberts-Gray, Cynthia

    2004-01-01

    In this study, the authors compared differences in sexual risk attitudes and intentions for three groups of youth (experimental program, n = 90; attention control, n = 80; and nonparticipant control, n = 634) aged 12-14 years. Two student groups participated with their parents in programs focused on strengthening family interaction and prevention…

  16. Application of fuzzy logic-neural network based reinforcement learning to proximity and docking operations: Attitude control results

    Science.gov (United States)

    Jani, Yashvant

    1992-01-01

    As part of the RICIS activity, the reinforcement learning techniques developed at Ames Research Center are being applied to proximity and docking operations using the Shuttle and Solar Max satellite simulation. This activity is carried out in the software technology laboratory utilizing the Orbital Operations Simulator (OOS). This report is deliverable D2 Altitude Control Results and provides the status of the project after four months of activities and outlines the future plans. In section 2 we describe the Fuzzy-Learner system for the attitude control functions. In section 3, we provide the description of test cases and results in a chronological order. In section 4, we have summarized our results and conclusions. Our future plans and recommendations are provided in section 5.

  17. Changes in eating attitudes, body esteem and weight control behaviours during adolescence in a South African cohort.

    Directory of Open Access Journals (Sweden)

    Tabither M Gitau

    Full Text Available Failure to consume an adequate diet or over consumption during adolescence can disrupt normal growth and development, resulting in undesirable weight change. This leads to an increase in unhealthy weight control practices related to eating and exercise among both adolescent girls and boys to meet the societal 'ideal' body shape. This study therefore aims to examine the longitudinal changes in eating attitudes, body-esteem and weight control behaviours among adolescents between 13 and 17 years; and, to describe perceptions around body shape at age 17 years. A total of 1435 urban South African black and mixed ancestry boys and girls, who had data at both age 13 and 17 years from the Birth to Twenty cohort were included. Data were collected through self-administered questionnaires on eating attitudes (EAT-26, body esteem and weight control behaviours for either weight loss or muscle gain attempts. Height and weight were measured at both time points and BMI was calculated. Black females had a higher BMI (p<0.001 and an increased risk of developing eating disorders as well as significant increase in the prevalence of weight loss practices between the ages 13 and 17 years. At age 17 years both Mixed ancestry adolescents had lower body-esteem compared to black adolescents. The prevalence of possible eating disorders was 11% and 13.1% in early and late adolescents respectively. Males and females shared similar opinions on normal silhouettes being the 'best', 'getting respect' and being the 'happiest', while the obese silhouette was associated with the 'worst' and the 'unhappiest', and the underweight silhouette with the "weakest". Black females had a higher BMI and an increased risk of developing eating disorders. Adolescent females engaged more in weight loss practices whereas, males in muscle gain practices indicating that Western norms of thinness as the ideal are becoming more common in South Africa.

  18. Controlling the Attitude Maneuvers of Flexible Spacecraft by Using Time-Optimal Shaped Inputs

    Science.gov (United States)

    Parman, S.; Koguchi, H.

    1999-04-01

    A three-dimensional rest-to-rest attitude maneuver of flexible spacecraft equipped with on-off reaction jets is studied. Equations of motion of the spacecraft are developed by using Lagrangian formulation. The finite element method is used to discretize elastic deformations of a particular model of satellite with flexible solar panels by modelling the panels as flat plate structures in bending. Under unshaped inputs, the maneuvers induce an undesirable motion of the satellite as well as vibration of the solar panels. Time-optimal and fuel-efficient input shapers are then applied to reduce the residual oscillation of its motion at several natural frequencies in order to get an expected pointing precision of the satellite. Once the shaped inputs are given to the satellite, the performance improves significantly. Results indicate that, the fuel-efficient shaped inputs give smaller maximum deflections of flexible members compared with the time-optimal ones.

  19. In-orbit performance of the ITOS improved attitude control system with Hall generator brushless motor and earth-splitting technique

    Science.gov (United States)

    Peacock, W. M.

    1973-01-01

    The National Aeronautics and Space Administration (NASA), launched ITOS-D with an improved attitude control system. A Hall generator brushless dc torque motor replaced the brush dc torque motor on Tiros-M and ITOS-A. Two CO2 attitude horizon sensors and one mirror replaced the four wideband horizon sensors and two mirrors on ITOS-1 and NOAA-1. Redundant pitch-control electronic boxes containing additional electronic circuitry for earth-splitting and brushless motor electronics were used. A method of generating a spacecraft earth-facing side reference for comparison to the time occurrence of the earth-splitting pulse was used to automatically correct pitch-attitude error. A single rotating flywheel, supported by a single bearing, provided gyroscopic stability and the required momentum interchange to keep one side of the satellite facing the earth. Magnetic torquing against the earth's magnetic field eliminated the requirement for expendable propellants which would limit satellite life in orbit.

  20. Neural networks based three-axis satellite attitude control using only magnetic torquers

    International Nuclear Information System (INIS)

    Full text: Magnetic control is a favorable way to stabilize small satellites. Often, the hardware is simple and lightweight, and does not degrade or change mass over time. However, a magnetic control system does have some disadvantages and limitations. The control, which is in the form of magnetic moment, can only be applied perpendicular to the local magnetic field. In addition, there is uncertainty in the Earth magnetic field models due to the complicated dynamic nature of the field. Also, the magnetic hardware and the spacecraft can interact, causing both to behave in undesirable ways. To overcome these limitations some intelligence is incorporated in the controller. In this paper, control laws are developed to stabilize spacecraft on Three axes. The motivation for this project is ANUSAT, which is a micro-satellite under development at Anna University in collaboration with ISRO. This control could be carried out solely with satellite's magnetometer measurements and its position in orbit. The magnetic dipole moment for control is: M = Kp (Bo - Br) + Kd (dBo/dt - dBr/dt) Where Bo is the measured magnetic field, Br is the reference magnetic field, and Kp and Kd are the control position and rate gains respectively. The value of the controller gains are selected by the Intelligent Neural Network System in the feedback path. Control laws are numerically tested to show that the magnetic control system works within resolution limits

  1. Using E-Portfolios in a Field Experience Placement: Examining Student-Teachers' Attitudes towards Learning in Relationship to Personal Value, Control and Responsibility

    Science.gov (United States)

    Shroff, Ronnie H.; Trent, John; Ng, Eugenia M. W.

    2013-01-01

    This study extends the ownership of learning model by using e-portfolios in a field experience placement to examine student-teachers' attitudes towards learning in relationship to personal value, feeling in control and taking responsibility. A research model is presented based on research into ownership of learning. The student e-portfolio…

  2. Design of Four Rotor Attitude Controller Based on ARM%基于AR M的四旋翼姿态控制器设计

    Institute of Scientific and Technical Information of China (English)

    吴承建; 沈捷; 陈乾坤

    2016-01-01

    四旋翼姿态控制器采用集成了加速度计和陀螺仪的惯性测量单元,实时采集姿态数据,传输给Cortex-M4内核的处理芯片,利用四元数姿态解算方法,对加速度和角速度数据融合解算处理;采用位置式PID控制算法,控制4个无刷电机的转速,实现控制四旋翼飞行器的飞行姿态;建立万向云台调试系统,通过实践调试验证该控制器能实现控制四旋翼姿态的稳定性;稳定飞行时,姿态角的平均振荡范围为5°。%Four rotor attitude controller adopts the inertial measurement unit which integrated accelerometer with gyro,gather attitude data real-time,then transferred to the Cortex-M4 core processing chips,Using the attitude of quaternion calculation method,the data in-tegration of acceleration and angular velocity is calculated.And use positional PID control algorithm to control four brushless motor speed to achieve controlled four-rotor aircraft flight attitude.Establish universal platform debug system,through the practice of testing to verify controller can achieve the stability control of four rotor profile.The stable flight attitude average oscillation angle range is 5 degree.

  3. Nature and operation of attitudes.

    Science.gov (United States)

    Ajzen, I

    2001-01-01

    This survey of attitude theory and research published between 1996 and 1999 covers the conceptualization of attitude, attitude formation and activation, attitude structure and function, and the attitude-behavior relation. Research regarding the expectancy-value model of attitude is considered, as are the roles of accessible beliefs and affective versus cognitive processes in the formation of attitudes. The survey reviews research on attitude strength and its antecedents and consequences, and covers progress made on the assessment of attitudinal ambivalence and its effects. Also considered is research on automatic attitude activation, attitude functions, and the relation of attitudes to broader values. A large number of studies dealt with the relation between attitudes and behavior. Research revealing additional moderators of this relation is reviewed, as are theory and research on the link between intentions and actions. Most work in this context was devoted to issues raised by the theories of reasoned action and planned behavior. The present review highlights the nature of perceived behavioral control, the relative importance of attitudes and subjective norms, the utility of adding more predictors, and the roles of prior behavior and habit. PMID:11148298

  4. Magnetic Attitude Control for Satellites in Polar or Sun-Synchronous Orbits

    OpenAIRE

    Cubas Cano, Javier; Farrahi, Assal; Pindado Carrion, Santiago

    2015-01-01

    In this work, a new law for magnetic control of satellites in near-polar orbits is presented. This law has been developed for the UMPSat-2 microsatellite, which has been designed and manufactured by Universidad Politécnica de Madrid, Madrid. The control law is a modification of the B-dot strategy that enables the satellite to control the rotation rate. Besides, the satellite?s equilibrium state is characterized by having the rotation axis perpendicular to the orbit?s plane. The control law de...

  5. Onboard Supervisor for the Ørsted Satellite Attitude Control System

    DEFF Research Database (Denmark)

    Bøgh, S.A.; Izadi-Zamanabadi, Roozbeh; Blanke, M.

    1995-01-01

    The increasing operational requirements for onboard autonomy in satellite control systems necessitates structural methods that support the design of a complete and reliable supervisory system.......The increasing operational requirements for onboard autonomy in satellite control systems necessitates structural methods that support the design of a complete and reliable supervisory system....

  6. Parasitic worms: knowledge, attitudes, and practices in Western Cote d'Ivoire with implications for integrated control.

    Directory of Open Access Journals (Sweden)

    Cinthia A Acka

    Full Text Available BACKGROUND: In the developing world where parasitic worm infections are pervasive, preventive chemotherapy is the key strategy for morbidity control. However, local knowledge, attitudes, and practices (KAP of parasitic worms are poorly understood, although such information is required for prevention and sustainable control. METHODS: We carried out KAP surveys in two rural communities of Côte d'Ivoire that were subjected to school-based and community-based research and control activities. We used qualitative and quantitative methods. The former included observations, in-depth interviews with key informants, and focus group discussions with school children and adults. Quantitative methods consisted of a structured questionnaire administered to household heads. PRINCIPAL FINDINGS: Access to clean water was lacking in both communities and only a quarter of the households had functioning latrines. There was a better understanding of soil-transmitted helminthiasis than intestinal schistosomiasis, but community-based rather than school-based interventions appeared to improve knowledge of schistosomiasis. In the villages with community-based interventions, three-quarters of household interviewees knew about intestinal schistosomiasis compared to 14% in the village where school-based interventions were implemented (P<0.001. Whereas two-thirds of respondents from the community-based intervention village indicated that the research and control project was the main source of information, only a quarter of the respondents cited the project as the main source. CONCLUSIONS/SIGNIFICANCE: Preventive chemotherapy targeting school-aged children has limitations, as older population segments are neglected, and hence lack knowledge about how to prevent and control parasitic worm infections. Improved access to clean water and sanitation is necessary, along with health education to make a durable impact against helminth infections.

  7. Parasitic Worms: Knowledge, Attitudes, and Practices in Western Côte d’Ivoire with Implications for Integrated Control

    Science.gov (United States)

    Acka, Cinthia A.; Raso, Giovanna; N'Goran, Eliézer K.; Tschannen, Andres B.; Bogoch, Isaac I.; Séraphin, Essane; Tanner, Marcel; Obrist, Brigit; Utzinger, Jürg

    2010-01-01

    Background In the developing world where parasitic worm infections are pervasive, preventive chemotherapy is the key strategy for morbidity control. However, local knowledge, attitudes, and practices (KAP) of parasitic worms are poorly understood, although such information is required for prevention and sustainable control. Methods We carried out KAP surveys in two rural communities of Côte d'Ivoire that were subjected to school-based and community-based research and control activities. We used qualitative and quantitative methods. The former included observations, in-depth interviews with key informants, and focus group discussions with school children and adults. Quantitative methods consisted of a structured questionnaire administered to household heads. Principal Findings Access to clean water was lacking in both communities and only a quarter of the households had functioning latrines. There was a better understanding of soil-transmitted helminthiasis than intestinal schistosomiasis, but community-based rather than school-based interventions appeared to improve knowledge of schistosomiasis. In the villages with community-based interventions, three-quarters of household interviewees knew about intestinal schistosomiasis compared to 14% in the village where school-based interventions were implemented (P<0.001). Whereas two-thirds of respondents from the community-based intervention village indicated that the research and control project was the main source of information, only a quarter of the respondents cited the project as the main source. Conclusions/Significance Preventive chemotherapy targeting school-aged children has limitations, as older population segments are neglected, and hence lack knowledge about how to prevent and control parasitic worm infections. Improved access to clean water and sanitation is necessary, along with health education to make a durable impact against helminth infections. PMID:21200423

  8. Smoking Prevalence and Associated Factors as well as Attitudes and Perceptions towards Tobacco Control in Northeast China

    Directory of Open Access Journals (Sweden)

    Zhijun Li

    2015-07-01

    Full Text Available Objectives: The present study aimed to investigate the prevalence of smoking and environmental tobacco smoke (ETS, the associated factors of current smoking among adults, and their attitudes and perceptions towards tobacco control. Methods: A population-based cross-sectional survey was conducted in 2012 using a self-reported questionnaire. A representative sample of adults aged 18–79 years was collected in the Jilin Province of Northeast China by a multistage stratified random cluster sampling design. Descriptive data analysis was conducted, and 95% confidence intervals (CI of prevalence/frequency were calculated to enable comparisons between the alleged differences and similarities. Multivariable logistic regressions were used to examine the risk factors associated with current smoking. Results: 21,435 adults responded to the survey (response rate: 84.9%. The overall prevalence of ever smoking, current smoking, and former smoking or smoking cessation was 39.1% (95% CI: 38.3–39.9, 31.8% (95% CI 31.1–32.6, and 7.3% (95% CI: 6.9–7.7, respectively. The proportion of ETS exposure among adult non-smokers in Jilin Province was 61.1% (95% CI: 60.1–62.1, and 23.1% (95% CI: 22.3–24.0 of the non-smokers reported daily ETS exposure. The proportion of ETS exposure at home was 33.4% (95% CI: 32.5–34.4, but the proportion of ETS exposure at restaurants was lower (6.5% (95% CI: 6.0–7.1. More than 90% of the participants had positive attitudes and perceptions towards tobacco control, but 23.2% (95% CI: 22.5–24.0 of them did not agree with the perception of “smoking is fully quit in public places”, and almost half of the adults (49.5% (95% CI: 48.7–50.3 did not agree with the perception of “hazards of low-tar cigarettes are equal to general cigarettes”. Conclusions: Smoking and exposure to ETS are prevalent among adults from the Jilin Province of Northeast China. Our findings suggest that tobacco control should be advocated in

  9. Comparative study on the knowledge-attitude-belief and practice to tobacco control between Chinese and foreign medical students in Soochow University

    OpenAIRE

    Qiao-zhu ZUO; Sun, Liang; Qian-lan XI; Wang, Li-Yan; Cen-tao LIU; Ya-na MA

    2014-01-01

    Objective: Based on the survey of the knowledge-attitude-belief and practice to tobacco control between Chinese and foreign medical students in Soochow University, the authors intended to explore the current situation, differences and influencing factors of Chinese and foreign medical students, in order to provide a reference for tobacco control policies and measures set by the Medical College of Soochow University. Methods: By stratified sampling, we selected 200 Chinese medical students and...

  10. Conceptual design of a low-cost real-time hardware-in-the-loop simulator for satellite attitude control system

    OpenAIRE

    Bayat, Farhad

    2015-01-01

    Integration of flight hardware with real-time simulation increases satellite attitude control system (ACS) reliability by providing greater test coverage through end-to-end testing in a realistic test environment. In this paper, a compound hardware and software simulator has been designed for evaluation and testing of the spacecraft ACS, placing emphasis on the real-time hardware-in-loop (RTHIL) architecture. The environment comprises both real-time control and data acquisition applications o...

  11. Rationale for an experimental test for flexible space structure attitude control

    Science.gov (United States)

    Lange, T.; Heimbold, G.; Schaefer, B.; Holzach, H.

    1985-01-01

    The problems of large flexible spacecraft control are characterized by the infinite bandwidth of structural vibrations, which cannot be accounted for in the dynamic design model. This may lead to instability even, if ideal control hardware is assumed, which can be concluded from preceding numerical investigations. Additional performance limitations are expected to occur due to hardware constraints. A laboratory experiment is proposed to investigate the key problems in more detail. The test setup requirements being defined by the idealized control system are extremely high demanding a high speed processor and special hardware component developments. The test element is a wire suspended plate being controlled by an array processor via high performance sensors and actuators. First tests on component level indicate the feasibility of the system presently being developed.

  12. Seeing race: N170 responses to race and their relation to automatic racial attitudes and controlled processing.

    Science.gov (United States)

    Ofan, Renana H; Rubin, Nava; Amodio, David M

    2011-10-01

    We examined the relation between neural activity reflecting early face perception processes and automatic and controlled responses to race. Participants completed a sequential evaluative priming task, in which two-tone images of Black faces, White faces, and cars appeared as primes, followed by target words categorized as pleasant or unpleasant, while encephalography was recorded. Half of these participants were alerted that the task assessed racial prejudice and could reveal their personal bias ("alerted" condition). To assess face perception processes, the N170 component of the ERP was examined. For all participants, stronger automatic pro-White bias was associated with larger N170 amplitudes to Black than White faces. For participants in the alerted condition only, larger N170 amplitudes to Black versus White faces were also associated with less controlled processing on the word categorization task. These findings suggest that preexisting racial attitudes affect early face processing and that situational factors moderate the link between early face processing and behavior. PMID:21452950

  13. Racism, gun ownership and gun control:biased attitudes in US whites may influence policy decisions

    OpenAIRE

    Kerry O'Brien; Walter Forrest; Dermot Lynott; Michael Daly

    2013-01-01

    OBJECTIVE: Racism is related to policies preferences and behaviors that adversely affect blacks and appear related to a fear of blacks (e.g., increased policing, death penalty). This study examined whether racism is also related to gun ownership and opposition to gun controls in US whites. METHOD: The most recent data from the American National Election Study, a large representative US sample, was used to test relationships between racism, gun ownership, and opposition to gun control in US wh...

  14. Racism, Gun Ownership and Gun Control: Biased Attitudes in US Whites May Influence Policy Decisions

    OpenAIRE

    O'Brien, Kerry S.; Forrest, Walter; Lynott, Dermot; Daly, Michael

    2013-01-01

    Objective Racism is related to policies preferences and behaviors that adversely affect blacks and appear related to a fear of blacks (e.g., increased policing, death penalty). This study examined whether racism is also related to gun ownership and opposition to gun controls in US whites. Method The most recent data from the American National Election Study, a large representative US sample, was used to test relationships between racism, gun ownership, and opposition to gun control in US whit...

  15. Attitude Control of a Single Tilt Tri-Rotor UAV System: Dynamic Modeling and Each Channel's Nonlinear Controllers Design

    Directory of Open Access Journals (Sweden)

    Juing-Shian Chiou

    2013-01-01

    Full Text Available This paper has implemented nonlinear control strategy for the single tilt tri-rotor aerial robot. Based on Newton-Euler’s laws, the linear and nonlinear mathematical models of tri-rotor UAVs are obtained. A numerical analysis using Newton-Raphson method is chosen for finding hovering equilibrium point. Back-stepping nonlinear controller design is based on constructing Lyapunov candidate function for closed-loop system. By imitating the linguistic logic of human thought, fuzzy logic controllers (FLCs are designed based on control rules and membership functions, which are much less rigid than the calculations computers generally perform. Effectiveness of the controllers design scheme is shown through nonlinear simulation model on each channel.

  16. Real Time Mode Sensing and Attitude Control of Flexible Launch Vehicle with Fiber Bragg Grating Sensor Array

    Science.gov (United States)

    Jiang, Hao

    Missiles and launch vehicles are typically slender in shape to reduce aerodynamic drag. Bending vibration occurs when a flying object with a large slenderness ratio performs pitch or yaw commands. The Inertial Measurement Unit (IMU) onboard measures the attitude and angular velocities of the deflected body as well as the rigid body motion, and in turn feeds these signals back into the control loop. Feedback of vibrating information degrades the control system stability and in the worst cases makes the system unstable. These effects become more significant as the slenderness ratio of the rocket increases. Another important challenge in launch vehicle control is created by the time-varying mass and inertia, as well as the consequent changes in modal frequencies and modal shapes of the structure as propellant is exhausted. This dissertation presents a method to correct the IMU sensors measurements with real time vibrating deflection measured by FBG sensors which have negligible mass penalty. Compared to notch filters and observers, unexpected errors induced by frequency variations, mode truncations, and un-modeled aerodynamics induced by deformation are avoided by using FBG corrected measurements. To deal with the time varying modal properties, a novel approach for the real-time estimation of mode shapes on a variable mass structure using FBG sensors is also presented in this dissertation. The method is validated by comparing estimated modal shapes to both numerical predictions and experiments on a vertical cantilever beam in which a step change in mass is introduced. The results show that the first three mode shapes of the beam can be estimated in real time using strain measurements from a FBG sensor array sampled at 1 kHz. A trajectory control system of a vertical cantilever beam is used in this dissertation to validate the method based on real-time mode sensing and FBG correction on IMU sensors. The flexible rocket dynamics and the prospective applications of this

  17. Passivity based nonlinear attitude control of the Rømer satellite

    DEFF Research Database (Denmark)

    Quottrup, Michael Melholt; Krogh-Sørensen, J.; Wisniewski, Rafal

    configuration of Wide Angle Telescopes for Cosmic Hard x-rays (WATCH), that server the dual purpose of X-ray detectors and momentum wheels. By employing passivity theory it is shown, that the satellite is a passive system. This paper shows, that global asymptotic can be obtained with a passive and an imput and...... output strictly passive system in a feedback interconnection. It is demonstrated in a simulation study that the resultant control has a potential for on-board implementation in the acquistion phase, where global stabillity of the control law is vital...

  18. Passivity Based Nonlinear Attitude Control of the Rømer Satellite

    DEFF Research Database (Denmark)

    Quottrup, Michael Melholt; Krogh-Sørensen, J.; Wisniewski, Rafal

    2001-01-01

    configuration of Wide Angle Telescopes for Cosmic Hard x-rays (WATCH), that server the dual purpose of X-ray detectors and momentum wheels. By employing passivity theory it is shown, that the satellite is a passive system. This paper shows, that global asymptotic can be obtained with a passive and an imput and...... output strictly passive system in a feedback interconnection. It is demonstrated in a simulation study that the resultant control has a potential for on-board implementation in the acquistion phase, where global stabillity of the control law is vital...

  19. Diagnosis, Remediation, and Locus of Control: Effects on Immediate and Retained Achievement and Attitudes.

    Science.gov (United States)

    Saunders-Harris, Ramona; Yeany, Russell H.

    1981-01-01

    Subjects were assessed for locus of control and experienced either: no diagnosis; diagnosis; or, diagnosis and remediation. Immediate achievement was measured twice during the experiment; retention was measured 30 days later. Findings suggest that diagnostic or diagnostic/remedial instruction is effective in increasing middle school science…

  20. Nonlinear fractional order proportion-integral-derivative active disturbance rejection control method design for hypersonic vehicle attitude control

    Science.gov (United States)

    Song, Jia; Wang, Lun; Cai, Guobiao; Qi, Xiaoqiang

    2015-06-01

    Near space hypersonic vehicle model is nonlinear, multivariable and couples in the reentry process, which are challenging for the controller design. In this paper, a nonlinear fractional order proportion integral derivative (NFOPIλDμ) active disturbance rejection control (ADRC) strategy based on a natural selection particle swarm (NSPSO) algorithm is proposed for the hypersonic vehicle flight control. The NFOPIλDμ ADRC method consists of a tracking-differentiator (TD), an NFOPIλDμ controller and an extended state observer (ESO). The NFOPIλDμ controller designed by combining an FOPIλDμ method and a nonlinear states error feedback control law (NLSEF) is to overcome concussion caused by the NLSEF and conversely compensate the insufficiency for relatively simple and rough signal processing caused by the FOPIλDμ method. The TD is applied to coordinate the contradiction between rapidity and overshoot. By attributing all uncertain factors to unknown disturbances, the ESO can achieve dynamic feedback compensation for these disturbances and thus reduce their effects. Simulation results show that the NFOPIλDμ ADRC method can make the hypersonic vehicle six-degree-of-freedom nonlinear model track desired nominal signals accurately and fast, has good stability, dynamic properties and strong robustness against external environmental disturbances.

  1. Consumer attitudes regarding internet health information and communication: Gender, locus of control, and stress implications

    Directory of Open Access Journals (Sweden)

    Joshua Fogel

    2009-01-01

    Full Text Available Los estudiantes universitarios utilizan internet para comunicarse y obtener información sobre salud. Se realizó un estudio descriptivo mediante una encuesta a 227 estudiantes para determinar si había diferencias entre aquellos que utilizan internet y el correo electrónico para informarse sobre salud y aquellos que no. Las variables dependientes fueron la Escala de Estrés Percibido y las subescalas de la Escala Multidimensional de Locus de Control de la Salud. Las variables independientes incluyeron preguntas sobre la utilización de internet para informarse o comunicarse con otros sobre salud. Se realizaron análisis para el total de la muestra y por género. En los tres ítems de comunicación, los que utilizaban internet/correo electrónico mostraron un nivel de estrés percibido significativamente más alto. No hubo diferencias entre los que usaban internet para buscar información sobre salud. Estos resultados se mantuvieron para hombres y se acercaron a la significación para las mujeres. Los que utilizan internet para obtener información sobre salud puntuaron significativamente más alto en la subescala de locus de control interno. Estos resultados se mantuvieron en los varones, mientras que para las mujeres fue significativa la subescala de control por otros poderes. Los hombres con estrés percibido se comunican por correo electrónico o internet sobre salud, mientras que las mujeres no. Respecto al uso de información sobre salud en internet, los hombres utilizan un locus de control interno y las mujeres un locus de control por otros poderes. Estos resultados son útiles para los profesionales que asesoren a universitarios con problemas de salud.

  2. AIRSHIP ATTITUDE TRACKING SYSTEM

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-liang; SHAN Xue-xiong

    2006-01-01

    The attitude tracking control problem for an airship with parameter uncertainties and external disturbances was considered in this paper. The mathematical model of the airship attitude is a multi-input/multi-output uncertain nonlinear system. Based on the characteristics of this system, a design method of robust output tracking controllers was adopted based on the upper-bounds of the uncertainties. Using the input/output feedback linearization approach and Liapunov method, a control law was designed, which guarantees that the system output exponentially tracks the given desired output. The controller is easy to compute and complement. Simulation results show that, in the closed-loop system, precise attitude control is accomplished in spite of the uncertainties and external disturbances in the system.

  3. Cassini Orbit Trim Maneuvers at Saturn - Overview of Attitude Control Flight Operations

    Science.gov (United States)

    Burk, Thomas A.

    2011-01-01

    The Cassini spacecraft has been in orbit around Saturn since July 1, 2004. To remain on the planned trajectory which maximizes science data return, Cassini must perform orbit trim maneuvers using either its main engine or its reaction control system thrusters. Over 200 maneuvers have been executed on the spacecraft since arrival at Saturn. To improve performance and maintain spacecraft health, changes have been made in maneuver design command placement, in accelerometer scale factor, and in the pre-aim vector used to align the engine gimbal actuator prior to main engine burn ignition. These and other changes have improved maneuver performance execution errors significantly since 2004. A strategy has been developed to decide whether a main engine maneuver should be performed, or whether the maneuver can be executed using the reaction control system.

  4. An Evaluation of Teachers' Attitudes and Beliefs Levels on Classroom Control in Terms of Teachers' Sense of Efficacy (The Sample of Biology Teachers in Turkey)

    Science.gov (United States)

    Kurt, Hakan

    2014-01-01

    The aim of this study is to evaluate biology teachers' attitudes and belief levels on classroom control in terms of teachers' sense of efficacy. The screening model was used in the study. The study group was comprised of 135 biology teachers. In this study, Teachers' Sense of Efficacy Scale (TSES) and The Attitudes and Beliefs on…

  5. Gender Differences in the Attitude and Strategy towards Weight Control among Government Employees in Penang, Malaysia

    OpenAIRE

    Zaitun, Y; MT, Mohd Nasir; AS Hazizi; Aina Mardiah, B; JM, Hamid Jan

    2012-01-01

    "nBackground: This was a cross-sectional study on the gender differences in weight-control behavior. The strategies used, weight status, weight satisfaction, and proportion of individuals attempting to lose weight among 233 government employees (104 men and 129 women) working in the Federal Government Building in Penang, Malaysia, were assessed."nMethods: Anthropometric indicators such as body mass index, waist-to-hip ratio, and body fat percentage were measured to determine the sub...

  6. Gender Differences in the Attitude and Strategy towards Weight Control among Government Employees in Penang, Malaysia

    OpenAIRE

    Aina Mardiah, B; Hazizi, AS; Nasir, MT Mohd; Zaitun, Y; Jan, JM Hamid

    2012-01-01

    Background: This was a cross-sectional study on the gender differences in weight-control behavior. The strategies used, weight status, weight satisfaction, and proportion of individuals attempting to lose weight among 233 government employees (104 men and 129 women) working in the Federal Government Building in Penang, Malaysia, were assessed. Methods: Anthropometric indicators such as body mass index, waist-to-hip ratio, and body fat percentage were measured to determine the subjects’ body w...

  7. Buddha as an eye opener: A link between prosocial attitude and attentional control

    OpenAIRE

    LorenzaSColzato; WeryVan Den Wildenberg; ShulanHsieh

    2010-01-01

    Increasing evidence suggests that religious practice induces systematic biases in attentional control. We used Navon's global–local task to compare attentional bias in Taiwanese Zen Buddhists and Taiwanese atheists; two groups brought up in the same country and culture and matched with respect to race, intelligence, sex, and age. Given the Buddhist emphasis on compassion for the physical and social environment, we expected a more global bias in Buddhist than in Atheist participants. In line w...

  8. Tilted wheel satellite attitude control with air-bearing table experimental results

    Science.gov (United States)

    Inumoh, Lawrence O.; Forshaw, Jason L.; Horri, Nadjim M.

    2015-12-01

    Gyroscopic actuators for satellite control have attracted significant research interest over the years, but their viability for the control of small satellites has only recently started to become clear. Research on variable speed gyroscopic actuators has long been focused on single gimbal actuators; double gimbal actuators typically operate at constant wheel spin rate and allow tilt angle ranges far larger than the ranges needed to operate most satellite missions. This research examines a tilted wheel, a newly proposed type of inertial actuator that can generate torques in all three principal axes of a rigid satellite using a spinning wheel and a double tilt mechanism. The tilt mechanism tilts the angular momentum vector about two axes providing two degree of freedom control, while variation of the wheel speed provides the third. The equations of motion of the system lead to a singularity-free system during nominal operation avoiding the need for complex steering logic. This paper describes the hardware design of the tilted wheel and the experimental setup behind both standalone and spherical air-bearing tables used to test it. Experimental results from the air bearing table are provided with the results depicting the high performance capabilities of the proposed actuator in torque generation.

  9. Autonomous Attitude Sensor Calibration (ASCAL)

    Science.gov (United States)

    Peterson, Chariya; Rowe, John; Mueller, Karl; Ziyad, Nigel

    1998-01-01

    In this paper, an approach to increase the degree of autonomy of flight software is proposed. We describe an enhancement of the Attitude Determination and Control System by augmenting it with self-calibration capability. Conventional attitude estimation and control algorithms are combined with higher level decision making and machine learning algorithms in order to deal with the uncertainty and complexity of the problem.

  10. Consumer attitudes regarding internet health information and communication: Gender, locus of control, and stress implications

    OpenAIRE

    Joshua Fogel; Solomon Israel

    2009-01-01

    Los estudiantes universitarios utilizan internet para comunicarse y obtener información sobre salud. Se realizó un estudio descriptivo mediante una encuesta a 227 estudiantes para determinar si había diferencias entre aquellos que utilizan internet y el correo electrónico para informarse sobre salud y aquellos que no. Las variables dependientes fueron la Escala de Estrés Percibido y las subescalas de la Escala Multidimensional de Locus de Control de la Salud. Las variables independientes incl...

  11. Case-based e-learning to improve the attitude of medical students towards occupational health, a randomised controlled trial

    OpenAIRE

    Smits, P.B.A.; de Graaf, L; Radon, Katja; de Boer, A G; Bos, N. R.; van Dijk, F. J. H.; Verbeek, J.H.A.M.

    2012-01-01

    Undergraduate medical teaching in occupational health (OH) is a challenge in universities around the world. Case-based e-learning with an attractive clinical context could improve the attitude of medical students towards OH. The study question is whether case-based e-learning for medical students is more effective in improving knowledge, satisfaction and a positive attitude towards OH than non-case-based textbook learning.

  12. Buddha as an eye opener: A link between prosocial attitude and attentional control

    Directory of Open Access Journals (Sweden)

    Lorenza S Colzato

    2010-09-01

    Full Text Available Increasing evidence suggests that religious practice induces systematic biases in attentional control. We used Navon’s global-local task to compare attentional bias in Taiwanese Buddhists and Taiwanese atheists; two groups brought up in the same country and culture and matched with respect to race, intelligence, sex, and age. Given the Buddhist emphasis on compassion for the physical and social environment, we expected a more global bias in Buddhist than in Atheist participants. In line with these expectations, Buddhists showed a larger global-precedence effect and increased interference from global distracters when processing local information. This pattern reinforces the idea that people's attentional processing style reflects biases rewarded by their religious beliefs.

  13. The influence of perceived behaviour control, attitude and empowerment on reported condom use and intention to use condoms among adolescents in rural Tanzania

    OpenAIRE

    Kalolo, Albino; Kibusi, Stephen Matthew

    2015-01-01

    Background Despite the declining trends of Human immunodeficiency virus (HIV) infection in Sub-Saharan Africa (SSA), unsafe sexual behaviours among adolescents still represent a public health challenge. It is important to understand factors acting at different levels to influence sexual behaviour among adolescents. This study examined the influence of perceived behaviour control, subjective norms, attitudes and empowerment on intention to use condoms and reported use of condoms among adolesce...

  14. Controle d'attitude d'un lanceur en phase atmospherique approche par applications gardiennes

    Science.gov (United States)

    Dubanchet, Vincent

    In a first phase, the modelling process underlines the presence of highly time varying parameters during the ascent, due to a fast mass variation along with propellant consumption. Linearizing the dynamical equations at six main flight instants yields linear time invariant models to be considered during control design. Each of them is to be stabilized by one control law, while respecting given specifications. The synthesis becomes even more complex when the bending modes are taken into account. Moreover, scheduling appears necessary to deal with the time variations. Indeed it is shown that no single gain setting is able to respect all the specifications along the trajectory. Furthermore, increasing complexity when modelling a whole launch vehicle pushes one to consider the model's errors and uncertainties. They represent a major issue in this study since it is asked to ensure the nominal performances in a robust fashion. Owing to their properties, guardian maps appear to be the most suitable tool to deal with such a problem of scheduling with robust performances. In light of this, the development of synthesis methods based on guardian maps is the main contribution of the project. It appears that actual state of the art in this field is focused on theoretical issues, whereas practical ones could be improved. Two approches are presented in the memoire. The first one is based on a graphical approach consisting in drawing the vanishing locus of guardian maps. A program using image analysis techniques is devised to check automatically which gain settings satisfy the constraints. The second one is based on an optimisation procedure involving guardian maps. Starting with the open loop system, the iterative process proposed ends up with a satisfactory gain setting for the closed-loop. These methods are tried and tested for the launch vehicle, with specifications from ASTRIUM-ST. Their practical application is motivated by the system complexity, the different kinds of

  15. Design of an attitude control system for spin-axis control of a 3U CubeSat

    Science.gov (United States)

    Westfall, Alexander J.

    This paper describes the design process of developing a spin-axis control system for a 3U CubeSat, a relatively small satellite. Design requires the CubeSat to de-spin after deployment and direct its antenna to track Earth nadir position. The one degree of freedom controller is developed for the TechEdSat, which is a CubeSat with a payload that allows for the assumption that rotation pitch and yaw rates are sufficiently close to zero. Satellite torqueing disturbances are modeled with reaction wheel noise for a more complete system analysis. Sensor noise is unmodeled. Frequency domain and time domain analyses are presented; the entire system bandwidth operates at 0.08 hertz with 43.2 decibels of gain and 67.7° of phase margin. During nominal operations, pointing accuracy with perfect state knowledge assumption maintains position with steady state error of 13.7 arc seconds and oscillates by 16.7 arc seconds at a rate of 0.7 mHertz. Artificial wheel noise is injected into the model causing the pointing accuracy to drop to +/- 15 arc seconds. Environmental disturbances are modeled extensively; the magnetic field torque is the worst disturbance, at 4.2e-7 Newton-meters. A 0.2 Amp˙m2 magnetorquer dumps the excess momentum every 7.75 hours and require 1.5 hours to complete. In the deployment simulation, a 1 rotation per minute spin is arrested with no angular offset in 60 seconds. Future plans include utilizing the model to build and fly a prototype reaction wheel on a future TechEdSat mission to verify modeled expectations.

  16. Smoking behaviour predicts tobacco control attitudes in a high smoking prevalence hospital: A cross-sectional study in a Portuguese teaching hospital prior to the national smoking ban

    Directory of Open Access Journals (Sweden)

    Aguiar Pedro

    2011-09-01

    Full Text Available Abstract Background Several studies have investigated attitudes to and compliance with smoking bans, but few have been conducted in healthcare settings and none in such a setting in Portugal. Portugal is of particular interest because the current ban is not in line with World Health Organization recommendations for a "100% smoke-free" policy. In November 2007, a Portuguese teaching-hospital surveyed smoking behaviour and tobacco control (TC attitudes before the national ban came into force in January 2008. Methods Questionnaire-based cross-sectional study, including all eligible staff. Sample: 52.9% of the 1, 112 staff; mean age 38.3 ± 9.9 years; 65.9% females. Smoking behaviour and TC attitudes and beliefs were the main outcomes. Bivariable analyses were conducted using chi-squared and MacNemar tests to compare categorical variables and Mann-Whitney tests to compare medians. Multilogistic regression (MLR was performed to identify factors associated with smoking status and TC attitudes. Results Smoking prevalence was 40.5% (95% CI: 33.6-47.4 in males, 23.5% (95% CI: 19.2-27.8 in females (p Conclusions Smoking prevalence was high, especially among the lower socio-economic groups. The findings showed a very high level of support for smoking bans, despite the pro-smoking environment. Most staff reported passive behaviour, despite high SHS exposure. This and the high smoking prevalence may contribute to low compliance with the ban and low participation on smoking cessation activities. Smoking behaviour had greater influence in TC attitudes than health professionals' education. Our study is the first in Portugal to identify potential predictors of non-compliance with the partial smoking ban, further emphasising the need for a 100% smoke-free policy, effective enforcement and public health education to ensure compliance and promote social norm change.

  17. Evaluation of the impact of school gardening interventions on children's knowledge of and attitudes towards fruit and vegetables. A cluster randomised controlled trial.

    Science.gov (United States)

    Hutchinson, Jayne; Christian, Meaghan Sarah; Evans, Charlotte Elizabeth Louise; Nykjaer, Camilla; Hancock, Neil; Cade, Janet Elizabeth

    2015-08-01

    Involvement of children in gardening has the potential to increase liking of fruit and vegetables (FV) and consequently, intake, but research results are mixed. School gardening led by external specialists such as the Royal Horticultural Society (RHS) could have more impact than teacher-led gardening on children's knowledge of, and attitudes towards, FV. Data from a cluster randomised controlled trial were used to compare a RHS-led school gardening intervention with a teacher-led gardening intervention amongst 7-10 year olds in 21 London schools. A short questionnaire was developed and used to identify children's knowledge and attitudes towards FV consumption before the garden intervention and 18 months afterwards. Results from multilevel regression models, both unadjusted and adjusted for baseline responses and socio-demographic factors, were reported. Attitudes to FV intake were compared between groups. Change in FV knowledge was used to predict change in FV consumption assessed using 24-hour food diaries. In comparison with the RHS-led group (n = 373), teacher-led children (n = 404) were more likely to agree they ate lots of fruit (p gardening was associated with a greater increase in the total number of vegetables recognised (p = 0.031). No other differences in improvements in attitudes, or associations between change in FV recognition and intake were found. In relation to improvements in children's recognition and attitudes towards eating FV, this trial produced limited evidence that gardening activity packages led by external specialists (RHS-led) provide additional benefits over those led by teachers trained by the RHS. Indeed, the latter were potentially more effective. PMID:25937511

  18. Attitude Control of Micro Spacecraft Without Angular Velocity Measurement%微小型航天器无角速度测量姿态控制

    Institute of Scientific and Technical Information of China (English)

    龚宜; 刘莹莹; 周军

    2013-01-01

    研究微小型航天器姿态跟踪在角速度不可测量以及控制力矩受限情况下的的控制方法.首先基于无源性原理,仅依赖姿态测量,建立一个类似PD控制的方法.为了让初始状态和角度误差始终在合理的控制范围内,对误差函数加入跳变规则,从而获得一种混合控制方法;然后利用Lyapunov原理证明了闭环系统的全局渐进稳定性;最后通过仿真与已有方法进行比较研究,验证了控制方法的有效性,即使初始速度估计误差和初始角度误差很大,依然可以控制.%The paper mainly dealt with the problem of attitude control of a micro rigid spacecraft without angular velocity measurement and under control torque constraint through a hybrid tracking controller.Based on passivity approach using only attitude measurements,a control law similar to the PD law was established; then in order to limit the inertial states and the attitude error to an appropriate bound,a switching rule was added to the error functions,so that a hybrid control law was gained.A Lyapunov approach was used to prove the global asymptotic stability of the closed loop system.The simulation results were presented to corroborate the effectiveness of this controller in contrast to another existing controller,even when the initial estimated angular velocity error and the initial angular error are large.

  19. Knowledge of HIV/AIDS, attitudes towards sexual risk behaviour and perceived behavioural control among college students in Botswana

    Directory of Open Access Journals (Sweden)

    Gabriel Faimau

    2016-12-01

    Full Text Available This study examines the knowledge of HIV/AIDS, attitudes towards risky sexual behaviour and perceived behavioural control among students in Botswana. Data were collected from 445 students randomly selected from the University of Botswana and Boitekanelo College. Hundred and seventy three males and 272 females participated in the study. The study established that although more than 90% of students correctly identified routes of HIV transmission, misconceptions regarding HIV/AIDS still exist. This includes the belief that people can be infected with HIV because of witchcraft and that only people who have sex with gay or homosexual partners can be infected with HIV. Majority of students were aware of various sexual risks. However, the percentage of students who indicated that “it is difficult to ask my partner to use a condom” was still relatively high (13.5% based on the assumption that students are supposed to know the consequences of sexual risky behaviour. It was also found that male students were 3.48 times more likely to negotiate sex than their female counterparts (OR = 3.48, 95% CI: 1.09 − 11.13 and students who were 18 years and below were more likely to negotiate sex than students above 18 years of age (OR = 2.78, 95% CI: 1.42 − 18.32. Christians are four times less likely to negotiate sex compared to non-Christians (OR = 0.219, 95% CI: 0.095 − 0.506. More than 80% of students were comfortable discussing HIV or sex and sexuality with their friends, boyfriends/girlfriends or partners but uncomfortable discussing the same issues with their parents.

  20. Pulsed Plasma Thrusters Based Attitude Control for a 2U Cubesat Mission Towards the Observation of the Lunar Horizon Glow

    Science.gov (United States)

    Rodrigo Cordova Alarcon, Jose; Low, Kay Soon; Cho, Mengu; Cihan Örger, Necmi

    2016-07-01

    The discoveries of the Apollo era arouse the interest of scientific community to research the lunar environment and the development of future missions to gather scientific data to corroborate recent theories. Particularly in lunar horizon glow, forward scattering of the sunlight by the electrically charged dust grains above the terminator region requires to be investigated further. For this reason, the data gathered by a lunar mission is valuable to improve our understanding regarding lunar environment. Nowadays, low-cost satellite platforms facilitated the access to space for university institutes and research centers worldwide. In this paper, we propose an Attitude Determination and Control System (ADCS) for a 2U CubeSat to be inserted into lunar orbit as a piggyback from a main mission. Due to the high interest to observe the light scattering by lofted dust particles in the lunar exosphere during lunar sunrise and sunset, a guidance and navigation scheme is also proposed. Through numerical simulations, we demonstrate the ADCS performance by the use of pulsed plasma thrusters (PPT) during pointing maneuvers towards lunar horizon glow. The proposed position of PPT along the satellite body contributes the orbit maintenance and the desaturation of reaction wheels. Because the maneuvers are dependent on the Sun position, a feasibility analysis were performed in orbits with different local sidereal time. Based on these results, the proposed ADCS is found suitable for 2U CubeSats to perform its maneuvers towards the accomplishment of its objectives. Additionally, we demonstrate that the increase of its mission lifetime by maintaining its orbit from PPT thrust is possible.

  1. Similar but Different: Sociocultural Attitudes towards Appearance, Body Shape Dissatisfaction, and Weight Control Behaviors among Male and Female College Students

    Science.gov (United States)

    DeBate, Rita; Lewis, Melissa; Zhang, Yan; Blunt, Heather; Thompson, Sharon H.

    2008-01-01

    Background: Although females have a higher incidence of eating disorders than males, there is evidence that among college students both males and females are vulnerable to risk factors associated with eating disorders. Purpose: To explore the relationship between sociocultural attitudes towards appearance (SCATA), body shape (dis)satisfaction…

  2. Method and apparatus for rate integration supplement for attitude referencing with quaternion differencing

    Science.gov (United States)

    Rodden, John James (Inventor); Price, Xenophon (Inventor); Carrou, Stephane (Inventor); Stevens, Homer Darling (Inventor)

    2002-01-01

    A control system for providing attitude control in spacecraft. The control system comprising a primary attitude reference system, a secondary attitude reference system, and a hyper-complex number differencing system. The hyper-complex number differencing system is connectable to the primary attitude reference system and the secondary attitude reference system.

  3. Integrated Design of Space Telescope Vibration Isolation and Attitude Control%空间相机隔振与姿态控制一体化设计

    Institute of Scientific and Technical Information of China (English)

    关新; 郑钢铁

    2013-01-01

    Mounting space telescope on spacecraft bus through vibration isolators is an effective way to reduce the Line of Sight (LOS) jitter caused by structural vibrations, which, however, will lead to non-collocated control problem. In this paper, basic principle related to vibration isolation and non-collocated control problem are investigated. An integrated design methodology for vibration isolation and attitude control is proposed. Simulation results show that LOS jitter could be significantly reduced without degrade the attitude control performance by using the proposed integrated design methodology.%为了解决星上微振动导致高分辨率遥感卫星图像质量下降的问题,研究了空间相机隔振措施及其带来的异位控制问题,提出了同时采取相机隔振与控制规律修改措施的一体化设计方法,实现了隔振性能与姿态控制性能兼备的系统方案.对算例的研究结果表明,采用相机隔振-姿态控制一体化设计方法可以在保证姿态控制性能的同时大幅降低曝光时间内空间相机的视线抖动量.

  4. Knowledge, Attitudes and Practices Relevant to Malaria Control in Remote Island Populations of Manus, Papua New Guinea

    OpenAIRE

    Ataka, Yuji; Inaoka, Tsukasa; Ohtsuka, Ryutaro

    2011-01-01

    A community-based cross-sectional survey of 262 participants in four island communities of Manus, Papua New Guinea was conducted using a structured questionnaire to examine possible factors of malaria prevalence, including education experiences, knowledge, attitudes, and preventive behaviors, in relation to antimalarial antibody titers. Bivariate and multivariate analyses revealed that micro-environmental conditions caused inter-community differences in malaria prevalence. Ninety-nine percent...

  5. Attitudes of the selfless

    DEFF Research Database (Denmark)

    Zettler, Ingo; Hilbig, B.E.

    2010-01-01

    Previous research on political orientations, which can be understood as one's left- versus right-wing attitude, has shown that some personality factors yield explanatory power. In the current work, we consider the role of altruism - a personality construct which does not exclusively map onto one of...... the broad personality dimensions typically studied. Altruism was predicted to relate to left-wing attitudes due to an overlap regarding concerns for social equality, and a discrepancy between well-known attributes of right-wingers and altruistic individuals, respectively. Moreover, altruism was...... positive association between altruism and left-wing attitudes, and altruism was found to account for substantial variance in political orientation after controlling for the HEXACO factors of personality. We conclude that altruism is an important construct which deserves attention whenever political...

  6. Platform attitude data acquisition system

    Digital Repository Service at National Institute of Oceanography (India)

    Afzulpurkar, S.

    A system for automatic acquisition of underwater platform attitude data has been designed, developed and tested in the laboratory. This is a micro controller based system interfacing dual axis inclinometer, high-resolution digital compass...

  7. ASCAL: Autonomous Attitude Sensor Calibration

    Science.gov (United States)

    Peterson, Chariya; Rowe, John; Mueller, Karl; Ziyad, Nigel

    1999-01-01

    Abstract In this paper, an approach to increase the degree of autonomy of flight software is proposed. We describe an enhancement of the Attitude Determination and Control System by augmenting it with self-calibration capability. Conventional attitude estimation and control algorithms are combined with higher level decision making and machine learning algorithms in order to deal with the uncertainty and complexity of the problem.

  8. Contingent Valuation of Residents' Attitudes and Willingness-to-Pay for Non-point Source Pollution Control: A Case Study in AL-Prespa, Southeastern Albania

    Science.gov (United States)

    Grazhdani, Dorina

    2015-07-01

    Recently, local governments in Albania have begun paying attention to management of small watershed, because there are specific boundaries and people living within a watershed basin tend to be more concerned about the basin's environmental, economic, and social development. But this natural resource management and non-point source (NPS) pollution control is still facing challenges. Albanian part of Prespa Park (AL-Prespa) is a good case study, as it is a protected wetland area of high biodiversity and long human history. In this framework, this study was undertaken, the main objectives of which were to explore: (1) the attitudes of the residents toward NPS pollution control, (2) their willingness-to-pay for improving water quality, and (3) factors affecting the residents' willingness-to-pay. Descriptive statistics, one-way ANOVA (analysis of variance), Chi-square analysis, and multivariate data analysis techniques were used. Findings strongly suggested that the residents' attitudes toward NPS pollution control in this area were positive. With the combination of two major contingent valuation methods—dichotomous choice and open-ended formats, the survey results indicated that the average yearly respondents' WTP was €6.4. The survey revealed that residents' yearly income and education level were the main factors affecting residents' willingness-to-pay for NPS pollution control in this area, and there was no significant correlation between residents' yearly income and their education level. The current study would lay a solid foundation on decision-making in further NPS pollution control and public participation through community-based watershed management policies in AL-Prespa watershed and similar areas.

  9. Attitude Control Flight Experience: Coping with Solar Radiation and Ion Engines Leak Thrust in Hayabusa (MUSES-C)

    Science.gov (United States)

    Kawaguchi, Jun'ichiro; Kominato, Takashi; Shirakawa, Ken'ichi

    2007-01-01

    The paper presents the attitude reorientation taking the advantage of solar radiation pressure without use of any fuel aboard. The strategy had been adopted to make Hayabusa spacecraft keep pointed toward the Sun for several months, while spinning. The paper adds the above mentioned results reported in Sedona this February showing another challenge of combining ion engines propulsion tactically balanced with the solar radiation torque with no spin motion. The operation has been performed since this March for a half year successfully. The flight results are presented with the estimated solar array panel diffusion coefficient and the ion engine's swirl torque.

  10. Training Changes Professionals’ Attitudes Towards Dual Diagnosis

    DEFF Research Database (Denmark)

    Pinderup, Pernille

    2016-01-01

    treatment outcome. This study tested whether providing training in dual diagnosis treatment to mental health professionals will affect their attitudes positively. Twenty-one professionals completed a questionnaire on attitudes towards working with dual diagnosis (Comorbidity Problems Perceptions......Studies have shown that mental health professionals in many cases have counterproductive attitudes towards patients with mental illnesses and comorbid substance use disorders (dual diagnosis). This is problematic because professionals’ attitudes are important for both the therapeutic alliance and...... might be a promising way to improve mental health professionals’ attitudes. Future research is needed to confirm this finding in controlled studies with more participants and a longer follow-up....

  11. Knowledge, attitudes and preventive behaviors related to dengue vector breeding control measures among adults in communities of Vientiane, capital of the Lao PDR.

    Science.gov (United States)

    Sayavong, Chanthalay; Chompikul, Jiraporn; Wongsawass, Somsak; Rattanapan, Cheerwit

    2015-01-01

    This research aimed to determine the knowledge, attitudes and preventive behaviors (KAP) of adults in relation to dengue vector control measures in the communities of Vientiane, the capital of the Lao PDR. A total of 207 respondents were actively participating in this cross-sectional descriptive study in 2011. Representatives of households were interviewed face-to-face by six trained interviewers using a structured questionnaire. KAP reliabilities of 0.89, 0.91 and 0.95 were reported in the pilot sample of 30 cases. The associations between each independent variable and prevention behavior were tested with chi-square tests. Multiple logistic regression was used to determine the factors that were significantly associated with preventive behavior while controlling for the other variables. The results revealed that 51.69% of the respondents had a high level of knowledge. More than 94% of the respondents knew that dengue fever is a dangerous communicable disease and that dengue fever is transmitted from person to person via mosquitoes. More than half (56.52%) of the participants had positive attitudes toward vector control measures, and 52.17% exhibited a high level of preventive behavior in terms of dengue vector control measures. Preventive behaviors were significantly associated with information provided from sources that included health personnel (p = 0.038) and heads of villages (p=0.031) and with knowledge levels (p < 0.001). This study suggests that proactive health education through appropriated mass media and community clean-up campaigns should strengthen and encourage community participation, particularly in terms of addressing mosquito larvae in overlooked places, such as the participants' own homes, for example, in flower vases and ant traps. PMID:25922218

  12. Criminal trial from a crime control perspective——mode, function and judge's attitude%犯罪控制视野下的刑事审判——模式、功能与法官的态度

    Institute of Scientific and Technical Information of China (English)

    刘广三

    2007-01-01

    Such ideas as upholding the advantages and merits of ex officio doctrine, gradually borrowing the fair factors of the adversary system, embodying a new-style concept of crime control and establishing the safeguarding rules and principles of the basic procedure for minimum justice criteria are macroscopical themes to which we must stick in the course of criminal trial. The effectiveness of a particular function in criminal trial in faith results from the choice of"degree" in the respect of crime control. The attitude of a criminal judge directly or otherwise exercises an influence on the trial of a case, and may even be decisive on some occasions. The concept of crime control is a barometer of the judge's attitude in criminal trial, and an indispensable component of the judge's rational attitude as well.

  13. BeppoSAX attitude operations for GRB follow up

    International Nuclear Information System (INIS)

    This poster describes the attitude dynamics software, Attitude and Orbit Control Ground Support System (AOCGSS), which was developed by TELESPAZIO and integrated in the Operations Control Centre (OCC), in order to support the on ground operations of the Attitude and Orbit Control Subsystem (AOCS). In particular its involvement during the operations performed to carry out the Gamma Ray Burst (GRB) Follow Up is described

  14. Max Launch Abort System (MLAS) Pad Abort Test Vehicle (PATV) II Attitude Control System (ACS) Integration and Pressurization Subsystem Dynamic Random Vibration Analysis

    Science.gov (United States)

    Ekrami, Yasamin; Cook, Joseph S.

    2011-01-01

    In order to mitigate catastrophic failures on future generation space vehicles, engineers at the National Aeronautics and Space Administration have begun to integrate a novel crew abort systems that could pull a crew module away in case of an emergency at the launch pad or during ascent. The Max Launch Abort System (MLAS) is a recent test vehicle that was designed as an alternative to the baseline Orion Launch Abort System (LAS) to demonstrate the performance of a "tower-less" LAS configuration under abort conditions. The MLAS II test vehicle will execute a propulsive coast stabilization maneuver during abort to control the vehicles trajectory and thrust. To accomplish this, the spacecraft will integrate an Attitude Control System (ACS) with eight hypergolic monomethyl hydrazine liquid propulsion engines that are capable of operating in a quick pulsing mode. Two main elements of the ACS include a propellant distribution subsystem and a pressurization subsystem to regulate the flow of pressurized gas to the propellant tanks and the engines. The CAD assembly of the Attitude Control System (ACS) was configured and integrated into the Launch Abort Vehicle (LAV) design. A dynamic random vibration analysis was conducted on the Main Propulsion System (MPS) helium pressurization panels to assess the response of the panel and its components under increased gravitational acceleration loads during flight. The results indicated that the panels fundamental and natural frequencies were farther from the maximum Acceleration Spectral Density (ASD) vibrations which were in the range of 150-300 Hz. These values will direct how the components will be packaged in the vehicle to reduce the effects high gravitational loads.

  15. 挠性飞行器飞轮姿态控制系统设计%Flexible Spacecraft Attitude Control System Design Using Wheels

    Institute of Scientific and Technical Information of China (English)

    耿云海; 崔祜涛; 崔海英; 杨涤

    2001-01-01

    针对带有大型太阳帆板的挠性空间飞行器动力学特性十分复杂的特点,通过合理的假设,采用单轴解耦分析姿态控制系统稳定性问题。采用极点配置法,按照刚体卫星设计系统PID参数,利用根轨迹,确定按刚体卫星参数设计的系统能使挠性空间飞行器控制系统具有渐近稳定性的充分条件;推导系统参数间的关系式,分析挠性空间飞行器主轴姿态控制系统稳定性问题。最后,通过仿真验证了系统的性能。%Because the dynamics' property of the flexible spacecraft with large solar panels is very complex, decoupling method is adopted to study the stability of the attitude control system for single axis through suitable assumption. The system PID parameters are designed using polar assignment according to rigid satellite. Then with root locus method, the sufficient condition is determined that the system designed by rigid satellite parameter ensures the stability of flexible spacecraft control system. The relation among parameters is derived and the stability of single axis flexible spacecraft attitude control system is studied. At last, the system performance is verified by simulation.

  16. Propagation of Uncertainty in Rigid Body Attitude Flows

    OpenAIRE

    Lee, Taeyoung; Chaturvedi, Nalin A.; Sanyal, Amit K.; Leok, Melvin; McClamroch, N. Harris

    2007-01-01

    Motivated by attitude control and attitude estimation problems for a rigid body, computational methods are proposed to propagate uncertainties in the angular velocity and the attitude. The nonlinear attitude flow is determined by Euler-Poincar\\'e equations that describe the rotational dynamics of the rigid body acting under the influence of an attitude dependent potential and by a reconstruction equation that describes the kinematics expressed in terms of an orthogonal matrix representing the...

  17. Integrated inertial stellar attitude sensor

    Science.gov (United States)

    Brady, Tye M. (Inventor); Kourepenis, Anthony S. (Inventor); Wyman, Jr., William F. (Inventor)

    2007-01-01

    An integrated inertial stellar attitude sensor for an aerospace vehicle includes a star camera system, a gyroscope system, a controller system for synchronously integrating an output of said star camera system and an output of said gyroscope system into a stream of data, and a flight computer responsive to said stream of data for determining from the star camera system output and the gyroscope system output the attitude of the aerospace vehicle.

  18. Attributions and Attitudes of Mothers and Fathers in Thailand.

    Science.gov (United States)

    Tapanya, Sombat

    2011-07-01

    OBJECTIVE: The present study examined similarities and differences between mothers' and fathers' attributions regarding successes and failures in caregiving situations and progressive versus authoritarian attitudes as well as correlations between mothers' and fathers' attributions and attitudes. DESIGN: Interviews were conducted with both mothers and fathers in 88 Thai families. RESULTS: Mothers and fathers did not differ in mean levels of attributions regarding successes and failures in caregiving situations or in authoritarian or progressive attitudes. Mothers' and fathers' perceived control over failure, authoritarian attitudes, progressive attitudes, and modernity of attitudes were significantly correlated. CONCLUSIONS: This work suggests high similarities between Thai mothers and fathers in their attributions and attitudes related to parenting. PMID:21927590

  19. Attitudes towards genetic testing: analysis of contradictions

    DEFF Research Database (Denmark)

    Jallinoja, P; Hakonen, A; Aro, A R;

    1998-01-01

    A survey study was conducted among 1169 people to evaluate attitudes towards genetic testing in Finland. Here we present an analysis of the contradictions detected in people's attitudes towards genetic testing. This analysis focuses on the approval of genetic testing as an individual choice and o...... scientific studies on attitudes towards genetic testing as well as in the health care context, e.g. in genetic counselling.......A survey study was conducted among 1169 people to evaluate attitudes towards genetic testing in Finland. Here we present an analysis of the contradictions detected in people's attitudes towards genetic testing. This analysis focuses on the approval of genetic testing as an individual choice and on...... the confidence in control of the process of genetic testing and its implications. Our analysis indicated that some of the respondents have contradictory attitudes towards genetic testing. It is proposed that contradictory attitudes towards genetic testing should be given greater significance both in...

  20. Gun Attitudes and Fear of Crime.

    Science.gov (United States)

    Heath, Linda; Weeks, Kyle; Murphy, Marie Mackay

    1997-01-01

    Using three studies, examined the relationship between attitudes toward guns and fear of crime. Findings indicate a connection between fear of crime and attitudes toward guns: people higher in fear of crime favored gun control. Results also established a relationship between stereotypical beliefs about gun victims and support for gun control. (RJM)

  1. Application of matrix singular value properties for evaluating gain and phase margins of multiloop systems. [stability margins for wing flutter suppression and drone lateral attitude control

    Science.gov (United States)

    Mukhopadhyay, V.; Newsom, J. R.

    1982-01-01

    A stability margin evaluation method in terms of simultaneous gain and phase changes in all loops of a multiloop system is presented. A universal gain-phase margin evaluation diagram is constructed by generalizing an existing method using matrix singular value properties. Using this diagram and computing the minimum singular value of the system return difference matrix over the operating frequency range, regions of guaranteed stability margins can be obtained. Singular values are computed for a wing flutter suppression and a drone lateral attitude control problem. The numerical results indicate that this method predicts quite conservative stability margins. In the second example if the eigenvalue magnitude is used instead of the singular value, as a measure of nearness to singularity, more realistic stability margins are obtained. However, this relaxed measure generally cannot guarantee global stability.

  2. Attitude Determination and Control System (ADCS) and Maintenance and Diagnostic System (MDS): A maintenance and diagnostic system for Space Station Freedom

    Science.gov (United States)

    Toms, David; Hadden, George D.; Harrington, Jim

    1990-01-01

    The Maintenance and Diagnostic System (MDS) that is being developed at Honeywell to enhance the Fault Detection Isolation and Recovery system (FDIR) for the Attitude Determination and Control System on Space Station Freedom is described. The MDS demonstrates ways that AI-based techniques can be used to improve the maintainability and safety of the Station by helping to resolve fault anomalies that cannot be fully determined by built-in-test, by providing predictive maintenance capabilities, and by providing expert maintenance assistance. The MDS will address the problems associated with reasoning about dynamic, continuous information versus only about static data, the concerns of porting software based on AI techniques to embedded targets, and the difficulties associated with real-time response. An initial prototype was built of the MDS. The prototype executes on Sun and IBM PS/2 hardware and is implemented in the Common Lisp; further work will evaluate its functionality and develop mechanisms to port the code to Ada.

  3. The role of beliefs and attitudes about sleep in seasonal and nonseasonal mood disorder, and nondepressed controls

    Science.gov (United States)

    Roecklein, Kathryn A.; Carney, Colleen E.; Wong, Patricia M.; Steiner, Jessica L.; Hasler, Brant P.; Franzen, Peter L.

    2014-01-01

    Background Unhelpful sleep-related cognitions play an important role in insomnia and major depressive disorder, but their role in seasonal affective disorder has not yet been explored. Therefore, the purpose of this study was to determine if individuals with seasonal affective disorder (SAD) have sleep-related cognitions similar to those with primary insomnia, and those with insomnia related to comorbid nonseasonal depression. Methods Participants (n=147) completed the Dysfunctional Beliefs and Attitudes about Sleep 16-item scale (DBAS-16) and the Structured Interview Guide for the Hamilton Depression Rating Scale, Seasonal Affective Disorder Version (SIGH-SAD), which assesses self reported sleep problems including early, middle, or late insomnia, and hypersomnia in the previous week. All participants were assessed in winter, and during an episode for those with a depressive disorder. Results Individuals with SAD were more likely to report hypersomnia on the SIGH-SAD, as well as a combined presentation of hypersomnia and insomnia on the Pittsburgh Sleep Quality Index (PSQI). The SAD group reported DBAS-16 scores in the range associated with clinical sleep disturbance, and DBAS-16 scores were most strongly associated with reports of early insomnia, suggesting circadian misalignment. Limitations Limitations include the self-report nature of the SIGH-SAD instrument on which insomnia and hypersomnia reports were based. Conclusions Future work could employ sleep- or chronobiological-focused interventions to improve clinical response in SAD. PMID:23706838

  4. Entrepreneurial Attitudes among Potential Entrepreneurs

    Directory of Open Access Journals (Sweden)

    Akhtar Ali (Corresponding author

    2011-09-01

    Full Text Available This article explores entrepreneurial attitudes among potential entrepreneurs in Pakistan. Multi-stage sampling maximized representation. Four hundred and eighty masters of business administration (MBA students (potential entrepreneurs from six public sector Pakistani universities returned completed questionnaires. Three factors emerged: entrepreneurial acceptability, entrepreneurial intentions and personal factors. Moreover, the perceptions of the potential entrepreneurs on locus of control, self efficacy, subjective norms and instrumental readiness were also analyzed. The majority of students showed generally positive attitudes towards entrepreneurship at all six universities. Overall there was a significant difference between negative and positive attitudes (negative mean 184, positive mean 284. There was also some impact of demographic variables, such as university, parental income and profession. Both genders exhibited similar attitudes at most of the sample institutions. The implications for practice and policy are discussed.

  5. Designing a New Nonlinear PID Attitude Controller for Small Quad-rotor Aircraft%小型四旋翼飞行器新型非线性PID姿态控制器设计

    Institute of Scientific and Technical Information of China (English)

    李杰; 齐晓慧; 韩帅涛

    2013-01-01

    针对小型四旋翼飞行器姿态控制问题,设计了一种新型非线性PID姿态控制器.针对传统PID的不足,通过引入两个跟踪微分器以及误差反馈的非线性组合构成非线性PID,并结合简化的小型四旋翼飞行器数学模型,提出了一种基于新型非线性PID姿态控制方法.仿真结果表明,所设计的控制器具有较强的鲁棒性、抗干扰性以及良好的滤波性能,系统具有良好的动态和稳态性能.由于保留了传统PID优点,设计简单,对实际工程具有较大的指导价值.%A new nonlinear PID attitude controller was designed to control the attitude of a small quad-rotor aircraft.Combined with the simplified mathematical model of small quad-rotor aircraft,an attitude control method was proposed by using the new nonlinear PID attitude controller.Two tracking differentiators and a nonlinear state error feedback are used to overcome the deficiency of the traditional PID controller.The simulation results indicate that our attitude controller achieves strong robustness,anti-disturbance and high filtering performances,having high-dynamic and steady-state performances.

  6. Attitude Control of Small Quad-rotor Based on Active Disturbance Rejection Control Theory%基于自抗扰理论的小型四旋翼飞行器姿态控制

    Institute of Scientific and Technical Information of China (English)

    张广昱; 袁昌盛

    2014-01-01

    针对四旋翼飞行器的强耦合性、非线性、易受外界干扰等控制难点,研究利用自抗扰控制器对四旋翼飞行器进行姿态控制的技术问题。通过牛顿-欧拉方程建立四旋翼飞行器动力学模型,将不确定性、耦合及参数摄动等干扰作为“总和干扰”,利用扩张状态观测器进行估计并动态反馈补偿,再利用非线性反馈抑制补偿残差,进行四旋翼飞行器姿态控制仿真实验。结果表明:在存在模型参数摄动和外界扰动的情况下,扩张状态观测器很好地实时估计和补偿了四旋翼飞行器的总和干扰,基于自抗扰的四旋翼飞行器姿态控制系统具有较好的动态品质、稳态精度以及较强的鲁棒性。%To solve the attitude control problem of small quad-rotor according to its complex coupling ,non-linear and serious internal/external disturbance feature ,a control scheme based on active disturbance rejection control technique is proposed .The dynamic model is established with Newton-Euler equations ,and the uncertainty , coupling and parameter perturbation are considered as total disturbance .Extended state observer is used to esti-mate and compensate the total disturbance .The non-linear state error feedback is used to restrain the compen-sate error ,and did simulation experiment of attitude control for small quad-rotor .The result of the simulation shows that the extended state observer of the active disturbance rejection control technique can estimate/com-pensate disturbance well under circumstance of parameter perturbation and disturbance .The attitude controller based on active disturbance rejection control theory shows good dynamic quality ,steady-state accuracy and strong robustness .

  7. Locus of control and contraceptive knowledge, attitude and practice among university students Locus de control y conocimiento, actitud y práctica contraceptivas entre adolescentes universitarios Lócus de controle e conhecimento, atitude e prática contraceptivas entre adolescentes universitários

    OpenAIRE

    Aline Salheb Alves; Maria Helena Baena de Moraes Lopes

    2010-01-01

    OBJECTIVE: To assess the relationship between locus of control and knowledge, attitude and practice regarding pill and condom use among university students. METHODS: The inquiry was developed in Campinas, a city in Southeastern Brazil, in 2006. A total of 295 adolescent newcomers to a public university answered a structured questionnaire and Levenson's multidimensional locus of control scale. The scores of the dimensions of locus of control were calculated and Spearman's correlation coefficie...

  8. Teaching desertification: An investigation of teacher and classroom attributes, instructional strategies, locus of control, attitudes, and self-efficacy of Namibian junior secondary school teachers

    Science.gov (United States)

    Shimwooshili Shaimemanya, Cornelia Ndahambelela

    The purpose of this study was to investigate the direct and indirect effects of teacher attributes (teaching experience, age, and science content preparation), classroom attributes (grade level, class size, and teaching resources), and instructional strategies on Namibian junior secondary school teachers' locus of control, attitudes toward desertification, and self-efficacy. A multivariate analysis of variance (MANOVA) and path analysis strategy were used to test a hypothesized causal model that expressed the relationships among these factors. Sample data were collected from 221 teachers from 218 schools representing 4 northern education regions of Namibia. Overall MANOVA results were not significant and hence no follow-up analyses were conducted. However, when the causal model was retested in the absence of 13 variables, which were incorrectly specified, MANOVA results, although still not significant, improved considerably: The p-value decreased from 28.5% to 15%. As a result., follow-up analyses were conducted at an inflated alpha level relative to this alternative model. The results indicated that science content preparation, syllabus use, and Internet use had significant influences on teachers' self-efficacy, but none of the IVs had a significant relationship with either of the other two dependent measures. A follow-up exploratory analysis was also conducted using structural equation modeling (SEM) via LISREL. The resulting LISREL model indicated that (1) age and textbook use are positive measures that determine a teacher's ability to teach desertification, (2) Internet use is a negative measure of teachers' desertification teaching ability, and (3) self-efficacy and attitudes toward desertification are measures of teachers' motivation to teach desertification, with self-efficacy as the stronger measure. Findings suggest that: (1) teachers' desertification teaching can be improved by a stronger science content background as part of teacher training programs; (2

  9. Predicting patient attitudes to asthma medication.

    OpenAIRE

    Osman, L M; Russell, I.T.; Friend, J. A.; Legge, J. S.; Douglas, J G

    1993-01-01

    BACKGROUND--Studies of patient attitudes to asthma and its control have focused on crisis action, and little attention has been paid to attitudes to regular preventive medication. It is not clear whether attitudes to regular medication are related to the degree of distress or interference with life perceived by patients as being caused by their asthma. For this reason this study examined how far dislike of medication related to dislike of other aspects of interference of asthma with daily lif...

  10. Attitudes, social representations and social attitudes

    OpenAIRE

    Farr, Robert

    1994-01-01

    This paper plays the role of the devil's advocate in relation to Colin Fraser's paper "attitudes, social representations and widespread beliefs". It argues for the alternative perspective which Colin identifies that social representations and social attitudes are epistemologically incompatible theories.

  11. Long Term Effect on Professionals’ Knowledge, Practice and Attitudes towards User Involvement Four Years after Implementing an Organisational Development Plan: A Controlled Study

    Science.gov (United States)

    Rise, Marit By; Steinsbekk, Aslak

    2016-01-01

    Background Health service organisations are increasingly implementing user involvement initiatives according to requirements from governments, such as user representation in administrational boards, better information to users, and more involvement of the users during treatment. Professionals are vital in all initiatives to enhance user involvement, and initiatives to increase involvement should influence the professionals’ practice and attitudes. The implementation of a development plan intending to enhance user involvement in a mental health hospital in Central Norway had no effect on the professionals after 16 months. The objective was therefore to investigate the long term effect on the professionals’ knowledge, practice and attitudes towards user involvement after four years. Methods This was a non-randomized controlled study including professionals from three mental health hospitals in Central Norway. A development plan intended to enhance user participation was implemented in one of the hospitals, including establishing a patient education centre and a user office, purchasing of user expertise, appointing contact professionals for next of kin, and improving of the centre’s information and the professional culture. The professionals at two other hospitals constituted the control group. All professionals were invited to answer the Consumer Participation Questionnaire (CPQ) and additional questions, at a four year interval. Results A total of 399 professionals participated (43% response rate). Comparing the changes in the intervention group with the changes in the control group, the results showed that the plan had improved some aspects of the professionals’ knowledge about the user involvement taking place in the hospital. In addition, some parts of the professionals’ practice of providing information to the service users was improved, and the development plan might have raised their awareness about insufficient involvement of next of kin

  12. Investigation of Dynamic Aerodynamics and Control of Wind Turbine Sections Under Relevant Inflow/Blade Attitude Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Naughton, Jonathan W. [University of Wyoming

    2014-08-05

    The growth of wind turbines has led to highly variable loading on the blades. Coupled with the relative reduced stiffness of longer blades, the need to control loading on the blades has become important. One method of controlling loads and maximizing energy extraction is local control of the flow on the wind turbine blades. The goal of the present work was to better understand the sources of the unsteady loading and then to control them. This is accomplished through an experimental effort to characterize the unsteadiness and the effect of a Gurney flap on the flow, as well as an analytical effort to develop control approaches. It was planned to combine these two efforts to demonstrate control of a wind tunnel test model, but that final piece still remains to be accomplished.

  13. Opportunities for Improved Chagas Disease Vector Control Based on Knowledge, Attitudes and Practices of Communities in the Yucatan Peninsula, Mexico

    OpenAIRE

    Kathryn Rosecrans; Gabriela Cruz-Martin; Ashley King; Eric Dumonteil

    2014-01-01

    BACKGROUND: Chagas disease is a vector-borne parasitic disease of major public health importance. Current prevention efforts are based on triatomine vector control to reduce transmission to humans. Success of vector control interventions depends on their acceptability and value to affected communities. We aimed to identify opportunities for and barriers to improved vector control strategies in the Yucatan peninsula, Mexico. METHODOLOGY/PRINCIPAL FINDINGS: We employed a sequence of qualitative...

  14. Spacecraft Attitude Tracking and Maneuver Using Combined Magnetic Actuators

    Science.gov (United States)

    Zhou, Zhiqiang

    2012-01-01

    A paper describes attitude-control algorithms using the combination of magnetic actuators with reaction wheel assemblies (RWAs) or other types of actuators such as thrusters. The combination of magnetic actuators with one or two RWAs aligned with different body axis expands the two-dimensional control torque to three-dimensional. The algorithms can guarantee the spacecraft attitude and rates to track the commanded attitude precisely. A design example is presented for nadir-pointing, pitch, and yaw maneuvers. The results show that precise attitude tracking can be reached and the attitude- control accuracy is comparable with RWA-based attitude control. When there are only one or two workable RWAs due to RWA failures, the attitude-control system can switch to the control algorithms for the combined magnetic actuators with the RWAs without going to the safe mode, and the control accuracy can be maintained. The attitude-control algorithms of the combined actuators are derived, which can guarantee the spacecraft attitude and rates to track the commanded values precisely. Results show that precise attitude tracking can be reached, and the attitude-control accuracy is comparable with 3-axis wheel control.

  15. 四旋翼两栖机器人姿态求解与控制%Attitude Solving and Control of an Amphibious Robot Based on Four rotor

    Institute of Scientific and Technical Information of China (English)

    李涛; 魏强; 付龙; 骆敏舟; 陈赛旋; 王美玲; 刘效; 庄晓明

    2015-01-01

    This paper mainly introduces the atti-tude solving and control of an amphibious robot based on four rotor mechanism.Firstly,it introduces the mechanism,control and sensor system,then it intro-duces the working principle that four rotor works as actuator,and by configuring rotating velocity and direc-tion of the four rotors,the robot can both fly in the air and rolling on the ground.Then,the attitude solving is carried out by using quaternion method,and then con-trol algorithm is developed as based on PID algorithm, after then corresponding simulation is implemented. Finally,experiments are presented to verify that the ro-bot can generate two motion modes,namely flying in the air and rolling on the ground,as expected.This amphibious robot enhances the environment adaptabili-ty of conventional mobile robots which just have a sin-gle motion mode.%介绍了一种基于四旋翼驱动的两栖移动机器人。首先简要介绍了该机器人的机械结构与控制及传感系统,并介绍了机器人由四旋翼机构提供动力,并通过对4个旋翼的转动速度和方向进行配置,从而实现在空中飞行或在地面滚动的原理。然后,采用四元数方法对该两栖机器人进行了姿态求解,在此基础上,基于 PID 算法开发了机器人的飞行控制算法,并进行了相应的仿真。最后通过实验验证了该两栖机器人能够实现预期的两种运动模式,即空中飞行和地面滚动。该机器人提高了传统只具有单一运动模式的移动机器人的环境适应能力。

  16. The use of real-time, hardware-in-the-loop simulation in the design and development of the new Hughes HS601 spacecraft attitude control system

    Science.gov (United States)

    Slafer, Loren I.

    1989-01-01

    Realtime simulation and hardware-in-the-loop testing is being used extensively in all phases of the design, development, and testing of the attitude control system (ACS) for the new Hughes HS601 satellite bus. Realtime, hardware-in-the-loop simulation, integrated with traditional analysis and pure simulation activities is shown to provide a highly efficient and productive overall development program. Implementation of high fidelity simulations of the satellite dynamics and control system algorithms, capable of real-time execution (using applied Dynamics International's System 100), provides a tool which is capable of being integrated with the critical flight microprocessor to create a mixed simulation test (MST). The MST creates a highly accurate, detailed simulated on-orbit test environment, capable of open and closed loop ACS testing, in which the ACS design can be validated. The MST is shown to provide a valuable extension of traditional test methods. A description of the MST configuration is presented, including the spacecraft dynamics simulation model, sensor and actuator emulators, and the test support system. Overall system performance parameters are presented. MST applications are discussed; supporting ACS design, developing on-orbit system performance predictions, flight software development and qualification testing (augmenting the traditional software-based testing), mission planning, and a cost-effective subsystem-level acceptance test. The MST is shown to provide an ideal tool in which the ACS designer can fly the spacecraft on the ground.

  17. Attitudes towards wind power

    International Nuclear Information System (INIS)

    Planning permission for the construction of a small 'farm' of wind turbines at Delabole (Deli windfarm) had been obtained and it was intended to use this source of renewable energy by generating electricity and selling it to the electrical power companies for distribution through the National Grid. It was important, therefore, to establish just what the attitudes of local residents were to the proposed development. A programme of research was discussed with the developer and it was agreed that an attitude survey would be conducted in the local area in the summer of 1990, before the turbines were erected, and before the tourist season was completely spent in order to obtain the views of visitors as well. A similar survey would then be done one year later, when the Deli windfarm was established and running. In addition, control samples would be taken at these two times in Exeter to give baseline information on attitudes toward this topic. This proposal was put to the developer and agreement was reached with him and the UK Department of Energy who were providing financial support for the research. The results of the research are reported. (author)

  18. Promoting positive attitudes to breastfeeding: the development and evaluation of a theory-based intervention with school children involving a cluster randomised controlled trial.

    Science.gov (United States)

    Giles, Melanie; Millar, Samantha; Armour, Cherie; McClenahan, Carol; Mallett, John; Stewart-Knox, Barbara

    2015-10-01

    The objective of this study was to design, implement and evaluate an intervention based on the theory of planned behaviour (TPB) to enhance young peoples' motivations to breastfeed/support a partner to breastfeed. Six semi-structured focus groups were first conducted with 48 13-14-year-olds from two schools in Northern Ireland. The salient beliefs elicited were subsequently used to design a TPB-based questionnaire that was then administered to 2021 13-14-year-old pupils (852 males; 1169 females) from 36 post-primary schools to identify the most important determinants of breastfeeding. The results were used to inform the design and implementation of an intervention package that was subsequently evaluated using a cluster randomised controlled trial involving 44 randomly selected schools across Northern Ireland. Questionnaires were administered to 18 intervention and 26 control schools at baseline and again at 1 and 6 months post-intervention to evaluate its effectiveness. Multi-level modelling was employed to analyse the data. The results revealed significant effects on women's intention to breastfeed, β = 0.208, t(1275) = 2.715, P = 0.007; attitudes, β = 0.223, t(1275) = 4.655, P < 0.001; moral attitudes, β = 0.231, t(1275) = 4.211, P < 0.001; subjective norm, β = 0.118, t(1275) = 2.521, P = 0.012; and knowledge, β = 0.109, d.f. (1275) = 7.843, P < 0.001. However, for men, the results revealed significant effects on only the construct of knowledge, β = 0.104, t(541) = 4.345, P < 0.001.The research has provided evidence to support the need for breastfeeding education in schools and has shown how a theoretical framework may be used to inform the design and evaluation of a health behaviour intervention. PMID:24028173

  19. Credit Card Misuse, Money Attitudes, and Compulsive Buying Behaviors: A Comparison of Internal and External Locus of Control (LOC) Consumers

    Science.gov (United States)

    Watson, Stevie

    2009-01-01

    This study examined attitudinal and behavioral differences between internal and external locus of control (LOC) consumers on credit card misuse, the importance of money, and compulsive buying. Using multiple analysis of variance and separate analyses of variance, internal LOC consumers were found to have lower scores on credit card misuse and…

  20. Project SUCCESS' Effects on Substance Use-Related Attitudes and Behaviors: A Randomized Controlled Trial in Alternative High Schools

    Science.gov (United States)

    Clark, Heddy Kovach; Ringwalt, Chris L.; Shamblen, Stephen R.; Hanley, Sean M.

    2011-01-01

    Using a randomized controlled effectiveness trial, we examined the effects of Project SUCCESS on a range of secondary outcomes, including the program's mediating variables. Project SUCCESS, which is based both on the Theory of Reasoned Action and on Cognitive Behavior Theory, is a school-based substance use prevention program that targets…

  1. The Effects of Diagnosis, Remediation and Locus of Control on Achievement, Retention, and Attitudes of Middle School Science Students.

    Science.gov (United States)

    Saunders, Ramona L.; Yeany, Russell H.

    Reported is a study designed to determine the effects of diagnostic testing followed by prescribed remediation on the immediate and retained science achievement of middle school students, and to determine if effects of treatment were consistent across students' race and locus of control (LOC) levels. Three intact seventh-grade science classes were…

  2. The Diabetes Intention, Attitude, and Behavior Questionnaire: evaluation of a brief questionnaire to measure physical activity, dietary control, maintenance of a healthy weight, and psychological antecedents

    Directory of Open Access Journals (Sweden)

    Traina SB

    2016-02-01

    -related self-care activities. Most subjects in Stage II were male, Caucasian, and married. Mean age was 63 years. Factor analysis revealed six psychological constructs (Behavior, Planning, Intention, Perceived Behavioral Control, Attitude, and Subjective Norm. Test–retest reliability was acceptable (≥0.70 for all scales, except Perceived Behavioral Control. Construct validity was demonstrated based on correlations with diabetes-specific items/scales and the SF-36. Known-groups validity was confirmed for Behavior, Planning, and Intention when respondents were categorized into groups that differed based on body mass index, disease severity, and HbA1c. Item scores were transformed to a 100-point scale, and minimal clinically important change estimates ranged from 6–11 points, representing the change that would be considered important to a respondent. Conclusion: The DIAB-Q is a brief, psychometrically sound, patient-reported outcome that can be used among individuals with T2DM to evaluate intention to engage in self-care behaviors. Keywords: diabetes, Theory of Planned Behavior, DIAB-Q, attitude, intention, behavior, patient-reported outcome, questionnaire

  3. Explicit- and Implicit Bullying Attitudes in Relation to Bullying Behavior

    Science.gov (United States)

    van Goethem, Anne A. J.; Scholte, Ron H. J.; Wiers, Reinout W.

    2010-01-01

    The main aim of this study was to examine whether an assessment of implicit bullying attitudes could add to the prediction of bullying behavior after controlling for explicit bullying attitudes. Primary school children (112 boys and 125 girls, M age = 11 years, 5 months) completed two newly developed measures of implicit bullying attitudes (a…

  4. Community Attitudes Toward Mass Drug Administration for Control and Elimination of Neglected Tropical Diseases After the 2014 Outbreak of Ebola Virus Disease in Lofa County, Liberia.

    Science.gov (United States)

    Bogus, Joshua; Gankpala, Lincoln; Fischer, Kerstin; Krentel, Alison; Weil, Gary J; Fischer, Peter U; Kollie, Karsor; Bolay, Fatorma K

    2016-03-01

    The recent outbreak of Ebola virus disease (EVD) interrupted mass drug administration (MDA) programs to control and eliminate neglected tropical diseases in Liberia. MDA programs treat entire communities with medication regardless of infection status to interrupt transmission and eliminate lymphatic filariasis and onchocerciasis. Following reports of hostilities toward health workers and fear that they might be spreading EVD, it was important to determine whether attitudes toward MDA might have changed after the outbreak. We surveyed 140 community leaders from 32 villages in Lofa County, Liberia, that had previously participated in MDA and are located in an area that was an early epicenter of the EVD outbreak. Survey respondents reported a high degree of community trust in the MDA program, and 97% thought their communities were ready to resume MDA. However, respondents predicted that fewer people would comply with MDA after the EVD epidemic than before. The survey also uncovered fears in the community that EVD and MDA might be linked. Respondents suggested that MDA programs emphasize to people that the medications are identical to those previously distributed and that MDA programs have nothing to do with EVD. PMID:26666700

  5. Towards an effective control programme of soil-transmitted helminth infections among Orang Asli in rural Malaysia. Part 2: Knowledge, attitude, and practices

    Directory of Open Access Journals (Sweden)

    Nasr Nabil A

    2013-01-01

    Full Text Available Abstract Background In the first part of this study, we investigated the prevalence and associated key factors of soil-transmitted helminth (STH infections among Orang Asli children in rural Malaysia; an alarming high prevalence and five key factors significantly associated with infections were reported. Part 2 of this study aims to evaluate the knowledge, attitude and practices (KAP on STH infections among Orang Asli in Peninsular Malaysia. Methods A cross-sectional study was carried out among 215 households from 13 villages in Lipis district, Pahang, Malaysia. Demographic and socioeconomic information of the participants and their KAP on STH were collected by using a pre-tested questionnaire. Results Overall, 61.4% of the participants had prior knowledge about intestinal helminths with a lack of knowledge on the transmission (28.8%, signs and symptoms (29.3% as well as the prevention (16.3%. Half of the respondents considered STH as harmful, while their practices to prevent infections were still inadequate. Significant associations between the KAP and age, gender, educational and employment status, family size, and household monthly income were reported. Moreover, significantly lower prevalence of STH infections was reported among children of respondents who wear shoes/slippers when outside the house (72.8%; 95% CI= 62.6, 80.5 vs 87.0%; 95% CI= 81.4, 91.1, wash their hands before eating (32.4%; 95% CI= 24.3, 42.2 vs 51.4%; 95% CI= 44.7, 60.1, and wash their hands after defecation (47.8%; 95% CI= 35.7, 57.1 vs 69.2%; 95% CI= 63.7, 78.7 as compared to their counterparts. Multiple logistic regression analysis indicated that the educational level of the respondents was the most important factor significantly associated with the KAP on STH among this population. Conclusion This study reveals inadequate knowledge, attitude and practices on STH infections among Orang Asli in rural Malaysia. Hence, there is a great need for a proper health education

  6. A Controlled Pre-Post Evaluation of a Computer-based HIV/AIDS Education on Students' Sexual Behaviors, Knowledge and Attitudes.

    Science.gov (United States)

    Musiimenta, Angella

    2012-01-01

    Unlike traditional approaches to sexuality and HIV education which can be constrained by the sensitive nature of the subject, Information Technology (IT) can be an innovative teaching tool that can be used to educate people about HIV. This is especially relevant to interventions targeting young people; the population group fond of using IT, and the same group that is more vulnerable to HIV/AIDS. Yet, there are significantly few empirical studies that rigorously evaluated computer-assisted school-based HIV/AIDS interventions in developing countries. The modest studies conducted in this area have largely been conducted in developed countries, leaving little known about the effectiveness of such interventions in low resource settings, which moreover host the majority of HIV/AIDS infections. This research addresses this gap by conducting a controlled pre-post intervention evaluation of the impacts of the World Starts With Me (WSWM), a computer-assisted HIV/AIDS intervention implemented in schools in Uganda. The research question was: did the WSWM intervention significantly influence students' sexual behaviors, HIV/AIDS knowledge, attitudes and self-efficacy? To address this question, questionnaires were simultaneously administering to 146 students in an intervention group (the group receiving the WSWM intervention) and 146 students in a comparison group (the group who did not receive the WSWM intervention), before (February 2009) and after the intervention (December 2009). Findings indicate that the intervention significantly improved students' HIV/AIDS knowledge, attitudes self-efficacy, sex abstinence and fidelity, but had no significant impact on condom use. The major reason for non-use of condoms was lack of knowledge about condom use which can be attributed to teachers' failure and inabilities to demonstrate condom use in class. To address this challenge, intervention teachers should be continuously trained in skills-based and interactive sexuality education. This

  7. Chaos in attitude dynamics of spacecraft

    CERN Document Server

    Liu, Yanzhu

    2013-01-01

    Attitude dynamics is the theoretical basis of attitude control of spacecrafts in aerospace engineering. With the development of nonlinear dynamics, chaos in spacecraft attitude dynamics has drawn great attention since the 1990's. The problem of the predictability and controllability of the chaotic attitude motion of a spacecraft has a practical significance in astronautic science. This book aims to summarize basic concepts, main approaches, and recent progress in this area. It focuses on the research work of the author and other Chinese scientists in this field, providing new methods and viewpoints in the investigation of spacecraft attitude motion, as well as new mathematical models, with definite engineering backgrounds, for further analysis. Professor Yanzhu Liu was the Director of the Institute of Engineering Mechanics, Shanghai Jiao Tong University, China. Dr. Liqun Chen is a Professor at the Department of Mechanics, Shanghai University, China.

  8. Attitude control system design and on-orbit performance analysis of nano-satellite—“Tian Tuo 1”

    OpenAIRE

    Ran Dechao; Sheng Tao; Cao Lu; Chen Xiaoqian; Zhao Yong

    2014-01-01

    “Tian Tuo 1” (TT-1) nano-satellite is the first single-board nano-satellite that was successfully launched in China. The main objective of TT-1 is technology demonstration and scientific measurements. The satellite carries out the significant exploration of single-board architecture feasibility validation, and it is tailored to the low-cost philosophy by adopting numerous commercial-off-the-shelf (COTS) components. The satellite is featured with three-axis stabilization control capability. A ...

  9. Evaluation of an Online Campaign for Promoting Help-Seeking Attitudes for Depression Using a Facebook Advertisement: An Online Randomized Controlled Experiment

    OpenAIRE

    Hui, Alison; Wong, Paul Wai-Ching; Fu, King-wa

    2015-01-01

    Background A depression-awareness campaign delivered through the Internet has been recommended as a public health approach that would enhance mental health literacy and encourage help-seeking attitudes. However, the outcomes of such a campaign remain understudied. Objective The main aim of this study was to evaluate the effectiveness of an online depression awareness campaign, which was informed by the theory of planned behavior, to encourage help-seeking attitudes for depression and to enhan...

  10. Weight self-regulation process in adolescence: the relationship between control weight attitudes, behaviors and body weight status

    Directory of Open Access Journals (Sweden)

    Jordi ePich

    2015-05-01

    Full Text Available Adolescents’ self-control weight behaviors were assessed (n= 1961; 12-17 years old; 2007-2008 in the Balearic Islands, Spain. The study analyzed the relationships between body weight status, body image and self-weight concern, and actual attempts to lose weight by restrained eating and/or increased exercising. In terms of regulatory focus theory (RFT, we considered that efforts to lose or to maintain weight (successful or failed would be motivated either by a promotion focus (to show an attractive body, a prevention focus (to avoid social rejection of fatness, or both. Results showed that 41% of overweight boys and 25% of obese boys stated that they had never made any attempt to lose weight, and 13% and 4% in females. Around half of overweight boys and around a quarter of obese boys stated that they were Not at all concerned about weight gain, and girls’ percentages decreased to 13% and 11% respectively. By contrast 57% of normal weight girls monitored their weight and stated that they had tried to slim at least once. Weight self-regulation in females attempted to combine diet and exercise, while boys relied almost exclusively on exercise. Apparent lack of consciousness of body weight status among overweight boys, and more important, subsequent absence of behaviors to reduce their weight clearly challenges efforts to prevent obesity. We argue that several causes may be involved in this outcome, including unconscious emotional (self-defense and cognitive (dissonance mechanisms driven by perceived social stigmatization of obesity. The active participation of social values of male and female body image (strong vs. pretty and the existence of social habituation to overweight are suggested. A better knowledge of psychosocial mechanisms underlying adolescent weight self-control may improve obesity epidemics.

  11. Weight Self-Regulation Process in Adolescence: The Relationship between Control Weight Attitudes, Behaviors, and Body Weight Status.

    Science.gov (United States)

    Pich, Jordi; Bibiloni, Maria Del Mar; Pons, Antoni; Tur, Josep A

    2015-01-01

    Adolescents' self-control weight behaviors were assessed (N = 1961; 12-17 years old; 2007-2008) in the Balearic Islands, Spain. The study analyzed the relationships between body weight status, body image, and self-weight concern, and actual attempts to lose weight by restrained eating and/or increased exercising. In terms of regulatory focus theory (RFT), we considered that efforts to lose or to maintain weight (successful or failed) would be motivated either by a "promotion focus" (to show an attractive body), or a "prevention focus" (to avoid social rejection of fatness), or both. Results showed that 41% of overweight boys and 25% of obese boys stated that they had never made any attempt to lose weight, and 13 and 4% in females. Around half of overweight boys and around a quarter of obese boys stated that they were "Not at all" concerned about weight gain, and girls' percentages decreased to 13 and 11%, respectively. By contrast, 57% of normal weight girls monitored their weight and stated that they had tried to become slim at least once. Weight self-regulation in females attempted to combine diet and exercise, while boys relied almost exclusively on exercise. Apparent lack of consciousness of body weight status among overweight boys, and more important, subsequent absence of behaviors to reduce their weight clearly challenges efforts to prevent obesity. We argue that several causes may be involved in this outcome, including unconscious, emotional (self-defense), and cognitive (dissonance) mechanisms driven by perceived social stigmatization of obesity. The active participation of social values of male and female body image (strong vs. pretty), and the existence of social habituation to overweight are suggested. A better knowledge of psychosocial mechanisms underlying adolescent weight self-control may improve obesity epidemics. PMID:26284248

  12. Instructional strategies to improve women's attitudes toward science

    Science.gov (United States)

    Newbill, Phyllis Leary

    Although negative attitudes toward science are common among women and men in undergraduate introductory science classes, women's attitudes toward science tend to be more negative than men's. The reasons for women's negative attitudes toward science include lack of self-confidence, fear of association with social outcasts, lack of women role models in science, and the fundamental differences between traditional scientific and feminist values. Attitudes are psychological constructs theorized to be composed of emotional, cognitive, and behavioral components. Attitudes serve functions, including social expressive, value expressive, utilitarian, and defensive functions, for the people who hold them. To change attitudes, the new attitudes must serve the same function as the old one, and all three components must be treated. Instructional designers can create instructional environments to effect attitude change. In designing instruction to improve women's attitudes toward science, instructional designers should (a) address the emotions that are associated with existing attitudes, (b) involve credible, attractive women role models, and (c) address the functions of the existing attitudes. Two experimental instructional modules were developed based on these recommendations, and two control modules were developed that were not based on these recommendations. The asynchronous, web-based modules were administered to 281 undergraduate geology and chemistry students at two universities. Attitude assessment revealed that attitudes toward scientists improved significantly more in the experimental group, although there was no significant difference in overall attitudes toward science. Women's attitudes improved significantly more than men's in both the experimental and control groups. Students whose attitudes changed wrote significantly more in journaling activities associated with the modules. Qualitative analysis of journals revealed that the guidelines worked exactly as predicted

  13. Rationale, design and methods for a staggered-entry, waitlist controlled clinical trial of the impact of a community-based, family-centred, multidisciplinary program focussed on activity, food and attitude habits (Curtin University’s Activity, Food and Attitudes Program—CAFAP among overweight adolescents

    Directory of Open Access Journals (Sweden)

    Straker Leon M

    2012-06-01

    Full Text Available Abstract Background Current estimates place just under one quarter of adolescents in Australia as overweight or obese. Adolescence has been identified as a critical period for the development of obesity, yet despite this recognition, there is limited systematic research into or evaluation of interventions for overweight adolescents. Reviews have concluded that there is a substantive evidence gap for effective intervention, but physical activity, lifestyle change and family involvement have been identified as promising foci for treatment. Methods This paper reports on the development of a staggered-entry, waitlist controlled clinical trial to assess the impact of a multidisciplinary intervention aiming to change the poor health trajectory of overweight adolescents and help them avoid morbid obesity in adulthood—Curtin University’s Activity, Food and Attitudes Program (CAFAP. 96 adolescents, aged 11–16 years, and parents, will attend twice weekly during an 8 week intensive multidisciplinary program with maintenance follow-up focussed on improving activity, food and attitude habits. Follow-up assessments will be conducted immediately after completing the intensive program, and at 3, 6 and 12 months post intensive program. Main outcomes will be objectively-measured physical activity, sedentary behaviour and activity behaviours; food intake (measured by 3 day diary and food behaviours; body composition, fitness and physical function; mental and social well-being (quality of life, mood and attitudes, and family functioning. Discussion This trial will provide important information to understand whether a community based multidisciplinary intervention can have short and medium term effects on activity and food habits, attitudes, and physical and mental health status of overweight adolescents. Trial registration Australian New Zealand Clinical Trials Registry ACTRN12611001187932.

  14. 挠性航天器姿态机动的变论域自整定模糊PID控制%Variable Universe Self-tuning Fuzzy PID Controller of Attitude Maneuver for Flexible Spacecraft

    Institute of Scientific and Technical Information of China (English)

    魏凤美; 赵育善; 师鹏

    2014-01-01

    建立了带有太阳翼的挠性航天器的姿态动力学模型,应用改进的罗德里格参数来描述姿态运动学模型。针对挠性航天器模型参数不确定性和环境干扰等问题,提出了变论域自整定模糊比例积分微分(PID)控制方案,构建了计算简单并且可以达到控制精度的伸缩因子。基于Matlab/Simulink进行了仿真验证,结果表明,变论域自整定模糊 PID 控制响应速度比传统PID控制、模糊PID控制快350 s,且无超调,不仅能够使航天器完成对目标姿态的机动,而且能够有效地抑制挠性太阳翼的振动。%The attitude dynamical equations of flexible spacecraft with solar panels were established, and the attitude kinematic equations were described by modified Rodrigues parameters (MRPs ) in order to prevent the singularity of the large angle maneuver. A variable universe self-tuning fuzzy PID controller was proposed for model uncertainties and environmental disturbances. A new shrinkable factor was designed, and it was easy to calculate and could achieve the accuracy. Numerical simulation based on Matlab/Simulink shows that the response of the variable universe self-tuning fuzzy PID controller are 350 s faster than that of the conventional PID and fuzzy PID controllers, and that it has no overshoot and can realize the effective control of attitude maneuver and effectively suppress the vibration of solar panels.

  15. Consumer attitude toward food irradiation

    International Nuclear Information System (INIS)

    Consumer attitudes toward food irradiation were evaluated. The influence of educational efforts on consumer concern for the safety of irradiated products and willingness to buy irradiated foods were measured. Demographic and psychological factors were studied in relation to attitudes. An educational leaflet describing current scientific information regarding the safety, advantages, and disadvantages of food irradiation was developed and used in two studies evaluating attitude change. In the first study, attitude change among two groups of consumers with different philosophic orientations was measured. In a second study, the effectiveness of an educational leaflet received through the mail and a poster display were examined. In a third study response to food irradiation was related to value hierarchy, locus of control, innovativeness, and demographic parameters. Initially, subjects showed a higher concern for other areas of food safety, particularly the use of chemicals and sprays on food, than toward food irradiation. After educational efforts, conventional consumers expressed minor concern toward irradiation whereas ecologically sensitive alternative consumers obtained from a food cooperative expressed major concern. A knowledgeable discussion leader lowered irradiation concern among conventional consumers. In contrast, concern among alternative consumers did not diminish when given the opportunity to discuss safety issues with a knowledgeable person

  16. Effect of Attitude of Partner on Sex Role Attitudes.

    Science.gov (United States)

    Snodgrass, Sara E.; Muneses, Tricia

    This study examined whether the expressed attitudes of a male or female companion might influence a woman to report sex-role attitudes more conforming to her companion's attitudes. Forty female college students were paired with a male or female confederate who expressed either sexist attitudes or feminist attitudes. The pairs read and discussed a…

  17. Consumer Attitude Towards Brand Extensions : An Integrative model and research propositions

    OpenAIRE

    Czellar, Sandor

    2002-01-01

    The paper proposes an integrative model of the antecedents and consequences of brand extension attitude based on the dominant cognitive paradigm. The four key processes of the model are : (1) the perception of fit, (2) the formation of primary attitudes towards the extension, (3) the link between extension attitude and marketplace behaviour and (4) the reciprocal effect of brand extension attitude on parent brand/extension category attitude. Moderator and control variables of these processes ...

  18. A Raspberry Pi-Based Attitude Sensor

    CERN Document Server

    Sreejith, A G; Sarpotdar, Mayuresh; Mohan, Rekhesh; Nayak, Akshata; Safonova, Margarita; Murthy, Jayant

    2014-01-01

    We have developed a lightweight low-cost attitude sensor, based on a Raspberry Pi, built with readily available commercial components. It can be used in experiments where weight and power are constrained, such as in high- altitude lightweight balloon flights. This attitude sensor will be used as a major building block in a closed-loop control system with driver motors to stabilize and point cameras and telescopes for astronomical observations from a balloon-borne payload.

  19. Attitude-adjusting table for neutron monochromator

    International Nuclear Information System (INIS)

    The neutron monochromator attitude-adjusting table is one of the mechanical components for most monochromatic neutron scattering spectrometer. It is mainly used for mounting crystal monochromator, and getting monochromatic neutron by adjusting the attitude of monochromator remotely. The table has a compact volume and five adjusting axes with high resolution. It combines optic mechanical electronic technique with computer control technique. This device will be applied to the neutron residual stress spectrometer on CARR firstly. (authors)

  20. A Raspberry Pi-Based Attitude Sensor

    Science.gov (United States)

    Sreejith, A. G.; Mathew, Joice; Sarpotdar, Mayuresh; Mohan, Rekhesh; Nayak, Akshata; Safonova, Margarita; Murthy, Jayant

    We have developed a lightweight low-cost attitude sensor, based on a Raspberry Pi, built with readily available commercial components. It can be used in experiments where weight and power are constrained, such as in high-altitude lightweight balloon flights. This attitude sensor will be used as a major building block in a closed-loop control system with driver motors to stabilize and point cameras and telescopes for astronomical observations from a balloon-borne payload.

  1. 基于输出反馈的编队卫星姿态同步和跟踪控制%Attitude Synchronization and Tracking Control of Formation Flying Satellites by Output Feedback

    Institute of Scientific and Technical Information of China (English)

    郭海波; 曹喜滨; 张世杰; 张安慧; 陈健; 王峰

    2011-01-01

    研究了卫星编队无角速度测量信息且采用局部信息交互时的姿态协同控制问题.以四元数为姿态描述手段,采用超前滤波方法重构星体绝对和相对角速度信息,设计了基于输出反馈的分散姿态同步和跟踪控制器.利用Barbalat引理和代数图论等对闭环系统的全局渐近稳定性进行了理论分析和证明.以六星编队为背景的数值仿真进一步验证了算法的有效性.%The coordinated attitude control via local information exchange for a group of satellites without angular velocity measurements is considered. A decentralizcd output feedback control law is developed by using quaternions only to guarantee attitude synchronization and tracking. Lead filters are adopted to estimate the unmcasured absolute and relative angular velocities necessary for the coordinated control. The global asymptotic stability for the closed-loop system is shown by applying algebraic graph theory and the Barbalat's Lemma. Simulation results of six formation flying satellites further demonstrate the effectiveness of the proposed control law.

  2. Towards an effective control programme of soil-transmitted helminth infections among Orang Asli in rural Malaysia. Part 2: Knowledge, attitude, and practices

    OpenAIRE

    Nasr Nabil A; Al-Mekhlafi Hesham M; Ahmed Abdulhamid; Roslan Muhammad Aidil; Bulgiba Awang

    2013-01-01

    Abstract Background In the first part of this study, we investigated the prevalence and associated key factors of soil-transmitted helminth (STH) infections among Orang Asli children in rural Malaysia; an alarming high prevalence and five key factors significantly associated with infections were reported. Part 2 of this study aims to evaluate the knowledge, attitude and practices (KAP) on STH infections among Orang Asli in Peninsular Malaysia. Methods A cross-sectional study was carried out a...

  3. The effect of motivational interviewing on oral healthcare knowledge, attitudes and behaviour of parents and caregivers of preschool children: an exploratory cluster randomised controlled study

    OpenAIRE

    Naidu, Rahul; Nunn, June; Irwin, Jennifer D.

    2015-01-01

    Background Motivational Interviewing (MI) has been used across primary healthcare and been shown to be effective in reducing the prevalence of early childhood caries (ECC) in preschool children. This study aimed to compare the effect of MI, in contrast to traditional dental health education (DHE), on oral health knowledge, attitudes, beliefs and behaviours among parents and caregivers of preschool children in Trinidad. Method The design of this exploratory study included a cluster randomised ...

  4. 基于模糊PID方法的盾构掘进姿态控制研究%Research on Shield Boring Attitude Control Based on Fuzzy PID Algorithm

    Institute of Scientific and Technical Information of China (English)

    龚国芳; 洪开荣; 周天宇; 侯典清; 王林涛

    2014-01-01

    针对盾构掘进过程中姿态主要依赖操作人员施工经验手工调整、掘进轨迹精度主要依赖人员熟练性的情况,提出基于双闭环反馈自动控制盾构掘进轨迹的方法,通过主反馈实现掘进斜度的实时更新,局部反馈实现液压缸的速度控制。分析表明,局部反馈精度决定了预调偏差大小,在掘进轨迹控制中至为关键,因此以球铰支撑推进系统为例分析单环掘进前后液压缸的几何关系,推导左右推进液压缸速度关于掘进斜度、掘进速度的数学解析式,采用AMESim和MATLAB联合仿真工具搭建了推进速度控制的模糊PID模型,仿真分析非均载荷下推进液压缸的速度控制,并以盾构模拟推进试验台为例进行推进速度控制试验。结果表明:基于模糊PID控制策略的推进液压缸速度控制可实现较准确的盾构掘进轨迹,为盾构失准问题的进一步解决提供了理论基础和现实依据。%Considering the fact that the attitude of shield during the boring process is mainly controlled by manual adjustment according to personal experience and that the precision of shield boring trajectory mainly depends on personal proficiency,the authors propose the automatic shield attitude control method based on dual closed-loop feedback.The automatic shield attitude control method proposed contains a main-loop feedback that updates the tunneling trajectory and a local feedback that controls the velocity of the thrust cylinders.Succedent analysis shows that the local-feedback control is crucial.Therefore,the authors analyze the geometric relation of hydraulic cylinders before and after one-ring boring based on a spherical-hinge support thrust system,and deduce the mathematical expression of shield attitude and velocity of thrust cylinders on the left and right sides.The authors achieve the simulation of the velocity control system based on fuzzy PID by using AMEsim and MATLAB software

  5. Language Learners' Acculturation Attitudes

    Science.gov (United States)

    Rafieyan, Vahid; Orang, Maryam; Bijami, Maryam; Nejad, Maryam Sharafi; Eng, Lin Siew

    2014-01-01

    Learning a language involves knowledge of both linguistic competence and cultural competence. Optimal development of linguistic competence and cultural competence, however, requires a high level of acculturation attitude toward the target language culture. To this end, the present study explored the acculturation attitudes of 70 Iranian…

  6. Individual Attitudes Towards Trade

    DEFF Research Database (Denmark)

    Jäkel, Ina Charlotte; Smolka, Marcel

    2013-01-01

    Using the 2007 wave of the Pew Global Attitudes Project, this paper finds statistically significant and economically large Stolper-Samuelson effects in individuals’ preference formation towards trade policy. High-skilled individuals are substantially more pro-trade than low-skilled individuals......-Ohlin model in shaping free trade attitudes, relative to existing literature....

  7. Measuring Attitude Functions.

    Science.gov (United States)

    Anderson, Deborah S.; Kristiansen, Connie M.

    1990-01-01

    Discusses the Attitude Functions Inventory (AFI), which assesses the extent to which a person's attitude fulfills each of four psychological functions. Reports findings of a study, involving 249 undergraduates, that tested the construct validity of the AFI. Suggests that the AFI provides conceptually meaningful measures of the functions of…

  8. Pornography and Attitude Change

    Science.gov (United States)

    Wallace, Douglas H.; Wehmer, Gerald

    1971-01-01

    The results indicate that a voluntary three hour exposure to erotic pictures, some of which have been defined as being legally obscene," does not lead to a change in a person's attitudes toward such materials or in attitudes toward their censorship. (Author)

  9. Adolescent Attitudes about Rape.

    Science.gov (United States)

    Kershner, Ruth

    1996-01-01

    A very significant problem in society is adolescent rape victimization and the growing number of adolescent perpetrators. This paper examines adolescent attitudes about rape in order to develop curricular materials. It is found that adolescents exhibit conservative attitudes about gender roles, general rape myths, and victim issues. (Author)

  10. Hierarchical Models of Attitude.

    Science.gov (United States)

    Reddy, Srinivas K.; LaBarbera, Priscilla A.

    1985-01-01

    The application and use of hierarchical models is illustrated, using the example of the structure of attitudes toward a new product and a print advertisement. Subjects were college students who responded to seven-point bipolar scales. Hierarchical models were better than nonhierarchical models in conceptualizing attitude but not intention. (GDC)

  11. Boundary control in the attitude maneuvering of tethered space solar power satellite%绳系太阳能发电卫星姿态机动的边界控制

    Institute of Scientific and Technical Information of China (English)

    周荻; 范继祥

    2013-01-01

    针对绳系太阳能发电卫星大角度回转机动时太阳能板的振动抑制问题,提出了主姿态控制和边界最优主动振动控制相结合的复合控制方法.基于Lyapunov方法设计的主姿态控制器不但能够使卫星完成姿态机动,而且能够以太阳能板根部的弯曲力矩作为反馈信息,通过改变太阳能板根部的控制力矩来保证挠性结构振动的衰减性.考虑到绳的单侧饱和非线性特性,用非二次型性能指标代替传统的二次型性能指标设计的边界最优控制器能够进一步抑制挠性结构的振动.设计的同时证明了系统的稳定性及控制器的最优性.将该复合控制方法用于绳系卫星大角度单轴回转机动的仿真研究,仿真结果验证了该控制策略的有效性.%A composite control approach is proposed for vibration suppression of tethered space solar power satellite (SSPS) during large-angle slewing maneuver by combining main attitude control and active vibration control based on boundary optimal method. The mathematical description for the slewing motion of tethered SSPS is presented. Lyapunov method is applied in the design of the main controller, which is able not only to implement attitude maneuvering of tethered satellite but also suppress the relatively large amplitude vibration of the flexible solar panel by changing the control torque acting on the root of the solar panel. Taking the unilateral and saturated nonlinearity of the flexible tether into account, the boundary optimal controller, acting on the corners of flexible solar panels, is designed by substituting the conventional quadratic performance function with nonquadratic performance function and is desired, as a compensate control system, for the further vibration suppression. In the design process, the stability of the vibration control system and the optimality of the controller are proved. Simulation results demonstrate the proposed control strategy can significantly

  12. Attitudes Towards Immigration

    DEFF Research Database (Denmark)

    Malchow-Møller, Nikolaj; Roland Munch, Jakob; Schroll, Sanne;

    2006-01-01

    In this paper, we re-examine the role of economic self-interest in shaping people's attitudes towards immigration, using data from the European Social Survey 2002/2003. Compared to the existing literature, there are two main contributions of the present paper. First, we develop a more powerful test...... of the hypothesis that a positive relationship between education and attitudes towards immigration reflects economic self-interest in the labour market. Second, we develop an alternativeand more direct test of whether economic self-interest mattersfor people's attitudes towards immigration. We find...

  13. Attitudes Towards Immigration

    DEFF Research Database (Denmark)

    Malchow-Møller, Nikolaj; Munch, Jakob Roland; Schroll, Sanne;

    In this paper, we re-examine the role of economic self-interest in shaping people’s attitudes towards immigration, using data from the European Social Survey 2002/2003. Compared to the existing literature, there are two main contributions of the present paper. First, we develop a more powerful test...... of the hypothesis that a positive relationship between education and attitudes towards immigration reflects economic self-interest in the labour market. Second, we develop an alternative and more direct test of whether economic self-interest matters for people’s attitudes towards immigration. We find...

  14. Active Vibration Control of Tethered Solar Power Satellite during Attitude Maneuvering%绳系太阳能发电卫星姿态机动的主动振动控制

    Institute of Scientific and Technical Information of China (English)

    周荻; 范继祥

    2012-01-01

    针对绳系太阳能发电卫星大角度回转机动时太阳能板的振动抑制问题,提出了主姿态控制和基于绳中张力的主动振动控制技术相结合的复合控制方法.建立了绳系太阳能发电卫星系统的动力学方程,并基于任务函数控制算法设计了主控制器保证卫星姿态的渐近稳定和挠性结构振动的衰减性;考虑到绳的非线性特性,基于任务函数控制算法设计了绳系卫星系统的主动振动抑制辅助控制器来抑制挠性结构的振动.设计的同时证明了系统的稳定性.将该方法应用于绳系卫星的大角度单轴回转机动的仿真研究,结果表明:该方法不仅能够使绳系卫星完成姿态机动,而且能够有效地抑制太阳能板的振动.%For vibration suppression of tethered Solar Power Satellite (SPS) during large-angle slewing maneuver, a composite control method is proposed by combining main attitude control with active vibration control based on tether tension. Dynamics equations for the slewing motion of tethered SPS are presented. A mission Function (MF) Control Algorithm is applied to design these two controllers. The main controller is able not only to implement attitude maneuvering of tethered satellite but also suppress the relatively large amplitude vibration of the flexible solar panel. The compensate control system acting on the comers of flexible solar panels is required for the further vibration suppression, and the nonlinearity of the flexible tether is taken into account in the controller design. In the design process, the stability of the vibration control system is proved. Simulation results demonstrate that the proposed approach can significantly suppress the vibration of the flexible solar panel during and after the maneuver operation.

  15. Does exposure to music videos predict adolescents’ sexual attitudes?

    NARCIS (Netherlands)

    J.W.J. Beentjes; R.P. Konig

    2013-01-01

    This study investigates whether exposure to music videos predicts adolescents' sexual attitudes when controlled for relevant characteristics of individuals and their social environment. Sexual attitudes are related to their music video use (i.e. exposure to music videos, peer group talk about music

  16. Does exposure to music videos predict adolescents' sexual attitudes?

    NARCIS (Netherlands)

    Beentjes, J.W.J.; Konig, R.P.

    2013-01-01

    This study investigates whether exposure to music videos predicts adolescents' sexual attitudes when controlled for relevant characteristics of individuals and their social environment. Sexual attitudes are related to their music video use (i.e. exposure to music videos, peer group talk about music

  17. Explicit- and implicit bullying attitudes in relation to bullying behavior

    NARCIS (Netherlands)

    A.A.J. van Goethem; R.H.J. Scholte; R.W. Wiers

    2010-01-01

    The main aim of this study was to examine whether an assessment of implicit bullying attitudes could add to the prediction of bullying behavior after controlling for explicit bullying attitudes. Primary school children (112 boys and 125 girls, M age = 11 years, 5 months) completed two newly develope

  18. Explicit- and Implicit Bullying Attitudes in Relation to Bullying Behavior

    NARCIS (Netherlands)

    Goethem, A.A.J. van; Scholte, R.H.J.; Wiers, R.W.H.J.

    2010-01-01

    The main aim of this study was to examine whether an assessment of implicit bullying attitudes could add to the prediction of bullying behavior after controlling for explicit bullying attitudes. Primary school children (112 boys and 125 girls, M age = 11 years, 5 months) completed two newly develope

  19. Variable Attitude Test Stand

    Data.gov (United States)

    Federal Laboratory Consortium — The Variable Attitude Test Stand designed and built for testing of the V-22 tilt rotor aircraft propulsion system, is used to evaluate the effect of aircraft flight...

  20. Attitudes to audit

    OpenAIRE

    Waters, W. H. R.; Kelly, J.; Lunn, J E

    1983-01-01

    An exercise in audit was arranged jointly by the Local Medical Committee and the Royal College of General Practitioners in the Doncaster area. This was followed up by a questionnaire enquiring about attitudes to the audit.

  1. Attitudes and Beliefs in Advertising

    OpenAIRE

    Pohořelá, Denisa

    2011-01-01

    Bachelor thesis of name „Attitudes and Belief in Advertising“ considers determination of general attitude towards advertising and testing of factors which effect advertising message´s consignee. Belief in advertising has character of general attitude or attitude towards brand. My bachelor abstract recognizes particulary these general attitudes. Working factors in advertising are: relation, politics, sex, symbolism, family. For this purpose questionnaire research was chosen. A part ...

  2. Consumers' attitudes towards sonic logos

    OpenAIRE

    Shi, Qichao

    2012-01-01

    Sonic logos are increasingly being used as a way of sonic branding in marketing activities. Scholars have acknowledged the benefits of sonic logos, such as communicating brand attributes to consumers. However, studies about consumers’ attitudes towards sonic logos are scarce. This paper examined consumers’ attitudes towards sonic logos, particularly how cognitive and affective elements correlated with such attitudes, whether such attitudes had correlations with consumers’ attitudes towards th...

  3. Attitudes Toward Single Parenthood

    OpenAIRE

    Pećnik, Ninoslava; Raboteg-Šarić, Zora

    2010-01-01

    Changes in the family structure produce different social reactions, and the negative attitude of society towards single parent families can generate social vulnerability of this group. (The lack of) understanding of the environment influences not only the behaviour of other persons toward single parents and their children, but also their attitudes and personal experience of single parenthood. In order to improve the insight into the experience of new forms of family in our society, a survey o...

  4. Consumers’ Attitude towards Advertising

    OpenAIRE

    Uchenna Cyril Eze; Chai Har Lee

    2012-01-01

    Advertising is a growing business and with advances in the Internet technology, the dynamics and landscape ofthe business has changed as well. Prior findings on consumers’ attitude towards advertising are mixed. Thispaper is an attempt to examine young adults’ attitude towards advertising. We conceptualized a framework toexamine the influence of six independent variables namely consumer manipulation, product information,hedonic/pleasure, economic condition, social integration, and materialism...

  5. Student attitudes to entrepreneurship

    OpenAIRE

    Christine K. VOLKMANN; Kim Oliver TOKARSKI

    2009-01-01

    This study on Student Attitudes to Entrepreneurship investigates the image which university students have of entrepreneurs and entrepreneurship. It is an initial exploratory/empirical study, which looks at the situation in Germany, Romania, Latvia, Italy and Austria. The study, based on questionnaires, shows that there are significant differences but also common features to the image of entrepreneurship and attitudes to it in the five countries. It is interesting to note that the students pol...

  6. Attitudes towards documentary soundstracks

    DEFF Research Database (Denmark)

    Have, Iben

    2010-01-01

    Musical experience is often related to an emotional and imaginative engagement of the listener. Discourses of journalistic documentaries relate primarily to inferential knowledge systems in which the uses of background music as a communicative device become an object of epistemological critique....... By listening to different voices - primarily from four focus group interviews - the article will discuss attitudes towards musical soundtracks in documentaries, attitudes being negotiated between emotional immersion and critical reflection, with the concept of manipulation as an underlying theme. In the end...

  7. Attitudes towards immigration

    DEFF Research Database (Denmark)

    Malchow-Møller, Nikolaj; Munch, Jakob Roland; Skaksen, Jan Rose;

    2008-01-01

    Using the European Social Survey 2002/3, we develop a new test of whether economic self-interest influences people's attitudes towards immigration, exploiting that people have widely different perceptions of the consequences of immigration......Using the European Social Survey 2002/3, we develop a new test of whether economic self-interest influences people's attitudes towards immigration, exploiting that people have widely different perceptions of the consequences of immigration...

  8. Roll stabilizer bars' design for solar-sail spacecraft attitude control%太阳帆航天器姿态控制滚转轴稳定机设计

    Institute of Scientific and Technical Information of China (English)

    马鑫; 杨萱; 杨辰; 钱航; 郑龙飞

    2014-01-01

    Two kinds of solar-sail attitude control mechanism were described in this paper, one was the centroid offet class, the other was the sail plane rotating class. Advantages and disadvantages of these two kinds of attitude control mechanism were analyzed. An attitude control roll stabilizer barsis was designed which was suitable for a kind of square solar sail which had extension boom and square sail surface. The boom's length of roll stabilizer bars is the key parameter, it was optimized under some constraints such as: configuration design, material strength, structural strength, quality optimization and control accuracy, it was calculated and verified through geometry relations and nonlinear static finite element simulation. The simulation result wa s 1.2 m. The rotate speed limit was obtained by power and speed relation formula according to the result of the boom's length, which was 20.83 (.)/s. In this paper, an optimization design idea of roll stabilizer bars boom's length was given. The calculation and simulation results provide the key design parameters and design conditions for the solar-sail spacecraft attitude control system design, and the optimization results have reference value for practical engineering applications.%针对一种具体的由支撑臂支撑、方形帆面形式的太阳帆航天器,介绍了质心偏移类、帆面转动类两大类姿态控制机构,并分析了其优缺点,对其适用的姿态控制滚转轴稳定机进行了设计。在构型设计、材料强度、结构强度、质量优化、控制精度等设计约束条件下,围绕滚转轴稳定机转杆长度关键设计参数,通过分析长度角度制约关系、几何计算、帆面有限元非线性静态建模仿真验证、伸展臂弯曲受力有限元建模仿真验证给出了转杆长度值的优化设计结果为1.2 m,并以此为依据结合功率、转速公式计算选取了合理的极限转速取值为20.83(。)/s。给出了一种滚转轴稳定

  9. Effects of Brain-Based Learning Approach on Students' Motivation and Attitudes Levels in Science Class

    Science.gov (United States)

    Akyurek, Erkan; Afacan, Ozlem

    2013-01-01

    The purpose of the study was to examine the effect of brain-based learning approach on attitudes and motivation levels in 8th grade students' science classes. The main reason for examining attitudes and motivation levels, the effect of the short-term motivation, attitude shows the long-term effect. The pre/post-test control group research model…

  10. The Effects of an Implemental Mind-Set on Attitude Strength

    OpenAIRE

    Henderson, Marlone D.; Liver, Yaël de; Gollwitzer, Peter M.

    2008-01-01

    The authors investigated whether an implemental mind-set fosters stronger attitudes. Participants who made a decision about how to act (vs. those who held off) expressed a more extreme attitude toward an issue unrelated to the decision (Experiment 1). Participants who planned the implementation of a decision (vs. deliberated vs. control) exhibited less ambivalent (Experiment 2) and more accessible (Experiment 3) attitudes toward various objects unrelated to the decision. Moreover, an attitude...

  11. 基于增强学习控制器的仿生水下机器人姿态镇定研究%Reinforcement Learning Controller Based Attitude Stabilization for Bionic Underwater Robots

    Institute of Scientific and Technical Information of China (English)

    张卫武; 林龙信

    2012-01-01

    仿生水下机器人是水下机器人领域的一个重要研究方向;利用增强学习控制器对仿生水下机器人的姿态镇定问题进行了研究;增强学习控制器主要由回报函数、学习样本数据库、神经网络、动作选择以及Q学习算法等模块构成,可通过直接与环境交互生成最优动作选择策略;镇定仿生水下机器人的偏航角姿态镇定的仿真试验表明,增强学习控制器在偏航角姿态镇定方面的性能较为理想;学习样本数据库的引入显著提升了增强学习控制器的姿态镇定性能;学习样本数据库的容量对学习性能存在较大影响.%The bionic underwater robot is one of the most important fields in underwater robots. This paper discussed the attitude stabilization problem of bionic underwater robots based on the reinforcement learning controller which is composed of reward function, database of learning samples, neural network, action selection and the Q—learning algorithm. Simulation experiments about the yawing angle stabilization are carried out, and results indicate that the reinforcement learning controller has a good performance in yawing angle stabilization; the database of learning samples improves the attitude stabilization performance evidently; the capacity of the database of learning samples has a big influence on the learning performance.

  12. ABFAB. Attachment to the breast and family attitudes to breastfeeding. The effect of breastfeeding education in the middle of pregnancy on the initiation and duration of breastfeeding: a randomised controlled trial [ISRCTN21556494

    Directory of Open Access Journals (Sweden)

    Waldenström Ulla

    2003-08-01

    Full Text Available Abstract Background It has proven difficult to reach World Health Organization (WHO recommendations that infants be exclusively breastfed from birth to six months of age 12, yet there is limited knowledge about interventions that are effective in increasing breastfeeding initiation and duration. Particularly lacking is evidence about how to maintain breastfeeding rates in countries which already have a high initiation of breastfeeding. This study aims to determine whether mid-pregnancy breastfeeding education, with a focus on either attitudes to breastfeeding or on technical aspects of breastfeeding, has an effect on rates of breastfeeding initiation and duration. Secondary aims of the study are to: explore what factors might affect the duration of breastfeeding and evaluate the interventions from the participant and childbirth facilitator perspectives. Methods/Design A randomised controlled trial (RCT design will be used. Women having their first baby, and planning to give birth as public patients at the Royal Women's Hospital (RWH, Melbourne, will be approached at 18–20 weeks of pregnancy and invited to participate in the study. Participants will be randomly allocated to a control group or one of two group interventions: a previously designed and trialled tool to teach practical aspects of breastfeeding or an exploration of family attitudes to breastfeeding. The latter was developed and piloted by the investigators in conjunction with the group facilitators, prior to trial commencement. The interventions are planned to take place at 20–25 weeks. Data will be collected by questionnaire at recruitment, at interview in hospital after the birth and by telephone interview six months later. Medical/obstetric outcomes will be obtained from the medical record. The sample size (972 was calculated to identify an increase in breastfeeding initiation from 75 to 85% and an increase from 40 to 50% in breastfeeding at six months.

  13. Scaling of Attitudes Toward Population Problems

    Science.gov (United States)

    Watkins, George A.

    1975-01-01

    This study related population problem attitudes and socioeconomic variables. Six items concerned with number of children, birth control, family, science, economic depression, and overpopulation were selected for a Guttman scalogram. Education, occupation, and number of children were correlated with population problems scale scores; marital status,…

  14. Adultos livres de cárie: estudo de casos e controles sobre conhecimentos, atitudes e práticas preventivas Adults free of caries: a case-control study about: awareness/consciousness, attitudes and preventive practices

    Directory of Open Access Journals (Sweden)

    Paulo C. Petry

    2000-01-01

    Full Text Available Com o objetivo de investigar o efeito do conhecimento e atitudes pessoais, hábitos de higiene oral e uso de fluoretos sobre a total ausência de cáries, realizou-se um estudo do tipo caso-controle entre estudantes universitários da região sul do Brasil. A análise bruta por regressão logística condicional não demonstrou efeito para as variáveis relacionadas ao uso de fluoretos e hábitos de higiene oral (p > 0,20. Já o uso de fio dental apareceu como um fator de risco: os que afirmaram não usá-lo apresentaram "odds ratio" (OR bruto de 0,70, e de 0,73 quando ajustado para visitas regulares ao dentista. O efeito para as visitas regulares ao dentista foi de risco. Pessoas com história de cárie visitavam mais os profissionais. Aqueles com história de cárie apresentaram um "odds ratio" bruto de 1,55; após o ajuste para uso de fio dental o risco foi levemente superior (OR = 1,67. Hábitos de higiene oral não demonstraram efeito protetor esperado. O uso de fluoretos não esteve significativamente associado à ausência de cáries. Permanece intrigando o fato de que algumas pessoas não desenvolvam cáries, mesmo não relatando cuidados considerados ideais à saúde bucal.The purpose of this article was to investigate the effect of personal awareness and attitudes, the dentist's role, oral hygiene habits, and fluoride use on total absence of caries in adults, using a case-control study matched for sex and age with undergraduate students from two private Brazilian universities. Crude analysis using conditional logistic regression failed to show any effect for the related variables regarding fluoride use and oral hygiene habits (p > 0.20. Use of dental floss was the only exception in this set. It appeared as a risk factor, since individuals who stated not flossing presented a crude odds ratio (OR of 0.70, or 0.73 when adjusted for regular visits to the dentist. The effect for regular visits to the dentist was that of a risk. Those with a

  15. Measuring Attitudes Toward Inclusion

    Directory of Open Access Journals (Sweden)

    André Kunz

    2010-12-01

    Full Text Available The considerable worldwide demand for an inclusive education system has driven Switzerland to reconsider the approach of segregated schooling for children with Special Educational Needs (SEN. Recently, an agreement was signed among the states with the intention to adopt a more inclusive practice in school. There is evidence suggesting that an inclusive practice established at policy level is not enough, as many times it becomes teacher’s effort to translate the policies in classroom setting. The effectiveness of inclusive practices can be tightly related to the attitude of teachers, parents and students to inclusion of children with SEN in mainstreaming classes. Attitude towards inclusion is an observable construct but it presents difficulties in terms of measurement. For this purpose, in order to evaluate the attitude to inclusion of teachers, parents and students, an American Scale, the 11-items Parent Attitude to Inclusion (Palmer et al., 1998a, 1998b, 2001 and the version for teachers (Stanley, Grimbeek, Bryer, Beamisch, 2003; Bryer, Grimbeek, Beamish, Stanley, 2004, has been slightly modified and translated into German language. The resulting scales have been used to collect data in Switzerland in two regions. Results show that the German version of the scale can be potentially used for reliable measurement of attitudes toward inclusion in German speaking countries.

  16. Attitude Assessment Using Pleiades-Hr Capabilities

    Science.gov (United States)

    Delevit, J. M.; Greslou, D.; Amberg, V.; Dechoz, C.; de Lussy, F.; Lebegue, L.; Latry, C.; Artigues, S.; Bernard, L.

    2012-07-01

    Since SPOT1, the French national space centre (CNES) has worked on improving the geometry of Earth observation spacecrafts. The accuracy of sensor calibration is one of the main key points for any Earth observation application such as orthorectification, DEM generation or surface change detection. For the last twenty years CNES has developed two families of methods: absolute methods and relative methods. These methods are used to characterize a pushbroom acquisition along the detector line and the time line. By this way, the viewing directions are measured and the residual of the spacecraft's attitude angles (not restituted by the Attitude and Orbit Control System) is estimated. This information can complete the geometric model of all the scenes acquired by the instrument and is used in all geometric applications. This paper presents new attitude assessment methods taking advantage of the capabilities of Pléiades-HR in terms of agility and focal plane arrangement - panchromatic band and multispectral (MS) bands.

  17. Attributions and Attitudes of Mothers and Fathers in Italy.

    Science.gov (United States)

    Bombi, Anna Silvia; Pastorelli, Concetta; Bacchini, Dario; Di Giunta, Laura; Miranda, Maria C; Zelli, Arnaldo

    2011-07-01

    OBJECTIVE: The present study examined mean level similarities and differences as well as correlations between mothers' and fathers' attributions regarding successes and failures in caregiving situations and progressive versus authoritarian attitudes. DESIGN: Interviews were conducted with both mothers and fathers in 177 Italian families from Rome and Naples. RESULTS: Fathers' attributions reflected higher perceived control over failure than did mothers' attributions, whereas mothers reported attitudes that were more progressive than did fathers. Only the difference in progressive attitudes remained significant after controlling for parents' age, education, and possible social desirability bias. Site differences emerged for four of the seven attributions and attitudes examined; three remained significant after controlling for parents' age, education, and possible social desirability bias. Medium effect sizes were found for concordance between parents in the same family for authoritarian attitudes and modernity of attitudes after controlling for parents' age, education, and possible social desirability bias. CONCLUSIONS: This work elucidates ways that parent gender and cultural context relate to attributions regarding parents' success and failure in caregiving situations and to progressive versus authoritarian parenting attitudes. PMID:21927586

  18. Attitude coordination for spacecraft formation with multiple communication delays

    Directory of Open Access Journals (Sweden)

    Guo Yaohua

    2015-04-01

    Full Text Available Communication delays are inherently present in information exchange between spacecraft and have an effect on the control performance of spacecraft formation. In this work, attitude coordination control of spacecraft formation is addressed, which is in the presence of multiple communication delays between spacecraft. Virtual system-based approach is utilized in case that a constant reference attitude is available to only a part of the spacecraft. The feedback from the virtual systems to the spacecraft formation is introduced to maintain the formation. Using backstepping control method, input torque of each spacecraft is designed such that the attitude of each spacecraft converges asymptotically to the states of its corresponding virtual system. Furthermore, the backstepping technique and the Lyapunov–Krasovskii method contribute to the control law design when the reference attitude is time-varying and can be obtained by each spacecraft. Finally, effectiveness of the proposed methodology is illustrated by the numerical simulations of a spacecraft formation.

  19. Communication skills training in undergraduate medicine: attitudes and attitude change.

    OpenAIRE

    Doherty, Eva M; McGee, Hannah; O'Boyle, Ciaran; Shannon, William; Bury, Gerard; Williams, A.

    1992-01-01

    The importance of communication skills training in undergraduate medical education is now widely accepted. However little is known about student attitudes towards their own communication skills and whether their attitudes changes as a result of participating in communication skills courses. The aim of the present study was to identify these attitudes prior to commencing such a course and to further evaluate changes in these attitudes on completion of the course. Results demonstrated an improv...

  20. International Space Station Attitude Motion Associated With Flywheel Energy Storage

    Science.gov (United States)

    Roithmayr, Carlos M.

    1999-01-01

    Flywheels can exert torque that alters the Station's attitude motion, either intentionally or unintentionally. A design is presented for a once planned experiment to contribute torque for Station attitude control, while storing or discharging energy. Two contingencies are studied: the abrupt stop of one rotor while another rotor continues to spin at high speed, and energy storage performed with one rotor instead of a counter rotating pair. Finally, the possible advantages to attitude control offered by a system of ninety-six flywheels are discussed.

  1. Combinators for Paraconsistent Attitudes

    DEFF Research Database (Denmark)

    Villadsen, Jørgen

    2001-01-01

    In order to analyse the semantics of natural language sentences a translation into a partial type logic using lexical and logical combinators is presented. The sentences cover a fragment of English with propositional attitudes like knowledge, belief and assertion. A combinator is a closed term of...... only used for embedded sentences expressing propositional attitudes, thereby allowing for inconsistency without explosion (also called paraconsistency), and is based on a few key equalities for the connectives giving four truth values (truth, falsehood, and undefinedness with negative and positive...

  2. Attitude that Matters

    OpenAIRE

    Tiina Purhonen

    2007-01-01

    In this article, I compare the operativity of radical avant-garde and new dialogical art forms from one selected viewpoint. I discuss the issue of the artist's attitude as a significance-producing element in the artwork. For decades, artist-issued interpretation of art has been problematic. Thus it is interesting to question the significance of the strong definition of the artist's attitude, inherent in the theories of the new dialogical art. New dialogical art-forms are for example new genre...

  3. Attitude scale and general health questionnaire subscales predict depression?

    OpenAIRE

    Amrollah Ebrahimi; Hamid Afshar; Hamid Taher Neshat Doost; Seyed Ghafur Mousavi; Hoseyn Moolavi

    2012-01-01

    Background: According to Beck theory, dysfunctional attitude has a central role in emergence of depression. The aim of this study was to determine contributions of dysfunctional attitude and general health index to depression. Methods: In this case-control study, two groups of subjects participated. The first group consisted of 65 patients with major depression and dysthymic disorder, who were recruited from Noor and Navab Safavi Psychiatry Clinics in Isfa-han. The control group was consi...

  4. Wages, Amenities and Negative Attitudes

    OpenAIRE

    Waisman, Gisela; Larsen, Birthe

    2012-01-01

    We exploit the regional variation in negative attitudes towards immigrants to Sweden in order to analyse the consequences of the attitudes on immigrants welfare. We find that attitudes towards immigrants are of importance: they both affect their labour market outcomes and their quality of life. We interpret the negative effect on wages as evidence of labour market discrimination. We estimate the welfare effects of negative attitudes, through their wage and local amenities, for immigrants with...

  5. Attitudes toward gambling among adolescents

    OpenAIRE

    Hanss, Daniel; Mentzoni, Rune Aune; Delfabbro, Paul; Myrseth, Helga; Pallesen, Ståle

    2014-01-01

    It is well documented that attitudes toward gambling are a good predictor of problem gambling during adolescence. However, so far, little is known about what factors are associated with adolescents' gambling attitudes. This study used cross-sectional data (N = 2055, response rate 70.4%) from a representative sample of 17-year-olds in Norway to investigate the relationship between demographic, personality, motivational and social variables and gambling attitudes. Overall, adolescents' attitude...

  6. Star trackers for attitude determination

    OpenAIRE

    Liebe, Carl Christian

    1995-01-01

    One problem comes to all spacecrafts using vector information. That is the problem of determining the attitude. This paper describes how the area of attitude determination instruments has evolved from simple pointing devices into the latest technology, which determines the attitude by utilizing a CCD camera and a powerful microcomputer. The instruments are called star trackers and they are capable of determining the attitude with an accuracy better than 1 arcsecond. The concept of the star tr...

  7. Autonomous attitude estimation via star sensing and pattern recognition

    Science.gov (United States)

    Junkins, J. L.; Strikwerda, T. E.

    1979-01-01

    Results are reported on the development of an autonomous, onboard, near real time spacecraft attitude estimation technique. The approach uses CCD based star sensors to digitize relative star positions. Three microcomputers are envisioned, configured in parallel, to: (1) determine star image centroids and delete spurious images; (2) identify measured stars with stars in an onboard catalog and determine discrete attitude estimates; (3) integrate gyro rate measurements and determine optimal real time attitude estimates for use in the control system and for feedback to the star identification algorithm. Algorithms for the star identification are presented. The discrete attitude estimation algorithm recovers thermally varying interlock angles between two star sensors. The optimal state estimation process recovers rate gyro biases in addition to real time attitude estimates.

  8. A star pattern recognition algorithm for autonomous attitude determination

    Science.gov (United States)

    Van Bezooijen, R. W. H.

    1990-01-01

    The star-pattern recognition algorithm presented allows the advanced Full-sky Autonomous Star Tracker (FAST) device, such as the projected ASTROS II system of the Mariner Mark II planetary spacecraft, to reliably ascertain attitude about all three axes. An ASTROS II-based FAST, possessing an 11.5 x 11.5 deg field of view and 8-arcsec accuracy, can when integrated with an all-sky data base of 4100 guide stars determine its attitude in about 1 sec, with a success rate close to 100 percent. The present recognition algorithm can also be used for automating the acquisition of celestial targets by astronomy telescopes, autonomously updating the attitude of gyro-based attitude control systems, and automating ground-based attitude reconstruction.

  9. Income, Amenities and Negative Attitudes

    DEFF Research Database (Denmark)

    Waisman, Gisela; Larsen, Birthe

    2016-01-01

    We exploit the regional variation in negative attitudes towards immigrants to Sweden in order to analyse the consequences of negative attitudes on refugees’ utility from labour income and amenities. We find that attitudes towards immigrants are important: while they affect mainly the refugees...

  10. Attitudes of Success.

    Science.gov (United States)

    Pendarvis, Faye

    This document investigates the attitudes of successful individuals, citing the achievement of established goals as the criteria for success. After offering various definitions of success, the paper focuses on the importance of self-esteem to success and considers ways by which the self-esteem of students can be improved. Theories of human behavior…

  11. Attitudes to nuclear waste

    International Nuclear Information System (INIS)

    This is a study of risk perception and attitudes with regard to nuclear waste. Two data sets are reported. In the first set, data were obtained from a survey of the general population, using an extensive questionnaire. The second set constituted a follow-up 7 years later, with a limited number of questions. The data showed that people considered the topic of nuclear waste risks to be very important and that they were not convinced that the technological problems had been solved. Experts associated with government agencies were moderately trusted, while those employed by the nuclear industry were much distrusted by some respondents, and very much trusted by others. Moral obligations to future generations were stressed. A large portion (more than 50 per cent) of the variances in risk perception could be explained by attitude to nuclear power, general risk sensitivity and trust in expertise. Most background variables, except gender, had little influence on risk perception and attitudes. The follow-up study showed that the attitude to nuclear power had become more positive over time, but that people still doubted that the problems of nuclear waste disposal had been solved. 49 refs

  12. Attitudes toward Rape.

    Science.gov (United States)

    Larsen, Knud S.; Long, Ed

    While the perception of rape has been studied intensely in recent years, most scales focus on rape myths as the content domain. The need exists for a more general instrument which would include items from a variety of sources, e.g., attitudes toward rape awareness, sexual history, age, virginity, community support, etc., in addition to the myth of…

  13. Assessing transcultural attitudes towards diabetes in Trinidad.

    Science.gov (United States)

    Johnson, Cynthia; Whetstone, William R

    2005-12-01

    The purpose of this descriptive correlational study was to assess diabetic attitudes among adults living and working on the Caribbean Island of Trinidad. A convenience sample of 66 (N = 66) adult men and women of Afro-Trinidadian descent, of Indo-Trinidadian descent, and of mixed ethnicity completed the 33-item Diabetic Attitude Scale (DAS-3) with its five sub-scales. They were: (1) Need for special training in education, (2) Seriousness of Type 2 diabetes, (3) Value of tight glucose control, (4) Psychosocial impact of diabetes, and (5) Autonomy and patient attitudes. Self-Determination Theory guided the conceptual development of the study. Data analyses revealed a strong effect between need for special training and autonomy and patient attitudes. Strong correlations were also found between seriousness of the disease, value of tight glucose control, and psychosocial impact. Moderate correlations were found between the other variables of the sub-scales. Practical implications were discussed. Findings suggest the need for more appropriate educational and supportive interventions of an autonomous nature. PMID:16570642

  14. Self-reported practices and attitudes of community health workers (accredited social health activist in tobacco control - Findings from two states in India

    Directory of Open Access Journals (Sweden)

    Divya Persai

    2015-01-01

    Conclusions: Study findings reflect suboptimal engagement of ASHAs in providing information pertaining to specific tobacco-related diseases. There is an urgent need to sensitize and train ASHAs in appropriate tobacco control practices.

  15. Attitude Representations for Kalman Filtering

    Science.gov (United States)

    Markley, F. Landis; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    The four-component quaternion has the lowest dimensionality possible for a globally nonsingular attitude representation, it represents the attitude matrix as a homogeneous quadratic function, and its dynamic propagation equation is bilinear in the quaternion and the angular velocity. The quaternion is required to obey a unit norm constraint, though, so Kalman filters often employ a quaternion for the global attitude estimate and a three-component representation for small errors about the estimate. We consider these mixed attitude representations for both a first-order Extended Kalman filter and a second-order filter, as well for quaternion-norm-preserving attitude propagation.

  16. MODEL OF CENTRIFUGAL EFFECT AND ATTITUDE MANEUVER STABILITY OF A COUPLED RIGID-FLEXIBLE SYSTEM

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-bin; WANG Zhao-lin; WANG Tian-shu; LIU Ning

    2005-01-01

    The influences of nonlinear centrifugal force to large overall attitude motion of coupled rigid-flexible system was investigated. First the nonlinear model of the coupled rigidflexible system was deduced from the idea of "cenlrifugal potential field", and then the dynamic effects of the nonlinear centrifugal force to system attitude motion were analyzed by approximate calculation; At last, the Lyapunov function based on energy norm was selected,in the condition that only the measured values of attitude and attitude speed are available,and it is proved that the PD feedback control law can ensure the attitude stability during large angle maneuver.

  17. Attitude synchronization for multiple spacecraft with input constraints

    Directory of Open Access Journals (Sweden)

    Lyu Jianting

    2014-04-01

    Full Text Available The attitude synchronization problem for multiple spacecraft with input constraints is investigated in this paper. Two distributed control laws are presented and analyzed. First, by introducing bounded function, a distributed asymptotically stable control law is proposed. Such a control scheme can guarantee attitude synchronization and the control inputs of each spacecraft can be a priori bounded regardless of the number of its neighbors. Then, based on graph theory, homogeneous method, and Lyapunov stability theory, a distributed finite-time control law is designed. Rigorous proof shows that attitude synchronization of multiple spacecraft can be achieved in finite time, and the control scheme satisfies input saturation requirement. Finally, numerical simulations are presented to demonstrate the effectiveness and feasibility of the proposed schemes.

  18. IDENTIFICATION OF GYRO DRIFTS UNDER THREE AXIS ATTITUDE COUPLING

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    Optical gyros and star sensors are primary measurement hardware in an attitude control system with high accuracy.The drifts of the optical gyros, however, make an unfavorable impact on the accuracy of the attitude control system.In order for compensations to be provided, this paper presents a least-square method to identify the optical gyro drifts by using flight attitude data from the star sensors and the optical gyros.Equations for identification are formulated by quaternion.Integration of the identification equations and the data from the star sensors are utilized to form a least-square index, in which lower sampling frequency of the star sensors than that of the optical gyros is dealt with effectively.An iterative identification algorithm is presented to minimize the index.Identification procedure under three-axis attitude coupling is illustrated .Simulation results show the effectiveness of the method presented.Proper sample size and sampling frequency are also recommended.

  19. Attitudes towards Immigration

    DEFF Research Database (Denmark)

    Dinesen, Peter Thisted; Klemmensen, Robert; Nørgaard, Asbjørn Sonne

    2016-01-01

    immigration: scoring higher on this trait implies a greater willingness to admit immigrants. Moreover, individuals react differently to economic threat depending on their score on the traits Agreeableness and Conscientiousness. Specifically, individuals scoring low on Agreeableness and individuals scoring...... high on Conscientiousness are more sensitive to the skill level of immigrants. The results imply that personality is important for attitudes toward immigration, and in the conclusion, we further discuss how the observed conditional and unconditional effects of personality make sense theoretically....

  20. Iranian Common Attitude Toward Opium Consumption.

    Science.gov (United States)

    Zarghami, Mehran

    2015-06-01

    Iran is suffering from the 2(nd) most severe addiction to opioids in the world. While the explanation of this enormous drug problem is refutably related to drug trafficking, the drug dilemma also illustrates the chain reaction of the imposed war with Iraq in 1980 - 88; the problems of poverty, unemployment, urbanization, homelessness, adultery, family crises, divorce, domestic violence, and runaway children. Although opium addiction often linked to these factors, drug use is common among all social classes. It seems that a positive traditional attitude is another reason for widespread raw opium use in this country. A survey in Iranian literature reveals that famous Iranian poets, who have a substantial contribution on cultural attitude formation of Iranian population, have used the phrase "Teriac" (raw opium) as a means of "antidote" a substance that treats every disease. It seems that a concrete deduction from the literature has been leaden to a positive attitude towards opium consumption in Persian culture. Recent research also supports this idea. Many patients use raw opium as a pain killer or for treating hyperlipidemia, hypertension, diabetes and other chronic diseases; most of them had started the use after developing the disease and the remaining had increased the consumption after developing the disease. Regarding this superstitious common belief, drug control headquarters should focus on education and correction of the faulty unhealthy attitude toward opium consumption. PMID:26288642