Reconfiguring and Realigning the Assessment Feedback Processes for an Undergraduate Criminology Degree

Science.gov (United States)

Case, Stephen

2007-01-01

A reconfigured and realigned system of assessment feedback was implemented with undergraduates taking criminology modules at Swansea University. The reformulated system integrated explicit engagement with assessment criteria in feedback given on an electronic template form with the use of a statement bank and the offer of follow-up, feedback…

Multi-bunch Feedback Systems

OpenAIRE

Lonza, M.; Schmickler, H.

2016-01-01

Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides importa...

A physical control interface with proprioceptive feedback and multiple degrees of freedom

Science.gov (United States)

Creasey, G. H.; Gow, D.; Sloan, Y.; Meadows, B.

1991-01-01

The use of the drug thalidomide by pregnant mothers in Britain resulted in a variety of deformities including the birth of children having no arms. Such children were provided with powered artificial arms with up to five degrees of freedom simultaneously controlled in real time by shoulder movement. The physiological sense of proprioception was extended from the user into the device, reducing the need for visual feedback and conscious control. With the banning of thalidomide, this technique fell into disuse but it is now being re-examined as a control mechanism for other artificial limbs and it may have other medical applications to allow patients to control formerly paralyzed limbs moved by electrical stimulation. It may also have commercial applications in robotic manipulation or physical interaction with virtual environments. To allow it to be investigated further, the original pneumatic control system has recently been converted to an electrical analogue to allow interfacing to electronic and computer-assisted systems. A harness incorporates force-sensitive resistors and linear potentiomenters for sensing position and force at the interface with the skin, and miniature electric motors and lead screws for feeding back to the user the position of the robotic arm and the forces applied to it. In the present system, control is applied to four degrees of freedom using elevation/depression and protraction/reaction of each shoulder so that each collar bone emulates a joystick. However, both electrical and mechanical components have been built in modular form to allow rapid replication and testing of a variety of force and position control strategies.

External Periodic Force Control of a Single-Degree-of-Freedom Vibroimpact System

Directory of Open Access Journals (Sweden)

Jingyue Wang

2013-01-01

Full Text Available A single-degree-of-freedom mechanical model of vibro-impact system is established. Bifurcation and chaos in the system are revealed with the time history diagram, phase trajectory map, and Poincaré map. According to the bifurcation and chaos of the actual vibro-impact system, the paper puts forward external periodic force control strategy. The method of controlling chaos by external periodic force feedback controller is developed to guide chaotic motions towards regular motions. The stability of the control system is also analyzed especially by theory. By selecting appropriate feedback coefficients, the unstable periodic orbits of the original chaotic orbit can be stabilized to the stable periodic orbits. The effectiveness of this control method is verified by numerical simulation.

Feedback systems for linear colliders

CERN Document Server

Hendrickson, L; Himel, Thomas M; Minty, Michiko G; Phinney, N; Raimondi, Pantaleo; Raubenheimer, T O; Shoaee, H; Tenenbaum, P G

1999-01-01

Feedback systems are essential for stable operation of a linear collider, providing a cost-effective method for relaxing tight tolerances. In the Stanford Linear Collider (SLC), feedback controls beam parameters such as trajectory, energy, and intensity throughout the accelerator. A novel dithering optimization system which adjusts final focus parameters to maximize luminosity contributed to achieving record performance in the 1997-98 run. Performance limitations of the steering feedback have been investigated, and improvements have been made. For the Next Linear Collider (NLC), extensive feedback systems are planned as an intregal part of the design. Feedback requiremetns for JLC (the Japanese Linear Collider) are essentially identical to NLC; some of the TESLA requirements are similar but there are significant differences. For NLC, algorithms which incorporate improvements upon the SLC implementation are being prototyped. Specialized systems for the damping rings, rf and interaction point will operate at hi...

A Complete Parametric Solutions of Eigenstructure Assignment by State-Derivative Feedback for Linear Control Systems

Directory of Open Access Journals (Sweden)

T. H. S. Abdelaziz

2005-01-01

Full Text Available In this paper we introduce a complete parametric approach for solving the problem of eigenstructure assignment via state-derivative feedback for linear systems. This problem is always solvable for any controllable systems iff the open-loop system matrix is nonsingular. In this work, two parametric solutions to the feedback gain matrix are introduced that describe the available degrees of freedom offered by the state-derivative feedback in selecting the associated eigenvectors from an admissible class. These freedoms can be utilized to improve robustness of the closed-loop system. Accordingly, the sensitivity of the assigned eigenvalues to perturbations in the system and gain matrix is minimized. Numerical examples are included to show the effectiveness of the proposed approach. 

The usefulness of 360 degree feedback in developing a personal work style

OpenAIRE

Chicu Nicoleta; Nedelcu Alexandra Catalina

2017-01-01

The present study focuses on a new approach in the process of developing personal work styles, based on the usefulness of 360 degree feedback, taking into consideration the following dimensions: work-life balance, gender-age, self-development and the behavior a person has, following the process of self-development and defining work style. Using different approaches, the study attempts to identify if there are some differences between the evaluations received from the family and the ones from ...

Operation of PEP longitudinal feedback system

International Nuclear Information System (INIS)

Allen, M.A.; Karvonen, L.G.; McConnell, R.A.; Schwarz, H.

1981-03-01

In order to suppress longitudinal coupled-bunch oscillations which might limit the capabilities of PEP, the 18 GeV e + e - storage ring at SLAC, a longitudinal feedback system is utilized. A frequency domain feedback system was chosen with the frequency spectrum of the stored beam being sampled close to a symmetry point in the ring where the feedback cavity itself is also located. The symmetry point chosen is symmetry point 5 which lies half-way between interaction regions 4 and 6. The system has been installed in PEP and is now operational. However, at stored currents up to the maximum stored in PEP to date at 14.5 GeV (approximately 40 mA in 6 bunches), the ring has been stable to all modes of longitudinal coupled-bunch oscillations both barycentric and the other fundamental modes. By deliberately detuning the main accelerating cavities, small multibunch oscillations can be introduced which, in turn, can be damped by the feedback system. Under optimized beam conditions the feedback system could be adjusted to positive feedback and excite oscillations with relatively small power to the feedback cavity. This will be described along with other details of the system

Theory of multi-bunch feedback systems

International Nuclear Information System (INIS)

Kohaupt, R.D.

1991-06-01

In this article the theory of multibunch feedback systems is developed in a rigorous way including the fact that the elements of feedback systems are localized in the ring. The results of the theory which can be used for any strength of the systems are the base for the multibunch feedback systems for PETRA and HERA, already tested successfully in PETRA. (orig.)

Feedbacks in human-landscape systems

Science.gov (United States)

Chin, Anne

2015-04-01

As human interactions with Earth systems intensify in the "Anthropocene", understanding the complex relationships among human activity, landscape change, and societal responses to those changes is increasingly important. Interdisciplinary research centered on the theme of "feedbacks" in human-landscape systems serves as a promising focus for unraveling these interactions. Deciphering interacting human-landscape feedbacks extends our traditional approach of considering humans as unidirectional drivers of change. Enormous challenges exist, however, in quantifying impact-feedback loops in landscapes with significant human alterations. This paper illustrates an example of human-landscape interactions following a wildfire in Colorado (USA) that elicited feedback responses. After the 2012 Waldo Canyon Fire, concerns for heightened flood potential and debris flows associated with post-fire hydrologic changes prompted local landowners to construct tall fences at the base of a burned watershed. These actions changed the sediment transport regime and promoted further landscape change and human responses in a positive feedback cycle. The interactions ultimately increase flood and sediment hazards, rather than dampening the effects of fire. A simple agent-based model, capable of integrating social and hydro-geomorphological data, demonstrates how such interacting impacts and feedbacks could be simulated. Challenges for fully capturing human-landscape feedback interactions include the identification of diffuse and subtle feedbacks at a range of scales, the availability of data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, and the varied metrics and data needed to represent both the physical and human systems. By collaborating with social scientists with expertise in the human causes of landscape change, as well as the human responses to those changes, geoscientists could more fully recognize and anticipate the coupled

360-Degree Feedback Implementation Plan: Dean Position, Graduate School of Business and Public Policy, Naval Postgraduate School

National Research Council Canada - National Science Library

Morrison, Devin

2002-01-01

360-degree feedback is a personal development and appraisal tool designed to quantify the competencies and skills of fellow employees by tapping the collective experience of their superiors, subordinates, and peers...

Ambulatory Feedback System

Science.gov (United States)

Finger, Herbert; Weeks, Bill

1985-01-01

This presentation discusses instrumentation that will be used for a specific event, which we hope will carry on to future events within the Space Shuttle program. The experiment is the Autogenic Feedback Training Experiment (AFTE) scheduled for Spacelab 3, currently scheduled to be launched in November, 1984. The objectives of the AFTE are to determine the effectiveness of autogenic feedback in preventing or reducing space adaptation syndrome (SAS), to monitor and record in-flight data from the crew, to determine if prediction criteria for SAS can be established, and, finally, to develop an ambulatory instrument package to mount the crew throughout the mission. The purpose of the Ambulatory Feedback System (AFS) is to record the responses of the subject during a provocative event in space and provide a real-time feedback display to reinforce the training.

Bunch by bunch feedback systems

International Nuclear Information System (INIS)

Tobiyama, Makoto

2006-01-01

Outlines of bunch-by-bunch feedback systems for suppressing multibunch instabilities in electron/positron storage rings are presented. The design principles and functions of the feedback components are reviewed. Recent topics of applying very fast and dense FPGA as feedback signal processor are also shown. (author)

Output Feedback Adaptive Control of Non-Minimum Phase Systems Using Optimal Control Modification

Science.gov (United States)

Nguyen, Nhan; Hashemi, Kelley E.; Yucelen, Tansel; Arabi, Ehsan

2018-01-01

This paper describes output feedback adaptive control approaches for non-minimum phase SISO systems with relative degree 1 and non-strictly positive real (SPR) MIMO systems with uniform relative degree 1 using the optimal control modification method. It is well-known that the standard model-reference adaptive control (MRAC) cannot be used to control non-SPR plants to track an ideal SPR reference model. Due to the ideal property of asymptotic tracking, MRAC attempts an unstable pole-zero cancellation which results in unbounded signals for non-minimum phase SISO systems. The optimal control modification can be used to prevent the unstable pole-zero cancellation which results in a stable adaptation of non-minimum phase SISO systems. However, the tracking performance using this approach could suffer if the unstable zero is located far away from the imaginary axis. The tracking performance can be recovered by using an observer-based output feedback adaptive control approach which uses a Luenberger observer design to estimate the state information of the plant. Instead of explicitly specifying an ideal SPR reference model, the reference model is established from the linear quadratic optimal control to account for the non-minimum phase behavior of the plant. With this non-minimum phase reference model, the observer-based output feedback adaptive control can maintain stability as well as tracking performance. However, in the presence of the mismatch between the SPR reference model and the non-minimum phase plant, the standard MRAC results in unbounded signals, whereas a stable adaptation can be achieved with the optimal control modification. An application of output feedback adaptive control for a flexible wing aircraft illustrates the approaches.

Evaluation of strip-line pick-up system for the SPS wideband transverse feedback system

CERN Document Server

Kotzian, G; Steinhagen, R J; Valuch, D; Wehrle, U

2017-01-01

The proposed SPS Wideband Transverse Feedback sys- tem requires a wide-band pick-up system to be able to de- tect intra-bunch motion within the SPS proton bunches, captured and accelerated in a 200 MHz bucket. We present the electro-magnetic design of transverse beam position pick-up options optimised for installation in the SPS and evaluate their performance reach with respect to direct time domain sampling of the intra-bunch motion. The analy- sis also discusses the achieved subsystem responses of the associated cabling with new low dispersion smooth wall coaxial cables, wide-band generation of intensity and posi- tion signals by means of 180 degree RF hybrids as well as passive techniques to electronically suppress the beam off- set signal, needed to optimise the dynamic range and posi- tion resolution of the planned digital intra-bunch feedback system.

Adaptive feedback synchronization of Lue system

International Nuclear Information System (INIS)

Han, X.; Lu, J.-A.; Wu, X.

2004-01-01

This letter further improves and extends the works of Chen and Lue [Chaos, Solitons and Fractals 14 (2002) 643] and Wang et al. [Phys. Lett. A 312 (2003) 34]. In detail, the linear feedback synchronization and adaptive feedback synchronization for Lue system are discussed. And the lower bound of the feedback gain in linear feedback synchronization is presented. The adaptive feedback synchronization with only one controller is designed, which improves the proof in the work by Wang et al. The adaptive synchronization with two controllers for completely uncertain Lue system is also discussed, which extends the work of Chen and Lue. Also, numerical simulations show the effectiveness of these methods

Research of a New 6-Dof Force Feedback Hand Controller System

Directory of Open Access Journals (Sweden)

Xin Gao

2014-01-01

Full Text Available The field of teleoperation with force telepresence has expanded its scope to include manipulation at different scales and in virtual worlds, and the key component of which is force feedback hand controller. This paper presents a novel force feedback hand controller system, including a 3-dof translational and 3-dof rotational hand controllers, respectively, to implement position and posture teleoperation of the robot end effector. The 3-dof translational hand controller adopts innovative three-axes decoupling structure based on the linear motor; the 3-dof rotational hand controller adopts serial mechanism based on three-axes intersecting at one point, improving its overall stiffness. Based on the kinematics, statics, and dynamics analyses for two platforms separately, the system applies big closed-loop force control method based on the zero force/torque, improving the feedback force/torque accuracy effectively. Experimental results show that self-developed 6-dof force feedback hand controller has good mechanical properties. The translational hand controller has the following advantages: simple kinematics solver, fast dynamic response, and better than 0.05 mm accuracy of three-axis end positioning, while the advantages of the rotational hand controller are wide turning space, larger than 1 Nm feedback, greater than 180 degrees of operating space of three axes, respectively, and high operation precision.

Recognition of boundary feedback systems

DEFF Research Database (Denmark)

Pedersen, Michael

1989-01-01

A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback stabili...... stabilizability. It is shown that it is possible to use the calculus to consider more general feedback systems in a variational setup.......A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback...

Numerical study on identification of transfer functions in a feedback system and model reduction

International Nuclear Information System (INIS)

Kishida, Kuniharu

1997-01-01

Identification of transfer function matrices in a feedback system is discussed by using the singular value decomposition of Hankel matrix from the viewpoint of inverse problems. A method of model reduction is considered, and selection criteria are proposed for identification of them. Transformation formula between open loop and closed loop transfer function matrices are determined from the feedback loop structure, and they are needed for identification of open loop transfer function matrices under such a condition where the feedback system is in a minimum phase. Though the identifiability of open loop transfer function matrices can be examined in the framework of innovation model equivalent to the feedback system, there are pole-zero cancellations in the identification of them. The method to reduce a model order of an open loop transfer function is discussed by using the singular value decomposition of a gramian given by the open loop transfer function with higher degree. To check reliability of the present algorithm, a simulation study is performed for an example. (author)

An FPGA-based Bunch-by-Bunch Position and Angle Feedback System at ATF2

CERN Document Server

Christian, G B; Bett, D R; Burrows, P N; Constance, B; Davis, M R; Gerbershagen, A; Perry, C; Resta Lopez, J

2011-01-01

The FONT5 intra-train feedback system serves as a prototype for an interaction point beam-based feedback system for future electron-positron colliders, such as the International Linear Collider. The system has been tested on the KEK Accelerator Test Facility (ATF) and is deployed to stabilise the beam orbit at the ATF2. The goal of this system is to correct both position and angle jitter in the vertical plane, providing stability of ~1 micron at the entrance to the ATF2 final-focus system. The system comprises three stripline beam position monitors (BPMs) and two stripline kickers, custom low-latency analogue front-end BPM processors, a custom FPGA-based digital processing board with fast ADCs, and custom kicker-drive amplifiers. An overview of the hardware, and the latest results from beam tests at ATF2, will be presented. The total latency of the system with coupled position and angle feedback loops operating simultaneously was measured to be approximately 140 ns. The greatest degree of correction observed ...

Feedback-linearization and feedback-feedforward decentralized control for multimachine power system

Energy Technology Data Exchange (ETDEWEB)

De Tuglie, Enrico [Dipartimento di Ingegneria dell' Ambiente, e per lo Sviluppo Sostenibile - DIASS, Politecnico di Bari, Viale del Turismo 8, 74100 Taranto (Italy); Iannone, Silvio Marcello; Torelli, Francesco [Dipartimento di Elettrotecnica, ed Elettronica - DEE, Politecnico di Bari, Via Re David 200, 70125 Bari (Italy)

2008-03-15

In this paper a decentralized nonlinear controller for large-scale power systems is investigated. The proposed controller design is based on the input-output feedback linearization methodology. In order to overcome computational difficulties in adopting such methodology, the overall interconnected nonlinear system, given as n-order, is analyzed as a cascade connection of an n{sub 1}-order nonlinear subsystem and an n{sub 2}-order linear subsystem. The controller design is obtained by applying input-output feedback linearization to the nonlinear subsystem and adopting a tracking control scheme, based on feedback-feedforward technique, for the linear subsystem. In the assumed system model, which is characterised by an interconnected structure between generating units, a decentralised adaptive controller is implemented by decentralizing these constraints. The use of a totally decentralised controller implies a system performance decay with respect to performance when the system is equipped with a centralised controller. Fortunately, the robustness of the proposed controller, based on input-output feedback procedure, guarantees good performance in terms of disturbance even when disturbances are caused by decentralization of interconnection constraints. Test results, provided on the IEEE 30 bus test system, demonstrate the effectiveness and practical applicability of proposed methodology. (author)

Feedback-Equivalence of Nonlinear Systems with Applications to Power System Equations.

Science.gov (United States)

Marino, Riccardo

The key concept of the dissertation is feedback equivalence among systems affine in control. Feedback equivalence to linear systems in Brunovsky canonical form and the construction of the corresponding feedback transformation are used to: (i) design a nonlinear regulator for a detailed nonlinear model of a synchronous generator connected to an infinite bus; (ii) establish which power system network structures enjoy the feedback linearizability property and design a stabilizing control law for these networks with a constraint on the control space which comes from the use of d.c. lines. It is also shown that the feedback linearizability property allows the use of state feedback to contruct a linear controllable system with a positive definite linear Hamiltonian structure for the uncontrolled part if the state space is even; a stabilizing control law is derived for such systems. Feedback linearizability property is characterized by the involutivity of certain nested distributions for strongly accessible analytic systems; if the system is defined on a manifold M diffeomorphic to the Euclidean space, it is established that the set where the property holds is a submanifold open and dense in M. If an analytic output map is defined, a set of nested involutive distributions can be always defined and that allows the introduction of an observability property which is the dual concept, in some sense, to feedback linearizability: the goal is to investigate when a nonlinear system affine in control with an analytic output map is feedback equivalent to a linear controllable and observable system. Finally a nested involutive structure of distributions is shown to guarantee the existence of a state feedback that takes a nonlinear system affine in control to a single input one, both feedback equivalent to linear controllable systems, preserving one controlled vector field.

Feedback coupling in dynamical systems

Science.gov (United States)

Trimper, Steffen; Zabrocki, Knud

2003-05-01

Different evolution models are considered with feedback-couplings. In particular, we study the Lotka-Volterra system under the influence of a cumulative term, the Ginzburg-Landau model with a convolution memory term and chemical rate equations with time delay. The memory leads to a modified dynamical behavior. In case of a positive coupling the generalized Lotka-Volterra system exhibits a maximum gain achieved after a finite time, but the population will die out in the long time limit. In the opposite case, the time evolution is terminated in a crash. Due to the nonlinear feedback coupling the two branches of a bistable model are controlled by the the strength and the sign of the memory. For a negative coupling the system is able to switch over between both branches of the stationary solution. The dynamics of the system is further controlled by the initial condition. The diffusion-limited reaction is likewise studied in case the reacting entities are not available simultaneously. Whereas for an external feedback the dynamics is altered, but the stationary solution remain unchanged, a self-organized internal feedback leads to a time persistent solution.

Development of a longitudinal feedback cavity for the beam feedback system

International Nuclear Information System (INIS)

Huang Gang; Chen Huaibi; Huang Wenhui; Tong Dechun; Lin Yuzheng; Zhao Zhentang

2003-01-01

Longitudinal beam feedback system is widely used to damp coupling bunch instability. Kicker is one of the key components of the longitudinal feedback system. A prototype cavity of longitudinal feedback kicker is developed according to the parameter of BEPC II. The usage of nose cone in the kicker design increased the shunt impedance. In order to avoid the extra tapper in the storage ring, the racetrack shape beam pipe is applied in the kicker. The impedance and the bandwidth of the kicker is measured by the coaxial line impedance measurement platform and the result achieved the design goals

Feedback control strategies for the Liu chaotic system

International Nuclear Information System (INIS)

Zhu Congxu; Chen Zhigang

2008-01-01

This Letter proposed three strategies of the dislocated feedback control, enhancing feedback control and speed feedback control of the Liu chaotic system to its unstable equilibrium points. It is found that the coefficients of enhancing feedback control and speed feedback control are smaller than those of ordinary feedback control, so, the complexity and cost of the system control are reduced. Theoretical analysis and numerical simulation are given, revealing the effectiveness of these strategies

The usefulness of 360 degree feedback in developing a personal work style

Directory of Open Access Journals (Sweden)

Chicu Nicoleta

2017-07-01

Full Text Available The present study focuses on a new approach in the process of developing personal work styles, based on the usefulness of 360 degree feedback, taking into consideration the following dimensions: work-life balance, gender-age, self-development and the behavior a person has, following the process of self-development and defining work style. Using different approaches, the study attempts to identify if there are some differences between the evaluations received from the family and the ones from the work environment. All these factors aim at improving personal, but also organizational performances. Based on the current body of the literature, a discussion is made and conclusions are presented.

Augmented Feedback System to Support Physical Therapy of Non-specific Low Back Pain

Science.gov (United States)

Brodbeck, Dominique; Degen, Markus; Stanimirov, Michael; Kool, Jan; Scheermesser, Mandy; Oesch, Peter; Neuhaus, Cornelia

Low back pain is an important problem in industrialized countries. Two key factors limit the effectiveness of physiotherapy: low compliance of patients with repetitive movement exercises, and inadequate awareness of patients of their own posture. The Backtrainer system addresses these problems by real-time monitoring of the spine position, by providing a framework for most common physiotherapy exercises for the low back, and by providing feedback to patients in a motivating way. A minimal sensor configuration was identified as two inertial sensors that measure the orientation of the lower back at two points with three degrees of freedom. The software was designed as a flexible platform to experiment with different hardware, and with various feedback modalities. Basic exercises for two types of movements are provided: mobilizing and stabilizing. We developed visual feedback - abstract as well as in the form of a virtual reality game - and complemented the on-screen graphics with an ambient feedback device. The system was evaluated during five weeks in a rehabilitation clinic with 26 patients and 15 physiotherapists. Subjective satisfaction of subjects was good, and we interpret the results as encouraging indication for the adoption of such a therapy support system by both patients and therapists.

A robust rotorcraft flight control system design methodology utilizing quantitative feedback theory

Science.gov (United States)

Gorder, Peter James

1993-01-01

Rotorcraft flight control systems present design challenges which often exceed those associated with fixed-wing aircraft. First, large variations in the response characteristics of the rotorcraft result from the wide range of airspeeds of typical operation (hover to over 100 kts). Second, the assumption of vehicle rigidity often employed in the design of fixed-wing flight control systems is rarely justified in rotorcraft where rotor degrees of freedom can have a significant impact on the system performance and stability. This research was intended to develop a methodology for the design of robust rotorcraft flight control systems. Quantitative Feedback Theory (QFT) was chosen as the basis for the investigation. Quantitative Feedback Theory is a technique which accounts for variability in the dynamic response of the controlled element in the design robust control systems. It was developed to address a Multiple-Input Single-Output (MISO) design problem, and utilizes two degrees of freedom to satisfy the design criteria. Two techniques were examined for extending the QFT MISO technique to the design of a Multiple-Input-Multiple-Output (MIMO) flight control system (FCS) for a UH-60 Black Hawk Helicopter. In the first, a set of MISO systems, mathematically equivalent to the MIMO system, was determined. QFT was applied to each member of the set simultaneously. In the second, the same set of equivalent MISO systems were analyzed sequentially, with closed loop response information from each loop utilized in subsequent MISO designs. The results of each technique were compared, and the advantages of the second, termed Sequential Loop Closure, were clearly evident.

Smart Braid Feedback for the Closed-Loop Control of Soft Robotic Systems.

Science.gov (United States)

Felt, Wyatt; Chin, Khai Yi; Remy, C David

2017-09-01

This article experimentally investigates the potential of using flexible, inductance-based contraction sensors in the closed-loop motion control of soft robots. Accurate motion control remains a highly challenging task for soft robotic systems. Precise models of the actuation dynamics and environmental interactions are often unavailable. This renders open-loop control impossible, while closed-loop control suffers from a lack of suitable feedback. Conventional motion sensors, such as linear or rotary encoders, are difficult to adapt to robots that lack discrete mechanical joints. The rigid nature of these sensors runs contrary to the aspirational benefits of soft systems. As truly soft sensor solutions are still in their infancy, motion control of soft robots has so far relied on laboratory-based sensing systems such as motion capture, electromagnetic (EM) tracking, or Fiber Bragg Gratings. In this article, we used embedded flexible sensors known as Smart Braids to sense the contraction of McKibben muscles through changes in inductance. We evaluated closed-loop control on two systems: a revolute joint and a planar, one degree of freedom continuum manipulator. In the revolute joint, our proposed controller compensated for elasticity in the actuator connections. The Smart Braid feedback allowed motion control with a steady-state root-mean-square (RMS) error of [1.5]°. In the continuum manipulator, Smart Braid feedback enabled tracking of the desired tip angle with a steady-state RMS error of [1.25]°. This work demonstrates that Smart Braid sensors can provide accurate position feedback in closed-loop motion control suitable for field applications of soft robotic systems.

Truncated predictor feedback for time-delay systems

CERN Document Server

Zhou, Bin

2014-01-01

This book provides a systematic approach to the design of predictor based controllers for (time-varying) linear systems with either (time-varying) input or state delays. Differently from those traditional predictor based controllers, which are infinite-dimensional static feedback laws and may cause difficulties in their practical implementation, this book develops a truncated predictor feedback (TPF) which involves only finite dimensional static state feedback. Features and topics: A novel approach referred to as truncated predictor feedback for the stabilization of (time-varying) time-delay systems in both the continuous-time setting and the discrete-time setting is built systematically Semi-global and global stabilization problems of linear time-delay systems subject to either magnitude saturation or energy constraints are solved in a systematic manner Both stabilization of a single system and consensus of a group of systems (multi-agent systems) are treated in a unified manner by applying the truncated pre...

RHIC 10 Hz global orbit feedback system

International Nuclear Information System (INIS)

Michnoff, R.; Arnold, L.; Carboni, L.; Cerniglia, P.; Curcio, A.; DeSanto, L.; Folz, C.; Ho, C.; Hoff, L.; Hulsart, R.; Karl, R.; Luo, Y.; Liu, C.; MacKay, W.; Mahler, G.; Meng, W.; Mernick, K.; Minty, M.; Montag, C.; Olsen, R.; Piacentino, J.; Popken, P.; Przybylinski, R.; Ptitsyn, V.; Ritter, J.; Schoenfeld, R.; Thieberger, P.; Tuozzolo, J.; Weston, A.; White, J.; Ziminski, P.; Zimmerman, P.

2011-01-01

Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the horizontal beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including a local beam feedback system at each of the two experimental areas, reinforcing the magnet base support assembly, and a mechanical servo feedback system. However, the local feedback system was insufficient because perturbation amplitudes outside the experimental areas were still problematic, and the mechanical solutions are very expensive. A global 10 Hz orbit feedback system consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two 3.8 km circumference counter-rotating rings has been developed and commissioned in February 2011. A description of the system architecture and results with beam will be discussed.

Daresbury SRS Positional Feedback Systems

CERN Document Server

Smith, S L

2000-01-01

The Daresbury SRS is a second generation synchrotron radiation source which ramps from its injection energy of 600 MeV to 2.0 GeV. Beam orbit feedback systems have been in routine operation on the SRS since 1994 and are now an essential element in delivering stable photon beams to experimental stations. The most recent enhancements to these systems have included the introduction of a ramp servo system to provide the orbit control demanded by the installation of two new narrow gap insertion device and development of the vertical orbit feedback system to cope with an increasing number of photon beamlines. This paper summaries the current status of these systems and briefly discusses proposed developments.

Asymptotic stabilization of nonlinear systems using state feedback

International Nuclear Information System (INIS)

D'Attellis, Carlos

1990-01-01

This paper studies the design of state-feedback controllers for the stabilization of single-input single-output nonlinear systems x = f(x) + g(x)u, y = h(x). Two approaches for the stabilization problem are given; the asymptotic stability is achieved by means of: a) nonlinear state feedback: two nonlinear feedbacks are used; the first separates the system in a controllable linear part and in the zeros-dynamic part. The second feedback generates an asymptotically stable equilibrium on the manifold where this dynamics evolves; b) nonlinear dynamic feedback: conditions are established under which the system can follow the output of a completely controllable bilinear system which uses bounded controls. This fact enables the system to reach, using bounded controls too, a desired output value in finite time. As this value corresponds to a state that lays in the attraction basin of a stable equilibrium with the same output, the system evolves to that point. The two methods are illustrated by examples. (Author) [es

Policy Feedback System (PFS)

Data.gov (United States)

Social Security Administration — The Policy Feedback System (PFS) is a web application developed by the Office of Disability Policy Management Information (ODPMI) team that gathers empirical data...

Can we observe open loop transfer functions in a stochastic feedback system ?

International Nuclear Information System (INIS)

Kishida, Kuniharu; Suda, Nobuhide.

1991-01-01

There are two kinds of problems concerning open loop and closed loop transfer functions in a feedback system. One is a problem even in the deterministic case, and the other is in the stochastic case. In the deterministic case it is guaranteed under a necessary and sufficient condition that total sum of degrees of sub-transfer functions coincides to the degree of the total system. In the stochastic case a systematic understanding of a physical state model, a theoretical innovation model and a data-oriented innovation model is indispensable for determination of open loop transfer functions from time series data. Undesirable factors appear in determination of open loop transfer functions, since a transfer function matrix from input noises to output variables has a redundancy factor of diagonal matrix. (author)

Generalized fast feedback system in the SLC

International Nuclear Information System (INIS)

Hendrickson, L.; Allison, S.; Gromme, T.; Himel, T.; Krauter, K.; Rouse, F.; Sass, R.; Shoaee, H.

1991-11-01

A generalized fast feedback system has been developed to stabilize beams at various locations in the SLC. The system is designed to perform measurements and change actuator settings to control beam states such as position, angle and energy on a pulse to pulse basis. The software design is based on the state space formalism of digital control theory. The system is database-driven, facilitating the addition of new loops without requiring additional software. A communications system, KISNet, provides fast communications links between microprocessors for feedback loops which involve multiple micros. Feedback loops have been installed in seventeen locations throughout the SLC and have proven to be invaluable in stabilizing the machine

Linear feedback control, adaptive feedback control and their combination for chaos (lag) synchronization of LC chaotic systems

International Nuclear Information System (INIS)

Yan Zhenya; Yu Pei

2007-01-01

In this paper, we study chaos (lag) synchronization of a new LC chaotic system, which can exhibit not only a two-scroll attractor but also two double-scroll attractors for different parameter values, via three types of state feedback controls: (i) linear feedback control; (ii) adaptive feedback control; and (iii) a combination of linear feedback and adaptive feedback controls. As a consequence, ten families of new feedback control laws are designed to obtain global chaos lag synchronization for τ < 0 and global chaos synchronization for τ = 0 of the LC system. Numerical simulations are used to illustrate these theoretical results. Each family of these obtained feedback control laws, including two linear (adaptive) functions or one linear function and one adaptive function, is added to two equations of the LC system. This is simpler than the known synchronization controllers, which apply controllers to all equations of the LC system. Moreover, based on the obtained results of the LC system, we also derive the control laws for chaos (lag) synchronization of another new type of chaotic system

Generalized fast feedback system in the SLC

International Nuclear Information System (INIS)

Hendrickson, L.; Allison, S.; Gromme, T.; Himel, T.; Krauter, K.; Rouse, F.; Sass, R.; Shoaee, H.

1992-01-01

A generalized fast feedback system has been developed to stabilize beams at various locations in the SLC. The system is designed to perform measurements and change actuator settings to control beam states such as position, angle and energy on a pulse to pulse basis. The software design is based on the state space formalism of digital control theory. The system is database-driven, facilitating the addition of new loops without requiring additional software. A communications system, KISNet, provides fast communications links between microprocessors for feedback loops which involve multiple micros. Feedback loops have been installed in seventeen locations throughout the SLC and have proven to be invaluable in stabilizing the machine. (author)

Novel Reduced-Feedback Wireless Communication Systems

KAUST Repository

Shaqfeh, Mohammad Obaidah

2011-11-20

Modern communication systems apply channel-aware adaptive transmission techniques and dynamic resource allocation in order to exploit the peak conditions of the fading wireless links and to enable significant performance gains. However, conveying the channel state information among the users’ mobile terminals into the access points of the network consumes a significant portion of the scarce air-link resources and depletes the battery resources of the mobile terminals rapidly. Despite its evident drawbacks, the channel information feedback cannot be eliminated in modern wireless networks because blind communication technologies cannot support the ever-increasing transmission rates and high quality of experience demands of current ubiquitous services. Developing new transmission technologies with reduced-feedback requirements is sought. Network operators will benefit from releasing the bandwidth resources reserved for the feedback communications and the clients will enjoy the extended battery life of their mobile devices. The main technical challenge is to preserve the prospected transmission rates over the network despite decreasing the channel information feedback significantly. This is a noteworthy research theme especially that there is no mature theory for feedback communication in the existing literature despite the growing number of publications about the topic in the last few years. More research efforts are needed to characterize the trade-off between the achievable rate and the required channel information and to design new reduced-feedback schemes that can be flexibly controlled based on the operator preferences. Such schemes can be then introduced into the standardization bodies for consideration in next generation broadband systems. We have recently contributed to this field and published several journal and conference papers. We are the pioneers to propose a novel reduced-feedback opportunistic scheduling scheme that combines many desired features

Normal form and synchronization of strict-feedback chaotic systems

International Nuclear Information System (INIS)

Wang, Feng; Chen, Shihua; Yu Minghai; Wang Changping

2004-01-01

This study concerns the normal form and synchronization of strict-feedback chaotic systems. We prove that, any strict-feedback chaotic system can be rendered into a normal form with a invertible transform and then a design procedure to synchronize the normal form of a non-autonomous strict-feedback chaotic system is presented. This approach needs only a scalar driving signal to realize synchronization no matter how many dimensions the chaotic system contains. Furthermore, the Roessler chaotic system is taken as a concrete example to illustrate the procedure of designing without transforming a strict-feedback chaotic system into its normal form. Numerical simulations are also provided to show the effectiveness and feasibility of the developed methods

Time-optimal feedback control for linear systems

International Nuclear Information System (INIS)

Mirica, S.

1976-01-01

The paper deals with the results of qualitative investigations of the time-optimal feedback control for linear systems with constant coefficients. In the first section, after some definitions and notations, two examples are given and it is shown that even the time-optimal control problem for linear systems with constant coefficients which looked like ''completely solved'' requires a further qualitative investigation of the stability to ''permanent perturbations'' of optimal feedback control. In the second section some basic results of the linear time-optimal control problem are reviewed. The third section deals with the definition of Boltyanskii's ''regular synthesis'' and its connection to Filippov's theory of right-hand side discontinuous differential equations. In the fourth section a theorem is proved concerning the stability to perturbations of time-optimal feedback control for linear systems with scalar control. In the last two sections it is proved that, if the matrix which defines the system has only real eigenvalues or is three-dimensional, the time-optimal feedback control defines a regular synthesis and therefore is stable to perturbations. (author)

Using sampled-data feedback control and linear feedback synchronization in a new hyperchaotic system

International Nuclear Information System (INIS)

Zhao Junchan; Lu Junan

2008-01-01

This paper investigates control and synchronization of a new hyperchaotic system which was proposed by [Chen A, Lu J-A, Lue J, Yu S. Generating hyperchaotic Lue attractor via state feedback control. Physica A 2006;364:103-10]. Firstly, we give different sampled-data feedback control schemes with the variation of system parameter d. Specifically, we only use one controller to drive the system to the origin when d element of (-0.35, 0), and use two controllers if d element of [0, 1.3]. Next, we combine PC method with linear feedback approach to realize synchronization, and derive similar conclusions with varying d. Numerical simulations are also given to validate the proposed approaches

Instabilities simulations with wideband feedback systems: CMAD, HEADTAIL, WARP

International Nuclear Information System (INIS)

Li, Kevin; Cesaratto, J; Fox, J D; Pivi, M; Rivetta, C; Rumolo, G

2013-01-01

Transverse mode coupling (TMCI) and electron cloud instabilities (ECI) pose fundamental limitations on the acceptable beam intensities in the SPS at CERN. This in turn limits the ultimate achievable luminosity in the LHC. Therefore, future luminosity upgrades foresee methods for evading TMCI as well as ECI. Proposed approaches within the LHC Injector Upgrade (LIU) project include new optics with reduced transition energy as well as vacuum chamber coating techniques. As a complementary option, high bandwidth feedback systems may provide instability mitigation by actively damping the intra-bunch motion of unstable modes. In an effort to evaluate the potentials and limitations of such feedback systems and to characterise some of the specifications, a numerical model of a realistic feedback system has been developed and integrated into available instabilities simulation codes. Together with the implementation of this new feedback system model, CMAD and HEADTAIL have been used to investigate the impact of different wideband feedback systems on ECI in the SPS. In this paper, we present some details on the numerical model of the realistic feedback system and its implementation as well as the results obtained from the simulation study using this model together with the instability codes. (author)

PEP-II RF feedback system simulation

Energy Technology Data Exchange (ETDEWEB)

Tighe, R [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

1996-08-01

A model containing the fundamental impedance of the PEP-II cavity along with the longitudinal beam dynamics and RF feedback system components is in use. It is prepared in a format allowing time-domain as well as frequency-domain analysis and full graphics capability. Matlab and Simulink are control system design and analysis programs (widely available) with many built-in tools. The model allows the use of compiled C-code modules for compute intensive portions. We desire to represent as nearly as possible the components of the feedback system including all delays, sample rates and applicable nonlinearities. (author)

Improving School Improvement: Development and Validation of the CSIS-360, a 360-Degree Feedback Assessment for School Improvement Specialists

Science.gov (United States)

McDougall, Christie M.

2013-01-01

The purpose of the mixed methods study was to develop and validate the CSIS-360, a 360-degree feedback assessment to measure competencies of school improvement specialists from multiple perspectives. The study consisted of eight practicing school improvement specialists from a variety of settings. The specialists nominated 23 constituents to…

Entropy as a measure of the noise extent in a two-level quantum feedback controlled system

Institute of Scientific and Technical Information of China (English)

Wang Tao-Bo; Fang Mao-Fa; Hu Yao-Hua

2007-01-01

By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can induce the reduction of the degree of noise, and different control schemes exhibit different noise controlling ability, the extent of the reduction also related with the position of the target state on the Bloch sphere. It is shown that the evolution of entropy can provide a real time noise observation and a systematic guideline to make reasonable choice of control strategy.

Quasi-period oscillations of relay feedback systems

International Nuclear Information System (INIS)

Wen Guilin; Wang Qingguo; Lee, T.H.

2007-01-01

This paper presents an analytical method for investigation of the existence and stability of quasi-period oscillations (torus solutions) for a class of relay feedback systems. The idea is to analyze Poincare map from one switching surface to the next based on the Hopf bifurcation theory of maps. It is shown that there exist quasi-period oscillations in certain relay feedback systems

Direct output feedback control of discrete-time systems

International Nuclear Information System (INIS)

Lin, C.C.; Chung, L.L.; Lu, K.H.

1993-01-01

An optimal direct output feedback control algorithm is developed for discrete-time systems with the consideration of time delay in control force action. Optimal constant output feedback gains are obtained through variational process such that certain prescribed quadratic performance index is minimized. Discrete-time control forces are then calculated from the multiplication of output measurements by these pre-calculated feedback gains. According to the proposed algorithm, structural system is assured to remain stable even in the presence of time delay. The number of sensors and controllers may be very small as compared with the dimension of states. Numerical results show that direct velocity feedback control is more sensitive to time delay than state feedback but, is still quite effective in reducing the dynamic responses under earthquake excitation. (author)

Rateless feedback codes

DEFF Research Database (Denmark)

Sørensen, Jesper Hemming; Koike-Akino, Toshiaki; Orlik, Philip

2012-01-01

This paper proposes a concept called rateless feedback coding. We redesign the existing LT and Raptor codes, by introducing new degree distributions for the case when a few feedback opportunities are available. We show that incorporating feedback to LT codes can significantly decrease both...... the coding overhead and the encoding/decoding complexity. Moreover, we show that, at the price of a slight increase in the coding overhead, linear complexity is achieved with Raptor feedback coding....

Novel Reduced-Feedback Wireless Communication Systems

KAUST Repository

Shaqfeh, Mohammad Obaidah; Alnuweiri, Hussein; Alouini, Mohamed-Slim

2011-01-01

We have recently contributed to this field and published several journal and conference papers. We are the pioneers to propose a novel reduced-feedback opportunistic scheduling scheme that combines many desired features including fairness in resources distribution across the active terminals and distributed processing at the MAC layer level. In addition our scheme operates close to the upper capacity limits of achievable transmission rates over wireless links. We have also proposed another hybrid scheme that enables adjusting the feedback load flexibly based on rates requirements. We are currently investigating other novel ideas to design reduced-feedback communication systems.

Combined feedforward and feedback control of a redundant, nonlinear, dynamic musculoskeletal system.

Science.gov (United States)

Blana, Dimitra; Kirsch, Robert F; Chadwick, Edward K

2009-05-01

A functional electrical stimulation controller is presented that uses a combination of feedforward and feedback for arm control in high-level injury. The feedforward controller generates the muscle activations nominally required for desired movements, and the feedback controller corrects for errors caused by muscle fatigue and external disturbances. The feedforward controller is an artificial neural network (ANN) which approximates the inverse dynamics of the arm. The feedback loop includes a PID controller in series with a second ANN representing the nonlinear properties and biomechanical interactions of muscles and joints. The controller was designed and tested using a two-joint musculoskeletal model of the arm that includes four mono-articular and two bi-articular muscles. Its performance during goal-oriented movements of varying amplitudes and durations showed a tracking error of less than 4 degrees in ideal conditions, and less than 10 degrees even in the case of considerable fatigue and external disturbances.

360 Degree Feedback: An Integrative Framework for Learning and Assessment

Science.gov (United States)

Tee, Ding Ding; Ahmed, Pervaiz K.

2014-01-01

Feedback is widely acknowledged as the crux of a learning process. Multiplicities of research studies have been advanced to address the common "cri de coeur" of teachers and students for a constructive and effective feedback mechanism in the current higher educational settings. Nevertheless, existing pedagogical approaches in feedback…

Longitudinal feedback system for PEP

International Nuclear Information System (INIS)

Allen, M.A.; Cornacchia, M.; Millich, A.

1979-02-01

Whether the wide bandwidth longitudinal feedback system described in this paper is made to act on the individual modes in frequency domain or on the individual bunches in time domain, it represents a clean and efficient way of damping the longitudinal oscillations without influencing other beam parameters such as bunch shape or synchrotron frequency distribution. The frequency domain feedback presents the advantage of providing information on which modes are unstable and on their risetimes, which may be helpful in locating dangerous resonators in the ring

PID position regulation in one-degree-of-freedom Euler-Lagrange systems actuated by a PMSM

Science.gov (United States)

Verastegui-Galván, J.; Hernández-Guzmán, V. M.; Orrante-Sakanassi, J.

2018-02-01

This paper is concerned with position regulation in one-degree-of-freedom Euler-Lagrange Systems. We consider that the mechanical subsystem is actuated by a permanent magnet synchronous motor (PMSM). Our proposal consists of a Proportional-Integral-Derivative (PID) controller for the mechanical subsystem and a slight variation of field oriented control for the PMSM. We take into account the motor electric dynamics during the stability analysis. We present, for the first time, a global asymptotic stability proof for such a control scheme without requiring the mechanical subsystem to naturally possess viscous friction. Finally, as a corollary of our main result we prove global asymptotic stability for output feedback PID regulation of one-degree-of-freedom Euler-Lagrange systems when generated torque is considered as the system input, i.e. when the electric dynamics of PMSM's is not taken into account.

Designing new feedback mangement system Långvik

OpenAIRE

Dang, Hien

2014-01-01

This thesis is a design project on the field of feedback management, conducted for Långvik hotel. The purpose of this thesis is to recommend a new feedback management system for the hotel that can effectively recognize original reasons for customers’ returning decision. The new approach to feedback management is expected to generate a higher number of re- turned customers subsequent to the summer business peak. The literature review focuses on the connection between customer experience and...

Leadership development in a professional medical society using 360-degree survey feedback to assess emotional intelligence.

Science.gov (United States)

Gregory, Paul J; Robbins, Benjamin; Schwaitzberg, Steven D; Harmon, Larry

2017-09-01

The current research evaluated the potential utility of a 360-degree survey feedback program for measuring leadership quality in potential committee leaders of a professional medical association (PMA). Emotional intelligence as measured by the extent to which self-other agreement existed in the 360-degree survey ratings was explored as a key predictor of leadership quality in the potential leaders. A non-experimental correlational survey design was implemented to assess the variation in leadership quality scores across the sample of potential leaders. A total of 63 of 86 (76%) of those invited to participate did so. All potential leaders received feedback from PMA Leadership, PMA Colleagues, and PMA Staff and were asked to complete self-ratings regarding their behavior. Analyses of variance revealed a consistent pattern of results as Under-Estimators and Accurate Estimators-Favorable were rated significantly higher than Over-Estimators in several leadership behaviors. Emotional intelligence as conceptualized in this study was positively related to overall performance ratings of potential leaders. The ever-increasing roles and potential responsibilities for PMAs suggest that these organizations should consider multisource performance reviews as these potential future PMA executives rise through their organizations to assume leadership positions with profound potential impact on healthcare. The current findings support the notion that potential leaders who demonstrated a humble pattern or an accurate pattern of self-rating scored significantly higher in their leadership, teamwork, and interpersonal/communication skills than those with an aggrandizing self-rating.

Object discrimination using electrotactile feedback.

Science.gov (United States)

Arakeri, Tapas J; Hasse, Brady A; Fuglevand, Andrew J

2018-04-09

A variety of bioengineering systems are being developed to restore tactile sensations in individuals who have lost somatosensory feedback because of spinal cord injury, stroke, or amputation. These systems typically detect tactile force with sensors placed on an insensate hand (or prosthetic hand in the case of amputees) and deliver touch information by electrically or mechanically stimulating sensate skin above the site of injury. Successful object manipulation, however, also requires proprioceptive feedback representing the configuration and movements of the hand and digits. Therefore, we developed a simple system that simultaneously provides information about tactile grip force and hand aperture using current amplitude-modulated electrotactile feedback. We evaluated the utility of this system by testing the ability of eight healthy human subjects to distinguish among 27 objects of varying sizes, weights, and compliances based entirely on electrotactile feedback. The feedback was modulated by grip-force and hand-aperture sensors placed on the hand of an experimenter (not visible to the subject) grasping and lifting the test objects. We were also interested to determine the degree to which subjects could learn to use such feedback when tested over five consecutive sessions. The average percentage correct identifications on day 1 (28.5%  ±  8.2% correct) was well above chance (3.7%) and increased significantly with training to 49.2%  ±  10.6% on day 5. Furthermore, this training transferred reasonably well to a set of novel objects. These results suggest that simple, non-invasive methods can provide useful multisensory feedback that might prove beneficial in improving the control over prosthetic limbs.

The system Cu-Rh-S at 900 degrees, 700 degrees, 540 degrees and 500 degrees C

DEFF Research Database (Denmark)

Karup-Møller, Sven; Makovicky, E.

2007-01-01

Phase relations in the dry condensed system Cu-Rh-S were determined at 900, 700, 540 and 500 degrees C. At 900 degrees C, the system contains digenite, four rhodium sulfides (Rh17S15, Rh3S4, Rh2S3 and RhS similar to 3), three ternary sulfides (CuRh2S4, CuxRhS3+x and a fibrous sulfide in the range...

Delayed feedback control of fractional-order chaotic systems

International Nuclear Information System (INIS)

Gjurchinovski, A; Urumov, V; Sandev, T

2010-01-01

We study the possibility to stabilize unstable steady states and unstable periodic orbits in chaotic fractional-order dynamical systems by the time-delayed feedback method. By performing a linear stability analysis, we establish the parameter ranges for successful stabilization of unstable equilibria in the plane parameterized by the feedback gain and the time delay. An insight into the control mechanism is gained by analyzing the characteristic equation of the controlled system, showing that the control scheme fails to control unstable equilibria having an odd number of positive real eigenvalues. We demonstrate that the method can also stabilize unstable periodic orbits for a suitable choice of the feedback gain, providing that the time delay is chosen to coincide with the period of the target orbit. In addition, it is shown numerically that delayed feedback control with a sinusoidally modulated time delay significantly enlarges the stability region of steady states in comparison to the classical time-delayed feedback scheme with a constant delay.

Corresponding Angle Feedback in an innovative weighted transportation system

International Nuclear Information System (INIS)

Dong Chuanfei; Ma Xu

2010-01-01

The optimal information feedback has a significant effect on many socioeconomic systems like stock market and traffic systems aiming to make full use of resources. In this Letter, we study dynamics of traffic flow with real-time information. The influence of a feedback strategy named Corresponding Angle Feedback Strategy (CAFS) is introduced, based on a two-route scenario in which dynamic information can be generated and displayed on the board to guide road users to make a choice. Our model incorporates the effects of adaptability into the cellular automaton models of traffic flow and simulation results adopting this optimal information feedback strategy have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the other three information feedback strategies, i.e., vehicle number and flux.

Ideal and conventional feedback systems for RWM suppression

International Nuclear Information System (INIS)

Pustovitov, V.D.

2002-01-01

Feedback suppression of resistive wall modes (RWM) is studied analytically using a model based on a standard cylindrical approximation. Two feedback systems are compared: 'ideal', creating only the field necessary for RMW suppression, and 'conventional', like that used in the DIII-D tokamak and considered as a candidate for ITER. The widespread opinion that the feedback with poloidal sensors is better than that with radial sensors is discussed. It is shown that the 'conventional' feedback with radial sensors can be effective only in a limited range, while using the input signal from internal poloidal sensors allows easy fulfilment of the stability criterion. This is a property of the 'conventional' feedback, but the 'ideal' feedback would stabilise RWM in both cases. (author)

Augmenting Environmental Interaction in Audio Feedback Systems

Directory of Open Access Journals (Sweden)

Seunghun Kim

2016-04-01

Full Text Available Audio feedback is defined as a positive feedback of acoustic signals where an audio input and output form a loop, and may be utilized artistically. This article presents new context-based controls over audio feedback, leading to the generation of desired sonic behaviors by enriching the influence of existing acoustic information such as room response and ambient noise. This ecological approach to audio feedback emphasizes mutual sonic interaction between signal processing and the acoustic environment. Mappings from analyses of the received signal to signal-processing parameters are designed to emphasize this specificity as an aesthetic goal. Our feedback system presents four types of mappings: approximate analyses of room reverberation to tempo-scale characteristics, ambient noise to amplitude and two different approximations of resonances to timbre. These mappings are validated computationally and evaluated experimentally in different acoustic conditions.

Predictor feedback for delay systems implementations and approximations

CERN Document Server

Karafyllis, Iasson

2017-01-01

This monograph bridges the gap between the nonlinear predictor as a concept and as a practical tool, presenting a complete theory of the application of predictor feedback to time-invariant, uncertain systems with constant input delays and/or measurement delays. It supplies several methods for generating the necessary real-time solutions to the systems’ nonlinear differential equations, which the authors refer to as approximate predictors. Predictor feedback for linear time-invariant (LTI) systems is presented in Part I to provide a solid foundation on the necessary concepts, as LTI systems pose fewer technical difficulties than nonlinear systems. Part II extends all of the concepts to nonlinear time-invariant systems. Finally, Part III explores extensions of predictor feedback to systems described by integral delay equations and to discrete-time systems. The book’s core is the design of control and observer algorithms with which global stabilization, guaranteed in the previous literature with idealized (b...

Feedbacks between conservation and social-ecological systems

Science.gov (United States)

Miller, Brian W.; Caplow, Susan C.; Leslie, Paul W.

2012-01-01

Robust ways to meet objectives of environmental conservation and social and economic development remain elusive. This struggle may in part be related to insufficient understanding of the feedbacks between conservation initiatives and social-ecological systems, specifically, the ways in which conservation initiatives result in social changes that have secondary effects on the environments targeted by conservation. To explore this idea we sampled peer-reviewed articles addressing the social and environmental dimensions of conservation and coded each paper according to its research focus and characterization of these feedbacks. The majority of articles in our sample focused either on the effect of conservation initiatives on people (e.g., relocation, employment) or the effect of people on the environment (e.g., fragmentation, conservation efficacy of traditional management systems). Few studies in our sample empirically addressed both the social dynamics resulting from conservation initiatives and subsequent environmental effects. In many cases, one was measured and the other was discussed anecdotally. Among the studies that describe feedbacks between social and environmental variables, there was more evidence of positive (amplifying) feedbacks between social and environmental outcomes (i.e., undesirable social outcomes yielded undesirable environmental effects, and desirable social outcomes yielded desirable environmental effects). The major themes within the sampled literature include conflict between humans and wild animals, social movements, adaptive comanagement, loss of traditional management systems, traditional ecological knowledge, human displacement and risks to livelihoods, and conservation and development. The narratives associated with each theme can serve as hypotheses for facilitating further discussion about conservation issues and for catalyzing future studies of the feedbacks between conservation and social-ecological systems. PMID:22443128

Beam position feedback system for the advanced photon source

International Nuclear Information System (INIS)

Chung, Y.

1994-01-01

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and x-ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4 kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and x-ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back to the global orbit data to the local feedback systems. The effect of the eddy current induced in the relatively thick (1/2 in.) vacuum chamber by the ac corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the x-ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will also be presented

Beam position feedback system for the advanced photon source

International Nuclear Information System (INIS)

Chung, Y.

1994-01-01

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4 kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and X-ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back the global orbit data to the local feedback systems. The effect of the vacuum chamber eddy current induced by the AC corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the X-ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will be presented. copyright 1994 American Institute of Physics

Beam position feedback system for the Advanced Photon Source

International Nuclear Information System (INIS)

Chung, Y.

1993-01-01

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and X-ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back the global orbit data to the local feedback systems. The effect of the vacuum chamber eddy current induced by the AC corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the X-ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will be presented

Beam position feedback system for the Advanced Photon Source

International Nuclear Information System (INIS)

Chung, Y.

1993-01-01

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and X-ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back the global orbit data to the local feedback systems. The effect of the eddy current induced in the relatively thick (1/2 inch) vacuum chamber by the AC corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the X-ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will also be presented

Ideal and conventional feedback systems for RWM suppression

Energy Technology Data Exchange (ETDEWEB)

Pustovitov, V.D.

2002-01-01

Feedback suppression of resistive wall modes (RWM) is studied analytically using a model based on a standard cylindrical approximation. Two feedback systems are compared: 'ideal', creating only the field necessary for RMW suppression, and 'conventional', like that used in the DIII-D tokamak and considered as a candidate for ITER. The widespread opinion that the feedback with poloidal sensors is better than that with radial sensors is discussed. It is shown that the 'conventional' feedback with radial sensors can be effective only in a limited range, while using the input signal from internal poloidal sensors allows easy fulfilment of the stability criterion. This is a property of the 'conventional' feedback, but the 'ideal' feedback would stabilise RWM in both cases. (author)

Theoretical treatment of transverse feedback systems with memory

International Nuclear Information System (INIS)

Cornacchia, M.; Wang, J.M.

1981-01-01

The differential equation of the dipole moment of coherent oscillations in the presence of a feedback system is derived. The analysis, which starts in the time domain, is extended to the frequency domain; this allows a straightforward derivation of the damping rate for both coasting and bunched beams. The damping rate is expressed in terms of the transfer function of the feedback system and in a general form which takes into account the β-function and betatron phase modulation along the beam trajectory, the effect of memory arising from the finiteness of the system bandwidth, the effect of the time delay and of the betatron phase advance between detector and kicker. Some examples of the dependence of the damping rate on the feedback parameters are given

Instabilities simulations with wideband feedback systems: CMAD, HEADTAIL, WARP

CERN Document Server

Li, Kevin; Fox, J D; Pivi, M; Rivetta, C; Rumolo, G

2013-01-01

Transverse mode coupling (TMCI) and electron cloud instabilities (ECI) pose fundamental limitations on the acceptable beam intensities in the SPS at CERN. This in turn limits the ultimate achievable luminosity in the LHC. Therefore, future luminosity upgrades foresee methods for evading TMCI as well as ECI. Proposed approaches within the LHC Injector Upgrade (LIU) project include new optics with reduced transition energy as well as vacuum chamber coating techniques. As a complementary option, high bandwidth feedback systems may provide instability mitigation by actively damping the intra-bunch motion of unstable modes. In an effort to evaluate the potentials and limitations of such feedback systems and to characterise some of the specifications, a numerical model of a realistic feedback system has been developed and integrated into available instabilities simulation codes. Together with the implementation of this new feedback system model, CMAD and HEADTAIL have been used to investigate the impact of differen...

Weighted congestion coefficient feedback in intelligent transportation systems

International Nuclear Information System (INIS)

Dong Chuanfei; Ma Xu; Wang Binghong

2010-01-01

In traffic systems, a reasonable information feedback can improve road capacity. In this Letter, we study dynamics of traffic flow with real-time information. And the influence of a feedback strategy named Weighted Congestion Coefficient Feedback Strategy (WCCFS) is introduced, based on a two-route scenario in which dynamic information can be generated and displayed on the board to guide road users to make a choice. Our model incorporates the effects of adaptability into the cellular automaton models of traffic flow and simulation results adopting this optimal information feedback strategy have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the other three information feedback strategies, i.e., vehicle number and flux.

Operation of the transverse feedback system at the CERN SPS

International Nuclear Information System (INIS)

Bossart, R.; Louwerse, R.; Mourier, J.; Vos, L.

1987-01-01

To prevent transverse instabilities at high beam intensity in the SPS, the transverse feedback system for damping the betatron oscillations has been upgraded for larger damping decrements and for increased system's bandwidth. The feedback loop now contains a digital delay line cancellor, so that the damper works with a velocity feedback Δx/Δt, unaffected by the closed orbit position x at the pick-up station. The digital processing of the feedback signal facilitates nonlinear feedback techniques such as antidamping and ''band-bang'' feedback. The ''bang-bang'' feedback provides the maximum possible damping rate of the injection oscillations in the SPS-collider, in order to minimize the emittance increase caused by filamentation. The antidamping nonlinearity provides small continuous beam oscillations of 50 μm amplitude for tracking the machine tune Q with a phase locked loop

Event-Triggered Output-Feedback Control for Disturbed Linear Systems

Directory of Open Access Journals (Sweden)

Hao Jiang

2018-01-01

Full Text Available In the last few decades, event-triggered control received considerable attention, because of advantages in reducing the resource utilization, such as communication load and processor. In this paper, we propose an event-triggered output-feedback controller for disturbed linear systems, in order to achieve both better resource utilization and disturbance attenuation properties at the same time. Based on our prior work on state-feedback H∞ control for disturbed systems, we propose an approach to design an output-feedback H∞ controller for the system whose states are not completely observable, and a sufficient condition guaranteeing the asymptotic stability and robustness of the system is given in the form of LMIs (Linear Matrix Inequalities.

Synchronizing strict-feedback and general strict-feedback chaotic systems via a single controller

International Nuclear Information System (INIS)

Chen Shihua; Wang Feng; Wang Changping

2004-01-01

We present a systematic design procedure to synchronize a class of chaotic systems in a so-called strict-feedback form based on back-stepping procedure. This approach needs only a single controller to realize synchronization no matter how many dimensions the chaotic system contains. Furthermore, we point out that the method does not work for general strict-feedback chaotic systems, for instance, Lorenz system. Therefore, we propose three kinds of synchronization schemes for Lorenz system using the Lyapunov function method. All the three schemes avoid including divergence factor as in Ref. [Chaos, Solitons and Fractals 16 (2003) 37]. Especially in the last two schemes, we need only one state variable in controller, which has important significance in chaos synchronization used for communication purposes. Finally numerical simulations are provided to show the effectiveness and feasibility of the developed methods

Feedback Control of a Class of Nonholonomic Hamiltonian Systems

DEFF Research Database (Denmark)

Sørensen, Mathias Jesper

Feedback control of nonholonomic systems has always been problematic due to the nonholonomic constraints that limit the space of possible system velocities. This property is very basic, and Brockett proved that a nonholonomic system cannot be asymptotically stabilized by a time-invariant smooth...... turns out to be useful when stabilizing the nonholonomic system. If the system is properly actuated it is possible to asymptotically stabilize the primary part of the configuration coordinates via a passive energy shaping and damping injecting feedback. The feedback is smooth and time......-invariant, but since it does not asymptotically stabilize the secondary part of the configuration coordinates, it does not violate Brockett’s obstruction. The results fromthe general class of nonholonomicHamiltonian systems with kinematic inputs are applied to a real implementation of a four wheel steered, four wheel...

Feedback authoring possibilities in web-based learning systems

NARCIS (Netherlands)

Vasilyeva, E.; De Bra, P.M.E.; Pechenizkiy, M.; Bonk, C.J.; et al., xx

2008-01-01

This paper surveys and analyses the feedback authoring possibilities in online assessment modules of the most popular Learning Management Systems (LMS) including Moodle, Sakai, and Blackboard. We consider the problem of authoring and support of tailored and personalized feedback and demonstrate how

The fast correction coil feedback control system

International Nuclear Information System (INIS)

Coffield, F.; Caporaso, G.; Zentler, J.M.

1989-01-01

A model-based feedback control system has been developed to correct beam displacement errors in the Advanced Test Accelerator (ATA) electron beam accelerator. The feedback control system drives an X/Y dipole steering system that has a 40-MHz bandwidth and can produce ±300-Gauss-cm dipole fields. A simulator was used to develop the control algorithm and to quantify the expected performance in the presence of beam position measurement noise and accelerator timing jitter. The major problem to date has been protecting the amplifiers from the voltage that is inductively coupled to the steering bars by the beam. 3 refs., 8 figs

Construction of experience feedback system for equipment supervision in nuclear engineering

International Nuclear Information System (INIS)

Zou Pingguo; Zhang Liying; Zhang Wenzhong

2009-01-01

Based on the analysis of the experience sources on equipment supervision in nuclear engineering, the details of the organization principle, working flow, and report requirement for the experience feedback system are introduced. The function range and its roll in the experience feedback system of the nuclear authority, nuclear power plant owners and equipment supervision organizations are illustrated. The standardization working requirements in the information gathering, analyzing, feedback and tracking process, and the characteristics and form of the incident report and feedback report are proposed. It emphasizes that the method for combined analysis of one significant incident and the whole incidents shall be adopted in the information analysis, and the experience feedback shall be considered in the development of equipment supervision technique and the equipment manufacturing, thus to maximize the use of experience feedback information to improve the pertinency and effectiveness of the experience feedback system. (authors)

Design of output feedback controller for a unified chaotic system

International Nuclear Information System (INIS)

Li Wenlin; Chen Xiuqin; Shen Zhiping

2008-01-01

In this paper, the synchronization of a unified chaotic system is investigated by the use of output feedback controllers; a two-input single-output feedback controller and single-input single-output feedback controller are presented to synchronize the unified chaotic system when the states are not all measurable. Compared with the existing results, the controllers designed in this paper have some advantages such as small feedback gain, simple structure and less conservation. Finally, numerical simulations results are provided to demonstrate the validity and effectiveness of the proposed method

Development of bunch by bunch transverse feedback system at Hefei light source

International Nuclear Information System (INIS)

Wang Junhua; Zheng Kai; Li Weimin; Yang Yongliang; Huang Longjun; Chen Yuanbo; Zhou Zeran; Wang Lin; Liu Zeping; Sun Baogen; Ma Li; Cao Jianshe; Yue Junhui; Liu Dekang; Ye Kairong

2008-01-01

This paper has introduced the development of the transverse bunch-by-bunch measurement and feedback system, including the experiment of damping the coupled bunch instability. Some key technologies on the system have been introduced: the vector calculation module as a signal processing module used to adjust the phase of the feedback signals, the feedback kicker cavity and the notch filter used to filter the DC component and revolution frequencies component in a signal and save the feedback power. The result of the feedback experiment is mentioned: the instability oscillation was damped when the feedback system was on. (authors)

Modeling and simulation of Indus-2 RF feedback control system

International Nuclear Information System (INIS)

Sharma, D.; Bagduwal, P.S.; Tiwari, N.; Lad, M.; Hannurkar, P.R.

2012-01-01

Indus-2 synchrotron radiation source has four RF stations along with their feedback control systems. For higher beam energy and current operation amplitude and phase feedback control systems of Indus-2 are being upgraded. To understand the behaviour of amplitude and phase control loop under different operating conditions, modelling and simulation of RF feedback control system is done. RF cavity baseband I/Q model has been created due to its close correspondence with actual implementation and better computational efficiency which makes the simulation faster. Correspondence between cavity baseband and RF model is confirmed by comparing their simulation results. Low Level RF (LLRF) feedback control system simulation is done using the same cavity baseband I/Q model. Error signals are intentionally generated and response of the closed loop system is observed. Simulation will help us in optimizing parameters of upgraded LLRF system for higher beam energy and current operation. (author)

Coherent versus Measurement Feedback: Linear Systems Theory for Quantum Information

Directory of Open Access Journals (Sweden)

Naoki Yamamoto

2014-11-01

Full Text Available To control a quantum system via feedback, we generally have two options in choosing a control scheme. One is the coherent feedback, which feeds the output field of the system, through a fully quantum device, back to manipulate the system without involving any measurement process. The other one is measurement-based feedback, which measures the output field and performs a real-time manipulation on the system based on the measurement results. Both schemes have advantages and disadvantages, depending on the system and the control goal; hence, their comparison in several situations is important. This paper considers a general open linear quantum system with the following specific control goals: backaction evasion, generation of a quantum nondemolished variable, and generation of a decoherence-free subsystem, all of which have important roles in quantum information science. Some no-go theorems are proven, clarifying that those goals cannot be achieved by any measurement-based feedback control. On the other hand, it is shown that, for each control goal there exists a coherent feedback controller accomplishing the task. The key idea to obtain all the results is system theoretic characterizations of the above three notions in terms of controllability and observability properties or transfer functions of linear systems, which are consistent with their standard definitions.

Diamond Light Source Booster fast orbit feedback system

International Nuclear Information System (INIS)

Gayadeen, S.; Duncan, S.R.; Christou, C.; Heron, M.T.; Rowland, J.

2012-01-01

The Fast Orbit Feedback system that has been installed on the Diamond Light Source Storage ring has been replicated on the Booster synchrotron in order to provide a test bed for the development of the Storage Ring controller design. To realise this the Booster is operated in DC mode. The electron beam is regulated in two planes using the Fast Orbit Feedback system, which takes the beam position from 22 beam position monitors for each plane, and calculates offsets to 44 corrector power supplies at a sample rate of 10 kHz. This paper describes the design and realization of the controller for the Booster Fast Orbit Feedback, presents results from the implementation and considers future development

Nonclassical state generation for linear quantum systems via nonlinear feedback control

International Nuclear Information System (INIS)

Ohki, Kentaro; Tsumura, Koji; Takeuchi, Reiji

2017-01-01

In this paper, we propose a measurement nonlinear feedback control scheme to generate Wigner-function negativity in an optical cavity having dynamics described as a linear quantum system. In general, linear optical quantum systems can be easily constructed with reliable devices; therefore, the idea of constructing the entire system with such an optical system and nonlinear feedback is reasonable for generating Wigner-function negativity. However, existing studies have insufficiently examined the realizability or actual implementation of feedback control, which essentially requires fast responses from the sensors and actuators. In order to solve this problem, we consider the realizable feedback control of the optical phase of a pumping beam supplied to a cavity by using electro-optical modulation, which can be utilized as a fast control actuator. Then, we introduce mathematical models of the feedback-controlled system and evaluate its effect on the generation of the Wigner-function negativity by using numerical simulation. Through various numerical simulations, we show that the proposed feedback control can effectively generate the negativity of the Wigner function. (paper)

PLS beam position measurement and feedback system

International Nuclear Information System (INIS)

Huang, J.Y.; Lee, J.; Park, M.K.; Kim, J.H.; Won, S.C.

1992-01-01

A real-time orbit correction system is proposed for the stabilization of beam orbit and photon beam positions in Pohang Light Source. PLS beam position monitoring system is designed to be VMEbus compatible to fit the real-time digital orbit feedback system. A VMEbus based subsystem control computer, Mil-1553B communication network and 12 BPM/PS machine interface units constitute digital part of the feedback system. With the super-stable PLS correction magnet power supply, power line frequency noise is almost filtered out and the dominant spectra of beam obtit fluctuations are expected to appear below 15 Hz. Using DSP board in SCC for the computation and using an appropriate compensation circuit for the phase delay by the vacuum chamber, PLS real-time orbit correction system is realizable without changing the basic structure of PLS computer control system. (author)

Operational status of the transverse multibunch feedback system at Diamond

International Nuclear Information System (INIS)

Uzun, I.; Abbott, M.; Heron, M.T.; Morgan, A.F.D.; Rehm, G.

2012-01-01

A transverse multibunch feedback (TMBF) system is in operation at Diamond Light Source to damp coupled-bunch instabilities up to 250 MHz in both the vertical and horizontal planes. It comprises an in-house designed and built analogue front end combined with a Libera Bunch-by-Bunch feedback processor and output stripline kickers. FPGA-based feedback electronics is used to implement several diagnostic features in addition to the basic feedback functionality. This paper reports on the current operational status of the TMBF system along with its characteristics. Also discussed are operational diagnostic functionalities including continuous measurement of the betatron tune and chromaticity. (authors)

KEKB bunch feedback systems

Energy Technology Data Exchange (ETDEWEB)

Tobiyama, M; Kikutani, E [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

1996-08-01

Design and the present status of the bunch by bunch feedback systems for KEKB rings are shown. The detection of the bunch oscillation are made with the phase detection for longitudinal plane, the AM/PM method for transverse plane. Two GHz component of the bunch signal which is extracted with an analog FIR filter is used for the detection. Hardware two-tap FIR filter systems to shift the phase of the oscillation by 90deg will be used for the longitudinal signal processing. The same system will be used with no filtering but with only digital delay for transverse system. The candidate for the kicker and the required maximum power are also estimated. (author)

Feedback loop compensates for rectifier nonlinearity

Science.gov (United States)

1966-01-01

Signal processing circuit with two negative feedback loops rectifies two sinusoidal signals which are 180 degrees out of phase and produces a single full-wave rectified output signal. Each feedback loop incorporates a feedback rectifier to compensate for the nonlinearity of the circuit.

Dynamics and control of a financial system with time-delayed feedbacks

International Nuclear Information System (INIS)

Chen, W.-C.

2008-01-01

Complex behaviors in a financial system with time-delayed feedbacks are discussed in this study via numerical modeling. The system shows complex dynamics such as periodic, quasi-periodic, and chaotic behaviors. Both period doubling and inverse period doubling routes were found in this system. This paper also shows that the attractor merging crisis is a fundamental feature of nonlinear financial systems with time-delayed feedbacks. Control of the deterministic chaos in the financial system can be realized using Pyragas feedbacks

Diversity in School Performance Feedback Systems

Science.gov (United States)

Verhaeghe, Goedele; Schildkamp, Kim; Luyten, Hans; Valcke, Martin

2015-01-01

As data-based decision making is receiving increased attention in education, more and more school performance feedback systems (SPFSs) are being developed and used worldwide. These systems provide schools with data on their functioning. However, little research is available on the characteristics of the different SPFSs. Therefore, this study…

Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems

Science.gov (United States)

Xia, Feng; Ma, Longhua; Peng, Chen; Sun, Youxian; Dong, Jinxiang

2008-01-01

There is a trend towards using wireless technologies in networked control systems. However, the adverse properties of the radio channels make it difficult to design and implement control systems in wireless environments. To attack the uncertainty in available communication resources in wireless control systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS) scheme is developed, which takes advantage of the co-design of control and wireless communications. By exploiting cross-layer design, CLAFS adjusts the sampling periods of control systems at the application layer based on information about deadline miss ratio and transmission rate from the physical layer. Within the framework of feedback scheduling, the control performance is maximized through controlling the deadline miss ratio. Key design parameters of the feedback scheduler are adapted to dynamic changes in the channel condition. An event-driven invocation mechanism for the feedback scheduler is also developed. Simulation results show that the proposed approach is efficient in dealing with channel capacity variations and noise interference, thus providing an enabling technology for control over WLAN. PMID:27879934

Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems

Directory of Open Access Journals (Sweden)

Jinxiang Dong

2008-07-01

Full Text Available There is a trend towards using wireless technologies in networked control systems. However, the adverse properties of the radio channels make it difficult to design and implement control systems in wireless environments. To attack the uncertainty in available communication resources in wireless control systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS scheme is developed, which takes advantage of the co-design of control and wireless communications. By exploiting crosslayer design, CLAFS adjusts the sampling periods of control systems at the application layer based on information about deadline miss ratio and transmission rate from the physical layer. Within the framework of feedback scheduling, the control performance is maximized through controlling the deadline miss ratio. Key design parameters of the feedback scheduler are adapted to dynamic changes in the channel condition. An eventdriven invocation mechanism for the feedback scheduler is also developed. Simulation results show that the proposed approach is efficient in dealing with channel capacity variations and noise interference, thus providing an enabling technology for control over WLAN.

Control of uncertain systems by feedback linearization with neural networks augmentation. Part II. Controller validation by numerical simulation

Directory of Open Access Journals (Sweden)

Adrian TOADER

2010-09-01

Full Text Available The paper was conceived in two parts. Part I, previously published in this journal, highlighted the main steps of adaptive output feedback control for non-affine uncertain systems, having a known relative degree. The main paradigm of this approach was the feedback linearization (dynamic inversion with neural network augmentation. Meanwhile, based on new contributions of the authors, a new paradigm, that of robust servomechanism problem solution, has been added to the controller architecture. The current Part II of the paper presents the validation of the controller hereby obtained by using the longitudinal channel of a hovering VTOL-type aircraft as mathematical model.

Minimal-Inversion Feedforward-And-Feedback Control System

Science.gov (United States)

Seraji, Homayoun

1990-01-01

Recent developments in theory of control systems support concept of minimal-inversion feedforward-and feedback control system consisting of three independently designable control subsystems. Applicable to the control of linear, time-invariant plant.

A method for calculating active feedback system to provide vertical

Indian Academy of Sciences (India)

The active feedback system is applied to control slow motions of plasma. The objective of the ... The other problem is connected with the control of plasma vertical position with active feedback system. Calculation of ... Current Issue Volume 90 ...

The efficacy of an automated feedback system for general practitioners

NARCIS (Netherlands)

Bindels, Rianne; Hasman, Arie; Kester, Arnold D.; Talmon, Jan L.; de Clercq, Paul A.; Winkens, Ron A. G.

2003-01-01

OBJECTIVE: An automated feedback system that produces comments about the non-adherence of general practitioners (GPs) to accepted practice guidelines for ordering diagnostic tests was developed. Before implementing the automated feedback system in daily practice, we assessed the potential effect of

Fast digital feedback control systems for accelerator RF system using FPGA

International Nuclear Information System (INIS)

Bagduwal, Pritam Singh; Sharma, Dheeraj; Tiwari, Nitesh; Lad, M.; Hannurkar, P.R.

2012-01-01

Feedback control system plays important role for proper injection and acceleration of beam in particle accelerators by providing the required amplitude and phase stability of RF fields in accelerating structures. Advancement in the field of digital technology enables us to develop fast digital feedback control system for RF applications. Digital Low Level RF (LLRF) system offers the inherent advantages of Digital System like flexibility, adaptability, good repeatability and reduced long time drift errors compared to analog system. To implement the feedback control algorithm, I/Q control scheme is used. By properly sampling the down converted IF signal using fast ADC we get accurate feedback signal and also eliminates the need of two separate detectors for amplitude and phase detection. Controller is implemented in Vertex-4 FPGA. Codes for control algorithms which controls the amplitude and phase in all four quadrants with good accuracy are written in the VHDL. I/Q modulator works as common actuator for both amplitude and phase correction. Synchronization between RF, LO and ADC clock is indispensable and has been achieved by deriving the clock and LO signal from RF signal itself. Control system has been successfully tested in lab with phase and amplitude stability better then ±1% and ±1° respectively. High frequency RF signal is down converted to IF using the super heterodyne technique. Super heterodyne principal not only brings the RF signal to the Low IF frequency at which it can be easily processed but also enables us to use the same hardware and software for other RF frequencies with some minor modification. (author)

Real time global orbit feedback system for NSLS x-ray ring

International Nuclear Information System (INIS)

Yu, L.H.; Biscardi, R.; Bittner, J.; Fauchet, A.M.; Krinsky, F.S.; Nawrocky, R.J.; Rothman, J.; Singh, O.V.; Yang, K.M.

1991-01-01

We report on the design and commissioning of a real time harmonic global orbit feedback system for the NSLS X-ray ring. This system uses 8 pick-up electrode position monitors and 16 trim dipole magnets to eliminate 3 harmonic components of the orbit fluctuations. Because of the larger number of position monitors and trim magnets, the X-ray ring feedback system differs from the previously reported VUV ring system in that the Fourier analysis and harmonic generation networks are comprised of MDAC boards controlled by computer. The implementation of the global feedback system has resulted in a dramatic improvement of orbit stability, by more than a factor of five everywhere. Simultaneous operation of the global and several local bump feedback systems has been achieved. 4 refs., 5 figs

Effect of vibrotactile feedback on an EMG-based proportional cursor control system.

Science.gov (United States)

Li, Shunchong; Chen, Xingyu; Zhang, Dingguo; Sheng, Xinjun; Zhu, Xiangyang

2013-01-01

Surface electromyography (sEMG) has been introduced into the bio-mechatronics systems, however, most of them are lack of the sensory feedback. In this paper, the effect of vibrotactile feedback for a myoelectric cursor control system is investigated quantitatively. Simultaneous and proportional control signals are extracted from EMG using a muscle synergy model. Different types of feedback including vibrotactile feedback and visual feedback are added, assessed and compared with each other. The results show that vibrotactile feedback is capable of improving the performance of EMG-based human machine interface.

Laser experimental system as teaching aid for demonstrating basic phenomena of laser feedback

International Nuclear Information System (INIS)

Xu, Ling; Zhao, Shijie; Zhang, Shulian

2015-01-01

An experimental laser teaching system is developed to demonstrate laser feedback phenomena, which bring great harm to optical communication and benefits to precision measurement. The system consists of an orthogonally polarized He-Ne laser, a feedback mirror which reflects the laser output light into the laser cavity, and an optical attenuator which changes the intensity of the feedback light. As the feedback mirror is driven by a piezoelectric ceramic, the attenuator is adjusted and the feedback mirror is tilted, the system can demonstrate many basic laser feedback phenomena, including weak, moderate and strong optical feedback, multiple feedback and polarization flipping. Demonstrations of these phenomena can give students a better understanding about the intensity and polarization of lasers. The system is well designed and assembled, simple to operate, and provides a valuable teaching aid at an undergraduate level. (paper)

Increasing Personal Value Congruence in Computerized Decision Support Using System Feedback

Directory of Open Access Journals (Sweden)

Bryan Hosack

2014-02-01

Full Text Available The Theory of Universals in Values (TUV, a reliable and validated conceptualization of personal values used in psychology, is used to examine the effect of system feedback delivered by a Decision Support System (DSS on personal values. The results indicate that value-based decision-making behavior can be influenced by DSS feedback to address value congruence in decision-making. User behavior was shown to follow the outcomes expected by operant theory when feedback was supportive and to follow the outcomes of reactance theory when feedback was challenging. This result suggests that practitioners and Information System (IS researchers should consider user values when designing computerized decision feedback to adjust a system’s design such that the potential user backlash is avoided or congruence between organizational and personal values is achieved.

Digital closed orbit feedback system for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A.J.

1995-01-01

Closed orbit feedback for the Advanced Photon Source (APS) storage ring employs unified global an local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm. application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware, including the DSPS, is distributed in 20 VNE crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories

Lyapunov-based Stability of Feedback Interconnections of Negative Imaginary Systems

KAUST Repository

Ghallab, Ahmed G.

2017-10-19

Feedback control systems using sensors and actuators such as piezoelectric sensors and actuators, micro-electro-mechanical systems (MEMS) sensors and opto-mechanical sensors, are allowing new advances in designing such high precision technologies. The negative imaginary control systems framework allows for robust control design for such high precision systems in the face of uncertainties due to unmodelled dynamics. The stability of the feedback interconnection of negative imaginary systems has been well established in the literature. However, the proofs of stability feedback interconnection which are used in some previous papers have a shortcoming due to a matrix inevitability issue. In this paper, we provide a new and correct Lyapunov-based proof of one such result and show that the result is still true.

Lyapunov-based Stability of Feedback Interconnections of Negative Imaginary Systems

KAUST Repository

Ghallab, Ahmed G.; Mabrok, Mohamed; Petersen, Ian R.

2017-01-01

Feedback control systems using sensors and actuators such as piezoelectric sensors and actuators, micro-electro-mechanical systems (MEMS) sensors and opto-mechanical sensors, are allowing new advances in designing such high precision technologies. The negative imaginary control systems framework allows for robust control design for such high precision systems in the face of uncertainties due to unmodelled dynamics. The stability of the feedback interconnection of negative imaginary systems has been well established in the literature. However, the proofs of stability feedback interconnection which are used in some previous papers have a shortcoming due to a matrix inevitability issue. In this paper, we provide a new and correct Lyapunov-based proof of one such result and show that the result is still true.

A beam position feedback system for beam lines at the photon factory

International Nuclear Information System (INIS)

Katsura, T.; Kamiya, Y.; Haga, K.; Mitsuhashi, T.

1987-01-01

The beam position of the synchrotron radiation produced from the Storage Ring was stabilized by a twofold position feedback system. A digital feedback system was developed to suppress the diurnal beam movement (one cycle of sin-like drifting motion per day) which became a serious problem in low-emittance operation. The feedback was applied to the closed-orbit-distortion (COD) correction system in order to cancel the position variation at all the beam lines proportionately to the variation monitored at one beam line. An analog feedback system is also used to suppress frequency components faster than the slow diurnal movement

The Technology of Measurement Feedback Systems.

Science.gov (United States)

Bickman, Leonard; Kelley, Susan Douglas; Athay, Michele

2012-12-01

Usual care in the community is far from optimal. Sufficient evidence exists that dropout rates are significant, treatment is effective for only a small proportion of clients, and that the translation of evidence-based treatments to the real world is problematic. Technology has been shown to be helpful in health care in improving the effectiveness of treatment. A relatively new technology being used in mental health is measurement feedback systems (MFSs). MFSs are particularly applicable to couple and family psychology (CFP) because of its ability to provide information on the multiple perspectives involved in treatment. The Contextualized Feedback Systems tm (CFS®), developed at Vanderbilt University is used as an example of what can be accomplished with an MFS. The advantages and limitations of this technology are described as well as the anticipated reimbursement requirements that mental health services will need.

Combined feedforward and feedback control of end milling system

OpenAIRE

Čuš, Franc; Župerl, Uroš; Balič, Jože

2012-01-01

Purpose: Purpose of this paper. An intelligent control system is presented that uses a combination of feedforward and feedback for cutting force control in end milling.Design/methodology/approach: The network is trained by the feedback output that is minimized during training and most control action for disturbance rejection is finally performed by the rapid feedforward action of the network.Findings: The feedback controller corrects for errors caused by external disturbances. The feedforward...

Comparison of Power Generating Systems Using Feedback Effect Modeling

International Nuclear Information System (INIS)

Kim, Seong Ho; Kim, Kil Yoo; Kim, Tae Woon

2005-01-01

Comparative assessment of various power systems can be treated as a multicriteria decision-making (MCDM) problem. In reality, there is interdependence among decision elements (e.g., decision goal, decision criteria, and decision alternatives). In our previous work, using an analytic hierarchy process (AHP) technique, a comprehensive assessment framework for national power systems has been developed. It was assumed in the AHP modeling that there is no interdependence among decision elements. In the present work, one of interdependence phenomena, feedback effect, is investigated in the context of network structures instead of one-way directional tree structures. Moreover, attitudes of decision-makers can be incorporated into the feedback effect modeling. The main objectives of this work are to develop a feedback effect modeling using an analytic network process (ANP) technique and to demonstrate the feedback effect using a numerical example in comparison to the hierarchy model

General Output Feedback Stabilization for Fractional Order Systems: An LMI Approach

Directory of Open Access Journals (Sweden)

Yiheng Wei

2014-01-01

Full Text Available This paper is concerned with the problem of general output feedback stabilization for fractional order linear time-invariant (FO-LTI systems with the fractional commensurate order 0<α<2. The objective is to design suitable output feedback controllers that guarantee the stability of the resulting closed-loop systems. Based on the slack variable method and our previous stability criteria, some new results in the form of linear matrix inequality (LMI are developed to the static and dynamic output feedback controllers synthesis for the FO-LTI system with 0<α<1. Furthermore, the results are extended to stabilize the FO-LTI systems with 1≤α<2. Finally, robust output feedback control is discussed. Numerical examples are given to illustrate the effectiveness of the proposed design methods.

Impact of biogenic emissions on feedbacks in the climate system

Science.gov (United States)

Krüger, Olaf

2017-04-01

Impact of biogenic emissions on feedbacks in the climate system Bio-geophysical feedback between marine or continental ecosystems and the atmosphere potentially can alter climate change. A prominent feedback loop which is under discussion since 1983 bases on the emission of biologically produced gases - molecular oxygen, sulphur containing compounds and possibly isoprene, supersaturated in oceanic waters - into the marine troposphere. These by-products of phytoplankton metabolism lead to aerosol production and procure sustained influence on climate via modulation of cloud optical properties. In this contribution some findings related to the above mentioned climate processes are presented with special emphasis on marine ecosystems. A comparison of marine and continental ecosystems is made and different processes with major impact on feedbacks in the climate system are discussed.

Good to great: using 360-degree feedback to improve physician emotional intelligence.

Science.gov (United States)

Hammerly, Milton E; Harmon, Larry; Schwaitzberg, Steven D

2014-01-01

The past decade has seen intense interest and dramatic change in how hospitals and physician organizations review physician behaviors. The characteristics of successful physicians extend past their technical and cognitive skills. Two of the six core clinical competencies (professionalism and interpersonal/communication skills) endorsed by the Accreditation Council for Graduate Medical Education, the American Board of Medical Specialties, and The Joint Commission require physicians to succeed in measures associated with emotional intelligence (EI). Using 360-degree anonymous feedback surveys to screen for improvement opportunities in these two core competencies enables organizations to selectively offer education to further develop physician EI. Incorporating routine use of these tools and interventions into ongoing professional practice evaluation and focused professional practice evaluation processes may be a cost-effective strategy for preventing disruptive behaviors and increasing the likelihood of success when transitioning to an employed practice model. On the basis of a literature review, we determined that physician EI plays a key role in leadership; teamwork; and clinical, financial, and organizational outcomes. This finding has significant implications for healthcare executives seeking to enhance physician alignment and transition to a team-based delivery model.

Controlling chaotic systems via nonlinear feedback control

International Nuclear Information System (INIS)

Park, Ju H.

2005-01-01

In this article, a new method to control chaotic systems is proposed. Using Lyapunov method, we design a nonlinear feedback controller to make the controlled system be stabilized. A numerical example is given to illuminate the design procedure and advantage of the result derived

Next Generation Environmentally-Friendly Driving Feedback Systems Research and Development

Energy Technology Data Exchange (ETDEWEB)

Barth, Matthew [Regents Of The University Of California, Riverside, CA (United States); Boriboonsomsin, Kanok [Regents Of The University Of California, Riverside, CA (United States)

2014-12-31

The objective of this project is to design, develop, and demonstrate a next-generation, federal safety- and emission-complaint driving feedback system that can be deployed across the existing vehicle fleet and improve fleet average fuel efficiency by at least 2%. The project objective was achieved with the driving feedback system that encourages fuel-efficient vehicle travel and operation through: 1) Eco-Routing Navigation module that suggests the most fuel-efficient route from one stop to the next, 2) Eco-Driving Feedback module that provides sensible information, recommendation, and warning regarding fuel-efficient vehicle operation, and 3) Eco-Score and Eco-Rank module that provides a means for driving performance tracking, self-evaluation, and peer comparison. The system also collects and stores vehicle travel and operation data, which are used by Algorithm Updating module to customize the other modules for specific vehicles and adapts them to specific drivers over time. The driving feedback system was designed and developed as an aftermarket technology that can be retrofitted to vehicles in the existing fleet. It consists of a mobile application for smart devices running Android operating system, a vehicle on-board diagnostics connector, and a data server. While the system receives and utilizes real-time vehicle and engine data from the vehicle’s controller area network bus through the vehicle’s on-board diagnostic connector, it does not modify or interfere with the vehicle’s controller area network bus, and thus, is in compliance with federal safety and emission regulations. The driving feedback system was demonstrated and then installed on 45 vehicles from three different fleets for field operational test. These include 15 private vehicles of the general public, 15 pickup trucks of the California Department of Transportation that are assigned to individual employees for business use, and 15 shuttle buses of the Riverside Transit Agency that are used

Feedback systems in the SLC

International Nuclear Information System (INIS)

Thompson, K.A.; Jobe, R.K.; Johnson, R.; Phinney, N.

1987-02-01

Two classes of computer-controlled feedback have been implemented to stabilize parameters in subsystems of the SLC: (1) ''slow'' (time scales ∼ minutes) feedback, and (2) ''fast'', i.e., pulse-to-pulse, feedback. The slow loops run in a single FEEDBACK process in the SLC host VAX, which acquires signals and sets control parameters via communication with the database and the network of normal SLC microprocessors. Slow loops exist to stabilize beam energy and energy spread, beam position and angle, and timing of kicker magnets, and to compensate for changes in the phase length of the rf drive line. The fast loops run in dedicated microprocessors, and may sample and/or feedback on particular parameters as often as every pulse of the SLC beam. The first implementations of fast feedback are to control transverse beam blow-up and to stabilize the energy and energy spread of bunches going into the SLC arcs. The overall architecture of the feedback software and the operator interface for controlling loops are discussed

Improving the security of optoelectronic delayed feedback system by parameter modulation and system coupling

Science.gov (United States)

Liu, Lingfeng; Miao, Suoxia; Cheng, Mengfan; Gao, Xiaojing

2016-02-01

A coupled system with varying parameters is proposed to improve the security of optoelectronic delayed feedback system. This system is coupled by two parameter-varied optoelectronic delayed feedback systems with chaotic modulation. Dynamics performance results show that this system has a higher complexity compared to the original one. Furthermore, this system can conceal the time delay effectively against the autocorrelation function and delayed mutual information method and can increase the dimension space of secure parameters to resist brute-force attack by introducing the digital chaotic systems.

Digital closed orbit feedback system for the advanced photon source storage ring

International Nuclear Information System (INIS)

Chung, Y.; Barr, D.; Decker, G.

1995-01-01

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described in this paper. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm, application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware including the DSPs is distributed in 20 VME crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories

Wideband feedback system prototype validation

CERN Document Server

Li, K; Bjorsvik, E; Fox, J; Hofle, W; Kotzian, G; Rivetta, C; Salvant, B; Turgut, O

2017-01-01

A wideband feedback demonstrator system has been de-veloped in collaboration with US-LARP under the joint lead-ership of CERN and SLAC. The system includes widebandkicker structures and amplifiers along with a fast digital re-configurable system up to 4 GS/s for single bunch and multibunch control. Most of the components have been installedin recent years and have been put into operation to test bothintra-bunch damping and individual bunch control in a multibunch train. In this note we report on the MD program,procedure and key findings that were made with this systemin the past year.

Feedback control and beam diagnostic algorithms for a multiprocessor DSP system

International Nuclear Information System (INIS)

Teytelman, D.; Claus, R.; Fox, J.; Hindi, H.; Linscott, I.; Prabhakar, S.

1996-09-01

The multibunch longitudinal feedback system developed for use by PEP-II, ALS and DAΦNE uses a parallel array of digital signal processors to calculate the feedback signals from measurements of beam motion. The system is designed with general-purpose programmable elements which allow many feedback operating modes as well as system diagnostics, calibrations and accelerator measurements. The overall signal processing architecture of the system is illustrated. The real-time DSP algorithms and off-line postprocessing tools are presented. The problems in managing 320 K samples of data collected in one beam transient measurement are discussed and the solutions are presented. Example software structures are presented showing the beam feedback process, techniques for modal analysis of beam motion(used to quantify growth and damping rates of instabilities) and diagnostic functions (such as timing adjustment of beam pick-up and kicker components). These operating techniques are illustrated with example results obtained from the system installed at the Advanced Light Source at LBL

Force Feedback Control Method of Active Tuned Mass Damper

Directory of Open Access Journals (Sweden)

Xiuli Wang

2017-01-01

Full Text Available Active tuned mass dampers as vibration-control devices are widely used in many fields for their good stability and effectiveness. To improve the performance of such dampers, a control method based on force feedback is proposed. The method offers several advantages such as high-precision control and low-performance requirements for the actuator, as well as not needing additional compensators. The force feedback control strategy was designed based on direct-velocity feedback. The effectiveness of the method was verified in a single-degree-of-freedom system, and factors such as damping effect, required active force, actuator stroke, and power consumption of the damper were analyzed. Finally, a simulation study was performed by configuring a main complex elastic-vibration-damping system. The results show that the method provides effective control over modal resonances of multiple orders of the system and improves its dynamics performance.

360 Derece Performans Değerlendirme ve Geri Bildirim: Bir Üniversite Mediko-Sosyal Merkezi Birim Amirlerinin Yönetsel Yetkinliklerinin Değerlendirilmesi Üzerine Pilot Uygulama Örneği(360 Degree Performance Appraisal And Feedback: “A Pilot Study Illustration in Appraising the Managerial Skills of Supervisors Working in Health Care Centre of a University”

Directory of Open Access Journals (Sweden)

Selin Metin CAMGÖZ

2006-01-01

Full Text Available In this study, “360 Degree Performance Appraisal” which is one of the most current and controversial issues of human resource practices is extensively examined and supported with an empirical research. The study contains 2 parts. After explaining the necessity and the general utilities of the classical performance appraisal system, the first theoretical part shifts to the emergence of 360 degree performance appraisal, discusses its distinctive benefits over the classical appraisal system and focuses its attention to the raters (superiors, subordinates, peers, self involving in the 360 degree performance appraisal.The second empirical part illustrates the development of 360 degree performance appraisal system as well as its application and sample feedback reports for feedback purposes in order to appraise the managerial skills of supervisors working in Health Care Centre of a public university.

Design and evaluation of a Flight Envelope Protection haptic feedback system

NARCIS (Netherlands)

Ellerbroek, J.; Rodriguez Martin, M.J.M.; Lombaerts, T; van Paassen, M.M.; Mulder, M.

2016-01-01

This paper describes the design and evaluation of a shared control, haptic feedback system to communicate Flight Envelope Protection System intent. The concept uses a combination of stiffness feedback and vibration to communicate proximity of the aircraft state to flight envelope boundaries. In

Introducing a feedback training system for guided home rehabilitation

Directory of Open Access Journals (Sweden)

Disselhorst-Klug Catherine

2010-01-01

Full Text Available Abstract As the number of people requiring orthopaedic intervention is growing, individualized physiotherapeutic rehabilitation and adequate postoperative care becomes increasingly relevant. The chances of improvement in the patients condition is directly related to the performance and consistency of the physiotherapeutic exercises. In this paper a smart, cost-effective and easy to use Feedback Training System for home rehabilitation based on standard resistive elements is introduced. This ensures high accuracy of the exercises performed and offers guidance and control to the patient by offering direct feedback about the performance of the movements. 46 patients were recruited and performed standard physiotherapeutic training to evaluate the system. The results show a significant increase in the patient's ability to reproduce even simple physiotherapeutic exercises when being supported by the Feedback Training System. Thus physiotherapeutic training can be extended into the home environment whilst ensuring a high quality of training.

Introducing a feedback training system for guided home rehabilitation.

Science.gov (United States)

Kohler, Fabian; Schmitz-Rode, Thomas; Disselhorst-Klug, Catherine

2010-01-15

As the number of people requiring orthopaedic intervention is growing, individualized physiotherapeutic rehabilitation and adequate postoperative care becomes increasingly relevant. The chances of improvement in the patients condition is directly related to the performance and consistency of the physiotherapeutic exercises.In this paper a smart, cost-effective and easy to use Feedback Training System for home rehabilitation based on standard resistive elements is introduced. This ensures high accuracy of the exercises performed and offers guidance and control to the patient by offering direct feedback about the performance of the movements.46 patients were recruited and performed standard physiotherapeutic training to evaluate the system. The results show a significant increase in the patient's ability to reproduce even simple physiotherapeutic exercises when being supported by the Feedback Training System. Thus physiotherapeutic training can be extended into the home environment whilst ensuring a high quality of training.

Instruction, Feedback and Biometrics: The User Interface for Fingerprint Authentication Systems

Science.gov (United States)

Riley, Chris; Johnson, Graham; McCracken, Heather; Al-Saffar, Ahmed

Biometric authentication is the process of establishing an individual’s identity through measurable characteristics of their behaviour, anatomy or physiology. Biometric technologies, such as fingerprint systems, are increasingly being used in a diverse range of contexts from immigration control, to banking and personal computing. As is often the case with emerging technologies, the usability aspects of system design have received less attention than technical aspects. Fingerprint systems pose a number of challenges for users and past research has identified issues with correct finger placement, system feedback and instruction. This paper describes the development of an interface for fingerprint systems using an iterative, participative design approach. During this process, several different methods for the presentation of instruction and feedback were identified. The different types of instruction and feedback were tested in a study involving 82 participants. The results showed that feedback had a statistically significant effect on overall system performance, but instruction did not. The design recommendations emerging from this study, and the use of participatory design in this context, are discussed.

Feedback control and adaptive control of the energy resource chaotic system

International Nuclear Information System (INIS)

Sun Mei; Tian Lixin; Jiang Shumin; Xu Jun

2007-01-01

In this paper, the problem of control for the energy resource chaotic system is considered. Two different method of control, feedback control (include linear feedback control, non-autonomous feedback control) and adaptive control methods are used to suppress chaos to unstable equilibrium or unstable periodic orbits. The Routh-Hurwitz criteria and Lyapunov direct method are used to study the conditions of the asymptotic stability of the steady states of the controlled system. The designed adaptive controller is robust with respect to certain class of disturbances in the energy resource chaotic system. Numerical simulations are presented to show these results

Persistent disturbance rejection via state feedback for networked control systems

Energy Technology Data Exchange (ETDEWEB)

Yue Dong [Institute of Information and Control Engineering Technology, Nanjing Normal University, 78 Bancang Street, Nanjing, Jiangsu 210042 (China)], E-mail: medongy@njnu.edu.cn; Lam, James [Department of Mechanical Engineering, University of Hong Kong, Pokfulam Road (Hong Kong); Wang Zidong [Department of Information Systems and Computing, Brunel University, Uxbridge, Middlesex UB8 3PH (United Kingdom)], E-mail: Zidong.Wang@brunel.ac.uk

2009-04-15

The problem of persistent disturbance rejection via state feedback for networked control systems is concerned based on the Lyapunov function method. The effect of the network conditions, such as network-induced delay and data dropout, is considered in the modeling of the system. It is assumed that the state and the control signals are individually quantized by quantizers on the sensor side and the controller side. The feedback gain and the quantizer parameters that guarantee the internal stability and the disturbance rejection performance of the closed-loop system are obtained by solving some linear matrix inequalities. To illustrate the effectiveness of the proposed method, a numerical example is provided for the design of the feedback gain and the quantizer parameters.

Survey of Digital Feedback Systems in High Current Storage Rings

International Nuclear Information System (INIS)

Teytelman, Dmitry

2003-01-01

In the last decade demand for brightness in synchrotron light sources and luminosity in circular colliders led to construction of multiple high current storage rings. Many of these new machines require feedback systems to achieve design stored beam currents. In the same time frame the rapid advances in the technology of digital signal processing allowed the implementation of these complex feedback systems. In this paper I concentrate on three applications of feedback to storage rings: orbit control in light sources, coupled-bunch instability control, and low-level RF control. Each of these applications is challenging in areas of processing bandwidth, algorithm complexity, and control of time-varying beam and system dynamics. I will review existing implementations as well as comment on promising future directions

Persistent disturbance rejection via state feedback for networked control systems

International Nuclear Information System (INIS)

Yue Dong; Lam, James; Wang Zidong

2009-01-01

The problem of persistent disturbance rejection via state feedback for networked control systems is concerned based on the Lyapunov function method. The effect of the network conditions, such as network-induced delay and data dropout, is considered in the modeling of the system. It is assumed that the state and the control signals are individually quantized by quantizers on the sensor side and the controller side. The feedback gain and the quantizer parameters that guarantee the internal stability and the disturbance rejection performance of the closed-loop system are obtained by solving some linear matrix inequalities. To illustrate the effectiveness of the proposed method, a numerical example is provided for the design of the feedback gain and the quantizer parameters.

Operation and performance of a longitudinal feedback system using digital signal processing

International Nuclear Information System (INIS)

Teytelman, D.; Fox, J.; Hindi, H.

1994-01-01

A programmable longitudinal feedback system using a parallel array of AT ampersand T 1610 digital signal processors has been developed as a component of the PEP-II R ampersand D program. This system has been installed at the Advanced Light Source (LBL) and implements full speed bunch by bunch signal processing for storage rings with bunch spacing of 4ns. Open and closed loop results showing the action of the feedback system are presented, and the system is shown to damp coupled-bunch instabilities in the ALS. A unified PC-based software environment for the feedback system operation is also described

Tutorial on beam-based feedback systems for linacs

International Nuclear Information System (INIS)

Hendrickson, L.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Ross, M.; Sass, R.; Shoaee, H.

1994-08-01

A generalized fast feedback system stabilizes beams in the SLC. It performs measurements and modifies actuator settings to control beam states such as position, angle, energy and intensity on a pulse to pulse basis. An adaptive cascade feature allows communication between a series of linac loops, avoiding overcorrection problems. The system is based on the state space formalism of digital control theory. Due to the database-driven design, new loops are added without requiring software modifications. Recent enhancements support the monitoring and control of nonlinear states such as beam phase using excitation techniques. In over three years of operation, the feedback system has grown from its original eight loops to more than fifty loops, and it has been invaluable in stabilizing the machine

Analysis, Design, and Evaluation of Acoustic Feedback Cancellation Systems for Hearing Aids

DEFF Research Database (Denmark)

Guo, Meng

2013-01-01

Acoustic feedback problems occur when the output loudspeaker signal of an audio system is partly returned to the input microphone via an acoustic coupling through the air. This problem often causes significant performance degradations in applications such as public address systems and hearing aids....... In the worst case, the audio system becomes unstable and howling occurs. In this work, first we analyze a general multiple microphone audio processing system, where a cancellation system using adaptive filters is used to cancel the effect of acoustic feedback. We introduce and derive an accurate approximation...... in acoustic feedback cancellation for hearing aids. It utilizes a probe noise signal which is generated with a specific characteristic so that it can facilitate an unbiased adaptive filter estimation with fast tracking of feedback path variations/changes despite its low signal level. We show in a hearing aid...

Theoretical and experimental study of Chen chaotic system with notch filter feedback control

International Nuclear Information System (INIS)

Ming, Zhang Xiao; Jian-Hua, Peng; Ju-Fang, Chen

2010-01-01

Since the past two decades, the time delay feedback control method has attracted more and more attention in chaos control studies because of its simplicity and efficiency compared with other chaos control schemes. Recently, it has been proposed to suppress low-dimensional chaos with the notch filter feedback control method, which can be implemented in a laser system. In this work, we have analytically determined the controllable conditions for notch filter feedback controlling of Chen chaotic system in terms of the Hopf bifurcation theory. The conditions for notch filter feedback controlled Chen chaoitc system having a stable limit cycle solution are given. Meanwhile, we also analysed the Hopf bifurcation direction, which is very important for parameter settings in notch filter feedback control applications. Finally, we apply the notch filter feedback control methods to the electronic circuit experiments and numerical simulations based on the theoretical analysis. The controlling results of notch filter feedback control method well prove the feasibility and reliability of the theoretical analysis. (general)

On a new time-delayed feedback control of chaotic systems

International Nuclear Information System (INIS)

Tian Lixin; Xu Jun; Sun Mei; Li Xiuming

2009-01-01

In this paper, using the idea of the successive dislocation feedback method, a new time-delayed feedback control method called the successive dislocation time-delayed feedback control (SDTDFC) is designed. Firstly, the idea of SDTDFC is introduced. Then some analytic sufficient conditions of the chaos control from the SDTDFC approach are derived for stabilization. Finally, some established results are further clarified via a case study of the Lorenz system with the numerical simulations.

Continuing Robot Skill Learning after Demonstration with Human Feedback

Directory of Open Access Journals (Sweden)

Argall Brenna D.

2011-12-01

Full Text Available Though demonstration-based approaches have been successfully applied to learning a variety of robot behaviors, there do exist some limitations. The ability to continue learning after demonstration, based on execution experience with the learned policy, therefore has proven to be an asset to many demonstration-based learning systems. This paper discusses important considerations for interfaces that provide feedback to adapt and improve demonstrated behaviors. Feedback interfaces developed for two robots with very different motion capabilities - a wheeled mobile robot and high degree-of-freedom humanoid - are highlighted.

Design of EAST LHCD high power supply feedback control system based on PLC

International Nuclear Information System (INIS)

Hu Huaichuan; Shan Jiafang

2009-01-01

Design of EAST LHCD -35kV/5.6MW high power supply feedback control system based on PLC is described. Industrial computer and PLC are used to control high power supply in the system. PID arithmetic is adopted to achieve the feedback control of voltage of high power supply. Operating system is base on real-time operating system of QNX. Good controlling properties and reliable protective properties of the feedback control system are proved by the experiment results. (authors)

Effect of biased feedback on motor imagery learning in BCI-teleoperation system

Directory of Open Access Journals (Sweden)

Maryam eAlimardani

2014-04-01

Full Text Available Feedback design is an important issue in motor imagery BCI systems. Regardless, to date it has not been reported how feedback presentation can optimize co-adaptation between a human brain and such systems. This paper assesses the effect of realistic visual feedback on users’ BC performance and motor imagery skills. We previously developed a tele-operation system for a pair of humanlike robotic hands and showed that BCI control of such hands along with first-person perspective visual feedback of movements can arouse a sense of embodiment in the operators. In the first stage of this study, we found that the intensity of this ownership illusion was associated with feedback presentation and subjects’ performance during BCI motion control. In the second stage, we probed the effect of positive and negative feedback bias on subjects’ BCI performance and motor imagery skills. Although the subject specific classifier, which was set up at the beginning of experiment, detected no significant change in the subjects’ online performance, evaluation of brain activity patterns revealed that subjects’ self-regulation of motor imagery features improved due to a positive bias of feedback and a possible occurrence of ownership illusion. Our findings suggest that in general training protocols for BCIs, manipulation of feedback can play an important role in the optimization of subjects’ motor imagery skills.

Fast digital transverse feedback system for bunch train operation in CESR

International Nuclear Information System (INIS)

Rogers, J.T.; Billing, M.G.; Dobbins, J.A.

1996-01-01

We have developed a time domain transverse feedback system with the high bandwidth needed to control transverse instabilities when the CESR e + e - collider is filled with trains of closely spaced bunches. This system is based on parallel digital processors and a stripline driver. It is capable of acting on arbitrary patterns of bunches having a minimum spacing of 14 ns. Several simplifying features have been introduced. A single shorted stripline kicker driven by one power amplifier is used to control both counter-rotating beams. The desired feedback phase is achieved by sampling the bunch position at a single location on two independently selectable beam revolutions. The system adapts to changes in the betatron tune, bunch pattern, or desired damping rate through the loading of new parameters into the digital processors via the CESR control system. The feedback system also functions as a fast gated bunch current monitor. Both vertical and horizontal loops are now used in CESR operation. The measured betatron damping rates with the transverse feedback system in operation are in agreement with the analytical prediction and a computer simulation developed in connection with this work. (author)

Fast digital transverse feedback system for bunch train operation in CESR

Energy Technology Data Exchange (ETDEWEB)

Rogers, J T; Billing, M G; Dobbins, J A [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies; and others

1996-08-01

We have developed a time domain transverse feedback system with the high bandwidth needed to control transverse instabilities when the CESR e{sup +}e{sup -} collider is filled with trains of closely spaced bunches. This system is based on parallel digital processors and a stripline driver. It is capable of acting on arbitrary patterns of bunches having a minimum spacing of 14 ns. Several simplifying features have been introduced. A single shorted stripline kicker driven by one power amplifier is used to control both counter-rotating beams. The desired feedback phase is achieved by sampling the bunch position at a single location on two independently selectable beam revolutions. The system adapts to changes in the betatron tune, bunch pattern, or desired damping rate through the loading of new parameters into the digital processors via the CESR control system. The feedback system also functions as a fast gated bunch current monitor. Both vertical and horizontal loops are now used in CESR operation. The measured betatron damping rates with the transverse feedback system in operation are in agreement with the analytical prediction and a computer simulation developed in connection with this work. (author)

The effects of driver identity on driving safety in a retrospective feedback system.

Science.gov (United States)

Zhao, Guozhen; Wu, Changxu

2012-03-01

Retrospective feedback that provides detailed information on a driver's performance in critical driving situations at the end of a trip enhances his/her driving behaviors and safe driving habits. Although this has been demonstrated by a previous study, retrospective feedback can be further improved and applied to non-critical driving situations, which is needed for transportation safety. To propose a new retrospective feedback system that uses driver identity (i.e., a driver's name) and to experimentally study its effects on measures of driving performance and safety in a driving simulator. We conducted a behavioral experimental study with 30 participants. "Feedback type" was a between-subject variable with three conditions: no feedback (control group), feedback without driver identity, and feedback with driver identity. We measured multiple aspects of participants' driving behavior. To control for potential confounds, factors that were significantly correlated with driving behavior (e.g., age and driving experience) were all entered as covariates into a multivariate analysis of variance. To examine the effects of speeding on collision severity in driving simulation studies, we also developed a new index - momentum of potential collision - with a set of equations. Subjects who used a feedback system with driver identity had the fewest speeding violations and central-line crossings, spent the least amount of time speeding and crossing the central line, had the lowest speeding and central-line crossing magnitude, ran the fewest red lights, and had the smallest momentum of potential collision compared to the groups with feedback without driver identity and without feedback (control group). The new retrospective feedback system with driver identity has the potential to enhance a person's driving safety (e.g., speeding, central-line crossing, momentum of potential collision), which is an indication of the valence of one's name in a feedback system design. Copyright �

[Real-time feedback systems for improvement of resuscitation quality].

Science.gov (United States)

Lukas, R P; Van Aken, H; Engel, P; Bohn, A

2011-07-01

The quality of chest compression is a determinant of survival after cardiac arrest. Therefore, the European Resuscitation Council (ERC) 2010 guidelines on resuscitation strongly focus on compression quality. Despite its impact on survival, observational studies have shown that chest compression quality is not reached by professional rescue teams. Real-time feedback devices for resuscitation are able to measure chest compression during an ongoing resuscitation attempt through a sternal sensor equipped with a motion and pressure detection system. In addition to the electrocardiograph (ECG) ventilation can be detected by transthoracic impedance monitoring. In cases of quality deviation, such as shallow chest compression depth or hyperventilation, feedback systems produce visual or acoustic alarms. Rescuers can thereby be supported and guided to the requested quality in chest compression and ventilation. Feedback technology is currently available both as a so-called stand-alone device and as an integrated feature in a monitor/defibrillator unit. Multiple studies have demonstrated sustainable enhancement in the education of resuscitation due to the use of real-time feedback technology. There is evidence that real-time feedback for resuscitation combined with training and debriefing strategies can improve both resuscitation quality and patient survival. Chest compression quality is an independent predictor for survival in resuscitation and should therefore be measured and documented in further clinical multicenter trials.

Push-Pull and Feedback Mechanisms Can Align Signaling System Outputs with Inputs.

Science.gov (United States)

Andrews, Steven S; Peria, William J; Yu, Richard C; Colman-Lerner, Alejandro; Brent, Roger

2016-11-23

Many cell signaling systems, including the yeast pheromone response system, exhibit "dose-response alignment" (DoRA), in which output of one or more downstream steps closely matches the fraction of occupied receptors. DoRA can improve the fidelity of transmitted dose information. Here, we searched systematically for biochemical network topologies that produced DoRA. Most networks, including many containing feedback and feedforward loops, could not produce DoRA. However, networks including "push-pull" mechanisms, in which the active form of a signaling species stimulates downstream activity and the nominally inactive form reduces downstream activity, enabled perfect DoRA. Networks containing feedbacks enabled DoRA, but only if they also compared feedback to input and adjusted output to match. Our results establish push-pull as a non-feedback mechanism to align output with variable input and maximize information transfer in signaling systems. They also suggest genetic approaches to determine whether particular signaling systems use feedback or push-pull control. Copyright © 2016 Elsevier Inc. All rights reserved.

H∞ synchronization of chaotic systems via dynamic feedback approach

International Nuclear Information System (INIS)

Lee, S.M.; Ji, D.H.; Park, Ju H.; Won, S.C.

2008-01-01

This Letter considers H ∞ synchronization of a general class of chaotic systems with external disturbance. Based on Lyapunov theory and linear matrix inequality (LMI) formulation, the novel feedback controller is established to not only guarantee stable synchronization of both master and slave systems but also reduce the effect of external disturbance to an H ∞ norm constraint. A dynamic feedback control scheme is proposed for H ∞ synchronization in chaotic systems for the first time. Then, a criterion for existence of the controller is given in terms of LMIs. Finally, a numerical simulation is presented to show the effectiveness of the proposed chaos synchronization scheme

Feedback Design Patterns for Math Online Learning Systems

Science.gov (United States)

Inventado, Paul Salvador; Scupelli, Peter; Heffernan, Cristina; Heffernan, Neil

2017-01-01

Increasingly, computer-based learning systems are used by educators to facilitate learning. Evaluations of several math learning systems show that they result in significant student learning improvements. Feedback provision is one of the key features in math learning systems that contribute to its success. We have recently been uncovering feedback…

Optimal control of nonlinear continuous-time systems in strict-feedback form.

Science.gov (United States)

Zargarzadeh, Hassan; Dierks, Travis; Jagannathan, Sarangapani

2015-10-01

This paper proposes a novel optimal tracking control scheme for nonlinear continuous-time systems in strict-feedback form with uncertain dynamics. The optimal tracking problem is transformed into an equivalent optimal regulation problem through a feedforward adaptive control input that is generated by modifying the standard backstepping technique. Subsequently, a neural network-based optimal control scheme is introduced to estimate the cost, or value function, over an infinite horizon for the resulting nonlinear continuous-time systems in affine form when the internal dynamics are unknown. The estimated cost function is then used to obtain the optimal feedback control input; therefore, the overall optimal control input for the nonlinear continuous-time system in strict-feedback form includes the feedforward plus the optimal feedback terms. It is shown that the estimated cost function minimizes the Hamilton-Jacobi-Bellman estimation error in a forward-in-time manner without using any value or policy iterations. Finally, optimal output feedback control is introduced through the design of a suitable observer. Lyapunov theory is utilized to show the overall stability of the proposed schemes without requiring an initial admissible controller. Simulation examples are provided to validate the theoretical results.

Formant compensation for auditory feedback with English vowels

DEFF Research Database (Denmark)

Mitsuya, Takashi; MacDonald, Ewen N; Munhall, Kevin G

2015-01-01

Past studies have shown that speakers spontaneously adjust their speech acoustics in response to their auditory feedback perturbed in real time. In the case of formant perturbation, the majority of studies have examined speaker's compensatory production using the English vowel /ɛ/ as in the word...... "head." Consistent behavioral observations have been reported, and there is lively discussion as to how the production system integrates auditory versus somatosensory feedback to control vowel production. However, different vowels have different oral sensation and proprioceptive information due...... to differences in the degree of lingual contact or jaw openness. This may in turn influence the ways in which speakers compensate for auditory feedback. The aim of the current study was to examine speakers' compensatory behavior with six English monophthongs. Specifically, the current study tested to see...

Modeling mutual feedback between users and recommender systems

Science.gov (United States)

Zeng, An; Yeung, Chi Ho; Medo, Matúš; Zhang, Yi-Cheng

2015-07-01

Recommender systems daily influence our decisions on the Internet. While considerable attention has been given to issues such as recommendation accuracy and user privacy, the long-term mutual feedback between a recommender system and the decisions of its users has been neglected so far. We propose here a model of network evolution which allows us to study the complex dynamics induced by this feedback, including the hysteresis effect which is typical for systems with non-linear dynamics. Despite the popular belief that recommendation helps users to discover new things, we find that the long-term use of recommendation can contribute to the rise of extremely popular items and thus ultimately narrow the user choice. These results are supported by measurements of the time evolution of item popularity inequality in real systems. We show that this adverse effect of recommendation can be tamed by sacrificing part of short-term recommendation accuracy.

Effects of realistic force feedback in a robotic assisted minimally invasive surgery system.

Science.gov (United States)

Moradi Dalvand, Mohsen; Shirinzadeh, Bijan; Nahavandi, Saeid; Smith, Julian

2014-06-01

Robotic assisted minimally invasive surgery systems not only have the advantages of traditional laparoscopic procedures but also restore the surgeon's hand-eye coordination and improve the surgeon's precision by filtering hand tremors. Unfortunately, these benefits have come at the expense of the surgeon's ability to feel. Several research efforts have already attempted to restore this feature and study the effects of force feedback in robotic systems. The proposed methods and studies have some shortcomings. The main focus of this research is to overcome some of these limitations and to study the effects of force feedback in palpation in a more realistic fashion. A parallel robot assisted minimally invasive surgery system (PRAMiSS) with force feedback capabilities was employed to study the effects of realistic force feedback in palpation of artificial tissue samples. PRAMiSS is capable of actually measuring the tip/tissue interaction forces directly from the surgery site. Four sets of experiments using only vision feedback, only force feedback, simultaneous force and vision feedback and direct manipulation were conducted to evaluate the role of sensory feedback from sideways tip/tissue interaction forces with a scale factor of 100% in characterising tissues of varying stiffness. Twenty human subjects were involved in the experiments for at least 1440 trials. Friedman and Wilcoxon signed-rank tests were employed to statistically analyse the experimental results. Providing realistic force feedback in robotic assisted surgery systems improves the quality of tissue characterization procedures. Force feedback capability also increases the certainty of characterizing soft tissues compared with direct palpation using the lateral sides of index fingers. The force feedback capability can improve the quality of palpation and characterization of soft tissues of varying stiffness by restoring sense of touch in robotic assisted minimally invasive surgery operations.

COMMISSIONING OF THE DIGITAL TRANSVERSE BUNCH-BY-BUNCH FEEDBACK SYSTEM FOR THE TLS

International Nuclear Information System (INIS)

HU, K.H.; KUO, C.H.; CHOU, P.J.; LEE, D.; HSU, S.Y.; CHEN, J.; WANG, C.J.; HSU, K.T.; KOBAYASHI, K.; NAKAMURA, T.; CHAO, A.W.; WENG, W.T.

2006-01-01

Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even beam loss. Feedback systems are used to suppress multi-bunch instabilities associated with the resistive wall of the beam ducts, cavity-like structures, and trapped ions. A new digital transverse bunch-by-bunch feedback system has recently been commissioned at the Taiwan Light Source, and has replaced the previous analog system. The new system has the advantages that it enlarges the tune acceptance and improves damping for transverse instability at high currents, such that top-up operation is achieved. After a coupled-bunch transverse instability was suppressed, more than 350 mA was successfully stored during preliminary commissioning. In this new system, a single feedback loop simultaneously suppresses both horizontal and vertical multi-bunch instabilities. Investigating the characteristics of the feedback loop and further improving the system performances are the next short-term goals. The feedback system employs the latest generation of field-programmable gate array (FPGA) processor to process bunch signals. Memory has been installed to capture up to 250 msec of bunch oscillation signal, considering system diagnostics suitable to support various beam physics studies

Design of the ILC Prototype FONT4 Digital Intra-Train Beam-Based Feedback System

International Nuclear Information System (INIS)

Burrows, P.; Queen Mary, U. of London; Christian, G.B.; Hartin, A.F.; Dabiri Khah, H.; White, G.R.; Oxford U.; Clarke, C.C.; Perry, C.; Oxford Instruments; Kalinin, A.; Daresbury; McCormick, D.J.; Molloy, S.; Ross, M.C.; SLAC

2007-01-01

We present the design of the FONT4 digital intra-train beam position feedback system prototype and preliminary results of initial beam tests at the Accelerator Test Facility (ATF) at KEK. The feedback system incorporates a fast analogue beam position monitor (BPM) front-end signal processor, a digital feedback board, and a kicker driver amplifier. The short bunchtrain, comprising 3 electron bunches separated by c. 150ns, in the ATF extraction line was used to test components of the prototype feedback system

Commissioning of FPGA-based Transverse and Longitudinal Bunch-by-Bunch Feedback System for the TLS

International Nuclear Information System (INIS)

Hu, K. H.; Kuo, C. H.; Lau, W. K.; Yeh, M. S.; Hsu, S. Y.; Chou, P. J.; Wang, M. H.; Lee, Demi; Chen, Jenny; Wang, C. J.; Hsu, K. T.; Kobayashi, K.; Nakamura, T.; Dehler, M.

2006-01-01

Multi-bunch instabilities deteriorate beam quality, increasing beam emittance, or even causing beam loss in the synchrotron light source. The feedback system is essential to suppress multi-bunch instabilities caused by the impedances of beam ducts, and trapped ions. A new FPGA based transverse and longitudinal bunch-by-bunch feedback system have been commissioned at the Taiwan Light Source recently, A single feedback loop is used to simultaneously suppress the horizontal and the vertical multi-bunch instabilities. Longitudinal instabilities caused by cavity-like structures are suppressed by the longitudinal feedback loop. The same FPGA processor is employed in the transverse feedback and the longitudinal feedback system respectively. Diagnostic memory is included in the system to capture the bunch oscillation signal, which supports various studies

A multipoint feedback control system for scanned focussed ultrasound hyperthermia

International Nuclear Information System (INIS)

Johnson, C.; Kress, R.; Roemer, R.; Hynynen, K.

1987-01-01

A multipoint feedback control system has been developed and tested for use with a scanned focussed ultrasound hyperthermia system. Extensive in-vivo tests (using a perfused organ model) have been made to evaluate the basic performance characteristics of the feedback control scheme for control of temperature in perfused media. The results of these tests are presented and compared with the predictions of a simulation routine. The control scheme was also tested in vivo using dogs' thighs and kidneys. Thigh experiments show the control scheme responds well to the affects of vasodilation and is able to maintain the targeted temperatures. In kidney experiments, where the rate of perfusion was controllable, the power adjusting algorithm successfully maintained uniform temperature distributions across regions of varying rates of perfusion. As a conclusion, the results show that this multipoint feedback controller scheme induces uniform temperature distributions when used with scanned focussed ultrasound systems

Simulations of the TESLA Linear Collider with a Fast Feedback System

CERN Document Server

Schulte, Daniel; White, G

2003-01-01

The tolerances on the beams as they collide at the interaction point of the TESLA linear collider are very tight due to the nano-metre scale final vertical bunch spot sizes. Ground motion causes the beams to increase in emittance and drift out of collision leading to dramatic degradation of luminosity performance. To combat this, both slow orbit and fast intra-train feedback systems will be used. The design of these feedback systems depends critically on how component misalignment effects the beam throughout the whole accelerator. A simulation has been set up to study in detail the accelerator performance under such conditions by merging the codes of PLACET, MERLIN and GUINEA-PIG together with Simulink code to model feedback systems, all under a Matlab environment.

Automatic Thermal Control System with Temperature Difference or Derivation Feedback

Directory of Open Access Journals (Sweden)

Darina Matiskova

2016-02-01

Full Text Available Automatic thermal control systems seem to be non-linear systems with thermal inertias and time delay. A controller is also non-linear because its information and power signals are limited. The application of methods that are available to on-linear systems together with computer simulation and mathematical modelling creates a possibility to acquire important information about the researched system. This paper provides a new look at the heated system model and also designs the structure of the thermal system with temperature derivation feedback. The designed system was simulated by using a special software in Turbo Pascal. Time responses of this system are compared to responses of a conventional thermal system. The thermal system with temperature derivation feedback provides better transients, better quality of regulation and better dynamical properties.

Uplink Contention-based CSI Feedback with Prioritized Layers for a Multi-Carrier System

DEFF Research Database (Denmark)

Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar

2012-01-01

, several works have considered contention-based CSI feedback in the UL control channel. We propose such a feedback scheme for a generic MC system, based on the idea of variable collision protection, where the probability that a feedback information experiences a collision depends on its importance......Optimized resource allocation of the Downlink (DL) in wireless systems utilizing Multi-Carrier (MC) transmission requires Channel State Information (CSI) feedback for each user/subchannel to the Base Station (BS), consuming a high amount of Uplink (UL) radio resources. To alleviate this problem...

Bayesian feedback versus Markovian feedback in a two-level atom

International Nuclear Information System (INIS)

Wiseman, H.M.; Mancini, Stefano; Wang Jin

2002-01-01

We compare two different approaches to the control of the dynamics of a continuously monitored open quantum system. The first is Markovian feedback, as introduced in quantum optics by Wiseman and Milburn [Phys. Rev. Lett. 70, 548 (1993)]. The second is feedback based on an estimate of the system state, developed recently by Doherty and Jacobs [Phys. Rev. A 60, 2700 (1999)]. Here we choose to call it, for brevity, Bayesian feedback. For systems with nonlinear dynamics, we expect these two methods of feedback control to give markedly different results. The simplest possible nonlinear system is a driven and damped two-level atom, so we choose this as our model system. The monitoring is taken to be homodyne detection of the atomic fluorescence, and the control is by modulating the driving. The aim of the feedback in both cases is to stabilize the internal state of the atom as close as possible to an arbitrarily chosen pure state, in the presence of inefficient detection and other forms of decoherence. Our results (obtained without recourse to stochastic simulations) prove that Bayesian feedback is never inferior, and is usually superior, to Markovian feedback. However, it would be far more difficult to implement than Markovian feedback and it loses its superiority when obvious simplifying approximations are made. It is thus not clear which form of feedback would be better in the face of inevitable experimental imperfections

Real-time system for studies of the effects of acoustic feedback on animal vocalizations.

Directory of Open Access Journals (Sweden)

Mike eSkocik

2013-01-01

Full Text Available Studies of behavioral and neural responses to distorted auditory feedback can help shed light on the neural mechanisms of animal vocalizations. We describe an apparatus for generating real-time acoustic feedback. The system can very rapidly detect acoustic features in a song and output acoustic signals if the detected features match the desired acoustic template. The system uses spectrogram-based detection of acoustic elements. It is low-cost and can be programmed for a variety of behavioral experiments requiring acoustic feedback or neural stimulation. We use the system to study the effects of acoustic feedback on birds' vocalizations and demonstrate that such an acoustic feedback can cause both immediate and long-term changes to birds’ songs.

Practice of knowledge management for institutes--take the construction of experience feedback system as the example

International Nuclear Information System (INIS)

Wu Kaiping

2014-01-01

The construction of experience feedback system is an important part and breakthrough point of institutes' knowledge management. It is significant for institutes' design, management, development and innovation. This article introduces the concept of experience feedback for institutes. It also goes details of the content of experience feedback system construction for institutes, including the founding of experience feedback organizational mechanism, the development of experience feedback system, construction of knowledge database system, the construction of knowledge resources, and the appraisal of experience feedback's performance. Furthermore, the recognition and support of leaders, understanding and cooperation of relative departments, and corporation's culture of encouraging knowledge sharing, also are the important guarantees for the good effects of institutes' experience feedback work. (author)

Robust synchronization of chaotic systems via feedback

Energy Technology Data Exchange (ETDEWEB)

Femat, Ricardo [IPICYT, San Luis Potosi (Mexico). Dept. de Matematicas Aplicadas; Solis-Perales, Gualberto [Universidad de Guadalajara, Centro Univ. de Ciencias Exactas e Ingenierias (Mexico). Div. de Electronica y Computacion

2008-07-01

This volume includes the results derived during last ten years about both suppression and synchronization of chaotic -continuous time- systems. Along this time, the concept was to study how the intrinsic properties of dynamical systems can be exploited to suppress and to synchronize the chaotic behaviour and what synchronization phenomena can be found under feedback interconnection. A compilation of these findings is described in this book. This book shows a perspective on synchronization of chaotic systems. (orig.)

Methane Feedbacks to the Global Climate System in a Warmer World

Science.gov (United States)

Dean, Joshua F.; Middelburg, Jack J.; Röckmann, Thomas; Aerts, Rien; Blauw, Luke G.; Egger, Matthias; Jetten, Mike S. M.; de Jong, Anniek E. E.; Meisel, Ove H.; Rasigraf, Olivia; Slomp, Caroline P.; in't Zandt, Michiel H.; Dolman, A. J.

2018-03-01

Methane (CH4) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH4 budgets, as well as future shifts in CH4 emissions, have high uncertainties. Climate change has the potential to increase CH4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment-specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH4 climate feedback up to 2100. Beyond this timescale, CH4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH4 consumption can counterbalance CH4 production under future climate scenarios.

Practical Loop-Shaping Design of Feedback Control Systems

Science.gov (United States)

Kopasakis, George

2010-01-01

An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design. The conception of this improved methodology was motivated by challenges in designing control systems of the types needed for supersonic propulsion. But the methodology is generally applicable to any classical control-system design where the transfer function of the plant is known or can be evaluated. In the case of a supersonic aerospace vehicle, a major challenge is to design the system to attenuate anticipated external and internal disturbances, using such actuators as fuel injectors and valves, bypass doors, and ramps, all of which are subject to limitations in actuator response, rates, and ranges. Also, for supersonic vehicles, with long slim type of structures, coupling between the engine and the structural dynamics can produce undesirable effects that could adversely affect vehicle stability and ride quality. In order to design distributed controls that can suppress these potential adverse effects, within the full capabilities of the actuation system, it is important to employ a systematic control design methodology such as this that can maximize the

Swing Damping for Helicopter Slung Load Systems using Delayed Feedback

DEFF Research Database (Denmark)

Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

2009-01-01

of swing. The design of the delayed feedback controller is presented as an optimization problem which gives the possibility of an automated design process. Simulations and flight test verifications of the control system on two different autonomous helicopters are presented and it is shown how a significant......This paper presents the design and verification of a swing reducing controller for helicopter slung load systems using intentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous...... helicopters. The delayed feedback controller is added to actively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integration with a feedforward control scheme based on input shaping for concurrent avoidance and dampening...

Decoherence control in open quantum systems via classical feedback

International Nuclear Information System (INIS)

Ganesan, Narayan; Tarn, Tzyh-Jong

2007-01-01

In this work we propose a strategy using techniques from systems theory to completely eliminate decoherence and also provide conditions under which it can be done. A construction employing an auxiliary system, the bait, which is instrumental to decoupling the system from the environment is presented. Our approach to decoherence control in contrast to other approaches in the literature involves the bilinear input affine model of quantum control system which lends itself to various techniques from classical control theory, but with nontrivial modifications to the quantum regime. The elegance of this approach yields interesting results on open loop decouplability and decoherence free subspaces. Additionally, the feedback control of decoherence may be related to disturbance decoupling for classical input affine systems, which entails careful application of the methods by avoiding all the quantum mechanical pitfalls. In the process of calculating a suitable feedback the system must be restructured due to its tensorial nature of interaction with the environment, which is unique to quantum systems. In the subsequent section we discuss a general information extraction scheme to gain knowledge of the state and the amount of decoherence based on indirect continuous measurement. The analysis of continuous measurement on a decohering quantum system has not been extensively studied before. Finally, a methodology to synthesize feedback parameters itself is given, that technology permitting, could be implemented for practical 2-qubit systems to perform decoherence free quantum computing. The results obtained are qualitatively different and superior to the ones obtained via master equations

Introducing BF++: AC++ framework for cognitive bio-feedback systems design.

Science.gov (United States)

Bianchi, L; Babiloni, F; Cincotti, F; Salinari, S; Marciani, M G

2003-01-01

This paper addressed the issue of building-up a framework for the realization of several cognitive bio-feedback (CBF) systems. It minimizes the programming effort and maximizes the efficiency and the cross-platform portability so that it can be used with many platforms (either software or hardware). A generic CBF system was decomposed into six modules: acquisition, kernel, feedback rule, patient feedback, operator user interface and persistent storage. The way in which these modules interact was defined by immutable software interfaces in a way that allows to completely substitute a module without the need to modify the others. Three Brain Computer Interface engines were developed with less than 40 lines of C++ code each. They can also be used under virtually any platform that supports an ANSI C++ compiler. A framework for the implementation of a wide range of CBF systems was developed. Compared to the other approaches that are described in the literature, the proposed one is the most efficient, the most protable across different platforms, the most generic and the one that allows the realization of the cheapest final systems.

Effects of error feedback on a nonlinear bistable system with stochastic resonance

International Nuclear Information System (INIS)

Li Jian-Long; Zhou Hui

2012-01-01

In this paper, we discuss the effects of error feedback on the output of a nonlinear bistable system with stochastic resonance. The bit error rate is employed to quantify the performance of the system. The theoretical analysis and the numerical simulation are presented. By investigating the performances of the nonlinear systems with different strengths of error feedback, we argue that the presented system may provide guidance for practical nonlinear signal processing

Optimal feedback control of the forced van der Pol system

International Nuclear Information System (INIS)

Chagas, T.P.; Toledo, B.A.; Rempel, E.L.; Chian, A.C.-L.; Valdivia, J.A.

2012-01-01

A simple feedback control strategy for chaotic systems is investigated using the forced van der Pol system as an example. The strategy regards chaos control as an optimization problem, where the maximum magnitude Floquet multiplier of a target unstable periodic orbit (UPO) is used as a cost function that needs to be minimized. Thus, the method obtains the optimal control gain in terms of the stability of the target UPO. This strategy was recently proposed for the proportional feedback control (PFC) method. Here, it is extended to the highly popular delayed feedback control (DFC) method. Since the DFC method treats the system as a delay-differential equation whose phase space is infinite-dimensional, the characteristic multipliers are found through a truncation in the number of delayed states. Control of a target UPO is achieved for several values of the forcing amplitude. We compare the DFC and PFC methods in terms of stability of the controlled orbit, steady state error and control effort.

Fast feedback system for energy and beam stabilization

International Nuclear Information System (INIS)

R. Dickson; V. Lebedev

1999-01-01

The electron beams being delivered to targets of the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson National Accelerator Facility (Jefferson Lab) are plagued with undesirable positional and energy fluctuations. These fluctuations primarily occur at harmonics of the power line frequency (60, 120, 180, etc. hertz), and their cause is rooted in electromagnetic fields generated by accelerator electronic equipment. It is possible to largely nullify these deviations by applying real time corrections to electromagnets and RF verniers along the beam line. This concept has been successfully applied at Jefferson Lab by extensively modifying the existing Beam Position Monitor (BPM) system with the integration of an algorithm that computes correction signals targeted at the power line harmonics. Many of the modifications required were due to the existing CEBAF BPM system not having the data acquisition bandwidth needed for this type of feedback system. This paper will describe the techniques required to transform the CEBAF standard BPM system into a high speed practical fast feedback system that coexists with the large scale control system--the Experimental Physics and Industrial Control System (EPICS)--that runs the CEBAF accelerator in daily operation

Chaos control for the family of Roessler systems using feedback controllers

International Nuclear Information System (INIS)

Liao Xiaoxin; Yu Pei

2006-01-01

This paper presents a new method for controlling chaos in several classical chaotic Roessler systems using feedback control strategy. In particular, for an arbitrarily given equilibrium point of a Roessler system, we design explicit and simple feedback control laws by which the equilibrium point is globally and exponentially stabilized. Six typical Roessler systems are studied, and explicit formulas are derived for estimating the convergence rate of these systems. Numerical examples are presented to illustrate the theoretical results. A mistake has been found in the existing literature, and a correct result is given

Bunch-by-bunch longitudinal feedback system for PEP-II

International Nuclear Information System (INIS)

Oxoby, G.; Claus, R.; Fox, J.

1994-06-01

This paper describes the implementation of the bunch-by-bunch longitudinal feedback system for the PEP-II B Factory. Bunch spacing down to 2 ns is achieved using 500 Megasamples per second A/D and D/A converters, and AT ampersand T 1610 Digital Signal Processors are integrated to run a downsampled feedback algorithm for each bunch in parallel. This general purpose programmable system, packaged in VXI and VME, is modular and scalable to offer portability to other accelerator rings. The control and monitoring hardware and software architecture have been developed to provide ease of operation as well as diagnostic tools for machine physics

Event-triggered output feedback control for distributed networked systems.

Science.gov (United States)

Mahmoud, Magdi S; Sabih, Muhammad; Elshafei, Moustafa

2016-01-01

This paper addresses the problem of output-feedback communication and control with event-triggered framework in the context of distributed networked control systems. The design problem of the event-triggered output-feedback control is proposed as a linear matrix inequality (LMI) feasibility problem. The scheme is developed for the distributed system where only partial states are available. In this scheme, a subsystem uses local observers and share its information to its neighbors only when the subsystem's local error exceeds a specified threshold. The developed method is illustrated by using a coupled cart example from the literature. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

ASSESSMENT OF THE VOLUNTEERED GEOGRAPHIC INFORMATION FEEDBACK SYSTEM FOR THE DUTCH TOPOGRAPHICAL KEY REGISTER

Directory of Open Access Journals (Sweden)

M. Grus

2015-08-01

Full Text Available Since Topographical Key Register has become an open data the amount of users increased enormously. The highest grow was in the private users group. The increasing number of users and their growing demand for high actuality of the topographic data sets motivates the Dutch Kadaster to innovate and improve the Topographical Key Register (BRT. One of the initiatives was to provide a voluntary geographical information project aiming at providing a user-friendly feedback system adjusted to all kinds of user groups. The feedback system is a compulsory element of the Topographical Key Register in the Netherlands. The Dutch Kadaster is obliged to deliver a feedback system and the key-users are obliged to use it. The aim of the feedback system is to improve the quality and stimulate the usage of the data. The results of the pilot shows that the user-friendly and open to everyone feedback system contributes enormously to improve the quality of the topographic dataset.

The pointer basis and the feedback stabilization of quantum systems

International Nuclear Information System (INIS)

Li, L; Chia, A; Wiseman, H M

2014-01-01

The dynamics for an open quantum system can be ‘unravelled’ in infinitely many ways, depending on how the environment is monitored, yielding different sorts of conditioned states, evolving stochastically. In the case of ideal monitoring these states are pure, and the set of states for a given monitoring forms a basis (which is overcomplete in general) for the system. It has been argued elsewhere (Atkins et al 2005 Europhys. Lett. 69 163) that the ‘pointer basis’ as introduced by Zurek et al (1993 Phys. Rev. Lett. 70 1187), should be identified with the unravelling-induced basis which decoheres most slowly. Here we show the applicability of this concept of pointer basis to the problem of state stabilization for quantum systems. In particular we prove that for linear Gaussian quantum systems, if the feedback control is assumed to be strong compared to the decoherence of the pointer basis, then the system can be stabilized in one of the pointer basis states with a fidelity close to one (the infidelity varies inversely with the control strength). Moreover, if the aim of the feedback is to maximize the fidelity of the unconditioned system state with a pure state that is one of its conditioned states, then the optimal unravelling for stabilizing the system in this way is that which induces the pointer basis for the conditioned states. We illustrate these results with a model system: quantum Brownian motion. We show that even if the feedback control strength is comparable to the decoherence, the optimal unravelling still induces a basis very close to the pointer basis. However if the feedback control is weak compared to the decoherence, this is not the case. (paper)

Performance Analysis of Simple Channel Feedback Schemes for a Practical OFDMA System

DEFF Research Database (Denmark)

Pedersen, Klaus, I.; Kolding, Troels; Kovacs, Istvan

2009-01-01

In this paper, we evaluate the tradeoff between the amount of uplink channel feedback information and the orthogonal frequency-division multiple access (OFDMA) downlink performance with opportunistic frequency-domain packet scheduling. Three candidate channel feedback schemes are investigated......, including practical aspects, such as the effects of terminal measurement errors, bandwidth measurement granularity, quantization, and uplink signaling delays. The performance is evaluated by means of system-level simulations with detailed modeling of various radio resource-management algorithms, etc. Our...... results show that the optimal tradeoff between the channel feedback and the downlink OFDMA system performance depends on the radio channel frequency coherence bandwidth. We conclude that the so-called average best-M scheme is the most attractive channel feedback solution, where only the average channel...

Feedback Loop Gains and Feedback Behavior (1996)

DEFF Research Database (Denmark)

Kampmann, Christian Erik

2012-01-01

Linking feedback loops and system behavior is part of the foundation of system dynamics, yet the lack of formal tools has so far prevented a systematic application of the concept, except for very simple systems. Having such tools at their disposal would be a great help to analysts in understanding...... large, complicated simulation models. The paper applies tools from graph theory formally linking individual feedback loop strengths to the system eigenvalues. The significance of a link or a loop gain and an eigenvalue can be expressed in the eigenvalue elasticity, i.e., the relative change...... of an eigenvalue resulting from a relative change in the gain. The elasticities of individual links and loops may be found through simple matrix operations on the linearized system. Even though the number of feedback loops can grow rapidly with system size, reaching astronomical proportions even for modest systems...

Use of synchronous e-learning at university degrees

OpenAIRE

Fita Fernández, Ana María; Monserrat del Río, Jose Francisco; Moltó Martínez, Germán; Mestre i Mestre, Eva María; Rodríguez Burruezo, Adrián

2016-01-01

Different types of Course Management Systems (CMS) are fully integrated in conventional and online courses in many Universities degrees. Although they are suitable for lecturer-student information sharing, their asynchronous nature prevents an efficient interaction, which may hamper the learning process. As an alternative, synchronous virtual learning platforms can help fill the gaps in traditional CMS. However, there is very little feedback regarding its use in higher education. The Universi...

Feature-Specific Organization of Feedback Pathways in Mouse Visual Cortex.

Science.gov (United States)

Huh, Carey Y L; Peach, John P; Bennett, Corbett; Vega, Roxana M; Hestrin, Shaul

2018-01-08

Higher and lower cortical areas in the visual hierarchy are reciprocally connected [1]. Although much is known about how feedforward pathways shape receptive field properties of visual neurons, relatively little is known about the role of feedback pathways in visual processing. Feedback pathways are thought to carry top-down signals, including information about context (e.g., figure-ground segmentation and surround suppression) [2-5], and feedback has been demonstrated to sharpen orientation tuning of neurons in the primary visual cortex (V1) [6, 7]. However, the response characteristics of feedback neurons themselves and how feedback shapes V1 neurons' tuning for other features, such as spatial frequency (SF), remain largely unknown. Here, using a retrograde virus, targeted electrophysiological recordings, and optogenetic manipulations, we show that putatively feedback neurons in layer 5 (hereafter "L5 feedback") in higher visual areas, AL (anterolateral area) and PM (posteromedial area), display distinct visual properties in awake head-fixed mice. AL L5 feedback neurons prefer significantly lower SF (mean: 0.04 cycles per degree [cpd]) compared to PM L5 feedback neurons (0.15 cpd). Importantly, silencing AL L5 feedback reduced visual responses of V1 neurons preferring low SF (mean change in firing rate: -8.0%), whereas silencing PM L5 feedback suppressed responses of high-SF-preferring V1 neurons (-20.4%). These findings suggest that feedback connections from higher visual areas convey distinctly tuned visual inputs to V1 that serve to boost V1 neurons' responses to SF. Such like-to-like functional organization may represent an important feature of feedback pathways in sensory systems and in the nervous system in general. Copyright © 2017 Elsevier Ltd. All rights reserved.

Edge turbulence control on the KT-5C tokamak by feedback using electrostatic probes

International Nuclear Information System (INIS)

Zhai Kan; Wang Cheng; Wen Yizi; Yu Changxuan; Wan Shude; Liu Wandong; Xu Zhizhan

1998-01-01

Experiments on edge turbulence control have been performed on the KT-5C tokamak by feedback using two sets of electrostatic probes as the driving probe and detective probe. The results indicate that the feedback can enhance or reduce the turbulence amplitude depending upon the phase shift and gain of the feedback network. When the feedback with 90 degree phase shift and with certain loop gain is applied, the spectrum component of turbulence is reduced obviously and the fluctuation amplitude of the electron density and electron temperature become lower by about 25%. consistently the particle flux across the magnetic field induced by the electrostatic fluctuation also decreases by about 25%. On the other hand, the feedback with 0 degree or 180 degree or -90 degree phase shift can enhance the amplitude of the edge turbulence. These results indicate a nonlinear mechanism of the influence of feedback on the edge turbulence, which to some extent also reflect a specific nonlinear characteristic of the edge turbulence

The Vibe of Skating; Design and Testing of a Vibro-Tactile Feedback System

Directory of Open Access Journals (Sweden)

Arjen J. Jansen

2018-03-01

Full Text Available Providing athletes with real-time feedback on their performance is becoming common in many sports, also in speed skating. This research-by-design project aims at finding a tool that allows the speed skater to get real-time feedback on his performance. Speed skaters often mention a so-called “good feeling” when skating behind a better skater. It is the feeling nearly every speed skater is after when skating alone; skate with less power while maintaining the same speed and feeling of ease. A longer push-off phase at a constant cadence has proven to contribute to this ideal situation but is hard for the coach alone to influence this. Therefore, a system was designed that measures the skating cadence and challenges the skater to change his skating stroke by means of vibro-tactile feedback. Four subjects have tested the feedback system. From this test, we concluded that the system provides meaningful feedback towards changing the skating cycle.

Feedback linearizing control of a MIMO power system

Science.gov (United States)

Ilyes, Laszlo

Prior research has demonstrated that either the mechanical or electrical subsystem of a synchronous electric generator may be controlled using single-input single-output (SISO) nonlinear feedback linearization. This research suggests a new approach which applies nonlinear feedback linearization to a multi-input multi-output (MIMO) model of the synchronous electric generator connected to an infinite bus load model. In this way, the electrical and mechanical subsystems may be linearized and simultaneously decoupled through the introduction of a pair of auxiliary inputs. This allows well known, linear, SISO control methods to be effectively applied to the resulting systems. The derivation of the feedback linearizing control law is presented in detail, including a discussion on the use of symbolic math processing as a development tool. The linearizing and decoupling properties of the control law are validated through simulation. And finally, the robustness of the control law is demonstrated.

Students' Informal Peer Feedback Networks

Science.gov (United States)

Headington, Rita

2018-01-01

The nature and significance of students' informal peer feedback networks is an under-explored area. This paper offers the findings of a longitudinal investigation of the informal peer feedback networks of a cohort of student teachers [n = 105] across the three years of a UK primary education degree programme. It tracked the dynamic nature of these…

Hardware design and implementation of the closed-orbit feedback system at APS

International Nuclear Information System (INIS)

Barr, D.; Chung, Youngjoo.

1996-01-01

The Advanced Photon Source (APS) storage ring will utilize a closed-orbit feedback system in order to produce a more stable beam. The specified orbit measurement resolution is 25 microns for global feedback and 1 micron for local feedback. The system will sample at 4 kHz and provide a correction bandwidth of 100 Hz. At this bandwidth, standard rf BPMs will provide a resolution of 0.7 micron, while specialized miniature BPMs positioned on either side of the insertion devices for local feedback will provide a resolution of 0.2 micron (1). The measured BPM noise floor for standard BPMs is 0.06 micron per root hertz mA. Such a system has been designed, simulated, and tested on a small scale (2). This paper covers the actual hardware design and layout of the entire closed-loop system. This includes commercial hardware components, in addition to many components designed and built in-house. The paper will investigate the large-scale workings of all these devices, as well as an overall view of each piece of hardware used

Mining Feedback in Ranking and Recommendation Systems

Science.gov (United States)

Zhuang, Ziming

2009-01-01

The amount of online information has grown exponentially over the past few decades, and users become more and more dependent on ranking and recommendation systems to address their information seeking needs. The advance in information technologies has enabled users to provide feedback on the utilities of the underlying ranking and recommendation…

Develop feedback system for intelligent dynamic resource allocation to improve application performance.

Energy Technology Data Exchange (ETDEWEB)

Gentile, Ann C.; Brandt, James M.; Tucker, Thomas (Open Grid Computing, Inc., Austin, TX); Thompson, David

2011-09-01

This report provides documentation for the completion of the Sandia Level II milestone 'Develop feedback system for intelligent dynamic resource allocation to improve application performance'. This milestone demonstrates the use of a scalable data collection analysis and feedback system that enables insight into how an application is utilizing the hardware resources of a high performance computing (HPC) platform in a lightweight fashion. Further we demonstrate utilizing the same mechanisms used for transporting data for remote analysis and visualization to provide low latency run-time feedback to applications. The ultimate goal of this body of work is performance optimization in the face of the ever increasing size and complexity of HPC systems.

Advantages of externally powered prosthesis with feedback system using pseudo-cineplasty.

Science.gov (United States)

Nambu, Seiji; Ikebuchi, Mitsuhiko; Taniguchi, Masashi; Park, Choong Sik; Kitagawa, Takahiro; Nakajima, Shigeyoshi; Koike, Tatsuya

2014-01-01

Externally powered upper-limb prostheses are difficult to use because of the lack of sensory feedback. Neuroprostheses have recently been developed for people with upper-limb amputation but are complicated, expensive, and still developing. We therefore designed a simple system by combining pseudo-cineplasty with extended physiological proprioception to provide sensory feedback to the body. We penetrated the palmaris longus tendon percutaneously with a metal ring, similar to that used in body piercing, in a nondisabled subject as a pseudo-cineplasty. The tendon and ring were connected to the system, and a sensory feedback experiment was performed. We investigated the ability of the user to determine the size of an object grasped by the prosthetic hand without visual information. The subject could distinguish between large and small objects with 100% accuracy and between small, medium, and large objects with 80% accuracy. In pseudo-cineplasty, control and sensory feedback are natural because the prosthetic hand is controlled by muscle contraction. Tension transmitted from the prosthetic hand is sensed via muscle spindles and skin sensors. This technique allows only partial sensory feedback but appears to offer several advantages over other human-machine interfaces.

Output Feedback M-MRAC Backstepping With Aerospace Applications

Science.gov (United States)

Stepanyan, Vahram; Krishnakumar, Kalmanje Sriniva

2014-01-01

The paper presents a certainty equivalence output feedback backstepping adaptive control design method for the systems of any relative degree with unmatched uncertainties without over-parametrization. It uses a fast prediction model to estimate the unknown parameters, which is independent of the control design. It is shown that the system's input and output tracking errors can be systematically decreased by the proper choice of the design parameters. The approach is applied to aerospace control problems and tested in numerical simulations.

Synchronization of spatiotemporal chaotic systems by feedback control

International Nuclear Information System (INIS)

Lai, Y.; Grebogi, C.

1994-01-01

We demonstrate that two identical spatiotemporal chaotic systems can be synchronized by (1) linking one or a few of their dynamical variables, and (2) applying a small feedback control to one of the systems. Numerical examples using the diffusively coupled logistic map lattice are given. The effect of noise and the limitation of the technique are discussed

Synchronization of coupled nonidentical multidelay feedback systems

International Nuclear Information System (INIS)

Hoang, Thang Manh; Nakagawa, Masahiro

2007-01-01

We present the lag synchronization of coupled nonidentical multidelay feedback systems, in which the synchronization signal is the sum of nonlinearly transformed components of delayed state variable. The sufficient condition for synchronization is considered by the Krasovskii-Lyapunov theory. The specific examples will demonstrate and verify the effectiveness of the proposed model

Commissioning of the iGp Feedback System at DAΦNE

International Nuclear Information System (INIS)

Drago, A.; Fox, J.D.; Teytelman, D.; Tobiyama, M.

2011-01-01

The iGp (Integrated Gigasample Processor) is an innovative digital bunch-by-bunch feedback system developed by a KEK / SLAC / INFN-LNF joint collaboration. The processing unit can sample at 500 MHz and compute the bunch-by-bunch output signal for up to ∼5000 bunches. The feedback gateware code is implemented inside just one FPGA (Field Programmable Gate Array) chip, a Xilinx Virtex-II. The FPGA implements two banks of 16-tap FIR (Finite Impulse Response) filters. Each filter is realtime programmable through the operator interface. At DAΦNE, the Frascati Φ-Factory, two iGp units have been commissioned in the April 2007. The iGp systems have substituted the previous betatron feedback systems. This insertion has been very fast and has shown no problems involving just a substitution of the old, less flexible, digital systems, letting unchanged the baseband analog frontend and backend. The commissioning has been very simple, due to the complete and powerful EPICS operator interface, working well in local and remote operations. The software includes also tools for analyzing post processor data. A description of the commissioning with the operations done is reported.

Commissioning of the APS real-time orbit feedback system

International Nuclear Information System (INIS)

Carwardine, J.; Decker, G.; Evans, K. Jr.; Hillman, A.; Lenkszus, F.; Merl, R.; Pietryla, A.

1997-01-01

A unified global and local closed-orbit feedback system has been implemented at the Advanced Photon Source in order to stabilize both particle and photon beams. Beam stability requirements in the band up to 50 Hz are 17 microm in the horizontal plane and 4.4 microm vertically. Orbit feedback algorithms are implemented digitally using multiple digital signal processors, with computing power distributed in 20 VME crates around the storage ring. Each crate communicates with all others via a fast reflective memory network. The system has access to 320 rf beam position monitors together with x-ray beam position monitors in both insertion device and bending magnet beamlines. Up to 317 corrector magnets are available to the system. The global system reduces horizontal rms beam motion at the x-ray source points by more than a factor of two in the frequency band from 10 mHz to 50 Hz

Investigation of control system of traction electric drive with feedbacks on load

Science.gov (United States)

Kuznetsov, N. K.; Iov, I. A.; Iov, A. A.

2018-03-01

In the article, by the example of a walking excavator, the results of a study of a control system of traction electric drive with a rigid and flexible feedback on the load are mentioned. Based on the analysis of known works, the calculation scheme has been chosen; the equations of motion of the electromechanical system have been obtained, taking into account the elasticity of the rope and feedbacks on the load in the elastic element. A simulation model of this system has been developed and mathematical modeling of the transient processes to evaluate the influence of feedback on the dynamic characteristics of the mechanism and its efficiency of work was carried out. It is shown that the use of rigid and flexible feedbacks makes it possible to reduce dynamic loads in the traction mechanism and to limit the elastic oscillation of the executive mechanism in transient operating modes in comparison with the standard control system; however, there is some decrease in productivity. It has been also established that the sign-variable of the loading of the electric drive, connected with the opening of the backlashes in the gearbox due to the action of feedbacks on the load in the elastic element, under certain conditions, can lead to undesirable phenomena in the operation of the drive and a decrease in the reliability of its operation.

The effects of feedback self-consistency, therapist status, and attitude toward therapy on reaction to personality feedback.

Science.gov (United States)

Collins, David R; Stukas, Arthur A

2006-08-01

Individuals' reactions to interpersonal feedback may depend on characteristics of the feedback and the feedback source. The present authors examined the effects of experimentally manipulated personality feedback that they--in the guise of therapists--e-mailed to participants on the degree of their acceptance of the feedback. Consistent with Self-Verification Theory (W. B. Swann Jr., 1987), participants accepted feedback that was consistent with their self-views more readily than they did feedback that was inconsistent with their self-views. Furthermore, the authors found main effects for therapist's status and participant's attitude toward therapy. Significant interactions showed effects in which high-status therapists and positive client attitudes increased acceptance of self-inconsistent feedback, effects that were only partially mediated by clients' perceptions of therapist competence. The present results indicate the possibility that participants may be susceptible to self-concept change or to self-fulfilling prophecy effects in therapy when they have a positive attitude toward therapy or are working with a high-status therapist.

Study on real-time force feedback for a master-slave interventional surgical robotic system.

Science.gov (United States)

Guo, Shuxiang; Wang, Yuan; Xiao, Nan; Li, Youxiang; Jiang, Yuhua

2018-04-13

In robot-assisted catheterization, haptic feedback is important, but is currently lacking. In addition, conventional interventional surgical robotic systems typically employ a master-slave architecture with an open-loop force feedback, which results in inaccurate control. We develop herein a novel real-time master-slave (RTMS) interventional surgical robotic system with a closed-loop force feedback that allows a surgeon to sense the true force during remote operation, provide adequate haptic feedback, and improve control accuracy in robot-assisted catheterization. As part of this system, we also design a unique master control handle that measures the true force felt by a surgeon, providing the basis for the closed-loop control of the entire system. We use theoretical and empirical methods to demonstrate that the proposed RTMS system provides a surgeon (using the master control handle) with a more accurate and realistic force sensation, which subsequently improves the precision of the master-slave manipulation. The experimental results show a substantial increase in the control accuracy of the force feedback and an increase in operational efficiency during surgery.

Cooling optically levitated dielectric nanoparticles via parametric feedback

Science.gov (United States)

Neukirch, Levi; Rodenburg, Brandon; Bhattacharya, Mishkatul; Vamivakas, Nick

2015-05-01

The inability to leverage resonant scattering processes involving internal degrees of freedom differentiates optical cooling experiments performed with levitated dielectric nanoparticles, from similar atomic and molecular traps. Trapping in optical cavities or the application of active feedback techniques have proven to be effective ways to circumvent this limitation. We present our nanoparticle optical cooling apparatus, which is based on parametric feedback modulation of a single-beam gradient force optical trap. This scheme allows us to achieve effective center-of-mass temperatures well below 1 kelvin for our ~ 1 ×10-18 kg particles, at modest vacuum pressures. The method provides a versatile platform, with parameter tunability not found in conventional tethered nanomechanical systems. Potential applications include investigations of nonequilibrium nanoscale thermodynamics, ultra-sensitive force metrology, and mesoscale quantum mechanics and hybrid systems. Supported by the office of Naval Research award number N000141410442.

Variance decomposition shows the importance of human-climate feedbacks in the Earth system

Science.gov (United States)

Calvin, K. V.; Bond-Lamberty, B. P.; Jones, A. D.; Shi, X.; Di Vittorio, A. V.; Thornton, P. E.

2017-12-01

The human and Earth systems are intricately linked: climate influences agricultural production, renewable energy potential, and water availability, for example, while anthropogenic emissions from industry and land use change alter temperature and precipitation. Such feedbacks have the potential to significantly alter future climate change. Current climate change projections contain significant uncertainties, however, and because Earth System Models do not generally include dynamic human (demography, economy, energy, water, land use) components, little is known about how climate feedbacks contribute to that uncertainty. Here we use variance decomposition of a novel coupled human-earth system model to show that the influence of human-climate feedbacks can be as large as 17% of the total variance in the near term for global mean temperature rise, and 11% in the long term for cropland area. The near-term contribution of energy and land use feedbacks to the climate on global mean temperature rise is as large as that from model internal variability, a factor typically considered in modeling studies. Conversely, the contribution of climate feedbacks to cropland extent, while non-negligible, is less than that from socioeconomics, policy, or model. Previous assessments have largely excluded these feedbacks, with the climate community focusing on uncertainty due to internal variability, scenario, and model and the integrated assessment community focusing on uncertainty due to socioeconomics, technology, policy, and model. Our results set the stage for a new generation of models and hypothesis testing to determine when and how bidirectional feedbacks between human and Earth systems should be considered in future assessments of climate change.

Stability and Bifurcation in Magnetic Flux Feedback Maglev Control System

Directory of Open Access Journals (Sweden)

Wen-Qing Zhang

2013-01-01

Full Text Available Nonlinear properties of magnetic flux feedback control system have been investigated mainly in this paper. We analyzed the influence of magnetic flux feedback control system on control property by time delay and interfering signal of acceleration. First of all, we have established maglev nonlinear model based on magnetic flux feedback and then discussed hopf bifurcation’s condition caused by the acceleration’s time delay. The critical value of delayed time is obtained. It is proved that the period solution exists in maglev control system and the stable condition has been got. We obtained the characteristic values by employing center manifold reduction theory and normal form method, which represent separately the direction of hopf bifurcation, the stability of the period solution, and the period of the period motion. Subsequently, we discussed the influence maglev system on stability of by acceleration’s interfering signal and obtained the stable domain of interfering signal. Some experiments have been done on CMS04 maglev vehicle of National University of Defense Technology (NUDT in Tangshan city. The results of experiments demonstrate that viewpoints of this paper are correct and scientific. When time lag reaches the critical value, maglev system will produce a supercritical hopf bifurcation which may cause unstable period motion.

Stability of Nonlinear Systems with Unknown Time-varying Feedback Delay

Science.gov (United States)

Chunodkar, Apurva A.; Akella, Maruthi R.

2013-12-01

This paper considers the problem of stabilizing a class of nonlinear systems with unknown bounded delayed feedback wherein the time-varying delay is 1) piecewise constant 2) continuous with a bounded rate. We also consider application of these results to the stabilization of rigid-body attitude dynamics. In the first case, the time-delay in feedback is modeled specifically as a switch among an arbitrarily large set of unknown constant values with a known strict upper bound. The feedback is a linear function of the delayed states. In the case of linear systems with switched delay feedback, a new sufficiency condition for average dwell time result is presented using a complete type Lyapunov-Krasovskii (L-K) functional approach. Further, the corresponding switched system with nonlinear perturbations is proven to be exponentially stable inside a well characterized region of attraction for an appropriately chosen average dwell time. In the second case, the concept of the complete type L-K functional is extended to a class of nonlinear time-delay systems with unknown time-varying time-delay. This extension ensures stability robustness to time-delay in the control design for all values of time-delay less than the known upper bound. Model-transformation is used in order to partition the nonlinear system into a nominal linear part that is exponentially stable with a bounded perturbation. We obtain sufficient conditions which ensure exponential stability inside a region of attraction estimate. A constructive method to evaluate the sufficient conditions is presented together with comparison with the corresponding constant and piecewise constant delay. Numerical simulations are performed to illustrate the theoretical results of this paper.

Utility of an app-based system to improve feedback following workplace-based assessment.

Science.gov (United States)

Lefroy, Janet; Roberts, Nicola; Molyneux, Adrian; Bartlett, Maggie; Gay, Simon; McKinley, Robert

2017-05-31

To determine whether an app-based software system to support production and storage of assessment feedback summaries makes workplace-based assessment easier for clinical tutors and enhances the educational impact on medical students. We monitored our workplace assessor app's usage by Year 3 to 5 medical students in 2014-15 and conducted focus groups with Year 4 medical students and interviews with clinical tutors who had used the apps. Analysis was by constant comparison using a framework based on elements of van der Vleuten's utility index. The app may enhance the content of feedback for students. Using a screen may be distracting if the app is used during feedback discussions.    Educational impact was reduced by students' perceptions that an easy-to-produce feedback summary is less valuable than one requiring more tutor time and effort. Tutors' typing, dictation skills and their familiarity with mobile devices varied. This influenced their willingness to use the assessment and feedback mobile app rather than the equivalent web app. Electronic feedback summaries had more real and perceived uses than anticipated both for tutors and students including perceptions that they were for the school rather than the student. Electronic workplace-based assessment systems can be acceptable to tutors and can make giving detailed written feedback more practical but can interrupt the social interaction required for the feedback conversation. Tutor training and flexible systems will be required to minimise unwanted consequences. The educational impact on both tutors and students of providing pre-formulated advice within the app is worth further study.

A switched state feedback law for the stabilization of LTI systems.

Energy Technology Data Exchange (ETDEWEB)

Santarelli, Keith R.

2009-09-01

Inspired by prior work in the design of switched feedback controllers for second order systems, we develop a switched state feedback control law for the stabilization of LTI systems of arbitrary dimension. The control law operates by switching between two static gain vectors in such a way that the state trajectory is driven onto a stable n - 1 dimensional hyperplane (where n represents the system dimension). We begin by briefly examining relevant geometric properties of the phase portraits in the case of two-dimensional systems to develop intuition, and we then show how these geometric properties can be expressed as algebraic constraints on the switched vector fields that are applicable to LTI systems of arbitrary dimension. We then derive necessary and sufficient conditions to ensure stabilizability of the resulting switched system (characterized primarily by simple conditions on eigenvalues), and describe an explicit procedure for designing stabilizing controllers. We then show how the newly developed control law can be applied to the problem of minimizing the maximal Lyapunov exponent of the corresponding closed-loop state trajectories, and we illustrate the closed-loop transient performance of these switched state feedback controllers via multiple examples.

Student Self-Assessment and Multisource Feedback Assessment: Exploring Benefits, Limitations, and Remedies

Science.gov (United States)

Taylor, Scott N.

2014-01-01

It has become common practice for management students to participate in some sort of self-assessment or multisource feedback assessment (MSF; also called 360-degree assessment or multirater assessment) during their management degree program. These assessments provide students invaluable feedback about themselves and assist students in their…

Swing Damping for Helicopter Slung Load Systems using Delayed Feedback

OpenAIRE

Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

2009-01-01

This paper presents the design and verification of a swing reducing controller for helicopter slung load systems usingintentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous helicopters. The delayed feedback controller is added to actively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integra...

The design of delay-dependent wide-area DOFC with prescribed degree of stability α for damping inter-area low-frequency oscillations in power system.

Science.gov (United States)

Sun, Miaoping; Nian, Xiaohong; Dai, Liqiong; Guo, Hua

2017-05-01

In this paper, the delay-dependent wide-area dynamic output feedback controller (DOFC) with prescribed degree of stability is proposed for interconnected power system to damp inter-area low-frequency oscillations. Here, the prescribed degree of stability α is used to maintain all the poles on the left of s=-α in the s-plane. Firstly, residue approach is adopted to select input-output control signals and the schur balanced truncation model reduction method is utilized to obtain the reduced power system model. Secondly, based on Lyapunov stability theory and transformation operation in complex plane, the sufficient condition of asymptotic stability for closed-loop power system with prescribed degree of stability α is derived. Then, a novel method based on linear matrix inequalities (LMIs) is presented to obtain the parameters of DOFC and calculate delay margin of the closed-loop system considering the prescribed degree of stability α. Finally, case studies are carried out on the two-area four-machine system, which is controlled by classical wide-area power system stabilizer (WAPSS) in reported reference and our proposed DOFC respectively. The effectiveness and advantages of the proposed method are verified by the simulation results under different operating conditions. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Phase and amplitude feedback control system for the Los Alamos free-electron laser

International Nuclear Information System (INIS)

Lynch, M.T.; Tallerico, P.J.; Higgins, E.F.

1985-01-01

Phase and amplitude feedback control systems for the Los Alamos free-electron laser (FEL) are described. Beam-driven voltages are very high in the buncher cavity because the electron gun is pulsed at the fifth subharmonic of the buncher resonant frequency. The high beam loading necessitated a novel feedback and drive configuration for the buncher. A compensation cirucit has been added to the gun/driver system to reduce observed drift. Extremely small variations in the accelerator gradients had dramatic effects on the laser output power. These problems and how they were solved are described and plans for improvements in the feedback control system are discussed. 5 refs., 7 figs

Single feedback systems for simultaneous damping of horizontal and longitudinal coherent oscillations

International Nuclear Information System (INIS)

Chao, A.W.; Morton, P.L.; Rees, J.R.

1979-03-01

To describe the horizontal motion of the bunch, we need four coordinates, x and z are the horizontal and longitudinal displacements of the bunch center relative to the ideal trajectory; x' is the angle between the bunch's direction of motion and the ideal trajectory; and δ=ΔE/E is relative energy error of the bunch. Among the four variables, x and z are easy to measure by position monitors, while x' and δ are easy to change by electromagnetic devices. In combination, this suggests four possible types of feedback systems. In the following, we will present a complete analysis of the Type (x, δ) feedback system, using a matrix method. The analyses of other types are similar to that of Type (x, δ) and only the results are included. We then include some comparisons of these types of feedback schemes in terms of power consumptions and the effectiveness in damping the horizontal-betatron and synchrotron oscillations. We will also discuss some effects of position measuring errors on the performance of the feedback system. 2 refs., 3 tabs

On Optimal Feedback Control for Stationary Linear Systems

International Nuclear Information System (INIS)

Russell, David L.

2010-01-01

We study linear-quadratic optimal control problems for finite dimensional stationary linear systems AX+BU=Z with output Y=CX+DU from the viewpoint of linear feedback solution. We interpret solutions in relation to system robustness with respect to disturbances Z and relate them to nonlinear matrix equations of Riccati type and eigenvalue-eigenvector problems for the corresponding Hamiltonian system. Examples are included along with an indication of extensions to continuous, i.e., infinite dimensional, systems, primarily of elliptic type.

Thoracic ROM measurement system with visual bio-feedback: system design and biofeedback evaluation.

Science.gov (United States)

Ando, Takeshi; Kawamura, Kazuya; Fujitani, Junko; Koike, Tomokazu; Fujimoto, Masashi; Fujie, Masakatsu G

2011-01-01

Patients with diseases such as chronic obstructive pulmonary disease (COPD) need to improve their thorax mobility. Thoracic ROM is one of the simplest and most useful indexes to evaluate the respiratory function. In this paper, we have proposed the prototype of a simple thoracic ROM measurement system with real-time visual bio-feedback in the chest expansion test. In this system, the thoracic ROM is measured using a wire-type linear encoder whose wire is wrapped around the thorax. In this paper, firstly, the repeatability and reliability of measured thoracic ROM was confirmed as a first report of the developed prototype. Secondly, we analyzed the effect of the bio-feedback system on the respiratory function. The result of the experiment showed that it was easier to maintain a large and stable thoracic ROM during deep breathing by using the real-time visual biofeedback system of the thoracic ROM.

Real-time feedback for spatiotemporal field stabilization in MR systems.

Science.gov (United States)

Duerst, Yolanda; Wilm, Bertram J; Dietrich, Benjamin E; Vannesjo, S Johanna; Barmet, Christoph; Schmid, Thomas; Brunner, David O; Pruessmann, Klaas P

2015-02-01

MR imaging and spectroscopy require a highly stable, uniform background field. The field stability is typically limited by hardware imperfections, external perturbations, or field fluctuations of physiological origin. The purpose of the present work is to address these issues by introducing spatiotemporal field stabilization based on real-time sensing and feedback control. An array of NMR field probes is used to sense the field evolution in a whole-body MR system concurrently with regular system operation. The field observations serve as inputs to a proportional-integral controller that governs correction currents in gradient and higher-order shim coils such as to keep the field stable in a volume of interest. The feedback system was successfully set up, currently reaching a minimum latency of 20 ms. Its utility is first demonstrated by countering thermal field drift during an EPI protocol. It is then used to address respiratory field fluctuations in a T2 *-weighted brain exam, resulting in substantially improved image quality. Feedback field control is an effective means of eliminating dynamic field distortions in MR systems. Third-order spatial control at an update time of 100 ms has proven sufficient to largely eliminate thermal and breathing effects in brain imaging at 7 Tesla. © 2014 Wiley Periodicals, Inc.

Task-space sensory feedback control of robot manipulators

CERN Document Server

Cheah, Chien Chern

2015-01-01

This book presents recent advances in robot control theory on task space sensory feedback control of robot manipulators. By using sensory feedback information, the robot control systems are robust to various uncertainties in modelling and calibration errors of the sensors. Several sensory task space control methods that do not require exact knowledge of either kinematics or dynamics of robots, are presented. Some useful methods such as approximate Jacobian control, adaptive Jacobian control, region control and multiple task space regional feedback are included. These formulations and methods give robots a high degree of flexibility in dealing with unforeseen changes and uncertainties in its kinematics and dynamics, which is similar to human reaching movements and tool manipulation. It also leads to the solution of several long-standing problems and open issues in robot control, such as force control with constraint uncertainty, control of multi-fingered robot hand with uncertain contact points, singularity i...

Feedback control of nonlinear quantum systems: a rule of thumb.

Science.gov (United States)

Jacobs, Kurt; Lund, Austin P

2007-07-13

We show that in the regime in which feedback control is most effective - when measurements are relatively efficient, and feedback is relatively strong - then, in the absence of any sharp inhomogeneity in the noise, it is always best to measure in a basis that does not commute with the system density matrix than one that does. That is, it is optimal to make measurements that disturb the state one is attempting to stabilize.

ETSON proposal on the European operational experience feedback system

International Nuclear Information System (INIS)

Maqua, Michael; Bertrand, Remy; Gelder, Pieter de

2007-01-01

The new IAEA Safety Fundamentals states regarding the operating experience feedback: The feedback of operating experience from facilities and activities - and, where relevant, from elsewhere - is a key means of enhancing safety. Processes must be put in place for the feedback and analysis of operating experience, including initiating events, accident precursors, near misses, accidents and unauthorized acts, so that lessons may be learned, shared and acted upon. This presentation deals with the proposal of the ETSON (European TSO Network) to optimize the European operating experiences feedback (OEF). It is generally recognized that the efficiency of nuclear safety supervision by public authorities is based on two key requirements: - the existence of a competent authority at national level, benefiting from an appropriate legislative and regulatory basis, from adequate (quantitatively and qualitatively) human resources, particularly for inspection purposes, - the availability of resources devoted to highly specialised independent technical expertise, in order to provide competent authorities with pertinent technical opinions on: -- the safety files provided by operators, for the purpose of licensing corresponding activities, -- the exploitation for regulatory purposes of the operating experience feed back from licensed nuclear installations. There are two worldwide systems intended to learn lessons from experience: the WANO (World Association of Nuclear Operators) system established by the licensees with access restricted to operating organizations and the IRS system jointly operated by IAEA and OECD/NEA accessible to regulators and to some other users nominated by the regulators in their countries. The IRS itself is dedicated to the analysis of safety significant operating events. NEA/CNRA runs a permanent working group on operating experience (WGOE). WGOE provides among other things also generic reports on safety concerns related to operating experiences and

Low-noise and high-speed photodetection system using optical feedback with a current amplification function.

Science.gov (United States)

Akiba, M

2015-09-01

A photodetection system with an optical-feedback circuit accompanied by current amplification was fabricated to minimize the drawbacks associated with a transimpedance amplifier (TIA) with a very high resistance feedback resistor. Current amplification was implemented by extracting an output light from the same light source that emitted the feedback light. The current gain corresponds to the ratio of the photocurrent created by the output light to that created by the feedback light because the feedback current value is identical to the input photocurrent value generated by an input light to be measured. The current gain has no theoretical limit. The output light was detected by a photodiode with a TIA having a small feedback resistance. The expression for the input-referred noise current of the optical-feedback photodetection system was derived, and the trade-off between sensitivity and response, which is a characteristic of TIA, was found to considerably improve. An optical-feedback photodetection system with an InGaAs pin photodiode was fabricated. The measured noise equivalent power of the system was 1.7 fW/Hz(1/2) at 10 Hz and 1.3 μm, which is consistent with the derived expression. The time response of the system was found to deteriorate with decreasing photocurrent. The 50% rise time for a light pulse input increased from 3.1 μs at a photocurrent of 10 nA to 15 μs at photocurrents below 10 pA. The bandwidth of the input-referred noise current was 7 kHz, which is consistent with rise times below 10 pA.

Web/smart phone based control and feedback systems for irrigation systems

Science.gov (United States)

The role of the internet and mobile devices in the control and feedback of irrigation systems is reviewed. This role is placed in the larger context of four distinct components required for irrigation management, including 1. the control panel; 2. remote control; 3. soil, plant, and weather (SPW) se...

Finite-time stabilization of uncertain nonholonomic systems in feedforward-like form by output feedback.

Science.gov (United States)

Gao, Fangzheng; Wu, Yuqiang; Zhang, Zhongcai

2015-11-01

This paper investigates the problem of finite-time stabilization by output feedback for a class of nonholonomic systems in chained form with uncertainties. Comparing with the existing relevant literature, a distinguishing feature of the systems under investigation is that the x-subsystem is a feedforward-like rather than feedback-like system. This renders the existing control methods inapplicable to the control problems of the systems. A constructive design procedure for output feedback control is given. The designed controller renders that the states of closed-loop system are regulated to zero in a finite time. Two simulation examples are provided to illustrate the effectiveness of the proposed approach. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Adaptive H∞ synchronization of chaotic systems via linear and nonlinear feedback control

International Nuclear Information System (INIS)

Fu Shi-Hui; Lu Qi-Shao; Du Ying

2012-01-01

Adaptive H ∞ synchronization of chaotic systems via linear and nonlinear feedback control is investigated. The chaotic systems are redesigned by using the generalized Hamiltonian systems and observer approach. Based on Lyapunov's stability theory, linear and nonlinear feedback control of adaptive H ∞ synchronization is established in order to not only guarantee stable synchronization of both master and slave systems but also reduce the effect of external disturbance on an H ∞ -norm constraint. Adaptive H ∞ synchronization of chaotic systems via three kinds of control is investigated with applications to Lorenz and Chen systems. Numerical simulations are also given to identify the effectiveness of the theoretical analysis. (general)

Decentralized Feedback Controllers for Exponential Stabilization of Hybrid Periodic Orbits: Application to Robotic Walking*

Science.gov (United States)

Hamed, Kaveh Akbari; Gregg, Robert D.

2016-01-01

This paper presents a systematic algorithm to design time-invariant decentralized feedback controllers to exponentially stabilize periodic orbits for a class of hybrid dynamical systems arising from bipedal walking. The algorithm assumes a class of parameterized and nonlinear decentralized feedback controllers which coordinate lower-dimensional hybrid subsystems based on a common phasing variable. The exponential stabilization problem is translated into an iterative sequence of optimization problems involving bilinear and linear matrix inequalities, which can be easily solved with available software packages. A set of sufficient conditions for the convergence of the iterative algorithm to a stabilizing decentralized feedback control solution is presented. The power of the algorithm is demonstrated by designing a set of local nonlinear controllers that cooperatively produce stable walking for a 3D autonomous biped with 9 degrees of freedom, 3 degrees of underactuation, and a decentralization scheme motivated by amputee locomotion with a transpelvic prosthetic leg. PMID:27990059

Synchronization control of cross-strict feedback hyperchaotic system based on cross active backstepping design

International Nuclear Information System (INIS)

Wang Jing; Gao Jinfeng; Ma Xikui

2007-01-01

This Letter presents a novel cross active backstepping design method for synchronization control of cross-strict feedback hyperchaotic system, in which the ordinary backstepping design is unavailable. The proposed control method, combining backstepping design and active control approach, extends the application of backstepping technique in chaos control. Based on this method, different combinations of controllers can be designed to meet the needs of different applications. The proposed method is applied to achieve chaos synchronization of two identical cross-strict feedback hyperchaotic systems. Also it is used to implement synchronization between cross-strict feedback hyperchaotic system and Roessler hyperchaotic system. Numerical examples illustrate the validity of the control method

The Neural Feedback Response to Error As a Teaching Signal for the Motor Learning System

Science.gov (United States)

Shadmehr, Reza

2016-01-01

When we experience an error during a movement, we update our motor commands to partially correct for this error on the next trial. How does experience of error produce the improvement in the subsequent motor commands? During the course of an erroneous reaching movement, proprioceptive and visual sensory pathways not only sense the error, but also engage feedback mechanisms, resulting in corrective motor responses that continue until the hand arrives at its goal. One possibility is that this feedback response is co-opted by the learning system and used as a template to improve performance on the next attempt. Here we used electromyography (EMG) to compare neural correlates of learning and feedback to test the hypothesis that the feedback response to error acts as a template for learning. We designed a task in which mixtures of error-clamp and force-field perturbation trials were used to deconstruct EMG time courses into error-feedback and learning components. We observed that the error-feedback response was composed of excitation of some muscles, and inhibition of others, producing a complex activation/deactivation pattern during the reach. Despite this complexity, across muscles the learning response was consistently a scaled version of the error-feedback response, but shifted 125 ms earlier in time. Across people, individuals who produced a greater feedback response to error, also learned more from error. This suggests that the feedback response to error serves as a teaching signal for the brain. Individuals who learn faster have a better teacher in their feedback control system. SIGNIFICANCE STATEMENT Our sensory organs transduce errors in behavior. To improve performance, we must generate better motor commands. How does the nervous system transform an error in sensory coordinates into better motor commands in muscle coordinates? Here we show that when an error occurs during a movement, the reflexes transform the sensory representation of error into motor

Velocity Feedback Experiments

Directory of Open Access Journals (Sweden)

Chiu Choi

2017-02-01

Full Text Available Transient response such as ringing in a control system can be reduced or removed by velocity feedback. It is a useful control technique that should be covered in the relevant engineering laboratory courses. We developed velocity feedback experiments using two different low cost technologies, viz., operational amplifiers and microcontrollers. These experiments can be easily integrated into laboratory courses on feedback control systems or microcontroller applications. The intent of developing these experiments was to illustrate the ringing problem and to offer effective, low cost solutions for removing such problem. In this paper the pedagogical approach for these velocity feedback experiments was described. The advantages and disadvantages of the two different implementation of velocity feedback were discussed also.

Synthesis of human-nature feedbacks

Directory of Open Access Journals (Sweden)

Vanessa Hull

2015-09-01

Full Text Available In today's globalized world, humans and nature are inextricably linked. The coupled human and natural systems (CHANS framework provides a lens with which to understand such complex interactions. One of the central components of the CHANS framework involves examining feedbacks among human and natural systems, which form when effects from one system on another system feed back to affect the first system. Despite developments in understanding feedbacks in single disciplines, interdisciplinary research on CHANS feedbacks to date is scant and often site-specific, a shortcoming that prevents complex coupled systems from being fully understood. The special feature "Exploring Feedbacks in Coupled Human and Natural Systems (CHANS" makes strides to fill this critical gap. Here, as an introduction to the special feature, we provide an overview of CHANS feedbacks. In addition, we synthesize key CHANS feedbacks that emerged in the papers of this special feature across agricultural, forest, and urban landscapes. We also examine emerging themes explored across the papers, including multilevel feedbacks, time lags, and surprises as a result of feedbacks. We conclude with recommendations for future research that can build upon the foundation provided in the special feature.

Feedback controlled dephasing and population relaxation in a two-level system

International Nuclear Information System (INIS)

Wang Jin

2009-01-01

This Letter presents the maximum achievable stability and purity that can be obtained in a two-level system with both dephasing and population relaxation processes by using homodyne-mediated feedback control. An analytic formula giving the optimal amplitudes of the driving and feedback for the steady-state is also presented. Experimental examples are used to show the importance of controlling the dephasing process.

Equilibrium of a two-route system with delayed information feedback strategies

International Nuclear Information System (INIS)

Zhao, Xiao-mei; Xie, Dong-fan; Gao, Zi-you; Gao, Liang

2013-01-01

In intelligent transport system, some advanced information feedback strategies have been developed to reduce the oscillations and enhance the capacity on the road level. However, seldom strategies have considered the information delay and user equilibrium (UE) objective. Here, a derivative cost feedback strategy (DCFS) is proposed to reduce the influence of the delay, based on the UE principle. The simulation results show that in both no-delay and delay information cases, DCFS are the best and can make the system reaching the UE. Because DCFS can predict the trend of the travel cost.

Equilibrium of a two-route system with delayed information feedback strategies

Energy Technology Data Exchange (ETDEWEB)

Zhao, Xiao-mei, E-mail: xmzhao@bjtu.edu.cn [School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044 (China); MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, Beijing Jiaotong University, Beijing 100044 (China); Xie, Dong-fan, E-mail: dfxie@bjtu.edu.cn [School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044 (China); MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, Beijing Jiaotong University, Beijing 100044 (China); Gao, Zi-you, E-mail: zygao@bjtu.edu.cn [School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044 (China); MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, Beijing Jiaotong University, Beijing 100044 (China); Gao, Liang, E-mail: lianggao@bjtu.edu.cn [School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044 (China); MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, Beijing Jiaotong University, Beijing 100044 (China)

2013-12-09

In intelligent transport system, some advanced information feedback strategies have been developed to reduce the oscillations and enhance the capacity on the road level. However, seldom strategies have considered the information delay and user equilibrium (UE) objective. Here, a derivative cost feedback strategy (DCFS) is proposed to reduce the influence of the delay, based on the UE principle. The simulation results show that in both no-delay and delay information cases, DCFS are the best and can make the system reaching the UE. Because DCFS can predict the trend of the travel cost.

Finite-time output feedback stabilization of high-order uncertain nonlinear systems

Science.gov (United States)

Jiang, Meng-Meng; Xie, Xue-Jun; Zhang, Kemei

2018-06-01

This paper studies the problem of finite-time output feedback stabilization for a class of high-order nonlinear systems with the unknown output function and control coefficients. Under the weaker assumption that output function is only continuous, by using homogeneous domination method together with adding a power integrator method, introducing a new analysis method, the maximal open sector Ω of output function is given. As long as output function belongs to any closed sector included in Ω, an output feedback controller can be developed to guarantee global finite-time stability of the closed-loop system.

Feedback in Clinical Education, Part I: Characteristics of Feedback Provided by Approved Clinical Instructors

Science.gov (United States)

Nottingham, Sara; Henning, Jolene

2014-01-01

Context Providing students with feedback is an important component of athletic training clinical education; however, little information is known about the feedback that Approved Clinical Instructors (ACIs; now known as preceptors) currently provide to athletic training students (ATSs). Objective To characterize the feedback provided by ACIs to ATSs during clinical education experiences. Design Qualitative study. Setting One National Collegiate Athletic Association Division I athletic training facility and 1 outpatient rehabilitation clinic that were clinical sites for 1 entry-level master's degree program accredited by the Commission on Accreditation of Athletic Training Education. Patients or Other Participants A total of 4 ACIs with various experience levels and 4 second-year ATSs. Data Collection and Analysis Extensive field observations were audio recorded, transcribed, and integrated with field notes for analysis. The constant comparative approach of open, axial, and selective coding was used to inductively analyze data and develop codes and categories. Member checking, triangulation, and peer debriefing were used to promote trustworthiness of the study. Results The ACIs gave 88 feedback statements in 45 hours and 10 minutes of observation. Characteristics of feedback categories included purpose, timing, specificity, content, form, and privacy. Conclusions Feedback that ACIs provided included several components that made each feedback exchange unique. The ACIs in our study provided feedback that is supported by the literature, suggesting that ACIs are using current recommendations for providing feedback. Feedback needs to be investigated across multiple athletic training education programs to gain more understanding of certain areas of feedback, including frequency, privacy, and form. PMID:24143902

To what extent is feedback in teacher education ‘for learning’?

OpenAIRE

Carver, Mark

2016-01-01

Feedback for student teachers during their work-based learning in schools offers significant advantages over feedback in the university-based element of their degree programme. Students receive frequent, often immediate, feedback from an experienced teacher who sees their gradual development and has only a few students to manage. This includes formal feedback linked to assessment criteria but also opportunities for informal, verbal feedback and dialogue that supports socialisation as a collea...

ℋ∞ constant gain state feedback stabilization of stochastic hybrid systems with Wiener process

Directory of Open Access Journals (Sweden)

E. K. Boukas

2004-01-01

Full Text Available This paper considers the stabilization problem of the class of continuous-time linear stochastic hybrid systems with Wiener process. The ℋ∞ state feedback stabilization problem is treated. A state feedback controller with constant gain that does not require access to the system mode is designed. LMI-based conditions are developed to design the state feedback controller with constant gain that stochastically stabilizes the studied class of systems and, at the same time, achieve the disturbance rejection of a desired level. The minimum disturbance rejection is also determined. Numerical examples are given to show the usefulness of the proposed results.

Design and Implementation of Output Feedback Control for Piezo Actuated Structure Using Embedded System

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R.Maheswari

2008-06-01

Full Text Available This paper presents the design of periodic output feedback control using state feedback gain to control the vibration of piezo actuated cantilever beam. The effectiveness of the controller is evaluated through simulation and experimentally by exciting the structure at resonance. Real time implementation of the controller is done using microcontroller. The closed loop eigen values of the system with periodic output feedback and state feedback are identical.

Auditory display as feedback for a novel eye-tracking system for sterile operating room interaction.

Science.gov (United States)

Black, David; Unger, Michael; Fischer, Nele; Kikinis, Ron; Hahn, Horst; Neumuth, Thomas; Glaser, Bernhard

2018-01-01

The growing number of technical systems in the operating room has increased attention on developing touchless interaction methods for sterile conditions. However, touchless interaction paradigms lack the tactile feedback found in common input devices such as mice and keyboards. We propose a novel touchless eye-tracking interaction system with auditory display as a feedback method for completing typical operating room tasks. Auditory display provides feedback concerning the selected input into the eye-tracking system as well as a confirmation of the system response. An eye-tracking system with a novel auditory display using both earcons and parameter-mapping sonification was developed to allow touchless interaction for six typical scrub nurse tasks. An evaluation with novice participants compared auditory display with visual display with respect to reaction time and a series of subjective measures. When using auditory display to substitute for the lost tactile feedback during eye-tracking interaction, participants exhibit reduced reaction time compared to using visual-only display. In addition, the auditory feedback led to lower subjective workload and higher usefulness and system acceptance ratings. Due to the absence of tactile feedback for eye-tracking and other touchless interaction methods, auditory display is shown to be a useful and necessary addition to new interaction concepts for the sterile operating room, reducing reaction times while improving subjective measures, including usefulness, user satisfaction, and cognitive workload.

Degree counting and Shadow system for Toda system of rank two: One bubbling

Science.gov (United States)

Lee, Youngae; Lin, Chang-Shou; Wei, Juncheng; Yang, Wen

2018-04-01

We initiate the program for computing the Leray-Schauder topological degree for Toda systems of rank two. This program still contains a lot of challenging problems for analysts. As the first step, we prove that if a sequence of solutions (u1k ,u2k) blows up, then one of hje ujk/∫Mhje ujk dvg, j = 1 , 2 tends to a sum of Dirac measures. This is so-called the phenomena of weak concentration. Our purposes in this article are (i) to introduce the shadow system due to the bubbling phenomena when one of parameters ρi crosses 4π and ρj ∉ 4 πN where 1 ≤ i ≠ j ≤ 2; (ii) to show how to calculate the topological degree of Toda systems by computing the topological degree of the general shadow systems; (iii) to calculate the topological degree of the shadow system for one point blow up. We believe that the degree counting formula for the shadow system would be useful in other problems.

The super collider transverse feedback system for suppression of the emittance growth and beam instabilities

International Nuclear Information System (INIS)

Lebedev, V.A.

1993-01-01

A super collider transverse feedback system designed to suppress injection errors, emittance growth due to external noises, and beam instabilities is considered. It is supposed that the feedback system should consist of two circuits: an injection damper operating just after injection and a super damper. To damp the emittance growth, the superdamper has to operate with the ultimate decrement close to the revolution frequency. The physics of such a feedback system and its main limitations are discussed. 9 refs.; 21 figs.; 1 tab

Parameter identification technique for uncertain chaotic systems using state feedback and steady-state analysis.

Science.gov (United States)

Zaher, Ashraf A

2008-03-01

A technique is introduced for identifying uncertain and/or unknown parameters of chaotic dynamical systems via using simple state feedback. The proposed technique is based on bringing the system into a stable steady state and then solving for the unknown parameters using a simple algebraic method that requires access to the complete or partial states of the system depending on the dynamical model of the chaotic system. The choice of the state feedback is optimized in terms of practicality and causality via employing a single feedback signal and tuning the feedback gain to ensure both stability and identifiability. The case when only a single scalar time series of one of the states is available is also considered and it is demonstrated that a synchronization-based state observer can be augmented to the state feedback to address this problem. A detailed case study using the Lorenz system is used to exemplify the suggested technique. In addition, both the Rössler and Chua systems are examined as possible candidates for utilizing the proposed methodology when partial identification of the unknown parameters is considered. Finally, the dependence of the proposed technique on the structure of the chaotic dynamical model and the operating conditions is discussed and its advantages and limitations are highlighted via comparing it with other methods reported in the literature.

Design and test of a Microsoft Kinect-based system for delivering adaptive visual feedback to stroke patients during training of upper limb movement.

Science.gov (United States)

Simonsen, Daniel; Popovic, Mirjana B; Spaich, Erika G; Andersen, Ole Kæseler

2017-11-01

The present paper describes the design and test of a low-cost Microsoft Kinect-based system for delivering adaptive visual feedback to stroke patients during the execution of an upper limb exercise. Eleven sub-acute stroke patients with varying degrees of upper limb function were recruited. Each subject participated in a control session (repeated twice) and a feedback session (repeated twice). In each session, the subjects were presented with a rectangular pattern displayed on a vertical mounted monitor embedded in the table in front of the patient. The subjects were asked to move a marker inside the rectangular pattern by using their most affected hand. During the feedback session, the thickness of the rectangular pattern was changed according to the performance of the subject, and the color of the marker changed according to its position, thereby guiding the subject's movements. In the control session, the thickness of the rectangular pattern and the color of the marker did not change. The results showed that the movement similarity and smoothness was higher in the feedback session than in the control session while the duration of the movement was longer. The present study showed that adaptive visual feedback delivered by use of the Kinect sensor can increase the similarity and smoothness of upper limb movement in stroke patients.

Multipulse dynamics of a passively mode-locked semiconductor laser with delayed optical feedback

Science.gov (United States)

Jaurigue, Lina; Krauskopf, Bernd; Lüdge, Kathy

2017-11-01

Passively mode-locked semiconductor lasers are compact, inexpensive sources of short light pulses of high repetition rates. In this work, we investigate the dynamics and bifurcations arising in such a device under the influence of time delayed optical feedback. This laser system is modelled by a system of delay differential equations, which includes delay terms associated with the laser cavity and feedback loop. We make use of specialised path continuation software for delay differential equations to analyse the regime of short feedback delays. Specifically, we consider how the dynamics and bifurcations depend on the pump current of the laser, the feedback strength, and the feedback delay time. We show that an important role is played by resonances between the mode-locking frequencies and the feedback delay time. We find feedback-induced harmonic mode locking and show that a mismatch between the fundamental frequency of the laser and that of the feedback cavity can lead to multi-pulse or quasiperiodic dynamics. The quasiperiodic dynamics exhibit a slow modulation, on the time scale of the gain recovery rate, which results from a beating with the frequency introduced in the associated torus bifurcations and leads to gain competition between multiple pulse trains within the laser cavity. Our results also have implications for the case of large feedback delay times, where a complete bifurcation analysis is not practical. Namely, for increasing delay, there is an ever-increasing degree of multistability between mode-locked solutions due to the frequency pulling effect.

Prescribed Performance Fuzzy Adaptive Output-Feedback Control for Nonlinear Stochastic Systems

Directory of Open Access Journals (Sweden)

Lili Zhang

2014-01-01

Full Text Available A prescribed performance fuzzy adaptive output-feedback control approach is proposed for a class of single-input and single-output nonlinear stochastic systems with unmeasured states. Fuzzy logic systems are used to identify the unknown nonlinear system, and a fuzzy state observer is designed for estimating the unmeasured states. Based on the backstepping recursive design technique and the predefined performance technique, a new fuzzy adaptive output-feedback control method is developed. It is shown that all the signals of the resulting closed-loop system are bounded in probability and the tracking error remains an adjustable neighborhood of the origin with the prescribed performance bounds. A simulation example is provided to show the effectiveness of the proposed approach.

Robust broadband nanopositioning: fundamental trade-offs, analysis, and design in a two-degree-of-freedom control framework

International Nuclear Information System (INIS)

Lee, Chibum; Salapaka, Srinivasa M

2009-01-01

This paper studies and analyses fundamental trade-offs between positioning resolution, tracking bandwidth, and robustness to modeling uncertainties in two-degree-of-freedom (2DOF) control designs for nanopositioning systems. The analysis of these systems is done in optimal control setting with various architectural constraints imposed on the 2DOF framework. In terms of these trade-offs, our analysis shows that the primary role of feedback is providing robustness to the closed-loop device whereas the feedforward component is mainly effective in overcoming fundamental algebraic constraints that limit the feedback-only designs. This paper presents (1) an optimal prefilter model matching design for a system with an existing feedback controller, (2) a simultaneous feedforward and feedback control design in an optimal mixed sensitivity framework, and (3) a 2DOF optimal robust model matching design. The experimental results on applying these controllers show a significant improvement, as high as 330% increase in bandwidth for similar robustness and resolution over optimal feedback-only designs. Other performance objectives can be improved similarly. We demonstrate that the 2DOF freedom design achieves performance specifications that are analytically impossible for feedback-only designs.

Collective irrationality and positive feedback.

Science.gov (United States)

Nicolis, Stamatios C; Zabzina, Natalia; Latty, Tanya; Sumpter, David J T

2011-04-26

Recent experiments on ants and slime moulds have assessed the degree to which they make rational decisions when presented with a number of alternative food sources or shelter. Ants and slime moulds are just two examples of a wide range of species and biological processes that use positive feedback mechanisms to reach decisions. Here we use a generic, experimentally validated model of positive feedback between group members to show that the probability of taking the best of options depends crucially on the strength of feedback. We show how the probability of choosing the best option can be maximized by applying an optimal feedback strength. Importantly, this optimal value depends on the number of options, so that when we change the number of options the preference of the group changes, producing apparent "irrationalities". We thus reinterpret the idea that collectives show "rational" or "irrational" preferences as being a necessary consequence of the use of positive feedback. We argue that positive feedback is a heuristic which often produces fast and accurate group decision-making, but is always susceptible to apparent irrationality when studied under particular experimental conditions.

Collective irrationality and positive feedback.

Directory of Open Access Journals (Sweden)

Stamatios C Nicolis

Full Text Available Recent experiments on ants and slime moulds have assessed the degree to which they make rational decisions when presented with a number of alternative food sources or shelter. Ants and slime moulds are just two examples of a wide range of species and biological processes that use positive feedback mechanisms to reach decisions. Here we use a generic, experimentally validated model of positive feedback between group members to show that the probability of taking the best of options depends crucially on the strength of feedback. We show how the probability of choosing the best option can be maximized by applying an optimal feedback strength. Importantly, this optimal value depends on the number of options, so that when we change the number of options the preference of the group changes, producing apparent "irrationalities". We thus reinterpret the idea that collectives show "rational" or "irrational" preferences as being a necessary consequence of the use of positive feedback. We argue that positive feedback is a heuristic which often produces fast and accurate group decision-making, but is always susceptible to apparent irrationality when studied under particular experimental conditions.

Integrated regional changes in arctic climate feedbacks: Implications for the global climate system

Science.gov (United States)

McGuire, A.D.; Chapin, F. S.; Walsh, J.E.; Wirth, C.; ,

2006-01-01

The Arctic is a key part of the global climate system because the net positive energy input to the tropics must ultimately be resolved through substantial energy losses in high-latitude regions. The Arctic influences the global climate system through both positive and negative feedbacks that involve physical, ecological, and human systems of the Arctic. The balance of evidence suggests that positive feedbacks to global warming will likely dominate in the Arctic during the next 50 to 100 years. However, the negative feedbacks associated with changing the freshwater balance of the Arctic Ocean might abruptly launch the planet into another glacial period on longer timescales. In light of uncertainties and the vulnerabilities of the climate system to responses in the Arctic, it is important that we improve our understanding of how integrated regional changes in the Arctic will likely influence the evolution of the global climate system. Copyright ?? 2006 by Annual Reviews. All rights reserved.

Feedback as Real-Time Constructions

Science.gov (United States)

Keiding, Tina Bering; Qvortrup, Ane

2014-01-01

This article offers a re-description of feedback and the significance of time in feedback constructions based on systems theory. It describes feedback as internal, real-time constructions in a learning system. From this perspective, feedback is neither immediate nor delayed, but occurs in the very moment it takes place. This article argues for a…

Robust output feedback H-infinity control and filtering for uncertain linear systems

CERN Document Server

Chang, Xiao-Heng

2014-01-01

"Robust Output Feedback H-infinity Control and Filtering for Uncertain Linear Systems" discusses new and meaningful findings on robust output feedback H-infinity control and filtering for uncertain linear systems, presenting a number of useful and less conservative design results based on the linear matrix inequality (LMI) technique. Though primarily intended for graduate students in control and filtering, the book can also serve as a valuable reference work for researchers wishing to explore the area of robust H-infinity control and filtering of uncertain systems. Dr. Xiao-Heng Chang is a Professor at the College of Engineering, Bohai University, China.

Down sampled signal processing for a B Factory bunch-by-bunch feedback system

International Nuclear Information System (INIS)

Hindi, H.; Hosseini, W.; Briggs, D.; Fox, J.; Hutton, A.

1992-03-01

A bunch-by-bunch feedback scheme is studied for damping coupled bunch synchrotron oscillations in the proposed PEP II B Factory. The quasi-linear feedback systems design incorporates a phase detector to provide a quantized measure of bunch phase, digital signal processing to compute an error correction signal and a kicker system to correct the energy of the bunches. A farm of digital processors, operating in parallel, is proposed to compute correction signals for the 1658 bunches of the B Factory. This paper studies the use of down sampled processing to reduce the computational complexity of the feedback system. We present simulation results showing the effect of down sampling on beam dynamics. Results show that down sampled processing can reduce the scale of the processing task by a factor of 10

Global output feedback stabilisation of stochastic high-order feedforward nonlinear systems with time-delay

Science.gov (United States)

Zhang, Kemei; Zhao, Cong-Ran; Xie, Xue-Jun

2015-12-01

This paper considers the problem of output feedback stabilisation for stochastic high-order feedforward nonlinear systems with time-varying delay. By using the homogeneous domination theory and solving several troublesome obstacles in the design and analysis, an output feedback controller is constructed to drive the closed-loop system globally asymptotically stable in probability.

Design of a Haptic Feedback System for Flight Envelope Protection

NARCIS (Netherlands)

Van Baelen, D.; Ellerbroek, J.; van Paassen, M.M.; Mulder, M.

2018-01-01

Current Airbus aircraft use a fly-by-wire control device: a passive spring-damper system which generates, without any force feedback, an electrical signal to the flight control computer. Additionally, a hard flight envelope protection system is used which can limit the inputs of the pilot when

Modeling of low frequency dynamics of a smart system and its state feedback based active control

Science.gov (United States)

Kant, Mohit; Parameswaran, Arun P.

2018-01-01

Major physical systems/structures suffer from unwanted vibrations. For efficient working of such systems, these vibrations have to be controlled. In this paper, mathematical modeling of an aluminum cantilever beam with bonded multiple piezoelectric patches which act as the disturbance generator, sensor as well as control actuator has been presented. This piezoelectric laminate cantilever beam is assumed to be vibrating in a single degree of freedom i.e. in the flexural mode only and the corresponding state space models have been derived analytically using the finite element technique. Dominant modes of flexural vibration are identified from the frequency response of the developed model of the system and finally a state feedback controller based on pole placement technique is designed to actively suppress the vibrations. Through numerous simulations as well as experimental validation, the effectiveness of the active controller in damping the vibrations at various excitation frequencies as well as frequency ranges along the flexural mode is established.

Educators' Perceptions of Automated Feedback Systems

Science.gov (United States)

Debuse, Justin C. W.; Lawley, Meredith; Shibl, Rania

2008-01-01

Assessment of student learning is a core function of educators. Ideally students should be provided with timely, constructive feedback to facilitate learning. However, provision of high quality feedback becomes more complex as class sizes increase, modes of study expand and academic workloads increase. ICT solutions are being developed to…

Mean Velocity Prediction Information Feedback Strategy in Two-Route Systems under ATIS

Directory of Open Access Journals (Sweden)

Jianqiang Wang

2015-02-01

Full Text Available Feedback contents of previous information feedback strategies in advanced traveler information systems are almost real-time traffic information. Compared with real-time information, prediction traffic information obtained by a reliable and effective prediction algorithm has many undisputable advantages. In prediction information environment, a traveler is prone to making a more rational route-choice. For these considerations, a mean velocity prediction information feedback strategy (MVPFS is presented. The approach adopts the autoregressive-integrated moving average model (ARIMA to forecast short-term traffic flow. Furthermore, prediction results of mean velocity are taken as feedback contents and displayed on a variable message sign to guide travelers' route-choice. Meanwhile, discrete choice model (Logit model is selected to imitate more appropriately travelers' route-choice behavior. In order to investigate the performance of MVPFS, a cellular automaton model with ARIMA is adopted to simulate a two-route scenario. The simulation shows that such innovative prediction feedback strategy is feasible and efficient. Even more importantly, this study demonstrates the excellence of prediction feedback ideology.

Improvement of density control by feedback on Langmuir probe signals in Tore Supra

International Nuclear Information System (INIS)

Gunn, J.; Bucalossi, J.; Costanzo, L.; Grisolia, C.; Ghendrih, Ph.; Grosman, A.; Loarer, T.; Martin, G.; Monier-Garbet, P.; Moulin, D.; Pascal, J.Y.; Saint-Laurent, F.

1999-12-01

Real time control of deuterium or helium gas injection by feedback on Langmuir probe signals is implemented in Tore Supra ergodic divertor discharges. The feedback schemes are based on the robust experimental observation that the density limit coincides with edge temperature T e ∼ 10 eV. Three control algorithms are used: (1) proportional feedback on the central line-averaged density with real-time attenuation of the system gain and security cut-off of the gas injection if the edge temperature becomes too low; (2) proportional feedback on the central line-averaged density with security cut-off controlled by the degree of detachment (DoD); (3) proportional feedback on edge temperature with security cut-off on the DoD. The DoD is defined for deuterium discharges, but not for helium since those do not detach. All three feedback modes permit operation close to the density limit and have been successfully applied for plasma currents 0.4 p p =1.4 MA with up to 4 MW of ICRH power. (author)

Comparison of Multiple-Microphone and Single-Loudspeaker Adaptive Feedback/Echo Cancellation Systems

DEFF Research Database (Denmark)

Guo, Meng; Elmedyb, Thomas Bo; Jensen, Søren Holdt

2011-01-01

Recently, we introduced a frequency domain measure - the power transfer function - to predict the convergence rate, system stability bound and the steady-state behavior across time and frequency of a least mean square based feedback/echo cancellation algorithm in a general multiple-microphone and......Recently, we introduced a frequency domain measure - the power transfer function - to predict the convergence rate, system stability bound and the steady-state behavior across time and frequency of a least mean square based feedback/echo cancellation algorithm in a general multiple...

Depression as a systemic syndrome: mapping the feedback loops of major depressive disorder.

Science.gov (United States)

Wittenborn, A K; Rahmandad, H; Rick, J; Hosseinichimeh, N

2016-02-01

Depression is a complex public health problem with considerable variation in treatment response. The systemic complexity of depression, or the feedback processes among diverse drivers of the disorder, contribute to the persistence of depression. This paper extends prior attempts to understand the complex causal feedback mechanisms that underlie depression by presenting the first broad boundary causal loop diagram of depression dynamics. We applied qualitative system dynamics methods to map the broad feedback mechanisms of depression. We used a structured approach to identify candidate causal mechanisms of depression in the literature. We assessed the strength of empirical support for each mechanism and prioritized those with support from validation studies. Through an iterative process, we synthesized the empirical literature and created a conceptual model of major depressive disorder. The literature review and synthesis resulted in the development of the first causal loop diagram of reinforcing feedback processes of depression. It proposes candidate drivers of illness, or inertial factors, and their temporal functioning, as well as the interactions among drivers of depression. The final causal loop diagram defines 13 key reinforcing feedback loops that involve nine candidate drivers of depression. Future research is needed to expand upon this initial model of depression dynamics. Quantitative extensions may result in a better understanding of the systemic syndrome of depression and contribute to personalized methods of evaluation, prevention and intervention.

Automatic lung segmentation using control feedback system: morphology and texture paradigm.

Science.gov (United States)

Noor, Norliza M; Than, Joel C M; Rijal, Omar M; Kassim, Rosminah M; Yunus, Ashari; Zeki, Amir A; Anzidei, Michele; Saba, Luca; Suri, Jasjit S

2015-03-01

Interstitial Lung Disease (ILD) encompasses a wide array of diseases that share some common radiologic characteristics. When diagnosing such diseases, radiologists can be affected by heavy workload and fatigue thus decreasing diagnostic accuracy. Automatic segmentation is the first step in implementing a Computer Aided Diagnosis (CAD) that will help radiologists to improve diagnostic accuracy thereby reducing manual interpretation. Automatic segmentation proposed uses an initial thresholding and morphology based segmentation coupled with feedback that detects large deviations with a corrective segmentation. This feedback is analogous to a control system which allows detection of abnormal or severe lung disease and provides a feedback to an online segmentation improving the overall performance of the system. This feedback system encompasses a texture paradigm. In this study we studied 48 males and 48 female patients consisting of 15 normal and 81 abnormal patients. A senior radiologist chose the five levels needed for ILD diagnosis. The results of segmentation were displayed by showing the comparison of the automated and ground truth boundaries (courtesy of ImgTracer™ 1.0, AtheroPoint™ LLC, Roseville, CA, USA). The left lung's performance of segmentation was 96.52% for Jaccard Index and 98.21% for Dice Similarity, 0.61 mm for Polyline Distance Metric (PDM), -1.15% for Relative Area Error and 4.09% Area Overlap Error. The right lung's performance of segmentation was 97.24% for Jaccard Index, 98.58% for Dice Similarity, 0.61 mm for PDM, -0.03% for Relative Area Error and 3.53% for Area Overlap Error. The segmentation overall has an overall similarity of 98.4%. The segmentation proposed is an accurate and fully automated system.

Load speed regulation in compliant mechanical transmission systems using feedback and feedforward control actions.

Science.gov (United States)

Raul, P R; Dwivedula, R V; Pagilla, P R

2016-07-01

The problem of controlling the load speed of a mechanical transmission system consisting of a belt-pulley and gear-pair is considered. The system is modeled as two inertia (motor and load) connected by a compliant transmission. If the transmission is assumed to be rigid, then using either the motor or load speed feedback provides the same result. However, with transmission compliance, due to belts or long shafts, the stability characteristics and performance of the closed-loop system are quite different when either motor or load speed feedback is employed. We investigate motor and load speed feedback schemes by utilizing the singular perturbation method. We propose and discuss a control scheme that utilizes both motor and load speed feedback, and design an adaptive feedforward action to reject load torque disturbances. The control algorithms are implemented on an experimental platform that is typically used in roll-to-roll manufacturing and results are shown and discussed. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Stereo camera based virtual cane system with identifiable distance tactile feedback for the blind.

Science.gov (United States)

Kim, Donghun; Kim, Kwangtaek; Lee, Sangyoun

2014-06-13

In this paper, we propose a new haptic-assisted virtual cane system operated by a simple finger pointing gesture. The system is developed by two stages: development of visual information delivery assistant (VIDA) with a stereo camera and adding a tactile feedback interface with dual actuators for guidance and distance feedbacks. In the first stage, user's pointing finger is automatically detected using color and disparity data from stereo images and then a 3D pointing direction of the finger is estimated with its geometric and textural features. Finally, any object within the estimated pointing trajectory in 3D space is detected and the distance is then estimated in real time. For the second stage, identifiable tactile signals are designed through a series of identification experiments, and an identifiable tactile feedback interface is developed and integrated into the VIDA system. Our approach differs in that navigation guidance is provided by a simple finger pointing gesture and tactile distance feedbacks are perfectly identifiable to the blind.

Effects of stochastic time-delayed feedback on a dynamical system modeling a chemical oscillator

Science.gov (United States)

González Ochoa, Héctor O.; Perales, Gualberto Solís; Epstein, Irving R.; Femat, Ricardo

2018-05-01

We examine how stochastic time-delayed negative feedback affects the dynamical behavior of a model oscillatory reaction. We apply constant and stochastic time-delayed negative feedbacks to a point Field-Körös-Noyes photosensitive oscillator and compare their effects. Negative feedback is applied in the form of simulated inhibitory electromagnetic radiation with an intensity proportional to the concentration of oxidized light-sensitive catalyst in the oscillator. We first characterize the system under nondelayed inhibitory feedback; then we explore and compare the effects of constant (deterministic) versus stochastic time-delayed feedback. We find that the oscillatory amplitude, frequency, and waveform are essentially preserved when low-dispersion stochastic delayed feedback is used, whereas small but measurable changes appear when a large dispersion is applied.

Work in Progress - Developing Joint Degrees through E-Learning Systems

OpenAIRE

Aguirre Herrera, Sandra; Quemada Vives, Juan; Salvachúa Rodríguez, Joaquín

2008-01-01

The development of Joint Degrees is an important mechanism for opening higher education systems nationwide, adapting them to the international standard, and promoting quality assessment to a broader environment. Since e-Learning systems covers a wide range of academic programs, and as joint degrees such as e-Learning are rapidly growing trends, finding a suitable solution that enables universities to design joint degrees through their own e-Learning systems becomes necessary. This paper intro...

An active feedback system to control synchrotron oscillations in the SLC Damping Rings

International Nuclear Information System (INIS)

Corredoura, P.L.; Pellegrin, J.L.; Schwarz, H.D.; Sheppard, J.C.

1989-03-01

Initially the SLC Damping Rings accomplished Robinson instability damping by operating the RF accelerating cavities slightly detuned. In order to be able to run the cavities tuned and achieve damping for Robinson instability and synchrotron oscillations at injection an active feedback system has been developed. This paper describes the theoretical basis for the feedback system and the development of the hardware. Extensive measurements of the loop response including stored beam were performed. Overall performance of the system is also reported. 3 refs., 6 figs

General, database-driven fast-feedback system for the Stanford Linear Collider

International Nuclear Information System (INIS)

Rouse, F.; Allison, S.; Castillo, S.; Gromme, T.; Hall, B.; Hendrickson, L.; Himel, T.; Krauter, K.; Sass, B.; Shoaee, H.

1991-05-01

A new feedback system has been developed for stabilizing the SLC beams at many locations. The feedback loops are designed to sample and correct at the 60 Hz repetition rate of the accelerator. Each loop can be distributed across several of the standard 80386 microprocessors which control the SLC hardware. A new communications system, KISNet, has been implemented to pass signals between the microprocessors at this rate. The software is written in a general fashion using the state space formalism of digital control theory. This allows a new loop to be implemented by just setting up the online database and perhaps installing a communications link. 3 refs., 4 figs

A high precision dual feedback discrete control system designed for satellite trajectory simulator

Science.gov (United States)

Liu, Ximin; Liu, Liren; Sun, Jianfeng; Xu, Nan

2005-08-01

Cooperating with the free-space laser communication terminals, the satellite trajectory simulator is used to test the acquisition, pointing, tracking and communicating performances of the terminals. So the satellite trajectory simulator plays an important role in terminal ground test and verification. Using the double-prism, Sun etc in our group designed a satellite trajectory simulator. In this paper, a high precision dual feedback discrete control system designed for the simulator is given and a digital fabrication of the simulator is made correspondingly. In the dual feedback discrete control system, Proportional- Integral controller is used in velocity feedback loop and Proportional- Integral- Derivative controller is used in position feedback loop. In the controller design, simplex method is introduced and an improvement to the method is made. According to the transfer function of the control system in Z domain, the digital fabrication of the simulator is given when it is exposed to mechanism error and moment disturbance. Typically, when the mechanism error is 100urad, the residual standard error of pitching angle, azimuth angle, x-coordinate position and y-coordinate position are 0.49urad, 6.12urad, 4.56urad, 4.09urad respectively. When the moment disturbance is 0.1rad, the residual standard error of pitching angle, azimuth angle, x-coordinate position and y-coordinate position are 0.26urad, 0.22urad, 0.16urad, 0.15urad respectively. The digital fabrication results demonstrate that the dual feedback discrete control system designed for the simulator can achieve the anticipated high precision performance.

How Are Feedbacks Represented in Land Models?

Directory of Open Access Journals (Sweden)

Yang Chen

2016-09-01

Full Text Available Land systems are characterised by many feedbacks that can result in complex system behaviour. We defined feedbacks as the two-way influences between the land use system and a related system (e.g., climate, soils and markets, both of which are encompassed by the land system. Land models that include feedbacks thus probably more accurately mimic how land systems respond to, e.g., policy or climate change. However, representing feedbacks in land models is a challenge. We reviewed articles incorporating feedbacks into land models and analysed each with predefined indicators. We found that (1 most modelled feedbacks couple land use systems with transport, soil and market systems, while only a few include feedbacks between land use and social systems or climate systems; (2 equation-based land use models that follow a top-down approach prevail; and (3 feedbacks’ effects on system behaviour remain relatively unexplored. We recommend that land system modellers (1 consider feedbacks between land use systems and social systems; (2 adopt (bottom-up approaches suited to incorporating spatial heterogeneity and better representing land use decision-making; and (3 pay more attention to nonlinear system behaviour and its implications for land system management and policy.

Lectures in feedback design for multivariable systems

CERN Document Server

Isidori, Alberto

2017-01-01

This book focuses on methods that relate, in one form or another, to the “small-gain theorem”. It is aimed at readers who are interested in learning methods for the design of feedback laws for linear and nonlinear multivariable systems in the presence of model uncertainties. With worked examples throughout, it includes both introductory material and more advanced topics. Divided into two parts, the first covers relevant aspects of linear-systems theory, the second, nonlinear theory. In order to deepen readers’ understanding, simpler single-input–single-output systems generally precede treatment of more complex multi-input–multi-output (MIMO) systems and linear systems precede nonlinear systems. This approach is used throughout, including in the final chapters, which explain the latest advanced ideas governing the stabilization, regulation, and tracking of nonlinear MIMO systems. Two major design problems are considered, both in the presence of model uncertainties: asymptotic stabilization with a “...

Architecture of the APS real-time orbit feedback system

International Nuclear Information System (INIS)

Carwardine, J. A.; Lenkszus, F. R.

1997-01-01

The APS Real-Time Orbit Feedback System is designed to stabilize the orbit of the stored positron beam against low-frequency sources such as mechanical vibration and power supply ripple. A distributed array of digital signal processors is used to measure the orbit and compute corrections at a 1kHz rate. The system also provides extensive beam diagnostic tools. This paper describes the architectural aspects of the system and describes how the orbit correction algorithms are implemented

Architecture of the APS real-time orbit feedback system.

Energy Technology Data Exchange (ETDEWEB)

Carwardine, J. A.; Lenkszus, F. R.

1997-11-21

The APS Real-Time Orbit Feedback System is designed to stabilize the orbit of the stored positron beam against low-frequency sources such as mechanical vibration and power supply ripple. A distributed array of digital signal processors is used to measure the orbit and compute corrections at a 1kHz rate. The system also provides extensive beam diagnostic tools. This paper describes the architectural aspects of the system and describes how the orbit correction algorithms are implemented.

Terrestrial biogeochemical feedbacks in the climate system: from past to future

Energy Technology Data Exchange (ETDEWEB)

Arneth, A.; Harrison, S. P.; Zaehle, S.; Tsigaridis, K; Menon, S; Bartlein, P.J.; Feichter, J; Korhola, A; Kulmala, M; O' Donnell, D; Schurgers, G; Sorvari, S; Vesala, T

2010-01-05

The terrestrial biosphere plays a major role in the regulation of atmospheric composition, and hence climate, through multiple interlinked biogeochemical cycles (BGC). Ice-core and other palaeoenvironmental records show a fast response of vegetation cover and exchanges with the atmosphere to past climate change, although the phasing of these responses reflects spatial patterning and complex interactions between individual biospheric feedbacks. Modern observations show a similar responsiveness of terrestrial biogeochemical cycles to anthropogenically-forced climate changes and air pollution, with equally complex feedbacks. For future conditions, although carbon cycle-climate interactions have been a major focus, other BGC feedbacks could be as important in modulating climate changes. The additional radiative forcing from terrestrial BGC feedbacks other than those conventionally attributed to the carbon cycle is in the range of 0.6 to 1.6 Wm{sup -2}; all taken together we estimate a possible maximum of around 3 Wm{sup -2} towards the end of the 21st century. There are large uncertainties associated with these estimates but, given that the majority of BGC feedbacks result in a positive forcing because of the fundamental link between metabolic stimulation and increasing temperature, improved quantification of these feedbacks and their incorporation in earth system models is necessary in order to develop coherent plans to manage ecosystems for climate mitigation.

Numerical Simulation of the Oscillations in a Mixer: An Internal Aeroacoustic Feedback System

Science.gov (United States)

Jorgenson, Philip C. E.; Loh, Ching Y.

2004-01-01

The space-time conservation element and solution element method is employed to numerically study the acoustic feedback system in a high temperature, high speed wind tunnel mixer. The computation captures the self-sustained feedback loop between reflecting Mach waves and the shear layer. This feedback loop results in violent instabilities that are suspected of causing damage to some tunnel components. The computed frequency is in good agreement with the available experimental data. The physical phenomena are explained based on the numerical results.

Design and implementation of remote robotic control system for nuclear power plant application achieved through kinesthetic force feedback model

International Nuclear Information System (INIS)

Roy, D.

1995-01-01

The technology of telerobotic control through a universal and transparent Man-Machine Interface is a growing field of robotics research in today's industrial scenario because of its promising application in hazardous and unstructured environments. The joystick, a sophisticated information receiver-translator-transmitter device, serves as a Man-Machine Interface for telerobots. The present paper describes the development paradigms of a remote control system for a planar four degrees-of-freedom joystick following position feed-forward force/torque feedback strategy in a bi-lateral mode. This joystick based control technology is designed to actuate an industrial robot working in nuclear power plant. The remote control system has been illustrated with model, algorithm, electronic hardware and software routines along with experimental results in order to have effective telemanipulation

The FONT5 Bunch-by-Bunch Position and Angle Feedback System at ATF2

Science.gov (United States)

Apsimon, R. J.; Bett, D. R.; Burrows, P. N.; Christian, G. B.; Constance, B.; Davis, M. R.; Gerbershagen, A.; Perry, C.; Resta-Lopez, J.

The FONT5 upstream beam-based feedback system at ATF2 is designed to correct the position and angle jitter at the entrance to the ATF2 final-focus system, and also to demonstrate a prototype intra-train feedback system for the International Linear Collider interaction point. We discuss the hardware, from stripline BPMs to kickers, and RF and digital signal processing, as well as presenting results from the latest beam tests at ATF2.

Fast feedback for linear colliders

International Nuclear Information System (INIS)

Hendrickson, L.; Adolphsen, C.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Minty, M.; Sass, R.

1995-01-01

A fast feedback system provides beam stabilization for the SLC. As the SLC is in some sense a prototype for future linear colliders, this system may be a prototype for future feedbacks. The SLC provides a good base of experience for feedback requirements and capabilities as well as a testing ground for performance characteristics. The feedback system controls a wide variety of machine parameters throughout the SLC and associated experiments, including regulation of beam position, angle, energy, intensity and timing parameters. The design and applications of the system are described, in addition to results of recent performance studies

Haptic feedback designs in teleoperation systems for minimal invasive surgery

NARCIS (Netherlands)

Font, I.; Weiland, S.; Franken, M.; Steinbuch, M.; Rovers, A.F.

2004-01-01

One of the major shortcomings of state-of-the-art robotic systems for minimal invasive surgery is the lack of haptic feedback for the surgeon. In order to provide haptic information, sensors and actuators have to be added to the master and slave device. A control system should process the data and

A method for calculating active feedback system to provide vertical ...

Indian Academy of Sciences (India)

Slow instabilities, development time of which is proportional to the .... where (w, I) denotes the scalar (inner or dot) product of vectors w and I. Solutions ... which the system of passive conductors must satisfy. ..... In this research, the active feedback system consisting of two coils with coordi- .... a new mode becomes dominant.

Feedback control of coupled-bunch instabilities

International Nuclear Information System (INIS)

Fox, J.D.; Eisen, N.; Hindi, H.; Linscott, I.; Oxoby, G.; Sapozhnikov, L.; Serio, M.

1993-05-01

The next generation of synchrotron light sources and particle accelerators will require active feedback systems to control multi-bunch instabilities. Stabilizing hundreds or thousands of potentially unstable modes in these accelerator designs presents many technical challenges. Feedback systems to stabilize coupled-bunch instabilities may be understood in the frequency domain (mode-based feedback) or in the time domain (bunch-by-bunch feedback). In both approaches an external amplifier system is used to create damping fields that prevent coupled-bunch oscillations from growing without bound. The system requirements for transverse (betatron) and longitudinal (synchrotron) feedback are presented, and possible implementation options developed. Feedback system designs based on digital signal-processing techniques are described. Experimental results are shown from a synchrotron oscillation damper in the SSRL/SLAC storage ring SPEAR that uses digital signal-processing techniques

Feedback in LT codes for prioritized and non-prioritized data

DEFF Research Database (Denmark)

Sørensen, Jesper Hemming; Popovski, Petar; Østergaard, Jan

2012-01-01

In this paper feedback in LT codes is investigated. The considered type of feedback is acknowledgments, where information on which symbols have been decoded is given to the transmitter. Our analysis reveals that acknowledgments has a very low potential in LT codes with standard degree distributions....... Motivated by this, we analyze the impact of acknowledgments on multi-layer LT codes. In this case, feedback proves advantageous. By using only a single feedback message, it is possible to achieve a significant performance improvement compared to traditional LT codes....

Design of the ALS transverse coupled-bunch feedback system

International Nuclear Information System (INIS)

Barry, W.; Byrd, J.M.; Corlett, J.N.; Hinkson, J.; Johnson, J.; Lambertson, G.R.; Fox, J.D.

1993-05-01

Calculations of transverse coupled bunch growth rates in the Advanced Light Source (ALS), a 1.5 GeV electron storage ring for producing synchrotron radiation, indicate the need for damping via a transverse feedback (TFB) system. We present the design of such a system. The maximum bunch frequency is 500 MHz, requiring that the FB system have a broadband response of at least 250 MHz. We described, in detail, the choice of broadband components such as kickers, pickups, power amplifiers, and electronics

Evaluation of State-of-the-Art Acoustic Feedback Cancellation Systems for Hearing Aids

DEFF Research Database (Denmark)

Guo, Meng; Jensen, Søren Holdt; Jensen, Jesper

2013-01-01

This research evaluates four state-of-the-art acoustic feedback cancellation systems in hearing aids in terms of the cancellation performance, sound quality degradation, and computational complexity. The authors compared a traditional full-band system to a system with a prediction error method...... in a full band, a subband system, a subband system with frequency shifting, and a recently proposed subband system with a novel probe noise deployment. All systems outperformed the traditional full-band system in cancellation performance, especially the subband system with probe noise is most effective...... for cancellation. However, in all cases there was a trade-off between performance and computational cost. With a 3-times increase in computation load, the probe noise based cancellation system can be realized that functions even in the most challenging feedback situation....

Climate-society feedbacks and the avoidance of dangerous climate change

Science.gov (United States)

Jarvis, A. J.; Leedal, D. T.; Hewitt, C. N.

2012-09-01

The growth in anthropogenic CO2 emissions experienced since the onset of the Industrial Revolution is the most important disturbance operating on the Earth's climate system. To avoid dangerous climate change, future greenhouse-gas emissions will have to deviate from business-as-usual trajectories. This implies that feedback links need to exist between climate change and societal actions. Here, we show that, consciously or otherwise, these feedbacks can be represented by linking global mean temperature change to the growth dynamics of CO2 emissions. We show that the global growth of new renewable sources of energy post-1990 represents a climate-society feedback of ~0.25%yr-1 per degree increase in global mean temperature. We also show that to fulfil the outcomes negotiated in Durban in 2011, society will have to become ~ 50 times more responsive to global mean temperature change than it has been since 1990. If global energy use continues to grow as it has done historically then this would result in amplification of the long-term endogenous rate of decarbonization from -0.6%yr-1 to ~-13%yr-1. It is apparent that modest levels of feedback sensitivity pay large dividends in avoiding climate change but that the marginal return on this effort diminishes rapidly as the required feedback strength increases.

Within-step modulation of leg muscles activity by afferent feedback in human walking

DEFF Research Database (Denmark)

Klint, Richard af; Nielsen, Jens Bo; Cole, Jonathan D.

2008-01-01

To maintain smooth and efficient gait the motor system must adjust for changes in the ground on a step-to-step basis. In the present study we investigated the role of sensory feedback as 19 able-bodied human subjects walked over a platform that mimicked an uneven supporting surface. Triceps surae.......153+/-0.051; 3 degrees : 0.156+/-0.053) and significantly decreased when the platform was declined (-3 degrees : 0.133+/-0.048; -2 degrees : 0.132+/-0.049) compared with level walking (0.141+/-0.048) for the able-bodied subjects. A similar experiment was performed with a subject who lacked proprioception...

Stereo Camera Based Virtual Cane System with Identifiable Distance Tactile Feedback for the Blind

Directory of Open Access Journals (Sweden)

Donghun Kim

2014-06-01

Full Text Available In this paper, we propose a new haptic-assisted virtual cane system operated by a simple finger pointing gesture. The system is developed by two stages: development of visual information delivery assistant (VIDA with a stereo camera and adding a tactile feedback interface with dual actuators for guidance and distance feedbacks. In the first stage, user’s pointing finger is automatically detected using color and disparity data from stereo images and then a 3D pointing direction of the finger is estimated with its geometric and textural features. Finally, any object within the estimated pointing trajectory in 3D space is detected and the distance is then estimated in real time. For the second stage, identifiable tactile signals are designed through a series of identification experiments, and an identifiable tactile feedback interface is developed and integrated into the VIDA system. Our approach differs in that navigation guidance is provided by a simple finger pointing gesture and tactile distance feedbacks are perfectly identifiable to the blind.

A New Feedback-Analysis based Reputation Algorithm for E-Commerce Communities

Directory of Open Access Journals (Sweden)

Hasnae Rahimi

2014-12-01

Full Text Available Dealing with the ever-growing content generated by users in the e-commerce applications, Trust Reputation Systems (TRS are widely used online to provide the trust reputation of each product using the customers’ ratings. However, there is also a good number of online customer reviews and feedback that must be used by the TRS. As a result, we propose in this work a new architecture for TRS in e-commerce application which includes feedback’ mining in order to calculate reputation scores. This architecture is based on an intelligent layer that proposes to each user (i.e. “feedback provider” who has already given his recommendation, a collection of prefabricated feedback to like or dislike. Then the proposed reputation algorithm calculates the trust degree of the user, the feedback’s trustworthiness and generates the global reputation score of the product according to his ‘likes’ and ‘dislikes’. In this work, we present also a state of the art of text mining tools and algorithms that can be used to generate the prefabricated feedback and to classify them into different categories.

Fuzzy combination of fuzzy and switching state-feedback controllers for nonlinear systems subject to parameter uncertainties.

Science.gov (United States)

Lam, H K; Leung, Frank H F

2005-04-01

This paper presents a fuzzy controller, which involves a fuzzy combination of local fuzzy and global switching state-feedback controllers, for nonlinear systems subject to parameter uncertainties with known bounds. The nonlinear system is represented by a fuzzy combined Takagi-Sugeno-Kang model, which is a fuzzy combination of the global and local fuzzy plant models. By combining the local fuzzy and global switching state-feedback controllers using fuzzy logic techniques, the advantages of both controllers can be retained and the undesirable chattering effect introduced by the global switching state-feedback controller can be eliminated. The steady-state error introduced by the global switching state-feedback controller when a saturation function is used can also be removed. Stability conditions, which are related to the system matrices of the local and global closed-loop systems, are derived to guarantee the closed-loop system stability. An application example will be given to demonstrate the merits of the proposed approach.

TFTR plasma feedback systems

International Nuclear Information System (INIS)

Efthimion, P.; Hawryluk, R.J.; Hojsak, W.; Marsala, R.J.; Mueller, D.; Rauch, W.; Tait, G.D.; Taylor, G.; Thompson, M.

1985-01-01

The Tokamak Fusion Test Reactor employs feedback control systems for four plasma parameters, i.e. for plasma current, for plasma major radius, for plasma vertical position, and for plasma density. The plasma current is controlled by adjusting the rate of change of current in the Ohmic Heating (OH) coil system. Plasma current is continuously sensed by a Rogowski coil and its associated electronics; the error between it and a preprogrammed reference plasma current history is operated upon by a ''proportional-plusintegral-plus-derivative'' (PID) control algorithm and combined with various feedforward terms, to generate compensating commands to the phase-controlled thyristor rectifiers which drive current through the OH coils. The plasma position is controlled by adjusting the currents in Equilibrium Field and Horizontal Field coil systems, which respectively determine the vertical and radial external magnetic fields producing J X B forces on the plasma current. The plasma major radius position and vertical position, sensed by ''B /sub theta/ '' and ''B /sub rho/ '' magnetic flux pickup coils with their associated electronics, are controlled toward preprogrammed reference histories by allowing PID and feedforward control algorithms to generate commands to the EF and HF coil power supplies. Plasma density is controlled by adjusting the amount of gas injected into the vacuum vessel. Time-varying gains are used to combine lineaveraged plasma density measurements from a microwave interferometer plasma diagnostic system with vacuum vessel pressure measurements from ion gauges, with various other measurements, and with preprogrammed reference histories, to determine commands to piezoelectric gas injection valves

Chaos synchronization in autonomous chaotic system via hybrid feedback control

International Nuclear Information System (INIS)

Yang Lixin; Chu Yandong; Zhang Jiangang; Li Xianfeng; Chang Yingxiang

2009-01-01

This paper presents the synchronization of chaos by designing united controller. First, this method is implemented in synchronization of a simple system, then we realize the synchronization of Lue hyperchaotic system, we also take tracking control to realize the synchronization of Lue hyperchaotic system. Comparing with results, we can find that hybrid feedback control approach is more effective than tracking control for hyperchaotic system. Numerical simulations show the united synchronization method works well.

State-feedback control of fuzzy discrete-event systems.

Science.gov (United States)

Lin, Feng; Ying, Hao

2010-06-01

In a 2002 paper, we combined fuzzy logic with discrete-event systems (DESs) and established an automaton model of fuzzy DESs (FDESs). The model can effectively represent deterministic uncertainties and vagueness, as well as human subjective observation and judgment inherent to many real-world problems, particularly those in biomedicine. We also investigated optimal control of FDESs and applied the results to optimize HIV/AIDS treatments for individual patients. Since then, other researchers have investigated supervisory control problems in FDESs, and several results have been obtained. These results are mostly derived by extending the traditional supervisory control of (crisp) DESs, which are string based. In this paper, we develop state-feedback control of FDESs that is different from the supervisory control extensions. We use state space to describe the system behaviors and use state feedback in control. Both disablement and enforcement are allowed. Furthermore, we study controllability based on the state space and prove that a controller exists if and only if the controlled system behavior is (state-based) controllable. We discuss various properties of the state-based controllability. Aside from novelty, the proposed new framework has the advantages of being able to address a wide range of practical problems that cannot be effectively dealt with by existing approaches. We use the diabetes treatment as an example to illustrate some key aspects of our theoretical results.

X-ray beam-position feedback system with easy-to-use beam-position monitor.

Science.gov (United States)

Park, Jae Yeon; Kim, Yesul; Lee, Sangsul; Lim, Jun

2018-05-01

X-ray beam-position stability is indispensable in cutting-edge experiments using synchrotron radiation. Here, for the first time, a beam-position feedback system is presented that utilizes an easy-to-use X-ray beam-position monitor incorporating a diamond-fluorescence screen. The acceptable range of the monitor is above 500 µm and the feedback system maintains the beam position within 3 µm. In addition to being inexpensive, the system has two key advantages: it works without a scale factor for position calibration, and it has no dependence on X-ray energy, X-ray intensity, beam size or beam shape.

The Roles of Feedback and Feedforward as Humans Learn to Control Unknown Dynamic Systems.

Science.gov (United States)

Zhang, Xingye; Wang, Shaoqian; Hoagg, Jesse B; Seigler, T Michael

2018-02-01

We present results from an experiment in which human subjects interact with an unknown dynamic system 40 times during a two-week period. During each interaction, subjects are asked to perform a command-following (i.e., pursuit tracking) task. Each subject's performance at that task improves from the first trial to the last trial. For each trial, we use subsystem identification to estimate each subject's feedforward (or anticipatory) control, feedback (or reactive) control, and feedback time delay. Over the 40 trials, the magnitudes of the identified feedback controllers and the identified feedback time delays do not change significantly. In contrast, the identified feedforward controllers do change significantly. By the last trial, the average identified feedforward controller approximates the inverse of the dynamic system. This observation provides evidence that a fundamental component of human learning is updating the anticipatory control until it models the inverse dynamics.

A Social Learning Management System Supporting Feedback for Incorrect Answers Based on Social Network Services

Science.gov (United States)

Son, Jiseong; Kim, Jeong-Dong; Na, Hong-Seok; Baik, Doo-Kwon

2016-01-01

In this research, we propose a Social Learning Management System (SLMS) enabling real-time and reliable feedback for incorrect answers by learners using a social network service (SNS). The proposed system increases the accuracy of learners' assessment results by using a confidence scale and a variety of social feedback that is created and shared…

Simulation of a transverse feedback system for the SSRF storage ring

International Nuclear Information System (INIS)

Jiang Bocheng; Chinese Academy of Sciences, Beijing; Liu Guimin; Zhao Zhentang

2007-01-01

Resistive wall instability is a serious problem in many light sources. An active transverse feedback system (TFS) is required to operate the machine in a good condition when beam current is high. In order to investigate beam dynamics with TFS turned on, we developed a TFS simulation program. The feedback effectiveness for the Shanghai Synchrotron Radiation Facility (SSRF) storage ring is simulated under various conditions such as closed orbit distortion included, beam position monitor reading errors added, and finite-duration impulse-response filter strategy changed. (authors)

A state variable approach to the BESSY II local beam-position-feedback system

International Nuclear Information System (INIS)

Gilpatrick, J.D.; Khan, S.; Kraemer, D.

1996-01-01

At the BESSY II facility, stability of the electron beam position and angle near insertion devices (IDs) is of utmost importance. Disturbances due to ground motion could result in unwanted broad-bandwidth beam-jitter which decreases the electron (and resultant photon) beam's effective brightness. Therefore, feedback techniques must be used. Operating over a frequency range of 100-Hz, a local feedback system will correct these beam-trajectory errors using the four bumps around IDs. This paper reviews how the state-variable feedback approach can be applied to real-time correction of these beam position and angle errors. A frequency-domain solution showing beam jitter reduction is presented. Finally, this paper reports results of a beam-feedback test at BESSY I

Predictive Feedback and Feedforward Control for Systems with Unknown Disturbances

Science.gov (United States)

Juang, Jer-Nan; Eure, Kenneth W.

1998-01-01

Predictive feedback control has been successfully used in the regulation of plate vibrations when no reference signal is available for feedforward control. However, if a reference signal is available it may be used to enhance regulation by incorporating a feedforward path in the feedback controller. Such a controller is known as a hybrid controller. This paper presents the theory and implementation of the hybrid controller for general linear systems, in particular for structural vibration induced by acoustic noise. The generalized predictive control is extended to include a feedforward path in the multi-input multi-output case and implemented on a single-input single-output test plant to achieve plate vibration regulation. There are cases in acoustic-induce vibration where the disturbance signal is not available to be used by the hybrid controller, but a disturbance model is available. In this case the disturbance model may be used in the feedback controller to enhance performance. In practice, however, neither the disturbance signal nor the disturbance model is available. This paper presents the theory of identifying and incorporating the noise model into the feedback controller. Implementations are performed on a test plant and regulation improvements over the case where no noise model is used are demonstrated.

An implementation of sensor-based force feedback in a compact laparoscopic surgery robot.

Science.gov (United States)

Lee, Duk-Hee; Choi, Jaesoon; Park, Jun-Woo; Bach, Du-Jin; Song, Seung-Jun; Kim, Yoon-Ho; Jo, Yungho; Sun, Kyung

2009-01-01

Despite the rapid progress in the clinical application of laparoscopic surgery robots, many shortcomings have not yet been fully overcome, one of which is the lack of reliable haptic feedback. This study implemented a force-feedback structure in our compact laparoscopic surgery robot. The surgery robot is a master-slave configuration robot with 5 DOF (degree of freedom corresponding laparoscopic surgical motion. The force-feedback implementation was made in the robot with torque sensors and controllers installed in the pitch joint of the master and slave robots. A simple dynamic model of action-reaction force in the slave robot was used, through which the reflective force was estimated and fed back to the master robot. The results showed the system model could be identified with significant fidelity and the force feedback at the master robot was feasible. However, the qualitative human assessment of the fed-back force showed only limited level of object discrimination ability. Further developments are underway with this result as a framework.

System analysis of force feedback microscopy

International Nuclear Information System (INIS)

Rodrigues, Mario S.; Costa, Luca; Chevrier, Joël; Comin, Fabio

2014-01-01

It was shown recently that the Force Feedback Microscope (FFM) can avoid the jump-to-contact in Atomic force Microscopy even when the cantilevers used are very soft, thus increasing force resolution. In this letter, we explore theoretical aspects of the associated real time control of the tip position. We take into account lever parameters such as the lever characteristics in its environment, spring constant, mass, dissipation coefficient, and the operating conditions such as controller gains and interaction force. We show how the controller parameters are determined so that the FFM functions at its best and estimate the bandwidth of the system under these conditions

System analysis of force feedback microscopy

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, Mario S. [CFMC/Dep. de Física, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Costa, Luca [European Synchrotron Radiation Facility, 6 rue Jules Horowitz BP 220, 38043 Grenoble Cedex (France); Université Joseph Fourier BP 53, 38041 Grenoble Cedex 9 (France); Chevrier, Joël [European Synchrotron Radiation Facility, 6 rue Jules Horowitz BP 220, 38043 Grenoble Cedex (France); Université Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Comin, Fabio [European Synchrotron Radiation Facility, 6 rue Jules Horowitz BP 220, 38043 Grenoble Cedex (France)

2014-02-07

It was shown recently that the Force Feedback Microscope (FFM) can avoid the jump-to-contact in Atomic force Microscopy even when the cantilevers used are very soft, thus increasing force resolution. In this letter, we explore theoretical aspects of the associated real time control of the tip position. We take into account lever parameters such as the lever characteristics in its environment, spring constant, mass, dissipation coefficient, and the operating conditions such as controller gains and interaction force. We show how the controller parameters are determined so that the FFM functions at its best and estimate the bandwidth of the system under these conditions.

Evaluating Land-Atmosphere Moisture Feedbacks in Earth System Models With Spaceborne Observations

Science.gov (United States)

Levine, P. A.; Randerson, J. T.; Lawrence, D. M.; Swenson, S. C.

2016-12-01

We have developed a set of metrics for measuring the feedback loop between the land surface moisture state and the atmosphere globally on an interannual time scale. These metrics consider both the forcing of terrestrial water storage (TWS) on subsequent atmospheric conditions as well as the response of TWS to antecedent atmospheric conditions. We designed our metrics to take advantage of more than one decade's worth of satellite observations of TWS from the Gravity Recovery and Climate Experiment (GRACE) along with atmospheric variables from the Atmospheric Infrared Sounder (AIRS), the Global Precipitation Climatology Project (GPCP), and Clouds and the Earths Radiant Energy System (CERES). Metrics derived from spaceborne observations were used to evaluate the strength of the feedback loop in the Community Earth System Model (CESM) Large Ensemble (LENS) and in several models that contributed simulations to Phase 5 of the Coupled Model Intercomparison Project (CMIP5). We found that both forcing and response limbs of the feedback loop were generally stronger in tropical and temperate regions in CMIP5 models and even more so in LENS compared to satellite observations. Our analysis suggests that models may overestimate the strength of the feedbacks between the land surface and the atmosphere, which is consistent with previous studies conducted across different spatial and temporal scales.

A longitudinal multi-bunch feedback system using parallel digital signal processors

International Nuclear Information System (INIS)

Sapozhnikov, L.; Fox, J.D.; Olsen, J.J.; Oxoby, G.; Linscott, I.; Drago, A.; Serio, M.

1994-01-01

A programmable longitudinal feedback system based on four AT ampersand T 1610 digital signal processors has been developed as a component of the PEP-II R ampersand D program. This longitudinal quick prototype is a proof of concept for the PEP-II system and implements full-speed bunch-by-bunch signal processing for storage rings with bunch spacings of 4 ns. The design incorporates a phase-detector-based front end that digitizes the oscillation phases of bunches at the 250 MHz crossing rate, four programmable signal processors that compute correction signals, and a 250-MHz hold buffer/kicker driver stage that applies correction signals back on the beam. The design implements a general-purpose, table-driven downsampler that allows the system to be operated at several accelerator facilities. The hardware architecture of the signal processing is described, and the software algorithms used in the feedback signal computation are discussed. The system configuration used for tests at the LBL Advanced Light Source is presented

Quantum learning by measurement and feedback

DEFF Research Database (Denmark)

Gammelmark, Søren; Mølmer, Klaus

2009-01-01

We investigate an approach to quantum computing in which quantum gate strengths are parametrized by quantum degrees of freedom. The capability of the quantum computer to perform desired tasks is monitored by measurements of the output and gradually improved by successive feedback modifications...

Quantum Learning by Measurement and Feedback

DEFF Research Database (Denmark)

Gammelmark, Søren

We investigate an approach to quantum computing in which quantum gate strengths are parametrized by quantum degrees of freedom. The capability of the quantum computer to perform desired tasks is monitored by measurements of the output and gradually improved by successive feedback modifications...

Robust Admissibilization of Descriptor Systems by Static Output-Feedback: An LMI Approach

Directory of Open Access Journals (Sweden)

M. Chaabane

2011-01-01

static output-feedback is studied in this paper and an approach to solve it is proposed. For this, sufficient conditions are derived for the closed-loop system to be admissible (i.e., stable, regular, and impulse-free. These conditions are expressed in terms of a strict Linear Matrix Inequality (LMI; so they are tractable using numerical computations. The proposed controller design methodology is based on two steps: the first is dedicated to synthesizing a classical state-feedback controller, which is used as the initial value for the second step, which uses an LMI problem to obtain static output-feedback controllers that give admissibility. Finally, a numerical example is given to illustrate the results.

Systematic design and simulation of a tearing mode suppression feedback control system for the TEXTOR tokamak

NARCIS (Netherlands)

Hennen, B.A.; Westerhof, E.; Nuij, Pwjm; M.R. de Baar,; Steinbuch, M.

2012-01-01

Suppression of tearing modes is essential for the operation of tokamaks. This paper describes the design and simulation of a tearing mode suppression feedback control system for the TEXTOR tokamak. The two main control tasks of this feedback control system are the radial alignment of electron

Chaotification of Quasi-zero Stiffness System Via Direct Time-delay Feedback

Directory of Open Access Journals (Sweden)

Shuyong Liu

2013-03-01

Full Text Available This paper presents a chaotification method based on direct time-delay feedback control for a quasi-zero-stiffness isolation system. An analytical function of time-delay feedback control is derived based on differential-geometry control theory. Furthermore, the feasibility and effectiveness of this method was verified by numerical simulations. Numerical simulations show that this method holds the favorable aspects including the advantage of using tiny control gain, the capability of chaotifying across a large range of parametric domain and the high feasibility of the control implement.

Autonomous learning by simple dynamical systems with delayed feedback.

Science.gov (United States)

Kaluza, Pablo; Mikhailov, Alexander S

2014-09-01

A general scheme for the construction of dynamical systems able to learn generation of the desired kinds of dynamics through adjustment of their internal structure is proposed. The scheme involves intrinsic time-delayed feedback to steer the dynamics towards the target performance. As an example, a system of coupled phase oscillators, which can, by changing the weights of connections between its elements, evolve to a dynamical state with the prescribed (low or high) synchronization level, is considered and investigated.

Feedback control of plasma equilibrium with control system aided by personal computer on the JIPP T-IIU tokamak

International Nuclear Information System (INIS)

Tsuzuki, T.; Toi, K.; Matsuura, K.

1991-04-01

A feedback control system aided by a personal computer is developed to maintain plasma position on the required position in the JIPP T-IIU tokamak. The personal computer enables to adjust various control parameters easily. In this control system, a control demand for driving the power supply of feedback controlled vertical field coils is composed to be proportional to a total plasma current. This system has been successfully employed throughout the discharge where the plasma current substantially changes from zero to hundreds of kiloamperes, because the feedback control can be done, being independent of the plasma current. The analysis of this feedback control system taken into account of digital sampling agrees well with the experimental results. (author)

Factorization and the synthesis of optimal feedback gains for distributed parameter systems

Science.gov (United States)

Milman, Mark H.; Scheid, Robert E.

1990-01-01

An approach based on Volterra factorization leads to a new methodology for the analysis and synthesis of the optimal feedback gain in the finite-time linear quadratic control problem for distributed parameter systems. The approach circumvents the need for solving and analyzing Riccati equations and provides a more transparent connection between the system dynamics and the optimal gain. The general results are further extended and specialized for the case where the underlying state is characterized by autonomous differential-delay dynamics. Numerical examples are given to illustrate the second-order convergence rate that is derived for an approximation scheme for the optimal feedback gain in the differential-delay problem.

Exponential synchronization of the Genesio-Tesi chaotic system via a novel feedback control

International Nuclear Information System (INIS)

Park, Ju H

2007-01-01

A novel feedback control scheme is proposed for exponential synchronization of the Genesio-Tesi chaotic system. The feedback controller consists of two parts: a linear dynamic control law and a nonlinear control one. For exponential synchronization between the drive and response Genesio-Tesi systems, the Lyapunov stability analysis is used. Then an existence criterion for the stabilizing controller is presented in terms of linear matrix inequalities (LMIs). The LMIs can be solved easily by various convex optimization algorithms. Finally, a numerical simulation is illustrated to show the effectiveness of the proposed chaos synchronization scheme

Frequency domain indirect identification of AMB rotor systems based on fictitious proportional feedback gain

Energy Technology Data Exchange (ETDEWEB)

Ahn, Hyeong Joon [Dept. of Mechanical Engineering, Soongsil University, Seoul (Korea, Republic of); Kim, Chan Jung [Dept. of Mechanical Design Engineering, Pukyong National University, Busan(Korea, Republic of)

2016-12-15

It is very difficult to directly identify an unstable system with uncertain dynamics from frequency domain input-output data. Hence, in these cases, closed-loop frequency responses calculated using a fictitious feedback could be more identifiable than open-loop data. This paper presents a frequency domain indirect identification of AMB rotor systems based on a Fictitious proportional feedback gain (FPFG). The closed-loop effect due to the FPFG can enhance the detectability of the system by moving the system poles, and significantly weigh the target mode in the frequency domain. The effectiveness of the proposed identification method was verified through the frequency domain identification of active magnetic bearing rotor systems.

Ultra high-speed (508 MHz) beam position digital feedback system

International Nuclear Information System (INIS)

Kurokawa, Shin-ichi; Kametani, Masatsugu; Nakayama, Takahide; Moriyama, Kunio.

1997-01-01

The B-Factory which is constructed by National Laboratory for High Energy Physics is the device for elucidating the breakdown of symmetry of matter and antimatter by studying the behavior of B mesons which are generated in large quantity when the electrons and the positrons which are accelerated to light velocity level are collided. In order to maintain electron beam-positron beam bunch circling the ring at light velocity stably, the instability of the coupled bunch must be overcome. For this purpose, the ultrahigh speed beam position digital feedback control system was developed. This system is composed of the high speed input-output substrate using GaAs LSI, the feedback computation substrate using complementary metal oxide semiconductor and the memory mounted on it, and the real time operation device. The development of both substrates and their functions are explained. The real time data collection and the change of computation parameters for specific bunch in the real time operation device have become feasible. The signal transmission characteristics of this system are shown. As the result of the action test of this system, it was confirmed to work normally. (K.I.)

Designing a stable feedback control system for blind image deconvolution.

Science.gov (United States)

Cheng, Shichao; Liu, Risheng; Fan, Xin; Luo, Zhongxuan

2018-05-01

Blind image deconvolution is one of the main low-level vision problems with wide applications. Many previous works manually design regularization to simultaneously estimate the latent sharp image and the blur kernel under maximum a posterior framework. However, it has been demonstrated that such joint estimation strategies may lead to the undesired trivial solution. In this paper, we present a novel perspective, using a stable feedback control system, to simulate the latent sharp image propagation. The controller of our system consists of regularization and guidance, which decide the sparsity and sharp features of latent image, respectively. Furthermore, the formational model of blind image is introduced into the feedback process to avoid the image restoration deviating from the stable point. The stability analysis of the system indicates the latent image propagation in blind deconvolution task can be efficiently estimated and controlled by cues and priors. Thus the kernel estimation used for image restoration becomes more precision. Experimental results show that our system is effective on image propagation, and can perform favorably against the state-of-the-art blind image deconvolution methods on different benchmark image sets and special blurred images. Copyright © 2018 Elsevier Ltd. All rights reserved.

Feedforward-feedback control of dissolved oxygen concentration in a predenitrification system.

Science.gov (United States)

Yong, Ma; Yongzhen, Peng; Shuying, Wang

2005-07-01

As the largest single energy-consuming component in most biological wastewater treatment systems, aeration control is of great interest from the point of view of saving energy and improving wastewater treatment plant efficiency. In this paper, three different strategies, including conventional constant dissolved oxygen (DO) set-point control, cascade DO set-point control, and feedforward-feedback DO set-point control were evaluated using the denitrification layout of the IWA simulation benchmark. Simulation studies showed that the feedforward-feedback DO set-point control strategy was better than the other control strategies at meeting the effluent standards and reducing operational costs. The control strategy works primarily by feedforward control based on an ammonium sensor located at the head of the aerobic process. It has an important advantage over effluent measurements in that there is no (or only a very short) time delay for information; feedforward control was combined with slow feedback control to compensate for model approximations. The feedforward-feedback DO control was implemented in a lab-scale wastewater treatment plant for a period of 60 days. Compared to operation with constant DO concentration, the required airflow could be reduced by up to 8-15% by employing the feedforward-feedback DO-control strategy, and the effluent ammonia concentration could be reduced by up to 15-25%. This control strategy can be expected to be accepted by the operating personnel in wastewater treatment plants.

An audience response system strategy to improve student motivation, attention, and feedback.

Science.gov (United States)

Cain, Jeff; Black, Esther P; Rohr, Jürgen

2009-04-07

To implement an audience response system (ARS) to improve student motivation and attention during lectures and provide immediate feedback to the instructor concerning student understanding of lecture content in a Physiological Chemistry/Molecular Biology course. Students used ARS devices to respond to strategically placed questions throughout physiological chemistry/molecular biology lectures. The instructor inserted 6 to 7 questions that promoted student/class interactivity into each of several 50-minute lectures to focus students' attention and provide feedback on students' comprehension of material. Ninety-eight percent of first-year pharmacy (P1) students (n = 109) reported that strategically placed ARS questions throughout lectures helped them maintain attention. Reports from an independent focus group indicated that students favored this strategy. Furthermore, ARS feedback helped the instructor gauge student comprehension and adjust lectures accordingly. Focused, strategically placed ARS questions throughout lectures may help students maintain attention and stay motivated to learn. Feedback from these questions also allows instructors to adapt lectures to address areas of deficiency.

Simulation of the ALS longitudinal multibunch feedback system

International Nuclear Information System (INIS)

Byrd, J.

1993-05-01

Longitudinal coupled bunch growth rates in the Advanced Light Source (ALS), a 1.5 GeV electron storage ring for producing synchrotron radiation, indicate the need for damping via a feedback (FB) system. The design of the system is based on the proposed PEP-II longitudinal FB system which uses a digital filter to provide the required phase and amplitude response. We report the results of a detailed computer simulation of the FB system including single particle longitudinal beam dynamics, measured RF cavity fundamental and higher order modes, and response of major FB components such as the power amplifier and kicker. The simulation addresses issues such as required FB power and gain, noise, digital filter effects, and varying initial bunch conditions

Beam excitation and damping with the transverse feedback system

International Nuclear Information System (INIS)

Pellegrin, J.L.; Rees, J.R.

1979-08-01

The questions often come up, ''What is the strength if the beam excitation system? How much damping can the transverse feedback provide?'' The design is now advanced enough to answer these questions; also, laboratory tests of some components have been conducted and we know what can be expected of the hardware. This paper discusses these questions

Real-time control systems: feedback, scheduling and robustness

Science.gov (United States)

Simon, Daniel; Seuret, Alexandre; Sename, Olivier

2017-08-01

The efficient control of real-time distributed systems, where continuous components are governed through digital devices and communication networks, needs a careful examination of the constraints arising from the different involved domains inside co-design approaches. Thanks to the robustness of feedback control, both new control methodologies and slackened real-time scheduling schemes are proposed beyond the frontiers between these traditionally separated fields. A methodology to design robust aperiodic controllers is provided, where the sampling interval is considered as a control variable of the system. Promising experimental results are provided to show the feasibility and robustness of the approach.

Implementation status of the global and local beam position feedback systems for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Kirchman, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A.J.

1995-01-01

The Advanced Photon Source (APS) is implementing an extensive beam position feedback system for both global and local stabilization of particle and photon beams based on digital signal processing. The description and operational experience of the system will be given in this paper. In particular, we will discuss the underlying fundamental principles, hardware layout, controls interface, and automatic software generation for multiple digital signal processors (DSPS) distributed in 20 VME crates around the ring. The feedback system runs at 4-kHz sampling frequency in order to achieve the correction bandwidth of approximately 100 Hz. For the maximum correction efficiency and resolution of conflicts among multiple local feedback systems due to the local bump closure error, the global and local feedback systems are combined into a single unified system. This novel approach is made possible through data sharing among the global and local systems via the fiber-optically networked reflective memories

State-PID Feedback for Pole Placement of LTI Systems

Directory of Open Access Journals (Sweden)

Sarawut Sujitjorn

2011-01-01

Full Text Available Pole placement problems are especially important for disturbance rejection and stabilization of dynamical systems and regarded as algebraic inverse eigenvalue problems. In this paper, we propose gain formulae of state feedback through PID-elements to achieve desired pole placement for a delay-free LTI system with single input. Real and complex stable poles can be assigned with the proposed compact gain formulae. Numerical examples show that our proposed gain formulae can be used effectively resulting in very satisfactory responses.

Control of conducting polymer actuators without physical feedback: simulated feedback control approach with particle swarm optimization

International Nuclear Information System (INIS)

Xiang, Xingcan; Mutlu, Rahim; Alici, Gursel; Li, Weihua

2014-01-01

Conducting polymer actuators have shown significant potential in articulating micro instruments, manipulation devices, and robotics. However, implementing a feedback control strategy to enhance their positioning ability and accuracy in any application requires a feedback sensor, which is extremely large in size compared to the size of the actuators. Therefore, this paper proposes a new sensorless control scheme without the use of a position feedback sensor. With the help of the system identification technique and particle swarm optimization, the control scheme, which we call the simulated feedback control system, showed a satisfactory command tracking performance for the conducting polymer actuator’s step and dynamic displacement responses, especially under a disturbance, without needing a physical feedback loop, but using a simulated feedback loop. The primary contribution of this study is to propose and experimentally evaluate the simulated feedback control scheme for a class of the conducting polymer actuators known as tri-layer polymer actuators, which can operate both in dry and wet media. This control approach can also be extended to other smart actuators or systems, for which the feedback control based on external sensing is impractical. (paper)

Group support system and explanatory feedback: An experimental study of mitigating halo effect

Directory of Open Access Journals (Sweden)

Intiyas Utami

2015-12-01

Full Text Available Comprehensive assessment potentially leads to halo effect that will affect accuracy of auditors decision-making process. Biased initial audit decision will potentially influence final audit decision. It is there-fore necessary to mitigate halo effect that is the consequence of auditors good impression on clients initial condition. This re-search aims to empirically show that halo effect can be mitigated by explanatory feedback and Group Support System (GSS. The researchers experimentally mani-pulate explanatory feedback and GSS using online web-site. The subjects are stu-dents who have already taken auditing courses. The results show that: 1 explanato-ry feedback can mitigate halo effect so that audit decision will be more accurate 2 GSS can also mitigate halo effect 3 explanatory feedback and GSS are the best me-thods to mitigate halo effect.

Output Feedback Distributed Containment Control for High-Order Nonlinear Multiagent Systems.

Science.gov (United States)

Li, Yafeng; Hua, Changchun; Wu, Shuangshuang; Guan, Xinping

2017-01-31

In this paper, we study the problem of output feedback distributed containment control for a class of high-order nonlinear multiagent systems under a fixed undirected graph and a fixed directed graph, respectively. Only the output signals of the systems can be measured. The novel reduced order dynamic gain observer is constructed to estimate the unmeasured state variables of the system with the less conservative condition on nonlinear terms than traditional Lipschitz one. Via the backstepping method, output feedback distributed nonlinear controllers for the followers are designed. By means of the novel first virtual controllers, we separate the estimated state variables of different agents from each other. Consequently, the designed controllers show independence on the estimated state variables of neighbors except outputs information, and the dynamics of each agent can be greatly different, which make the design method have a wider class of applications. Finally, a numerical simulation is presented to illustrate the effectiveness of the proposed method.

Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves

DEFF Research Database (Denmark)

Pedersen, Henrik Clemmensen; Andersen, Torben O.; Hansen, Michael R.

2016-01-01

this problem is to use an over centre valve with a sufficiently low pilot ratio and/or include various damping orifices in the system. Both of these solutions are energy consuming and may decrease the control performance. An alternative approach is to use (electronic) pressure feedback — also referred...... to as active damping — to stabilise the system and damp pressure pulsations. This is not a new method, but the effect and adjustment of the filters is often misunderstood leading to incorrectly adjusted filters and degraded system performance. The focus of the current paper is therefore to explain and derive...... a set of guidelines for how to properly adjust a standard pressure feedback in system with an over centre valve when also considering model uncertainties, un-modelled dynamics and parameter variations. The paper takes its basis in a standard cylinder drive with an inertia load, over centre valve...

Stochastic resonance in a bistable system subject to multi-time-delayed feedback and aperiodic signal

International Nuclear Information System (INIS)

Li Jianlong; Zeng Lingzao

2010-01-01

We discuss in detail the effects of the multi-time-delayed feedback driven by an aperiodic signal on the output of a stochastic resonance (SR) system. The effective potential function and dynamical probability density function (PDF) are derived. To measure the performance of the SR system in the presence of a binary random signal, the bit error rate (BER) defined by the dynamical PDF is employed, as is commonly used in digital communications. We find that the delay time, strength of the feedback, and number of time-delayed terms can change the effective potential function and the effective amplitude of the signal, and then affect the BER of the SR system. The numerical simulations strongly support the theoretical results. The goal of this investigation is to explore the effects of the multi-time-delayed feedback on SR and give a guidance to nonlinear systems in the application of information processing.

Survey on multisensory feedback virtual reality dental training systems.

Science.gov (United States)

Wang, D; Li, T; Zhang, Y; Hou, J

2016-11-01

Compared with traditional dental training methods, virtual reality training systems integrated with multisensory feedback possess potentials advantages. However, there exist many technical challenges in developing a satisfactory simulator. In this manuscript, we systematically survey several current dental training systems to identify the gaps between the capabilities of these systems and the clinical training requirements. After briefly summarising the components, functions and unique features of each system, we discuss the technical challenges behind these systems including the software, hardware and user evaluation methods. Finally, the clinical requirements of an ideal dental training system are proposed. Future research/development areas are identified based on an analysis of the gaps between current systems and clinical training requirements. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Beam stability in synchrotrons with digital transverse feedback systems in dependence on beam tunes

International Nuclear Information System (INIS)

Zhabitskij, V.M.

2011-01-01

The beam stability problem in synchrotrons with a digital transverse feedback system (TFS) is studied. The TFS damper kicker (DK) corrects the transverse momentum of a bunch in proportion to its displacement from the closed orbit measured at the location of the beam position monitor (BPM). It is shown that the area and configuration of the beam stability separatrix depend on the beam tune, the feedback gain, the phase balance between the phase advance from BPM to DK and the phase response of the feedback chain at the betatron frequency

Chaotification of vibration isolation floating raft system via nonlinear time-delay feedback control

International Nuclear Information System (INIS)

Zhang Jing; Xu Daolin; Zhou Jiaxi; Li Yingli

2012-01-01

Highlights: ► A chaotification method based on nonlinear time-delay feedback control is present. ► An analytical function of nonlinear time-delay feedback control is derived. ► A large range of parametric domain for chaotification is obtained. ► The approach allows using small control gain. ► Design of chaotification becomes a standard process without uncertainty. - Abstract: This paper presents a chaotification method based on nonlinear time-delay feedback control for a two-dimensional vibration isolation floating raft system (VIFRS). An analytical function of nonlinear time-delay feedback control is derived. This approach can theoretically provide a systematic design of chaotification for nonlinear VIFRS and completely avoid blind and inefficient numerical search on the basis of trials and errors. Numerical simulations show that with a proper setting of control parameters the method holds the favorable aspects including the capability of chaotifying across a large range of parametric domain, the advantage of using small control and the flexibility of designing control feedback forms. The effects on chaotification performance are discussed in association with the configuration of the control parameters.

Investigation of a delayed feedback controller of MEMS resonators

KAUST Repository

Masri, Karim M.

2013-08-04

Controlling mechanical systems is an important branch of mechanical engineering. Several techniques have been used to control Microelectromechanical systems (MEMS) resonators. In this paper, we study the effect of a delayed feedback controller on stabilizing MEMS resonators. A delayed feedback velocity controller is implemented through modifying the parallel plate electrostatic force used to excite the resonator into motion. A nonlinear single degree of freedom model is used to simulate the resonator response. Long time integration is used first. Then, a finite deference technique to capture periodic motion combined with the Floquet theory is used to capture the stable and unstable periodic responses. We show that applying a suitable positive gain can stabilize the MEMS resonator near or inside the instability dynamic pull in band. We also study the stability of the resonator by tracking its basins of attraction while sweeping the controller gain and the frequency of excitations. For positive delayed gains, we notice significant enhancement in the safe area of the basins of attraction. Copyright © 2013 by ASME.

From Static Output Feedback to Structured Robust Static Output Feedback: A Survey

OpenAIRE

Sadabadi , Mahdieh ,; Peaucelle , Dimitri

2016-01-01

This paper reviews the vast literature on static output feedback design for linear time-invariant systems including classical results and recent developments. In particular, we focus on static output feedback synthesis with performance specifications, structured static output feedback, and robustness. The paper provides a comprehensive review on existing design approaches including iterative linear matrix inequalities heuristics, linear matrix inequalities with rank constraints, methods with ...

Feedback in Clinical Education, Part II: Approved Clinical Instructor and Student Perceptions of and Influences on Feedback

Science.gov (United States)

Nottingham, Sara; Henning, Jolene

2014-01-01

Context: Approved Clinical Instructors (ACIs; now known as preceptors) are expected to provide feedback to athletic training students (ATSs) during clinical education experiences. Researchers in other fields have found that clinical instructors and students often have different perceptions of actual and ideal feedback and that several factors may influence the feedback exchanges between instructors and students. However, understanding of these issues in athletic training education is minimal. Objective: To investigate the current characteristics and perceptions of and the influences on feedback exchanges between ATSs and ACIs. Design: Qualitative study. Setting: One entry-level master's degree program accredited by the Commission on Accreditation of Athletic Training Education. Patients or Other Participants: Four ACIs and 4 second-year ATSs. Data Collection and Analysis: Individual, semistructured interviews were conducted with participants and integrated with field notes and observations for analysis. We used the constant comparative approach to inductively analyze data and develop codes and categories. Member checking, triangulation, and peer debriefing were used to promote trustworthiness of the study. Results: Participants described that feedback plays an important role in clinical education and has several purposes related to improving performance. The ACIs and ATSs also discussed several preferred characteristics of feedback. Participants identified 4 main influences on their feedback exchanges, including the ACI, the ATS, personalities, and the learning environment. Conclusions: The ACIs and ATSs had similar perceptions of ideal feedback in addition to the actual feedback that was provided during their clinical education experiences. Most of the preferences for feedback were aligned with recommendations in the literature, suggesting that existing research findings are applicable to athletic training clinical education. Several factors influenced the

Reduction of energy intake using just-in-time feedback from a wearable sensor system.

Science.gov (United States)

Farooq, Muhammad; McCrory, Megan A; Sazonov, Edward

2017-04-01

This work explored the potential use of a wearable sensor system for providing just-in-time (JIT) feedback on the progression of a meal and tested its ability to reduce the total food mass intake. Eighteen participants consumed three meals each in a lab while monitored by a wearable sensor system capable of accurately tracking chew counts. The baseline visit was used to establish the self-determined ingested mass and the associated chew counts. Real-time feedback on chew counts was provided in the next two visits, during which the target chew count was either the same as that at baseline or the baseline chew count reduced by 25% (in randomized order). The target was concealed from the participant and from the experimenter. Nonparametric repeated-measures ANOVAs were performed to compare mass of intake, meal duration, and ratings of hunger, appetite, and thirst across three meals. JIT feedback targeting a 25% reduction in chew counts resulted in a reduction in mass and energy intake without affecting perceived hunger or fullness. JIT feedback on chewing behavior may reduce intake within a meal. This system can be further used to help develop individualized strategies to provide JIT adaptive interventions for reducing energy intake. © 2017 The Obesity Society.

Using the Context of User Feedback in Recommender Systems

Directory of Open Access Journals (Sweden)

Ladislav Peska

2016-12-01

Full Text Available Our work is generally focused on recommending for small or medium-sized e-commerce portals, where explicit feedback is absent and thus the usage of implicit feedback is necessary. Nonetheless, for some implicit feedback features, the presentation context may be of high importance. In this paper, we present a model of relevant contextual features affecting user feedback, propose methods leveraging those features, publish a dataset of real e-commerce users containing multiple user feedback indicators as well as its context and finally present results of purchase prediction and recommendation experiments. Off-line experiments with real users of a Czech travel agency website corroborated the importance of leveraging presentation context in both purchase prediction and recommendation tasks.

The phase detection and calculation for low hybrid wave phase-feedback control system

International Nuclear Information System (INIS)

Liu Qiang; Liang Hao; Zhou Yongzhao; Shan Jiafang

2008-01-01

A method of phase detection and calculation for low hybrid wave phase-feedback control system and the implementing the algorithms on DSP cores embedded in FPGA is introduced. By taking the advantages of matlab-aided design and algorithms optimization to carry out parallel processing of multi-channel phase calculation in FPGA with rich resources, the purposed of fast phase-feedback control is achieved under the need of complicated mathematical operations. (authors)

Extended Cognition: Feedback Loops and Coupled Systems

Directory of Open Access Journals (Sweden)

Olga Markic

2017-12-01

Full Text Available The article explores two waves of active externalism. I first introduce the distinction between passive and active externalism and analyse a proposal of active externalism based on the principle of parity proposed by Clark and Chalmers. There are two main obstacles, causal-constitution fallacy and cognitive bloat, that threaten the extended cognition hypothesis. The second wave of discussions based on the complementarity principle deals with cognitive systems with feedback loops between internal and external elements and is a more radical departure from functionalism and traditional thinking about cognition. I conclude with some remarks on potential ethical considerations of extended cognition.

Bifurcation Regulations Governed by Delay Self-Control Feedback in a Stochastic Birhythmic System

Science.gov (United States)

Ma, Zhidan; Ning, Lijuan

2017-12-01

We aim to investigate bifurcation behaviors in a stochastic birhythmic van der Pol (BVDP) system subjected to delay self-control feedback. First, the harmonic approximation is adopted to drive the delay self-control feedback to state variables without delay. Then, Fokker-Planck-Kolmogorov (FPK) equation and stationary probability density function (SPDF) for amplitude are obtained by applying stochastic averaging method. Finally, dynamical scenarios of the change of delay self-control feedback as well as noise that markedly influence bifurcation performance are observed. It is found that: the big feedback strength and delay will suppress the large amplitude limit cycle (LC) while the relatively big noise strength facilitates the large amplitude LC, which imply the proposed regulation strategies are feasible. Interestingly enough, the inner LC is never destroyed due to noise. Furthermore, the validity of analytical results was verified by Monte Carlo simulation of the dynamics.

Feedback loops and reciprocal regulation: recurring motifs in the systems biology of the cell cycle

OpenAIRE

Ferrell, James E.

2013-01-01

The study of eukaryotic cell cycle regulation over the last several decades has led to a remarkably detailed understanding of the complex regulatory system that drives this fundamental process. This allows us to now look for recurring motifs in the regulatory system. Among these are negative feedback loops, which underpin checkpoints and generate cell cycle oscillations; positive feedback loops, which promote oscillations and make cell cycle transitions switch-like and unidirectional; and rec...

[A Methane Detection System Using Distributed Feedback Laser at 1 654 nm].

Science.gov (United States)

Li, Bin; Liu, Hui-fang; He, Qi-xin; Zhai, Bing; Pan, Jiao-qing; Zheng, Chuan-tao; Wang, Yi-ding

2016-01-01

A methane (CH4) detection system based on tunable diode laser absorption spectroscopy (TDLAS) technique was experimentally demonstrated. A distributed feedback (DFB) laser around 1 654 nm, an open reflective sensing probe and two InGaAs photodiodes were adopted in the system. The electrical part of the system mainly includes the laser temperature control & modulation module and the orthogonal lock-in amplifier module. Temperature and spectrum tests on the DFB laser indicate that, the laser temperature fluctuation can be limited to the range of -0.02-0.02 degrees C, the laser's emitting wavelength varies linearly with the temperature and injection current, and also good operation stability of the laser was observed through experiments. Under a constant working temperature, the center wavelength of the laser is varied linearly by adjusting the driving current. Meanwhile, a 5 kHz sine wave signal and a 10 Hz saw wave signal were provided by the driving circuit for the harmonic extraction purpose. The developed orthogonal lock-in amplifier can extract the If and 2f harmonic signals with the extraction error of 3.55% and 5% respectively. By using the open optical probe, the effective optical pass length was doubled to 40 cm. Gas detection experiment was performed to derive the relation between the harmonic amplitude and the gas concentration. As the concentration increases from 1% to 5%, the amplitudes of the 1f harmonic and the 2f harmonic signal were obtained, and good linear ration between the concentration and the amplitude ratio was observed, which proves the normal function of the developed detection system. This system is capable to detect other trace gases by using relevant DFB lasers.

Study on fault diagnosis and load feedback control system of combine harvester

Science.gov (United States)

Li, Ying; Wang, Kun

2017-01-01

In order to timely gain working status parameters of operating parts in combine harvester and improve its operating efficiency, fault diagnosis and load feedback control system is designed. In the system, rotation speed sensors were used to gather these signals of forward speed and rotation speeds of intermediate shaft, conveying trough, tangential and longitudinal flow threshing rotors, grain conveying auger. Using C8051 single chip microcomputer (SCM) as processor for main control unit, faults diagnosis and forward speed control were carried through by rotation speed ratio analysis of each channel rotation speed and intermediate shaft rotation speed by use of multi-sensor fused fuzzy control algorithm, and these processing results would be sent to touch screen and display work status of combine harvester. Field trials manifest that fault monitoring and load feedback control system has good man-machine interaction and the fault diagnosis method based on rotation speed ratios has low false alarm rate, and the system can realize automation control of forward speed for combine harvester.

Factorization and the synthesis of optimal feedback kernels for differential-delay systems

Science.gov (United States)

Milman, Mark M.; Scheid, Robert E.

1987-01-01

A combination of ideas from the theories of operator Riccati equations and Volterra factorizations leads to the derivation of a novel, relatively simple set of hyperbolic equations which characterize the optimal feedback kernel for the finite-time regulator problem for autonomous differential-delay systems. Analysis of these equations elucidates the underlying structure of the feedback kernel and leads to the development of fast and accurate numerical methods for its computation. Unlike traditional formulations based on the operator Riccati equation, the gain is characterized by means of classical solutions of the derived set of equations. This leads to the development of approximation schemes which are analogous to what has been accomplished for systems of ordinary differential equations with given initial conditions.

Decentralised output feedback control of Markovian jump interconnected systems with unknown interconnections

Science.gov (United States)

Li, Li-Wei; Yang, Guang-Hong

2017-07-01

The problem of decentralised output feedback control is addressed for Markovian jump interconnected systems with unknown interconnections and general transition rates (TRs) allowed to be unknown or known with uncertainties. A class of decentralised dynamic output feedback controllers are constructed, and a cyclic-small-gain condition is exploited to dispose the unknown interconnections so that the resultant closed-loop system is stochastically stable and satisfies an H∞ performance. With slack matrices to cope with the nonlinearities incurred by unknown and uncertain TRs in control synthesis, a novel controller design condition is developed in linear matrix inequality formalism. Compared with the existing works, the proposed approach leads to less conservatism. Finally, two examples are used to illustrate the effectiveness of the new results.

MATHEMATICAL MODEL OF AUTOMATED REHABILITATION SYSTEM WITH BIOLOGICAL FEEDBACK FOR REHABILITATION AND DEVELOPMENT OF MUSCULOSKELETAL SYSTEM

Directory of Open Access Journals (Sweden)

Kirill A. Kalyashin

2013-01-01

Full Text Available In order to increase the efficiency and safety of rehabilitation of musculoskeletal system, the model and the algorithm for patient interaction with automated rehabilitation system with biological feedback was developed, based on registration and management of the second functional parameter, which prevents risks of overwork while intensive exercises.

A software module for implementing auditory and visual feedback on a video-based eye tracking system

Science.gov (United States)

Rosanlall, Bharat; Gertner, Izidor; Geri, George A.; Arrington, Karl F.

2016-05-01

We describe here the design and implementation of a software module that provides both auditory and visual feedback of the eye position measured by a commercially available eye tracking system. The present audio-visual feedback module (AVFM) serves as an extension to the Arrington Research ViewPoint EyeTracker, but it can be easily modified for use with other similar systems. Two modes of audio feedback and one mode of visual feedback are provided in reference to a circular area-of-interest (AOI). Auditory feedback can be either a click tone emitted when the user's gaze point enters or leaves the AOI, or a sinusoidal waveform with frequency inversely proportional to the distance from the gaze point to the center of the AOI. Visual feedback is in the form of a small circular light patch that is presented whenever the gaze-point is within the AOI. The AVFM processes data that are sent to a dynamic-link library by the EyeTracker. The AVFM's multithreaded implementation also allows real-time data collection (1 kHz sampling rate) and graphics processing that allow display of the current/past gaze-points as well as the AOI. The feedback provided by the AVFM described here has applications in military target acquisition and personnel training, as well as in visual experimentation, clinical research, marketing research, and sports training.

Recurrent fuzzy neural network by using feedback error learning approaches for LFC in interconnected power system

International Nuclear Information System (INIS)

Sabahi, Kamel; Teshnehlab, Mohammad; Shoorhedeli, Mahdi Aliyari

2009-01-01

In this study, a new adaptive controller based on modified feedback error learning (FEL) approaches is proposed for load frequency control (LFC) problem. The FEL strategy consists of intelligent and conventional controllers in feedforward and feedback paths, respectively. In this strategy, a conventional feedback controller (CFC), i.e. proportional, integral and derivative (PID) controller, is essential to guarantee global asymptotic stability of the overall system; and an intelligent feedforward controller (INFC) is adopted to learn the inverse of the controlled system. Therefore, when the INFC learns the inverse of controlled system, the tracking of reference signal is done properly. Generally, the CFC is designed at nominal operating conditions of the system and, therefore, fails to provide the best control performance as well as global stability over a wide range of changes in the operating conditions of the system. So, in this study a supervised controller (SC), a lookup table based controller, is addressed for tuning of the CFC. During abrupt changes of the power system parameters, the SC adjusts the PID parameters according to these operating conditions. Moreover, for improving the performance of overall system, a recurrent fuzzy neural network (RFNN) is adopted in INFC instead of the conventional neural network, which was used in past studies. The proposed FEL controller has been compared with the conventional feedback error learning controller (CFEL) and the PID controller through some performance indices

Development of a medical academic degree system in China.

Science.gov (United States)

Wu, Lijuan; Wang, Youxin; Peng, Xiaoxia; Song, Manshu; Guo, Xiuhua; Nelson, Hugh; Wang, Wei

2014-01-01

The Chinese government launched a comprehensive healthcare reform to tackle challenges to health equities. Medical education will become the key for successful healthcare reform. We describe the current status of the Chinese medical degree system and its evolution over the last 80 years. Progress has been uneven, historically punctuated most dramatically by the Cultural Revolution. There is a great regional disparity. Doctors with limited tertiary education may be licensed to practice, whereas medical graduates with advanced doctorates may have limited clinical skills. There are undefined relationships between competing tertiary training streams, the academic professional degree, and the clinical residency training programme (RTP). The perceived quality of training in both streams varies widely across China. As the degrees of master or doctor of academic medicine is seen as instrumental in career advancement, including employability in urban hospitals, attainment of this degree is sought after, yet is often unrelated to a role in health care, or is seen as superior to clinical experience. Meanwhile, the practical experience gained in some prestigious academic institutions is deprecated by the RTP and must be repeated before accreditation for clinical practice. This complexity is confusing both for students seeking the most appropriate training, and also for clinics, hospitals and universities seeking to recruit the most appropriate applicants. The future education reforms might include: 1) a domestic system of 'credits' that gives weight to quality clinical experience vs. academic publications in career advancement, enhanced harmonisation between the competing streams of the professional degree and the RTP, and promotion of mobility of staff between areas of excellence and areas of need; 2) International - a mutual professional and academic recognition between China and other countries by reference to the Bologna Accord, setting up a system of easily comparable and

The cloud-phase feedback in the Super-parameterized Community Earth System Model

Science.gov (United States)

Burt, M. A.; Randall, D. A.

2016-12-01

Recent comparisons of observations and climate model simulations by I. Tan and colleagues have suggested that the Wegener-Bergeron-Findeisen (WBF) process tends to be too active in climate models, making too much cloud ice, and resulting in an exaggerated negative cloud-phase feedback on climate change. We explore the WBF process and its effect on shortwave cloud forcing in present-day and future climate simulations with the Community Earth System Model, and its super-parameterized counterpart. Results show that SP-CESM has much less cloud ice and a weaker cloud-phase feedback than CESM.

Feedback as real-time constructions

DEFF Research Database (Denmark)

Keiding, Tina Bering; Qvortrup, Ane

2014-01-01

instant it takes place. This article argues for a clear distinction between the timing of communicative events, such as responses that are provided as help for feedback constructions, and the feedback construction itself as an event in a psychic system. Although feedback is described as an internal...

An Artificial Immune System with Feedback Mechanisms for Effective Handling of Population Size

Science.gov (United States)

Gao, Shangce; Wang, Rong-Long; Ishii, Masahiro; Tang, Zheng

This paper represents a feedback artificial immune system (FAIS). Inspired by the feedback mechanisms in the biological immune system, the proposed algorithm effectively manipulates the population size by increasing and decreasing B cells according to the diversity of the current population. Two kinds of assessments are used to evaluate the diversity aiming to capture the characteristics of the problem on hand. Furthermore, the processing of adding and declining the number of population is designed. The validity of the proposed algorithm is tested for several traveling salesman benchmark problems. Simulation results demonstrate the efficiency of the proposed algorithm when compared with the traditional genetic algorithm and an improved clonal selection algorithm.

Using field feedback to estimate failure rates of safety-related systems

International Nuclear Information System (INIS)

Brissaud, Florent

2017-01-01

The IEC 61508 and IEC 61511 functional safety standards encourage the use of field feedback to estimate the failure rates of safety-related systems, which is preferred than generic data. In some cases (if “Route 2_H” is adopted for the 'hardware safety integrity constraints”), this is even a requirement. This paper presents how to estimate the failure rates from field feedback with confidence intervals, depending if the failures are detected on-line (called 'detected failures', e.g. by automatic diagnostic tests) or only revealed by proof tests (called 'undetected failures'). Examples show that for the same duration and number of failures observed, the estimated failure rates are basically higher for “undetected failures” because, in this case, the duration observed includes intervals of time where it is unknown that the elements have failed. This points out the need of using a proper approach for failure rates estimation, especially for failures that are not detected on-line. Then, this paper proposes an approach to use the estimated failure rates, with their uncertainties, for PFDavg and PFH assessment with upper confidence bounds, in accordance with IEC 61508 and IEC 61511 requirements. Examples finally show that the highest SIL that can be claimed for a safety function can be limited by the 90% upper confidence bound of PFDavg or PFH. The requirements of the IEC 61508 and IEC 61511 relating to the data collection and analysis should therefore be properly considered for the study of all safety-related systems. - Highlights: • This paper deals with requirements of the IEC 61508 and IEC 61511 for using field feedback to estimate failure rates of safety-related systems. • This paper presents how to estimate the failure rates from field feedback with confidence intervals for failures that are detected on-line. • This paper presents how to estimate the failure rates from field feedback with confidence intervals for failures that are only revealed by

Peripheral visual feedback: a powerful means of supporting effective attention allocation in event-driven, data-rich environments.

Science.gov (United States)

Nikolic, M I; Sarter, N B

2001-01-01

Breakdowns in human-automation coordination in data-rich, event-driven domains such as aviation can be explained in part by a mismatch between the high degree of autonomy yet low observability of modern technology. To some extent, the latter is the result of an increasing reliance in feedback design on foveal vision--an approach that fails to support pilots in tracking system-induced changes and events in parallel with performing concurrent flight-related tasks. One possible solution to the problem is the distribution of tasks and information across sensory modalities and processing channels. A simulator study is presented that compared the effectiveness of current foveal feedback and two implementations of peripheral visual feedback for keeping pilots informed about uncommanded changes in the status of an automated cockpit system. Both peripheral visual displays resulted in higher detection rates and faster response times, without interfering with the performance of concurrent visual tasks any more than does currently available automation feedback. Potential applications include improved display designs that support effective attention allocation in a variety of complex dynamic environments, such as aviation, process control, and medicine.

Effects of feedback reliability on feedback-related brain activity: A feedback valuation account.

Science.gov (United States)

Ernst, Benjamin; Steinhauser, Marco

2018-04-06

Adaptive decision making relies on learning from feedback. Because feedback sometimes can be misleading, optimal learning requires that knowledge about the feedback's reliability be utilized to adjust feedback processing. Although previous research has shown that feedback reliability indeed influences feedback processing, the underlying mechanisms through which this is accomplished remain unclear. Here we propose that feedback processing is adjusted by the adaptive, top-down valuation of feedback. We assume that unreliable feedback is devalued relative to reliable feedback, thus reducing the reward prediction errors that underlie feedback-related brain activity and learning. A crucial prediction of this account is that the effects of feedback reliability are susceptible to contrast effects. That is, the effects of feedback reliability should be enhanced when both reliable and unreliable feedback are experienced within the same context, as compared to when only one level of feedback reliability is experienced. To evaluate this prediction, we measured the event-related potentials elicited by feedback in two experiments in which feedback reliability was varied either within or between blocks. We found that the fronto-central valence effect, a correlate of reward prediction errors during reinforcement learning, was reduced for unreliable feedback. But this result was obtained only when feedback reliability was varied within blocks, thus indicating a contrast effect. This suggests that the adaptive valuation of feedback is one mechanism underlying the effects of feedback reliability on feedback processing.

Feedback linearization based control of a variable air volume air conditioning system for cooling applications.

Science.gov (United States)

Thosar, Archana; Patra, Amit; Bhattacharyya, Souvik

2008-07-01

Design of a nonlinear control system for a Variable Air Volume Air Conditioning (VAVAC) plant through feedback linearization is presented in this article. VAVAC systems attempt to reduce building energy consumption while maintaining the primary role of air conditioning. The temperature of the space is maintained at a constant level by establishing a balance between the cooling load generated in the space and the air supply delivered to meet the load. The dynamic model of a VAVAC plant is derived and formulated as a MIMO bilinear system. Feedback linearization is applied for decoupling and linearization of the nonlinear model. Simulation results for a laboratory scale plant are presented to demonstrate the potential of keeping comfort and maintaining energy optimal performance by this methodology. Results obtained with a conventional PI controller and a feedback linearizing controller are compared and the superiority of the proposed approach is clearly established.

Exploring the bases for a mixed reality stroke rehabilitation system, Part II: design of interactive feedback for upper limb rehabilitation.

Science.gov (United States)

Lehrer, Nicole; Chen, Yinpeng; Duff, Margaret; L Wolf, Steven; Rikakis, Thanassis

2011-09-08

Few existing interactive rehabilitation systems can effectively communicate multiple aspects of movement performance simultaneously, in a manner that appropriately adapts across various training scenarios. In order to address the need for such systems within stroke rehabilitation training, a unified approach for designing interactive systems for upper limb rehabilitation of stroke survivors has been developed and applied for the implementation of an Adaptive Mixed Reality Rehabilitation (AMRR) System. The AMRR system provides computational evaluation and multimedia feedback for the upper limb rehabilitation of stroke survivors. A participant's movements are tracked by motion capture technology and evaluated by computational means. The resulting data are used to generate interactive media-based feedback that communicates to the participant detailed, intuitive evaluations of his performance. This article describes how the AMRR system's interactive feedback is designed to address specific movement challenges faced by stroke survivors. Multimedia examples are provided to illustrate each feedback component. Supportive data are provided for three participants of varying impairment levels to demonstrate the system's ability to train both targeted and integrated aspects of movement. The AMRR system supports training of multiple movement aspects together or in isolation, within adaptable sequences, through cohesive feedback that is based on formalized compositional design principles. From preliminary analysis of the data, we infer that the system's ability to train multiple foci together or in isolation in adaptable sequences, utilizing appropriately designed feedback, can lead to functional improvement. The evaluation and feedback frameworks established within the AMRR system will be applied to the development of a novel home-based system to provide an engaging yet low-cost extension of training for longer periods of time.

Digital filter algorithm study and simulation of SSRF feedback system

International Nuclear Information System (INIS)

Han Lifeng; Yuan Renxian; Ye Kairong

2008-01-01

Least Square Fitting was used to design a FIR filter of the transverse feedback system for the Shanghai Synchrotron Radiation Facility (SSRF). The algorithm helped us to set appropriate gain and phase at special frequency points. This reduced the power needed for damping the beam oscillations, which was proved by System View signal simulation. And with AT (Accelerator Tool) simulation, the Gain calculation and settings to the output signals from the FIR filter were deduced. The relationship between the Kicker power and the system damping time was also given. (authors)

The intensity feedback system at Heidelberg Ion-Beam Therapy Centre

Energy Technology Data Exchange (ETDEWEB)

Schoemers, Christian, E-mail: christian.schoemers@med.uni-heidelberg.de; Feldmeier, Eike; Naumann, Jakob; Panse, Ralf; Peters, Andreas; Haberer, Thomas

2015-09-21

At Heidelberg Ion-Beam Therapy Centre (HIT), more than 2500 tumour patients have been treated with charged particle beams since 2009 using the raster scanning method. The tumour is irradiated slice-by-slice, each slice corresponding to a different beam energy. For the particle dose of each raster point the pre-irradiation by more distal slices has to be considered. This leads to highly inhomogeneous dose distributions within one iso-energy slice. The particles are extracted from the synchrotron via transverse RF knock-out. A pure feed forward control cannot take into account fluence inhomogeneities or deal with intensity fluctuations. So far, fluctuations have been counteracted by a reduced scanning velocity. We now added a feedback loop to the extraction system. The dose monitoring ionisation chambers in front of the patient have been coupled to the extraction device in the synchrotron. Characterization and implementation of the intensity feedback system into the HIT facility is described here. By its implementation the treatment time has been reduced by 10% in average.

Near-real-time feedback control system for liver thermal ablations based on self-referenced temperature imaging

International Nuclear Information System (INIS)

Keserci, Bilgin M.; Kokuryo, Daisuke; Suzuki, Kyohei; Kumamoto, Etsuko; Okada, Atsuya; Khankan, Azzam A.; Kuroda, Kagayaki

2006-01-01

Our challenge was to design and implement a dedicated temperature imaging feedback control system to guide and assist in a thermal liver ablation procedure in a double-donut 0.5T open MR scanner. This system has near-real-time feedback capability based on a newly developed 'self-referenced' temperature imaging method using 'moving-slab' and complex-field-fitting techniques. Two phantom validation studies and one ex vivo experiment were performed to compare the newly developed self-referenced method with the conventional subtraction method and evaluate the ability of the feedback control system in the same MR scanner. The near-real-time feedback system was achieved by integrating the following primary functions: (1) imaging of the moving organ temperature; (2) on-line needle tip tracking; (3) automatic turn-on/off the heating devices; (4) a Windows operating system-based novel user-interfaces. In the first part of the validation studies, microwave heating was applied in an agar phantom using a fast spoiled gradient recalled echo in a steady state sequence. In the second part of the validation and ex vivo study, target visualization, treatment planning and monitoring, and temperature and thermal dose visualization with the graphical user interface of the thermal ablation software were demonstrated. Furthermore, MR imaging with the 'self-referenced' temperature imaging method has the ability to localize the hot spot in the heated region and measure temperature elevation during the experiment. In conclusion, we have demonstrated an interactively controllable feedback control system that offers a new method for the guidance of liver thermal ablation procedures, as well as improving the ability to assist ablation procedures in an open MR scanner

Development of comprehensive unattended child warning and feedback system in vehicle

Directory of Open Access Journals (Sweden)

Sulaiman Norizam

2017-01-01

Full Text Available The cases of children being trapped and suffocated in unattended vehicle keep increasing even though the awareness campaign on the safety of children in non-moving vehicle were carried out by government. Various methods were introduced by researchers to overcome this issue but yet to be effective. Among them were the usage of capacitive sensor, microwave sensor, pressure sensor and image sensor where most of the techniques or systems were applied on the child’s seat to detect the presence of baby or infant. Thus, this research is carried out to provide a comprehensive and effective detection system to detect the presence of children including infant in unattended vehicle by using the combination of human physiological signals (voice and body odor detectors with the temperature and motion sensors. Here, once the proposed system recognizes any signals that generated from voice, odor, motion and temperature detectors in vehicle’s cabin, the system then will provide effective feedback system by sending short message to the parents first. If no response received in the specified allocation time, the system then will activate the vehicle’s horn system. Finally, the system will lower down the vehicle’s window to release the toxic gas and reduce the cabin temperature. The system is in prototyping stage where every design component was evaluated individually. Besides, the overall system was successfully tested where the detection and feedback system follow the instruction given by the microcontroller.

On the Internal Model Principle in the Coordination of Nonlinear Systems

NARCIS (Netherlands)

De Persis, C.; Jayawardhana, B.

2014-01-01

The role of the internal model principle is investigated in this paper for the coordination of relative-degree-one and relative-degree-two nonlinear systems. For relative-degree-one systems that are incrementally (output-feedback) passive, we propose internal-model-based distributed control laws

Theory and Applications of Discontinuous State Feedback Generating Chaos for Linear Systems

International Nuclear Information System (INIS)

Xiao-Dan, Zhang; Zhen, Wang; Pin-Dong, Zhao

2008-01-01

We investigate a kind of chaos generating technique on a type of n-dimensional linear differential systems by adding feedback control items under a discontinuous state. This method is checked with some examples of numeric simulation. A constructive theorem is proposed for generalized synchronization related to the above chaotic system

Real-time orbit feedback at the APS

International Nuclear Information System (INIS)

Carwardine, J.

1998-01-01

A real-time orbit feedback system has been implemented at the Advanced Photon Source in order to meet the stringent orbit stability requirements. The system reduces global orbit motion below 30Hz by a factor of four to below 5 microm rms horizontally and 2 microm rms vertically. This paper focuses on dynamic orbit stability and describes the all-digital orbit feedback system that has been implemented at the APS. Implementation of the global orbit feedback system is described and its latest performance is presented. Ultimately, the system will provide local feedback at each x-ray source point using installed photon BPMs to measure x-ray beam position and angle directly. Technical challenges associated with local feedback and with dynamics of the associated corrector magnets are described. The unique diagnostic capabilities provided by the APS system are discussed with reference to their use in identifying sources of the underlying orbit motion

Developing a patient-led electronic feedback system for quality and safety within Renal PatientView.

Science.gov (United States)

Giles, Sally J; Reynolds, Caroline; Heyhoe, Jane; Armitage, Gerry

2017-03-01

It is increasingly acknowledged that patients can provide direct feedback about the quality and safety of their care through patient reporting systems. The aim of this study was to explore the feasibility of patients, healthcare professionals and researchers working in partnership to develop a patient-led quality and safety feedback system within an existing electronic health record (EHR), known as Renal PatientView (RPV). Phase 1 (inception) involved focus groups (n = 9) and phase 2 (requirements) involved cognitive walkthroughs (n = 34) and 1:1 qualitative interviews (n = 34) with patients and healthcare professionals. A Joint Services Expert Panel (JSP) was convened to review the findings from phase 1 and agree the core principles and components of the system prototype. Phase 1 data were analysed using a thematic approach. Data from phase 1 were used to inform the design of the initial system prototype. Phase 2 data were analysed using the components of heuristic evaluation, resulting in a list of core principles and components for the final system prototype. Phase 1 identified four main barriers and facilitators to patients feeding back on quality and safety concerns. In phase 2, the JSP agreed that the system should be based on seven core principles and components. Stakeholders were able to work together to identify core principles and components for an electronic patient quality and safety feedback system in renal services. Tensions arose due to competing priorities, particularly around anonymity and feedback. Careful consideration should be given to the feasibility of integrating a novel element with differing priorities into an established system with existing functions and objectives. © 2016 European Dialysis and Transplant Nurses Association/European Renal Care Association.

A waveguide overloaded cavity as longitudinal kicker for the DA{Phi}NE bunch-by-bunch feedback system

Energy Technology Data Exchange (ETDEWEB)

Gallo, A; Boni, R; Ghigo, A; Marcellini, F; Serio, M; Zobov, M [Instituto Nazionale de Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati

1996-08-01

The multibunch operation of DA{Phi}NE calls for a very efficient feedback system to damp the coupled-bunch longitudinal instabilities. A collaboration program among SLAC, LBL and LNF laboratories on this subject led to the development of a time domain, digital system based on digital signal processors that has been already successfully tested at ALS. The feedback chain ends with the longitudinal kicker, an electromagnetic structure capable of transferring the proper energy correction to each bunch. A cavity kicker for the DA{Phi}NE bunch-by-bunch longitudinal feedback system based on a pill-box loaded by six waveguides has been designed and a full-scale aluminium prototype has been fabricated at LNF. Both simulations and measurements have shown a peak shunt impedance of about 750 ohm and a bandwidth of about 220 MHz. The large shunt impedance allows to economize on the costly feedback power. Moreover, the damping waveguides drastically reduce the device HOM longitudinal and transverse impedances. One cavity pre ring will be sufficient to operate the machine up to 30 bunches while a second device per ring together with a feedback power improvement will be necessary to reach the ultimate current. (G.T.)

FY1995 study of feedback type gait training system; 1995 nendo feedback gata hoko kuren sochi ni kansuru kenkyu kaihatsu

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

The purpose of this project is to develop and demonstrate the utility of feedback type gait training equipment designed for the measurement and evaluation by a walking training of the aged or patient. As similar concepts of walking training, a locomotion in the water for the aged is applied in rehabilitation. Our development of this study established the system of a suspending mechanism which revolves around the prop, and a walking on the circular type force plate by the aged or patient. It is possible to detect a walking reaction force of several patients from force plate simultaneously. And then, the data from force plate makes feedback signal to put up the patient like a buoyancy in the water. Concerning the evaluations of walking pattern a step range, a hanging ratio and a walking speed, etc. are acquired for each patient by the acknowledgment base. This system is actively able to perform a walking training continuously compared with conventional passive gait equipment. (NEDO)

Optoelectronic instrumentation enhancement using data mining feedback for a 3D measurement system

Science.gov (United States)

Flores-Fuentes, Wendy; Sergiyenko, Oleg; Gonzalez-Navarro, Félix F.; Rivas-López, Moisés; Hernandez-Balbuena, Daniel; Rodríguez-Quiñonez, Julio C.; Tyrsa, Vera; Lindner, Lars

2016-12-01

3D measurement by a cyber-physical system based on optoelectronic scanning instrumentation has been enhanced by outliers and regression data mining feedback. The prototype has applications in (1) industrial manufacturing systems that include: robotic machinery, embedded vision, and motion control, (2) health care systems for measurement scanning, and (3) infrastructure by providing structural health monitoring. This paper presents new research performed in data processing of a 3D measurement vision sensing database. Outliers from multivariate data have been detected and removal to improve artificial intelligence regression algorithm results. Physical measurement error regression data has been used for 3D measurements error correction. Concluding, that the joint of physical phenomena, measurement and computation is an effectiveness action for feedback loops in the control of industrial, medical and civil tasks.

Research of the master-slave robot surgical system with the function of force feedback.

Science.gov (United States)

Shi, Yunyong; Zhou, Chaozheng; Xie, Le; Chen, Yongjun; Jiang, Jun; Zhang, Zhenfeng; Deng, Ze

2017-12-01

Surgical robots lack force feedback, which may lead to operation errors. In order to improve surgical outcomes, this research developed a new master-slave surgical robot, which was designed with an integrated force sensor. The new structure designed for the master-slave robot employs a force feedback mechanism. A six-dimensional force sensor was mounted on the tip of the slave robot's actuator. Sliding model control was adopted to control the slave robot. According to the movement of the master system manipulated by the surgeon, the slave's movement and the force feedback function were validated. The motion was completed, the standard deviation was calculated, and the force data were detected. Hence, force feedback was realized in the experiment. The surgical robot can help surgeons to complete trajectory motions with haptic sensation. Copyright © 2017 John Wiley & Sons, Ltd.

Nonlinear feedback synchronisation control between fractional-order and integer-order chaotic systems

International Nuclear Information System (INIS)

Jia Li-Xin; Dai Hao; Hui Meng

2010-01-01

This paper focuses on the synchronisation between fractional-order and integer-order chaotic systems. Based on Lyapunov stability theory and numerical differentiation, a nonlinear feedback controller is obtained to achieve the synchronisation between fractional-order and integer-order chaotic systems. Numerical simulation results are presented to illustrate the effectiveness of this method

Education for Managing Digital Transformation: A Feedback Systems Approach

Directory of Open Access Journals (Sweden)

Michael Von Kutzschenbach

2017-04-01

Full Text Available "Digital transformation" is becoming the newest mantra of business leaders. It is clear that there are tremendous business opportunities resulting from this revolution, but there is also a price to be paid. Most management literature focuses on the benefits of digitalization, reflecting the desire to increase performance and efficiency in selected business activities. However, digital transformations may lead to the disruption of established ways of doing the work of the firm, stakeholder power may be fundamentally changed, and there is the potential for redefining the nature of the firm itself. Consequently, the decision to "go digital" requires managers to develop perspectives that have the requisite variety to cope with these challenges. Feedback systems thinking is a powerful means for managers to develop and communicate business models that include those aspects of digitalization that affects their firm's theory of success. The Uber case illustrates the principles of applying feedback systems thinking to the radical changes that it has presented the public transportation sector. This paper analyzes Uber's platform business by presenting an endogenous explanation of the drivers and eventual constraints to growth of the theory of success upon which the firm is based. This type of analysis has implications for all firms considering implementing a significant digital transformation process.

Robot-assisted microsurgical forceps with haptic feedback for transoral laser microsurgery.

Science.gov (United States)

Deshpande, Nikhil; Chauhan, Manish; Pacchierotti, Claudio; Prattichizzo, Domenico; Caldwell, Darwin G; Mattos, Leonardo S

2016-08-01

In this paper, a novel, motorized, multi-degrees-of-freedom (DoF), microsurgical forceps tool is presented, which is based on a master-slave teleoperation architecture. The slave device is a 7-DoF manipulator with: (i) 6-DoF positioning and orientation, (ii) 1 open/close gripper DoF; and (iii) an integrated force/torque sensor for tissue grip-force measurement. The master device is a 7-DoF haptic interface which teleoperates the slave device, and provides haptic feedback in its gripper interface. The combination of the device and the surgeon interface replaces the manual, hand-held device providing easy-to-use and ergonomic tissue control, simplifying the surgical tasks. This makes the system suitable to real surgical scenarios in the operating room (OR). The performance of the system was analysed through the evaluation of teleoperation control and characterization of gripping force. The new system offers an overall positioning error of less than 400 μm demonstrating its safety and accuracy. Improved system precision, usability, and ergonomics point to the potential suitability of the device for the OR and its ability to advance haptic-feedback-enhanced transoral laser microsurgeries.

Mode Selection Rules for a Two-Delay System with Positive and Negative Feedback Loops

Science.gov (United States)

Takahashi, Kin'ya; Kobayashi, Taizo

2018-04-01

The mode selection rules for a two-delay system, which has negative feedback with a short delay time t1 and positive feedback with a long delay time t2, are studied numerically and theoretically. We find two types of mode selection rules depending on the strength of the negative feedback. When the strength of the negative feedback |α1| (α1 0), 2m + 1-th harmonic oscillation is well sustained in a neighborhood of t1/t2 = even/odd, i.e., relevant condition. In a neighborhood of the irrelevant condition given by t1/t2 = odd/even or t1/t2 = odd/odd, higher harmonic oscillations are observed. However, if |α1| is slightly less than α2, a different mode selection rule works, where the condition t1/t2 = odd/even is relevant and the conditions t1/t2 = odd/odd and t1/t2 = even/odd are irrelevant. These mode selection rules are different from the mode selection rule of the normal two-delay system with two positive feedback loops, where t1/t2 = odd/odd is relevant and the others are irrelevant. The two types of mode selection rules are induced by individually different mechanisms controlling the Hopf bifurcation, i.e., the Hopf bifurcation controlled by the "boosted bifurcation process" and by the "anomalous bifurcation process", which occur for |α1| below and above the threshold value αth, respectively.

Real-time orbit feedback at the APS

International Nuclear Information System (INIS)

Carwardine, J.A.; Lenkszus, F.R.

1998-01-01

A real-time orbit feedback system has been implemented at the Advanced Photon Source in order to meet the stringent orbit stability requirements. The system reduces global orbit motion below 30 Hz by a factor of four to below 5 μm rms horizontally and 2 μm rms vertically. This paper focuses on dynamic orbit stability and describes the all-digital orbit feedback system that has been implemented at the APS. Implementation of the global orbit feedback system is described and its latest performance is presented. Ultimately, the system will provide local feedback at each x-ray source point using installed photon BPMs to measure x-ray beam position and angle directly. Technical challenges associated with local feedback and with dynamics of the associated corrector magnets are described. The unique diagnostic capabilities provided by the APS system are discussed with reference to their use in identifying sources of the underlying orbit motion. copyright 1998 American Institute of Physics

Real-time orbit feedback at the APS.

Energy Technology Data Exchange (ETDEWEB)

Carwardine, J.

1998-06-18

A real-time orbit feedback system has been implemented at the Advanced Photon Source in order to meet the stringent orbit stability requirements. The system reduces global orbit motion below 30Hz by a factor of four to below 5{micro}m rms horizontally and 2{micro}m rms vertically. This paper focuses on dynamic orbit stability and describes the all-digital orbit feedback system that has been implemented at the APS. Implementation of the global orbit feedback system is described and its latest performance is presented. Ultimately, the system will provide local feedback at each x-ray source point using installed photon BPMs to measure x-ray beam position and angle directly. Technical challenges associated with local feedback and with dynamics of the associated corrector magnets are described. The unique diagnostic capabilities provided by the APS system are discussed with reference to their use in identifying sources of the underlying orbit motion.

Model-Based State Feedback Controller Design for a Turbocharged Diesel Engine with an EGR System

Directory of Open Access Journals (Sweden)

Tianpu Dong

2015-05-01

Full Text Available This paper describes a method for the control of transient exhaust gas recirculation (EGR systems. Firstly, a state space model of the air system is developed by simplifying a mean value model. The state space model is linearized by using linearization theory and validated by the GT-Power data with an operating point of the diesel engine. Secondly, a state feedback controller based on the intake oxygen mass fraction is designed for EGR control. Since direct measurement of the intake oxygen mass fraction is unavailable on the engine, the estimation method for intake oxygen mass fraction has been proposed in this paper. The control strategy is analyzed by using co-simulation with the Matlab/Simulink and GT-Powers software. Finally, the whole control system is experimentally validated against experimental data of a turbocharged diesel engine. The control effect of the state feedback controller compared with PID controller proved to be further verify the feasibility and advantages of the proposed state feedback controller.

Factors affecting feeling-of-knowing in a medical intelligent tutoring system: the role of immediate feedback as a metacognitive scaffold.

Science.gov (United States)

El Saadawi, Gilan M; Azevedo, Roger; Castine, Melissa; Payne, Velma; Medvedeva, Olga; Tseytlin, Eugene; Legowski, Elizabeth; Jukic, Drazen; Crowley, Rebecca S

2010-03-01

Previous studies in our laboratory have shown the benefits of immediate feedback on cognitive performance for pathology residents using an intelligent tutoring system (ITS) in pathology. In this study, we examined the effect of immediate feedback on metacognitive performance, and investigated whether other metacognitive scaffolds will support metacognitive gains when immediate feedback is faded. Twenty-three participants were randomized into intervention and control groups. For both groups, periods working with the ITS under varying conditions were alternated with independent computer-based assessments. On day 1, a within-subjects design was used to evaluate the effect of immediate feedback on cognitive and metacognitive performance. On day 2, a between-subjects design was used to compare the use of other metacognitive scaffolds (intervention group) against no metacognitive scaffolds (control group) on cognitive and metacognitive performance, as immediate feedback was faded. Measurements included learning gains (a measure of cognitive performance), as well as several measures of metacognitive performance, including Goodman-Kruskal gamma correlation (G), bias, and discrimination. For the intervention group, we also computed metacognitive measures during tutoring sessions. Results showed that immediate feedback in an intelligent tutoring system had a statistically significant positive effect on learning gains, G and discrimination. Removal of immediate feedback was associated with decreasing metacognitive performance, and this decline was not prevented when students used a version of the tutoring system that provided other metacognitive scaffolds. Results obtained directly from the ITS suggest that other metacognitive scaffolds do have a positive effect on G and discrimination, as immediate feedback is faded. We conclude that immediate feedback had a positive effect on both metacognitive and cognitive gains in a medical tutoring system. Other metacognitive scaffolds

Perturbed cooperative-state feedback strategy for model predictive networked control of interconnected systems.

Science.gov (United States)

Tran, Tri; Ha, Q P

2018-01-01

A perturbed cooperative-state feedback (PSF) strategy is presented for the control of interconnected systems in this paper. The subsystems of an interconnected system can exchange data via the communication network that has multiple connection topologies. The PSF strategy can resolve both issues, the sensor data losses and the communication network breaks, thanks to the two components of the control including a cooperative-state feedback and a perturbation variable, e.g., u i =K ij x j +w i . The PSF is implemented in a decentralized model predictive control scheme with a stability constraint and a non-monotonic storage function (ΔV(x(k))≥0), derived from the dissipative systems theory. Numerical simulation for the automatic generation control problem in power systems is studied to illustrate the effectiveness of the presented PSF strategy. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

RF feedback simulation results for PEP-II

International Nuclear Information System (INIS)

Tighe, R.; Corredoura, P.

1995-06-01

A model of the RF feedback system for PEP-II has been developed to provide time-domain simulation and frequency-domain analysis of the complete system. The model includes the longitudinal beam dynamics, cavity fundamental resonance, feedback loops, and the nonlinear klystron operating near saturation. Transients from an ion clearing gap and a reference phase modulation from the longitudinal feedback system are also studied. Growth rates are predicted and overall system stability examined

Feedback implementation options and issues for B factory accelerators

International Nuclear Information System (INIS)

Fox, J.D.; Briggs, D.; Eisen, N.; Hindi, H.; Hosseini, W.; Oxoby, G.; Linscott, I.; Coiro, O.; Ghigo, A.; Serio, M.; Lambertson, G.; Voelker, F.

1992-09-01

The proposed B factory accelerator facilities will require active feedback systems to control multibunch instabilities. These feedback systems must operate in machines with thousands of circulating bunches and with short (2--4 ns) interbunch intervals. The functional requirements for transverse (betatron) and longitudinal (synchrotron) feedback systems are presented. Several possible implementation options are discussed and system requirements developed. Conceptual designs are presented for the PEP II transverse and longitudinal feedback systems

Free-space optics mode-wavelength division multiplexing system using LG modes based on decision feedback equalization

Science.gov (United States)

Amphawan, Angela; Ghazi, Alaan; Al-dawoodi, Aras

2017-11-01

A free-space optics mode-wavelength division multiplexing (MWDM) system using Laguerre-Gaussian (LG) modes is designed using decision feedback equalization for controlling mode coupling and combating inter symbol interference so as to increase channel diversity. In this paper, a data rate of 24 Gbps is achieved for a FSO MWDM channel of 2.6 km in length using feedback equalization. Simulation results show significant improvement in eye diagrams and bit-error rates before and after decision feedback equalization.

Feedback Linearization Controller for a Wind Energy Power System

Directory of Open Access Journals (Sweden)

Muthana Alrifai

2016-09-01

Full Text Available This paper deals with the control of a doubly-fed induction generator (DFIG-based variable speed wind turbine power system. A system of eight ordinary differential equations is used to model the wind energy conversion system. The generator has a wound rotor type with back-to-back three-phase power converter bridges between its rotor and the grid; it is modeled using the direct-quadrature rotating reference frame with aligned stator flux. An input-state feedback linearization controller is proposed for the wind energy power system. The controller guarantees that the states of the system track the desired states. Simulation results are presented to validate the proposed control scheme. Moreover, further simulation results are shown to investigate the robustness of the proposed control scheme to changes in some of the parameters of the system.

Interference Alignment-based Precoding and User Selection with Limited Feedback in Two-cell Downlink Multi-user MIMO Systems

Directory of Open Access Journals (Sweden)

Yin Zhu

2016-05-01

Full Text Available Interference alignment (IA is a new approach to address interference in modern multiple-input multiple-out (MIMO cellular networks in which interference is an important factor that limits the system throughput. System throughput in most IA implementation schemes is significantly improved only with perfect channel state information and in a high signal-to-noise ratio (SNR region. Designing a simple IA scheme for the system with limited feedback and investigating system performance at a low-to-medium SNR region is important and practical. This paper proposed a precoding and user selection scheme based on partial interference alignment in two-cell downlink multi-user MIMO systems under limited feedback. This scheme aligned inter-cell interference to a predefined direction by designing user’s receive antenna combining vectors. A modified singular value decomposition (SVD-based beamforming method and a corresponding user-selection algorithm were proposed for the system with low rate limited feedback to improve sum rate performance. Simulation results show that the proposed scheme achieves a higher sum rate than traditional schemes without IA. The modified SVD-based beamforming scheme is also superior to the traditional zero-forcing beamforming scheme in low-rate limited feedback systems. The proposed partial IA scheme does not need to collaborate between transmitters and joint design between the transmitter and the users. The scheme can be implemented with low feedback overhead in current MIMO cellular networks.

[Development of an Analgesia Therapy System for Delivery Based on Bio-feedback Transcuataneous Electrical Nerve Stimulation].

Science.gov (United States)

Deng Songbo; Lu Yaosheng; Fang, Kun; Qin, Ruyi; Lin, Zhan

2015-06-01

Transcuataneous electrical nerve stimulation (TENS) analgesia as a non-drug method has received people's more and more attention recently. Considering problems of existing products, such as unstable performance and unsatisfied effectiveness, we developed a new analgesia therapy system for delivery based on bio-feedback TENS in our laboratory. We proposed a new idea for stimulation signal design, that is, we modulated a middle frequency signal by a traditional low frequency TENS wave in the new system. We designed different prescription waves for pain relief during a uterine contraction or massage between contractions. In the end, a bio-feedback TENS method was proposed, in which the waveforms of stimulation signals were selected and their parameters were modified automatically based on feedback from uterine pressure, etc. It was proved through quality tests and clinical trials that the system had good performance and satisfied analgesia effectiveness.

To Stabilize Power Systems from Various Kind of Oscillations using a State Feedback Controller

International Nuclear Information System (INIS)

Afridi, M. A.

2012-01-01

Damping of electromechanical oscillations in power systems is one of the major concerns in the operation of power system since many years. These oscillations cause improper of the power system incorporating losses. This thesis work presents the coordinated AVR+PSS structure, called the Desensitized four loops Regulator, designed to damp these oscillations in the power system. It is shown here that it is possible to transform the structure of this controller into any standard IEEE AVR+PSS structure. The AVR+PSS structure obtained through this structure is efficient to damp out many types of oscillations present in the Power system. These models are to be incorporated with the generator models to get a power system model with state feedback control. On simulating the system in Simulink with the controllers we have obtained the power system model with state feedback control and observed that how these controllers are helpful in damping the oscillations. (author)

Designing Student Feedback System within the Course Evaluation Process: Dokuz Eylül University Case Study

Directory of Open Access Journals (Sweden)

Muhammet DAMAR

2017-04-01

Full Text Available The Bologna Process at National Higher Education Programs initiated a series of studies regarding the assessment and evaluation of quality in higher education. Dokuz Eylül University has taken this initiation into a primary concern to develop a methodology for the measurement of quality in undergraduate education. Besides the existing systems on this subject at Dokuz Eylül University, substantial progress was recently made by developing innovative sub-systems aiming further improvements. As one of the most important stakeholders, the feedback from students about the quality of the courses was selected as the major concern and a Student Course Feedback System was developed for this purpose. As an exemplary case study, this reveals how the Student Course Feedback System was designed, the process, the technologies used, the problems and constraints encountered, and the roadmap that can be followed by other universities. Dokuz Eylül University has interiorized this process as a corporate culture by directing instructors to make improvements in the courses with respect to the outputs of the evaluation forms, including questions about learning outcomes, instructors, and physical conditions. The integrated design of the Student Course Feedback System with the existing information systems has enabled management to implement a course evaluation system comprising the trilogy of students, instructors, and courses as a whole. The existence of such an assessment process supports the principles of continuous improvement and helps to establish the factual decision making process as an important milestone on the roadmap for a living quality assurance system.

Feedback dynamics and cell function: Why systems biology is called Systems Biology.

Science.gov (United States)

Wolkenhauer, Olaf; Mesarovic, Mihajlo

2005-05-01

A new paradigm, like Systems Biology, should challenge the way research has been conducted previously. This Opinion article aims to present Systems Biology, not as the application of engineering principles to biology but as a merger of systems- and control theory with molecular- and cell biology. In our view, the central dogma of Systems Biology is that it is system dynamics that gives rise to the functioning and function of cells. The concepts of feedback regulation and control of pathways and the coordination of cell function are emphasized as an important area of Systems Biology research. The hurdles and risks for this area are discussed from the perspective of dynamic pathway modelling. Most of all, the aim of this article is to promote mathematical modelling and simulation as a part of molecular- and cell biology. Systems Biology is a success if it is widely accepted that there is nothing more practical than a good theory.

Global orbit feedback utilizing analog and digital technologies

International Nuclear Information System (INIS)

Singh, O.; Tang, Y.; Ramamoorthy, S.; Krinsky, S.; Yu, L.H.

1997-01-01

At the NSLS, an analog global orbit feedback system is used in regular operations, and a digital global orbit feedback system is available in machine physics studies on the X-Ray Ring. Here, the authors discuss the relative merits of utilizing analog and digital technology in orbit feedback. Results of experiments are reported characterizing the performance of the analog and digital systems when operated individually or together. They give their thoughts on plans for future development of the orbit feedback systems at the NSLS

Feedback control of edge turbulence in a tokamak

International Nuclear Information System (INIS)

Kan, Zhai; Yi-zhi, Wen; Chang-xuan, Yu; Wan-dong, Liu; Chao, Wang; Ge, Zhuang; Kan, Zhai; Zhi-Zhan, Yu

1997-01-01

An experiment on feedback control of edge turbulence has been undertaken on the KT-5C tokamak. The results indicate that the edge turbulence could be suppressed or enhanced depending on the phase shift of the feedback network. In a typical case of 90 degree phase shift feedback, the turbulence amplitudes of both T e and n e were reduced by about 25% when the gain of the feedback network was 15. Correspondingly the radial particle flux decreased to about 75% level of the background. Through bispectral analysis it is found that there exists a substantial nonlinear coupling between various modes comprised in edge turbulence, especially in the frequency range from about 10 kHz to 100 kHz, which contains the large part of the edge turbulence energy in KT-5C tokamak. In particular, by actively controlling the turbulence amplitude using feedback, a direct experimental evidence of the link between the nonlinear wave-wave coupling over the whole spectrum in turbulence, the saturated turbulence amplitude, and the radial particle flux was provided. copyright 1997 The American Physical Society

Design Of Combined Stochastic Feedforward/Feedback Control

Science.gov (United States)

Halyo, Nesim

1989-01-01

Methodology accommodates variety of control structures and design techniques. In methodology for combined stochastic feedforward/feedback control, main objectives of feedforward and feedback control laws seen clearly. Inclusion of error-integral feedback, dynamic compensation, rate-command control structure, and like integral element of methodology. Another advantage of methodology flexibility to develop variety of techniques for design of feedback control with arbitrary structures to obtain feedback controller: includes stochastic output feedback, multiconfiguration control, decentralized control, or frequency and classical control methods. Control modes of system include capture and tracking of localizer and glideslope, crab, decrab, and flare. By use of recommended incremental implementation, control laws simulated on digital computer and connected with nonlinear digital simulation of aircraft and its systems.

A unified approach to global and local beam position feedback

International Nuclear Information System (INIS)

Chung, Y.

1994-01-01

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams for the storage ring. The global feedback system uses 40 BPMs and 40 correctors per plane. Singular value decomposition (SVD) of the response matrix is used for closed orbit correction. The local feedback system uses two X-ray BPMS, two rf BPMS, and the four-magnet local bump to control the angle and displacement of the X-ray beam from a bending magnet or an insertion device. Both the global and local feedback systems are based on digital signal processing (DSP) running at 4-kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. In this paper, we will discuss resolution of the conflict among multiple local feedback systems due to local bump closure error and decoupling of the global and local feedback systems to maximize correction efficiency. In this scheme, the global feedback system absorbs the local bump closure error and the local feedback systems compensate for the effect of global feedback on the local beamlines. The required data sharing between the global and local feedback systems is done through the fiber-optically networked reflective memory

Pressure Feedback in Fluid Power Systems--Active Damping Explained and Exemplified

DEFF Research Database (Denmark)

Pedersen, Henrik Clemmensen; Andersen, Torben O.

2018-01-01

Fluid power systems are inherently nonlinear and typically suffer from very poor damping. Despite these characteristics, it is not uncommon that traditional linear type controllers are applied. This typically results in conservative adjustment of the controllers, or when more advanced controllers...... a given system, and how to adjust the parameters of the pressure feedback to obtain the best results. This is done for both a traditional symmetric cylinder servo system and a system with a differential cylinder using both pressure and nonpressure compensated proportional valves. Based on the presented...

Feedback System Control Optimized Electrospinning for Fabrication of an Excellent Superhydrophobic Surface.

Science.gov (United States)

Yang, Jian; Liu, Chuangui; Wang, Boqian; Ding, Xianting

2017-10-13

Superhydrophobic surface, as a promising micro/nano material, has tremendous applications in biological and artificial investigations. The electrohydrodynamics (EHD) technique is a versatile and effective method for fabricating micro- to nanoscale fibers and particles from a variety of materials. A combination of critical parameters, such as mass fraction, ratio of N, N-Dimethylformamide (DMF) to Tetrahydrofuran (THF), inner diameter of needle, feed rate, receiving distance, applied voltage as well as temperature, during electrospinning process, to determine the morphology of the electrospun membranes, which in turn determines the superhydrophobic property of the membrane. In this study, we applied a recently developed feedback system control (FSC) scheme for rapid identification of the optimal combination of these controllable parameters to fabricate superhydrophobic surface by one-step electrospinning method without any further modification. Within five rounds of experiments by testing totally forty-six data points, FSC scheme successfully identified an optimal parameter combination that generated electrospun membranes with a static water contact angle of 160 degrees or larger. Scanning electron microscope (SEM) imaging indicates that the FSC optimized surface attains unique morphology. The optimized setup introduced here therefore serves as a one-step, straightforward, and economic approach to fabricate superhydrophobic surface with electrospinning approach.

Free-space optics mode-wavelength division multiplexing system using LG modes based on decision feedback equalization

Directory of Open Access Journals (Sweden)

Amphawan Angela

2017-01-01

Full Text Available A free-space optics mode-wavelength division multiplexing (MWDM system using Laguerre-Gaussian (LG modes is designed using decision feedback equalization for controlling mode coupling and combating inter symbol interference so as to increase channel diversity. In this paper, a data rate of 24 Gbps is achieved for a FSO MWDM channel of 2.6 km in length using feedback equalization. Simulation results show significant improvement in eye diagrams and bit-error rates before and after decision feedback equalization.

The Potential of User Feedback Through the Iterative Refining of Queries in an Image Retrieval System

NARCIS (Netherlands)

Ben Moussa, Maher; Pasch, Marco; Hiemstra, Djoerd; van der Vet, P.E.; Huibers, Theo W.C.; Marchand-Maillet, Stephane; Bruno, Eric; Nürnberger, Andreas; Detyniecki, Marcin

2007-01-01

Inaccurate or ambiguous expressions in queries lead to poor results in information retrieval. We assume that iterative user feedback can improve the quality of queries. To this end we developed a system for image retrieval that utilizes user feedback to refine the user’s search query. This is done