ROBUST STABILITY ANALYSIS FOR RAILWAY VEHICLE SYSTEMS
Wang Yong; Zeng Jing; Cao Dengqing
2003-01-01
The lateral stability for railway vehicle dynamic system with uncertain parameters and nonlinear uncertain force vector is studied by using the Lyapunov stability theory. A robust stability condition for the considered system is derived, and the obtained stability bounds are not necessarily symmetric with respect to the origin in the parameter space. The lateral stability analysis for a railway bogie model is analyzed by using the proposed approach. The symmetric and asymmetric results are both given and the influence of the adjustable parameter ( on the stability bounds is also discussed. With the help of the proposed method, the robust stability analysis can provide a reference for the design of the railway vehicle systems.
A New Approach for Aeroelastic Robust Stability Analysis
Wu Zhigang; Yang Chao
2008-01-01
Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An approach for aeroelastic robust stability analysis taking into account the perturbations of structural mass and stiffness is developed. Applying the perturbation method and harmonic unsteady aerodynamic forces, the frequency-domain linear fractal transformation (LFT) representation of pertorbed aeroelastic system is modeled.Then, the robust stability is analyzed by using the structured singular value μ-method. The numerical results of a bi-spar wing show its effectiveness and low computational time in dealing with the robust problems with mass and stiffness perturbations. In engineering analysis for solving aeroelastic problems, the robust approach can be applied to flutter analysis for airplane with the fuel load variation and taking the damage conditions into consideration.
Analytic robust stability analysis of SVD orbit feedback
Pfingstner, Jürgen
2012-01-01
Orbit feedback controllers are indispensable for the operation of modern particle accelerators. Many such controllers are based on the decoupling of the inputs and outputs of the system to be controlled with the help of the singular value decomposition (SVD controller). It is crucial to verify the stability of SVD controllers, also in the presence of mismatches between the used accelerator model and the real machine (robust stability problem). In this paper, analytical criteria for guaranteed stability margins of SVD orbit feedback systems for three different types of model mismatches are presented: scaling errors of actuators and BPMs (beam position monitors) and additive errors of the orbit response matrix. For the derivation of these criteria, techniques from robust control theory have been used, e.g the small gain theorem. The obtained criteria can be easily applied directly to other SVD orbit feedback systems. As an example, the criteria were applied to the orbit feedback system of the Compact Linear ...
Robust Stability Analysis of Nonlinear Switched Systems with Filippov Solutions
Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal
2012-01-01
. Based on the theory of differential inclusions, a Lyapunov stability theorem is brought forward. These results are also extended to autonomous switched systems subject to polytopic uncertainty. Furthermore, the proposed stability theorems are reformulated using the sum of squares decomposition method...... which provides sufficient means to construct the corresponding Lyapunov functions via available semi-definite programming techniques....
IQC-based robust stability analysis for LPV control of doubly-fed induction generators
Tien, H. N.; Scherer, C. W.; Scherpen, J. M. A.
2008-01-01
Parameters of electrical machines are usually varying with time in a smooth way due to changing operating conditions, such as variations in the machine temperature and/or the magnetic saturation. This paper is concerned with robust stability analysis of controlled Doubly-Fed Induction Generators (DF
Robust exponential stability analysis of a larger class of discrete-time recurrent neural networks
无
2007-01-01
The robust exponential stability of a larger class of discrete-time recurrent neural networks (RNNs) is explored in this paper. A novel neural network model, named standard neural network model (SNNM), is introduced to provide a general framework for stability analysis of RNNs. Most of the existing RNNs can be transformed into SNNMs to be analyzed in a unified way.Applying Lyapunov stability theory method and S-Procedure technique, two useful criteria of robust exponential stability for the discrete-time SNNMs are derived. The conditions presented are formulated as linear matrix inequalities (LMIs) to be easily solved using existing efficient convex optimization techniques. An example is presented to demonstrate the transformation procedure and the effectiveness of the results.
Robust Stability Analysis of the Space Launch System Control Design: A Singular Value Approach
Pei, Jing; Newsome, Jerry R.
2015-01-01
Classical stability analysis consists of breaking the feedback loops one at a time and determining separately how much gain or phase variations would destabilize the stable nominal feedback system. For typical launch vehicle control design, classical control techniques are generally employed. In addition to stability margins, frequency domain Monte Carlo methods are used to evaluate the robustness of the design. However, such techniques were developed for Single-Input-Single-Output (SISO) systems and do not take into consideration the off-diagonal terms in the transfer function matrix of Multi-Input-Multi-Output (MIMO) systems. Robust stability analysis techniques such as H(sub infinity) and mu are applicable to MIMO systems but have not been adopted as standard practices within the launch vehicle controls community. This paper took advantage of a simple singular-value-based MIMO stability margin evaluation method based on work done by Mukhopadhyay and Newsom and applied it to the SLS high-fidelity dynamics model. The method computes a simultaneous multi-loop gain and phase margin that could be related back to classical margins. The results presented in this paper suggest that for the SLS system, traditional SISO stability margins are similar to the MIMO margins. This additional level of verification provides confidence in the robustness of the control design.
Computational analysis of a stability robustness margin for structured real-parameter perturbations
Wedell, Evan; Chuang, C.-H.; Wie, Bong
1989-01-01
An efficient computational method is presented for stability robustness analysis with structured real-parameter perturbations. A generic model of a class of uncertain dynamical systems is used as an example. The parameter uncertainty is characterized by a real scalar, epsilon. Multilinearity of the closed-loop characteristic polynomial is exploited to permit application of the mapping theorem to calculate the stability robustness margin. It is found that sensitive geometry of the stability boundary in the epsilon, omega-plane renders problematic the calculation of the minimum epsilon as a function of omega. This difficulty is avoided by calculating the minimum distance to the image of the uncertainty domain over omega as a function of epsilon. It is also shown that a certain class of uncertain dynamical systems has the required multilinearity property and are thus amenable to the proposed technique.
Robust stability analysis of uncertain discrete-time systems with state delay
任正云; 张立群; 邵惠鹤
2004-01-01
The sufficient conditions of stability for uncertain discrete-time systems with state delay have been proposed by some researchers in the past few years, yet these results may be conservative in application. The stability analysis of these systems is discussed, and the necessary and sufficient condition of stability is derived by method other than constructing Lyapunov function and solving Riccati inequality. The root locations of system characteristic polynomial, which is obtained by augmentation approach and Laplace expansion, determine the stability of uncertain discrete-time systems with state delay, the system is stable if and only if all roots lie within the unit circle. In order to analyze robust stability of system characteristic polynomial effectively, Kharitonov theorem and edge theorem are applied. Example shows the practicability of these methods.
Robust Stability Analysis and Synthesis for Switched Discrete-Time Systems with Time Delay
Liguo Zhang
2010-01-01
Full Text Available The problems of robust stability analysis and synthesis for a class of uncertain switched time-delay systems with polytopic type uncertainties are addressed. Based on the constructive use of an appropriate switched Lyapunov function, sufficient linear matrix inequalities (LMIs conditions are investigated to make such systems a uniform quadratic stability with an L2-gain smaller than a given constant level. System synthesis is to design switched feedback schemes, whether based on state, output measurements, or by using dynamic output feedback, to guarantee that the corresponding closed-loop system satisfies the LMIs conditions. Two numerical examples are provided that demonstrate the efficiency of this approach.
Real-Time Stability Margin Measurements for X-38 Robustness Analysis
Bosworth, John T.; Stachowiak, Susan J.
2005-01-01
A method has been developed for real-time stability margin measurement calculations. The method relies on a tailored-forced excitation targeted to a specific frequency range. Computation of the frequency response is matched to the specific frequencies contained in the excitation. A recursive Fourier transformation is used to make the method compatible with real-time calculation. The method was incorporated into the X-38 nonlinear simulation and applied to an X-38 robustness test. X-38 stability margins were calculated for different variations in aerodynamic and mass properties over the vehicle flight trajectory. The new method showed results comparable to more traditional stability analysis techniques, and at the same time, this new method provided coverage that is more complete and increased efficiency.
Robust Stability Clearance of Flight Control Law Based on Global Sensitivity Analysis
Liuli Ou
2014-01-01
Full Text Available To validate the robust stability of the flight control system of hypersonic flight vehicle, which suffers from a large number of parametrical uncertainties, a new clearance framework based on structural singular value (μ theory and global uncertainty sensitivity analysis (SA is proposed. In this framework, SA serves as the preprocess of uncertain model to be analysed to help engineers to determine which uncertainties affect the stability of the closed loop system more slightly. By ignoring these unimportant uncertainties, the calculation of μ can be simplified. Instead of analysing the effect of uncertainties on μ which involves solving optimal problems repeatedly, a simpler stability analysis function which represents the effect of uncertainties on closed loop poles is proposed. Based on this stability analysis function, Sobol’s method, the most widely used global SA method, is extended and applied to the new clearance framework due to its suitability for system with strong nonlinearity and input factors varying in large interval, as well as input factors subjecting to random distributions. In this method, the sensitive indices can be estimated via Monte Carlo simulation conveniently. An example is given to illustrate the efficiency of the proposed method.
Su Weiwei; Chen Yiming
2008-01-01
Delay-dependent robust stability of cellular neural networks with time-varying discrete and distributed time-varying delays is considered. Based on Lyapunov stability theory and the linear matrix inequality (LMIs) technique, delay-dependent stability criteria are derived in terms of LMIs avoiding bounding certain cross terms, which often leads to conservatism. The effectiveness of the proposed stability criteria and the improvement over the existing results are illustrated in the numerical examples.
A New Robust Stabilization Analysis Result for Uncertain Systems with Time-Varying Delay
WANG Zhong-sheng; WANG Dong-yun; LIAO Xiao-xin
2005-01-01
The robust stabilization problem for uncertain systems with time-varying delay has been discussed. A new sufficient criterion is obtained to guarantee the closed-loop system robust stabilizable. The controller gain matrix is included in a Hamiltonian matrix. The Hamiltonian matrix can be constructed by the boundedness of the uncertainties. Some examples are given to illustrate the feasibility of the criterion.
Robust stability analysis of singular linear system with delay and parameter uncertainty
Renxin ZHONG; Zhi YANG
2005-01-01
This paper deals with the problem of robust stability for continuous-time singular systems with state delay and parameter uncertainty.The uncertain singular systems with delay considered in this paper are assumed to be regular and impulse free.By decomposing the systems into slow and fast subsystems,a robust delay-dependent asymptotic stability criteria based on linear matrix inequality is proposed,which is derived by using Lyapunov-Krasovskii functionals,neither model transformation nor bounding for cross terms is required in the derivation of our delay-dependent result.The robust delay-dependent stability criterion proposed in this paper is a sufficient condition.Finally,numerical examples and Matlab simulation are provided to illustrate the effectiveness of the proposed method.
Quantum Popov robust stability analysis of an optical cavity containing a saturated Kerr medium
Petersen, Ian R.
2017-09-01
This paper applies results of the robust stability of nonlinear quantum systems to a system consisting of an optical cavity containing a saturated Kerr medium. The system is characterised by a Hamiltonian operator that contains a non-quadratic term involving a quartic function of the annihilation and creation operators. A saturated version of the Kerr nonlinearity leads to a sector-bounded nonlinearity that enables a quantum small gain theorem to be applied to this system in order to analyse its stability. Also, a non-quadratic version of a quantum Popov stability criterion is presented and applied to analyse the stability of this system.
无
2011-01-01
In this paper,the robust stability issue of switched uncertain multidelay systems resulting from actuator failures is considered.Based on the average dwell time approach,a set of suitable switching signals is designed by using the total activation time ratio between the stable subsystem and the unstable one.It is first proven that the resulting closed-loop system is robustly exponentially stable for some allowable upper bound of delays if the nominal system with zero delay is exponentially stable under thes...
SHAO, Xueguang; CHEN, Da; XU, Heng; LIU, Zhichao; CAI, Wensheng
2009-01-01
Partial least-squares (PLS) regression has been presented as a powerful tool for spectral quantitative measure- ment. However, the improvement of the robustness and stability of PLS models is still needed, because it is difficult to build a stable model when complex samples are analyzed or outliers are contained in the calibration data set. To achieve the purpose, a robust ensemble PLS technique based on probability resampling was proposed, which is named RE-PLS. In the proposed method, a probability is firstly obtained for each calibration sample from its resid- ual in a robust regression. Then, multiple PLS models are constructed based on probability resampling. At last, the multiple PLS models are used to predict unknown samples by taking the average of the predictions from the multi- ple models as final prediction result. To validate the effectiveness and universality of the proposed method, it was applied to two different sets of NIR spectra. The results show that RE-PLS can not only effectively avoid the inter- ference of outliers but also enhance the precision of prediction and the stability of PLS regression. Thus, it may pro- vide a useful tool for multivariate calibration with multiple outliers.
S. Lakshmanan; P. Balasubramaniarn
2011-01-01
This paper studies the problem of linear matrix inequality(LMI)approach to robust stability analysis for stochastic neural networks with a time-varying delay. By developing a delay decomposition approach, the information of the delayed plant states can be taken into full consideration. Based on the new Lyapunov-Krasovskii functional, some inequality techniques and stochastic stability theory, new delay-dependent stability criteria are obtained in terms of LMIs. The proposed results prove the less conservatism, which are realized by choosing new Lyapunov matrices in the decomposed integral intervals. Finally, numerical examples are provided to demonstrate the less conservatism and effectiveness of the proposed LMI method.
The robust regulation problem with robust stability
Cevik, M.K.K.; Schumacher, J.M.
1999-01-01
Among the most common purposes of control are the tracking of reference signals and the rejection of disturbance signals in the face of uncertainties. The related design problem is called the `robust regulation problem'. Here we investigate the trade-off between the robust regulation constraint and
Stability and robustness analysis of a linear time-periodic system subjected to random perturbations
Redkar, Sangram; Liu, J.; Sinha, S. C.
2012-03-01
In this work, new methods of guaranteeing the stability of linear time periodic dynamical systems with stochastic perturbations are presented. In the approaches presented here, the Lyapunov-Floquet (L-F) transformation is applied first so that the linear time-periodic part of the equations becomes time-invariant. For the linear time periodic system with stochastic perturbations, a stability theorem and related corollary have been suggested using the results previously obtained by Infante. This technique is not only applicable to systems with stochastic parameters but also to systems with deterministic variation in parameters. Some illustrative examples are presented to show the practical applications. These methods can be used to investigate the degree of robustness and design controllers for systems with time periodic coefficients subjected to random perturbations.
Faydasicok, Ozlem; Arik, Sabri
2013-08-01
The main problem with the analysis of robust stability of neural networks is to find the upper bound norm for the intervalized interconnection matrices of neural networks. In the previous literature, the major three upper bound norms for the intervalized interconnection matrices have been reported and they have been successfully applied to derive new sufficient conditions for robust stability of delayed neural networks. One of the main contributions of this paper will be the derivation of a new upper bound for the norm of the intervalized interconnection matrices of neural networks. Then, by exploiting this new upper bound norm of interval matrices and using stability theory of Lyapunov functionals and the theory of homomorphic mapping, we will obtain new sufficient conditions for the existence, uniqueness and global asymptotic stability of the equilibrium point for the class of neural networks with discrete time delays under parameter uncertainties and with respect to continuous and slope-bounded activation functions. The results obtained in this paper will be shown to be new and they can be considered alternative results to previously published corresponding results. We also give some illustrative and comparative numerical examples to demonstrate the effectiveness and applicability of the proposed robust stability condition.
Robust stability analysis of a class of neural networks with discrete time delays.
Faydasicok, Ozlem; Arik, Sabri
2012-05-01
This paper studies the existence, uniqueness and global asymptotic stability of the equilibrium point for the class of neural networks with discrete constant time delays under parameter uncertainties. The class of the neural network considered in this paper employs the activation functions which are assumed to be continuous and slope-bounded but not required to be bounded or differentiable. We conduct a stability analysis by exploiting the stability theory of Lyapunov functionals and the theory of Homomorphic mapping to derive some easily verifiable sufficient conditions for existence, uniqueness and global asymptotic stability of the equilibrium point. The conditions obtained mainly establish some time-independent relationships between the network parameters of the neural network. We make a detailed comparison between our results and the previously published corresponding results. This comparison proves that our results are new and improve and generalize the results derived in the past literature. We also give some illustrative numerical examples to show the effectiveness and applicability of our proposed stability results.
Robust Stabilization Analysis for Uncertain Systems with Time-Varying Delays
WANG Zhong-sheng; WANG Dong-yun; SHEN Yi
2004-01-01
In this paper, the stabilization problem for uncertain systems with time-varying delays both in state and control are discussed. A stabilization criterion is obtained to guarantee the quadratic stability of the closed-loop system. The controller gain matrix is included in an Hamiltonian matrix, which is easily constructed by the boundedness of the uncertainties.
Probabilistic robust stabilization of fractional order systems with interval uncertainty.
Alagoz, Baris Baykant; Yeroglu, Celaleddin; Senol, Bilal; Ates, Abdullah
2015-07-01
This study investigates effects of fractional order perturbation on the robust stability of linear time invariant systems with interval uncertainty. For this propose, a probabilistic stability analysis method based on characteristic root region accommodation in the first Riemann sheet is developed for interval systems. Stability probability distribution is calculated with respect to value of fractional order. Thus, we can figure out the fractional order interval, which makes the system robust stable. Moreover, the dependence of robust stability on the fractional order perturbation is analyzed by calculating the order sensitivity of characteristic polynomials. This probabilistic approach is also used to develop a robust stabilization algorithm based on parametric perturbation strategy. We present numerical examples demonstrating utilization of stability probability distribution in robust stabilization problems of interval uncertain systems.
Hybrid Dynamical Systems Modeling, Stability, and Robustness
Goebel, Rafal; Teel, Andrew R
2012-01-01
Hybrid dynamical systems exhibit continuous and instantaneous changes, having features of continuous-time and discrete-time dynamical systems. Filled with a wealth of examples to illustrate concepts, this book presents a complete theory of robust asymptotic stability for hybrid dynamical systems that is applicable to the design of hybrid control algorithms--algorithms that feature logic, timers, or combinations of digital and analog components. With the tools of modern mathematical analysis, Hybrid Dynamical Systems unifies and generalizes earlier developments in continuous-time and discret
Requejo, Rubén J; Cuesta, José A; Arenas, Alex; 10.1103/PhysRevE.86.026105
2012-01-01
The emergence and promotion of cooperation are two of the main issues in evolutionary game theory, as cooperation is amenable to exploitation by defectors, which take advantage of cooperative individuals at no cost, dooming them to extinction. It has been recently shown that the existence of purely destructive agents (termed jokers) acting on the common enterprises (public goods games) can induce stable limit cycles among cooperation, defection, and destruction when infinite populations are considered. These cycles allow for time lapses in which cooperators represent a relevant fraction of the population, providing a mechanism for the emergence of cooperative states in nature and human societies. Here we study analytically and through agent-based simulations the dynamics generated by jokers in finite populations for several selection rules. Cycles appear in all cases studied, thus showing that the joker dynamics generically yields a robust cyclic behavior not restricted to infinite populations. We also comput...
Robust integral stabilization of regular linear systems
XU Chengzheng; FENG Dexing
2004-01-01
We consider regular systems with control and observation. We prove some necessary and sufficient condition for an exponentially stable regular system to admit an integral stabilizing controller. We propose also some robust integral controllers when they exist.
Robust Schur Stability and Robust H^2 Performance
Stoustrup, Jakob; Zhao, K.-Y.
1996-01-01
In this paper we address the problems of robust stability androbust QTR H^2 performance for uncertain discrete time systemswith nonlinear parametric uncertainties. We consider two families ofsystems with parametric uncertainties described by state space modelswhich offer a fairly general represen...
Robust Schur Stability and Robust H^2 Performance
Stoustrup, Jakob; Zhao, K.-Y.
1996-01-01
In this paper we address the problems of robust stability androbust QTR H^2 performance for uncertain discrete time systemswith nonlinear parametric uncertainties. We consider two families ofsystems with parametric uncertainties described by state space modelswhich offer a fairly general...... representation of most uncertain systemswith one or two parameters (the approach can be extended to more parameters).For these two families we obtain explicit expressions for the Schurstability radius and for the QTR H^2 robust performance radiusin the case of uncertainties with a single parameter. Moreover, we...
G. Chesi
2013-01-01
This paper addresses the problem of establishing robust asymptotical stability of discrete-time systems affected by time-varying parametric uncertainty. Specifically, it is supposed that the coefficients of the system depend linearly on the uncertainty, and that the uncertainty is confined into a polytope. In the continuous-time case, the problem can be addressed by imposing that the system admits a common homogeneous polynomial Lyapunov function (HPLF) at the vertices of the polytope. Unfort...
Stability Constraints for Robust Model Predictive Control
Amanda G. S. Ottoni
2015-01-01
Full Text Available This paper proposes an approach for the robust stabilization of systems controlled by MPC strategies. Uncertain SISO linear systems with box-bounded parametric uncertainties are considered. The proposed approach delivers some constraints on the control inputs which impose sufficient conditions for the convergence of the system output. These stability constraints can be included in the set of constraints dealt with by existing MPC design strategies, in this way leading to the “robustification” of the MPC.
Robust stability of interval parameter matrices
无
2000-01-01
This note is devoted to the problem of robust stability of interval parameter matrices. Based on some basic facts relating the H∞ norm of a transfer function to the Riccati matrix inequality and Hamilton matrix, several test conditions with parameter perturbation bounds are obtained.
Robust fuzzy logic stabilization with disturbance elimination.
Danapalasingam, Kumeresan A
2014-01-01
A robust fuzzy logic controller is proposed for stabilization and disturbance rejection in nonlinear control systems of a particular type. The dynamic feedback controller is designed as a combination of a control law that compensates for nonlinear terms in a control system and a dynamic fuzzy logic controller that addresses unknown model uncertainties and an unmeasured disturbance. Since it is challenging to derive a highly accurate mathematical model, the proposed controller requires only nominal functions of a control system. In this paper, a mathematical derivation is carried out to prove that the controller is able to achieve asymptotic stability by processing state measurements. Robustness here refers to the ability of the controller to asymptotically steer the state vector towards the origin in the presence of model uncertainties and a disturbance input. Simulation results of the robust fuzzy logic controller application in a magnetic levitation system demonstrate the feasibility of the control design.
A numerical investigation for robust stability of fractional-order uncertain systems.
Senol, Bilal; Ates, Abdullah; Alagoz, B Baykant; Yeroglu, Celaleddin
2014-03-01
This study presents numerical methods for robust stability analysis of closed loop control systems with parameter uncertainty. Methods are based on scan sampling of interval characteristic polynomials from the hypercube of parameter space. Exposed-edge polynomial sampling is used to reduce the computational complexity of robust stability analysis. Computer experiments are used for demonstration of the proposed robust stability test procedures.
Rider, William, E-mail: wjrider@sandia.gov [Sandia National Laboratories, Center for Computing Research, Albuquerque, NM 87185 (United States); Witkowski, Walt [Sandia National Laboratories, Verification and Validation, Uncertainty Quantification, Credibility Processes Department, Engineering Sciences Center, Albuquerque, NM 87185 (United States); Kamm, James R. [Los Alamos National Laboratory, Methods and Algorithms Group, Computational Physics Division, Los Alamos, NM 87545 (United States); Wildey, Tim [Sandia National Laboratories, Center for Computing Research, Albuquerque, NM 87185 (United States)
2016-02-15
We introduce a new methodology for inferring the accuracy of computational simulations through the practice of solution verification. We demonstrate this methodology on examples from computational heat transfer, fluid dynamics and radiation transport. Our methodology is suited to both well- and ill-behaved sequences of simulations. Our approach to the analysis of these sequences of simulations incorporates expert judgment into the process directly via a flexible optimization framework, and the application of robust statistics. The expert judgment is systematically applied as constraints to the analysis, and together with the robust statistics guards against over-emphasis on anomalous analysis results. We have named our methodology Robust Verification. Our methodology is based on utilizing multiple constrained optimization problems to solve the verification model in a manner that varies the analysis' underlying assumptions. Constraints applied in the analysis can include expert judgment regarding convergence rates (bounds and expectations) as well as bounding values for physical quantities (e.g., positivity of energy or density). This approach then produces a number of error models, which are then analyzed through robust statistical techniques (median instead of mean statistics). This provides self-contained, data and expert informed error estimation including uncertainties for both the solution itself and order of convergence. Our method produces high quality results for the well-behaved cases relatively consistent with existing practice. The methodology can also produce reliable results for ill-behaved circumstances predicated on appropriate expert judgment. We demonstrate the method and compare the results with standard approaches used for both code and solution verification on well-behaved and ill-behaved simulations.
Fang-Xiang Wu
2011-08-01
The study of stability is essential for designing or controlling genetic regulatory networks. This paper addresses global and robust stability of genetic regulatory networks with time delays and parameter uncertainties. Most existing results on this issue are based on the linear matrix inequalities (LMIs) approach, which results in checking the existence of a feasible solution to high dimensional LMIs. Based on M-matrix theory, we will present several novel global stability conditions for genetic regulatory networks with time-varying and time-invariant delays. All of these stability conditions are given in terms of M-matrices, for which there are many and very easy ways to be verified. Then, we extend these results to genetic regulatory networks with time delays and parameter uncertainties. To illustrate the effectiveness of our theoretical results, several genetic regulatory networks are analyzed. Compared with existing results in the literature, we also show that our results are less conservative than existing ones with these illustrative genetic regulatory networks.
Xianming ZHANG; Min WU; Jinhua SHE; Dongsheng HAN
2007-01-01
This paper addresses the problems of the robust stability and robust stabilization of a discrete-time system with polytopic uncertainties.A new and simple method is presented to directly decouple the Lyapunov matrix and the system dynamic matrix.Combining this method with the parameter-dependent Lyapunov function approach yields new criteria that include some existing ones as special cases.A numerical example illustrates the improvement over the existing ones.
Stabilization of nonlinear systems based on robust control Lyapunov function
CAI Xiu-shan; HAN Zheng-zhi; LU Gan-yun
2007-01-01
This paper deals with the robust stabilization problem for a class of nonlinear systems with structural uncertainty. Based on robust control Lyapunov function, a sufficient and necessary condition for a function to be a robust control Lyapunov function is given. From this condition, simply sufficient condition for the robust stabilization (robust practical stabilization) is deduced. Moreover, if the equilibrium of the closed-loop system is unique, the existence of such a robust control Lyapunov function will also imply robustly globally asymptotical stabilization. Then a continuous state feedback law can be constructed explicitly. The simulation shows the effectiveness of the method.
Robust laser frequency stabilization by serrodyne modulation
Kohlhaas, Ralf; Bernon, Simon; Bertoldi, Andrea; Landragin, Arnaud; Bouyer, Philippe
2011-01-01
We report the frequency stabilization of a distributed feedback erbium-doped fiber laser on an optical cavity by serrodyne frequency shifting. A correction bandwidth of 2.4 MHz and a dynamic range of 220 MHz are achieved, which leads to a strong robustness against large disturbances up to high frequencies. Serrodyne frequency shifting allows to use an electro-optical modulator as a fast external transducer with a correction range which exceeds the one of acousto-optical modulators by at least one order of magnitude.
Rauk, Adam P; Guo, Kevin; Hu, Yanling; Cahya, Suntara; Weiss, William F
2014-08-01
Defining a suitable product presentation with an acceptable stability profile over its intended shelf-life is one of the principal challenges in bioproduct development. Accelerated stability studies are routinely used as a tool to better understand long-term stability. Data analysis often employs an overall mass action kinetics description for the degradation and the Arrhenius relationship to capture the temperature dependence of the observed rate constant. To improve predictive accuracy and precision, the current work proposes a least-squares estimation approach with a single nonlinear covariate and uses a polynomial to describe the change in a product attribute with respect to time. The approach, which will be referred to as Arrhenius time-scaled (ATS) least squares, enables accurate, precise predictions to be achieved for degradation profiles commonly encountered during bioproduct development. A Monte Carlo study is conducted to compare the proposed approach with the common method of least-squares estimation on the logarithmic form of the Arrhenius equation and nonlinear estimation of a first-order model. The ATS least squares method accommodates a range of degradation profiles, provides a simple and intuitive approach for data presentation, and can be implemented with ease. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.
Robust Principal Component Analysis?
Candes, Emmanuel J; Ma, Yi; Wright, John
2009-01-01
This paper is about a curious phenomenon. Suppose we have a data matrix, which is the superposition of a low-rank component and a sparse component. Can we recover each component individually? We prove that under some suitable assumptions, it is possible to recover both the low-rank and the sparse components exactly by solving a very convenient convex program called Principal Component Pursuit; among all feasible decompositions, simply minimize a weighted combination of the nuclear norm and of the L1 norm. This suggests the possibility of a principled approach to robust principal component analysis since our methodology and results assert that one can recover the principal components of a data matrix even though a positive fraction of its entries are arbitrarily corrupted. This extends to the situation where a fraction of the entries are missing as well. We discuss an algorithm for solving this optimization problem, and present applications in the area of video surveillance, where our methodology allows for th...
Zhang Hua-Guang; Fu Jie; Ma Tie-Dong; Tong Shao-Cheng
2009-01-01
This paper is concerned with the problem of robust stability for a class of Markovian jumping stochastic neural networks (MJSNNs) subject to mode-dependent time-varying interval delay and state-multiplicative noise.Based on the Lyapunov-Krasovskii functional and a stochastic analysis approach,some new delay-dependent sufficient conditions are obtained in the linear matrix inequality (LMI) format such that delayed MJSNNs are globally asymptotically stable in the mean-square sense for all admissible uncertainties.An important feature of the results is that the stability criteria are dependent on not only the lower bound and upper bound of delay for all modes but also the covariance matrix consisting of the correlation coefficient.Numerical examples are given to illustrate the effectiveness.
M.Syed Ali
2011-01-01
In this paper,the global stability of Takagi-Sugeno(TS)uncertain stochastic fuzzy recurrent neural networks with discrete and distributed time-varying delays(TSUSFRNNs)is considered.A novel LMI-based stability criterion is obtained by using Lyapunov functional theory to guarantee the asymptotic stability of TSUSFRNNs.The proposed stability conditions are demonstrated through numerical examples.Furthermore,the supplementary requirement that the time derivative of time-varying delays must be smaller than one is removed.Comparison results are demonstrated to show that the proposed method is more able to guarantee the widest stability region than the other methods available in the existing literature.
Semigroup approximation and robust stabilization of distributed parameter systems
Kurdila, A. J.; Fabiano, R.; Strganac, T.; Hsu, S.
1994-01-01
Theoretical results that enable rigorous statements of convergence and exponential stability of Galerkin approximations of LQR controls for infinite dimensional, or distributed parameter, systems have proliferated over the past ten years. In addition, extensive progress has been made over the same time period in the derivation of robust control design strategies for finite dimensional systems. However, the study of the convergence of robust finite dimensional controllers to robust controllers for infinite dimensional systems remains an active area of research. We consider a class of soft-constrained differential games evolving in a Hilbert space. Under certain conditions, a saddle point control can be given in feedback form in terms of a solution to a Riccati equation. By considering a related LQR problem, we can show a convergence result for finite dimensional approximations of this differential game. This yields a computational algorithm for the feedback gain that can be derived from similar strategies employed in infinite dimensional LQR control design problems. The approach described in this paper also inherits the additional properties of stability robustness common to game theoretic methods in finite dimensional analysis. These theoretical convergence and stability results are verified in several numerical experiments.
Robust stabilization of general nonlinear systems with structural uncertainty
无
2006-01-01
This paper deals with the robust stabilization and passivity of general nonlinear systems with structural uncertainty. By using Lyapunov function, it verifies that under some conditions the robust passivity implies the zero-state detectability, Furthermore, it also implies the robust stabilization for such nonlinear systems. We then establish a stabilization method for the nonlinear systems with structural uncertainty. The smooth state feedback law can be constructed with the solution of an equation. Finally, it is worth noting that the main contribution of the paper establishes the relation between robust passivity and feedback stabilization for the general nonlinear systems with structural uncertainty. The simulation shows the effectiveness of the method.
Impact of pilots' biodynamic feedthrough on rotorcraft by robust stability
Quaranta, Giuseppe; Masarati, Pierangelo; Venrooij, Joost
2013-09-01
The coupling of rotorcraft dynamics with the dynamics of one of the main systems devoted to its control, the pilot, may lead to several peculiar phenomena, known as Rotorcraft-Pilot Couplings (RPCs), all characterized by an abnormal behavior that may jeopardize flight safety. Among these phenomena, there is a special class of couplings which is dominated by the biodynamic behavior of the pilot's limbs that close the loop between the vibrations and the control inceptors in the cockpit. Leveraging robust stability analysis, the inherently uncertain pilot biodynamics can be treated as the uncertain portion of a feedback system, making analytical, numerical or graphical determination of proneness to RPC possible by comparing robust stability margins of helicopter models with experimental Biodynamic Feedthrough (BDFT) data. The application of the proposed approach to collective bounce is exemplified using simple analytical helicopter and pilot models. The approach is also applied to detailed helicopter models and experimental BDFT measurement data.
Robustness and robust stability of the active sliding mode synchronization
Naseh, Majid Reza [Electrical Engineering Department, Islamic Azad University, Birjand Branch (Iran, Islamic Republic of)], E-mail: naseh@ee.src.aiu.ir; Haeri, Mohammad [Advanced Control System Lab., Electrical Engineering Department, Sharif University Technology, Tehran (Iran, Islamic Republic of)], E-mail: haeri@sina.sharif.edu
2009-01-15
We have developed relations between uncertainties and signals bounds in one side and the control parameters on the other side in the case of the active sliding mode synchronization. Using Lyapunov stability theorem, we have determined uncertainties levels for which synchronization is achieved for a given set of the control parameters. We have run a nonlinear programming algorithm to determine the control parameters for specific range of the uncertainties. Finally, numerical simulations are presented to verify the derived relations.
Robust Sparse Analysis Regularization
Vaiter, Samuel; Dossal, Charles; Fadili, Jalal
2011-01-01
This paper studies the properties of L1-analysis regularization for the resolution of linear inverse problems. Most previous works consider sparse synthesis priors where the sparsity is measured as the L1 norm of the coefficients that synthesize the signal in a given dictionary. In contrast, the more general analysis regularization minimizes the L1 norm of the correlations between the signal and the atoms in the dictionary. The corresponding variational problem includes several well-known regularizations such as the discrete total variation and the fused lasso. We first prove that a solution of analysis regularization is a piecewise affine function of the observations. Similarly, it is a piecewise affine function of the regularization parameter. This allows us to compute the degrees of freedom associated to sparse analysis estimators. Another contribution gives a sufficient condition to ensure that a signal is the unique solution of the analysis regularization when there is no noise in the observations. The s...
Computation of robustly stabilizing PID controllers for interval systems.
Matušů, Radek; Prokop, Roman
2016-01-01
The paper is focused on the computation of all possible robustly stabilizing Proportional-Integral-Derivative (PID) controllers for plants with interval uncertainty. The main idea of the proposed method is based on Tan's (et al.) technique for calculation of (nominally) stabilizing PI and PID controllers or robustly stabilizing PI controllers by means of plotting the stability boundary locus in either P-I plane or P-I-D space. Refinement of the existing method by consideration of 16 segment plants instead of 16 Kharitonov plants provides an elegant and efficient tool for finding all robustly stabilizing PID controllers for an interval system. The validity and relatively effortless application of presented theoretical concepts are demonstrated through a computation and simulation example in which the uncertain mathematical model of an experimental oblique wing aircraft is robustly stabilized.
Sutawanir Darwis
2012-05-01
Full Text Available Empirical decline curve analysis of oil production data gives reasonable answer in hyperbolic type curves situations; however the methodology has limitations in fitting real historical production data in present of unusual observations due to the effect of the treatment to the well in order to increase production capacity. The development ofrobust least squares offers new possibilities in better fitting production data using declinecurve analysis by down weighting the unusual observations. This paper proposes a robustleast squares fitting lmRobMM approach to estimate the decline rate of daily production data and compares the results with reservoir simulation results. For case study, we usethe oil production data at TBA Field West Java. The results demonstrated that theapproach is suitable for decline curve fitting and offers a new insight in decline curve analysis in the present of unusual observations.
Robust stabilization, robust performance, and disturbance attenuation for uncertain linear systems
Wang, Yeih J.; Shieh, Leang S.; Sunkel, John W.
1992-01-01
This paper presents a linear quadratic regulator approach to the robust stabilization, robust performance, and disturbance attenuation of uncertain linear systems. The state-feedback designed systems provide both the robust stability with optimal performance and the disturbance attenuation with H-infinity-norm bounds. The proposed approach can be applied to matched and/or mismatched uncertain linear systems. For a matched uncertain linear system, it is shown that the disturbance attenuation robust-stabilizing controllers with or without optimal performance always exist and can be easily determined without searching; whereas, for a mismatched uncertain linear system, the introduced tuning parameters greatly enhance the flexibility of finding the disturbance-attenuation robust-stabilizing controllers.
Robust stability for the perturbed sampled-data systems
无
2006-01-01
Robust stability for a class of sampled-data systems whose underlying continuous-time systems were subjected to additive structured perturbations was considered. The proposed upper bounds of the induced perturbations in discrete-time model were similar to those obtained in reference. A stable digital optimal state feedback controller whose design was based on the solution of Riccati equation was given. By considering stability based on the second method of Lyapunov, the robust stability bounds for discrete-time model was obtained.Combining the above findings, one sufficient condition of robust stability and a new region of robust stability on the underlying continuous-time system were obtained. Example was given to illustrate the proposed results. It was shown that the sampling period was a crucial design parameter.
On delay-dependent robust stability of neutral systems
Renxin ZHONG; Zhi YANG; Guoli WANG
2006-01-01
The delay-dependent robust stability of uncertain linear neutral systems with delays is investigated. Both discrete-delay-dependent/neutral-delay-independent and neutral-/discrete- delay-dependent stability criteria will be developed. The proposed stability criteria are formulated in the form of linear matrix inequalities and it is easy to check the robust stability of the considered systems. By introducing certain Lyapunov-Krasovskii functional the mathematical development of our result avoids model transformation and bounding for cross terms, which lead to conservatism. Finally, numerical example is given to indicate the improvement over some existing results.
Robust Stabilization for Uncertain Linear Delay Markow Jump System
钟麦英; 汤兵勇; 黄小原
2001-01-01
Markov jump linear systems are defined as a family of linear systems with randomly Markov jumping parameters and are used to model systems subject to failures or changes in structure. The robust stabilization problem of jump linear delay system with umcerratnty was studied. By using of linear matrix inequalities, the existence conditions of robust stabilizing and the state feedback controller designing methods are also presented and proved. Finally, an illustrated example shows the effectiveness of this approach.
Inherent robust stability of driver support systems
王龙; J.; Ackermann
1999-01-01
Presented are the fact that the transfer function from the front steering angle to yaw rate is strictly positive real, irrespective of the uncertain mass and uncertain velocity, how to determine the positivity margin for this transfer function (some stabilization results are obtained), and how to check the positivity of a controller family. Furthermore,by exploiting the intrinsic structure of system equations and uncertainties, a nonconservative PID stabilization criterion for driver support systems is established. Some interesting results on positivity and connections of PID controllers are shown. Finally, some extreme point results on PID α-stabilization are obtained. These results give certain explanations and justifications for the simulation results performed at German Aerospace Research Center.
Robust stabilization of uncertain nonholonomic systems with strong nonlinear drifts
Yuqiang WU; Xiuyun ZHENG
2008-01-01
This paper investigates the robust stabilization of the nonholonomic control systems with strongly nonlinear uncertainties.In order to make the state scaling effective and to prevent the fiflite time escape phenomenon from happening.the switching control strategy based on the state measurement of the first subsystem is employed to achieve the asymptotic stabilization.The recurslve integrator backstepping technique is applied to the design of the robust controller.The simulation example demonstrates the efficiency and robust features of the proposed method.
New results on robust exponential stability of integral delay systems
Melchor-Aguilar, Daniel
2016-06-01
The robust exponential stability of integral delay systems with exponential kernels is investigated. Sufficient delay-dependent robust conditions expressed in terms of linear matrix inequalities and matrix norms are derived by using the Lyapunov-Krasovskii functional approach. The results are combined with a new result on quadratic stabilisability of the state-feedback synthesis problem in order to derive a new linear matrix inequality methodology of designing a robust non-fragile controller for the finite spectrum assignment of input delay systems that guarantees simultaneously a numerically safe implementation and also the robustness to uncertainty in the system matrices and to perturbation in the feedback gain.
Robust Helicopter Stabilization in the Face of Wind Disturbance
A. Danapalasingam, Kumeresan; Leth, John-Josef; la Cour-Harbo, Anders
2010-01-01
When a helicopter is required to hover with minimum deviations from a desired position without measurements of an affecting persistent wind disturbance, a robustly stabilizing control action is vital. In this paper, the stabilization of the position and translational velocity of a nonlinear...
Robust stabilization for a class of nonlinear networked control systems
Jinfeng GAO; Hongye SU; Xiaofu JI; Jian CHU
2008-01-01
The problem of robust stabilization for a class of uncertain networked control systems(NCSs)with nonlinearities satisfying a given sector condition is investigated in this paper.By introducing a new model of NCSs with parameter uncertainty,network.induced delay,nonlinearity and data packet dropout in the transmission,a strict linear matrix inequality(LMI)criterion is proposed for robust stabilization of the uncenmn nonlinear NCSs based on the Lyapunov stability theory.The maximum allowable transfer interval(MATI)can be derived by solving the feasibility problem of the corresponding LMI.Some numerical examples are provided to demonstrate the applicability of the proposed algorithm.
Robust stabilization of stochastic systems based on the LQ controller
Jundong BAO; Feiqi DENG; Qi LUO
2005-01-01
The robust exponential stability in mean square for a class of linear stochastic uncertain control systems is dealt with.For the uncertain stochastic systems,we have designed an optimal controller which guarantees the exponential stability of the system.Actually,we employed Lyapunov function approach and the stochastic algebraic Riccati equation (SARE) to have shown the robustness of the linear quadratic(LQ) optimal control law.And the algebraic criteria for the exponential stability on the linear stochastic uncertain closed-loop systems are given.
Robust Stabilization, Robust Performance, and Disturbance Attenuation for Uncertain Linear Systems
1992-01-01
the following Riccati equation: [ - ] B Tp+!I+ 1 CTC+Q=O. (7) Then, a disturbance-attenuation robust- stabilizing control law is given by u(t) = K z(t...disturbance-attenuation robust- stabilizing control law with the attenuation constant 6 is given by u(t) = K x(t), where K = -- BT P with 7> 1/2... stabilizing control law with the attenuation constant 6 is given by u(t) = K z(t), where K = -7 BT P with 7> - 1/2. Furthermore, the state-feedback
Robust Stabilization of a Class of passive Nonlinear Systems
Joshi, Suresh M.; Kelkar, Atul G.
1996-01-01
The problem of feedback stabilization is considered for a class of nonlinear, finite dimensional, time invariant passive systems that are affine in control. Using extensions of the Kalman-Yakubovch lemma, it is shown that such systems can be stabilized by a class of finite demensional, linear, time-invariant controllers which are strictly positive real in the weak or marginal sense. The stability holds regardless of model uncertainties, and is therefore, robust.
A Developed Graphical User Interface for Power System Stability and Robustness Studies
GHOURAF Djamel Eddine
2015-06-01
Full Text Available This paper present the realization and development of a graphical user interface (GUI to studied the stability and robustness of power systems (analysis and synthesis, using Conventional Power System Stabilizers (CPSS - realized on PID scheme or advanced controllers (based on adaptive and robust control, and applied on automatic excitation control of powerful synchronous generators, to improve dynamic performances and robustness. The GUI is a useful average to facilitate stability study of power system with the analysis and synthesis of regulators, and resolution of the compromise: results precision / calculation speed. The obtained Simulation results exploiting our developed GUI realized under MATLAB shown considerable improvements in static and dynamic performances, a great stability and enhancing the robustness of power system, with best precision and minimum operating time. This study was performed for different types of powerful synchronous generators.
Robust enzyme design: bioinformatic tools for improved protein stability.
Suplatov, Dmitry; Voevodin, Vladimir; Švedas, Vytas
2015-03-01
The ability of proteins and enzymes to maintain a functionally active conformation under adverse environmental conditions is an important feature of biocatalysts, vaccines, and biopharmaceutical proteins. From an evolutionary perspective, robust stability of proteins improves their biological fitness and allows for further optimization. Viewed from an industrial perspective, enzyme stability is crucial for the practical application of enzymes under the required reaction conditions. In this review, we analyze bioinformatic-driven strategies that are used to predict structural changes that can be applied to wild type proteins in order to produce more stable variants. The most commonly employed techniques can be classified into stochastic approaches, empirical or systematic rational design strategies, and design of chimeric proteins. We conclude that bioinformatic analysis can be efficiently used to study large protein superfamilies systematically as well as to predict particular structural changes which increase enzyme stability. Evolution has created a diversity of protein properties that are encoded in genomic sequences and structural data. Bioinformatics has the power to uncover this evolutionary code and provide a reproducible selection of hotspots - key residues to be mutated in order to produce more stable and functionally diverse proteins and enzymes. Further development of systematic bioinformatic procedures is needed to organize and analyze sequences and structures of proteins within large superfamilies and to link them to function, as well as to provide knowledge-based predictions for experimental evaluation.
Robust Stability of Fractional Order Time-Delay Control Systems: A Graphical Approach
Radek Matušů; Roman Prokop
2015-01-01
The paper deals with a graphical approach to investigation of robust stability for a feedback control loop with an uncertain fractional order time-delay plant and integer order or fractional order controller. Robust stability analysis is based on plotting the value sets for a suitable range of frequencies and subsequent verification of the zero exclusion condition fulfillment. The computational examples present the typical shapes of the value sets of a family of closed-loop characteristic qua...
Yielding elastic tethers stabilize robust cell adhesion.
Matt J Whitfield
2014-12-01
Full Text Available Many bacteria and eukaryotic cells express adhesive proteins at the end of tethers that elongate reversibly at constant or near constant force, which we refer to as yielding elasticity. Here we address the function of yielding elastic adhesive tethers with Escherichia coli bacteria as a model for cell adhesion, using a combination of experiments and simulations. The adhesive bond kinetics and tether elasticity was modeled in the simulations with realistic biophysical models that were fit to new and previously published single molecule force spectroscopy data. The simulations were validated by comparison to experiments measuring the adhesive behavior of E. coli in flowing fluid. Analysis of the simulations demonstrated that yielding elasticity is required for the bacteria to remain bound in high and variable flow conditions, because it allows the force to be distributed evenly between multiple bonds. In contrast, strain-hardening and linear elastic tethers concentrate force on the most vulnerable bonds, which leads to failure of the entire adhesive contact. Load distribution is especially important to noncovalent receptor-ligand bonds, because they become exponentially shorter lived at higher force above a critical force, even if they form catch bonds. The advantage of yielding is likely to extend to any blood cells or pathogens adhering in flow, or to any situation where bonds are stretched unequally due to surface roughness, unequal native bond lengths, or conditions that act to unzip the bonds.
Robust Stabilization of Uncertain Systems Based on Energy Dissipation Concepts
Gupta, Sandeep
1996-01-01
Robust stability conditions obtained through generalization of the notion of energy dissipation in physical systems are discussed in this report. Linear time-invariant (LTI) systems which dissipate energy corresponding to quadratic power functions are characterized in the time-domain and the frequency-domain, in terms of linear matrix inequalities (LMls) and algebraic Riccati equations (ARE's). A novel characterization of strictly dissipative LTI systems is introduced in this report. Sufficient conditions in terms of dissipativity and strict dissipativity are presented for (1) stability of the feedback interconnection of dissipative LTI systems, (2) stability of dissipative LTI systems with memoryless feedback nonlinearities, and (3) quadratic stability of uncertain linear systems. It is demonstrated that the framework of dissipative LTI systems investigated in this report unifies and extends small gain, passivity, and sector conditions for stability. Techniques for selecting power functions for characterization of uncertain plants and robust controller synthesis based on these stability results are introduced. A spring-mass-damper example is used to illustrate the application of these methods for robust controller synthesis.
Thermal stability of the C106 dye in robust electrolytes
Lund, Torben; Phuong, Nguyen Tuyet; Pechy, Peter
Thermal stability of the C106 dye in robust electrolytes. We have investigated the thermal stability and degradation chemistry of the ruthenium dye C106 (Figure 1) at 80 ◦C in the “robust” electrolyte “B” comprised of 1.0 M DMII, 0.03 M I2, 0.5 M NBB, and 0.1 M GuNCS in 3-methoxypropionitrile (3......-MPN) introduced by Gao et al. in 2008. [1]. Figure 1 Thermal degradation of C106 bound to TiO2 at 80 ºC in dark as a function of heating time. ● C106 = RuLL´(NCS)2 ■ RuLL´(NCS)(NBB)+ ▲ RuLL´(NCS)(3-MPN)+ The C106 dye was attached to the surface of TiO2 nano-particles and stable colloidal solutions...... of the particles were prepared in electrolyte mixture B. The solutions were thermally treated at 80 ◦C for 0-2000 hours followed by dye extraction and analysis by HPLC coupled to UV/Vis and electro spray mass spectrometry [2]. Figure 1 shows the concentration profiles of C106 samples prepared under ambient...
Finite-Time Robust Stabilization for Stochastic Neural Networks
Weixiong Jin
2012-01-01
Full Text Available This paper is concerned with the finite-time stabilization for a class of stochastic neural networks (SNNs with noise perturbations. The purpose of the addressed problem is to design a nonlinear stabilizator which can stabilize the states of neural networks in finite time. Compared with the previous references, a continuous stabilizator is designed to realize such stabilization objective. Based on the recent finite-time stability theorem of stochastic nonlinear systems, sufficient conditions are established for ensuring the finite-time stability of the dynamics of SNNs in probability. Then, the gain parameters of the finite-time controller could be obtained by solving a linear matrix inequality and the robust finite-time stabilization could also be guaranteed for SNNs with uncertain parameters. Finally, two numerical examples are given to illustrate the effectiveness of the proposed design method.
Design for robust stabilization of nonlinear systems with uncertain parameters
赖旭芝; 文静; 吴敏
2004-01-01
Based on Lyapunov stability theory, a design method for the robust stabilization problem of a class of nonlinear systems with uncertain parameters is presented. The design procedure is divided into two steps: the first is to design controllers for the nominal system and make the system asymptotically stabilize at the expected equilibrium point; the second is to construct closed-loop nominal system based on the first step, then design robust controller to make the error of state between the original system and the nominal system converge to zero, thereby a dynamic controller with the constructed closed-loop nominal system served as interior dynamic is obtained. A numerical simulation verifies the correctness of the design method.
Robustness Analysis of Timber Truss Structure
Rajčić, Vlatka; Čizmar, Dean; Kirkegaard, Poul Henning
2010-01-01
The present paper discusses robustness of structures in general and the robustness requirements given in the codes. Robustness of timber structures is also an issues as this is closely related to Working group 3 (Robustness of systems) of the COST E55 project. Finally, an example of a robustness...... evaluation of a widespan timber truss structure is presented. This structure was built few years ago near Zagreb and has a span of 45m. Reliability analysis of the main members and the system is conducted and based on this a robustness analysis is preformed....
Robust stability test for 2-D continuous-discrete systems with interval parameters
肖扬
2004-01-01
It is revealed that the dynamic stability of 2-D recursive continuous-discrete systems with interval parameters involves the problem of robust Hurwitz-Schur stability of bivariate polynomials family. It is proved that the HurwitzSchur stability of the denominator polynomials of the systems is necessary and sufficient for the asymptotic stability of the 2-D hybrid systems. The 2-D hybrid transformation, i.e. 2-D Laplace-Z transformation, has been proposed to solve the stability analysis of the 2-D continuous-discrete systems, to get the 2-D hybrid transfer functions of the systems. The edge test for the Hurwitz-Schur stability of interval bivariate polynomials is introduced. The Hurwitz-Schur stability of the interval family of 2-D polynomials can be guaranteed by the stability of its finite edge polynomials of the family. An algorithm about the stability test of edge polynomials is given.
Robust stabilization of rotor-active magnetic bearing systems
Li, Guoxin
Active magnetic bearings (AMBs) are emerging as a beneficial technology for high-speed and high-performance suspensions in rotating machinery applications. A fundamental feedback control problem is robust stabilization in the presence of uncertain destabilizing mechanisms in aeroelastic, hydroelastic dynamics, and AMB feedback. As rotating machines are evolving in achieving high speed, high energy density, and high performance, the rotor and the support structure become increasingly flexible, and highly coupled. This makes rotor-AMB system more challenging to stabilize. The primary objective of this research is to develop a systematic control synthesis procedure for achieving highly robust stabilization of rotor-AMB systems. Of special interest is the stabilization of multivariable systems such as the AMB supported flexible rotors and gyroscopic rotors, where the classical control design may encounter difficulties. To this end, we first developed a systematic modeling procedure. This modeling procedure exploited the best advantages of technology developed in rotordynamics and the unique system identification tool provided by the AMBs. A systematic uncertainty model for rotor-AMB systems was developed, eliminating the iterative process of selecting uncertainty structures. The consequences of overestimation or underestimation of uncertainties were made transparent to control engineers. To achieve high robustness, we explored the fundamental performance/robustness limitations due to rotor-AMB system unstable poles. We examined the mixed sensitivity performance that is closely related to the unstructured uncertainty. To enhance transparency of the synthesis, we analyzed multivariable controllers from classical control perspectives. Based on these results, a systematic robust control synthesis procedure was established. For a strong gyroscopic rotor over a wide speed range, we applied the advanced gain-scheduled synthesis, and compared two synthesis frameworks in
Microgrid Stability Controller Based on Adaptive Robust Total SMC
Su, Xiaoling; Han, Minxiao; Guerrero, Josep M.
2015-01-01
and mathematical models of the MSC indicate that the system is inherently nonlinear and time-variable. Therefore, this paper proposes an adaptive robust total sliding-mode control (ARTSMC) system for the MSC. It is proved that the ARTSMC system is insensitive to parametric uncertainties and external disturbances......This paper presents a microgrid stability controller (MSC) in order to provide existing DGs the additional functionality of working in islanding mode without changing their control strategies in grid-connected mode and to enhance the stability of the microgrid. Microgrid operating characteristics....... The MSC provides fast dynamic response and robustness to the microgrid. When the system is operating in grid-connected mode, it is able to improve the controllability of the exchanged power between the microgrid and the utility grid, while smoothing DG’s output power. When the microgrid is operating...
On delay-dependent robust stability for uncertain neutral systems
He Yong; Wu Min
2005-01-01
The problem of delay-dependent criteria for the robust stability of neutral systems with time-varying structured uncertainties and identi-eal neutral-delay and discrete-delay is concerned. A criterion for nominal systems is presented by taking the relationship between the terms in the Leibniz-Newton formula into account, which is described by some freeweighting matrices. In addition, this criterion is extended to robust stability of the systems with time-varying structured uncertainties. All of the criteria are based on linear matrix inequality such that it is easy to calculate the upper bound of the time-delay and the free-weighting matrices. Numerical examples illustrate the effectiveness and the improvement over the existing results.
Robust Stabilization of Nonlinear Systems with Uncertain Varying Control Coefficient
Zaiyue Yang
2014-01-01
Full Text Available This paper investigates the stabilization problem for a class of nonlinear systems, whose control coefficient is uncertain and varies continuously in value and sign. The study emphasizes the development of a robust control that consists of a modified Nussbaum function to tackle the uncertain varying control coefficient. By such a method, the finite-time escape phenomenon has been prevented when the control coefficient is crossing zero and varying its sign. The proposed control guarantees the asymptotic stabilization of the system and boundedness of all closed-loop signals. The control performance is illustrated by a numerical simulation.
Robust Stability Criterion for Uncertain Neural Networks with Time Delays
LIN Zhi-wei; ZHANG Ning; YANG Hong-jiu
2010-01-01
The robust stability of uncertain neural network with time-varying delay was investigated. The norm-bounded un-certainties are included in the system matrices. The constraint on time-varying delays is removed, which means that a fast time-varying delay is admissible. Some new delay-dependent stability criteria were presented by using Lyapunov-Krasovskii functional and linear matrix inequalities (LMIs) approaches. Finally, a numerical example was given to illustrate the effec-tiveness and innovation nature of the developed techniques.
Robust decentralized adaptive stabilization for a class of interconnected systems
Zhaojing WU; Xuejun XIE; Siying ZHANG
2004-01-01
The robust decentralized adaptive output-feedback stabilization for a class of interconnected systems with static and dynamic interconnections by using the MT-filters and backstepping design method is studied. By introducing a new filtered tramformation, the adaptive laws were derived for measurement. Under the assumption of the nonlinear growth conditions imposed on the nonlinear interconnections and by constructing the error system and using a new proof method, the global stability of the closed-loop system was effectively analyzed, and the exponential convergence of all the signals except for parameter estimates were guaranteed.
A Robust Method to Improve Stability in Matrix Converters
Liu, F.; Klumpner, Christian; Blaabjerg, Frede
2004-01-01
of instability. The matrix converter stability can be improved by decoupling its input current with the input voltage. A modulation strategy is presented that satisfies the idea. The difference of the strategy compared with the traditional one only concerns on the definition of the reference angle for the input....... It is simple in implementation and the algorithm is robust. Experimental results are presented to verify the conclusions....
Robust Stability and Performance Comparison of PID and PPI Control
任正云; 张红; 邵惠鹤
2004-01-01
Predictive PI (PPI) control form, capable of time delay compensation, has been put forward recently. This control algorithm is essentially a PI controller with enhanced derivative action, which is not only suitable for long time delay process, but also of simple structure and excellent robust stability. The performance of PPI controller was demonstrated and compared with that of traditional PID controller by different tuning methods.
QFT Framework for Robust Tuning of Power System Stabilizers
Alavi, Seyyed Mohammad Mahdi; Izadi-Zamanabadi, Roozbeh
2005-01-01
This paper discusses the use of conventional quantitative feedback design for Power System Stabilizer (PSS). An appropriate control structure of the PSS that is directly applicable to PSS, is described. Two desired performances are also proposed in order to achieve an overall improvement in damping...... and robustness. The efficiency of the proposed method is demonstrated on Single Machine Infinite Bus (SMIB) power system with level of uncertainty....
Kwakkel, Jan; Haasnoot, Marjolijn
2015-04-01
performance of a candidate plan with the performance of other candidate plans across a large ensemble of plausible futures. Initial results suggest that the simplest satisficing metric, inspired by the signal to noise ratio, results in very risk averse solutions. Other satisficing metrics, which handle the average performance and the dispersion around the average separately, provide substantial additional insights into the trade off between the average performance, and the dispersion around this average. In contrast, the regret-based metrics enhance insight into the relative merits of candidate plans, while being less clear on the average performance or the dispersion around this performance. These results suggest that it is beneficial to use multiple robustness metrics when doing a robust decision analysis study. Haasnoot, M., J. H. Kwakkel, W. E. Walker and J. Ter Maat (2013). "Dynamic Adaptive Policy Pathways: A New Method for Crafting Robust Decisions for a Deeply Uncertain World." Global Environmental Change 23(2): 485-498. Kwakkel, J. H., M. Haasnoot and W. E. Walker (2014). "Developing Dynamic Adaptive Policy Pathways: A computer-assisted approach for developing adaptive strategies for a deeply uncertain world." Climatic Change.
Robustness Analysis of Kinetic Structures
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard
2009-01-01
The present paper considers robustness of kinetic structures. Robustness of structures has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. Especially for these types of structural syst...... systems, it is of interest to investigate how robust the structures are, or what happens if a structural element is added to or removed from the original structure. The present paper discusses this issue for kinetic structures in architecture....
Wang, Leimin; Shen, Yi; Sheng, Yin
2016-04-01
This paper is concerned with the finite-time robust stabilization of delayed neural networks (DNNs) in the presence of discontinuous activations and parameter uncertainties. By using the nonsmooth analysis and control theory, a delayed controller is designed to realize the finite-time robust stabilization of DNNs with discontinuous activations and parameter uncertainties, and the upper bound of the settling time functional for stabilization is estimated. Finally, two examples are provided to demonstrate the effectiveness of the theoretical results.
LLCL-Filtered Grid Converter with Improved Stability and Robustness
Min, Huang; Wang, Xiongfei; Loh, Poh Chiang
2016-01-01
impedance variations, making its design more challenging. To address these concerns, a new parameter design method for LLCL-filter has been formulated in the paper, which when enforced, guarantees robust and stable grid current control regardless of how the grid conditions change. It is thus an enhanced......LLCL-filter has been proven to introduce more filtering at the converter switching frequency, while using smaller passive components. However, like other higher order filters, it introduces resonance to the grid when used with a grid converter. Its stability and robustness are also affected by grid...... method even with no damping added to the grid converter. The method has been applied to the development of an LLCL-filter for testing in the laboratory with a 5-kW, 400-V, and 50-Hz grid converter. The method can also be applied to the lower order LCL-filter with only a slight modification needed....
Ma, Yingdong; Lu, Junguo; Chen, Weidong
2014-03-01
This paper investigates the robust stability and stabilization of fractional order linear systems with positive real uncertainty. Firstly, sufficient conditions for the asymptotical stability of such uncertain fractional order systems are presented. Secondly, the existence conditions and design methods of the state feedback controller, static output feedback controller and observer-based controller for asymptotically stabilizing such uncertain fractional order systems are derived. The results are obtained in terms of linear matrix inequalities. Finally, some numerical examples are given to validate the proposed theoretical results.
Uezato, E. [Ryukyu Univ., Nishihara, Okinawa (Japan)] Ikeda, M. [Osaka Univ., Suita (Japan)] Toyama, R. [Kobe Univ. (Japan)
1998-11-30
This paper presents two sufficient conditions as linear and bilinear matrix conditions for a system with polytopic uncertainties to be robustly stabilizable by an approach of quadratic stabilization of equivalent systems as regards closed system and robust stabilization. For the purpose, two systems are assumed which are equivalent concerning closed loop system and robust stabilization and contains no uncertainty in the coefficient matrix of the differential of descriptor variables. The robust stability conditions for the original system are obtained by deriving quadratic stabilization conditions of the equivalent systems because the original closed system is robustly stable if those equivalent systems are quadratically stable. Robust stabilizability conditions for a system with polytopic uncertainties in the coefficient matrix are given in terms of linear and bilinear matrix inequalities. In addition, an algorithm based on the idea of the homotopy method is proposed to solve the bilinear matrix inequality. 13 refs., 1 fig.
Microgrid Stability Controller Based on Adaptive Robust Total SMC
Xiaoling Su
2015-03-01
Full Text Available This paper presents a microgrid stability controller (MSC in order to provide existing distributed generation units (DGs the additional functionality of working in islanding mode without changing their control strategies in grid-connected mode and to enhance the stability of the microgrid. Microgrid operating characteristics and mathematical models of the MSC indicate that the system is inherently nonlinear and time-variable. Therefore, this paper proposes an adaptive robust total sliding-mode control (ARTSMC system for the MSC. It is proved that the ARTSMC system is insensitive to parametric uncertainties and external disturbances. The MSC provides fast dynamic response and robustness to the microgrid. When the system is operating in grid-connected mode, it is able to improve the controllability of the exchanged power between the microgrid and the utility grid, while smoothing the DGs’ output power. When the microgrid is operating in islanded mode, it provides voltage and frequency support, while guaranteeing seamless transition between the two operation modes. Simulation and experimental results show the effectiveness of the proposed approach.
Control design for robust stability in linear regulators: Application to aerospace flight control
Yedavalli, R. K.
1986-01-01
Time domain stability robustness analysis and design for linear multivariable uncertain systems with bounded uncertainties is the central theme of the research. After reviewing the recently developed upper bounds on the linear elemental (structured), time varying perturbation of an asymptotically stable linear time invariant regulator, it is shown that it is possible to further improve these bounds by employing state transformations. Then introducing a quantitative measure called the stability robustness index, a state feedback conrol design algorithm is presented for a general linear regulator problem and then specialized to the case of modal systems as well as matched systems. The extension of the algorithm to stochastic systems with Kalman filter as the state estimator is presented. Finally an algorithm for robust dynamic compensator design is presented using Parameter Optimization (PO) procedure. Applications in a aircraft control and flexible structure control are presented along with a comparison with other existing methods.
Pakazad, Sina Khoshfetrat; Hansson, Anders; Andersen, Martin Skovgaard;
2013-01-01
We consider a class of convex feasibility problems where the constraints that describe the feasible set are loosely coupled. These problems arise in robust stability analysis of large, weakly interconnected uncertain systems. To facilitate distributed implementation of robust stability analysis o...
Robust adaptive output stabilization using dynamic normalizing signal
Haixia SU; Xuejun XIE; Haikuan LIU
2007-01-01
For a class of nonlinear systems with dynamic uncertainties,robust adaptive stabilization problem is considered in this paper.Firstly,by introducing an observer,an augmented system is obtained.Based on the system,we construct an exp-ISpS Lyapunov function for the unmodeled dynamics,prove that the unmodeled dynamics is exp-ISpS,and then obtain a dynamic normalizing signal to counteract the dynamic disturbances.By the backstepping technique,an adaptive controller is given,it is proved that all the signals in the adaptive control system are globally uniformly ultimately bounded,and the output can be regulated to the origin with any prescribed accuracy.A simulation example further demonstrates the efficiency of the control scheme.
Robust SRAM Designs and Analysis
Singh, Jawar; Pradhan, Dhiraj K
2013-01-01
This book provides a guide to Static Random Access Memory (SRAM) bitcell design and analysis to meet the nano-regime challenges for CMOS devices and emerging devices, such as Tunnel FETs. Since process variability is an ongoing challenge in large memory arrays, this book highlights the most popular SRAM bitcell topologies (benchmark circuits) that mitigate variability, along with exhaustive analysis. Experimental simulation setups are also included, which cover nano-regime challenges such as process variation, leakage and NBTI for SRAM design and analysis. Emphasis is placed throughout the book on the various trade-offs for achieving a best SRAM bitcell design. Provides a complete and concise introduction to SRAM bitcell design and analysis; Offers techniques to face nano-regime challenges such as process variation, leakage and NBTI for SRAM design and analysis; Includes simulation set-ups for extracting different design metrics for CMOS technology and emerging devices; Emphasizes different trade-offs for ach...
Robust Mediation Analysis Based on Median Regression
Yuan, Ying; MacKinnon, David P.
2014-01-01
Mediation analysis has many applications in psychology and the social sciences. The most prevalent methods typically assume that the error distribution is normal and homoscedastic. However, this assumption may rarely be met in practice, which can affect the validity of the mediation analysis. To address this problem, we propose robust mediation analysis based on median regression. Our approach is robust to various departures from the assumption of homoscedasticity and normality, including heavy-tailed, skewed, contaminated, and heteroscedastic distributions. Simulation studies show that under these circumstances, the proposed method is more efficient and powerful than standard mediation analysis. We further extend the proposed robust method to multilevel mediation analysis, and demonstrate through simulation studies that the new approach outperforms the standard multilevel mediation analysis. We illustrate the proposed method using data from a program designed to increase reemployment and enhance mental health of job seekers. PMID:24079925
Liu, Ping
2013-07-01
This paper deals with the finite-time stabilization of unified chaotic complex systems with known and unknown parameters. Based on the finite-time stability theory, nonlinear control laws are presented to achieve finite-time chaos control of the determined and uncertain unified chaotic complex systems, respectively. The two controllers are simple, and one of the uncertain unified chaotic complex systems is robust. For the design of a finite-time controller on uncertain unified chaotic complex systems, only some of the unknown parameters need to be bounded. Simulation results for the chaotic complex Lorenz, Lü and Chen systems are presented to validate the design and analysis.
ROBUST STABILITY WITH GUARANTEEING COST FOR DISCRETE TIME-DELAY SYSTEMS WITH NONLINEAR PERTURBATION
JIA Xinchun; ZHENG Nanning; LIU Yuehu
2005-01-01
The problems of robust stability and robust stability with a guaranteeing cost for discrete time-delay systems with nonlinear perturbation are discussed. A sufficient criterion for robust stability is established in an LMI framework and a linear convex optimization problem with LMI constraints for computing maximal perturbation bound is proposed. Meanwhile, a sufficient criterion for robust stability with a guaranteeing cost for such systems is obtained, and an optimal procedure for decreasing the value of guaranteeing cost is put forward. Two examples are used to illustrate the efficiency of the results.
Security analysis of robust perceptual hashing
Koval, Oleksiy; Voloshynovskiy, Sviatoslav; Beekhof, Fokko; Pun, Thierry
2008-02-01
In this paper we considered the problem of security analysis of robust perceptual hashing in authentication application. The main goal of our analysis was to estimate the amount of trial efforts of the attacker, who is acting within the Kerckhoffs security principle, to reveal a secret key. For this purpose, we proposed to use Shannon equivocation that provides an estimate of complexity of the key search performed based on all available prior information and presented its application to security evaluation of particular robust perceptual hashing algorithms.
Robust-mode analysis of hydrodynamic flows
Roy, Sukesh; Gord, James R.; Hua, Jia-Chen; Gunaratne, Gemunu H.
2017-04-01
The emergence of techniques to extract high-frequency high-resolution data introduces a new avenue for modal decomposition to assess the underlying dynamics, especially of complex flows. However, this task requires the differentiation of robust, repeatable flow constituents from noise and other irregular features of a flow. Traditional approaches involving low-pass filtering and principle components analysis have shortcomings. The approach outlined here, referred to as robust-mode analysis, is based on Koopman decomposition. Three applications to (a) a counter-rotating cellular flame state, (b) variations in financial markets, and (c) turbulent injector flows are provided.
Robustness analysis of stochastic biochemical systems.
Ceska, Milan; Safránek, David; Dražan, Sven; Brim, Luboš
2014-01-01
We propose a new framework for rigorous robustness analysis of stochastic biochemical systems that is based on probabilistic model checking techniques. We adapt the general definition of robustness introduced by Kitano to the class of stochastic systems modelled as continuous time Markov Chains in order to extensively analyse and compare robustness of biological models with uncertain parameters. The framework utilises novel computational methods that enable to effectively evaluate the robustness of models with respect to quantitative temporal properties and parameters such as reaction rate constants and initial conditions. We have applied the framework to gene regulation as an example of a central biological mechanism where intrinsic and extrinsic stochasticity plays crucial role due to low numbers of DNA and RNA molecules. Using our methods we have obtained a comprehensive and precise analysis of stochastic dynamics under parameter uncertainty. Furthermore, we apply our framework to compare several variants of two-component signalling networks from the perspective of robustness with respect to intrinsic noise caused by low populations of signalling components. We have successfully extended previous studies performed on deterministic models (ODE) and showed that stochasticity may significantly affect obtained predictions. Our case studies demonstrate that the framework can provide deeper insight into the role of key parameters in maintaining the system functionality and thus it significantly contributes to formal methods in computational systems biology.
Robust geostatistical analysis of spatial data
Papritz, Andreas; Künsch, Hans Rudolf; Schwierz, Cornelia; Stahel, Werner A.
2013-04-01
Most of the geostatistical software tools rely on non-robust algorithms. This is unfortunate, because outlying observations are rather the rule than the exception, in particular in environmental data sets. Outliers affect the modelling of the large-scale spatial trend, the estimation of the spatial dependence of the residual variation and the predictions by kriging. Identifying outliers manually is cumbersome and requires expertise because one needs parameter estimates to decide which observation is a potential outlier. Moreover, inference after the rejection of some observations is problematic. A better approach is to use robust algorithms that prevent automatically that outlying observations have undue influence. Former studies on robust geostatistics focused on robust estimation of the sample variogram and ordinary kriging without external drift. Furthermore, Richardson and Welsh (1995) proposed a robustified version of (restricted) maximum likelihood ([RE]ML) estimation for the variance components of a linear mixed model, which was later used by Marchant and Lark (2007) for robust REML estimation of the variogram. We propose here a novel method for robust REML estimation of the variogram of a Gaussian random field that is possibly contaminated by independent errors from a long-tailed distribution. It is based on robustification of estimating equations for the Gaussian REML estimation (Welsh and Richardson, 1997). Besides robust estimates of the parameters of the external drift and of the variogram, the method also provides standard errors for the estimated parameters, robustified kriging predictions at both sampled and non-sampled locations and kriging variances. Apart from presenting our modelling framework, we shall present selected simulation results by which we explored the properties of the new method. This will be complemented by an analysis a data set on heavy metal contamination of the soil in the vicinity of a metal smelter. Marchant, B.P. and Lark, R
Robust cluster analysis and variable selection
Ritter, Gunter
2014-01-01
Clustering remains a vibrant area of research in statistics. Although there are many books on this topic, there are relatively few that are well founded in the theoretical aspects. In Robust Cluster Analysis and Variable Selection, Gunter Ritter presents an overview of the theory and applications of probabilistic clustering and variable selection, synthesizing the key research results of the last 50 years. The author focuses on the robust clustering methods he found to be the most useful on simulated data and real-time applications. The book provides clear guidance for the varying needs of bot
Blackwell, C. C.
1987-01-01
A relevant facet of the application of Lyapunov gradient-generated robust control to unstable linear autonomous plants is explored. It is demonstrated that if the plant, the output, and the nominal stabilizing control satisfy certain conditions, then the robust component alone stabilizes the nominal plant. An example characterized by two zero eigenvalues and two negative real value poles is presented. These results assure that the robust component will fulfill the role of nominal stabilization successfully so long as the possible magnitude of the robust component can overcome the contribution of the instability to positiveness of the Lyapunov rate.
Blackwell, C. C.
1987-01-01
A relevant facet of the application of Lyapunov gradient-generated robust control to unstable linear autonomous plants is explored. It is demonstrated that if the plant, the output, and the nominal stabilizing control satisfy certain conditions, then the robust component alone stabilizes the nominal plant. An example characterized by two zero eigenvalues and two negative real value poles is presented. These results assure that the robust component will fulfill the role of nominal stabilization successfully so long as the possible magnitude of the robust component can overcome the contribution of the instability to positiveness of the Lyapunov rate.
Curtain, RF
2004-01-01
We solve the problem of robust stabilization with respect to left coprime factor perturbations for a class of irrational transfer functions with a state space realization. We obtain a parameterization of the robustly stabilizing controllers in terms of the generating operators and an arbitrary
Robust Stability and Performance for Linear Systems with Structured and Unstructured Uncertainties
1990-06-01
IEEE Transactions on Automatic Control , vol...34 IEEE Transactions on Automatic Control , vol. AC-30, pp. 577-579, June 1985. [10] Yedavalli, R.K., "Perturbation Bounds for Robust Stability in Linear...Zhou, K. and Khargonekar, Pl, "Stability Robustness Bounds for Linear State Space Models with Structured Uncertainty," IEEE Transactions on Automatic Control ,
Robust stability of discrete-time nonlinear system with time-delay
LIU Xin-ge; WU Min
2005-01-01
The robustly asymptotical stability problem for discrete-time nonlinear systems with time-delay was investigated. Positive definite matrix are constructed through Lyapunov functional. With the identity transform, property of matrix inverse and S-procedure, a new sufficient condition independent of the size of time-delay for robust stability of discrete-time nonlinear systems with time-delay is established. With Schur complement, another equivalent sufficient condition for robust stability of discrete-time nonlinear systems with time-delay is given. Finally, a sufficient condition dependent on the size of time-delay for robust stability of discrete-time nonlinear systems with time-delay is obtained. A unified approach is used to cast the robust stability problem into a convex optimization involving linear matrix inequalities.
Study on Robust Uniform Asymptotical Stability for Uncertain Linear Impulsive Delay Systems
刘斌; 刘新芝; 廖晓昕
2003-01-01
In the area of control theory the time-delay systems have been investigated. It's well known that delays often result in instability, therefore, stability analysis of time-delay systems is an important subject in control theory. As a result, many criteria for testing the stability of linear time-delay systems have been proposed. Significant progress has been made in the theory of impulsive systems and impulsive delay systems in recent years. However, the corresponding theory for uncertain impulsive systems and uncertain impulsive delay systems has not been fully developed. In this paper, robust stability criteria are established for uncertain linear delay impulsive systems by using Lyapunov function, Razumikhin techniques and the results obtained. Some examples are given to illustrate our theory.
Robust Absolute Stability of General Interval Lur'e Type Nonlinear Control Systems
无
2001-01-01
In this paper, Lyapunov function method isused to study the robust absolute stability of general interval Lur'e type nonlinear control systems. As a result, algebraically sufficient conditions with interval matrix inequality form are obtained for the general interval Lur'e type nonlinear control systems, thus the relationship between the stability of symmetrical interval matrix and the robust absolute stability of general interval Lur'e type nonlinear control systems is established.
Delay-dependent state feedback robust stabilization for uncertain singular time-delay systems
Gao Huanli; Xu Bugong
2008-01-01
The problem of robust stabilization for uncertain singular time-delay systems is studied.First,a new delay-dependent asymptotic stability criteria for normal singular time-delay systems is given,which is less conservative.Using this result,the problem of state feedback robust stabilization for uncertain singular time-delay systems is discussed.Finally,two examples are given to illustrate the effectiveness of the results.
Robustness analysis for real parametric uncertainty
Sideris, Athanasios
1989-01-01
Some key results in the literature in the area of robustness analysis for linear feedback systems with structured model uncertainty are reviewed. Some new results are given. Model uncertainty is described as a combination of real uncertain parameters and norm bounded unmodeled dynamics. Here the focus is on the case of parametric uncertainty. An elementary and unified derivation of the celebrated theorem of Kharitonov and the Edge Theorem is presented. Next, an algorithmic approach for robustness analysis in the cases of multilinear and polynomic parametric uncertainty (i.e., the closed loop characteristic polynomial depends multilinearly and polynomially respectively on the parameters) is given. The latter cases are most important from practical considerations. Some novel modifications in this algorithm which result in a procedure of polynomial time behavior in the number of uncertain parameters is outlined. Finally, it is shown how the more general problem of robustness analysis for combined parametric and dynamic (i.e., unmodeled dynamics) uncertainty can be reduced to the case of polynomic parametric uncertainty, and thus be solved by means of the algorithm.
Design of robust stability augmentation system for an airship using genetic algorithm
OUYANG Jin; QU Wei-dong; XI Yu-geng
2005-01-01
This paper presents the design of stability augmentation system (SAS) for the airship, which is robust with respect to parametric plant uncertainties. A robust pole placement approach is adopted in the design,which uses genetic algorithm (GA) as the optimization tool to derive the most robust solution of the state-feedback gain matrix K. The method can guarantee the resulting closed-loop poles to remain in a specified allocation region despite plant parameter uncertainty. Thus, the longitudinal stability of the airship is augmented by robustly assigning the closed-loop poles in a prescribed region of the left half s-plane.
Robust adaptive dynamic programming and feedback stabilization of nonlinear systems.
Jiang, Yu; Jiang, Zhong-Ping
2014-05-01
This paper studies the robust optimal control design for a class of uncertain nonlinear systems from a perspective of robust adaptive dynamic programming (RADP). The objective is to fill up a gap in the past literature of adaptive dynamic programming (ADP) where dynamic uncertainties or unmodeled dynamics are not addressed. A key strategy is to integrate tools from modern nonlinear control theory, such as the robust redesign and the backstepping techniques as well as the nonlinear small-gain theorem, with the theory of ADP. The proposed RADP methodology can be viewed as an extension of ADP to uncertain nonlinear systems. Practical learning algorithms are developed in this paper, and have been applied to the controller design problems for a jet engine and a one-machine power system.
Robust stability of uncertain neutral linear stochastic differential delay system
JIANG Ming-hui; SHEN Yi; LIAO Xiao-xin
2007-01-01
The LaSalle-type theorem for the neutral stochastic differential equations with delay is established for the first time and then applied to propose algebraic criteria of the stochastically asymptotic stability and almost exponential stability for the uncertain neutral stochastic differential systems with delay. An example is given to verify the effectiveness of obtained results.
Chen Qin
2013-01-01
Full Text Available This paper considers the problems of the robust stability and robust H∞ controller design for time-varying delay switched systems using delta operator approach. Based on the average dwell time approach and delta operator theory, a sufficient condition of the robust exponential stability is presented by choosing an appropriate Lyapunov-Krasovskii functional candidate. Then, a state feedback controller is designed such that the resulting closed-loop system is exponentially stable with a guaranteed H∞ performance. The obtained results are formulated in the form of linear matrix inequalities (LMIs. Finally, a numerical example is provided to explicitly illustrate the feasibility and effectiveness of the proposed method.
Liu Ping
2013-01-01
This paper deals with the finite-time stabilization of unified chaotic complex systems with known and unknown parameters.Based on the finite-time stability theory,nonlinear control laws are presented to achieve finite-time chaos control of the determined and uncertain unified chaotic complex systems,respectively.The two controllers are simple,and one of the uncertain unified chaotic complex systems is robust.For the design of a finite-time controller on uncertain unified chaotic complex systems,only some of the unknown parameters need to be bounded.Simulation results for the chaotic complex Lorenz,Lü and Chen systems are presented to validate the design and analysis.
无
2006-01-01
In this paper, using the theory of topological degree and Liapunov functional methods, the authors study the competitive neural networks with time delays and different time scales and present some criteria of global robust stability for this neural network model.
Dynamic compensator design for robust stability of linear uncertain systems
Yedavalli, R. K.
1986-01-01
This paper presents a robust linear dynamic compensator design algorithm for linear uncertain systems whose parameters vary within given bounded sets. The algorithm explicitly incorporates the structure of the uncertainty into the design procedure and utilizes the elemental perturbation bounds developed recently. The special cases of linear state feedback and measurement feedback controllers are considered and the relative trade offs are discussed. The design algorithm is illustrated with the help of a simple example.
Robust stability of time-varying uncertain systems with rational dependence on the uncertainty
2010-01-01
Robust stability of time-varying uncertain systems is a key problem in automatic control. This note considers the case of linear systems with rational dependence on an uncertain time-varying vector constrained in a polytope, which is typically addressed in the literature by using the linear fractional representation (LFR). A novel sufficient condition for robust stability is derived in terms of a linear matrix inequality (LMI) feasibility test by exploiting homogeneous polynomial Lyapunov fun...
A new result on global exponential robust stability of neural networks with time-varying delays
Jinliang SHAO; Tingzhu HUANG
2009-01-01
In this paper,the global exponential robust stability of neural networks with time-varying delays is investigated.By using nonnegative matrix theory and the Halanay inequality,a new sufficient condition for global exponential robust stability is presented.It is shown that the obtained result is different from or improves some existing ones reported in the literatures.Finally,some numerical examples and a simulation are given to show the effectiveness of the obtained result.
Jinxing Lin
2013-01-01
Full Text Available This paper is concerned with the problems of delay-dependent robust stability and stabilization for a class of continuous singular systems with time-varying delay in range and parametric uncertainties. The parametric uncertainties are assumed to be of a linear fractional form, which includes the norm bounded uncertainty as a special case and can describe a class of rational nonlinearities. In terms of strict linear matrix inequalities (LMIs, delay-range-dependent robust stability criteria for the unforced system are presented. Moreover, a strict LMI design approach is developed such that, when the LMI is feasible, a desired state feedback stabilizing controller can be constructed, which guarantees that, for all admissible uncertainties, the closed-loop dynamics will be regular, impulse free, and robustly asymptotically stable. Numerical examples are provided to demonstrate the effectiveness of the proposed methods.
Robust Adaptive Stabilization of Nonholonomic Mobile Robots with Bounded Disturbances
Gang Chen
2014-01-01
Full Text Available The stabilization problem of nonholonomic mobile robots with unknown system parameters and environmental disturbances is investigated in this paper. Considering the dynamic model and the kinematic model of mobile robots, the transverse function approach is adopted to construct an additional control parameter, so that the closed-loop system is not underactuated. Then the adaptive backstepping method and the parameter projection technique are applied to design the controller to stabilize the system. At last, simulation results demonstrate the effectiveness of our proposed controller schemes.
Robustness and Adaptiveness Analysis of Future Fleets
Wesolkowski, Slawomir; Whitacre, James M; Bender, Axel; Abbass, Hussein
2009-01-01
Making decisions about the structure of a future military fleet is a challenging task. Several issues need to be considered such as the existence of multiple competing objectives and the complexity of the operating environment. A particular challenge is posed by the various types of uncertainty that the future might hold. It is uncertain what future events might be encountered; how fleet design decisions will influence and shape the future; and how present and future decision makers will act based on available information, their personal biases regarding the importance of different objectives, and their economic preferences. In order to assist strategic decision-making, an analysis of future fleet options needs to account for conditions in which these different classes of uncertainty are exposed. It is important to understand what assumptions a particular fleet is robust to, what the fleet can readily adapt to, and what conditions present clear risks to the fleet. We call this the analysis of a fleet's strate...
Robust Utilization of Wind Turbine Flexibility for Grid Stabilization
Juelsgaard, Morten; Bendtsen, Jan Dimon; Wisniewski, Rafal
2012-01-01
This work considers the use of wind turbines for stabilizing an electrical grid, by employing temporary overproduction with respect to available power. We present a simple model describing a turbine, and show how the possible period of overproduction, can be maximized through a series of convex...
A Robust Stability and Control Theory for Hybrid Dynamical Systems
2006-09-30
IEEE Transactions on Automatic Control , to...Dual Linear Differential Inclusions", IEEE Transactions on Automatic Control , Vol. 51, Issue 4, April 2006, pp. 661-666. D. Liberzon and J. Hespanha...34Stabilization of nonlinear systems with limited information feedback", IEEE Transactions on Automatic Control , vol. 50, no. 6, pp. 910-915,
Nominal and robust stability regions of optimization-based PID controllers.
Ou, Linlin; Zhang, Weidong; Gu, Danying
2006-07-01
In recent decades, several optimization-based methods have been developed for the proportional-integral-derivative (PID) controller design, and the common feature of these methods is that the controller has only one adjustable parameter. To keep the closed-loop systems stable is an essential requirement for the optimization-based PID controllers. In almost all these methods, however, no exact stability region for the single adjustable parameter was sketched. In this paper, using the proposed analytical procedure based on the dual-locus diagram technique, explicit stability regions of the optimization-based PID controllers are derived for stable, integrating, and unstable processes with time delay in the nominal and perturbed cases, respectively. It is revealed that the proposed analytical procedure is effective for the determination of the nominal and robust stability regions and it offers simplicity and ease of mathematical calculations over other available stability analysis methods. The results in this paper provide some insight into the tuning of the optimization-based PID controllers.
Distributed Robustness Analysis of Interconnected Uncertain Systems Using Chordal Decomposition
Pakazad, Sina Khoshfetrat; Hansson, Anders; Andersen, Martin Skovgaard
2014-01-01
Large-scale interconnected uncertain systems commonly have large state and uncertainty dimensions. Aside from the heavy computational cost of performing robust stability analysis in a centralized manner, privacy requirements in the network can also introduce further issues. In this paper, we...... utilize IQC analysis for analyzing large-scale interconnected uncertain systems and we evade these issues by describing a decomposition scheme that is based on the interconnection structure of the system. This scheme is based on the so-called chordal decomposition and does not add any conservativeness...... to the analysis approach. The decomposed problem can be solved using distributed computational algorithms without the need for a centralized computational unit. We further discuss the merits of the proposed analysis approach using a numerical experiment....
Risk Analysis in Robust Control -- Making the Case for Probabilistic Robust Control
Chen, Xinjia; Zhou, Kemin
2007-01-01
This paper offers a critical view of the "worst-case" approach that is the cornerstone of robust control design. It is our contention that a blind acceptance of worst-case scenarios may lead to designs that are actually more dangerous than designs based on probabilistic techniques with a built-in risk factor. The real issue is one of modeling. If one accepts that no mathematical model of uncertainties is perfect then a probabilistic approach can lead to more reliable control even if it cannot guarantee stability for all possible cases. Our presentation is based on case analysis. We first establish that worst-case is not necessarily "all-encompassing." In fact, we show that for some uncertain control problems to have a conventional robust control solution it is necessary to make assumptions that leave out some feasible cases. Once we establish that point, we argue that it is not uncommon for the risk of unaccounted cases in worst-case design to be greater than that of the accepted risk in a probabilistic appro...
Robust stability in predictive control with soft constraints
Thomsen, Sven Creutz; Niemann, Hans Henrik; Poulsen, Niels Kjølstad
2010-01-01
In this paper we take advantage of the primary and dual Youla parameterizations for setting up a soft constrained model predictive control (MPC) scheme for which stability is guaranteed in face of norm-bounded uncertainties. Under special conditions guarantees are also given for hard input...... consisting of the primary and dual Youla parameter. This is included in the MPC optimization as a constraint on the induced gain of the optimization variable. We illustrate the method with a numerical simulation example....
Blanchini, F. [Universita di Udine (Italy); Carabelli, S. [Politecnico di Torino (Italy)
1994-12-31
We apply a technique recently proposed in literature for the robust stabilization of linear systems with time-varying uncertain parameters to a magnetic levitation system. This technique allows the construction of a polyhedral Lyapunov function and a linear variable-structure stabilizing controller.
2-D algebraic test for robust stability of time-delay systems with interval parameters
Xiao Yang
2006-01-01
The robust stability test of time-delay systems with interval parameters can be concluded into the robust stability of the interval quasipolynomials. It has been revealed that the robust stability of the quasipolynomials depends on that of their edge polynomials. This paper transforms the interval quasipolynomials into two-dimensional (2-D) interval polynomials (2-D s-z hybrid polynomials), proves that the robust stability of interval 2-D polynomials are sufficient for the stability of given quasipolynomials. Thus, the stability test of interval quasipolynomials can be completed in 2-D s-z domain instead of classical 1-D s domain. The 2-D s-z hybrid polynomials should have different forms under the time delay properties of given quasipolynomials. The stability test proposed by the paper constructs an edge test set from Kharitonov vertex polynomials to reduce the number of testing edge polynomials. The 2-D algebraic tests are provided for the stability test of vertex 2-D polynomials and edge 2-D polynomials family. To verify the results of the paper to be correct and valid, the simulations based on proposed results and comparison with other presented results are given.
Chunhui Liang
2014-01-01
Full Text Available Attitude stability analysis and robust control algorithms for spacecrafts orbiting irregular asteroids are investigated in the presence of model uncertainties and external disturbances. Rigid spacecraft nonlinear attitude models are considered and detailed attitude stability analysis of spacecraft subjected to the gravity gradient torque in an irregular central gravity field is included in retrograde orbits and direct orbits using linearized system model. The robust adaptive backstepping sliding mode control laws are designed to make the attitude of the spacecrafts stabilized and responded accurately to the expectation in the presence of disturbances and parametric uncertainties. Numerical simulations are included to illustrate the spacecraft performance obtained using the proposed control laws.
FREQUENCY DOMAIN CRITERIA FOR ROBUST D-STABILITY OF MIMO SYSTEMS BASED ON LMI METHOD
LI Hai-bin; WANG Zhi-zhen; WANG Long; LI Zhao-ping; LI Er-xiao
2006-01-01
The problem of checking robust D-stability of multi-in and multi-out (MIMO) systems was studied. Three system models were introduced, i.e. multilinear polynomial matrix, polytopic polynomial matrix and feedback system model. Furthermore, the convex property of each model with respect to the parametric uncertainties was estabilished respectively. Based on this, sufficient conditions for D-stability were expressed in terms of linear matrix inequalities (LMIs) involving only the convex vertices. Therefore, the robust D-stability was tested by solving an LMI optimal problem.
An improved robust stability result for uncertain neural networks with multiple time delays.
Arik, Sabri
2014-06-01
This paper proposes a new alternative sufficient condition for the existence, uniqueness and global asymptotic stability of the equilibrium point for the class of delayed neural networks under the parameter uncertainties of the neural system. The existence and uniqueness of the equilibrium point is proved by using the Homomorphic mapping theorem. The asymptotic stability of the equilibrium point is established by employing the Lyapunov stability theorems. The obtained robust stability condition establishes a new relationship between the network parameters of the system. We compare our stability result with the previous corresponding robust stability results derived in the past literature. Some comparative numerical examples together with some simulation results are also given to show the applicability and advantages of our result.
Robust stability in constrained predictive control through the Youla parameterisations
Thomsen, Sven Creutz; Niemann, Hans Henrik; Poulsen, Niels Kjølstad
2011-01-01
In this article we take advantage of the primary and dual Youla parameterisations to set up a soft constrained model predictive control (MPC) scheme. In this framework it is possible to guarantee stability in face of norm-bounded uncertainties. Under special conditions guarantees are also given...... arguments on the loop consisting of the primary and dual Youla parameter. This is included in the MPC optimisation as a constraint on the induced gain of the optimisation variable. We illustrate the method with a numerical simulation example....
Sørensen, John Dalsgaard; Rizzuto, Enrico; Narasimhan, Harikrishna
2012-01-01
More frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure combined with increased requirements to efficiency in design and execution followed by increased risk of human errors has made the need of requirements to robustness of structures......, a theoretical and risk-based framework is presented which facilitates the quantification of robustness, and thus supports the formulation of pre-normative guidelines....
Intuitive robust stability metric for PID control of self-regulating processes.
Arbogast, Jeffrey E; Beauregard, Brett M; Cooper, Douglas J
2008-10-01
Published methods establish how plant-model mismatch in the process gain and dead time impacts closed-loop stability. However, these methods assume no plant-model mismatch in the process time constant. The work presented here proposes the robust stability factor metric, RSF, to examine the effect of plant-model mismatch in the process gain, dead time, and time constant. The RSF is presented in two forms: an equation form and a visual form displayed on robustness plots derived from the Bode and Nyquist stability criteria. This understanding of robust stability is reinforced through visual examples of how closed-loop performance changes with various levels of plant-model mismatch. One example shows how plant-model mismatch in the time constant can impact closed-loop stability as much as plant-model mismatch in the gain and/or dead time. Theoretical discussion shows that the impact is greater for small dead time to time constant ratios. As the closed-loop time constant used in Internal Model Control (IMC) tuning decreases, the impact becomes significant for a larger range of dead time to time constant ratios. To complete the presentation, the RSF is used to compare the robust stability of IMC-PI tuning to other PI, PID, and PID with Filter tuning correlations.
Reliability-Based Robustness Analysis for a Croatian Sports Hall
Čizmar, Dean; Kirkegaard, Poul Henning; Sørensen, John Dalsgaard;
2011-01-01
This paper presents a probabilistic approach for structural robustness assessment for a timber structure built a few years ago. The robustness analysis is based on a structural reliability based framework for robustness and a simplified mechanical system modelling of a timber truss system. A comp...
Pan, Indranil; Ghosh, Soumyajit; Gupta, Amitava; 10.1109/PACC.2011.5978958
2012-01-01
Networked Control Systems (NCSs) are often associated with problems like random data losses which might lead to system instability. This paper proposes a method based on the use of variable controller gains to achieve maximum parametric robustness of the plant controlled over a network. Stability using variable controller gains under data loss conditions is analyzed using a suitable Linear Matrix Inequality (LMI) formulation. Also, a Particle Swarm Optimization (PSO) based technique is used to maximize parametric robustness of the plant.
Liu, Yanbin; Liu, Mengying; Sun, Peihua
2014-01-01
A typical model of hypersonic vehicle has the complicated dynamics such as the unstable states, the nonminimum phases, and the strong coupling input-output relations. As a result, designing a robust stabilization controller is essential to implement the anticipated tasks. This paper presents a robust stabilization controller based on the guardian maps theory for hypersonic vehicle. First, the guardian maps theories are provided to explain the constraint relations between the open subsets of complex plane and the eigenvalues of the state matrix of closed-loop control system. Then, a general control structure in relation to the guardian maps theories is proposed to achieve the respected design demands. Furthermore, the robust stabilization control law depending on the given general control structure is designed for the longitudinal model of hypersonic vehicle. Finally, a simulation example is provided to verify the effectiveness of the proposed methods.
PAN Li-xin; JIN Hong-zhang; WANG Lin-lin
2011-01-01
In the case of Autonomous Underwater Vehicle (AUV) navigating with low speed near water surface, a new method for design of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance. Robust control is applied, which is based on uncertain nonlinear horizontal motion model of AUV and the principle of zero speed fin stabilizer. Feedback linearization approach is used to transform the complex nonlinear system into a comparatively simple linear system. For parameter uncertainty of motion model, the controller is designed with mixed-sensitivity method based on H-infinity robust control theory. Simulation results show better robustness improved by this control method for roll stabilizing of AUV navigating near water surface.
Robustness Analysis for Value-Freezing Signal Temporal Logic
L. Brim
2013-08-01
Full Text Available In our previous work we have introduced the logic STL*, an extension of Signal Temporal Logic (STL that allows value freezing. In this paper, we define robustness measures for STL* by adapting the robustness measures previously introduced for Metric Temporal Logic (MTL. Furthermore, we present an algorithm for STL* robustness computation, which is implemented in the tool Parasim. Application of STL* robustness analysis is demonstrated on case studies.
Thermal stability of the C106 dye in robust electrolytes
Lund, Torben; Phuong, Nguyen Tuyet; Pechy, Peter
of the particles were prepared in electrolyte mixture B. The solutions were thermally treated at 80 ◦C for 0-2000 hours followed by dye extraction and analysis by HPLC coupled to UV/Vis and electro spray mass spectrometry [2]. Figure 1 shows the concentration profiles of C106 samples prepared under ambient...
基于运动矢量的鲁棒视频去抖动算法%Robust Video Stabilization Based on Motion Vectors
SONG Li; ZHOU Yuan-hua; ZHOU Jun
2005-01-01
This paper proposes a new robust video stabilization algorithm to remove unwanted vibrations in video sequences. A complete theoretical analysis is first established for video stabilization, providing a basis for new stabilization algorithm. Secondly, a new robust global motion estimation (GME) algorithm is proposed. Different from classic methods, the GME algorithm is based on spatial-temporal filtered motion vectors computed by block-matching methods. In addition, effective schemes are employed in correction phase to prevent boundary artifacts and error accumulation. Experiments show that the proposed algorithm has satisfactory stabilization effects while maintaining good tradeoff between speed and precision.
Robust fitting for pulsar timing analysis
Wang, Yidi; Keith, Michael J.; Stappers, Benjamin; Zheng, Wei
2017-07-01
We introduce a robust fitting method into pulsar timing analysis to cope with the non-Gaussian noise. The general maximum likelihood estimator (M-estimator) can resist the impact of non-Gaussian noise by employing convex and bounded loss functions. Three loss functions, including the Huber function, the Bisquare function and the Welsch function, are investigated. The Shapiro-Wilk test is employed to test whether the uncertainty in the observed times of arrival is drawn from a non-Gaussian distribution. Two simulations, where the non-Gaussian distribution is modelled as contaminated Gaussian distributions, are performed. It is found that M-estimators are unbiased and could achieve a root-mean-square error smaller than that obtained by the least square (LS) at the cost of a slightly higher computation complexity in a non-Gaussian environment. M-estimators are also applied to the real timing data of PSR J1713+0747. The results have shown that the fitting results of M-estimators are more accurate than those of LS and are closer to the result of very long baseline interferometry.
Reliable grading robust stabilization for uncertain time-varying systems via dynamic compensator
无
2002-01-01
A new general model for uncertain time-varying parameters and a new measure sensor failure model are presented, and the problems of both grading robust stabilization and reliable grading robust stabilization for such systems are studied. By the Lyapunov stability theory and matrix algebra method, some sufficient criteria for the above two control problems are established in quasi-linear matrix inequalities (Q-LMIS) forms. In view of linear matrix inequality (LMI) approach, a solving procedure for the Q-LMIS problem is proposed. The solvability of the Q-LMIS problem can be improved obviously by adding some LMI constraints to the Q-LMIS. Based on the two Q-LMIS criteria, a grading robust stable control strategy, namely, the controller with different energy is acted on the system with different uncertain parameter range, is presented. The numerical simulating results show that the grading robust stable control strategy for the robust stabilization of uncertain systems has important theoretical and practical significance.
Zhengguang WU; Wuneng ZHOU
2008-01-01
This paper investigates the problem of delay-dependent robust stabilization for uncertain singular systems with discrete and distributed delays in terms of linear matrix inequality(LMI)approach.Based on a delay-dependent stability condition for the nominal system,a state feedback controller is designed,which guarantees the resultant closedloop system to be robustly stable.An explicit expression for the desired controller is also given by solving a set of matrix inequalities.Some numerical examples are provided to illustrate the less conservativeness of the proposed methods.
Delay-dependent criteria for the robust stability of systems with time-varying delay
Min WU; Yong HE; Jinhua SHE
2003-01-01
The problem of delay-dependent robust stability for systems with titne-varying delay has been considered. By using the S-procedure and the Park' s inequality in the recent issue, a delay-dependent robust stability criterion which is less conservative than the previous results has been derived for time-delay systems with time-varying structured uncertainties. The same idea has also been easily extended to the systems with nonlinear perturbations. Numerical examples illustrated the effectiveness and the improvement of the proposed approach.
Robust Video Stabilization Using Particle Keypoint Update and l₁-Optimized Camera Path.
Jeon, Semi; Yoon, Inhye; Jang, Jinbeum; Yang, Seungji; Kim, Jisung; Paik, Joonki
2017-02-10
Acquisition of stabilized video is an important issue for various type of digital cameras. This paper presents an adaptive camera path estimation method using robust feature detection to remove shaky artifacts in a video. The proposed algorithm consists of three steps: (i) robust feature detection using particle keypoints between adjacent frames; (ii) camera path estimation and smoothing; and (iii) rendering to reconstruct a stabilized video. As a result, the proposed algorithm can estimate the optimal homography by redefining important feature points in the flat region using particle keypoints. In addition, stabilized frames with less holes can be generated from the optimal, adaptive camera path that minimizes a temporal total variation (TV). The proposed video stabilization method is suitable for enhancing the visual quality for various portable cameras and can be applied to robot vision, driving assistant systems, and visual surveillance systems.
Robust stabilization using LMI techniques of neutral time-delay systems subject to input saturation
El Fezazi, Nabil; El Haoussi, Fatima; Houssaine Tissir, El; Alvarez, Teresa; Tadeo, Fernando
2017-01-01
The robust stabilization of uncertain saturated neutral systems with state delay is solved in this paper: based on a free weighting matrix approach, sufficient conditions are obtained via an LMI formulation. From these conditions, state feedback gains that ensure stability for the largest set of admissible initial conditions can be calculated solving optimization problems with LMI constraints. Some applications of this methodology to feedback control are then presented and compared with previous results in the literature.
Robust Stability of Scaled-Four-Channel Teleoperation with Internet Time-Varying Delays
Emma Delgado
2016-04-01
Full Text Available We describe the application of a generic stability framework for a teleoperation system under time-varying delay conditions, as addressed in a previous work, to a scaled-four-channel (γ-4C control scheme. Described is how varying delays are dealt with by means of dynamic encapsulation, giving rise to mu-test conditions for robust stability and offering an appealing frequency technique to deal with the stability robustness of the architecture. We discuss ideal transparency problems and we adapt classical solutions so that controllers are proper, without single or double differentiators, and thus avoid the negative effects of noise. The control scheme was fine-tuned and tested for complete stability to zero of the whole state, while seeking a practical solution to the trade-off between stability and transparency in the Internet-based teleoperation. These ideas were tested on an Internet-based application with two Omni devices at remote laboratory locations via simulations and real remote experiments that achieved robust stability, while performing well in terms of position synchronization and force transparency.
Robust exponential stability and stabilization of linear uncertain polytopic time-delay systems
Nam PHAN T.; Phat VU N.
2008-01-01
This paper proposes new sufficient conditions for the exponential stability and stabilization.of linear uncertain polytopic time-delay systems.The conditions for exponential stability are expressed in terms of Kharitonov-type linear matrix inequalities(LMIs)and we develop control design methods based on UMIs for solving stabilization problem.Our method consists of a combination of the LMI approach and the use of parameter-dependent Lyapunov funcfionals,which allows to compute simultaneously the two bounds that characterize the exponetial stability rate of the solution.Numerical examples illustrating the conditions are given.
π型感应电能传输系统的鲁棒稳定性分析%Robust Stability Analysis of π-type Inductive Power Transfer System
李砚玲; 孙跃; 戴欣
2011-01-01
为分析π型感应电能传输系统的鲁棒稳定性,首先采用基于频域分解的方法建立对象的广义状态空间平均(GSSA)模型,再考虑系统中的频率不确定性,通过线性分式变换分离对象的摄动和标称部分,将不确定模型进一步转化为含摄动反馈的线性动力学系统.最后,采用基于结构奇异值的μ方法分析了频率撮动对系统稳定性的影响以及系统保持稳定所容许的最大摄动,并利用仿真结果验证了μ理论分析的准确性.%In order to analyze the robust stability of π -type inductive power transfer system, a general-ized state space averaging (GSSA) model based on frequency domain resolving method was first built. An uncertain model was then represented as a linear dynamic system with perturbation feedback, which took into account the frequency uncertainty by separating the object into nominal part and perturbation part with the method of linear fractional transformation. The μ method based on the structure singular value was used to analyze the effect of frequency perturbation on system stability as well as the maximum pertur-bation allowed for maintaining system stability. The simulation results have verified the accuracy of the μ theory analyses.
Robust Stabilization for Uncertain Control Systems Using Piecewise Quadratic Lyapunov Functions
无
2002-01-01
The sufficient condition based on piecewise quadratic simultaneous Lyapunov functions for robust stabilizationof uncertain control systems via a constant linear state feedback control law is obtained. The objective is to use a robuststability criterion that is less conservative than the usual quadratic stability criterion. Numerical example is given, show-ing the advanteges of the proposed method.
Oostveen, JC; Curtain, RF
1997-01-01
We solve the problem of robust stabilization with respect to normalized coprime factor perturbations for a new class of infinite-dimensional systems with finite-rank, colocated actuators and sensors and possibly infinitely many unstable eigenvalues on the imaginary axis. Such systems are often used
Robust stabilization with H∞ performance for a class of linear parameter-dependent systems
Hamid Reza Karimi
2006-01-01
Full Text Available We focus on the issue of robust stabilization with H∞ performance for a class of linear time-invariant parameter-dependent systems under norm-bounded nonlinear uncertainties. By combining the idea of polynomially parameter-dependent quadratic Lyapunov functions and linear matrix inequalities formulations, some parameter-independent conditions with high precision are given to guarantee robust asymptotic stability and robust disturbance attenuation of the linear time-invariant parameter-dependent system in the presence of norm-bounded nonlinear uncertainties. The parameter-dependent state-feedback control is designed based on the Hamilton-Jacobi-Isaac (HJI method. The applicability of the proposed design method is illustrated in a simple example.
Qiang Yang
2016-01-01
Full Text Available Based on adaptive nonlinear damping, a novel decentralized robust adaptive output feedback stabilization comprising a decentralized robust adaptive output feedback controller and a decentralized robust adaptive observer is proposed for a large-scale interconnected nonlinear system with general uncertainties, such as unknown nonlinear parameters, bounded disturbances, unknown nonlinearities, unmodeled dynamics, and unknown interconnections, which are nonlinear function of not only states and outputs but also unmodeled dynamics coming from other subsystems. In each subsystem, the proposed stabilization only has two adaptive parameters, and it is not needed to generate an additional dynamic signal or estimate the unknown parameters. Under certain assumptions, the proposed scheme guarantees that all the dynamic signals in the interconnected nonlinear system are bounded. Furthermore, the system states and estimate errors can approach arbitrarily small values by choosing the design parameters appropriately large. Finally, simulation results illustrated the effectiveness of the proposed scheme.
Robust H∞ stabilization of a hard disk drive system with a single-stage actuator
Harno, Hendra G.; Kiin Woon, Raymond Song
2015-04-01
This paper considers a robust H∞ control problem for a hard disk drive system with a single stage actuator. The hard disk drive system is modeled as a linear time-invariant uncertain system where its uncertain parameters and high-order dynamics are considered as uncertainties satisfying integral quadratic constraints. The robust H∞ control problem is transformed into a nonlinear optimization problem with a pair of parameterized algebraic Riccati equations as nonconvex constraints. The nonlinear optimization problem is then solved using a differential evolution algorithm to find stabilizing solutions to the Riccati equations. These solutions are used for synthesizing an output feedback robust H∞ controller to stabilize the hard disk drive system with a specified disturbance attenuation level.
MohammadReza Davoodi
2009-12-01
Full Text Available This paper offers a design procedure for robust stability, robust H-infinity control and robust H2 control via dynamic output feedback for a class of uncertain linear systems. The uncertainties are of norm bounded type. Then in order to support a high-speed energy storage flywheel, these procedures are applied to an active radial magnetic bearing system. The state space matrices of this controller are the solution of some linear matrix inequalities (LMIs.
Robust stabilizing first-order controllers for a class of time delay systems.
Saadaoui, Karim; Testouri, Sana; Benrejeb, Mohamed
2010-07-01
In this paper, stabilizing regions of a first-order controller for an all poles system with time delay are computed via parametric methods. First, the admissible ranges of one of the controller's parameters are obtained. Then, for a fixed value of this parameter, stabilizing regions in the remaining two parameters are determined using the D-decomposition method. Phase and gain margin specifications are then included in the design. Finally, robust stabilizing first-order controllers are determined for uncertain plants with an interval type uncertainty in the coefficients. Examples are given to illustrate the effectiveness of the proposed method.
Kanit Mukdasai
2012-01-01
Full Text Available This paper investigates the problem of robust exponential stability for linear parameter-dependent (LPD systems with discrete and distributed time-varying delays and nonlinear perturbations. Parameter dependent Lyapunov-Krasovskii functional, Leibniz-Newton formula, and linear matrix inequality are proposed to analyze the stability. On the basis of the estimation and by utilizing free-weighting matrices, new delay-dependent exponential stability criteria are established in terms of linear matrix inequalities (LMIs. Numerical examples are given to demonstrate the effectiveness and less conservativeness of the proposed methods.
Ratschbacher, Lothar; Gallego, Jose; Ghosh, Sutapa; Alavi, Seyed; Alt, Wolfgang; Martinez-Dorantes, Miguel; Meschede, Dieter
2016-04-01
Fiber Fabry-Perot cavities, formed by micro-machined mirrors on the end-facets of optical fibers, are used in an increasing number of technical and scientific applications. Some of the most promising areas of application of these optical micro-resonators with high finesse and small mode volume are in the field of quantum communication and information. The resonator-enhanced light-matter interaction, for instance, provide basis for the realization of efficient optical interfaces between stationary matter-based quantum nodes and flying single-photon qubits. To date fiber Fabry-Perot cavities have been successfully applied in experiments interfacing single photons with a wide range of quantum systems, including cold atoms, ions and solid state emitters as well as quantum optomechanical experiments. Here we address some important practical questions that arise during the experimental implementation of high finesse fiber Fabry-Perot cavities: How can optimal fiber cavity alignment be achieved and how can the efficiency of coupling light from the optical fibers to the cavity mode and vice versa be characterized? How should optical fiber cavities be constructed and stabilized to fulfill their potential for miniaturization and integration into robust scientific and technological devices that can operate outside of dedicated laboratory environments in the future? The first two questions we answer with an analytic mode matching calculation that relates the alignment dependent fiber-to-cavity mode-matching efficiency to the easily measurable dip in the reflected light power at the cavity resonance. Our general analysis provides a simple recipe for the optimal alignment of fiber Fabry-Perot cavities and moreover for the first time explains the asymmetry in their reflective line shapes. The latter question we explore by investigating a novel, intrinsically rigid fiber cavity design that makes use of the high passive stability of a monolithic cavity spacer and employs thermal
Nevsky, A; Alighanbari, S; Chen, Q-F; Ernsting, I; Vasilyev, S; Schiller, S; Barwood, G; Gill, P; Poli, N; Tino, G M
2013-11-15
We have demonstrated a compact, robust device for simultaneous absolute frequency stabilization of three diode lasers whose carrier frequencies can be chosen freely relative to the reference. A rigid ULE multicavity block is employed, and, for each laser, the sideband locking technique is applied. A small lock error, computer control of frequency offset, wide range of frequency offset, simple construction, and robust operation are the useful features of the system. One concrete application is as a stabilization unit for the cooling and trapping lasers of a neutral-atom lattice clock. The device significantly supports and improves the clock's operation. The laser with the most stringent requirements imposed by this application is stabilized to a line width of 70 Hz, and a residual frequency drift less than 0.5 Hz/s. The carrier optical frequency can be tuned over 350 MHz while in lock.
Stabilization and regulation of nonlinear systems a robust and adaptive approach
Chen, Zhiyong
2015-01-01
The core of this textbook is a systematic and self-contained treatment of the nonlinear stabilization and output regulation problems. Its coverage embraces both fundamental concepts and advanced research outcomes and includes many numerical and practical examples. Several classes of important uncertain nonlinear systems are discussed. The state-of-the art solution presented uses robust and adaptive control design ideas in an integrated approach which demonstrates connections between global stabilization and global output regulation allowing both to be treated as stabilization problems. Stabilization and Regulation of Nonlinear Systems takes advantage of rich new results to give students up-to-date instruction in the central design problems of nonlinear control, problems which are a driving force behind the furtherance of modern control theory and its application. The diversity of systems in which stabilization and output regulation become significant concerns in the mathematical formulation of practical contr...
Stability analysis of ferrofluids
Katharina Duda
2015-09-01
Full Text Available Superparamagnetic iron oxides (SPIOs are used as tracer for the new imaging technique Magnetic Particle Imaging. The stability of ferrofluids for medical application has a great importance, in addition to the particle size. The shell material, which protects the iron core prior from agglomeration and sedimentation, can be degraded by various processes. Another important aspect of stability is the constant performance of magnetisation. Therefore, the measurement of the magnetisation of the particles must be controlled in order to ensure the stability of the samples.
Robustness analysis method for orbit control
Zhang, Jingrui; Yang, Keying; Qi, Rui; Zhao, Shuge; Li, Yanyan
2017-08-01
Satellite orbits require periodical maintenance due to the presence of perturbations. However, random errors caused by inaccurate orbit determination and thrust implementation may lead to failure of the orbit control strategy. Therefore, it is necessary to analyze the robustness of the orbit control methods. Feasible strategies which are tolerant to errors of a certain magnitude can be developed to perform reliable orbit control for the satellite. In this paper, first, the orbital dynamic model is formulated by Gauss' form of the planetary equation using the mean orbit elements; the atmospheric drag and the Earth's non-spherical perturbations are taken into consideration in this model. Second, an impulsive control strategy employing the differential correction algorithm is developed to maintain the satellite trajectory parameters in given ranges. Finally, the robustness of the impulsive control method is analyzed through Monte Carlo simulations while taking orbit determination error and thrust error into account.
Robustness analysis for a class of nonlinear descriptor systems
吴敏; 张凌波; 何勇
2004-01-01
The robustness analysis problem of a class of nonlinear descriptor systems is studied. Nonlinear matrix inequality which has the good computation property of convex feasibility is employed to derive some sufficient conditions to guarantee that the nonlinear descriptor systems have robust disturbance attenuation performance, which avoids the computational difficulties in conversing nonlinear matrix and Hamilton-Jacobi inequality. The computation property of convex feasibility of nonlinear matrix inequality makes it possible to apply the results of nonlinear robust control to practice.
Analysis and Synthesis of Robust Data Structures
1990-08-01
1.3.2 Multiversion Software. .. .. .. .. .. .... .. ... .. ...... 5 1.3.3 Robust Data Structure .. .. .. .. .. .. .. .. .. ... .. ..... 6 1.4...context are 0 multiversion software, which is an adaptation oi N-modulo redundancy (NMR) tech- nique. * recovery blocks, which is an adaptation of...implementations using these features for such a hybrid approach. 1.3.2 Multiversion Software Avizienis [AC77] was the first to adapt NMR technique into
Reliability-Based Robustness Analysis for a Croatian Sports Hall
Čizmar, Dean; Kirkegaard, Poul Henning; Sørensen, John Dalsgaard
2011-01-01
. A complex timber structure with a large number of failure modes is modelled with only a few dominant failure modes. First, a component based robustness analysis is performed based on the reliability indices of the remaining elements after the removal of selected critical elements. The robustness...
Robust methods for multivariate data analysis A1
Frosch, Stina; Von Frese, J.; Bro, Rasmus
2005-01-01
Outliers may hamper proper classical multivariate analysis, and lead to incorrect conclusions. To remedy the problem of outliers, robust methods are developed in statistics and chemometrics. Robust methods reduce or remove the effect of outlying data points and allow the ?good? data to primarily...
Jinxing Lin; Shumin Fei; Jiong Shen
2010-01-01
The problems of robust stability and stabilization via memoryless state feedback for a class of discrete-time switched singular systems with time-varying delays and linear fractional uncertainties are investigated.By constructing a novel switched Lyapunov-Krasovskii functional,a delay-dependent criterion for the unforced system to be regular,causal and uniformly asymptotically stable is established in terms of linear matrix inequalities(LMIs).An explicit expression for the desired memoryless state feedback stabilization controller is also given.The merits of the proposed criteria lie in their less conservativeness and relative simplicity,which are achieved by considering additionally useful terms(ignored in previous methods)when estimating the upper bound of the forward difference of the Lyapunov-Krasovskii functional and by avoiding utilizing any model augmentation transformation.Some numerical examples are provided to illustrate the validity of the proposed methods.
Huaicheng YAN; Xinhan HUANG; Min WANG
2007-01-01
In this paper, delay-dependent robust stability for a class of uncertain networked control systems (NCSs)with multiple state time-delays is investigated. Modeling of multi-input and multi-output (MIMO) NCSs with networkinduced delays and uncertainties through new methods are proposed. Some new stability criteria in terms of LMIs are derived by using Lyapunov stability theory combined with linear matrix inequalities (LMIs) techniques. We analyze the delay-dependent asymptotic stability and obtain maximum allowable delay bound (MADB) for the NCSs with the proposed methods. Compared with the reported results, the proposed results obtain a much less conservative MADB which are more general. Numerical example and simulation is used to illustrate the effectiveness of the proposed methods.
Global robust asymptotic stability of variable-time impulsive BAM neural networks.
Saylı, Mustafa; Yılmaz, Enes
2014-12-01
In this paper, the global robust asymptotic stability of the equilibrium point for a more general class of bidirectional associative memory (BAM) neural networks with variable time of impulses is addressed. Unlike most existing studies, the case of non-fix time impulses is focused on in the present study. By means of B-equivalence method, which was introduced in Akhmet (2003, 2005, 2009, 2010), Akhmet and Perestyuk (1990) and Akhmet and Turan (2009), we reduce these networks to a fix time impulsive neural networks system. Sufficient conditions ensuring the existence, uniqueness and global robust asymptotic stability of the equilibrium point are obtained by employing an appropriate Lyapunov function and linear matrix inequality (LMI). Finally, we give one illustrative example to show the effectiveness of the theoretical results.
Robust D-Stability Controller Design for a Ducted Fan Unmanned Aerial Vehicle
Xiao-lu Ren
2014-01-01
Full Text Available This paper deals with the aerodynamic modeling of a small ducted fan UAV and the problem of attitude stabilization when the parameter of the vehicle is varied. The main aerodynamic model of the hovering flight UAV is first presented. Then, an attitude control is designed from a linearization of the dynamic model around the hovering flight, which is based on the H∞ output feedback control theory with D-stability. Simulation results show that such method has good robustness to the attitude system. They can meet the requirements of attitude control and verify further the feasibility of such a control strategy.
Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal
2012-01-01
This paper addresses the robust stability and control problem of uncertain piecewise linear switched systems where, instead of the conventional Carathe ́odory solutions, we allow for Filippov solutions. In other words, in contrast to the previous studies, solutions with infinite switching in finite...... time along the facets and on faces of arbitrary dimensions are also taken into account. Firstly, based on earlier results, the stability problem of piecewise linear systems with Filippov solutions is translated into a number of linear matrix inequality feasibility tests. Subsequently, a set of matrix...
On Robust Stability of a Class of Uncertain Nonlinear Systems with Time-Varying Delay
NIAN Xiao-hong
2002-01-01
The problem of robust stability of a class of uncertain nonlinear dynamical systems with time-delay is considered. Based on the assumption that the nominal system is stable, some sufficient conditions onrobust stability of uncertain nonlinear dynamical systems with time-delay are derived. Some analytical methods and a type of Lyapunov functional are used to investigate such sufficient conditions. The results obtained in this paper are applicable to perturbed time-delay systems with unbounded time-varying delay.Some previous results are improved and a numerical example is given to demonstrate the validity of our results.
Flight control application of new stability robustness bounds for linear uncertain systems
Yedavalli, Rama K.
1993-01-01
This paper addresses the issue of obtaining bounds on the real parameter perturbations of a linear state-space model for robust stability. Based on Kronecker algebra, new, easily computable sufficient bounds are derived that are much less conservative than the existing bounds since the technique is meant for only real parameter perturbations (in contrast to specializing complex variation case to real parameter case). The proposed theory is illustrated with application to several flight control examples.
Sandeep Gupta
2015-01-01
Full Text Available A current source converter (CSC based static synchronous compensator (STATCOM is a shunt flexible AC transmission system (FACTS device, which has a vital role as a stability support for small and large transient instability in an interconnected power network. This paper investigates the impact of a novel and robust pole-shifting controller for CSC-STATCOM to improve the transient stability of the multimachine power system. The proposed algorithm utilizes CSC based STATCOM to supply reactive power to the test system to maintain the transient stability in the event of severe contingency. Firstly, modeling and pole-shifting controller design for CSC based STATCOM are stated. After that, we show the impact of the proposed method in the multimachine power system with different disturbances. Here, applicability of the proposed scheme is demonstrated through simulation in MATLAB and the simulation results show an improvement in the transient stability of multimachine power system with CSC-STATCOM. Also clearly shown, the robustness and effectiveness of CSC-STATCOM are better rather than other shunt FACTS devices (SVC and VSC-STATCOM by comparing the results in this paper.
Liang, Yao; Yamaura, Hiroshi; Ouyang, Huajiang
2017-06-01
As friction couples tangential and lateral degrees-of-freedom of a structure at contact interfaces, the resulting asymmetric dynamic system is prone to dynamic instability. Using state-feedback control, such a frictional asymmetric system can be stabilized through assigning the system desirable eigenvalues; but uncertainties in system parameters can cause assigned eigenvalues to deviate from desired locations and thus stability may be lost. This study presents a robust stabilization method that assigns both desirable eigenvalues and their sensitivities and thus render assigned eigenvalues stable and insensitive to perturbations in uncertain contact parameters (the friction coefficient, contact damping, and contact stiffness). This method utilizes receptances of the corresponding symmetric part of the asymmetric system. The optimal control input location is first determined by minimizing the Frobenius norm of the normalized eigen-sensitivity matrix. The normalized eigen-sensitivities indicate that the friction coefficient and contact stiffness intrinsically have similar crucial effects on the stability of the system. To demonstrate the application of the proposed control method, the eigen-sensitivities with respect to only the friction coefficient are assigned. A constrained over-determined least-squares problem is solved to assign both required eigenvalues and eigen-sensitivities. Numerical examples validate the effectiveness of the proposed robust control scheme by Monte Carlo simulations.
A new delay-independent condition for global robust stability of neural networks with time delays.
Samli, Ruya
2015-06-01
This paper studies the problem of robust stability of dynamical neural networks with discrete time delays under the assumptions that the network parameters of the neural system are uncertain and norm-bounded, and the activation functions are slope-bounded. By employing the results of Lyapunov stability theory and matrix theory, new sufficient conditions for the existence, uniqueness and global asymptotic stability of the equilibrium point for delayed neural networks are presented. The results reported in this paper can be easily tested by checking some special properties of symmetric matrices associated with the parameter uncertainties of neural networks. We also present a numerical example to show the effectiveness of the proposed theoretical results.
Robust Output Feedback Stabilization of a Field-Sensed Magnetic Suspension System
Jen-Hsing Li
2013-01-01
Full Text Available The magnetic suspension system (MSS is very important in many engineering applications. This paper proposes the dynamic output feedback control of a field-sensed MSS (FSMSS. Subsequently, the mathematical model of the MSS is described by discrete-time systems. Ideally, the coefficients of a nominal polynomial can precisely determine the Schur stability. But in reality, the coefficients may contain uncertainties due to reasons such as computational errors. Therefore, there is a need to address the problem of robust stability for discrete-time systems. In this paper, the size of allowable perturbation in polynomial coefficient space was estimated for the output feedback control of the MSS. The ℓ∞-norm and a lower bound for the size of the Schur stability hypercube are provided in this paper.
Jeevanandham Arumugam
2009-01-01
Full Text Available In this paper a classical lead-lag power system stabilizer is used for demonstration. The stabilizer parameters are selected in such a manner to damp the rotor oscillations. The problem of selecting the stabilizer parameters is converted to a simple optimization problem with an eigen value based objective function and it is proposed to employ simulated annealing and particle swarm optimization for solving the optimization problem. The objective function allows the selection of the stabilizer parameters to optimally place the closed-loop eigen values in the left hand side of the complex s-plane. The single machine connected to infinite bus system and 10-machine 39-bus system are considered for this study. The effectiveness of the stabilizer tuned using the best technique, in enhancing the stability of power system. Stability is confirmed through eigen value analysis and simulation results and suitable heuristic technique will be selected for the best performance of the system.
Robust numerical phase stabilization for long-range swept-source optical coherence tomography.
Song, Shaozhen; Xu, Jingjiang; Men, Shaojie; Shen, Tueng T; Wang, Ruikang K
2017-05-09
A novel phase stabilization technique is demonstrated with significant improvement in the phase stability of a micro-electromechanical (MEMS) vertical cavity surface-emitting laser (VCSEL) based swept-source optical coherence tomography (SS-OCT) system. Without any requirements of hardware modifications, the new fully numerical phase stabilization technique features high tolerance to acquisition jitter, and significantly reduced budget in computational effort. We demonstrate that when measured with biological tissue, this technique enables a phase sensitivity of 89 mrad in highly scattering tissue, with image ranging distance of up to 12.5 mm at A-line scan rate of 100.3 kHz. We further compare the performances delivered by the phase-stabilization approach with conventional numerical approach for accuracy and computational efficiency. Imaging result of complex signal-based optical coherence tomography angiography (OCTA) and Doppler OCTA indicate that the proposed phase stabilization technique is robust, and efficient in improving the image contrast-to-noise ratio and extending OCTA depth range. The proposed technique can be universally applied to improve phase-stability in generic SS-OCT with different scale of scan rates without a need for special treatment. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Quéro, Anthony; Jousse, Cyril; Lequart-Pillon, Michelle; Gontier, Eric; Guillot, Xavier; Courtois, Bernard; Courtois, Josiane; Pau-Roblot, Corinne
2014-11-01
Plant metabolite profiling is commonly carried out by GC-MS of methoximated trimethylsilyl (TMS) derivatives. This technique is robust and enables a library search for spectra produced by electron ionization. However, recent articles have described problems associated with the low stability of some TMS derivatives. This limits the use of GC-MS for metabolomic studies that need large sets of qualitative and quantitative analyses. The aim of this work is to determine the experimental conditions in which the stability of TMS derivatives could be improved. This would facilitate the analysis of the large-scale experimental designs needed in the metabolomics approach. For good repeatability, the sampling conditions and the storage temperature of samples during analysis were investigated. Multiple injections of one sample from one vial led to high variations while injection of one sample from different vials improved the analysis. However, before injection, some amino acid TMS derivatives were degraded during the storage of vials in the autosampler. Only 10% of the initial quantity of glutamine 3 TMS and glutamate 3 TMS and 66% of α-alanine 2 TMS was detected 48 h after derivatization. When stored at 4 °C until injection, all TMS derivatives remained stable for 12 h; at -20 °C, they remained stable for 72 h. From the integration of all these results, a detailed analytical procedure is thus proposed. It enables a robust quantification of polar metabolites, useful for further plant metabolomics studies using GC-MS.
嵇小辅; 杨泽斌; 孙玉坤; 苏宏业
2008-01-01
The problem of roust stabilization for linear time-varying uncertain periodic descriptor systems is revisited. Based on the concept of robust stability for linear time-varying uncer-tain periodic descriptor systems, a necessary and sufficient con-dition for robust stability is put forward. The robust stabiliza-tion problem is also studied and the corresponding necessary and sufficient condition is given using the notation of dual system.The obtained matrix inequality conditions can be transformed to linear matrix inequality ones with the introduction of some free matrices, which makes the analysis and design procedure simple and reliable.
Robust Controller Design Using the Nevanlinna-Pick Interpolation in Gyro Stabilized Pod
Bin Liu
2010-01-01
Full Text Available The sensitivity minimization of feedback system is solved based on the theory of Nevanlinna-Pick interpolation with degree constraint without using weighting functions. More details of the dynamic characteristic of second-order system investigated, which is determined by the location of spectral zeroes, the upper bound γ of S, the length of the spectral radius and the additional interpolation constraints. And the guidelines on how to tune the design parameters are provided. Gyro stabilized pod as a typical tracking system is studied, which is based on the typical structure of two-axis and four-frame. The robust controller is designed based on Nevanlinna-Pick interpolation with degree constraint. When both friction of LuGre model and disturbance exist, the closed-loop system has stronger disturbance rejection ability and high tracking precision. Numerical examples illustrate the potential of the method in designing robust controllers with relatively low degrees.
Buffered Qualitative Stability explains the robustness and evolvability of transcriptional networks.
Albergante, Luca; Blow, J Julian; Newman, Timothy J
2014-09-02
The gene regulatory network (GRN) is the central decision-making module of the cell. We have developed a theory called Buffered Qualitative Stability (BQS) based on the hypothesis that GRNs are organised so that they remain robust in the face of unpredictable environmental and evolutionary changes. BQS makes strong and diverse predictions about the network features that allow stable responses under arbitrary perturbations, including the random addition of new connections. We show that the GRNs of E. coli, M. tuberculosis, P. aeruginosa, yeast, mouse, and human all verify the predictions of BQS. BQS explains many of the small- and large-scale properties of GRNs, provides conditions for evolvable robustness, and highlights general features of transcriptional response. BQS is severely compromised in a human cancer cell line, suggesting that loss of BQS might underlie the phenotypic plasticity of cancer cells, and highlighting a possible sequence of GRN alterations concomitant with cancer initiation.
Denoising and robust nonlinear wavelet analysis
Bruce, Andrew G.; Donoho, David L.; Gao, Hong-Ye; Martin, R. D.
1994-03-01
In a series of papers, Donoho and Johnstone develop a powerful theory based on wavelets for extracting non-smooth signals from noisy data. Several nonlinear smoothing algorithms are presented which provide high performance for removing Gaussian noise from a wide range of spatially inhomogeneous signals. However, like other methods based on the linear wavelet transform, these algorithms are very sensitive to certain types of non-Gaussian noise, such as outliers. In this paper, we develop outlier resistant wavelet transforms. In these transforms, outliers and outlier patches are localized to just a few scales. By using the outlier resistant wavelet transform, we improve upon the Donoho and Johnstone nonlinear signal extraction methods. The outlier resistant wavelet algorithms are included with the 'S+WAVELETS' object-oriented toolkit for wavelet analysis.
Analysis of Robust Quasi-deviances for Generalized Linear Models
Eva Cantoni
2004-04-01
Full Text Available Generalized linear models (McCullagh and Nelder 1989 are a popular technique for modeling a large variety of continuous and discrete data. They assume that the response variables Yi , for i = 1, . . . , n, come from a distribution belonging to the exponential family, such that E[Yi ] = ?i and V[Yi ] = V (?i , and that ?i = g(?i = xiT?, where ? ? IR p is the vector of parameters, xi ? IR p, and g(. is the link function. The non-robustness of the maximum likelihood and the maximum quasi-likelihood estimators has been studied extensively in the literature. For model selection, the classical analysis-of-deviance approach shares the same bad robustness properties. To cope with this, Cantoni and Ronchetti (2001 propose a robust approach based on robust quasi-deviance functions for estimation and variable selection. We refer to that paper for a deeper discussion and the review of the literature.
Robust Global Control Strategies for Improvement of Angular Stability using FACTS and HVDC Devices
Agnihotri, P.; Kulkarni, A. M.; Gole, A. M.
2013-05-01
System-wide feedback signals made available by Wide-Area Measurement Systems technology can be used in FACTS/HVDC based controllers for the improvement of angular stability. These global signals can facilitate the efficient use of controller effort to stabilize critical swing modes. This paper introduces a restricted global strategy which involves the use of specific global feedback signals which are available at the HVDC/FACTS locations. The strategy is expected to be robust to changes in the power grid as well as communication uncertainties. This paper presents a heuristic introduction to this strategy using a circuit analogy of a simplified model of a power system. Preliminary results on a small system are also presented.
Power System Stabilizer Based on Robust H∞ Controller for Low Frequency Operating Range
Ali Mohamed Yousef
2012-05-01
Full Text Available The aim of study is designed of Power System Stabilizer (PSS based on H4 approach for power system stabilization. The uncertainties in power system modeling and operations are considered at designing of H∞ PSS. The bounds of power system parameters are determined over a wide range of low frequency operating conditions. These bounds are used to design a robust H∞ PSS. A sample power system composed a synchronous generator connected to infinite bus through transmission line is simulated. The digital H∞ PSS can achieve good performance over a wide range of operating conditions. A comparison between power system responses at variety of operating conditions using the proposed H∞ PSS and Linear Quadratic Regulator LQR control have been done. H2 PSS is designed and compared with the proposed controller.
Robust Stabilization of T-S Fuzzy Stochastic Descriptor Systems via Integral Sliding Modes.
Li, Jinghao; Zhang, Qingling; Yan, Xing-Gang; Spurgeon, Sarah K
2017-09-19
This paper addresses the robust stabilization problem for T-S fuzzy stochastic descriptor systems using an integral sliding mode control paradigm. A classical integral sliding mode control scheme and a nonparallel distributed compensation (Non-PDC) integral sliding mode control scheme are presented. It is shown that two restrictive assumptions previously adopted developing sliding mode controllers for Takagi-Sugeno (T-S) fuzzy stochastic systems are not required with the proposed framework. A unified framework for sliding mode control of T-S fuzzy systems is formulated. The proposed Non-PDC integral sliding mode control scheme encompasses existing schemes when the previously imposed assumptions hold. Stability of the sliding motion is analyzed and the sliding mode controller is parameterized in terms of the solutions of a set of linear matrix inequalities which facilitates design. The methodology is applied to an inverted pendulum model to validate the effectiveness of the results presented.
Slope Stability Analysis Using GIS
Bouajaj, Ahmed; Bahi, Lahcen; Ouadif, Latifa; Awa, Mohamed
2016-10-01
An analysis of slope stability using Geographic Information System (GIS) is presented in this paper. The methodology is based on the calculation of the safety factor in 2D and 3D using ArcGis. Hovland's Method in 3D and 2D were used in the stability analysis of the slope located at the 34 kilometer point (K.P.34) on the highway in the North of Morocco connecting Tangier to Ksar Sghir. Results shows that the safety factors obtained in 3D are always higher than those obtained in 2D and the slope becomes unstable when the water table level is less than 1 m.
SLOPE STABILITY ANALYSIS USING GIS
A. Bouajaj
2016-10-01
Full Text Available An analysis of slope stability using Geographic Information System (GIS is presented in this paper. The methodology is based on the calculation of the safety factor in 2D and 3D using ArcGis. Hovland's Method in 3D and 2D were used in the stability analysis of the slope located at the 34 kilometer point (K.P.34 on the highway in the North of Morocco connecting Tangier to Ksar Sghir. Results shows that the safety factors obtained in 3D are always higher than those obtained in 2D and the slope becomes unstable when the water table level is less than 1 m.
Robust F0 Estimation Using ELS-Based Robust Complex Speech Analysis
Funaki, Keiichi; Kinjo, Tatsuhiko
Complex speech analysis for an analytic speech signal can accurately estimate the spectrum in low frequencies since the analytic signal provides spectrum only over positive frequencies. The remarkable feature makes it possible to realize more accurate F0 estimation using complex residual signal extracted by complex-valued speech analysis. We have already proposed F0 estimation using complex LPC residual, in which the autocorrelation function weighted by AMDF was adopted as the criterion. The method adopted MMSE-based complex LPC analysis and it has been reported that it can estimate more accurate F0 for IRS filtered speech corrupted by white Gauss noise although it can not work better for the IRS filtered speech corrupted by pink noise. In this paper, robust complex speech analysis based on ELS (Extended Least Square) method is introduced in order to overcome the drawback. The experimental results for additive white Gauss or pink noise demonstrate that the proposed algorithm based on robust ELS-based complex AR analysis can perform better than other methods.
Robustness Analysis of Real Network Topologies Under Multiple Failure Scenarios
Manzano, M.; Marzo, J. L.; Calle, E.
2012-01-01
on topological characteristics. Recently approaches also consider the services supported by such networks. In this paper we carry out a robustness analysis of five real backbone telecommunication networks under defined multiple failure scenarios, taking into account the consequences of the loss of established......Nowadays the ubiquity of telecommunication networks, which underpin and fulfill key aspects of modern day living, is taken for granted. Significant large-scale failures have occurred in the last years affecting telecommunication networks. Traditionally, network robustness analysis has been focused...
A Robust Method of Vehicle Stability Accurate Measurement Using GPS and INS
Miao Zhibin
2015-12-01
Full Text Available With the development of the vehicle industry, controlling stability has become more and more important. Techniques of evaluating vehicle stability are in high demand. Integration of Global Positioning System (GPS and Inertial Navigation System (INS is a very practical method to get high-precision measurement data. Usually, the Kalman filter is used to fuse the data from GPS and INS. In this paper, a robust method is used to measure vehicle sideslip angle and yaw rate, which are two important parameters for vehicle stability. First, a four-wheel vehicle dynamic model is introduced, based on sideslip angle and yaw rate. Second, a double level Kalman filter is established to fuse the data from Global Positioning System and Inertial Navigation System. Then, this method is simulated on a sample vehicle, using Carsim software to test the sideslip angle and yaw rate. Finally, a real experiment is made to verify the advantage of this approach. The experimental results showed the merits of this method of measurement and estimation, and the approach can meet the design requirements of the vehicle stability controller.
ZHU Xiao-cai; DONG Guo-hua; CAI Zi-xing; HU De-wen
2007-01-01
A robust unified controller was proposed for wheeled mobile robots that do not satisfy the ideal rolling without slipping constraint. Practical trajectory tracking and posture stabilization were achieved in a unified framework. The design procedure was based on the transverse function method and Lyapunov redesign technique. The Lie group was also introduced in the design. The left-invariance property of the nominal model was firstly explored with respect to the standard group operation of the Lie group SE(2). Then, a bounded transverse function was constructed, by which a corresponding smooth embedded submanifold was defined.With the aid of the group operation, a smooth control law was designed, which fulfills practical tracking/stabilization of the nominal system. An additional component was finally constructed to robustify the nominal control law with respect to the slipping disturbance by using the Lyapunov redesign technique. The design procedure can be easily extended to the robot system suffered from general unknown but bounded disturbances. Simulations were provided to demonstrate the effectiveness of the robust unified controller.
STRUCTURAL SYNTHESIS OF A STABILIZING ROBUST CONTROLLER OF THE ROTOR FLUX LINKAGE
N. J. Khlopenko
2017-03-01
Full Text Available Purpose. The aim is to structural synthesis of robust stabilizing control of the rotor flux vector control system of induction motor. Methodology. Synthesis controller structure was carried out in two stages. The first stage constructed a mathematical model of the channel of the rotor flux with parametric uncertainty and calculated transfer function of H∞-suboptimal controller by method of the mixed sensitivity. The second stage was carried out the expansion of the transfer function of the continued fraction for the Euclidean algorithm. This fraction was used to construct the controller structural scheme. Results. Computer modeling of the transfer function of H∞-suboptimal controller. Achieved decomposition found the transfer function of the continued fraction. The flow diagram of suboptimal H∞-controller with a proportional and integrating links and a few summers. The curves of transient rotor flux linkage in packages Robust Control Toolbox and Simulink. They coincide in the steady state, but differ among themselves in the transition. Originality. We developed the method of structural synthesis of robust stabilizing controller of the flux linkage rotor, H∞-suboptimal structural scheme of which is presented in the form of simple compounds integrating and proportional elements of the same order as the controller with the strictly correct transfer function, and takes into account the parametric uncertainty of control object. The results of the simulation of transient processes in a variety of packages MATLAB applications confirms the adequacy and small sensitivity of the system to parametric perturbation. Practical value. The resulting structure of the controller makes it possible to carry out the modernization of electric control systems, in use, with minimal financial costs.
Stability analysis of nonlinear systems
Lakshmikantham, Vangipuram; Martynyuk, Anatoly A
2015-01-01
The book investigates stability theory in terms of two different measure, exhibiting the advantage of employing families of Lyapunov functions and treats the theory of a variety of inequalities, clearly bringing out the underlying theme. It also demonstrates manifestations of the general Lyapunov method, showing how this technique can be adapted to various apparently diverse nonlinear problems. Furthermore it discusses the application of theoretical results to several different models chosen from real world phenomena, furnishing data that is particularly relevant for practitioners. Stability Analysis of Nonlinear Systems is an invaluable single-sourse reference for industrial and applied mathematicians, statisticians, engineers, researchers in the applied sciences, and graduate students studying differential equations.
Robust Frequency and Voltage Stability Control Strategy for Standalone AC/DC Hybrid Microgrid
Furqan Asghar
2017-05-01
Full Text Available The microgrid (MG concept is attracting considerable attention as a solution to energy deficiencies, especially in remote areas, but the intermittent nature of renewable sources and varying loads cause many control problems and thereby affect the quality of power within a microgrid operating in standalone mode. This might cause large frequency and voltage deviations in the system due to unpredictable output power fluctuations. Furthermore, without any main grid support, it is more complex to control and manage the system. In past, droop control and various other coordination control strategies have been presented to stabilize the microgrid frequency and voltages, but in order to utilize the available resources up to their maximum capacity in a positive way, new and robust control mechanisms are required. In this paper, a standalone microgrid is presented, which integrates renewable energy-based distributed generations and local loads. A fuzzy logic-based intelligent control technique is proposed to maintain the frequency and DC (direct current-link voltage stability for sudden changes in load or generation power. Also from a frequency control perspective, a battery energy storage system (BESS is suggested as a replacement for a synchronous generator to stabilize the nominal system frequency as a synchronous generator is unable to operate at its maximum efficiency while being controlled for stabilization purposes. Likewise, a super capacitor (SC and BESS is used to stabilize DC bus voltages even though maximum possible energy is being extracted from renewable generated sources using maximum power point tracking. This newly proposed control method proves to be effective by reducing transient time, minimizing the frequency deviations, maintaining voltages even though maximum power point tracking is working and preventing generators from exceeding their power ratings during disturbances. However, due to the BESS limited capacity, load switching
Statistical analysis of wines using a robust compositional biplot.
Hron, K; Jelínková, M; Filzmoser, P; Kreuziger, R; Bednář, P; Barták, P
2012-02-15
Eight phenolic acids (vanillic, gentisic, protocatechuic, syringic, gallic, coumaric, ferulic and caffeic) were quantitatively determined in 30 commercially available wines from South Moravia by gas chromatography-mass spectrometry. Raw (untransformed) and centered log-ratio transformed data were evaluated by classical and robust version of principal component analysis (PCA). A robust compositional biplot of the centered log-ratio transformed data gives the best resolution of particular categories of wines. Vanillic, syringic and gallic acids were identified as presumed markers occurring in relatively higher concentrations in red wines. Gentisic and caffeic acid were tentatively suggested as prospective technological markers, reflecting presumably some kinds of technological aspects of wine making.
Power System Stabilizer Design Based on Model Reference Robust Fuzzy Control
Mohammad Reza Yazdchi
2012-04-01
Full Text Available Power System Stabilizers (PSS are used to generate supplementary damping control signals for the excitation system in order to damp the Low Frequency Oscillations (LFO of the electric power system. The PSS is usually designed based on classical control approaches but this Conventional PSS (CPSS has some problems in power system control and stability enhancement. To overcome the drawbacks of CPSS, numerous techniques have been proposed in literatures. In this study a new method based on Model Reference Robust Fuzzy Control (MRRFC is considered to design PSS. In this new approach, in first an optimal PSS is designed in the nominal operating condition and then power system identification is used to obtain model reference of power system including optimal PSS. With changing system operating condition from the nominal condition, the error between obtained model reference and power system response in sent to a fuzzy controller and this fuzzy controller provides the stabilizing signal for damping power system oscillations just like PSS. In order to model reference identification a PID type PSS (PID-PSS is considered for damping electric power system oscillations. The parameters of this PID-PSS are tuned based on hybrid Genetic Algorithms (GA optimization method. The proposed MRRFC is evaluated against the CPSS at a single machine infinite bus power system considering system parametric uncertainties. The simulation results clearly indicate the effectiveness and validity of the proposed method.
Software Tools for Robust Analysis of High-Dimensional Data
Valentin Todorov
2014-06-01
Full Text Available The present work discusses robust multivariate methods specifically designed for highdimensions. Their implementation in R is presented and their application is illustratedon examples. The first group are algorithms for outlier detection, already introducedelsewhere and implemented in other packages. The value added of the new package isthat all methods follow the same design pattern and thus can use the same graphicaland diagnostic tools. The next topic covered is sparse principal components including anobject oriented interface to the standard method proposed by Zou, Hastie, and Tibshirani(2006 and the robust one proposed by Croux, Filzmoser, and Fritz (2013. Robust partialleast squares (see Hubert and Vanden Branden 2003 as well as partial least squares fordiscriminant analysis conclude the scope of the new package.
ROBUST STABILIZATION AND OPTIMIZATION OF FLIGHT CONTROL SYSTEM WITH STATE FEEDBACK AND FUZZY LOGICS
Marta M. Komnatska
2009-04-01
Full Text Available This paper deals with combination of two powerful and modern control tools as linear matrix inequality that is used for synthesis a ‘crisp’ controller and a fuzzy control approach for designing a soft controller. The control design consists of two stages. The first stage investigates the problem of a robust an controller design with parameters uncertainties of the handled plant in the presence of external disturbances. Stability conditions are obtained via a quadratic Lyapunov function and represented in the form of linear matrix inequalities. The second stage consists of the outer loop controller construction based on fuzzy inference system that utilizes for altitude hold mode. The parameters of the fuzzy controller are adjusted with a gradient descent method in order to improve the performance of the overall system. The case study illustrates the efficiency of the proposed approach to the flight control of small Unmanned Aerial Vehicle
Stochastic robustness and relative stability of multiple pathways in biological networks
Guo, Yongyi; Qian, Min; Ge, Hao
2015-01-01
Multiple dynamic pathways always exist in biological networks, but their robustness against internal fluctuations and relative stability have not been well recognized and carefully analyzed yet. Here we try to address these issues through an illustrative example, namely the Siah-1/beta-catenin/p14/19 ARF loop of protein p53 dynamics. Its deterministic Boolean network model predicts that two parallel pathways with comparable magnitudes of attractive basins should exist after the protein p53 is activated when a cell becomes harmfully disturbed. Once the low but non-neglectable intrinsic fluctuations are incorporated into the model, we show that a phase transition phenomenon is emerged: in one parameter region the probability weights of the normal pathway, reported in experimental literature, are comparable with the other pathway which is seemingly abnormal with the unknown functions, whereas, in some other parameter regions, the probability weight of the abnormal pathway can even dominate and become globally at...
Delay-dependent robust stability for neutral systems with mixed discrete-and-neutral delays
Yong HE; Min WU; Jinhua SHE
2004-01-01
This paper focuses on the problem of delay-dependent robust stability of neutral systems with different discrete-and-neutral delays and time-varying structured uncertainties.Some new criteria are presented,in which some free weighting matrices are used to express the relationships between the terms in the Leibniz-Newton formula.The criteria include the information on the size of both neutral-and-discrete delays.It is shown that the present results also include the results for identical discrete-and-neutral delays as special cases.A numerical example illustrates the improvement of the proposed methods over the previous methods and the influences between the discrete and neutral delays.
Rohlf, Thimo
2008-01-01
Genetic regulation is a key component in development, but a clear understanding of the structure and dynamics of genetic networks is not yet at hand. In this work we investigate these properties within an artificial genome model originally introduced by Reil. We analyze statistical properties of randomly generated genomes both on the sequence- and network level, and show that this model correctly predicts the frequency of genes in genomes as found in experimental data. Using an evolutionary algorithm based on stabilizing selection for a phenotype, we show that robustness against single base mutations, as well as against random changes in initial network states that mimic stochastic fluctuations in environmental conditions, can emerge in parallel. Evolved genomes exhibit characteristic patterns on both sequence and network level.
GRANDIN, P. H.
2014-06-01
Full Text Available Recommendation systems based on collaborative filtering are open by nature, what makes them vulnerable to profile injection attacks that insert biased evaluations in the system database in order to manipulate recommendations. In this paper we evaluate the stability and robustness of collaborative filtering algorithms applied to semantic web services recommendation when submitted to random and segment profile injection attacks. We evaluated four algorithms: (1 IMEAN, that makes predictions using the average of the evaluations received by the target item; (2 UMEAN, that makes predictions using the average of the evaluation made by the target user; (3 an algorithm based on the k-nearest neighbor (k-NN method and (4, an algorithm based on the k-means clustering method.The experiments showed that the UMEAN algorithm is not affected by the attacks and that IMEAN is the most vulnerable of all algorithms tested. Nevertheless, both UMEAN and IMEAN have little practical application due to the low precision of their predictions. Among the algorithms with intermediate tolerance to attacks but with good prediction performance, the algorithm based on k-nn proved to be more robust and stable than the algorithm based on k-means.
Mean flow stability analysis of oscillating jet experiments
Oberleithner, Kilian; Soria, Julio
2014-01-01
Linear stability analysis is applied to the mean flow of an oscillating round jet with the aim to investigate the robustness and accuracy of mean flow stability wave models. The jet's axisymmetric mode is excited at the nozzle lip through a sinusoidal modulation of the flow rate at amplitudes ranging from 0.1 % to 100 %. The instantaneous flow field is measured via particle image velocimetry and decomposed into a mean and periodic part utilizing proper orthogonal decomposition. Local linear stability analysis is applied to the measured mean flow adopting a weakly nonparallel flow approach. The resulting global perturbation field is carefully compared to the measurements in terms of spatial growth rate, phase velocity, and phase and amplitude distribution. It is shown that the stability wave model accurately predicts the excited flow oscillations during their entire growth phase and during a large part of their decay phase. The stability wave model applies over a wide range of forcing amplitudes, showing no pr...
A Comparative Study of Kernel and Robust Canonical Correlation Analysis
Ashad M. Alam
2010-02-01
Full Text Available A number of measures of canonical correlation coefficient are now used in multimedia related fields like object recognition, image segmentation facial expression recognition and pattern recognition in the different literature. Some robust forms of classical canonical correlation coefficient are introduced recently to address the robustness issue of the canonical coefficient in the presence of outliers and departure from normality. Also a few number of kernels are used in canonical analysis to capture nonlinear relationship in data space, which is linear in some higher dimensional feature space. But not much work has been done to investigate their relative performances through i simulation from the view point of sensitivity, breakdown analysis as well as ii using real data sets. In this paper an attempt has been made to compare performances of kernel canonical correlation coefficients (Gaussian function, Laplacian function and Polynomial function with that of robust and classical canonical correlation coefficient measures using simulation with five sample sizes (50, 500, 1000, 1500 and 2000, influence function, breakdown point along with several real data and a multi-modal data sets, focusing on the specific case of segmented images with associated text. We investigate the bias, mean square error(MISE, qualitative robustness index (RI, sensitivity curve of each estimator under a variety of situations and also employ box plots and scatter plots of canonical variates to judge their performances. We have observed that the class of kernel estimators perform better than the class of classical and robust estimators in general and the kernel estimator with Laplacian function has shown the best performance for large sample size and break down is high in case of nonlinear data.
Practical robust stabilization of PMAC servo drive based on continuous variable structure control
Grcar, B.; Cafuta, P.; Znidaric, M. [Univ. of Maribor (Slovenia). Faculty of Electrical Engineering and Computer Sciences
1996-12-01
In the paper the two stage control design of a high performance PMAC servo drive is described. In the first stage the nominal PMAC motor model is discussed as an analytical nonlinear system, transformed into the controllable canonical Brunovsky`s forms on the basis of input-output linearization. The influence of the load torque is considered implicitly by introducing the disturbance observer. Due to the sensitivity of the nominal model based control to parameter perturbations the linear tracking control is extended in the second stage by a continuous variable structure stabilizing control derived from Lyapunov`s function of the augmented feedback system. The design of the variable structure control requires no knowledge of the upper bounds of the perturbation function; instead, it considers the variable bounds of the available control signal. Undesired chattering of states and controlled variables are excluded. The introduced two stage control design assures practical robust stabilization for the class of bounded nonlinear perturbations satisfying the matching conditions without affecting the relative degree of the feedback system. Experimental results of the proposed PMAC servo drive control are presented.
Robust decentralized PID-based power system stabilizer design using an ILMI approach
Soliman, M.; Bendary, F.; Mansour, W. [Electrical Power and Machines Dept., Faculty of Engineering, Benha university, 108 Shoubra St., Cairo (Egypt); Elshafei, A.L. [Electrical Power and Machines Dept., Cairo University, Gamma St, Giza (Egypt)
2010-12-15
Thanks to its essential functionality and structure simplicity, proportional-integral-derivative (PID) controllers are commonly used by industrial utilities. A robust PID-based power system stabilizer (PSS) is proposed to properly function over a wide range of operating conditions. Uncertainties in plant parameters, due to variation in generation and load patterns, are expressed in the form of a polytopic model. The PID control problem is firstly reduced to a generalized static output feedback (SOF) synthesis. The derivative action is designed and implemented as a high-pass filter based on a low-pass block to reduce its sensitivity to sensor noise. The proposed design algorithm adopts a quadratic Lyapunov approach to guarantee {alpha}-decay rate for the entire polytope. A constrained structure of Lyapunov function and SOF gain matrix is considered to enforce a decentralized scheme. Setting of controller parameters is carried out via an iterative linear matrix inequality (ILMI). Simulation results, based on a benchmark model of a two-area four-machine test system, are presented to compare the proposed design to a well-tuned conventional PSS and to the standard IEEE-PSS4B stabilizer. (author)
Nguyen, Quan M.; Peleg, Avner; Tran, Thinh P.
2015-01-01
We develop a method for transmission stabilization and robust dynamic switching for colliding optical soliton sequences in broadband waveguide systems with nonlinear gain and loss. The method is based on employing hybrid waveguides, consisting of spans with linear gain and cubic loss, and spans with linear loss, cubic gain, and quintic loss. We show that the amplitude dynamics is described by a hybrid Lotka-Volterra (LV) model, and use the model to determine the physical parameter values required for enhanced transmission stabilization and switching. Numerical simulations with coupled nonlinear Schrödinger equations confirm the predictions of the LV model, and show complete suppression of radiative instability and pulse distortion. This enables stable transmission over distances larger by an order of magnitude compared with uniform waveguides with linear gain and cubic loss. Moreover, multiple on-off and off-on dynamic switching events are demonstrated over a wide range of soliton amplitudes, showing the superiority of hybrid waveguides compared with static switching in uniform waveguides.
Design of a H∞ Robust Controller with μ-Analysis for Steam Turbine Power Generation Applications
Vincenzo Iannino
2017-07-01
Full Text Available Concentrated Solar Power plants are complex systems subjected to quite sensitive variations of the steam production profile and external disturbances, thus advanced control techniques that ensure system stability and suitable performance criteria are required. In this work, a multi-objective H∞ robust controller is designed and applied to the power control of a Concentered Solar Power plant composed by two turbines, a gear and a generator. In order to provide robust performance and stability in presence of disturbances, not modeled plant dynamics and plant-parameter variations, the advanced features of the μ-analysis are exploited. A high order controller is obtained from the process of synthesis that makes the implementation of the controller difficult and computational more demanding for a Programmable Logic Controller. Therefore, the controller order is reduced through the Balanced Truncation method and then discretized. The obtained robust control is compared to the current Proportional Integral Derivative-based governing system in order to evaluate its performance, considering unperturbed as well as perturbed scenarios, taking into account variations of steam conditions, sensor measurement delays and power losses. The simulations results show that the proposed controller achieves better robustness and performance compared to the existing Proportional Integral Derivative controller.
Comparative Analysis for Robust Penalized Spline Smoothing Methods
Bin Wang
2014-01-01
Full Text Available Smoothing noisy data is commonly encountered in engineering domain, and currently robust penalized regression spline models are perceived to be the most promising methods for coping with this issue, due to their flexibilities in capturing the nonlinear trends in the data and effectively alleviating the disturbance from the outliers. Against such a background, this paper conducts a thoroughly comparative analysis of two popular robust smoothing techniques, the M-type estimator and S-estimation for penalized regression splines, both of which are reelaborated starting from their origins, with their derivation process reformulated and the corresponding algorithms reorganized under a unified framework. Performances of these two estimators are thoroughly evaluated from the aspects of fitting accuracy, robustness, and execution time upon the MATLAB platform. Elaborately comparative experiments demonstrate that robust penalized spline smoothing methods possess the capability of resistance to the noise effect compared with the nonrobust penalized LS spline regression method. Furthermore, the M-estimator exerts stable performance only for the observations with moderate perturbation error, whereas the S-estimator behaves fairly well even for heavily contaminated observations, but consuming more execution time. These findings can be served as guidance to the selection of appropriate approach for smoothing the noisy data.
Stability Analysis of Ecomorphodynamic Equations
Bärenbold, Fabian; Perona, Paolo
2014-01-01
Although riparian vegetation is present in or along many water courses of the world, its active role resulting from the interaction with flow and sediment processes has only recently become an active field of research. Especially, the role of vegetation in the process of river pattern formation has been explored and demonstrated mostly experimentally and numerically until now. In the present work, we shed light on this subject by performing a linear stability analysis on a simple model for riverbed vegetation dynamics coupled with the set of classical river morphodynamic equations. The vegetation model only accounts for logistic growth, local positive feedback through seeding and resprouting, and mortality by means of uprooting through flow shear stress. Due to the simplicity of the model, we can transform the set of equations into an eigenvalue problem and assess the stability of the linearized equations when slightly perturbated away from a spatially homogeneous solution. If we couple vegetation dynamics wi...
Robust Linear Models for Cis-eQTL Analysis.
Mattias Rantalainen
Full Text Available Expression Quantitative Trait Loci (eQTL analysis enables characterisation of functional genetic variation influencing expression levels of individual genes. In outbread populations, including humans, eQTLs are commonly analysed using the conventional linear model, adjusting for relevant covariates, assuming an allelic dosage model and a Gaussian error term. However, gene expression data generally have noise that induces heavy-tailed errors relative to the Gaussian distribution and often include atypical observations, or outliers. Such departures from modelling assumptions can lead to an increased rate of type II errors (false negatives, and to some extent also type I errors (false positives. Careful model checking can reduce the risk of type-I errors but often not type II errors, since it is generally too time-consuming to carefully check all models with a non-significant effect in large-scale and genome-wide studies. Here we propose the application of a robust linear model for eQTL analysis to reduce adverse effects of deviations from the assumption of Gaussian residuals. We present results from a simulation study as well as results from the analysis of real eQTL data sets. Our findings suggest that in many situations robust models have the potential to provide more reliable eQTL results compared to conventional linear models, particularly in respect to reducing type II errors due to non-Gaussian noise. Post-genomic data, such as that generated in genome-wide eQTL studies, are often noisy and frequently contain atypical observations. Robust statistical models have the potential to provide more reliable results and increased statistical power under non-Gaussian conditions. The results presented here suggest that robust models should be considered routinely alongside other commonly used methodologies for eQTL analysis.
Power system small signal stability analysis and control
Mondal, Debasish; Sengupta, Aparajita
2014-01-01
Power System Small Signal Stability Analysis and Control presents a detailed analysis of the problem of severe outages due to the sustained growth of small signal oscillations in modern interconnected power systems. The ever-expanding nature of power systems and the rapid upgrade to smart grid technologies call for the implementation of robust and optimal controls. Power systems that are forced to operate close to their stability limit have resulted in the use of control devices by utility companies to improve the performance of the transmission system against commonly occurring power system
Gayvoronskiy, S. A.; Ezangina, T.; Khozhaev, I.; Gunbo, Lan
2017-01-01
The authors of this article developed the technique of combined parametric synthesis of a linear controller on the basis of the coefficient method and the method of mathematical programming capable of ensuring the maximization of the degree of robust stability of a control system. The article also presents the numerical illustration of the PI controller synthesis of the position stabilization system of an underwater object.
Performance Analysis of Intelligent Robust Facility Layout Design
Moslemipour, G.; Lee, T. S.; Loong, Y. T.
2017-03-01
Design of a robust production facility layout with minimum handling cost (MHC) presents an appropriate approach to tackle facility layout problems in a dynamic volatile environment, in which product demands randomly change in each planning period. The objective of the design is to find the robust facility layout with minimum total material handling cost over the entire multi-period planning horizon. This paper proposes a new mathematical model for designing robust machine layout in the stochastic dynamic environment of manufacturing systems using quadratic assignment problem (QAP) formulation. In this investigation, product demands are assumed to be normally distributed random variables with known expected value, variance, and covariance that randomly change from period to period. The proposed model was verified and validated using randomly generated numerical data and benchmark examples. The effect of dependent product demands and varying interest rate on the total cost function of the proposed model has also been investigated. Sensitivity analysis on the proposed model has been performed. Dynamic programming and simulated annealing optimization algorithms were used in solving the modeled example problems.
Performance Analysis of Intelligent Robust Facility Layout Design
Moslemipour, G.; Lee, T. S.; Loong, Y. T.
2017-03-01
Design of a robust production facility layout with minimum handling cost (MHC) presents an appropriate approach to tackle facility layout problems in a dynamic volatile environment, in which product demands randomly change in each planning period. The objective of the design is to find the robust facility layout with minimum total material handling cost over the entire multi-period planning horizon. This paper proposes a new mathematical model for designing robust machine layout in the stochastic dynamic environment of manufacturing systems using quadratic assignment problem (QAP) formulation. In this investigation, product demands are assumed to be normally distributed random variables with known expected value, variance, and covariance that randomly change from period to period. The proposed model was verified and validated using randomly generated numerical data and benchmark examples. The effect of dependent product demands and varying interest rate on the total cost function of the proposed model has also been investigated. Sensitivity analysis on the proposed model has been performed. Dynamic programming and simulated annealing optimization algorithms were used in solving the modeled example problems.
M. Ramírez
2015-04-01
Full Text Available In this paper, the effect of fuzzy logic-based robust power system stabilizers on the improvement of the dynamics of a large-scale power system is investigated. The study is particularly focused on the Mexican Interconnected System and on adding damping to two critical inter-area system oscillation modes: the north-south mode and the western-peninsular mode. The fuzzy power system stabilizers (FPSSs applied here are based on a significantly reduced rule base, small number of tuning parameters, and simple control algorithm and architecture, which makes their design and implementation easier and suitable for practical applications. Non-linear time-domain simulations for a set of test cases and results from Prony Analysis verify the robustness of the designed FPSSs, as compared to conventional PSSs.
Application of Bounded Linear Stability Analysis Method for Metrics-Driven Adaptive Control
Bakhtiari-Nejad, Maryam; Nguyen, Nhan T.; Krishnakumar, Kalmanje
2009-01-01
This paper presents the application of Bounded Linear Stability Analysis (BLSA) method for metrics-driven adaptive control. The bounded linear stability analysis method is used for analyzing stability of adaptive control models, without linearizing the adaptive laws. Metrics-driven adaptive control introduces a notion that adaptation should be driven by some stability metrics to achieve robustness. By the application of bounded linear stability analysis method the adaptive gain is adjusted during the adaptation in order to meet certain phase margin requirements. Analysis of metrics-driven adaptive control is evaluated for a second order system that represents a pitch attitude control of a generic transport aircraft. The analysis shows that the system with the metrics-conforming variable adaptive gain becomes more robust to unmodeled dynamics or time delay. The effect of analysis time-window for BLSA is also evaluated in order to meet the stability margin criteria.
Stability Analysis of MEMS Gyroscope Dynamic Systems
M. Naser-Moghadasi; S. A. Olamaei; F. Setoudeh
2013-01-01
In this paper, the existence of a common quadratic Lyapunov function for stability analysis of MEMS Gyroscope dynamic systems has been studied then a new method based on stochastic stability of MEMS Gyroscope system has been proposed.
ANALYSIS OF MOTORCAR COURSE-KEEPING STABILITY
Makarov, V.
2012-06-01
Full Text Available The generalized scheme and graph-model with factors influencing the motorcar course-keeping stability are suggested. The analysis of possible variants improving the motorcar course-keeping stability is presented in the graph-model.
Zhang Yougang; Xu Bugong
2006-01-01
Decentralized robust stabilization problem of discrete-time fuzzy large-scale systems with parametric uncertainties is considered. This uncertain fuzzy large-scale system consists of N interconnected T-S fuzzy subsystems, and the parametric uncertainties are unknown but norm-bounded. Based on Lyapunov stability theory and decentralized control theory of large-scale system, the design schema of decentralized parallel distributed compensation (DPDC) fuzzy controllers to ensure the asymptotic stability of the whole fuzzy large-scale system is proposed. The existence conditions for these controllers take the forms of LMIs. Finally a numerical simulation example is given to show the utility of the method proposed.
Liu, Yuzhi; Li, Muguo
2015-05-01
This paper investigates the robust stabilization problem for uncertain linear systems with interval time-varying delays. By constructing novel Lyapunov-Krasovskii functionals and developing delay-partitioning approaches, some delay-dependent stability criteria are derived based on an improved Wirtinger׳s inequality and the reciprocally convex method. The proposed methods have improved the stability conditions without increasing much computational complexity. A state feedback controller design approach is also presented based on the proposed criteria. Numerical examples are finally given to illustrate the effectiveness of the proposed method.
Weihua Mao
2012-01-01
Full Text Available This paper discusses the mean-square exponential stability of uncertain neutral linear stochastic systems with interval time-varying delays. A new augmented Lyapunov-Krasovskii functional (LKF has been constructed to derive improved delay-dependent robust mean-square exponential stability criteria, which are forms of linear matrix inequalities (LMIs. By free-weight matrices method, the usual restriction that the stability conditions only bear slow-varying derivative of the delay is removed. Finally, numerical examples are provided to illustrate the effectiveness of the proposed method.
Analysis and design of robust decentralized controllers for nonlinear systems
Schoenwald, D.A.
1993-07-01
Decentralized control strategies for nonlinear systems are achieved via feedback linearization techniques. New results on optimization and parameter robustness of non-linear systems are also developed. In addition, parametric uncertainty in large-scale systems is handled by sensitivity analysis and optimal control methods in a completely decentralized framework. This idea is applied to alleviate uncertainty in friction parameters for the gimbal joints on Space Station Freedom. As an example of decentralized nonlinear control, singular perturbation methods and distributed vibration damping are merged into a control strategy for a two-link flexible manipulator.
Yang Fang
2016-01-01
Full Text Available The robust exponential stability problem for a class of uncertain impulsive stochastic neural networks of neutral-type with Markovian parameters and mixed time-varying delays is investigated. By constructing a proper exponential-type Lyapunov-Krasovskii functional and employing Jensen integral inequality, free-weight matrix method, some novel delay-dependent stability criteria that ensure the robust exponential stability in mean square of the trivial solution of the considered networks are established in the form of linear matrix inequalities (LMIs. The proposed results do not require the derivatives of discrete and distributed time-varying delays to be 0 or smaller than 1. Moreover, the main contribution of the proposed approach compared with related methods lies in the use of three types of impulses. Finally, two numerical examples are worked out to verify the effectiveness and less conservativeness of our theoretical results over existing literature.
Delay-dependent robust stabilization for a class of neutral systems with nonlinear perturbations
无
2007-01-01
This note deals with the problem of stabilization/stability for neutral systems with nonlinear perturbations.A new stabilization/stability scheme is presented.Using improved Lyapunov functionals.less conservative stabilization/stability conditions are derived for such systems based on linear matrix inequalities(LMI).Numerical examples are provided to show that the proposed results significantly improve the allowed upper bounds of the delay size over some existing ones in the literature.
The analysis of image feature robustness using cometcloud
Xin Qi
2012-01-01
Full Text Available The robustness of image features is a very important consideration in quantitative image analysis. The objective of this paper is to investigate the robustness of a range of image texture features using hematoxylin stained breast tissue microarray slides which are assessed while simulating different imaging challenges including out of focus, changes in magnification and variations in illumination, noise, compression, distortion, and rotation. We employed five texture analysis methods and tested them while introducing all of the challenges listed above. The texture features that were evaluated include co-occurrence matrix, center-symmetric auto-correlation, texture feature coding method, local binary pattern, and texton. Due to the independence of each transformation and texture descriptor, a network structured combination was proposed and deployed on the Rutgers private cloud. The experiments utilized 20 randomly selected tissue microarray cores. All the combinations of the image transformations and deformations are calculated, and the whole feature extraction procedure was completed in 70 minutes using a cloud equipped with 20 nodes. Center-symmetric auto-correlation outperforms all the other four texture descriptors but also requires the longest computational time. It is roughly 10 times slower than local binary pattern and texton. From a speed perspective, both the local binary pattern and texton features provided excellent performance for classification and content-based image retrieval.
Stability Analysis of ISS Medications
Wotring, V. E.
2014-01-01
the United States Pharmacopeia (USP) to measure the amount of intact active ingredient, identify degradation products and measure their amounts. Some analyses were conducted by an independent analytical laboratory, but certain (Schedule) medications could not be shipped to their facility and were analyzed at JSC. RESULTS Nine medications were analyzed with respect to active pharmaceutical ingredient (API) and degradant amounts. Results were compared to the USP requirements for API and degradants/impurities content for every FDA-approved medication. One medication met USP requirements at 5 months after its expiration date. Four of the nine (44% of those tested) medications tested met USP requirements up to 8 months post-expiration. Another 3 medications (33% of those tested) met USP guidelines 2-3 months before expiration. One medication, a compound classed by the FDA as a dietary supplement and sometimes used as a sleep aid, failed to meet USP requirements at 11 months post-expiration. CONCLUSION Analysis of each medication at a single time point provides limited information on the stability of a medication stored in particular conditions; it is not possible to predict how long a medication may be safe and effective from these data. Notwithstanding, five of the nine medications tested (56%) met USP requirements for API and degradants/impurities at least 5 months past expiration dates. The single compound that failed to meet USP requirements is not regulated as strictly as prescription medications are during manufacture; it is unknown if this medication would have met the requirements prior to flight. Notably, it was the furthest beyond its expiration date. Only more comprehensive analysis of flight-aged samples compared to appropriate ground controls will permit determination of spaceflight effects on medication stability.
Kaibo Shi
2014-01-01
Full Text Available This paper is concerned with the problem of delay-dependent robust stability analysis for a class of uncertain neutral type Lur’e systems with mixed time-varying delays. The system has not only time-varying uncertainties and sector-bounded nonlinearity, but also discrete and distributed delays, which has never been discussed in the previous literature. Firstly, by employing one effective mathematical technique, some less conservative delay-dependent stability results are established without employing the bounding technique and the mode transformation approach. Secondly, by constructing an appropriate new type of Lyapunov-Krasovskii functional with triple terms, improved delay-dependent stability criteria in terms of linear matrix inequalities (LMIs derived in this paper are much brief and valid. Furthermore, both nonlinearities located in finite sector and infinite one have been also fully taken into account. Finally, three numerical examples are presented to illustrate lesser conservatism and the advantage of the proposed main results.
Qualitative and quantitative stability analysis of penta-rhythmic circuits
Schwabedal, Justus T. C.; Knapper, Drake E.; Shilnikov, Andrey L.
2016-12-01
Inhibitory circuits of relaxation oscillators are often-used models for dynamics of biological networks. We present a qualitative and quantitative stability analysis of such a circuit constituted by three generic oscillators (of a Fitzhugh-Nagumo type) as its nodes coupled reciprocally. Depending on inhibitory strengths, and parameters of individual oscillators, the circuit exhibits polyrhythmicity of up to five simultaneously stable rhythms. With methods of bifurcation analysis and phase reduction, we investigate qualitative changes in stability of these circuit rhythms for a wide range of parameters. Furthermore, we quantify robustness of the rhythms maintained under random perturbations by monitoring phase diffusion in the circuit. Our findings allow us to describe how circuit dynamics relate to dynamics of individual nodes. We also find that quantitative and qualitative stability properties of polyrhythmicity do not always align.
An Efficient and Configurable Preprocessing Algorithm to Improve Stability Analysis.
Sesia, Ilaria; Cantoni, Elena; Cernigliaro, Alice; Signorile, Giovanna; Fantino, Gianluca; Tavella, Patrizia
2016-04-01
The Allan variance (AVAR) is widely used to measure the stability of experimental time series. Specifically, AVAR is commonly used in space applications such as monitoring the clocks of the global navigation satellite systems (GNSSs). In these applications, the experimental data present some peculiar aspects which are not generally encountered when the measurements are carried out in a laboratory. Space clocks' data can in fact present outliers, jumps, and missing values, which corrupt the clock characterization. Therefore, an efficient preprocessing is fundamental to ensure a proper data analysis and improve the stability estimation performed with the AVAR or other similar variances. In this work, we propose a preprocessing algorithm and its implementation in a robust software code (in MATLAB language) able to deal with time series of experimental data affected by nonstationarities and missing data; our method is properly detecting and removing anomalous behaviors, hence making the subsequent stability analysis more reliable.
Deep and Structured Robust Information Theoretic Learning for Image Analysis.
Deng, Yue; Bao, Feng; Deng, Xuesong; Wang, Ruiping; Kong, Youyong; Dai, Qionghai
2016-07-07
This paper presents a robust information theoretic (RIT) model to reduce the uncertainties, i.e. missing and noisy labels, in general discriminative data representation tasks. The fundamental pursuit of our model is to simultaneously learn a transformation function and a discriminative classifier that maximize the mutual information of data and their labels in the latent space. In this general paradigm, we respectively discuss three types of the RIT implementations with linear subspace embedding, deep transformation and structured sparse learning. In practice, the RIT and deep RIT are exploited to solve the image categorization task whose performances will be verified on various benchmark datasets. The structured sparse RIT is further applied to a medical image analysis task for brain MRI segmentation that allows group-level feature selections on the brain tissues.
Jin, Q B; Liu, Q; Huang, B
2016-03-01
This paper considers the problem of determining all the robust PID (proportional-integral-derivative) controllers in terms of the gain and phase margins (GPM) for open-loop unstable first order plus time delay (UFOPTD) processes. It is the first time that the feasible ranges of the GPM specifications provided by a PID controller are given for UFOPTD processes. A gain and phase margin tester is used to modify the original model, and the ranges of the margin specifications are derived such that the modified model can be stabilized by a stabilizing PID controller based on Hermite-Biehlers Theorem. Furthermore, we obtain all the controllers satisfying a given margin specification. Simulation studies show how to use the results to design a robust PID controller.
Renji Han; Wei Jiang
2009-01-01
The problem of delay-dependent robust stability for uncertain linear singular neu-tral systems with time-varying and distributed delays is investigated. The uncertain-ties under consideration are norm bounded, and possibly time varying. Some new stability criteria, which are simpler and less conservative than existing results, are derived based on a new class of Lyapunov-Krasovskii functionals combined with the descriptor model transformation and the decomposition technique of coefficient matrix and formulated in the form of a linear matrix inequalitys (LMIs). Also, the criteria can be easily checked by the Matlab LMI toolbox.
Robustness analysis of pull strategies in multi-product systems
Chukwunonyelum Emmanuel Onyeocha
2015-09-01
Full Text Available Purpose: This paper examines the behaviour of shared and dedicated Kanban allocation policies of Hybrid Kanban-CONWIP and Basestock-Kanban-CONWIP control strategies in multi-product systems; with considerations to robustness of optimal solutions to environmental and system variabilities. Design/methodology/approach: Discrete event simulation and evolutionary multi-objective optimisation approach were utilised to develop Pareto-frontier or sets of non-dominated optimal solutions and for selection of an appropriate decision set for the control parameters in the shared Kanban allocation policy (S-KAP and dedicated Kanban allocation policy (D-KAP. Simulation experiments were carried out via ExtendSim simulation application software. The outcomes of PCS+KAP performances were compared via all pairwise comparison and Nelson’s screening and selection procedure for superior PCS+KAP under negligible environmental and system stability. To determine superior PCS+KAP under systems’ and environmental variability, the optimal solutions were tested for robustness using Latin hypercube sampling technique and stochastic dominance test. Findings: The outcome of this study shows that under uncontrollable environmental variability, dedicated Kanban allocation policy outperformed shared Kanban allocation policy in serial manufacturing system with negligible and in complex assembly line with setup times. Moreover, the BK-CONWIP is shown as superior strategy to HK-CONWIP. Research limitations/implications: Future research should be conducted to verify the level of flexibility of BK-CONWIP with respect to product mix and product demand volume variations in a complex multi-product system Practical implications: The outcomes of this work are applicable to multi-product manufacturing industries with significant setup times and systems with negligible setup times. The multi-objective optimisation provides decision support for selection of control-parameters such that
Fei Song; Shiyin Qin
2014-01-01
This paper proposed a robust fault-tolerant control algorithm for satellite stabilization based on active disturbance rejection approach with artificial bee colony algorithm. The actuating mechanism of attitude control system consists of three working reaction flywheels and one spare reaction flywheel. The speed measurement of reaction flywheel is adopted for fault detection. If any reaction flywheel fault is detected, the corresponding fault flywheel is isolated and the spare reaction flywhe...
Yi-You Hou; Zhang-Lin Wan
2014-01-01
This paper considers the problem of the robust stability for the nonlinear system with time-varying delay and parameters uncertainties. Based on the H∞ theorem, Lyapunov-Krasovskii theory, and linear matrix inequality (LMI) optimization technique, the H∞ quasi-sliding mode controller and switching function are developed such that the nonlinear system is asymptotically stable in the quasi-sliding mode and satisfies the disturbance attenuation (H∞-norm performance). The effectiveness and accura...
Sign Stability via Root Locus Analysis
Gibson, Travis E
2015-01-01
With the rise of network science old topics in ecology and economics are resurfacing. One such topic is structural stability (often referred to as qualitative stability or sign stability). A system is deemed structurally stable if the system remains stable for all possible parameter variations so long as the parameters do not change sign. This type of stability analysis is appealing when studying real systems as the underlying stability result only requires the scientist or engineer to know the sign of the parameters in the model and not the specific values. The necessary and sufficient conditions for qualitative stability however are opaque. In order to shed light on those conditions root locus analysis is employed. This technique allows us to illustrate the necessary conditions for qualitative stability.
The Variation and Stability Analysis of Wheat Dough Stability Time
TIAN Ji-chun; HU Rui-bo; DENG Zhi-ying; WANG Yan-xun
2007-01-01
Farinograph dough stability time is an important index for classifying wheat, and it often indicates the most appropriate end use for the wheat cultivars. This study aimed at the problem of large fluctuations in dough stability time that occurs during the commercial wheat production. The variations in the dough stability time and its consistency across locations and years were analyzed using 12 principal high-quality wheat cultivars (varieties) obtained from Shandong Province,China, which were grown at nine different locations for three successive years. The results showed that the coefficient of variation for the dough stability time ranged from 24.29 to 49.60% across different varieties, locations, and years. Additive main effects and multiplicative interaction (AMMI) analysis indicated that there were significant interactions for the dough stability time between the varieties, the growth locations, and the years. The genotype effect was the most noticeable, followed by the interaction of the genotype and the environment. The environmental effect was the least significant. The interactions between the varieties and the locations differ considerably, however, each cultivar (variety) apparently has a specific adaptability to the growth location. Therefore, for the successful commercial scale production of the high-quality wheat varieties, both the selection of proper cultivars and its most suitable growth locations to meet the desired requirements for the dough mixing stability time are important.
Reliability and Robustness Analysis of the Masinga Dam under Uncertainty
Hayden Postle-Floyd
2017-02-01
Full Text Available Kenya’s water abstraction must meet the projected growth in municipal and irrigation demand by the end of 2030 in order to achieve the country’s industrial and economic development plan. The Masinga dam, on the Tana River, is the key to meeting this goal to satisfy the growing demands whilst also continuing to provide hydroelectric power generation. This study quantitatively assesses the reliability and robustness of the Masinga dam system under uncertain future supply and demand using probabilistic climate and population projections, and examines how long-term planning may improve the longevity of the dam. River flow and demand projections are used alongside each other as inputs to the dam system simulation model linked to an optimisation engine to maximise water availability. Water availability after demand satisfaction is assessed for future years, and the projected reliability of the system is calculated for selected years. The analysis shows that maximising power generation on a short-term year-by-year basis achieves 80%, 50% and 1% reliability by 2020, 2025 and 2030 onwards, respectively. Longer term optimal planning, however, has increased system reliability to up to 95% in 2020, 80% in 2025, and more than 40% in 2030 onwards. In addition, increasing the capacity of the reservoir by around 25% can significantly improve the robustness of the system for all future time periods. This study provides a platform for analysing the implication of different planning and management of Masinga dam and suggests that careful consideration should be given to account for growing municipal needs and irrigation schemes in both the immediate and the associated Tana River basin.
Wholesale energy market in a smart grid. Dynamic modeling, stability, and robustness
Kiani Bejestani, Arman
2013-01-24
The recent paradigm shift in the architecture of the smart grid is driven by the need to integrate Renewable Energy Resources (RER), the availability of information through communication networks, and an emerging policy of demand that is intertwined with pricing. A major component of this architecture is the design of electricity markets, which pertains to the optimal scheduling of power generation and reserve requirements. The challenge is to carry out this scheduling with a high level of integration of renewable generation sources, a formidable task due to intermittency and uncertainty. Introducing huge intermittency and uncertainty in the smart grid will demand a dynamic framework for addressing the operation, scheduling and financial settlements in the uncertain environment. The temporal components in scheduling generation are necessary due to increasing penetration of renewable sources, and increasing potential of adjustable demand via Demand Response (DR). The former brings issues of strong intermittency and uncertainty, and the latter brings a feedback structure, where demand can be modulated over a range of time-scales. Both of these components are dictating a new look at market mechanisms, with a controls viewpoint enabling a novel framework for analysis and synthesis. This dissertation provides static and dynamic models that capture the various aspects of electrical power systems, including the dynamics of market participants, the physical and technical constraints of power systems, and the uncertainty of RER. The proposed models shed new light on wholesale electricity market design, allowing an understanding to be gained of how to create markets, which enhance the stability of price profiles, and efficiency of the power systems, in the presence of uncertain demand and intermittent resources. The notion of market equilibrium in the presence of RER and DR is presented. The effects of uncertainties due to forecast errors in RER and variations due to DR on
Stability Analysis of Path-vector Routing
Dimitri, Papadimitriou
2012-01-01
Most studies on path-vector routing stability have been conducted empirically by means of ad-hoc analysis of BGP data traces. None of them consider prior specification of an analytic method including the use of stability measurement metrics for the systematic analysis of BGP traces and associated meta-processing for determining the local state of the routing system. In this paper, we define a set of metrics that characterize the local stability properties of path-vector routing such as BGP (Border Gateway Protocol). By means of these stability metrics, we propose a method to analyze the effects of BGP policy- and protocol-induced instability on local routers.
Analysis of Path-vector Routing Stability
Dimitri, Papadimitriou
2012-01-01
Most studies on path-vector routing stability have been conducted empirically by means of ad-hoc analysis of BGP data traces. None of them consider prior specification of an analytic method including the use of stability measurement metrics for the systematic analysis of BGP traces and associated meta-processing for determining the local state of the routing system. In this paper, we define a set of metrics that characterize the local stability properties of path-vector routing such as BGP (Border Gateway Protocol). By means of these stability metrics, we propose a method to analyze the effects of BGP policy- and protocol-induced instability on local routers.
Robust Algorithm Development for Application of Pinch Analysis on HEN
Ritesh Sojitra
2016-10-01
Full Text Available Since its genesis, Pinch Analysis is continuously evolving and its application is widening, reaching new horizons. The original concept of pinch approach was quite clear and, because of flexibility of this approach, innumerable applications have been developed in the industry. Consequently, a designer gets thoroughly muddled among these flexibilities. Hence, there was a need for a rigorous and robust model which could guide the optimisation engineer on deciding the applicability of the pinch approach and direct sequential step of procedure in predefined workflow, so that the precision of approach is ensured. Exploring the various options of a novice hands-on algorithm development that can be coded and interfaced with GUI and keeping in mind the difficulties faced by designers, an effort was made to formulate a new algorithm for the optimisation activity. As such, the work aims at easing out application hurdles and providing hands-on information to the Developer for use during preparation of new application tools. This paper presents a new algorithm, the application which ensures the Developer does not violate basic pinch rules. To achieve this, intermittent check gates are provided in the algorithm, which eliminate violation of predefined basic pinch rules, design philosophy, and Engineering Standards and ensure that constraints are adequately considered. On the other side, its sequential instruction to develop the pinch analysis and reiteration promises Maximum Energy Recovery (MER.
Stability and Sensitivity Analysis of Fuzzy Control Systems. Mechatronics Applications
Radu-Emil Precup
2006-01-01
Full Text Available The development of fuzzy control systems is usually performed by heuristicmeans, incorporating human skills, the drawback being in the lack of general-purposedevelopment methods. A major problem, which follows from this development, is theanalysis of the structural properties of the control system, such as stability, controllabilityand robustness. Here comes the first goal of the paper, to present a stability analysismethod dedicated to fuzzy control systems with mechatronics applications based on the useof Popov’s hyperstability theory. The second goal of this paper is to perform the sensitivityanalysis of fuzzy control systems with respect to the parametric variations of the controlledplant for a class of servo-systems used in mechatronics applications based on theconstruction of sensitivity models. The stability and sensitivity analysis methods provideuseful information to the development of fuzzy control systems. The case studies concerningfuzzy controlled servo-systems, accompanied by digital simulation results and real-timeexperimental results, validate the presented methods.
A robust stabilization methodology for time domain integral equations in electromagnetics
Pray, Andrew J.
Time domain integral equations (TDIEs) are an attractive framework from which to analyze electromagnetic scattering problems. Casting problems in the time domain enables study of systems with nonlinearities, characterization of transient behavior both at the early and late time, and broadband analysis within a single simulation. Integral equation frameworks have the advantages of restricting the computational domain to the scatterer surface (boundary integral equations) or volume (volume integral equations), implicitly satisfying the radiation boundary condition, and being free of numerical dispersion error. Despite these advantages, TDIE solvers are not widely used by computational practitioners; principally because TDIE solutions are susceptible to late-time instability. While a plethora of stabilization schemes have been developed, particularly since the early 1980s, most of these schemes either do not guarantee stability, are difficult to implement, or are impractical for certain problems. The most promising methods seem to be the space-time Galerkin schemes. These are very challenging to implement as they require the accurate evaluation of 4-dimensional spatial integrals. The most successful recent approach to implementing these schemes has been to approximate a subset of these integrals, and evaluate the remaining integrals analytically. This approach describes the quasi-exact integration methods [Shanker et al. IEEE TAP 2009, Shi et al. IEEE TAP 2011]. The method of [Shanker et al. IEEE TAP 2009] approximates 2 of the 4 dimensions using numerical quadrature. The remaining integrals are evaluated analytically by determining shadow boundaries on the domain of integration. In [Shi et al. IEEE TAP 2011], only 1 dimension is approximated, but the procedure also relies on analytical integration between shadow boundaries. These two characteristics-the need to find shadow boundaries and develop analytical integration rules-prevent these methods from being extended
Scalable Robust Principal Component Analysis Using Grassmann Averages
Hauberg, Søren; Feragen, Aasa; Enficiaud, Raffi
2016-01-01
provide a simple algorithm for computing this Grassmann Average (GA), and show that the subspace estimate is less sensitive to outliers than PCA for general distributions. Because averages can be efficiently computed, we immediately gain scalability. We exploit robust averaging to formulate the Robust...
Kim, Dongcheol; Rhee, Sehun
2002-01-01
CO(2) welding is a complex process. Weld quality is dependent on arc stability and minimizing the effects of disturbances or changes in the operating condition commonly occurring during the welding process. In order to minimize these effects, a controller can be used. In this study, a fuzzy controller was used in order to stabilize the arc during CO(2) welding. The input variable of the controller was the Mita index. This index estimates quantitatively the arc stability that is influenced by many welding process parameters. Because the welding process is complex, a mathematical model of the Mita index was difficult to derive. Therefore, the parameter settings of the fuzzy controller were determined by performing actual control experiments without using a mathematical model of the controlled process. The solution, the Taguchi method was used to determine the optimal control parameter settings of the fuzzy controller to make the control performance robust and insensitive to the changes in the operating conditions.
Synthesis of Model Based Robust Stabilizing Reactor Power Controller for Nuclear Power Plant
Arshad Habib Malik
2011-04-01
Full Text Available In this paper, a nominal SISO (Single Input Single Output model of PHWR (Pressurized Heavy Water Reactor type nuclear power plant is developed based on normal moderator pump-up rate capturing the moderator level dynamics using system identification technique. As the plant model is not exact, therefore additive and multiplicative uncertainty modeling is required. A robust perturbed plant model is derived based on worst case model capturing slowest moderator pump-up rate dynamics and moderator control valve opening delay. Both nominal and worst case models of PHWR-type nuclear power plant have ARX (An Autoregressive Exogenous structures and the parameters of both models are estimated using recursive LMS (Least Mean Square optimization algorithm. Nominal and worst case discrete plant models are transformed into frequency domain for robust controller design purpose. The closed loop system is configured into two port model form and H? robust controller is synthesized. The H?controller is designed based on singular value loop shaping and desired magnitude of control input. The selection of desired disturbance attenuation factor and size of the largest anticipated multiplicative plant perturbation for loop shaping of H? robust controller form a constrained multi-objective optimization problem. The performance and robustness of the proposed controller is tested under transient condition of a nuclear power plant in Pakistan and found satisfactory.
Design of a robust superhydrophobic surface: thermodynamic and kinetic analysis
Sarkar, Anjishnu
2014-01-01
The design of a robust superhydrophobic surface is a widely pursued topic.While many investigations are limited to applications with high impact velocities (for raindrops of the order of a few m/s), the essence of robustness is yet to be analyzed for applications involving quasi-static liquid transfer.To achieve robustness with high impact velocities, the surface parameters (geometrical details, chemistry) have to be selected from a narrow range of permissible values, which often entail additional manufacturing costs.From the dual perspectives of thermodynamics and mechanics, we analyze the significance of robustness for quasi-static drop impact, and present the range of permissible surface characteristics.For surfaces with a Youngs contact angle greater than 90{\\deg} and square micropillar geometry, we show that robustness can be enforced when an intermediate wetting state (sagged state) impedes transition to a wetted state (Wenzel state).From the standpoint of mechanics, we use available scientific data to ...
一类前馈系统的鲁棒镇定%Robust Stabilization of a Class of Feedforward Systems
叶华文; 王红; 康剑灵
2005-01-01
Two kinds of saturated controllers are designed for a class of feedforward systems and the closed-loop resulted is locally input-to-state stable and input-to-state stable, respectively. By the word "locally", it is meant that there are restrictions on the amplitude of inputs. At first, under the guidance of suitable energy functions, two kinds of saturated controllers are designed as locally input-to-state stabilizers for a class of perturbed linear systems, from which explicit gain estimations can be obtained for the subsequent design. Then under the conditions that two subsystems of the feedforward system are respectively of locally input-to-state stability and input-to-state stability, the small gain theory is used to determine saturated degrees for corresponding robust stabilizers. The stability proofs are given by using a new characterization of input-to-state stability that is based on the concept of ultimate boundedness. As an application, saturated controllers are designed for the partial dynamics of a certain inverted pendulum.
LDRD final report : robust analysis of large-scale combinatorial applications.
Carr, Robert D.; Morrison, Todd (University of Colorado, Denver, CO); Hart, William Eugene; Benavides, Nicolas L. (Santa Clara University, Santa Clara, CA); Greenberg, Harvey J. (University of Colorado, Denver, CO); Watson, Jean-Paul; Phillips, Cynthia Ann
2007-09-01
Discrete models of large, complex systems like national infrastructures and complex logistics frameworks naturally incorporate many modeling uncertainties. Consequently, there is a clear need for optimization techniques that can robustly account for risks associated with modeling uncertainties. This report summarizes the progress of the Late-Start LDRD 'Robust Analysis of Largescale Combinatorial Applications'. This project developed new heuristics for solving robust optimization models, and developed new robust optimization models for describing uncertainty scenarios.
Robust and sensitive analysis of mouse knockout phenotypes.
Natasha A Karp
Full Text Available A significant challenge of in-vivo studies is the identification of phenotypes with a method that is robust and reliable. The challenge arises from practical issues that lead to experimental designs which are not ideal. Breeding issues, particularly in the presence of fertility or fecundity problems, frequently lead to data being collected in multiple batches. This problem is acute in high throughput phenotyping programs. In addition, in a high throughput environment operational issues lead to controls not being measured on the same day as knockouts. We highlight how application of traditional methods, such as a Student's t-Test or a 2-way ANOVA, in these situations give flawed results and should not be used. We explore the use of mixed models using worked examples from Sanger Mouse Genome Project focusing on Dual-Energy X-Ray Absorptiometry data for the analysis of mouse knockout data and compare to a reference range approach. We show that mixed model analysis is more sensitive and less prone to artefacts allowing the discovery of subtle quantitative phenotypes essential for correlating a gene's function to human disease. We demonstrate how a mixed model approach has the additional advantage of being able to include covariates, such as body weight, to separate effect of genotype from these covariates. This is a particular issue in knockout studies, where body weight is a common phenotype and will enhance the precision of assigning phenotypes and the subsequent selection of lines for secondary phenotyping. The use of mixed models with in-vivo studies has value not only in improving the quality and sensitivity of the data analysis but also ethically as a method suitable for small batches which reduces the breeding burden of a colony. This will reduce the use of animals, increase throughput, and decrease cost whilst improving the quality and depth of knowledge gained.
Profile Orientation and Slope Stability Analysis
Zhe-Ping Shen
2016-01-01
Full Text Available This paper presents an analysis of soil slope stability using a terrestrial laser scanner, particle swarm optimization, and the force equilibrium method. The aim of this study was to demonstrate that a slope needed to be analyzed in many different directions in order to assess its stability conclusively, rather than using just one cross-sectional profile to represent the entire slope. To achieve this purpose, this study illustrates how a particle swarm optimization algorithm can be successfully incorporated into the analysis with slope stability analysis software, STABL. This study compares results obtained with those of previous studies and makes important observations.
The computer in shell stability analysis
Almroth, B. O.; Starnes, J. H., Jr.
1975-01-01
Some examples in which the high-speed computer has been used to improve the static stability analysis capability for general shells are examined. The fundamental concepts of static stability are reviewed with emphasis on the differences between linear bifurcation buckling and nonlinear collapse. The analysis is limited to the stability of conservative systems. Three examples are considered. The problem of cylinders subjected to bending loads is used as an example to illustrate that a simple structure can have a sufficiently complicated nonlinear behavior to require a computer analysis for accurate results. An analysis of the problems involved in the modeling of stiffening elements in plate and shell structures illustrates the necessity that the analyst recognizes all important deformation modes. The stability analysis of the Skylab structure indicates the size of problems that can be solved with current state-of-the-art capability.
A robust silicon photonic platform for multiparameter biological analysis
Bailey, Ryan C.; Washburn, Adam L.; Qavi, Abraham J.; Iqbal, Muzammil; Gleeson, Martin; Tybor, Frank; Gunn, L. Cary
2009-02-01
Silicon photonic technology has incredible potential to transform multiplexed bioanalysis on account of the scalability of device fabrication, which maps favorably to a myriad of medical diagnostic applications. The optical properties of CMOS-fabricated microring resonators are incredibly responsive to changes in the local dielectric environment accompanying a biological binding event near the ring surface. Arrays of high-Q microrings were designed to be individually addressable both in surface derivitization, using well-established microarraying technologies, and in optical evaluation. The optical response of each ring can be determined in near real time allowing multiple biomolecular interactions to be simultaneously monitored. We describe a stable and robust measurement platform that allows sensitive visualization of small molecule surface chemical derivitization as well as monitoring of biological interactions, including the detection of proteins and nucleic acids. We also present recent results demonstrating multiplexed measurement of cancer markers. These demonstrations establish a pathway to higher level multiparameter analysis from real-world patient samples; a development that will enable individualized disease diagnostics and personalized medicine.
A robust polynomial principal component analysis for seismic noise attenuation
Wang, Yuchen; Lu, Wenkai; Wang, Benfeng; Liu, Lei
2016-12-01
Random and coherent noise attenuation is a significant aspect of seismic data processing, especially for pre-stack seismic data flattened by normal moveout correction or migration. Signal extraction is widely used for pre-stack seismic noise attenuation. Principle component analysis (PCA), one of the multi-channel filters, is a common tool to extract seismic signals, which can be realized by singular value decomposition (SVD). However, when applying the traditional PCA filter to seismic signal extraction, the result is unsatisfactory with some artifacts when the seismic data is contaminated by random and coherent noise. In order to directly extract the desired signal and fix those artifacts at the same time, we take into consideration the amplitude variation with offset (AVO) property and thus propose a robust polynomial PCA algorithm. In this algorithm, a polynomial constraint is used to optimize the coefficient matrix. In order to simplify this complicated problem, a series of sub-optimal problems are designed and solved iteratively. After that, the random and coherent noise can be effectively attenuated simultaneously. Applications on synthetic and real data sets note that our proposed algorithm can better suppress random and coherent noise and have a better performance on protecting the desired signals, compared with the local polynomial fitting, conventional PCA and a L1-norm based PCA method.
Power system stability modelling, analysis and control
Sallam, Abdelhay A
2015-01-01
This book provides a comprehensive treatment of the subject from both a physical and mathematical perspective and covers a range of topics including modelling, computation of load flow in the transmission grid, stability analysis under both steady-state and disturbed conditions, and appropriate controls to enhance stability.
Micro-simulation based analysis of railway lines robustness
Cerreto, Fabrizio
2015-01-01
Railway Undertakers and Railway Infrastructure Managers have a variety of parameters to measure robustness of timetables: this paper examines empirical data collected from Nederlandse Spoorwegen on the heavily occupied railway line between The Hague and Rotterdam in The Netherlands. The results...... show that the robustness indicator examined are affected by infrastructure changes in different ways. A micro-simulation of the line is used to determine the robustness of different railway infrastructure scenarios measuring the capacity consumption, as well as the share of trains affected by amount...
Jacobi stability analysis of Rikitake system
Gupta, M. K.; Yadav, C. K.
2016-06-01
We study the Rikitake system through the method of differential geometry, i.e. Kosambi-Cartan-Chern (KCC) theory for Jacobi stability analysis. For applying KCC theory we reformulate the Rikitake system as two second-order nonlinear differential equations. The five KCC invariants are obtained which express the intrinsic properties of nonlinear dynamical system. The deviation curvature tensor and its eigenvalues are obtained which determine the stability of the system. Jacobi stability of the equilibrium points is studied and obtain the conditions for stability. We study the dynamics of Rikitake system which shows the chaotic behaviour near the equilibrium points.
Computer Aided Transient Stability Analysis
Nihad M. Al-Rawi
2007-01-01
Full Text Available A program for handling and improving the transient stability of the Iraqi Super Grid electrical network was developed. The idea was demonstrated by applying it to the outages of the main generating units. The methodology was built upon a state of increasing power transfer through the healthy portion of network during disturbances. There were three parts concerned; the first part was the developing of the load flow program using fast decoupled method and the transient stability program using Modified Eulers method in the step by step solution, the second part was the engagement between the two programs, the third part was the application of the new program on the Iraqi supper grid network (400 kV.
Robustness analysis metrics for worldwide airport network: A comprehensive study
Xiaoqian Sun
2017-04-01
Full Text Available Robustness of transportation networks is one of the major challenges of the 21st century. This paper investigates the resilience of global air transportation from a complex network point of view, with focus on attacking strategies in the airport network, i.e., to remove airports from the system and see what could affect the air traffic system from a passenger’s perspective. Specifically, we identify commonalities and differences between several robustness measures and attacking strategies, proposing a novel notion of functional robustness: unaffected passengers with rerouting. We apply twelve attacking strategies to the worldwide airport network with three weights, and evaluate three robustness measures. We find that degree and Bonacich based attacks harm passenger weighted network most. Our evaluation is geared toward a unified view on air transportation network attack and serves as a foundation on how to develop effective mitigation strategies.
Embaby, Amira M; Saeed, Hesham; Hussein, Ahmed
2016-12-01
Present study underlines an unusual non-cumbersome-powerful strategy for purification of SHG10 keratinolytic alkaline protease from Bacillus licheniformis SHG10 DSM 28096 with robust stability properties. The enzyme was impressively purified to homogeneity with specific activity, purification fold, and yield of 613.82 U mg(-1) , 58.91 and 99%, respectively, via a sequential two-step purification strategy: precipitation with 65% (NH4 )2 SO4 and flow through fractions of DEAE-cellulose DE 53 column. SDS-PAGE conferred a monomeric enzyme with a molecular mass of 30.4 kDa. The enzyme demonstrated optimal activity at pH (10.0-11.0) and at 65 °C. It exhibited full stability at pH (6.0-11.0) over 38 h at 4 °C and at 65 °C for 15 min. Remarkable enhanced enzyme activity (130.15 and 126.37%) was retained in presence of commercial laundry detergents Oxi and Ariel after 1 h, respectively. Organic solvent stability of the enzyme was verified in butanol, ether, acetonitrile, isopropanol, and chloroform. Imposingly, full storage stability (100%) of the enzyme along 1 year in -20 °C was confirmed. Km -Vmax was 0.00174 mM-534.2 mM Sub · min(-1) · mg protein(-1) and 1.266 mg-28.89 mg Sub · h(-1) · mg protein(-1) on N-Suc-Ala-Ala-Pro-Phe-pNA and keratin azure, respectively. Robust stability properties of SHG10 keratinolytic alkaline protease along with rapid-efficient purification underpin its potential commercialization for industrial exploitation.
Robust Stability of a Class of Uncertain Lur'e Systems of Neutral Type
W. Weera
2012-01-01
Full Text Available This paper deals with the problem of stability for a class of Lur’e systems with interval time-varying delay and sector-bounded nonlinearity. The interval time-varying delay function is not assumed to be differentiable. We analyze the global exponential stability for uncertain neutral and Lur’e dynamical systems with some sector conditions. By constructing a set of improved Lyapunov-Krasovskii functional combined with Leibniz-Newton’s formula, we establish some stability criteria in terms of linear matrix inequalities. Numerical examples are given to illustrate the effectiveness of the results.
Analysis of a wavelet-based robust hash algorithm
Meixner, Albert; Uhl, Andreas
2004-06-01
This paper paper is a quantitative evaluation of a wavelet-based, robust authentication hashing algorithm. Based on the results of a series of robustness and tampering sensitivity tests, we describepossible shortcomings and propose variousmodifications to the algorithm to improve its performance. The second part of the paper describes and attack against the scheme. It allows an attacker to modify a tampered image, such that it's hash value closely matches the hash value of the original.
A Computational Method for Robust Bifurcation Analysis and Its Application to Biomolecular Systems
Inoue, Masaki; Ikuta, Hikaru; Adachi, Shuichi; Imura, Jun-Ichi; Aihara, Kazuyuki
2015-06-01
We consider a general uncertain nonlinear dynamical system defined in a certain model set, and reformulate a problem of robustness bifurcation analysis (RBA), which has been originally formulated in our previous work. As such, we develop an efficient computational method for the RBA, which can be used for quantitative evaluation of bifurcation robustness in uncertain dynamical systems. Specifically, we first linearize the uncertain system properly and then apply a feedback transformation technique to reduce the RBA problem to a linear robustness analysis one, which can be solved using μ-analysis, a common analysis technique in robust control theory. Finally, we provide robustness analysis of a gene regulatory network model where oscillatory behavior appears according to Hopf bifurcation. We give quantitative evaluation of the bifurcation robustness using the RBA method proposed here.
Multi-criteria robustness analysis of metro networks
Wang, Xiangrong; Koç, Yakup; Derrible, Sybil; Ahmad, Sk Nasir; Pino, Willem J. A.; Kooij, Robert E.
2017-05-01
Metros (heavy rail transit systems) are integral parts of urban transportation systems. Failures in their operations can have serious impacts on urban mobility, and measuring their robustness is therefore critical. Moreover, as physical networks, metros can be viewed as topological entities, and as such they possess measurable network properties. In this article, by using network science and graph theory, we investigate ten theoretical and four numerical robustness metrics and their performance in quantifying the robustness of 33 metro networks under random failures or targeted attacks. We find that the ten theoretical metrics capture two distinct aspects of robustness of metro networks. First, several metrics place an emphasis on alternative paths. Second, other metrics place an emphasis on the length of the paths. To account for all aspects, we standardize all ten indicators and plot them on radar diagrams to assess the overall robustness for metro networks. Overall, we find that Tokyo and Rome are the most robust networks. Rome benefits from short transferring and Tokyo has a significant number of transfer stations, both in the city center and in the peripheral area of the city, promoting both a higher number of alternative paths and overall relatively short path-lengths.
Frye, Michael Takaichi
This dissertation examines the problem of global decentralized control by output feedback for large-scale uncertain nonlinear systems whose subsystems are interconnected not only by their outputs but also by their unmeasurable states. Several innovative techniques will be developed to create decentralized output feedback controllers rendering the closed-loop systems globally asymptotically stable. This is accomplished by extending an output feedback domination design that requires only limited information about the nonlinear system. We will apply our design to lower, upper, and non-triangular nonlinear systems. A time-varying output feedback controller is also constructed for use with large-scale systems that have unknown parameters. Furthermore, a mixed large-scale system consisting of both lower and upper triangular systems is shown to be stabilizable by employing a combined high and low gain domination technique. The significance of our results is that we do not need to have prior information about the nonlinearities of the system. In addition, a new design technique was developed using homogeneous system theory, which allows for the design of nonsmooth controllers and observers to stabilize a class of feedforward system with uncontrollable and unobservable linearization. An example of a large-scale system is a group of autonomous airships performing the function of a temporary mobile cell phone network. An airship mobile cell phone network is a novel solution to the problem of maintaining communication during the advent of extensive damage to the communication infrastructure; be it from a flood, earthquake, hurricane, or terrorist attack. A first principle force-based dynamic model for the Tri-Turbofan Airship was developed and will be discussed in detail. The mathematical model was based on actual flight test data that has been collected at the Gait Analysis and Innovative Technologies Laboratory. This model was developed to research autonomous airship
无
2011-01-01
The visual servoing stabilization of nonholonomic mobile robot with unknown camera parameters is investigated.A new kind of uncertain chained model of nonholonomic kinemetic system is obtained based on the visual feedback and the standard chained form of type (1,2) mobile robot.Then,a novel time-varying feedback controller is proposed for exponentially stabilizing the position and orientation of the robot using visual feedback and switching strategy when the camera parameters are not known.The exponential s...
Stability analysis of peer-to-peer networks against churn
Bivas Mitra; Sujoy Ghose; Niloy Ganguly; Fernando Peruani
2008-08-01
Users of the peer-to-peer system join and leave the network randomly, which makes the overlay network dynamic and unstable in nature. In this paper, we propose an analytical framework to assess the robustness of p2p networks in the face of user churn. We model the peer churn through degree-independent as well as degree-dependent node failure. Lately, superpeer networks are becoming the most widely used topology among the p2p networks. Therefore, we perform the stability analysis of superpeer networks as a case study. We validate the analytically derived results with the help of simulation.
Yi-You Hou
2014-01-01
Full Text Available This paper considers the problem of the robust stability for the nonlinear system with time-varying delay and parameters uncertainties. Based on the H∞ theorem, Lyapunov-Krasovskii theory, and linear matrix inequality (LMI optimization technique, the H∞ quasi-sliding mode controller and switching function are developed such that the nonlinear system is asymptotically stable in the quasi-sliding mode and satisfies the disturbance attenuation (H∞-norm performance. The effectiveness and accuracy of the proposed methods are shown in numerical simulations.
Huynh, Huynh; Rawls, Anita
2011-01-01
There are at least two procedures to assess item difficulty stability in the Rasch model: robust z procedure and "0.3 Logit Difference" procedure. The robust z procedure is a variation of the z statistic that reduces dependency on outliers. The "0.3 Logit Difference" procedure is based on experiences in Rasch linking for tests…
Robust image analysis with sparse representation on quantized visual features.
Bao, Bing-Kun; Zhu, Guangyu; Shen, Jialie; Yan, Shuicheng
2013-03-01
Recent techniques based on sparse representation (SR) have demonstrated promising performance in high-level visual recognition, exemplified by the highly accurate face recognition under occlusion and other sparse corruptions. Most research in this area has focused on classification algorithms using raw image pixels, and very few have been proposed to utilize the quantized visual features, such as the popular bag-of-words feature abstraction. In such cases, besides the inherent quantization errors, ambiguity associated with visual word assignment and misdetection of feature points, due to factors such as visual occlusions and noises, constitutes the major cause of dense corruptions of the quantized representation. The dense corruptions can jeopardize the decision process by distorting the patterns of the sparse reconstruction coefficients. In this paper, we aim to eliminate the corruptions and achieve robust image analysis with SR. Toward this goal, we introduce two transfer processes (ambiguity transfer and mis-detection transfer) to account for the two major sources of corruption as discussed. By reasonably assuming the rarity of the two kinds of distortion processes, we augment the original SR-based reconstruction objective with l(0) norm regularization on the transfer terms to encourage sparsity and, hence, discourage dense distortion/transfer. Computationally, we relax the nonconvex l(0) norm optimization into a convex l(1) norm optimization problem, and employ the accelerated proximal gradient method to optimize the convergence provable updating procedure. Extensive experiments on four benchmark datasets, Caltech-101, Caltech-256, Corel-5k, and CMU pose, illumination, and expression, manifest the necessity of removing the quantization corruptions and the various advantages of the proposed framework.
Azizi, Sajad
2017-05-01
The robust stability of a class of feedback linearizable minimum-phase nonlinear system, having parametric uncertainties, is investigated in this study. The system in new coordinates is represented to an equivalent formulation after the attempt of feedback linearization. Due to the parametric uncertainties the approximately linearized system entails a norm bounded input nonlinearity such that the equilibrium point condition in error dynamics can not be satisfied. Accordingly, to guarantee the regional asymptotic stability a control synthesis problem is proposed by means of sufficient Linear Matrix Inequalities (LMIs) together with an amended nonlinear control term, derived from the Lyapunov redesign method, which tackles zero steady-state error condition. The numerical examples of a general aviation aircraft's longitudinal dynamics and inverted pendulum are simulated to show the proficiency of the proposed control technique. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Robustness Analysis of Typologies of Reciprocal Timber Structures
Kirkegaard, Poul Henning; Parigi, Dario
2013-01-01
Robustness of structural systems has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. In order to minimise the likelihood of such disproportionate structural failures many modern buildi...... to the future development of typologies of reciprocal timber structures. The paper concludes that these kinds of structures can have a potential as long span timber structures in real projects if they are carefully designed with respect to the overall robustness strategies....
Fei Song
2014-01-01
Full Text Available This paper proposed a robust fault-tolerant control algorithm for satellite stabilization based on active disturbance rejection approach with artificial bee colony algorithm. The actuating mechanism of attitude control system consists of three working reaction flywheels and one spare reaction flywheel. The speed measurement of reaction flywheel is adopted for fault detection. If any reaction flywheel fault is detected, the corresponding fault flywheel is isolated and the spare reaction flywheel is activated to counteract the fault effect and ensure that the satellite is working safely and reliably. The active disturbance rejection approach is employed to design the controller, which handles input information with tracking differentiator, estimates system uncertainties with extended state observer, and generates control variables by state feedback and compensation. The designed active disturbance rejection controller is robust to both internal dynamics and external disturbances. The bandwidth parameter of extended state observer is optimized by the artificial bee colony algorithm so as to improve the performance of attitude control system. A series of simulation experiment results demonstrate the performance superiorities of the proposed robust fault-tolerant control algorithm.
Davison Daniel E.
2000-01-01
Full Text Available This paper deals with the notion of disturbance model uncertainty. The disturbance is modeled as the output of a first-order filter which is driven by white noise and whose bandwidth and gain are uncertain. An analytical expression for the steady-state output variance as a function of the uncertain bandwidth and gain is derived, and several properties of this variance function are analyzed. Two notions, those of disturbance bandwidth margin and disturbance gain margin are also introduced. These tools are then applied to the analysis of a simple altitude-hold autopilot system in the presence of turbulence where the turbulence scale is treated as an uncertain parameter. It is shown that the autopilot, which is satisfactory for nominal turbulence scale, may be inadequate when the uncertainty is taken into account. Moreover, it is proven that, in order to obtain a design that provides robust performance in the face of turbulence scale uncertainty, it is necessary to substantially increase the controller bandwidth, even if one is willing to sacrifice the autopilot's holding ability and stability robustness.
Stability analysis of free piston Stirling engines
Bégot, Sylvie; Layes, Guillaume; Lanzetta, François; Nika, Philippe
2013-03-01
This paper presents a stability analysis of a free piston Stirling engine. The model and the detailed calculation of pressures losses are exposed. Stability of the machine is studied by the observation of the eigenvalues of the model matrix. Model validation based on the comparison with NASA experimental results is described. The influence of operational and construction parameters on performance and stability issues is exposed. The results show that most parameters that are beneficial for machine power seem to induce irregular mechanical characteristics with load, suggesting that self-sustained oscillations could be difficult to maintain and control.
Zhuanxian Xiong; Yun Long; Huixing Xiao; Xi Zhang; Lingxiang He; Baolong Lu
2011-01-01
A frequency-stabilized 556-nm laser is an essential tool for experimental studies associated with 1S0-3p1 intercombination transition of ytterbium (Yb) atoms. A 556-nm laser light using a single-pass second harmonic generation (SHG) is obtained in a periodically poled MgO:LiNbO3 (PPLN) crystal pumped by a fiber laser at 1111.6 nm. A robust frequency stabilization method which facilitates the control of laser frequency with an accuracy better than the natural linewidth (187 kHz) of the intercombination line is developed. The short-term frequency jitter is reduced to less than 100 kHz by locking the laser to a home-made reference cavity. A slow frequency drift is sensed by the 556-nm fluorescence signal of an Yb atomic beam excited by one probe beam and is reduced to less than 50-kHz by a computer-controlled servo system. The laser can be stably locked for more than 5 h. This frequency stabilization method can be extended to other alkaline-earth-like atoms with similar weak intercombination lines.%@@ A frequency-stabilized 556-nm laser is an essential tool for experimental studies associated with 1So-3P1intercombination transition of ytterbium (Yb) atoms.A 556-nm laser light using a single-pass second harmonic generation (SHG) is obtained in a periodically poled MgO:LiNbO3 (PPLN) crystal pumped by a fiber laser at 1111.6 nm.A robust frequency stabilization method which facilitates the control of laser frequency with an accuracy better than the natural linewidth (187 kHz) of the intercombination line is developed.The short-term frequency jitter is reduced to less than i00 kHz by locking the laser to a home-made reference cavity.A slow frequency drift is sensed by the 556-nm fluorescence signal of an Yb atomic beam excited by one probe beam and is reduced to less than 50-kHz by a computer-controlled servo system.The laser can be stably locked for more than 5 h.This frequency stabilization method can be extended to other alkaline-earth-like atoms with similar weak
Robust Output Stabilization of Time-Varying Input Delay Systems using Attractive Ellipsoid Method
Polyakov, Andrey; Poznyak, Alexander; Richard, Jean-Pierre
2013-01-01
International audience; The problem of output control design for linear system with unknown and time-varying input delay, bounded exogenous disturbances and bounded deterministic measurement noises is considered. The prediction technique is combined with Luenberger-like observer design in order to provide the stabilizing output feedback. The scheme of parameters tuning for reduction of measurement noises effect and exogenous disturbances effects is developed basing on Attractive Ellipsoids Me...
Robust stabilization of underactuated nonlinear systems: A fast terminal sliding mode approach.
Khan, Qudrat; Akmeliawati, Rini; Bhatti, Aamer Iqbal; Khan, Mahmood Ashraf
2017-01-01
This paper presents a fast terminal sliding mode based control design strategy for a class of uncertain underactuated nonlinear systems. Strategically, this development encompasses those electro-mechanical underactuated systems which can be transformed into the so-called regular form. The novelty of the proposed technique lies in the hierarchical development of a fast terminal sliding attractor design for the considered class. Having established sliding mode along the designed manifold, the close loop dynamics become finite time stable which, consequently, result in high precision. In addition, the adverse effects of the chattering phenomenon are reduced via strong reachability condition and the robustness of the system against uncertainties is confirmed theoretically. A simulation as well as experimental study of an inverted pendulum is presented to demonstrate the applicability of the proposed technique.
Observer-based robust stabilization for uncertain systems with unknown time-varying delay
Peigang JIANG; Chunwen LI
2004-01-01
This paper focuses on the problem of robust stabiiization for a class of linear systems with uncertain parameters and time varying delays in states. The parameter uncertainty is continuous, time varying, and norm-bounded. The state delay is unknown and time varying. The states of the system are not all measurable and an observer is constructed to estimate the states. If a linear matrix inequality (LMI) is solvable, the gains of the controller and observer can be obtained from the solution of the LMI.The observer and controller are dependent on the size of time delay and on the size of delay derivative. Finally, an example is given to illustrate the effectiveness of the proposed control method.
Nanoporous membrane robustness / stability in small form factor microfluidic filtration system.
Johnson, Dean G; Pan, Sabrina; Hayden, Andrew; McGrath, James L
2016-08-01
The development of wearable hemodialysis (HD) devices that replace center-based HD holds the promise to improve both outcomes and quality-of-life for patients with end-stage-renal disease (ERD). A prerequisite for these devices is the development of highly efficient membranes that can achieve high toxin clearance in small footprints. The ultrathin nanoporous membrane material developed by our group is orders of magnitude more permeable than conventional HD membranes. We report on our progress making a prototype wearable dialysis unit. First, we present data from benchtop studies confirming that clinical levels of urea clearance can be obtained in a small animal model with low blood flow rates. Second, we report on efforts to improve the mechanical robustness of high membrane area dialysis devices.
Logical and symbolic analysis of robust biological dynamics.
Glass, Leon; Siegelmann, Hava T
2010-12-01
Logical models provide insight about key control elements of biological networks. Based solely on the logical structure, we can determine state transition diagrams that give the allowed possible transitions in a coarse grained phase space. Attracting pathways and stable nodes in the state transition diagram correspond to robust attractors that would be found in several different types of dynamical systems that have the same logical structure. Attracting nodes in the state transition diagram correspond to stable steady states. Furthermore, the sequence of logical states appearing in biological networks with robust attracting pathways would be expected to appear also in Boolean networks, asynchronous switching networks, and differential equations having the same underlying structure. This provides a basis for investigating naturally occurring and synthetic systems, both to predict the dynamics if the structure is known, and to determine the structure if the transitions are known.
Robust Control of Underactuated Manipulators: Analysis and Implementation
1994-05-01
Y Control of mechanical systems with second-order nonholonomic constraints: underactuated manipulators. Proc. of the 30th Conference on Decision and...any of a series of controllers fully developed in the literature for mechanical manipulators. Because the control of such a system is fully dependent...robust controller for underactuated manipulators. The control of such systems can be extended to the control problem of fault-tolerant robots, space
Linear stability analysis of heated parallel channels
Nourbakhsh, H. P.; Isbin, H. S.
An analyis is presented of thermal hydraulic stability of flow in parallel channels covering the range from inlet subcooling to exit superheat. The model is based on a one-dimensional drift velocity formulation of the two phase flow conservation equations. The system of equations is linearized by assuming small disturbances about the steady state. The dynamic response of the system to an inlet flow perturbation is derived yielding the characteristic equation which predicts the onset of instabilities. A specific application is carried out for homogeneous and regional uniformly heated systems. The particular case of equal characteristic frequencies of two-phase and single phase vapor region is studied in detail. The D-partition method and the Mikhailov stability criterion are used for determining the marginal stability boundary. Stability predictions from the present analysis are compared with the experimental data from the solar test facility.
Thermal stability of the DSC ruthenium dye C106 in robust electrolytes
Lund, Torben; Phuong, Nguyen Tuyet; Pechy, Peter
2014-01-01
the dye from the TiO2 particles and analyzed its by HPLC coupled to UV/Vis and electro spray mass spectrometry. Samples prepared in the glove box gave the highest stability with a steady state photo anode surface concentration of 80% C106 intact and the remaining ∼20% being the N-butylbenzimidazole (NBB......We have investigated the thermal stability of the heteroleptic ruthenium complex C106 employed as a sensitizer in dye-sensitized solar cells. The C106 was adsorbed on TiO2 particles and exposed to 2 different iodide/triidode based redox electrolytes A and B at 80 °C for up to 1500 h in sealed glass...... of the degree of dye loading of the TiO2 particles and the ratio between the amount of dyed TiO2 particles and electrolyte volume. Assuming that this substitution is the predominant loss mechanism in a DSC during thermal stress, we estimate the reduction in the DSC efficiency after long term heat to be 12...
Minakshi, Manickam; Barmi, Maryam J; Jones, Robert T
2017-03-14
Hybrid capacitors can replace or complement batteries, while storing energy through ion adsorption and fast surface redox reactions. There is a growing demand in developing nanostructured materials as electrodes for hybrid systems that can enhance the specific capacitance by ion desolvation in the nanopores. Here, we demonstrate that rescaling the pore diameter with the aid of biopolymer at an optimal level during the synthesis of metal molybdate leads to high capacitance 124 F g(-1) giving robust capacitance retention of 80% over 2000 cycles for a constructed device (activated carbon vs. metal molybdate). The presence of biopolymer (l-glutamic acid) in the metal molybdate acts as a complexing agent of the metal ion while enhancing the mass transport and hence it's improved electrochemical performance. However, XPS and other elemental analyses illustrated no evidence for N doping but traces of other surface functional groups (i.e. C and O) could be present on the molybdate surface. The biopolymer synthetic approach has the advantage of yielding nanostructured material with a relatively narrow pore size distribution controlled by l-glutamic acid. This study will provide a generic route to rescale other metal molybdate, phosphate or oxide counterparts and be an added value to the database.
Collaborative Research: Robust Climate Projections and Stochastic Stability of Dynamical Systems
Ghil, Michael; McWilliams, James; Neelin, J. David; Zaliapin, Ilya; Chekroun, Mickael; Kondrashov, Dmitri; Simonnet, Eric
2011-10-13
The project was completed along the lines of the original proposal, with additional elements arising as new results were obtained. The originally proposed three thrusts were expanded to include an additional, fourth one. (i) The e ffects of stochastic perturbations on climate models have been examined at the fundamental level by using the theory of deterministic and random dynamical systems, in both nite and in nite dimensions. (ii) The theoretical results have been implemented first on a delay-diff erential equation (DDE) model of the El-Nino/Southern-Oscillation (ENSO) phenomenon. (iii) More detailed, physical aspects of model robustness have been considered, as proposed, within the stripped-down ICTP-AGCM (formerly SPEEDY) climate model. This aspect of the research has been complemented by both observational and intermediate-model aspects of mid-latitude and tropical climate. (iv) An additional thrust of the research relied on new and unexpected results of (i) and involved reduced-modeling strategies and associated prediction aspects have been tested within the team's empirical model reduction (EMR) framework. Finally, more detailed, physical aspects have been considered within the stripped-down SPEEDY climate model. The results of each of these four complementary e fforts are presented in the next four sections, organized by topic and by the team members concentrating on the topic under discussion.
Quantifying robustness of biochemical network models
Iglesias Pablo A
2002-12-01
Full Text Available Abstract Background Robustness of mathematical models of biochemical networks is important for validation purposes and can be used as a means of selecting between different competing models. Tools for quantifying parametric robustness are needed. Results Two techniques for describing quantitatively the robustness of an oscillatory model were presented and contrasted. Single-parameter bifurcation analysis was used to evaluate the stability robustness of the limit cycle oscillation as well as the frequency and amplitude of oscillations. A tool from control engineering – the structural singular value (SSV – was used to quantify robust stability of the limit cycle. Using SSV analysis, we find very poor robustness when the model's parameters are allowed to vary. Conclusion The results show the usefulness of incorporating SSV analysis to single parameter sensitivity analysis to quantify robustness.
Analysis of Robustness of PID-GPC Based on IMC Structure
陈增强; 毛宗星; 等
2003-01-01
Proportion integral differential generalized predictive control(PID-GPC),a new type of generalized predictive control(GPC) is introduced,and its quality is analyzed with internal model contron(IMC).A very important characteristic,which distinguishes GPC from ordinary IMC,and the robust effect are found.At the same time,a robust region is obtained according to the control laws,so that the defect that the robust analysis could be carried out only with stable models is vercome.It is verified that the robustness of PID-GPC is stronger than general GPC.
Robustness Analysis of Road Networks: a Framework with Combined DTA Models
Li, M.
2008-01-01
Network robustness is the ability of a road network functioning properly facing unpredictable and exceptional incidents. A systematical framework with combined dynamic traffic assignment (DTA) models is designed for the analysis of road network robustness. With this framework, network performance co
More stability and robustness with the multi-loop control solution for dynamic voltage restorer (DVR
Abdelkhalek Othmane
2009-01-01
Full Text Available This paper presents the application of dynamic voltage restorers (DVR on power distribution systems for mitigation of voltage sags/swells at critical loads. DVR is one of the compensating types of custom power devices. An adequate modeling and simulation of DVR, including controls in MATLAB, based on forced-commutated voltage source converter (VSC, has been proved suitable for compensating the voltage sags/swells. In this paper, a double loop control method is proposed for the improvement of the stability of DVR during the load current variation. For the main loop (Outer Voltage Loop, we use a PI controller for the regulation of the filter condenser voltage. The second loop (Inner Current Loop also uses a PI controller to control the disturbances current during load variation. Simulation results are presented to illustrate and understand the performances of DVR in the compensation of voltage sags/swell even with variation load condition.
Application of Coordinated SOFC and SMES Robust Control for Stabilizing Tie-Line Power
Wei Liu
2013-04-01
Full Text Available Wind power causes fluctuations in power systems and introduces issues concerning system stability and power quality because of the lack of controllability of its discontinuous and intermittent resources. This paper presents a coordinated control strategy for solid oxide fuel cells (SOFCs and superconducting magnetic energy storage (SMES to match the intermittent wind power generation and compensate for the rapid load changes. An optimal H∞ control method, where the weighting function selection is expressed as an optimization problem, is proposed to mitigate tie-line power fluctuations and the mixed-sensitivity approach is used to deal with the interference suppression. Simulation results show that the proposed method significantly improves the smoothing effect of wind power fluctuations. Compared with the conventional control method, the proposed method has better anti-interference performance in various operating situations.
Zhang Jinhui [Department of Automatic Control, Beijing Institute of Technology, Beijing 100081 (China)], E-mail: jinhuizhang82@gmail.com; Shi Peng [Faculty of Advanced Technology, University of Glamorgan, Pontypridd CF37 1DL (United Kingdom); ILSCM, School of Science and Engineering, Victoria University, Melbourne, Vic. 8001 (Australia); School of Mathematics and Statistics, University of South Australia, Mawson Lakes, SA 5095 (Australia)], E-mail: pshi@glam.ac.uk; Yang Hongjiu [Department of Automatic Control, Beijing Institute of Technology, Beijing 100081 (China)], E-mail: yanghongjiu@gmail.com
2009-12-15
This paper deals with the problem of non-fragile robust stabilization and H{sub {infinity}} control for a class of uncertain stochastic nonlinear time-delay systems. The parametric uncertainties are real time-varying as well as norm bounded. The time-delay factors are unknown and time-varying with known bounds. The aim is to design a memoryless non-fragile state feedback control law such that the closed-loop system is stochastically asymptotically stable in the mean square and the effect of the disturbance input on the controlled output is less than a prescribed level for all admissible parameter uncertainties. New sufficient conditions for the existence of such controllers are presented based on the linear matrix inequalities (LMIs) approach. Numerical example is given to illustrate the effectiveness of the developed techniques.
Yanke Du
2013-01-01
Full Text Available A class of interval Cohen-Grossberg neural networks with time-varying delays and infinite distributed delays is investigated. By employing H-matrix and M-matrix theory, homeomorphism techniques, Lyapunov functional method, and linear matrix inequality approach, sufficient conditions are established for the existence, uniqueness, and global robust exponential stability of the equilibrium point and the periodic solution to the neural networks. Our results improve some previously published ones. Finally, numerical examples are given to illustrate the feasibility of the theoretical results and further to exhibit that there is a characteristic sequence of bifurcations leading to a chaotic dynamics, which implies that the system admits rich and complex dynamics.
Xungao Zhong
2013-10-01
Full Text Available In this paper, a global-state-space visual servoing scheme is proposed for uncalibrated model-independent robotic manipulation. The scheme is based on robust Kalman filtering (KF, in conjunction with Elman neural network (ENN learning techniques. The global map relationship between the vision space and the robotic workspace is learned using an ENN. This learned mapping is shown to be an approximate estimate of the Jacobian in global space. In the testing phase, the desired Jacobian is arrived at using a robust KF to improve the ENN learning result so as to achieve robotic precise convergence of the desired pose. Meanwhile, the ENN weights are updated (re-trained using a new input-output data pair vector (obtained from the KF cycle to ensure robot global stability manipulation. Thus, our method, without requiring either camera or model parameters, avoids the corrupted performances caused by camera calibration and modeling errors. To demonstrate the proposed scheme’s performance, various simulation and experimental results have been presented using a six-degree-of-freedom robotic manipulator with eye-in-hand configurations.
Stock market stability: Diffusion entropy analysis
Li, Shouwei; Zhuang, Yangyang; He, Jianmin
2016-05-01
In this article, we propose a method to analyze the stock market stability based on diffusion entropy, and conduct an empirical analysis of Dow Jones Industrial Average. Empirical results show that this method can reflect the volatility and extreme cases of the stock market.
Robustness analysis of uncertain dynamical neural networks with multiple time delays.
Senan, Sibel
2015-10-01
This paper studies the problem of global robust asymptotic stability of the equilibrium point for the class of dynamical neural networks with multiple time delays with respect to the class of slope-bounded activation functions and in the presence of the uncertainties of system parameters of the considered neural network model. By using an appropriate Lyapunov functional and exploiting the properties of the homeomorphism mapping theorem, we derive a new sufficient condition for the existence, uniqueness and global robust asymptotic stability of the equilibrium point for the class of neural networks with multiple time delays. The obtained stability condition basically relies on testing some relationships imposed on the interconnection matrices of the neural system, which can be easily verified by using some certain properties of matrices. An instructive numerical example is also given to illustrate the applicability of our result and show the advantages of this new condition over the previously reported corresponding results.
Steel Augmented Production Function: Robust Analysis for European Union
Bilal Mehmood
2017-03-01
Full Text Available This study contributes to the empirical literature on augmented neo-classical production function. It is done by introducing steel production into macro-production function of the European Union. The data is collected from the World Development Indicators and the World Steel Association from the period of 1980–2014. We apply second generations of unit root tests to examine stationarity and panel cointegration with cross-sectional dependence to analyze long run relationship between national income and steel production. Robustness of tests is also reached by using 23 estimators and country specific slopes. Whereas, to detect the cause and effect, Granger and Dumitrescu-Hurlin causality tests are applied. Uni-directional causality from national income to steel production is found. Recommendations are made on the basis of empirical results.
Design of LLCL-filter for grid-connected converter to improve stability and robustness
Huang, Min; Wang, Xiongfei; Loh, Poh Chiang;
2015-01-01
The LLCL-filter has recently emerged into gridconnected converters due to the improved filtering capability which ensuring a smaller physical size. An LLCL -based gridconnected converter has almost the same frequency-response characteristic as that with the traditional LCL-filter within half of t...... for LLCL-filter is given. Both simulations and experimental results are provided through a 5 kW, 380V/50 Hz grid-connected inverter model to validate the theoretical analysis in this paper....
Sirada Pinjai
2013-01-01
Full Text Available This paper is concerned with the problem of robust exponential stability for linear parameter-dependent (LPD neutral systems with mixed time-varying delays and nonlinear perturbations. Based on a new parameter-dependent Lyapunov-Krasovskii functional, Leibniz-Newton formula, decomposition technique of coefficient matrix, free-weighting matrices, Cauchy’s inequality, modified version of Jensen’s inequality, model transformation, and linear matrix inequality technique, new delay-dependent robust exponential stability criteria are established in terms of linear matrix inequalities (LMIs. Numerical examples are given to show the effectiveness and less conservativeness of the proposed methods.
A Robust Color Object Analysis Approach to Efficient Image Retrieval
Ruofei Zhang
2004-06-01
Full Text Available We describe a novel indexing and retrieval methodology integrating color, texture, and shape information for content-based image retrieval in image databases. This methodology, we call CLEAR, applies unsupervised image segmentation to partition an image into a set of objects. Fuzzy color histogram, fuzzy texture, and fuzzy shape properties of each object are then calculated to be its signature. The fuzzification procedures effectively resolve the recognition uncertainty stemming from color quantization and human perception of colors. At the same time, the fuzzy scheme incorporates segmentation-related uncertainties into the retrieval algorithm. An adaptive and effective measure for the overall similarity between images is developed by integrating properties of all the objects in every image. In an effort to further improve the retrieval efficiency, a secondary clustering technique is developed and employed, which significantly saves query processing time without compromising retrieval precision. A prototypical system of CLEAR, we developed, demonstrated the promising retrieval performance and robustness in color variations and segmentation-related uncertainties for a test database containing 10Ã¢Â€Â‰000 general-purpose color images, as compared with its peer systems in the literature.
Graph theory and stability analysis of protein complex interaction networks.
Huang, Chien-Hung; Chen, Teng-Hung; Ng, Ka-Lok
2016-04-01
Protein complexes play an essential role in many biological processes. Complexes can interact with other complexes to form protein complex interaction network (PCIN) that involves in important cellular processes. There are relatively few studies on examining the interaction topology among protein complexes; and little is known about the stability of PCIN under perturbations. We employed graph theoretical approach to reveal hidden properties and features of four species PCINs. Two main issues are addressed, (i) the global and local network topological properties, and (ii) the stability of the networks under 12 types of perturbations. According to the topological parameter classification, we identified some critical protein complexes and validated that the topological analysis approach could provide meaningful biological interpretations of the protein complex systems. Through the Kolmogorov-Smimov test, we showed that local topological parameters are good indicators to characterise the structure of PCINs. We further demonstrated the effectiveness of the current approach by performing the scalability and data normalization tests. To measure the robustness of PCINs, we proposed to consider eight topological-based perturbations, which are specifically applicable in scenarios of targeted, sustained attacks. We found that the degree-based, betweenness-based and brokering-coefficient-based perturbations have the largest effect on network stability.
Wenjuan ZHANG; Li CHEN; Ning QU; Hai'an LIANG
2006-01-01
Landslide is one kind of geologic hazards that often happens all over the world. It brings huge losses to human life and property; therefore, it is very important to research it. This study focused in combination between single and regional landslide, traditional slope stability analysis method and reliability analysis method. Meanwhile, methods of prediction of slopes and reliability analysis were discussed.
Visual optimality and stability analysis of 3DCT scan positions.
Amirkhanov, Artem; Heinzl, Christoph; Reiter, Michael; Gröller, Eduard
2010-01-01
Industrial cone-beam X-Ray computed tomography (CT) systems often face problems due to artifacts caused by a bad placement of the specimen on the rotary plate. This paper presents a visual-analysis tool for CT systems, which provides a simulation-based preview and estimates artifacts and deviations of a specimen's placement using the corresponding 3D geometrical surface model as input. The presented tool identifies potentially good or bad placements of a specimen and regions of a specimen, which cause the major portion of artefacts. The tool can be used for a preliminary analysis of the specimen before CT scanning, in order to determine the optimal way of placing the object. The analysis includes: penetration lengths, placement stability and an investigation in Radon space. Novel visualization techniques are applied to the simulation data. A stability widget is presented for determining the placement parameters' robustness. The performance and the comparison of results provided by the tool compared with real world data is demonstrated using two specimens.
黄剑; 关治洪; 王仲东
2005-01-01
The data packet dropouts phenomenon is usually inevitable when information transmitted among communication networks. In this paper, the robust stabilization problem for uncertain networked control systems with data packet dropouts is studied. First, an uncertain discrete-time switching system model is presented to describe these networked control systems. The stability equivalence is then proved between this switching system and an uncertain impulsive difference system.Moreover, a sufficient condition is obtained for the asymptotical stability of the nonlinear impulsive difference system. From this condition the robust stabilization problem is dealt with for the uncertain impulsive system. Main results are given in linear matrix inequalities. Finally a numerical example is given to illustrate the theoretical results.
董楸煌; 陈力
2015-01-01
分析漂浮基双臂空间机器人捕获非合作目标所受的冲击影响效应，及捕获后空间机器人和目标组成的闭链混合系统对目标夹持内力和位形的鲁棒镇定控制。将捕获目标过程视为两机械臂末端与目标碰撞前、碰撞过程和碰撞后三个阶段。在碰撞前空间机器人和目标是分离的两分体系统，利用第二类拉格朗日方程建立漂浮基双臂空间机器人系统的动力学模型。在机械臂末端与目标碰撞阶段，基于空间机器人与目标总动量守恒，利用动量定理计算翻滚目标对空间机器人运动状态的冲击影响效应。在碰撞后，双臂空间机器人已捕获翻滚目标并组成闭链混合系统，针对混合系统在碰撞阶段受冲击影响而产生不稳定运动，提出一种鲁棒控制算法对其进行镇定控制，以实现双臂对目标夹持内力和空间机器人位形的协调控制，并达到期望的稳定状态。数值仿真验证了上述控制算法的有效性。%The impact effect of a free-floating dual-arm space robot to capture a non-cooperative target is analyzed, and during the post-capture the space robot and the target compose a closed-chaln hybrid system, then a clamp force and position robust stabilization control is discussed. The target capture process is considered as pre-impact phase,impact phase and post-impact phase. The space robot and target are separated subsystem in the pre-impact phase, and the dynamics model of free-floating space robot is derived by the second Lagrange equation. In the impact phase, base on the total momentum conservation of space robot and target, the impact effect for the space robot motion is calculated by momentum theorem. In the post-impact phase, the dual-arm space robot has captured the target and formed a closed-chaln hybrid system, considering the unstable motion which is caused by the impact effect in the impact phase, a robust control algorithm is proposed
Dynamic Stability Analysis Using High-Order Interpolation
Juarez-Toledo C.
2012-10-01
Full Text Available A non-linear model with robust precision for transient stability analysis in multimachine power systems is proposed. The proposed formulation uses the interpolation of Lagrange and Newton's Divided Difference. The High-Order Interpolation technique developed can be used for evaluation of the critical conditions of the dynamic system.The technique is applied to a 5-area 45-machine model of the Mexican interconnected system. As a particular case, this paper shows the application of the High-Order procedure for identifying the slow-frequency mode for a critical contingency. Numerical examples illustrate the method and demonstrate the ability of the High-Order technique to isolate and extract temporal modal behavior.
Stability analysis for bad cavity lasers with inhomogeneously broadened gain
Kazakov, Georgy A
2016-01-01
Bad cavity lasers are experiencing renewed interest in the context of active optical frequency standards, due to their enhanced robustness against fluctuations of the laser cavity. The gain medium would consist of narrow-linewidth atoms, either trapped inside the cavity or intersecting the cavity mode dynamically. A finite velocity distribution, atomic interactions, or interactions of realistic multilevel atoms with external field leads to an inhomogeneous broadening of the atomic gain profile. This can bring the bad cavity laser to operate in unstable regimes characterized by complex temporal patterns of the field amplitude. We present a new and efficient method for the stability analysis of bad cavity lasers with inhomogeneously broadened gain. We apply this method to identify the steady-state solutions for the metrology-relevant case of spin-1/2 atoms interacting with an external magnetic field.
Nonlinear physical systems spectral analysis, stability and bifurcations
Kirillov, Oleg N
2013-01-01
Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam
Multispectral Image Analysis for Robust Prediction of Astaxanthin Coating
Ljungqvist, Martin Georg; Frosch, Stina; Nielsen, Michael Engelbrecht
2013-01-01
The aim of this study was to investigate the possibility of predicting the type and concentration level of astaxanthin coating of aquaculture feed pellets using multispectral image analysis. We used both natural and synthetic astaxanthin, and we used several different concentration levels...... of synthetic astaxanthin in combination with four different recipes of feed pellets. We used a VideometerLab with 20 spectral bands in the range of 385-1050 nm. We used linear discriminant analysis and sparse linear discriminant analysis for classification and variable selection. We used partial least squares...
Linear Stability Analysis of Dynamical Quadratic Gravity
Ayzenberg, Dimitry; Yunes, Nicolas
2013-01-01
We perform a linear stability analysis of dynamical, quadratic gravity in the high-frequency, geometric optics approximation. This analysis is based on a study of gravitational and scalar modes propagating on spherically-symmetric and axially-symmetric, vacuum solutions of the theory. We find dispersion relations that do no lead to exponential growth of the propagating modes, suggesting the theory is linearly stable on these backgrounds. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity.
Li, XS; Narayanan, S; Michaelis, VK; Ong, TC; Keeler, EG; Kim, H; Mckay, IS; Griffin, RG; Wang, EN
2015-01-01
Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg, Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the lab-scale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N-2 sorption, Al-27/Si-29 MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N-2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. (C) 2014 Elsevier Inc. All rights reserved.
Leng, Y; Wang, Z; Tsai, L-K; Leeds, P; Fessler, E B; Wang, J; Chuang, D-M
2015-02-01
Fibroblast growth factor-21 (FGF-21) is a new member of the FGF super-family and an important endogenous regulator of glucose and lipid metabolism. It has been proposed as a therapeutic target for diabetes and obesity. Its function in the central nervous system (CNS) remains unknown. Previous studies from our laboratory demonstrated that aging primary neurons are more vulnerable to glutamate-induced excitotoxicity, and that co-treatment with the mood stabilizers lithium and valproic acid (VPA) induces synergistic neuroprotective effects. This study sought to identify molecule(s) involved in these synergistic effects. We found that FGF-21 mRNA was selectively and markedly elevated by co-treatment with lithium and VPA in primary rat brain neurons. FGF-21 protein levels were also robustly increased in neuronal lysates and culture medium following lithium-VPA co-treatment. Combining glycogen synthase kinase-3 (GSK-3) inhibitors with VPA or histone deacetylase (HDAC) inhibitors with lithium synergistically increased FGF-21 mRNA levels, supporting that synergistic effects of lithium and VPA are mediated via GSK-3 and HDAC inhibition, respectively. Exogenous FGF-21 protein completely protected aging neurons from glutamate challenge. This neuroprotection was associated with enhanced Akt-1 activation and GSK-3 inhibition. Lithium-VPA co-treatment markedly prolonged lithium-induced Akt-1 activation and augmented GSK-3 inhibition. Akt-1 knockdown markedly decreased FGF-21 mRNA levels and reduced the neuroprotection induced by FGF-21 or lithium-VPA co-treatment. In addition, FGF-21 knockdown reduced lithium-VPA co-treatment-induced Akt-1 activation and neuroprotection against excitotoxicity. Together, our novel results suggest that FGF-21 is a key mediator of the effects of these mood stabilizers and a potential new therapeutic target for CNS disorders.
Yoon, Ju-Heon; Yoon, Kwan-Hee; Jeong, Jeung-hyun [Solar Cell Research Center, Korea Institute of Science and Technology, 39-1, Seoul 136-791 (Korea, Republic of); Kim, Won Mok; Park, Jong-Keuk; Baik, Young-Joon [Electronic Materials Research Center, Korea Institute of Science and Technology, 39-1, Seoul 136-791 (Korea, Republic of); Seong, Tae-Yeon, E-mail: jhjeong@kist.re.kr [Department of Materials Science and Engineering, College of Engineering, Korea University, Seoul 136-701 (Korea, Republic of)
2011-10-26
The thermal stability of Mo thin films is indispensable to Cu(In,Ga)Se{sub 2} (CIGS) solar cells: CIGS films are deposited above 500 deg. C. The thermal stabilities of Mo thin films with dense to porous Mo microstructures, which are varied by controlling the sputtering pressure, are investigated. Interface failures are found to occur in buckling mode in denser Mo films, whereas cracking arises in less dense films. The failure modes are apparently dependent on the sign of the residual stress: the former is due to compressive stress, whereas the latter is due to tensile stress. Interestingly, the softening of soda-lime glass at high temperatures reconfigures the film stresses to be more compressive after annealing, which in turn triggers buckling even in films that are tensile-stressed in the as-deposited states. We conclude that the appropriate processing conditions for thermally stable back contacts cannot be obtained with the simple single layer approach. On the basis of this relationship between microstructure, residual stress and the failure modes, it is shown that improvements in film adhesion can widen the processing window for the preparation of robust back contacts, i.e. with a conventional bilayer approach and substrate roughening. Since the bilayer approach employed more compliant porous structures in the bottom layer, back contacts that are better suited to higher stress and temperature can be produced. Furthermore, substrate roughening might make the back contact more conductive as well as more stable because adhesion can be enhanced without the use of an electrically resistive buffer layer.
Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N
2015-01-01
Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg(2+) ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, (27)Al/(29)Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2(nd) law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.
Hátylas Azevedo; Carlos Alberto Moreira-Filho
2015-01-01
Biological networks display high robustness against random failures but are vulnerable to targeted attacks on central nodes. Thus, network topology analysis represents a powerful tool for investigating network susceptibility against targeted node removal. Here, we built protein interaction networks associated with chemoresistance to temozolomide, an alkylating agent used in glioma therapy, and analyzed their modular structure and robustness against intentional attack. These networks showed fu...
CASCADED FUNZZY SYSTEM AND ITS ROBUST ANALYSIS BASED ON SYLLOGISTIC FUZZY REASONING
Wang Shitong; Korris F. L. Chung
2004-01-01
Syllogistic fuzzy reasoning is introduced into fizzy system, and the new Cascaded Fuzzy System(CFS) is presented. The thoroughly theoretical analysis and experimental results show that syllogistic fuzzy reasoning is more robust than all other implication inferences for noise data and that CFS has better robustness than conventional fuzzy systems, which provide the solid foundation for CFS's potential application in fuzzy control and modeling and so on.
Reliability Analysis of High Rockfill Dam Stability
Ping Yi
2015-01-01
Full Text Available A program 3DSTAB combining slope stability analysis and reliability analysis is developed and validated. In this program, the limit equilibrium method is utilized to calculate safety factors of critical slip surfaces. The first-order reliability method is used to compute reliability indexes corresponding to critical probabilistic surfaces. When derivatives of the performance function are calculated by finite difference method, the previous iteration’s critical slip surface is saved and used. This sequential approximation strategy notably improves efficiency. Using this program, the stability reliability analyses of concrete faced rockfill dams and earth core rockfill dams with different heights and different slope ratios are performed. The results show that both safety factors and reliability indexes decrease as the dam’s slope increases at a constant height and as the dam’s height increases at a constant slope. They decrease dramatically as the dam height increases from 100 m to 200 m while they decrease slowly once the dam height exceeds 250 m, which deserves attention. Additionally, both safety factors and reliability indexes of the upstream slope of earth core rockfill dams are higher than that of the downstream slope. Thus, the downstream slope stability is the key failure mode for earth core rockfill dams.
Robust analysis of guidance performance against weaving targets
Weiss, M.
2008-01-01
Traditionally performance analysis of guidance loops against weaving targets is performed by assuming that the acceleration of the target is sinusoidal (barrel-S maneuver) or, in any case, periodic with a fixed period. Either by direct simulation, or by using the Adjoint Method, it is easy to comput
Robustness of Multiple Objective Decision Analysis Preference Functions
2002-06-01
1995. Jia, Jianmin, and James S. Dyer. “Risk Value Theory.” Risk-Value Study Series Working Paper No. 3, August 1994. Johnson, Edgar M., and...Analysis." Cambridge University Press, 1990. Morin , R. A., and A. F. Suarez. “Risk Aversion Revisited,” Journal of Finance: 1201-1216 (September
Zhenhua Zhou
2015-01-01
Full Text Available This paper is concerned with the problem of designing robust H-infinity output feedback controller and resilient filtering for a class of discrete-time singular piecewise-affine systems with input saturation and state constraints. Based on a singular piecewise Lyapunov function combined with S-procedure and some matrix inequality convexifying techniques, the H-infinity stabilization condition is established and the resilient H-infinity filtering error dynamic system is investigated, and, meanwhile, the domain of attraction is well estimated. Under energy bounded disturbance, the input saturation disturbance tolerance condition is proposed; then, the resilient H-infinity filter is designed in some restricted region. It is shown that the controller gains and filter design parameters can be obtained by solving a family of LMIs parameterized by one or two scalar variables. Meanwhile, by using the corresponding optimization methods, the domain of attraction and the disturbance tolerance level is maximized, and the H-infinity performance γ is minimized. Numerical examples are given to illustrate the effectiveness of the proposed design methods.
Kick Stability Analysis of the LHC Inflectors
Ducimetière, L; Schröder, G; Vossenberg, Eugène B; Barnes, M J; Wait, G D
1996-01-01
Two sets of four LHC inflector magnet systems must produce a kick of 1.36 Tm each with a duration of 6.5 µs, a rise time of 750 ns, and an overall stability of ± 0.5%. The electrical circuit of the complete system, including all known stray quantities, has been simulated with PSpice. Many stray elements were determined from Opera2D simulations which included eddy-currents. 3D analyses have also been carried out for the kicker magnet using the electromagnetic analysis code Opera3D. Equivalent circuits which simulate the frequency dependence of inductance and resistance of the Pulse Forming Network (PFN) have been derived. The dimensions of the PFN coil have been selected to give the correct pulse response. The end cells of the PFN have also been optimised. The discharge stability of various PFN capacitors has been measured. This paper presents the results of both the analyses and measurements.
Reliability Analysis of Dynamic Stability in Waves
Søborg, Anders Veldt
2004-01-01
exhibit sufficient characteristics with respect to slope at zero heel (GM value), maximum leverarm, positive range of stability and area below the leverarm curve. The rule-based requirements to calm water leverarm curves are entirely based on experience obtained from vessels in operation and recorded......-4 per ship year such brute force Monte-Carlo simulations are not always feasible due to the required computational resources. Previous studies of dynamic stability of ships in waves typically focused on the capsizing event. In this study the objective is to establish a procedure that can identify...... the distribution of the exceedance probability may be established by an estimation of the out-crossing rate of the "safe set" defined by the utility function. This out-crossing rate will be established using the so-called Madsen's Formula. A bi-product of this analysis is a set of short wave time series...
Novel DTA method for thermal stability analysis
Berty, J.M.; Gandhi, R.J.; Lee, S.
1986-01-01
A Differential Thermal Analysis (DTA) technique to study the kinetics of highly exothermic reactions for estimating thermal stability parameters has been developed. The technique involves measuring and analyzing the heat generated due to the reaction from a differential temperature curve. The technique has been tested by studying the kinetics of the reaction between sodium thiosulfate and hydrogen peroxide whose kinetic parameters are already known and whose thermal stability has been analyzed by a different technique. First the envisiones experiment was simulated on computer, then the DTA experimental equipment was designed on the basis of the computer simulation and finally the actual reaction between Na/sub 2/S/sub 2/O/sub 4/ and H/sub 2/O was performed. The satisfactory results demonstrated the feasibility of the DTA technique for estimating the kinetic parameters.
On robust kalman filtering with using wavelet analysis
Lobach, V. I.
2013-01-01
One presents a nonlinear filtering algorithm that propagates the entire condi- tional probability density functions. These functions are recursively computed in efficient manner using the discrete wavelet transform. With the multiresolution analysis we can speed up the computation by ignoring the high-frequency details of the probability density function up to a certain level. The level of the wavelet decomposition can be determined at each time step adaptively.
吴敏; 何勇; 佘锦华
2005-01-01
This paper concerns problem of the delay-dependent robust stability and stabilization for uncertain neutral systems. Some new delay-dependent stability criteria are derived by taking matrices are given to express the relationship between the terms in the Leibniz-Newton formula and the new criteria are based on linear matrix inequalities such that the free weighting matrices can be easily obtained. Moreover, the stability criteria are also used to design the state-feedback controller.Numerical examples demonstrates that the proposed criteria are effective and are an improvement over the previous papers.
Stability Analysis and Stabilization of Miduk Heap Leaching Structure, Iran
Mehdi Amini
2013-06-01
Full Text Available To construct copper heap leaching structures, a stepped heap of ore is placed over an isolated sloping surface and then washed with sulphuric acid. The isolated bed of such a heap consists of some natural and geosynthetic layers. Shear strength parameters between these layers are low, so they form the possible sliding surfaces of the heaps. Economic and environmental considerations call for studying such slides. In this study, firstly, results of the laboratory tests carried on the materials of the heap leaching structures bed are presented. Then, the instability mechanisms of such structures are investigated and proper approaches are summarized for their stabilization. Finally, stability of the Miduk copper heap is evaluated as a case history, and appropriate approaches and their effects are discussed for its stabilization.
Denoising and robust non-linear wavelet analysis
Bruce, Andrew G.; Donoho, David L.; Gao, Hong-Ye; Martin, R. D.
1994-04-01
In a series of papers, Donoho and Johnstone develop a powerful theory based on wavelets for extracting non-smooth signals from noisy data. Several nonlinear smoothing algorithms are presented which provide high performance for removing Gaussian noise from a wide range of spatially inhomogeneous signals. However, like other methods based on the linear wavelet transform, these algorithms are very sensitive to certain types of non-Gaussian noise, such as outliers. In this paper, we develop outlier resistance wavelet transforms. In these transforms, outliers and outlier patches are localized to just a few scales. By using the outlier resistant wavelet transforms, we improve upon the Donoho and Johnstone nonlinear signal extraction methods. The outlier resistant wavelet algorithms are included with the S+Wavelets object-oriented toolkit for wavelet analysis.
Robust decision analysis for environmental management of groundwater contamination sites
Vesselinov, Velimir V; Katzman, Danny
2013-01-01
In contrast to many other engineering fields, the uncertainties in subsurface processes (e.g., fluid flow and contaminant transport in aquifers) and their parameters are notoriously difficult to observe, measure, and characterize. This causes severe uncertainties that need to be addressed in any decision analysis related to optimal management and remediation of groundwater contamination sites. Furthermore, decision analyses typically rely heavily on complex data analyses and/or model predictions, which are often poorly constrained as well. Recently, we have developed a model-driven decision-support framework (called MADS; http://mads.lanl.gov) for the management and remediation of subsurface contamination sites in which severe uncertainties and complex physics-based models are coupled to perform scientifically defensible decision analyses. The decision analyses are based on Information Gap Decision Theory (IGDT). We demonstrate the MADS capabilities by solving a decision problem related to optimal monitoring ...
Design of Launch Vehicle Flight Control Systems Using Ascent Vehicle Stability Analysis Tool
Jang, Jiann-Woei; Alaniz, Abran; Hall, Robert; Bedossian, Nazareth; Hall, Charles; Jackson, Mark
2011-01-01
A launch vehicle represents a complicated flex-body structural environment for flight control system design. The Ascent-vehicle Stability Analysis Tool (ASAT) is developed to address the complicity in design and analysis of a launch vehicle. The design objective for the flight control system of a launch vehicle is to best follow guidance commands while robustly maintaining system stability. A constrained optimization approach takes the advantage of modern computational control techniques to simultaneously design multiple control systems in compliance with required design specs. "Tower Clearance" and "Load Relief" designs have been achieved for liftoff and max dynamic pressure flight regions, respectively, in the presence of large wind disturbances. The robustness of the flight control system designs has been verified in the frequency domain Monte Carlo analysis using ASAT.
Stability analysis of rubblemound breakwater using ANN
Mandal, S.; Rao, S.; Manjunath, Y.R.; Kim, D.H.
are of rubble mound type which consists of one or two layers of heavier armor stones, one or two filter layers consisting of relatively smaller stones and a core of quarry run. The design of the breakwater section, which is normally of a trapezoidal shape... relation is not clear. In more practical terms networks are non-linear modeling tools and they can be used to model complex relationship between input and output system. Earlier applications of neural networks for stability analysis of rubble mound...
Stability analysis of cylindrical Vlasov equilibria
Short, R.W.
1979-01-01
A general method of stability analysis is described which may be applied to a large class of such problems, namely those which are described dynamically by the Vlasov equation, and geometrically by cylindrical symmetry. The method is presented for the simple case of the Vlasov-Poisson (electrostatic) equations, and the results are applied to a calculation of the lower-hybrid-drift instability in a plasma with a rigid rotor distribution function. The method is extended to the full Vlasov-Maxwell (electromagnetic) equations. These results are applied to a calculation of the instability of the extraordinary electromagnetic mode in a relativistic E-layer interacting with a background plasma.
Stability and Sensitivity Analysis of Fuzzy Control Systems. Mechatronics Applications
Radu-Emil Precup; Stefan Preitl
2006-01-01
The development of fuzzy control systems is usually performed by heuristicmeans, incorporating human skills, the drawback being in the lack of general-purposedevelopment methods. A major problem, which follows from this development, is theanalysis of the structural properties of the control system, such as stability, controllabilityand robustness. Here comes the first goal of the paper, to present a stability analysismethod dedicated to fuzzy control systems with mechatronics applications bas...
Stability analysis of liver cancer-related microRNAs
Yan Li; Zhenggang Jiang; Lijian Xu; Hu Yao; Jiangfeng Guo; Xianfeng Ding
2011-01-01
MicroRNAs(miRNAs)are non-coding,single-stranded RNAs of ～22 nt and constitute a novel class of gene regulators that are found in both plants and animals.Several studies have demonstrated that serum miRNAs could serve as potential biomarkers for the detection of various cancers and other diseases.A few documents regarding the stability of liver cancer-related miRNAs in serum are available.A systemic analysis of the stability of miRNA in serum is quite necessary.The purpose of this study was to evaluate the stability of miRNAs from three different sources,cultured liver cancer Huh-7 cell line,clinical liver cancer,and serum under different experimental conditions,including different temperature,time duration,pH values,Rnase A digestion,Dnase Ⅰ digestion,and various freeze-thaw cycles.The qRT-PCR analysis demonstrated that liver cancer-related miRNAs were detectable under each of test conditions,indicating that miRNAs were extremely stable and resistant to destruction and degradation under harsh environmental conditions.However,ribosomal RNA was fragile and easily degraded by demonstrating sharp decrease of relative expression under the non-physiological test conditions.We also established a robust procedure for serum RNA extraction,which is greatly important not only for the miRNA profiling studies bat also for the disease prognosis based on abnormal miRNA expression.
Robustness Analysis of the IFN-γ Induced JAK-STAT Signaling Pathway
Zhi-Ke Zi; Zhi-Rong Sun
2005-01-01
Here, the issue of robustness analysis of cell JAK-STAT signal transduction networks is addressed. This is investigated upon a mathematical model of IFN-γ induced JAK-STAT signaling pathway by applying robustness analysis which is based on a broad range of simultaneous and systematical parameters variation. The effects of the variations of the initial signal proteins' concentrations on the output of this system are also studied. The study demonstrates that the JAK-STAT signaling pathway is robust with respect to its "signal time" and "signal duration", but sensitive with respect to its "signal amplitude". These analysis results can point to experimental designs that can further test how the pathway activity can be perturbed.
Model and Stability Analysis of a Flexible Bladed Rotor
2006-01-01
Full Text Available This paper presents a fully bladed flexible rotor and outlines the associated stability analysis. From an energetic approach based on the complete energies and potentials for Euler-Bernoulli beams, a system of equations is derived, in the rotational frame, for the rotor. This later one is made of a hollow shaft modelled by an Euler-Bernoulli beam supported by a set of bearings. It is connected to a rigid disk having a rotational inertia. A full set of flexible blades is also modelled by Euler-Bernoulli beams clamped in the disk. The flexural vibrations of the blades as well as those of the shaft are considered. The evolution of the eigenvalues of this rotor, in the corotational frame, is studied. A stability detection method, bringing coalescence and loci separation phenomena to the fore, in case of an asymmetric rotor, is undertaken in order to determine a parametric domain where turbomachinery cannot encounter damage. Finally, extensive parametric studies including the length and the stagger angle of the blades as well as their flexibility are presented in order to obtain robust criteria for stable and unstable areas prediction.
Dynamic Analysis of Power System Voltage Stability.
Gebreselassie, Assefa
This thesis investigates the effects of loads and voltage regulators on the dynamic voltage stability of power systems. The analysis focuses on the interactions of machine flux dynamics with loads and voltage control devices. The results are based on eigenvalue analysis of the linearized models and time simulation of the nonlinear models, using models from the Power System Toolbox, a Matlab -based package for the simulation and small signal analysis of nonlinear power systems. The voltage stability analysis results are developed using a single machine single load system with typical machine and network parameters and the NPCC 10-machine system. Dynamic models for generators, exciters and loads are used. The generator is modeled with a pair of poles and one damper circuit in both the d-axis and the q-axis. Saturation effects are included in the model. The IEEE Type DC1 DC commutator exciter model is used for all the exciters. Five different types of loads: constant impedance, constant current, constant power, a first order induction motor model (slip model) and a third order induction motor model (slip-flux model) are considered. The modes of instability and the stability limits of the different representation of loads are examined for two different operating modes of the exciters. The first, when all the exciters are on automatic control and the second when some exciters are on manual control. Modal participation factors are used to determine the characteristics of the critical modes. The characteristics of the unstable modes are verified by performing time simulation of the nonlinear models. Oscillatory and non-oscillatory instabilities are experienced by load buses when all the exciters are on automatic control and some exciters are on manual control respectively, for loads which are predominantly constant power and induction motors. It is concluded that the mode of instability does not depend on the type of loads but on the operating condition of the exciters
The beauty of simple adaptive control and new developments in nonlinear systems stability analysis
Barkana, Itzhak
2014-12-01
Although various adaptive control techniques have been around for a long time and in spite of successful proofs of stability and even successful demonstrations of performance, the eventual use of adaptive control methodologies in practical real world systems has met a rather strong resistance from practitioners and has remained limited. Apparently, it is difficult to guarantee or even understand the conditions that can guarantee stable operations of adaptive control systems under realistic operational environments. Besides, it is difficult to measure the robustness of adaptive control system stability and allow it to be compared with the common and widely used measure of phase margin and gain margin that is utilized by present, mainly LTI, controllers. Furthermore, customary stability analysis methods seem to imply that the mere stability of adaptive systems may be adversely affected by any tiny deviation from the pretty idealistic and assumably required stability conditions. This paper first revisits the fundamental qualities of customary direct adaptive control methodologies, in particular the classical Model Reference Adaptive Control, and shows that some of their basic drawbacks have been addressed and eliminated within the so-called Simple Adaptive Control methodology. Moreover, recent developments in the stability analysis methods of nonlinear systems show that prior conditions that were customarily assumed to be needed for stability are only apparent and can be eliminated. As a result, sufficient conditions that guarantee stability are clearly stated and lead to similarly clear proofs of stability. As many real-world applications show, once robust stability of the adaptive systems can be guaranteed, the added value of using Add-On Adaptive Control along with classical Control design techniques is pushing the desired performance beyond any previous limits.
The beauty of simple adaptive control and new developments in nonlinear systems stability analysis
Barkana, Itzhak, E-mail: ibarkana@gmail.com [BARKANA Consulting, Ramat Hasharon (Israel)
2014-12-10
Although various adaptive control techniques have been around for a long time and in spite of successful proofs of stability and even successful demonstrations of performance, the eventual use of adaptive control methodologies in practical real world systems has met a rather strong resistance from practitioners and has remained limited. Apparently, it is difficult to guarantee or even understand the conditions that can guarantee stable operations of adaptive control systems under realistic operational environments. Besides, it is difficult to measure the robustness of adaptive control system stability and allow it to be compared with the common and widely used measure of phase margin and gain margin that is utilized by present, mainly LTI, controllers. Furthermore, customary stability analysis methods seem to imply that the mere stability of adaptive systems may be adversely affected by any tiny deviation from the pretty idealistic and assumably required stability conditions. This paper first revisits the fundamental qualities of customary direct adaptive control methodologies, in particular the classical Model Reference Adaptive Control, and shows that some of their basic drawbacks have been addressed and eliminated within the so-called Simple Adaptive Control methodology. Moreover, recent developments in the stability analysis methods of nonlinear systems show that prior conditions that were customarily assumed to be needed for stability are only apparent and can be eliminated. As a result, sufficient conditions that guarantee stability are clearly stated and lead to similarly clear proofs of stability. As many real-world applications show, once robust stability of the adaptive systems can be guaranteed, the added value of using Add-On Adaptive Control along with classical Control design techniques is pushing the desired performance beyond any previous limits.
A non-local method for robustness analysis of floating point programs
Ivan Gazeau
2012-07-01
Full Text Available Robustness is a standard correctness property which intuitively means that if the input to the program changes less than a fixed small amount then the output changes only slightly. This notion is useful in the analysis of rounding error for floating point programs because it helps to establish bounds on output errors introduced by both measurement errors and by floating point computation. Compositional methods often do not work since key constructs—like the conditional and the while-loop—are not robust. We propose a method for proving the robustness of a while-loop. This method is non-local in the sense that instead of breaking the analysis down to single lines of code, it checks certain global properties of its structure. We show the applicability of our method on two standard algorithms: the CORDIC computation of the cosine and Dijkstra's shortest path algorithm.
A non-local method for robustness analysis of floating point programs
Gazeau, Ivan; Palamidessi, Catuscia
2012-01-01
Robustness is a standard correctness property which intuitively means that if the input to the program changes less than a fixed small amount then the output changes only slightly. This notion is useful in the analysis of rounding error for floating point programs because it helps to establish bounds on output errors introduced by both measurement errors and by floating point computation. Compositional methods often do not work since key constructs---like the conditional and the while-loop---are not robust. We propose a method for proving the robustness of a while-loop. This method is non-local in the sense that instead of breaking the analysis down to single lines of code, it checks certain global properties of its structure. We show the applicability of our method on two standard algorithms: the CORDIC computation of the cosine and Dijkstra's shortest path algorithm.
YOGESH K BICHPURIYA; S A SOMAN; A SUBRAMANYAM
2016-10-01
We present an empirical analysis to show that combination of short term load forecasts leads to better accuracy. We also discuss other aspects of combination, i.e.,distribution of weights, effect of variation in the historical window and distribution of forecast errors. The distribution of forecast errors is analyzed in order to get a robust forecast. We define a robust forecaster as one which has consistency in forecast accuracy, lesser shocks (outliers) and lower standard deviation in the distribution of forecast errors. We propose a composite ranking (CRank) scheme based on a composite score which considers three performance measures—standard deviation, kurtosis of distribution of forecast errors and accuracy of forecasts. The CRank helps in identification of a robust forecasts given a choice of individual and combined forecaster. The empirical analysis has been done with the real life data sets of two distribution companies in India.
Experiments with ROPAR, an approach for probabilistic analysis of the optimal solutions' robustness
Marquez, Oscar; Solomatine, Dimitri
2016-04-01
Robust optimization is defined as the search for solutions and performance results which remain reasonably unchanged when exposed to uncertain conditions such as natural variability in input variables, parameter drifts during operation time, model sensitivities and others [1]. In the present study we follow the approach named ROPAR (multi-objective robust optimization allowing for explicit analysis of robustness (see online publication [2]). Its main idea is in: a) sampling the vectors of uncertain factors; b) solving MOO problem for each of them obtaining multiple Pareto sets; c) analysing the statistical properties (distributions) of the subsets of these Pareto sets corresponding to different conditions (e.g. based on constraints formulated for the objective functions values of other system variables); d) selecting the robust solutions. The paper presents the results of experiments with the two case studies: 1) a benchmark function ZDT1 (with an uncertain factor) often used in algorithms comparisons, and 2) a problem of drainage network rehabilitation that uses SWMM hydrodynamic model (the rainfall is assumed to be an uncertain factor). This study is partly supported by the FP7 European Project WeSenseIt Citizen Water Observatory (www.http://wesenseit.eu/) and the CONACYT (Mexico's National Council of Science and Technology) supporting the PhD study of the first author. References [1] H.G.Beyer and B. Sendhoff. "Robust optimization - A comprehensive survey." Comput. Methods Appl. Mech. Engrg., 2007: 3190-3218. [2] D.P. Solomatine (2012). An approach to multi-objective robust optimization allowing for explicit analysis of robustness (ROPAR). UNESCO-IHE. Online publication. Web: https://www.unesco-ihe.org/sites/default/files/solomatine-ropar.pdf
Nakach, Mostafa; Authelin, Jean-René; Voignier, Cecile; Tadros, Tharwat; Galet, Laurence; Chamayou, Alain
2016-06-15
The small particle size of nano-crystalline suspensions can be responsible for their physical instability during drug product preparation (downstream processing), storage and administration. For that purpose, the commercial formulation needs to be sufficiently robust to various triggering conditions, such as ionic strength, shear rate, wetting/dispersing agent desorption by dilution, temperature and pH variation. In our previous work we described a systematic approach to select the suitable wetting/dispersant agent for the stabilization of nano-crystalline suspension. In this paper, we described the assessment of the formulation robustness (stabilized using a mixture of sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) and) by measuring the rate of perikinetic (diffusion-controlled) and orthokinetic (shear-induced) aggregation as a function of ionic strength, temperature, pH and dilution. The results showed that, using the SDS/PVP system, the critical coagulation concentration is about five times higher than that observed in the literature for suspension colloidaly stable at high concentration. The nano-suspension was also found to be very stable at ambient temperature and at different pH conditions. Desorption test confirmed the high affinity between API and wetting/dispersing agent. However, the suspension undergoes aggregation at high temperature due to the desorption of the wetting/dispersing agent and disaggregation of SDS micelles. Furthermore, aggregation occurs at very high shear rate (orhokinetic aggregation) by overcoming the energy barrier responsible for colloidal stability of the system.
Robust Optimal Design of a Nonlinear Dynamic Vibration Absorber Combining Sensitivity Analysis
R.A. Borges
2010-01-01
Full Text Available Dynamic vibration absorbers are discrete devices developed in the beginning of the last century used to attenuate the vibrations of different engineering structures. They have been used in several engineering applications, such as ships, power lines, aeronautic structures, civil engineering constructions subjected to seismic induced excitations, compressor systems, etc. However, in the context of nonlinear dynamics, few works have been proposed regarding the robust optimal design of nonlinear dynamic vibration absorbers. In this paper, a robust optimization strategy combined with sensitivity analysis of systems incorporating nonlinear dynamic vibration absorbers is proposed. Although sensitivity analysis is a well known numerical technique, the main contribution intended for this study is its extension to nonlinear systems. Due to the numerical procedure used to solve the nonlinear equations, the sensitivities addressed herein are computed from the first-order finite-difference approximations. With the aim of increasing the efficiency of the nonlinear dynamic absorber into a frequency band of interest, and to augment the robustness of the optimal design, a robust optimization strategy combined with the previous sensitivities is addressed. After presenting the underlying theoretical foundations, the proposed robust design methodology is performed for a two degree-of-freedom system incorporating a nonlinear dynamic vibration absorber. Based on the obtained results, the usefulness of the proposed methodology is highlighted.
Truck Roll Stability Data Collection and Analysis
Stevens, SS
2001-07-02
The principal objective of this project was to collect and analyze vehicle and highway data that are relevant to the problem of truck rollover crashes, and in particular to the subset of rollover crashes that are caused by the driver error of entering a curve at a speed too great to allow safe completion of the turn. The data are of two sorts--vehicle dynamic performance data, and highway geometry data as revealed by vehicle behavior in normal driving. Vehicle dynamic performance data are relevant because the roll stability of a tractor trailer depends both on inherent physical characteristics of the vehicle and on the weight and distribution of the particular cargo that is being carried. Highway geometric data are relevant because the set of crashes of primary interest to this study are caused by lateral acceleration demand in a curve that exceeds the instantaneous roll stability of the vehicle. An analysis of data quality requires an evaluation of the equipment used to collect the data because the reliability and accuracy of both the equipment and the data could profoundly affect the safety of the driver and other highway users. Therefore, a concomitant objective was an evaluation of the performance of the set of data-collection equipment on the truck and trailer. The objective concerning evaluation of the equipment was accomplished, but the results were not entirely positive. Significant engineering apparently remains to be done before a reliable system can be fielded. Problems were identified with the trailer to tractor fiber optic connector used for this test. In an over-the-road environment, the communication between the trailer instrumentation and the tractor must be dependable. In addition, the computer in the truck must be able to withstand the rigors of the road. The major objective--data collection and analysis--was also accomplished. Using data collected by instruments on the truck, a ''bad-curve'' database can be generated. Using
Sun, Yeong-Jeu; Wu, Yu-Biaw; Wang, Ching-Cheng
2013-06-01
In this study, the concept of global exponential ε-stabilization is introduced and the robust stabilization for a class of nonlinear systems with single input is investigated. Based on Lyapunov-like Theorem with differential and integral inequalities, a feedback control is proposed to realize the global stabilization of such nonlinear systems with any pre-specified exponential convergence rate. The guaranteed exponential convergence rate can be also correctly estimated. This result can be straightforwardly applicable to some famous chaotic systems. Besides, it will be proven that a single and linear control, with lower dimensions than that of the states, can realize the global exponential stability of some famous chaotic systems. Finally, comparisons of our main results with recently published results as well as numerical examples with circuit realization are provided to show the effectiveness and superiority of the obtained results.
Robust Mokken Scale Analysis by Means of the Forward Search Algorithm for Outlier Detection
Zijlstra, Wobbe P.; van der Ark, L. Andries; Sijtsma, Klaas
2011-01-01
Exploratory Mokken scale analysis (MSA) is a popular method for identifying scales from larger sets of items. As with any statistical method, in MSA the presence of outliers in the data may result in biased results and wrong conclusions. The forward search algorithm is a robust diagnostic method for outlier detection, which we adapt here to…
Robustness studies in covariance structure modeling - An overview and a meta-analysis
Boomsma, A
1998-01-01
In covariance structure modeling, several estimation methods are available. The robustness of an estimator against specific violations of assumptions can be determined empirically by means of a Monte Carlo study. Many such studies in covariance structure analysis have been published, but the conclus
Self-Organized Robust Principal Component Analysis by Back-Propagation Learning
樋口, 勇夫
2004-01-01
The purpose of this study is the suggestion of a self-organized back-propagation algorithm for robust principal component analysis. The self-organizing algorithm that discriminates the influence of data automatically is applied to learning of a sandglass type neural network.
Robustness studies in covariance structure modeling - An overview and a meta-analysis
Boomsma, A
1998-01-01
In covariance structure modeling, several estimation methods are available. The robustness of an estimator against specific violations of assumptions can be determined empirically by means of a Monte Carlo study. Many such studies in covariance structure analysis have been published, but the conclus
Robustness studies in covariance structure modeling - An overview and a meta-analysis
Boomsma, A
In covariance structure modeling, several estimation methods are available. The robustness of an estimator against specific violations of assumptions can be determined empirically by means of a Monte Carlo study. Many such studies in covariance structure analysis have been published, but the
Global stability analysis of axisymmetric boundary layers
Vinod, N
2016-01-01
This paper presents the linear global stability analysis of the incompressible axisymmetric boundary layer on a circular cylinder. The base flow is parallel to the axis of the cylinder at inlet. The pressure gradient is zero in the streamwise direction. The base flow velocity profile is fully non-parallel and non-similar in nature. The boundary layer grows continuously in the spatial directions. Linearized Navier-Stokes(LNS) equations are derived for the disturbance flow quantities in the cylindrical polar coordinates. The LNS equations along with homogeneous boundary conditions forms a generalized eigenvalues problem. Since the base flow is axisymmetric, the disturbances are periodic in azimuthal direction. Chebyshev spectral collocation method and Arnoldi's iterative algorithm is used for the solution of the general eigenvalues problem. The global temporal modes are computed for the range of Reynolds numbers and different azimuthal wave numbers. The largest imaginary part of the computed eigenmodes are nega...
STABILITY ANALYSIS OF RIVERBANK SUBJECT TO SEEPAGE
Yan LU; Yongjun LU; Xingnong ZHANG
2007-01-01
The stability of riverbanks subject to seepage is studied experimentally and theoretically in this paper. By including seepage in a 3-dimensional theoretical analysis, the study first shows how the critical slope or angle of repose of a cohesionless material is related to the ratio of the hydraulic gradient of seepage to its critical value under the fluidization condition. The critical stable slope is shown to be related to not only the hydraulic gradient but also the seepage direction. Measured laboratory data reasonably fit well with the theoretical relationship for the case of injection and suction. The data reveal that the slope is reduced with injection and increased with suction, respectively. Additionally, the study identifies the seepage direction which results in a minimum critical stable slope for a certain hydraulic gradient of seepage.
Haddad, Wassim M.; Bernstein, Dennis S.
1991-01-01
Lyapunov function proofs of sufficient conditions for asymptotic stability are given for feedback interconnections of bounded real and positive real transfer functions. Two cases are considered: (1) a proper bounded real (resp., positive real) transfer function with a bounded real (resp., positive real) time-varying memoryless nonlinearity; and (2) two strictly proper bounded real (resp., positive real) transfer functions. A similar treatment is given for the circle and Popov theorems. Application of these results to robust stability with time-varying bounded real, positive real, and sector-bounded uncertainty is discussed.
Haddad, Wassim M.; Bernstein, Dennis S.
1991-01-01
Lyapunov function proofs of sufficient conditions for asymptotic stability are given for feedback interconnections of bounded real and positive real transfer functions. Two cases are considered: (1) a proper bounded real (resp., positive real) transfer function with a bounded real (resp., positive real) time-varying memoryless nonlinearity; and (2) two strictly proper bounded real (resp., positive real) transfer functions. A similar treatment is given for the circle and Popov theorems. Application of these results to robust stability with time-varying bounded real, positive real, and sector-bounded uncertainty is discussed.
Efficient and robust analysis of complex scattering data under noise in microwave resonators
Probst, S.; Song, F. B.; Bushev, P. A.; Ustinov, A. V.; Weides, M.
2015-02-01
Superconducting microwave resonators are reliable circuits widely used for detection and as test devices for material research. A reliable determination of their external and internal quality factors is crucial for many modern applications, which either require fast measurements or operate in the single photon regime with small signal to noise ratios. Here, we use the circle fit technique with diameter correction and provide a step by step guide for implementing an algorithm for robust fitting and calibration of complex resonator scattering data in the presence of noise. The speedup and robustness of the analysis are achieved by employing an algebraic rather than an iterative fit technique for the resonance circle.
Efficient and robust analysis of complex scattering data under noise in microwave resonators
Probst, S., E-mail: sebastian.probst@kit.edu [Physikalisches Institut, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Song, F. B. [Physikalisches Institut, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); The 10th Institute of Chinese Electronic Technology Corporation, Chengdu 610036 (China); Bushev, P. A. [Experimentalphysik, Universität des Saarlandes, D-66123 Saarbrücken (Germany); Ustinov, A. V. [Physikalisches Institut, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Laboratory of Superconducting Metamaterials, National University of Science and Technology “MISIS,” Moscow 119049 (Russian Federation); Weides, M. [Physikalisches Institut, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz (Germany)
2015-02-15
Superconducting microwave resonators are reliable circuits widely used for detection and as test devices for material research. A reliable determination of their external and internal quality factors is crucial for many modern applications, which either require fast measurements or operate in the single photon regime with small signal to noise ratios. Here, we use the circle fit technique with diameter correction and provide a step by step guide for implementing an algorithm for robust fitting and calibration of complex resonator scattering data in the presence of noise. The speedup and robustness of the analysis are achieved by employing an algebraic rather than an iterative fit technique for the resonance circle.
Developing Uncertainty Models for Robust Flutter Analysis Using Ground Vibration Test Data
Potter, Starr; Lind, Rick; Kehoe, Michael W. (Technical Monitor)
2001-01-01
A ground vibration test can be used to obtain information about structural dynamics that is important for flutter analysis. Traditionally, this information#such as natural frequencies of modes#is used to update analytical models used to predict flutter speeds. The ground vibration test can also be used to obtain uncertainty models, such as natural frequencies and their associated variations, that can update analytical models for the purpose of predicting robust flutter speeds. Analyzing test data using the -norm, rather than the traditional 2-norm, is shown to lead to a minimum-size uncertainty description and, consequently, a least-conservative robust flutter speed. This approach is demonstrated using ground vibration test data for the Aerostructures Test Wing. Different norms are used to formulate uncertainty models and their associated robust flutter speeds to evaluate which norm is least conservative.
田俊康; 钟守铭; 熊良林
2008-01-01
This paper deals with delay-dependent robust stability of neutral Lurie control systems with multiple nonlinearities and time-varying structured uncertainties. The Lyapunov functional method is used. By adding some appropriate zero terms to the deviation of V and constructing some linear matrix inequalities, some sufficient conditions for the delay-dependent absolute stability and robust stability are derived. Finally, a numerical example is presented to illustrate the effectiveness of the method.
FUZZY STABILITY ANALYSIS OF MODE COUPLING CHATTER ON CUTTING PROCESS
1998-01-01
The influence of fuzzy uncertainty factors is considered on the analysis of chatter occurring during machine tool cutting process. Using fuzzy mathematics analysis methods, a detailed discussion over fuzzy stability analysis problems is presented related to the mode coupling chatter with respect to intrinsic structure fuzzy factors, and the possibility distribution of the fuzzy stability cutting range and the confidence level expressions of the fuzzy stability cutting width are given.
ANALYSIS AND OPTIMISATION OF DYNAMIC STABILITY OF MOBILE WORKING MACHINES
Peter BIGOŠ
2014-09-01
Full Text Available This paper describes an investigation of the dynamic stability, which is specified for the mobile working machines. There are presented the basic theoretical principles of the stability theory together with an introduction of two illustrative examples of the dynamic stability analysis.
Importance of criteria weights in composite appraisal of transport projects – a robustness analysis
Jensen, Anders Vestergaard
2010-01-01
This paper presents a framework for estimating the robustness of appraisal of transport projects using composite appraisal methodology which makes use of both cost benefit analysis (CBA) and multi criteria analysis (MCA). The setting of criteria weights in MCA is often seen as the most subjective...... part of the analysis and is frequently a subject for discussion. The examined methodology makes use of importance order for setting the criteria weights; thereby only a ranking of the criteria after importance is required from the involved decision makers or stakeholders. In some cases the setting...... of criteria weights can make a big difference in the resulting assessment of alternatives. It is concluded that it is highly relevant to examine the criteria weights for estimating the robustness of the assessment....
Dependent component analysis based approach to robust demarcation of skin tumors
Kopriva, Ivica; Peršin, Antun; Puizina-Ivić, Neira; Mirić, Lina
2009-02-01
Method for robust demarcation of the basal cell carcinoma (BCC) is presented employing novel dependent component analysis (DCA)-based approach to unsupervised segmentation of the red-green-blue (RGB) fluorescent image of the BCC. It exploits spectral diversity between the BCC and the surrounding tissue. DCA represents an extension of the independent component analysis (ICA) and is necessary to account for statistical dependence induced by spectral similarity between the BCC and surrounding tissue. Robustness to intensity fluctuation is due to the scale invariance property of DCA algorithms. By comparative performance analysis with state-of-the-art image segmentation methods such as active contours (level set), K-means clustering, non-negative matrix factorization and ICA we experimentally demonstrate good performance of DCA-based BCC demarcation in demanding scenario where intensity of the fluorescent image has been varied almost two-orders of magnitude.
Stability Analysis and Design for Nonlinear Singular Systems
Yang, Chunyu; Zhou, Linna
2013-01-01
Singular systems which are also referred to as descriptor systems, semi-state systems, differential- algebraic systems or generalized state-space systems have attracted much attention because of their extensive applications in the Leontief dynamic model, electrical and mechanical models, etc. This monograph presented up-to-date research developments and references on stability analysis and design of nonlinear singular systems. It investigated the problems of practical stability, strongly absolute stability, input-state stability and observer design for nonlinear singular systems and the problems of absolute stability and multi-objective control for nonlinear singularly perturbed systems by using Lyapunov stability theory, comparison principle, S-procedure and linear matrix inequality (LMI), etc. Practical stability, being quite different from stability in the sense of Lyapunov, is a significant performance specification from an engineering point of view. The basic concepts and results on practical stability f...
Stability analysis and stabilization of networked linear systems with random packet losses
XIE LiHua
2009-01-01
This paper Is concerned with the stability analysis and stabilization of networked discrete-time and sampled-data linear systems with random packet losses.Asymptotic stability,mean-square stability,and stochastic stability are considered.For networked discrete-time linear systems,the packet loss period is assumed to be a finite-state Markov chain.We establish that the mean-square stability of a related discrete-time system which evolves in random time Implies the mean-square stability of the system in deterministic time by using the equivalence of stability properties of Markovian jump linear systems in random time.We also establish the equivalence of asymptotic stability for the systems in deterministic discrete time and in random time.For networked sampled-data systems,a binary Markov chain Is used to characterize the packet loss phenomenon of the network.In this case,the packet loss period between two transmission instants is driven by an identically Independently distributed sequence assuming any positive values.Two approaches,namely the Markov jump linear system approach and randomly sampled system approach,are introduced.Based on the stability results derived,we present methods for stabilization of networked sampled-data systems in terms of matrix inequalities.Numerical examples are given to Illustrate the design methods of stabilizing controllers.
Transient Stability Analysis Using Transmission Line Measurement
蔡国伟; 程浩忠; 陈家荣; 王承民
2004-01-01
The novel quantitative assessment method using transmission line measurement was developed. A new style of stability criterion was suggested which is based on the line measurement. The stability indices for lines,cutsets and power system according to features of transient energy in the lines were given, which not only provide a reliable and accurate assessment of the transient stability of power system, but also can be used to assess the effect of lines and cutsets on the transient stability and identify the weak transmission segment. Examples were presented by simulation on the IEEE-39 buses test system.
Remarks on boiling water reactor stability analysis. Pt. 2. Stability monitoring
Lange, Carsten; Hennig, Dieter; Hurtado, Antonio [Technische Univ. Dresden (Germany). Chair of Hydrogen and Nuclear Energy; Schuster, Roland [Kernkraftwerk Brunsbuettel GmbH und Co. oHG, Brunsbuettel (Germany); Lukas, Bernard [EnBW Kernkraft GmbH, Philippsburg (Germany). Kernkraftwerk Philippsburg; Aguirre, Carlos [Kernkraftwerk Leibstadt AG, Aargau (Switzerland)
2012-12-15
In part 1 of this article we explained the partly relative complex solution manifold of the differential equations describing the stability behaviour of a BWR, in particular the coexistence of different types of solutions, such as the coexistence of unstable limit cycles and stable fixed points are of interest from the operational safety point of view. The part 2 is devoted to the surveillance of the stability behaviour. We summarize some stability monitoring methods and suggest to support stability tests by RAM-ROM analyses in order to reveal in advance the stability 'landscape' of the BWR in a parameter region high sensitive for appearing of linear unstable states. The analysis of an especial stability test, performed at NPP Leibstadt (KKL), makes it clear that the measurement results can only be interpreted by application of bifurcation analysis. (orig.)
Labyrinth Seal Flutter Analysis and Test Validation in Support of Robust Rocket Engine Design
El-Aini, Yehia; Park, John; Frady, Greg; Nesman, Tom
2010-01-01
High energy-density turbomachines, like the SSME turbopumps, utilize labyrinth seals, also referred to as knife-edge seals, to control leakage flow. The pressure drop for such seals is order of magnitude higher than comparable jet engine seals. This is aggravated by the requirement of tight clearances resulting in possible unfavorable fluid-structure interaction of the seal system (seal flutter). To demonstrate these characteristics, a benchmark case of a High Pressure Oxygen Turbopump (HPOTP) outlet Labyrinth seal was studied in detail. First, an analytical assessment of the seal stability was conducted using a Pratt & Whitney legacy seal flutter code. Sensitivity parameters including pressure drop, rotor-to-stator running clearances and cavity volumes were examined and modeling strategies established. Second, a concurrent experimental investigation was undertaken to validate the stability of the seal at the equivalent operating conditions of the pump. Actual pump hardware was used to construct the test rig, also referred to as the (Flutter Rig). The flutter rig did not include rotational effects or temperature. However, the use of Hydrogen gas at high inlet pressure provided good representation of the critical parameters affecting flutter especially the speed of sound. The flutter code predictions showed consistent trends in good agreement with the experimental data. The rig test program produced a stability threshold empirical parameter that separated operation with and without flutter. This empirical parameter was used to establish the seal build clearances to avoid flutter while providing the required cooling flow metering. The calibrated flutter code along with the empirical flutter parameter was used to redesign the baseline seal resulting in a flutter-free robust configuration. Provisions for incorporation of mechanical damping devices were introduced in the redesigned seal to ensure added robustness
On the relation between flexibility analysis and robust optimization for linear systems
Zhang, Qi
2016-03-05
Flexibility analysis and robust optimization are two approaches to solving optimization problems under uncertainty that share some fundamental concepts, such as the use of polyhedral uncertainty sets and the worst-case approach to guarantee feasibility. The connection between these two approaches has not been sufficiently acknowledged and examined in the literature. In this context, the contributions of this work are fourfold: (1) a comparison between flexibility analysis and robust optimization from a historical perspective is presented; (2) for linear systems, new formulations for the three classical flexibility analysis problems—flexibility test, flexibility index, and design under uncertainty—based on duality theory and the affinely adjustable robust optimization (AARO) approach are proposed; (3) the AARO approach is shown to be generally more restrictive such that it may lead to overly conservative solutions; (4) numerical examples show the improved computational performance from the proposed formulations compared to the traditional flexibility analysis models. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3109–3123, 2016
Stochastic stabilization analysis of networked control systems
Ma Changlin; Fang Huajing
2007-01-01
Considering the stochastic delay problems existing in networked control systems, a new control mode is proposed for networked control systems whose delay is longer than a sampling period. Under the control mode, the mathematical model of such a system is established. A stochastic stabilization condition for the system is given. The maximum delay can be derived from the stabilization condition.
M. J. P. Mens
2015-01-01
Full Text Available Droughts will likely become more frequent, of greater magnitude and of longer duration in the future due to climate change. Already in the present climate, a variety of drought events may occur with different exceedance frequencies. These frequencies are becoming more uncertain due to climate change. Many methods in support of drought risk management focus on providing insight into changing drought frequencies, and use water supply reliability as key decision criterion. In contrast, robustness analysis focuses on providing insight into the full range of drought events and their impact on a system's functioning. This method has been developed for flood risk systems, but applications on drought risk systems are lacking. This paper aims to develop robustness analysis for drought risk systems, and illustrates the approach through a case study with a water supply reservoir and its users. We explore drought characterization and the assessment of a system's ability to deal with drought events, by quantifying the severity and socio-economic impact of a variety of drought events, both frequent and rare ones. Furthermore, we show the effect of three common drought management strategies (increasing supply, reducing demand and implementing hedging rules on the robustness of the coupled water supply and socio-economic system. The case is inspired by Oologah Lake, a multipurpose reservoir in Oklahoma, United States. Results demonstrate that although demand reduction and supply increase may have a comparable effect on the supply reliability, demand reduction may be preferred from a robustness perspective. To prepare drought management plans for dealing with current and future droughts, it is thus recommended to test how alternative drought strategies contribute to a system's robustness rather than relying solely on water reliability as the decision criterion.
Reliability Analysis of Dynamic Stability in Waves
Søborg, Anders Veldt
2004-01-01
exhibit sufficient characteristics with respect to slope at zero heel (GM value), maximum leverarm, positive range of stability and area below the leverarm curve. The rule-based requirements to calm water leverarm curves are entirely based on experience obtained from vessels in operation and recorded......The assessment of a ship's intact stability is traditionally based on a semi-empirical deterministic concept that evaluates the characteristics of ship's calm water restoring leverarm curves. Today the ship is considered safe with respect to dynamic stability if its calm water leverarm curves...... accidents in the past. The rules therefore only leaves little room for evaluation and improvement of safety of a ship's dynamic stability. A few studies have evaluated the probability of ship stability loss in waves using Monte Carlo simulations. However, since this probability may be in the order of 10...
Vaseem, Mohammad; McKerricher, Garret; Shamim, Atif
2016-01-13
Currently, silver-nanoparticle-based inkjet ink is commercially available. This type of ink has several serious problems such as a complex synthesis protocol, high cost, high sintering temperatures (∼200 °C), particle aggregation, nozzle clogging, poor shelf life, and jetting instability. For the emerging field of printed electronics, these shortcomings in conductive inks are barriers for their widespread use in practical applications. Formulating particle-free silver inks has potential to solve these issues and requires careful design of the silver complexation. The ink complex must meet various requirements, such as in situ reduction, optimum viscosity, storage and jetting stability, smooth uniform sintered films, excellent adhesion, and high conductivity. This study presents a robust formulation of silver-organo-complex (SOC) ink, where complexing molecules act as reducing agents. The 17 wt % silver loaded ink was printed and sintered on a wide range of substrates with uniform surface morphology and excellent adhesion. The jetting stability was monitored for 5 months to confirm that the ink was robust and highly stable with consistent jetting performance. Radio frequency inductors, which are highly sensitive to metal quality, were demonstrated as a proof of concept on flexible PEN substrate. This is a major step toward producing high-quality electronic components with a robust inkjet printing process.
Vaseem, Mohammad
2015-12-29
Currently, silver-nanoparticle-based inkjet ink is commercially available. This type of ink has several serious problems such as a complex synthesis protocol, high cost, high sintering temperatures (∼200 °C), particle aggregation, nozzle clogging, poor shelf life, and jetting instability. For the emerging field of printed electronics, these shortcomings in conductive inks are barriers for their widespread use in practical applications. Formulating particle-free silver inks has potential to solve these issues and requires careful design of the silver complexation. The ink complex must meet various requirements, such as in situ reduction, optimum viscosity, storage and jetting stability, smooth uniform sintered films, excellent adhesion, and high conductivity. This study presents a robust formulation of silver–organo-complex (SOC) ink, where complexing molecules act as reducing agents. The 17 wt % silver loaded ink was printed and sintered on a wide range of substrates with uniform surface morphology and excellent adhesion. The jetting stability was monitored for 5 months to confirm that the ink was robust and highly stable with consistent jetting performance. Radio frequency inductors, which are highly sensitive to metal quality, were demonstrated as a proof of concept on flexible PEN substrate. This is a major step toward producing high-quality electronic components with a robust inkjet printing process.
Keller, Brad M; Oustimov, Andrew; Wang, Yan; Chen, Jinbo; Acciavatti, Raymond J; Zheng, Yuanjie; Ray, Shonket; Gee, James C; Maidment, Andrew D A; Kontos, Despina
2015-04-01
An analytical framework is presented for evaluating the equivalence of parenchymal texture features across different full-field digital mammography (FFDM) systems using a physical breast phantom. Phantom images (FOR PROCESSING) are acquired from three FFDM systems using their automated exposure control setting. A panel of texture features, including gray-level histogram, co-occurrence, run length, and structural descriptors, are extracted. To identify features that are robust across imaging systems, a series of equivalence tests are performed on the feature distributions, in which the extent of their intersystem variation is compared to their intrasystem variation via the Hodges-Lehmann test statistic. Overall, histogram and structural features tend to be most robust across all systems, and certain features, such as edge enhancement, tend to be more robust to intergenerational differences between detectors of a single vendor than to intervendor differences. Texture features extracted from larger regions of interest (i.e., [Formula: see text]) and with a larger offset length (i.e., [Formula: see text]), when applicable, also appear to be more robust across imaging systems. This framework and observations from our experiments may benefit applications utilizing mammographic texture analysis on images acquired in multivendor settings, such as in multicenter studies of computer-aided detection and breast cancer risk assessment.
Lee, J. J.
2016-01-01
Full Text Available Here we provide a description of the IRT estimation method known as Normal Ogive Harmonic Analysis Robust Method (NOHARM. Although in some ways this method has been superseded by new computer programs that also adopt a specifically factor-analytic approach, its fundamental principles remain useful in certain applications, which include calculating the residual covariance matrix and rescaling the distribution of the common factor (latent trait. These principles can be applied to parameter estimates obtained by any method.
Robust Feature Detection and Local Classification for Surfaces Based on Moment Analysis
2004-01-01
The stable local classification of discrete surfaces with respect to features such as edges and corners or concave and convex regions, respectively, is as quite difficult as well as indispensable for many surface processing applications. Usually, the feature detection is done via a local curvature analysis. If concerned with large triangular and irregular grids, e.g., generated via a marching cube algorithm, the detectors are tedious to treat and a robust classification is hard to achieve. He...
Robust Analysis of the Joint Strike Fighter Integrated Training Center Pilot Scheduling
2011-09-01
models weather using Markov chains and a weather resource, since weather conditions for consecutive events are not independent (Dummar, 2011). He...justification for procurement or as an explanation for bottlenecks in the system. The ITC model is a discrete-event, first-in first-out, queuing -based...Unfortunately, queuing theory tells us that this will likely bias the results (Ross, 2007). In robust analysis, the intent is to look at the effect of
Azevedo, Hátylas; Moreira-Filho, Carlos Alberto
2015-11-01
Biological networks display high robustness against random failures but are vulnerable to targeted attacks on central nodes. Thus, network topology analysis represents a powerful tool for investigating network susceptibility against targeted node removal. Here, we built protein interaction networks associated with chemoresistance to temozolomide, an alkylating agent used in glioma therapy, and analyzed their modular structure and robustness against intentional attack. These networks showed functional modules related to DNA repair, immunity, apoptosis, cell stress, proliferation and migration. Subsequently, network vulnerability was assessed by means of centrality-based attacks based on the removal of node fractions in descending orders of degree, betweenness, or the product of degree and betweenness. This analysis revealed that removing nodes with high degree and high betweenness was more effective in altering networks’ robustness parameters, suggesting that their corresponding proteins may be particularly relevant to target temozolomide resistance. In silico data was used for validation and confirmed that central nodes are more relevant for altering proliferation rates in temozolomide-resistant glioma cell lines and for predicting survival in glioma patients. Altogether, these results demonstrate how the analysis of network vulnerability to topological attack facilitates target prioritization for overcoming cancer chemoresistance.
Wang, Yonggang, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States); Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Wen, Ting [Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); Park, Changyong; Kenney-Benson, Curtis [High Pressure Collaborative Access Team (HPCAT), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Pravica, Michael; Zhao, Yusheng, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States); Yang, Wenge, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China)
2016-01-14
The structure stability under high pressure and thermal expansion behavior of Na{sub 3}OBr and Na{sub 4}OI{sub 2}, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na{sub 3}OBr and Na{sub 4}OI{sub 2}, respectively. The cubic Na{sub 3}OBr structure and tetragonal Na{sub 4}OI{sub 2} with intergrowth K{sub 2}NiF{sub 4} structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na{sub 4}OI{sub 2} exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20–80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.
Wang, Yonggang; Wen, Ting; Park, Changyong; Kenney-Benson, Curtis; Pravica, Michael; Yang, Wenge; Zhao, Yusheng
2016-01-01
The structure stability under high pressure and thermal expansion behavior of Na3OBr and Na4OI2, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na3OBr and Na4OI2, respectively. The cubic Na3OBr structure and tetragonal Na4OI2 with intergrowth K2NiF4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na4OI2 exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.
Milling Stability Analysis Based on Chebyshev Segmentation
HUANG, Jianwei; LI, He; HAN, Ping; Wen, Bangchun
2016-09-01
Chebyshev segmentation method was used to discretize the time period contained in delay differential equation, then the Newton second-order difference quotient method was used to calculate the cutter motion vector at each time endpoint, and the Floquet theory was used to determine the stability of the milling system after getting the transfer matrix of milling system. Using the above methods, a two degree of freedom milling system stability issues were investigated, and system stability lobe diagrams were got. The results showed that the proposed methods have the following advantages. Firstly, with the same calculation accuracy, the points needed to represent the time period are less by the Chebyshev Segmentation than those of the average segmentation, and the computational efficiency of the Chebyshev Segmentation is higher. Secondly, if the time period is divided into the same parts, the stability lobe diagrams got by Chebyshev segmentation method are more accurate than those of the average segmentation.
Reliability Analysis of Slope Stability by Central Point Method
Li, Chunge; WU Congliang
2015-01-01
Given uncertainty and variability of the slope stability analysis parameter, the paper proceed from the perspective of probability theory and statistics based on the reliability theory. Through the central point method of reliability analysis, performance function about the reliability of slope stability analysis is established. What’s more, the central point method and conventional limit equilibrium methods do comparative analysis by calculation example. The approach’s numerical ...
Baggio, Jacopo A; BurnSilver, Shauna B; Arenas, Alex; Magdanz, James S; Kofinas, Gary P; De Domenico, Manlio
2016-11-29
Network analysis provides a powerful tool to analyze complex influences of social and ecological structures on community and household dynamics. Most network studies of social-ecological systems use simple, undirected, unweighted networks. We analyze multiplex, directed, and weighted networks of subsistence food flows collected in three small indigenous communities in Arctic Alaska potentially facing substantial economic and ecological changes. Our analysis of plausible future scenarios suggests that changes to social relations and key households have greater effects on community robustness than changes to specific wild food resources.
Control design and robustness analysis of a ball and plate system by using polynomial chaos
Colón, Diego [University of São Paulo, Polytechnic School, LAC -PTC, São Paulo (Brazil); Balthazar, José M. [São Paulo State University - Rio Claro Campus, Rio Claro (Brazil); Reis, Célia A. dos [São Paulo State University - Bauru Campus, Bauru (Brazil); Bueno, Átila M.; Diniz, Ivando S. [São Paulo State University - Sorocaba Campus, Sorocaba (Brazil); Rosa, Suelia de S. R. F. [University of Brasilia, Brasilia (Brazil)
2014-12-10
In this paper, we present a mathematical model of a ball and plate system, a control law and analyze its robustness properties by using the polynomial chaos method. The ball rolls without slipping. There is an auxiliary robot vision system that determines the bodies' positions and velocities, and is used for control purposes. The actuators are to orthogonal DC motors, that changes the plate's angles with the ground. The model is a extension of the ball and beam system and is highly nonlinear. The system is decoupled in two independent equations for coordinates x and y. Finally, the resulting nonlinear closed loop systems are analyzed by the polynomial chaos methodology, which considers that some system parameters are random variables, and generates statistical data that can be used in the robustness analysis.
Control design and robustness analysis of a ball and plate system by using polynomial chaos
Colón, Diego; Balthazar, José M.; dos Reis, Célia A.; Bueno, Átila M.; Diniz, Ivando S.; de S. R. F. Rosa, Suelia
2014-12-01
In this paper, we present a mathematical model of a ball and plate system, a control law and analyze its robustness properties by using the polynomial chaos method. The ball rolls without slipping. There is an auxiliary robot vision system that determines the bodies' positions and velocities, and is used for control purposes. The actuators are to orthogonal DC motors, that changes the plate's angles with the ground. The model is a extension of the ball and beam system and is highly nonlinear. The system is decoupled in two independent equations for coordinates x and y. Finally, the resulting nonlinear closed loop systems are analyzed by the polynomial chaos methodology, which considers that some system parameters are random variables, and generates statistical data that can be used in the robustness analysis.
Robustness analysis of the Zhang neural network for online time-varying quadratic optimization
Zhang Yunong; Ruan Gongqin; Li Kene; Yang Yiwen, E-mail: zhynong@mail.sysu.edu.c, E-mail: ynzhang@ieee.or [School of Information Science and Technology, Sun Yat-Sen University, Guangzhou 510006 (China)
2010-06-18
A general type of recurrent neural network (termed as Zhang neural network, ZNN) has recently been proposed by Zhang et al for the online solution of time-varying quadratic-minimization (QM) and quadratic-programming (QP) problems. Global exponential convergence of the ZNN could be achieved theoretically in an ideal error-free situation. In this paper, with the normal differentiation and dynamics-implementation errors considered, the robustness properties of the ZNN model are investigated for solving these time-varying problems. In addition, linear activation functions and power-sigmoid activation functions could be applied to such a perturbed ZNN model. Both theoretical-analysis and computer-simulation results demonstrate the good ZNN robustness and superior performance for online time-varying QM and QP problem solving, especially when using power-sigmoid activation functions.
Robust passivity analysis for discrete-time recurrent neural networks with mixed delays
Huang, Chuan-Kuei; Shu, Yu-Jeng; Chang, Koan-Yuh; Shou, Ho-Nien; Lu, Chien-Yu
2015-02-01
This article considers the robust passivity analysis for a class of discrete-time recurrent neural networks (DRNNs) with mixed time-delays and uncertain parameters. The mixed time-delays that consist of both the discrete time-varying and distributed time-delays in a given range are presented, and the uncertain parameters are norm-bounded. The activation functions are assumed to be globally Lipschitz continuous. Based on new bounding technique and appropriate type of Lyapunov functional, a sufficient condition is investigated to guarantee the existence of the desired robust passivity condition for the DRNNs, which can be derived in terms of a family of linear matrix inequality (LMI). Some free-weighting matrices are introduced to reduce the conservatism of the criterion by using the bounding technique. A numerical example is given to illustrate the effectiveness and applicability.
Random Access Broadcast: Stability and Throughput Analysis
Shrader, Brooke
2007-01-01
A wireless network in which packets are broadcast to a group of receivers through use of a random access protocol is considered in this work. The relation to previous work on networks of interacting queues is discussed and subsequently, the stability and throughput regions of the system are analyzed and presented. A simple network of two source nodes and two destination nodes is considered first. The broadcast service process is analyzed assuming a channel that allows for packet capture and multipacket reception. In this small network, the stability and throughput regions are observed to coincide. The same problem for a network with N sources and M destinations is considered next. The channel model is simplified in that multipacket reception is no longer permitted. Bounds on the stability region are developed using the concept of stability rank and the throughput region of the system is compared to the bounds. Our results show that as the number of destination nodes increases, the stability and throughput reg...
Stability analysis of spacecraft power systems
Halpin, S. M.; Grigsby, L. L.; Sheble, G. B.; Nelms, R. M.
1990-01-01
The problems in applying standard electric utility models, analyses, and algorithms to the study of the stability of spacecraft power conditioning and distribution systems are discussed. Both single-phase and three-phase systems are considered. Of particular concern are the load and generator models that are used in terrestrial power system studies, as well as the standard assumptions of load and topological balance that lead to the use of the positive sequence network. The standard assumptions regarding relative speeds of subsystem dynamic responses that are made in the classical transient stability algorithm, which forms the backbone of utility-based studies, are examined. The applicability of these assumptions to a spacecraft power system stability study is discussed in detail. In addition to the classical indirect method, the applicability of Liapunov's direct methods to the stability determination of spacecraft power systems is discussed. It is pointed out that while the proposed method uses a solution process similar to the classical algorithm, the models used for the sources, loads, and networks are, in general, more accurate. Some preliminary results are given for a linear-graph, state-variable-based modeling approach to the study of the stability of space-based power distribution networks.
Further Result on Robust Stabilization for Uncertain Nonlinear Time-delay Systems%不确定非线性时滞系统鲁棒镇定化研究
焦晓红; 申铁龙; 孙元章
2007-01-01
The systematic recursive design method of the robust stabilizing controller for general uncertain nonlinear time-delay systems is investigated in this paper. A delay-independent state feedback control law can be obtained by recursively constructing Lyapunov-Razumikhin function. It is shown that by some design techniques the obstacle that is intrinsic to the application of the Razumikhin condition can be removed such that the design of the robust stabilizing control law is free of any restriction for the systems.
Developing robust recurrence plot analysis techniques for investigating infant respiratory patterns.
Terrill, Philip I; Wilson, Stephen; Suresh, Sadasivam; Cooper, David M
2007-01-01
Recurrence plot analysis is a useful non-linear analysis tool. There are still no well formalised procedures for carrying out this analysis on measured physiological data, and systemising analysis is often difficult. In this paper, the recurrence based embedding is compared to radius based embedding by studying a logistic attractor and measured breathing data collected from sleeping human infants. Recurrence based embedding appears to be a more robust method of carrying out a recurrence analysis when attractor size is likely to be different between datasets. In the infant breathing data, the radius measure calculated at a fixed recurrence, scaled by average respiratory period, allows the accurate discrimination of active sleep from quiet sleep states (AUC=0.975, Sn=098, Sp=0.94).
Linear stability analysis of supersonic axisymmetric jets
Zhenhua Wan
2014-01-01
Full Text Available Stabilities of supersonic jets are examined with different velocities, momentum thicknesses, and core temperatures. Amplification rates of instability waves at inlet are evaluated by linear stability theory (LST. It is found that increased velocity and core temperature would increase amplification rates substantially and such influence varies for different azimuthal wavenumbers. The most unstable modes in thin momentum thickness cases usually have higher frequencies and azimuthal wavenumbers. Mode switching is observed for low azimuthal wavenumbers, but it appears merely in high velocity cases. In addition, the results provided by linear parabolized stability equations show that the mean-flow divergence affects the spatial evolution of instability waves greatly. The most amplified instability waves globally are sometimes found to be different from that given by LST.
Stability analysis of automobile driver steering control
Allen, R. W.
1981-01-01
In steering an automobile, the driver must basically control the direction of the car's trajectory (heading angle) and the lateral deviation of the car relative to a delineated pathway. A previously published linear control model of driver steering behavior which is analyzed from a stability point of view is considered. A simple approximate expression for a stability parameter, phase margin, is derived in terms of various driver and vehicle control parameters, and boundaries for stability are discussed. A field test study is reviewed that includes the measurement of driver steering control parameters. Phase margins derived for a range of vehicle characteristics are found to be generally consistent with known adaptive properties of the human operator. The implications of these results are discussed in terms of driver adaptive behavior.
Liquefaction mathematical analysis for improvement structures stability
Azam Khodashenas Pelko
2010-10-01
Full Text Available The stability of any structure is possible if foundation is appropriately designed. The Bandar abbas is the largest and most important port of Iran, with high seismicity and occurring strong earthquakes in this territory, the soil mechanical properties of different parts of city have been selected as the subject of current research. The data relating to the design of foundation for improvement of structure at different layer of subsoil have been collected and, accordingly, soil mechanical properties have been evaluated. The results of laboratory experiments can be used for evaluation of geotechnical characteristics of urban area for development a region with high level of structural stability. Ultimately, a new method for calculation of liquefaction force is suggested. It is applicable for improving geotechnical and structure codes and also for reanalysis of structure stability of previously constructed buildings.
Stability Analysis for Stochastic Optimization Problems
无
2007-01-01
Stochastic optimization offers a means of considering the objectives and constrains with stochastic parameters. However, it is generally difficult to solve the stochastic optimization problem by employing conventional methods for nonlinear programming when the number of random variables involved is very large. Neural network models and algorithms were applied to solve the stochastic optimization problem on the basis of the stability theory. Stability for stochastic programs was discussed. If random vector sequence converges to the random vector in the original problem in distribution, the optimal value of the corresponding approximation problems converges to the optimal value of the original stochastic optimization problem.
Analysis of feedback loops and robustness in network evolution based on Boolean models
Cho Kwang-Hyun
2007-11-01
Full Text Available Abstract Background Many biological networks such as protein-protein interaction networks, signaling networks, and metabolic networks have topological characteristics of a scale-free degree distribution. Preferential attachment has been considered as the most plausible evolutionary growth model to explain this topological property. Although various studies have been undertaken to investigate the structural characteristics of a network obtained using this growth model, its dynamical characteristics have received relatively less attention. Results In this paper, we focus on the robustness of a network that is acquired during its evolutionary process. Through simulations using Boolean network models, we found that preferential attachment increases the number of coupled feedback loops in the course of network evolution. Whereas, if networks evolve to have more coupled feedback loops rather than following preferential attachment, the resulting networks are more robust than those obtained through preferential attachment, although both of them have similar degree distributions. Conclusion The presented analysis demonstrates that coupled feedback loops may play an important role in network evolution to acquire robustness. The result also provides a hint as to why various biological networks have evolved to contain a number of coupled feedback loops.
Module-based analysis of robustness tradeoffs in the heat shock response system.
Hiroyuki Kurata
2006-07-01
Full Text Available Biological systems have evolved complex regulatory mechanisms, even in situations where much simpler designs seem to be sufficient for generating nominal functionality. Using module-based analysis coupled with rigorous mathematical comparisons, we propose that in analogy to control engineering architectures, the complexity of cellular systems and the presence of hierarchical modular structures can be attributed to the necessity of achieving robustness. We employ the Escherichia coli heat shock response system, a strongly conserved cellular mechanism, as an example to explore the design principles of such modular architectures. In the heat shock response system, the sigma-factor sigma32 is a central regulator that integrates multiple feedforward and feedback modules. Each of these modules provides a different type of robustness with its inherent tradeoffs in terms of transient response and efficiency. We demonstrate how the overall architecture of the system balances such tradeoffs. An extensive mathematical exploration nevertheless points to the existence of an array of alternative strategies for the existing heat shock response that could exhibit similar behavior. We therefore deduce that the evolutionary constraints facing the system might have steered its architecture toward one of many robustly functional solutions.
Keyser, V.
2015-12-01
Philosophers of science discuss how multiple modes of measurement can generate evidence for the existence and character of a phenomenon (Horwich 1982; Hacking 1983; Franklin and Howson 1984; Collins 1985; Sober 1989; Trout 1993; Culp 1995; Keeley 2002; Staley 2004; Weber 2005; Keyser 2012). But how can this work systematically in climate change measurement? Additionally, what conclusions can scientists and policy-makers draw when different modes of measurement fail to be robust by producing contradictory results? First, I present a new technical account of robust measurement (RAMP) that focuses on the physical independence of measurement processes. I detail how physically independent measurement processes "check each other's results." (This account is in contrast to philosophical accounts of robustness analysis that focus on independent model assumptions or independent measurement products or results.) Second, I present a puzzle about contradictory and divergent climate change measures, which has consistently re-emerged in climate measurement. This discussion will focus on land, drilling, troposphere, and computer simulation measures. Third, to systematically solve this climate measurement puzzle, I use RAMP in the context of drought measurement in order to generate a classification of measurement processes. Here, I discuss how multimodal precipitation measures—e.g., measures of precipitation deficit like the Standard Precipitation Index vs. air humidity measures like the Standardized Relative Humidity Index--can help with the classification scheme of climate change measurement processes. Finally, I discuss how this classification of measures can help scientists and policy-makers draw effective conclusions in contradictory multimodal climate change measurement contexts.
High-content analysis to leverage a robust phenotypic profiling approach to vascular modulation.
Isherwood, Beverley J; Walls, Rebecca E; Roberts, Mark E; Houslay, Thomas M; Brave, Sandra R; Barry, Simon T; Carragher, Neil O
2013-12-01
Phenotypic screening seeks to identify substances that modulate phenotypes in a desired manner with the aim of progressing first-in-class agents. Successful campaigns require physiological relevance, robust screening, and an ability to deconvolute perturbed pathways. High-content analysis (HCA) is increasingly used in cell biology and offers one approach to prosecution of phenotypic screens, but challenges exist in exploitation where data generated are high volume and complex. We combine development of an organotypic model with novel HCA tools to map phenotypic responses to pharmacological perturbations. We describe implementation for angiogenesis, a process that has long been a focus for therapeutic intervention but has lacked robust models that recapitulate more completely mechanisms involved. The study used human primary endothelial cells in co-culture with stromal fibroblasts to model multiple aspects of angiogenic signaling: cell interactions, proliferation, migration, and differentiation. Multiple quantitative descriptors were derived from automated microscopy using custom-designed algorithms. Data were extracted using a bespoke informatics platform that integrates processing, statistics, and feature display into a streamlined workflow for building and interrogating fingerprints. Ninety compounds were characterized, defining mode of action by phenotype. Our approach for assessing phenotypic outcomes in complex assay models is robust and capable of supporting a range of phenotypic screens at scale.
An Analysis of the Stability Pact
Uhlig, H.F.H.V.S.; Beetsma, R.M.W.J.
1997-01-01
We analyse the proposed "Stability Pact" for countries joining a European Monetary Union (EMU). In an EMU shortsighted governments fail to fully internalise the inflationary consequences of their debt policies. This results in excessive debt accumulation. Therefore, while in the absence of EMU gover
Robust Control of Collaborative Manipulators - Flexible Object System
Balasubramanian Esakki
2013-05-01
stability analysis is performed for both subsystems. Focusing on two three‐link manipulators holding a flexible beam, simulations are performed and simulation results demonstrate the versatility of the proposed robust composite control scheme.
Assessment of Stability of Craniofacial Implants by Resonant Frequency Analysis.
Ivanjac, Filip; Konstantinović, Vitomir S; Lazić, Vojkan; Dordević, Igor; Ihde, Stefan
2016-03-01
Implant stability is a principal precondition for the success of implant therapy. Extraoral implants (EO) are mainly used for anchoring of maxillofacial epithesis. However, assessment of implant stability is mostly based on principles derived from oral implants. The aim of this study was to investigate clinical stability of EO craniofacial disk implants (single, double, and triple) by resonance frequency analysis at different stages of the bone's healing. Twenty patients with orbital (11), nasal (5), and auricular (4) defects with 50 EO implants placed for epithesis anchorage were included. Implant stability was measured 3 times; after implant placement, at 3 months and at least after 6 months. A significant increase in implant stability values was noted between all of the measurements, except for triple-disk implants between third and sixth months, and screw implants between 0 and third months. Disk implants showed lower implant stability quotient (ISQ) values compared with screw implants. Triple-disk implants showed better stability compared with single and double-disk implants. Based on resonance frequency analysis values, disk implants could be safely loaded when their ISQ values are 38 (single disks), 47 (double disks), and 48 (triple disks). According to resonance frequency analysis, disk implant stability increased over time, which showed good osseointegration and increasing mineralization. Although EO screw implants showed higher ISQ values than disk implants, disk-type implants can be safely loaded even if lower values of stability are measured.
Contribution to stability analysis of nonlinear control systems
varc Ivan
2003-12-01
Full Text Available The Popov criterion for the stability of nonlinear control systems is considered. The Popov criterion gives sufficient conditions for stability of nonlinear systems in the frequency domain. It has a direct graphical interpretation and is convenient for both design and analysis. In the article presented, a table of transfer functions of linear parts of nonlinear systems is constructed. The table includes frequency response functions and offers solutions to the stability of the given systems. The table makes a direct stability analysis of selected nonlinear systems possible. The stability analysis is solved analytically and graphically.Then it is easy to find out if the nonlinear system is or is not stable; the task that usually ranks among the difficult task in engineering practice.
Stability analysis of underground engineering based on multidisciplinary design optimization
MA Rong; ZHOU Ke-ping; GAO Feng
2008-01-01
Aiming at characteristics of underground engineering,analyzed the feasibility of Multidisciplinary Design Optimization (MDO) used in underground engineering,and put forward a modularization-based MDO method and the idea of MDO to resolve problems in stability analysis,proving the validity and feasibility of using MDO in underground engineering.Characteristics of uncertainty,complexity and nonlinear become bottle-neck to carry on underground engineering stability analysis by MDO.Therefore,the application of MDO in underground engineering stability analysis is still at a stage of exploration,which need some deep research.
Stability analysis of underground engineering based on multidisciplinary design optimization
MA Rong; ZHOU Ke-ping; GAO Feng
2008-01-01
Aiming at characteristics of underground engineering, analyzed the feasibility of Multidisciplinary Design Optimization (MDO) used in underground engineering, and put forward a modularization-based MDO method and the idea of MDO to resolve problems in stability analysis, proving the validity and feasibility of using MDO in underground engi-neering. Characteristics of uncertainty, complexity and nonlinear become bottle-neck to carry on underground engineering stability analysis by MDO. Therefore, the application of MDO in underground engineering stability analysis is still at a stage of exploration, which need some deep research.
W. Weera
2011-01-01
theory, we derive new delay-dependent stability conditions in terms of linear matrix inequalities (LMIs which can be solved by various available algorithms. Numerical examples are given to demonstrate that the derived conditions are much less conservative than those given in the literature.
LU Qiang; ZHENG ShaoMing; MEI ShengWei; WANG Gang; HUANG QiLi
2008-01-01
On the foundation of nonlinear robust control and exact generator model, this paper presents a design principle of NR-PSS (Nonlinear Robust Power System Stabilizer) for multi-machine power system, based on which an industrial NR-PSS equipment is developed. For popularizing it, the proposed parameter setting method of NR-PSS is completely the same as the widely used parameter adjustment rule of PSS. By virtue of real time digital simulator (RTDS), large disturbance experiments are carried out to compare the performances between generator excitation system equipped with NR-PSS and PSS in order to verify the correctness of design theory. The results show that compared with classical PSS, the proposed NR-PSS can dramatically improve the generator damping and attenuate the oscillation much faster, enhance the generator damping and raise both the small signal and large disturbance transient stability transmission power limit remarkably. The NR-PSS equipment with independent intellectual property right has been successfully put into operation on a 300 MW generator in Baishan Hydro Plant of Northeast China Grid more than 10 months.
Nada S. Abdelwahab
2017-05-01
Full Text Available The present work concerns with the development of stability indicating the RP-HPLC method for simultaneous determination of guaifenesin (GUF and pseudoephedrine hydrochloride (PSH in the presence of guaifenesin related substance (Guaiacol. GUC, and in the presence of syrup excepients with minimum sample pre-treatment. In the developed RP-HPLC method efficient chromatographic separation was achieved for GUF, PSH, GUC and syrup excepients using ODS column as a stationary phase and methanol: water (50:50, v/v, pH = 4 with orthophosphoric acid as a mobile phase with a flow rate of 1 mL min−1 and UV detection at 210 nm. The chromatographic run time was approximately 10 min. Calibration curves were drawn relating the integrated area under peak to the corresponding concentrations of PSH, GUF and GUC in the range of 1–8, 1–20, 0.4–8 μg mL−1, respectively. The developed method has been validated and met the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated method was successfully applied for determination of the studied drugs in triaminic chest congestion® syrup; moreover its results were statistically compared with those obtained by the official method and no significant difference was found between them.
Frosch, Stina; Jørgensen, Bo
2007-01-01
Gas chromatograms of fatty acid methyl esters and of volatile lipid oxidation products from fish lipid extracts are analyzed by multivariate data analysis [principal component analysis (PCA)]. Peak alignment is necessary in order to include all sampled points of the chromatograms in the data set....... The ability of robust algorithms to deal with outlier problems, including both sample-wise and element-wise outliers, and the advantages and drawbacks of two robust PCA methods, robust PCA (ROBPCA) and robust singular value decomposition when analysing these GC data were investigated. The results show...... that the usage of ROPCA is advantageous, compared with traditional PCA, when analysing the entire profile of chromatographic data in cases of sub-optimally aligned data. It also demonstrates how choosing the most robust PCA (sample or element-wise) depends on the type of outliers present in the data set....
Application of modern time series analysis to high stability oscillators
Farrell, B. F.; Mattison, W. M.; Vessot, R. F. C.
1980-01-01
Techniques of modern time series analysis useful for investigating the characteristics of high-stability oscillators and identifying systematic perturbations are discussed with reference to an experiment in which the frequencies of superconducting cavity-stabilized oscillators and hydrogen masers were compared. The techniques examined include transformation to stationarity, autocorrelation and cross-correlation, superresolution, and transfer function determination.
Mathematical modelling and linear stability analysis of laser fusion cutting
Hermanns, Torsten; Schulz, Wolfgang; Vossen, Georg; Thombansen, Ulrich
2016-06-01
A model for laser fusion cutting is presented and investigated by linear stability analysis in order to study the tendency for dynamic behavior and subsequent ripple formation. The result is a so called stability function that describes the correlation of the setting values of the process and the process' amount of dynamic behavior.
The research analysis and application of stability of ventilation system
卢国斌; 陈长华; 葛少成
2002-01-01
The stability of ventilation system includes stabilities of branch, network and main fan. The ventilation system is a dynamic process. The parameters in the ventilation system vary with time. In the paper, a group of mathematical models of quantitative analysis are set up, and the mathematical models are suitable to any ventilation system.
Stability analysis on Jinjia dam hydropower project in Chongqing City
Fuzhi XIE; Hong FENG; Xiaohan YANG; Jingzong YU
2006-01-01
The stability analysis is one of the chief problems at hydropower stations. The Jinjia Hydropower Station is a significant project in Southwest China. The paper adopts the rigidity limited equilibrium theory and evaluated stability of the slope body, which will provide the evidences for further detail design.
Stability Analysis for Class of Switched Nonlinear Systems
Shaker, Hamid Reza; How, Jonathan P.
2010-01-01
Stability analysis for a class of switched nonlinear systems is addressed in this paper. Two linear matrix inequality (LMI) based sufficient conditions for asymptotic stability are proposed for switched nonlinear systems. These conditions are analogous counterparts for switched linear systems which...
Performance and stability analysis of a photovoltaic power system
Merrill, W. C.; Blaha, R. J.; Pickrell, R. L.
1978-01-01
The performance and stability characteristics of a 10 kVA photovoltaic power system are studied using linear Bode analysis and a nonlinear analog simulation. Power conversion efficiencies, system stability, and system transient performance results are given for system operation at various levels of solar insolation. Additionally, system operation and the modeling of system components for the purpose of computer simulation are described.
Stability analysis of interacting queues in the ALOHA system
Rao, Ramesh
The author considers the finite-user, infinite-buffer slotted ALOHA system and analytically extends the known bounds for its stability region. The technique used consists of expressing the stability region in terms of certain status probabilities and then solving for the status probabilities by using results from the analysis of dependent queues and that of Markov chains.
Robust analysis of trends in noisy tokamak confinement data using geodesic least squares regression
Verdoolaege, G.; Shabbir, A.; Hornung, G.
2016-11-01
Regression analysis is a very common activity in fusion science for unveiling trends and parametric dependencies, but it can be a difficult matter. We have recently developed the method of geodesic least squares (GLS) regression that is able to handle errors in all variables, is robust against data outliers and uncertainty in the regression model, and can be used with arbitrary distribution models and regression functions. We here report on first results of application of GLS to estimation of the multi-machine scaling law for the energy confinement time in tokamaks, demonstrating improved consistency of the GLS results compared to standard least squares.
Robust analysis of an underwater navigational strategy in electrically heterogeneous corridors.
Dimble, Kedar D; Ranganathan, Badri N; Keshavan, Jishnu; Humbert, J Sean
2016-08-01
Obstacles and other global stimuli provide relevant navigational cues to a weakly electric fish. In this work, robust analysis of a control strategy based on electrolocation for performing obstacle avoidance in electrically heterogeneous corridors is presented and validated. Static output feedback control is shown to achieve the desired goal of reflexive obstacle avoidance in such environments in simulation and experimentation. The proposed approach is computationally inexpensive and readily implementable on a small scale underwater vehicle, making underwater autonomous navigation feasible in real-time.
A robust penalized method for the analysis of noisy DNA copy number data
Huang Jian
2010-09-01
Full Text Available Abstract Background Deletions and amplifications of the human genomic DNA copy number are the causes of numerous diseases, such as, various forms of cancer. Therefore, the detection of DNA copy number variations (CNV is important in understanding the genetic basis of many diseases. Various techniques and platforms have been developed for genome-wide analysis of DNA copy number, such as, array-based comparative genomic hybridization (aCGH and high-resolution mapping with high-density tiling oligonucleotide arrays. Since complicated biological and experimental processes are often associated with these platforms, data can be potentially contaminated by outliers. Results We propose a penalized LAD regression model with the adaptive fused lasso penalty for detecting CNV. This method contains robust properties and incorporates both the spatial dependence and sparsity of CNV into the analysis. Our simulation studies and real data analysis indicate that the proposed method can correctly detect the numbers and locations of the true breakpoints while appropriately controlling the false positives. Conclusions The proposed method has three advantages for detecting CNV change points: it contains robustness properties; incorporates both spatial dependence and sparsity; and estimates the true values at each marker accurately.
Stability analysis of dielectric elastomer film actuator
LIU YanJu; LIU LiWu; SUN ShouHua; ZHANG Zhen; LENG JinSong
2009-01-01
Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field, due to the electrostatic force between the two electrodes, the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value, the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases, which can be applied to design of actuators. Finally, this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.
Stability analysis of dielectric elastomer film actuator
无
2009-01-01
Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field,due to the electrostatic force between the two electrodes,the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value,the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases,which can be applied to design of actuators. Finally,this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.
Multivariable robust PID control for a PEMFC system
Wang, Fu-Cheng; Ko, Chin-Chun [Department of Mechanical Engineering, National Taiwan University, No. 1 Roosevelt Rd. Sec. 4, Taipei 10617 (China)
2010-10-15
This paper proposes robust proportional-integral-derivative (PID) control for a proton exchange membrane fuel cell (PEMFC) system. We model a PEMFC as a multivariable system, and apply identification techniques to obtain the system's transfer function matrices, where system variations and disturbances are regarded as uncertainties. Because robust control can cope with system uncertainties and disturbances, it has been successfully applied to improve the stability, performance, and efficiency of PEMFC systems in previous studies. However, the resulting robust controllers might be too complicated for hardware implementation. On the other hand, PID control has been widely applicable to engineering practices because of its simple structure, but it lacks stability analysis for systems with uncertainties. Therefore, by combining the merits of robust control and PID control, we design robust PID controllers for the PEMFC system. Based on evaluation of stability, performance, and efficiencies, the proposed robust PID controllers are shown to be effective. (author)
Ozlem Yorulmaz
Full Text Available As is known skewness and outliers are frequently observed in return series, overlooking both concepts during the statistical analysis may cause misleading interpretations. In this paper similar movements of stock markets through the returns of developed and emerging stock markets are recognized and appealing portfolio diversification benefits are identified for investors of USA, UK and Turkey. Different from the previous studies, modified robust principal component analysis which considers skewness and outliers effects was used to investigate the best portfolio diversification. Sixteen stock markets are represented with five components according to findings obtained from analysis. Hence Egyptian, Hungarian, Polish, Thai and Indonesian stock markets provide appealing portfolio diversification opportunities for investors of Turkey. And for the investors of USA and UK, selected emerging markets except Mexican and Turkish offer good diversification benefit.
Long-term performance and stability of molecular shotgun lipidomic analysis of human plasma samples.
Heiskanen, Laura A; Suoniemi, Matti; Ta, Hung Xuan; Tarasov, Kirill; Ekroos, Kim
2013-09-17
The stability of the lipid concentration levels in shotgun lipidomics analysis was tracked over a period of 3.5 years. Concentration levels in several lipid classes, such as phospholipids, were determined in human plasma lipid extracts. Impact of the following factors on the analysis was investigated: sample amount, internal standard amount, and sample dilution factor. Moreover, the reproducibility of lipid profiles obtained in both polarity modes was evaluated. Total number of samples analyzed was approximately 6800 and 7300 samples in negative and positive ion modes, respectively, out of which 610 and 639 instrument control samples were used in stability calculations. The assessed shotgun lipidomics approach showed to be remarkably robust and reproducible, requiring no batch corrections. Coefficients of variation (CVs) of lipid mean concentration measured with optimized analytical parameters were typically less than 15%. The high reproducibility indicated that no lipid degradation occurred during the monitored time period.
ORIGINAL ARTICLE Stability Analysis of Delayed Cournot Model in ...
HP
and Lyapunov method of nonlinear stability analysis are employed. It is ascertained ... MATLAB2012a is used to demonstrate the applicability and accuracy of the results. ...... computation, 149(3), 843-860. ... Science and Complexity, Elsevier.
Huaiqin Wu
2012-01-01
Full Text Available By combing the theories of the switched systems and the interval neural networks, the mathematics model of the switched interval neural networks with discrete and distributed time-varying delays of neural type is presented. A set of the interval parameter uncertainty neural networks with discrete and distributed time-varying delays of neural type are used as the individual subsystem, and an arbitrary switching rule is assumed to coordinate the switching between these networks. By applying the augmented Lyapunov-Krasovskii functional approach and linear matrix inequality (LMI techniques, a delay-dependent criterion is achieved to ensure to such switched interval neural networks to be globally asymptotically robustly stable in terms of LMIs. The unknown gain matrix is determined by solving this delay-dependent LMIs. Finally, an illustrative example is given to demonstrate the validity of the theoretical results.
MA Tao; ZHANG Weigang; ZHANG Yang; TANG Ting
2015-01-01
The current research of complex nonlinear system robust optimization mainly focuses on the features of design parameters, such as probability density functions, boundary conditions, etc. After parameters study, high-dimensional curve or robust control design is used to find an accurate robust solution. However, there may exist complex interaction between parameters and practical engineering system. With the increase of the number of parameters, it is getting hard to determine high-dimensional curves and robust control methods, thus it’s difficult to get the robust design solutions. In this paper, a method of global sensitivity analysis based on divided variables in groups is proposed. By making relevant variables in one group and keeping each other independent among sets of variables, global sensitivity analysis is conducted in grouped variables and the importance of parameters is evaluated by calculating the contribution value of each parameter to the total variance of system response. By ranking the importance of input parameters, relatively important parameters are chosen to conduct robust design analysis of the system. By applying this method to the robust optimization design of a real complex nonlinear system-a vehicle occupant restraint system with multi-parameter, good solution is gained and the response variance of the objective function is reduced to 0.01, which indicates that the robustness of the occupant restraint system is improved in a great degree and the method is effective and valuable for the robust design of complex nonlinear system. This research proposes a new method which can be used to obtain solutions for complex nonlinear system robust design.
Singh, H P; Sukavanam, N
2012-01-01
This paper proposes a new adaptive neural network based control scheme for switched linear systems with parametric uncertainty and external disturbance. A key feature of this scheme is that the prior information of the possible upper bound of the uncertainty is not required. A feedforward neural network is employed to learn this upper bound. The adaptive learning algorithm is derived from Lyapunov stability analysis so that the system response under arbitrary switching laws is guaranteed uniformly ultimately bounded. A comparative simulation study with robust controller given in [Zhang L, Lu Y, Chen Y, Mastorakis NE. Robust uniformly ultimate boundedness control for uncertain switched linear systems. Computers and Mathematics with Applications 2008; 56: 1709-14] is presented.
Stability Analysis of A Neuro-Identification Scheme with Asymptotic Convergence
José A. R. Vargas
2012-07-01
Full Text Available This paper focuses on the stability and convergence analysis of a neuro-identification scheme for uncertain nonlinear systems. Based on linearly parameterized neural networks and the previous knowledge of upper bounds for the approximation error and disturbances, a robust modification of the descent gradient algorithm is proposed to make the overall identification process stable, and, in addition, the on-line residual prediction error asymptotically null, despite the presence of approximation error and disturbances. A simulation study to show the application and comparative performance of the proposed algorithm is presented.
Stability analysis of impulsive functional differential equations
Stamova, Ivanka
2009-01-01
This book is devoted to impulsive functional differential equations which are a natural generalization of impulsive ordinary differential equations (without delay) and of functional differential equations (without impulses). At the present time the qualitative theory of such equationsis under rapid development. After a presentation of the fundamental theory of existence, uniqueness and continuability of solutions, a systematic development of stability theory for that class of problems is given which makes the book unique. It addresses to a wide audience such as mathematicians, applied research
Stability Analysis for Regularized Least Squares Regression
Rudin, Cynthia
2005-01-01
We discuss stability for a class of learning algorithms with respect to noisy labels. The algorithms we consider are for regression, and they involve the minimization of regularized risk functionals, such as L(f) := 1/N sum_i (f(x_i)-y_i)^2+ lambda ||f||_H^2. We shall call the algorithm `stable' if, when y_i is a noisy version of f*(x_i) for some function f* in H, the output of the algorithm converges to f* as the regularization term and noise simultaneously vanish. We consider two flavors of...
Multilayer perceptron for robust nonlinear interval regression analysis using genetic algorithms.
Hu, Yi-Chung
2014-01-01
On the basis of fuzzy regression, computational models in intelligence such as neural networks have the capability to be applied to nonlinear interval regression analysis for dealing with uncertain and imprecise data. When training data are not contaminated by outliers, computational models perform well by including almost all given training data in the data interval. Nevertheless, since training data are often corrupted by outliers, robust learning algorithms employed to resist outliers for interval regression analysis have been an interesting area of research. Several approaches involving computational intelligence are effective for resisting outliers, but the required parameters for these approaches are related to whether the collected data contain outliers or not. Since it seems difficult to prespecify the degree of contamination beforehand, this paper uses multilayer perceptron to construct the robust nonlinear interval regression model using the genetic algorithm. Outliers beyond or beneath the data interval will impose slight effect on the determination of data interval. Simulation results demonstrate that the proposed method performs well for contaminated datasets.
Multilayer Perceptron for Robust Nonlinear Interval Regression Analysis Using Genetic Algorithms
2014-01-01
On the basis of fuzzy regression, computational models in intelligence such as neural networks have the capability to be applied to nonlinear interval regression analysis for dealing with uncertain and imprecise data. When training data are not contaminated by outliers, computational models perform well by including almost all given training data in the data interval. Nevertheless, since training data are often corrupted by outliers, robust learning algorithms employed to resist outliers for interval regression analysis have been an interesting area of research. Several approaches involving computational intelligence are effective for resisting outliers, but the required parameters for these approaches are related to whether the collected data contain outliers or not. Since it seems difficult to prespecify the degree of contamination beforehand, this paper uses multilayer perceptron to construct the robust nonlinear interval regression model using the genetic algorithm. Outliers beyond or beneath the data interval will impose slight effect on the determination of data interval. Simulation results demonstrate that the proposed method performs well for contaminated datasets. PMID:25110755
Robustness Analysis of Integrated LPV-FDI Filters and LTI-FTC System for a Transport Aircraft
Khong, Thuan H.; Shin, Jong-Yeob
2007-01-01
This paper proposes an analysis framework for robustness analysis of a nonlinear dynamics system that can be represented by a polynomial linear parameter varying (PLPV) system with constant bounded uncertainty. The proposed analysis framework contains three key tools: 1) a function substitution method which can convert a nonlinear system in polynomial form into a PLPV system, 2) a matrix-based linear fractional transformation (LFT) modeling approach, which can convert a PLPV system into an LFT system with the delta block that includes key uncertainty and scheduling parameters, 3) micro-analysis, which is a well known robust analysis tool for linear systems. The proposed analysis framework is applied to evaluating the performance of the LPV-fault detection and isolation (FDI) filters of the closed-loop system of a transport aircraft in the presence of unmodeled actuator dynamics and sensor gain uncertainty. The robustness analysis results are compared with nonlinear time simulations.
Liu, Xue; Du, Jing; Shao, Yang; Zhao, Shao-Fan; Yao, Ke-Fu
2017-08-31
Metallic core-shell nanostructures have inspired prominent research interests due to their better performances in catalytic, optical, electric, and magnetic applications as well as the less cost of noble metal than monometallic nanostructures, but limited by the complicated and expensive synthesis approaches. Development of one-pot and inexpensive method for metallic core-shell nanostructures' synthesis is therefore of great significance. A novel Cu network supported nanoporous Ag-Cu alloy with an Ag shell and an Ag-Cu core was successfully synthesized by one-pot chemical dealloying of Zr-Cu-Ag-Al-O amorphous/crystalline composite, which provides a new way to prepare metallic core-shell nanostructures by a simple method. The prepared nanoporous Ag-Cu@Ag core-shell alloy demonstrates excellent air-stability at room temperature and enhanced oxidative stability even compared with other reported Cu@Ag core-shell micro-particles. In addition, the nanoporous Ag-Cu@Ag core-shell alloy also possesses robust antibacterial activity against E. Coli DH5α. The simple and low-cost synthesis method as well as the excellent oxidative stability promises the nanoporous Ag-Cu@Ag core-shell alloy potentially wide applications.
无
2001-01-01
This paper focuses on the H∞ controller design for linear systems with time-varying delays and norm bounded parameter perturbetions in the system state and control/disturbance. On the existence of delayed/undelayed full state feedback controllers, we present a sufficient condition and give a design method in the form of Riccati equation. The controller can not only stabilize the time-delay system, but also make the H∞ norm of the closed-loop system be less than a given bound. This result practically generalizes the related results in current literature.
Campbell, Kieran R.
2016-01-01
Single cell gene expression profiling can be used to quantify transcriptional dynamics in temporal processes, such as cell differentiation, using computational methods to label each cell with a ‘pseudotime’ where true time series experimentation is too difficult to perform. However, owing to the high variability in gene expression between individual cells, there is an inherent uncertainty in the precise temporal ordering of the cells. Pre-existing methods for pseudotime estimation have predominantly given point estimates precluding a rigorous analysis of the implications of uncertainty. We use probabilistic modelling techniques to quantify pseudotime uncertainty and propagate this into downstream differential expression analysis. We demonstrate that reliance on a point estimate of pseudotime can lead to inflated false discovery rates and that probabilistic approaches provide greater robustness and measures of the temporal resolution that can be obtained from pseudotime inference. PMID:27870852
Within-session analysis of the extinction of pavlovian fear-conditioning using robust regression
Vargas-Irwin, Cristina
2010-06-01
Full Text Available Traditionally , the analysis of extinction data in fear conditioning experiments has involved the use of standard linear models, mostly ANOVA of between-group differences of subjects that have undergone different extinction protocols, pharmacological manipulations or some other treatment. Although some studies report individual differences in quantities such as suppression rates or freezing percentages, these differences are not included in the statistical modeling. Withinsubject response patterns are then averaged using coarse-grain time windows which can overlook these individual performance dynamics. Here we illustrate an alternative analytical procedure consisting of 2 steps: the estimation of a trend for within-session data and analysis of group differences in trend as main outcome. This procedure is tested on real fear-conditioning extinction data, comparing trend estimates via Ordinary Least Squares (OLS and robust Least Median of Squares (LMS regression estimates, as well as comparing between-group differences and analyzing mean freezing percentage versus LMS slopes as outcomes
Conjoint Analysis As Robust Measure Leadership Preferences Evidence From The Military Service
Easter B. Belandres
2015-08-01
Full Text Available The study proves that conjoint analysis is a robust measure of preferences as it offers to be a promising technique in determining the leadership preferences in the military service. The process of conjoint analysis in this study employs both qualitative and quantitative methods. The qualitative result shows that the ideal military leadership style in Baguio City and in Benguet is authentic servant transformational and transactional leadership. The findings led to the construction of a data gathering tool for the quantitative method to determine the average importance utility weight that the respondents attach to their preferences on military leadership. Quantitative results reveal that the respondents give a higher degree of importance to military officers who carry out transformational transactional servant and authentic leadership in decreasing order of importance.
Keyong Li; Seong-Cheol Kang; I. Ch. Paschalidis
2007-09-01
This paper investigates stochastic processes that are modeled by a finite number of states but whose transition probabilities are uncertain and possibly time-varying. The treatment of uncertain transition probabilities is important because there appears to be a disconnection between the practice and theory of stochastic processes due to the difficulty of assigning exact probabilities to real-world events. Also, when the finite-state process comes as a reduced model of one that is more complicated in nature (possibly in a continuous state space), existing results do not facilitate rigorous analysis. Two approaches are introduced here. The first focuses on processes with one terminal state and the properties that affect their convergence rates. When a process is on a complicated graph, the bound of the convergence rate is not trivially related to that of the probabilities of individual transitions. Discovering the connection between the two led us to define two concepts which we call 'progressivity' and 'sortedness', and to a new comparison theorem for stochastic processes. An optimality criterion for robust optimal control also derives from this comparison theorem. In addition, this result is applied to the case of mission-oriented autonomous robot control to produce performance estimate within a control framework that we propose. The second approach is in the MDP frame work. We will introduce our preliminary work on optimistic robust optimization, which aims at finding solutions that guarantee the upper bounds of the accumulative discounted cost with prescribed probabilities. The motivation here is to address the issue that the standard robust optimal solution tends to be overly conservative.
Modeling, Stability Analysis and Active Stabilization of Multiple DC-Microgrids Clusters
Shafiee, Qobad; Dragicevic, Tomislav; Vasquez, Juan Carlos
2014-01-01
), and more especially during interconnection with other MGs, creating dc MG clusters. This paper develops a small signal model for dc MGs from the control point of view, in order to study stability analysis and investigate effects of CPLs and line impedances between the MGs on stability of these systems......DC microgrids (MGs), as an alternative option, have attracted increasing interest in recent years due to many potential advantages as compare to the ac system. Stability of these systems can be an important issue under high penetration of load converters which behaves as constant power loads (CPLs....... This model can be also used to synthesis and study dynamics of control loops in dc MGs and also dc MG clusters. An active stabilization method is proposed to be implemented as a dc active power filter (APF) inside the MGs in order to not only increase damping of dc MGs at the presence of CPLs but also...
Jiang, Yanjun; Liu, Xinlong; Chen, Yafei; Zhou, Liya; He, Ying; Ma, Li; Gao, Jing
2014-02-01
A novel catalytic system of Pickering emulsion stabilized by lipase-containing periodic mesoporous organosilica was constructed (named LP@PE) and used as biocatalyst for biodiesel production. The reaction parameters were optimized and the optimum conditions were as follows: the water fraction 0.65%, molar ratio of ethanol to oleic acid 2:1, immobilized lipase particles 150mg, phosphate buffer pH 7.0 and temperature 30°C. Under these conditions, the maximum biodiesel yield obtained via esterification of oleic acid with ethanol could reach 95.8%. The biodiesel yield could maintain 88.6% after LP@PE was used 15times. The LP@PE was also used in the synthesis of biodiesel from Jatropha curcas oil. The highest yield could reach 87.1% and the yield was 73.0% after 10 cycles. All these results demonstrated that Pickering emulsion system stabilized by immobilized enzyme may possess much potential in many enzymatic industrial applications.
Robust gene selection methods using weighting schemes for microarray data analysis.
Kang, Suyeon; Song, Jongwoo
2017-09-02
A common task in microarray data analysis is to identify informative genes that are differentially expressed between two different states. Owing to the high-dimensional nature of microarray data, identification of significant genes has been essential in analyzing the data. However, the performances of many gene selection techniques are highly dependent on the experimental conditions, such as the presence of measurement error or a limited number of sample replicates. We have proposed new filter-based gene selection techniques, by applying a simple modification to significance analysis of microarrays (SAM). To prove the effectiveness of the proposed method, we considered a series of synthetic datasets with different noise levels and sample sizes along with two real datasets. The following findings were made. First, our proposed methods outperform conventional methods for all simulation set-ups. In particular, our methods are much better when the given data are noisy and sample size is small. They showed relatively robust performance regardless of noise level and sample size, whereas the performance of SAM became significantly worse as the noise level became high or sample size decreased. When sufficient sample replicates were available, SAM and our methods showed similar performance. Finally, our proposed methods are competitive with traditional methods in classification tasks for microarrays. The results of simulation study and real data analysis have demonstrated that our proposed methods are effective for detecting significant genes and classification tasks, especially when the given data are noisy or have few sample replicates. By employing weighting schemes, we can obtain robust and reliable results for microarray data analysis.
Simulation analysis of construction process of high rock slope's stabilization
ZHU Zhan-yuan; LING Xian-zhang; WANG Xuan-qing; ZOU Zu-yin
2008-01-01
A self-developed elasto-plastic finite element program was used to analyze the construction sequence of high rock slope' s stabilization in a coal-coking plant, and the result was compared with that employing the ultimate equilibrium method. Based on the results of finite element analysis, the stress contour graphs and dis-placement vector graphs at different construction steps were obtained, and the behavior of the slope during stabi-lization construction process was analyzed quantitatively. Based on the analysis of safety factors of three different schemes of stabilization and two different construction schemes, the assessment of stability and bracing design of the construction process were performed. The results show that the original reinforcement design is improper;the stability of the rock slope is controlled by a developed structural plane, the stability factor after excavation is less than 1, and the free surface should be braced in time ; for stability, the construction sequence should adopt that bracing follows excavation step by step up to down; the local slide occurred during the construction process agrees with the dangerous slide determined by the numerical analysis, which proves the validity and rationality of the adopted method.
Voltage stability analysis in the new deregulated environment
Zhu, Tong
Nowadays, a significant portion of the power industry is under deregulation. Under this new circumstance, network security analysis is more critical and more difficult. One of the most important issues in network security analysis is voltage stability analysis. Due to the expected higher utilization of equipment induced by competition in a power market that covers bigger power systems, this issue is increasingly acute after deregulation. In this dissertation, some selected topics of voltage stability analysis are covered. In the first part, after a brief review of general concepts of continuation power flow (CPF), investigations on various matrix analysis techniques to improve the speed of CPF calculation for large systems are reported. Based on these improvements, a new CPF algorithm is proposed. This new method is then tested by an inter-area transaction in a large inter-connected power system. In the second part, the Arnoldi algorithm, the best method to find a few minimum singular values for a large sparse matrix, is introduced into the modal analysis for the first time. This new modal analysis is applied to the estimation of the point of voltage collapse and contingency evaluation in voltage security assessment. Simulations show that the new method is very efficient. In the third part, after transient voltage stability component models are investigated systematically, a novel system model for transient voltage stability analysis, which is a logical-algebraic-differential-difference equation (LADDE), is offered. As an example, TCSC (Thyristor controlled series capacitors) is addressed as a transient voltage stabilizing controller. After a TCSC transient voltage stability model is outlined, a new TCSC controller is proposed to enhance both fault related and load increasing related transient voltage stability. Its ability is proven by the simulation.
Robust EBS design and source-term analysis for the partially saturated Yucca Mountain Site
Apted, M. [Intera Information Technologies, Inc., Denver, CO (United States)
1994-12-31
The concept of robust repository design and assessment is examined. Successful demonstration of decoupling of near-field and far-field performance is a central principle in achieving robustness. An innovative design for the engineered barrier system (EBS) for the partially saturated conditions at Yucca Mountain is described based on this principle of robustness.
Analysis of lateral stability of I-section aluminum beams
CHENG Ming; SHI Yongjiu; WANG Yuanqing
2006-01-01
This paper focuses on the lateral buckling of laterally-unrestrained aluminum beams subjected to a concentrated, uniformly loading and pure-bending action. The design methods of lateral stability of aluminum beams in the current codes are discussed. The influence of material property on the lateral buckling of aluminum beams is investigated with finite element analysis (FEA) methods. Some numerical examples are given, and the results from current codes are compared with the FEA solutions. The design method on lateral stability of steel beams specified in the Chinese standard GB 50017-2003 is modified to calibrate the stability factors of aluminum beams according to the European code, British code, and American code, and the modified method is verified by FEA results. Through comparison with the available test results, the modified design method for overall stability of aluminum bending members is proposed in this paper and proved applicable in the design of lateral stability of aluminum beams.
Simulation-Based Probabilistic Tsunami Hazard Analysis: Empirical and Robust Hazard Predictions
De Risi, Raffaele; Goda, Katsuichiro
2017-08-01
Probabilistic tsunami hazard analysis (PTHA) is the prerequisite for rigorous risk assessment and thus for decision-making regarding risk mitigation strategies. This paper proposes a new simulation-based methodology for tsunami hazard assessment for a specific site of an engineering project along the coast, or, more broadly, for a wider tsunami-prone region. The methodology incorporates numerous uncertain parameters that are related to geophysical processes by adopting new scaling relationships for tsunamigenic seismic regions. Through the proposed methodology it is possible to obtain either a tsunami hazard curve for a single location, that is the representation of a tsunami intensity measure (such as inundation depth) versus its mean annual rate of occurrence, or tsunami hazard maps, representing the expected tsunami intensity measures within a geographical area, for a specific probability of occurrence in a given time window. In addition to the conventional tsunami hazard curve that is based on an empirical statistical representation of the simulation-based PTHA results, this study presents a robust tsunami hazard curve, which is based on a Bayesian fitting methodology. The robust approach allows a significant reduction of the number of simulations and, therefore, a reduction of the computational effort. Both methods produce a central estimate of the hazard as well as a confidence interval, facilitating the rigorous quantification of the hazard uncertainties.
Ye, Jianxiong; Feng, Enmin; Wang, Lei; Xiu, Zhilong; Sun, Yaqin
Glycerol bioconversion to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae (K. pneumoniae) can be characterized by an intricate network of interactions among biochemical fluxes, metabolic compounds, key enzymes and genetic regulatory. To date, there still exist some uncertain factors in this complex network because of the limitation in bio-techniques, especially in measuring techniques for intracellular substances. In this paper, among these uncertain factors, we aim to infer the transport mechanisms of glycerol and 1,3-PD across the cell membrane, which have received intensive interest in recent years. On the basis of different inferences of the transport mechanisms, we reconstruct various metabolic networks correspondingly and subsequently develop their dynamical systems (S-systems). To determine the most reasonable metabolic network from all possible ones, we establish a quantitative definition of biological robustness and undertake parameter identification and robustness analysis for each system. Numerical results show that it is most possible that both glycerol and 1,3-PD pass the cell membrane by active transport and passive diffusion.
Robust estimation for homoscedastic regression in the secondary analysis of case-control data
Wei, Jiawei
2012-12-04
Primary analysis of case-control studies focuses on the relationship between disease D and a set of covariates of interest (Y, X). A secondary application of the case-control study, which is often invoked in modern genetic epidemiologic association studies, is to investigate the interrelationship between the covariates themselves. The task is complicated owing to the case-control sampling, where the regression of Y on X is different from what it is in the population. Previous work has assumed a parametric distribution for Y given X and derived semiparametric efficient estimation and inference without any distributional assumptions about X. We take up the issue of estimation of a regression function when Y given X follows a homoscedastic regression model, but otherwise the distribution of Y is unspecified. The semiparametric efficient approaches can be used to construct semiparametric efficient estimates, but they suffer from a lack of robustness to the assumed model for Y given X. We take an entirely different approach. We show how to estimate the regression parameters consistently even if the assumed model for Y given X is incorrect, and thus the estimates are model robust. For this we make the assumption that the disease rate is known or well estimated. The assumption can be dropped when the disease is rare, which is typically so for most case-control studies, and the estimation algorithm simplifies. Simulations and empirical examples are used to illustrate the approach.
AGCD:a robust periodicity analysis method based on approximate greatest common divisor
Juan YU‡; Pei-zhong LU
2015-01-01
Periodicity is one of the most common phenomena in the physical world. The problem of periodicity analysis (or period detection) is a research topic in several areas, such as signal processing and data mining. However, period detection is a very challenging problem, due to the sparsity and noisiness of observational datasets of periodic events. This paper focuses on the problem of period detection from sparse and noisy observational datasets. To solve the problem, a novel method based on the approximate greatest common divisor (AGCD) is proposed. The proposed method is robust to sparseness and noise, and is eﬃcient. Moreover, unlike most existing methods, it does not need prior knowledge of the rough range of the period. To evaluate the accuracy and eﬃciency of the proposed method, comprehensive experiments on synthetic data are conducted. Experimental results show that our method can yield highly accurate results with small datasets, is more robust to sparseness and noise, and is less sensitive to the magnitude of period than compared methods.
Arriaga, Miguel; Waisman, Haim
2017-06-01
A local physical stability criterion for multidimensional fracture problems modeled by the phase field method is developed and studied. Stability analysis provides a rigorous mathematical way to determine the onset of an unstable damage growth and fracture of the structure. In this work, stability is determined by examining the roots of a characteristic equation that arise when a linear perturbation technique is applied to the instantaneous partial differential equation system in a general viscoplastic material. It is shown that such analysis is not limited to a particular degradation function or energy split and could therefore be applied to a wide range of cases. Numerical results are presented to verify the theoretical predictions assuming quadratic and cubic degradation functions. Additionally we show that this stability criterion can be directly expanded to 2D with robust mesh-insensitive predictive capabilities with respect to crack nucleation and path. Several numerical examples are presented to verify these results.
Robust flood frequency analysis: Performance of EMA with multiple Grubbs-Beck outlier tests
Lamontagne, J. R.; Stedinger, J. R.; Yu, Xin; Whealton, C. A.; Xu, Ziyao
2016-04-01
Flood frequency analysis generally involves the use of simple parametric probability distributions to smooth and extrapolate the information provided by short flood records to estimate extreme flood flow quantiles. Parametric probability distributions can have difficulty simultaneously fitting both the largest and smallest floods. A danger is that the smallest observations in a record can distort the exceedance probabilities assigned to the large floods of interest. The identification and treatment of such Potentially Influential Low Floods (PILFs) frees a fitting algorithm to describe the distribution of the larger observations. This can allow parametric flood frequency analysis to be both efficient, and also robust to deviations from the proposed probability model's lower tail. Historically, PILF identification involved subjective judgement. We propose a new multiple Grubbs-Beck outlier test (MGBT) for objective PILF identification. MGBT PILF identification rates (akin to Type I errors) are reported for the lognormal (LN) distribution and the log-Pearson Type III (LP3) distribution with a variety of skew coefficients. MGBT PILF identification generally matched subjective identification from a recent California flood frequency study. Monte Carlo results show that censoring of PILFs identified by the MGBT algorithm improves the extreme quantile estimator efficiency of the expected moments algorithm (EMA) for negatively skewed LP3 distributions and has little effect for zero or positive skews; simultaneously it protects against deviations from the LP3 in the lower tail, as illustrated by distorted LN examples. Thus, MGBT generally makes flood frequency analysis based on the LP3 distribution with EMA both more accurate and more robust.
Dynamic remedial action scheme using online transient stability analysis
Shrestha, Arun
configuration and operating state. The generation-shedding cost is calculated using pre-RAS and post-RAS OPF costs. The criteria for selecting generators to trip is based on the minimum cost rather than minimum amount of generation to shed. For an unstable Category C contingency, the RAS control action that results in stable system with minimum generation shedding cost is selected among possible candidate solutions. The RAS control actions update whenever there is a change in operating condition, system configuration, or cost functions. The effectiveness of the proposed technique is demonstrated by simulations on the IEEE 9-bus system, the IEEE 39-bus system, and IEEE 145-bus system. This dissertation also proposes an improved, yet relatively simple, technique for solving Transient Stability-Constrained Optimal Power Flow (TSC-OPF) problem. Using the SIME method, the sets of dynamic and transient stability constraints are reduced to a single stability constraint, decreasing the overall size of the optimization problem. The transient stability constraint is formulated using the critical machines' power at the initial time step, rather than using the machine rotor angles. This avoids the addition of machine steady state stator algebraic equations in the conventional OPF algorithm. A systematic approach to reach an optimal solution is developed by exploring the quasi-linear behavior of critical machine power and stability margin. The proposed method shifts critical machines active power based on generator costs using an OPF algorithm. Moreover, the transient stability limit is based on stability margin, and not on a heuristically set limit on OMIB rotor angle. As a result, the proposed TSC-OPF solution is more economical and transparent. The proposed technique enables the use of fast and robust commercial OPF tool and time-domain simulation software for solving large scale TSC-OPF problem, which makes the proposed method also suitable for real-time application.
Barth, Aline Bergesch; de Oliveira, Gabriela Bolfe; Malesuik, Marcelo Donadel; Paim, Clésio Soldatelli; Volpato, Nadia Maria
2011-08-01
A stability-indicating liquid chromatography method for the determination of the antifungal agent butenafine hydrochloride (BTF) in a cream was developed and validated using the Plackett-Burman experimental design for robustness evaluation. Also, the drug photodegradation kinetics was determined. The analytical column was operated with acetonitrile, methanol and a solution of triethylamine 0.3% adjusted to pH 4.0 (6:3:1) at a flow rate of 1 mL/min and detection at 283 nm. BTF extraction from the cream was done with n-butyl alcohol and methanol in ultrasonic bath. The performed degradation conditions were: acid and basic media with HCl 1M and NaOH 1M, respectively, oxidation with H(2)O(2) 10%, and the exposure to UV-C light. No interference in the BTF elution was verified. Linearity was assessed (r(2) = 0.9999) and ANOVA showed non-significative linearity deviation (p > 0.05). Adequate results were obtained for repeatability, intra-day precision, and accuracy. Critical factors were selected to examine the method robustness with the two-level Plackett-Burman experimental design and no significant factors were detected (p > 0.05). The BTF photodegradation kinetics was determined for the standard and for the cream, both in methanolic solution, under UV light at 254 nm. The degradation process can be described by first-order kinetics in both cases.
Palaniswamy, Hariharasudhan; Kanthadai, Narayan; Roy, Subir; Beauchesne, Erwan
2011-08-01
Crash, NVH (Noise, Vibration, Harshness), and durability analysis are commonly deployed in structural CAE analysis for mechanical design of components especially in the automotive industry. Components manufactured by stamping constitute a major portion of the automotive structure. In CAE analysis they are modeled at a nominal state with uniform thickness and no residual stresses and strains. However, in reality the stamped components have non-uniformly distributed thickness and residual stresses and strains resulting from stamping. It is essential to consider the stamping information in CAE analysis to accurately model the behavior of the sheet metal structures under different loading conditions. Especially with the current emphasis on weight reduction by replacing conventional steels with aluminum and advanced high strength steels it is imperative to avoid over design. Considering this growing need in industry, a highly automated and robust method has been integrated within Altair Hyperworks® to initialize sheet metal components in CAE models with stamping data. This paper demonstrates this new feature and the influence of stamping data for a full car frontal crash analysis.
Solar Dynamic Power System Stability Analysis and Control
Momoh, James A.; Wang, Yanchun
1996-01-01
The objective of this research is to conduct dynamic analysis, control design, and control performance test of solar power system. Solar power system consists of generation system and distribution network system. A bench mark system is used in this research, which includes a generator with excitation system and governor, an ac/dc converter, six DDCU's and forty-eight loads. A detailed model is used for modeling generator. Excitation system is represented by a third order model. DDCU is represented by a seventh order system. The load is modeled by the combination of constant power and constant impedance. Eigen-analysis and eigen-sensitivity analysis are used for system dynamic analysis. The effects of excitation system, governor, ac/dc converter control, and the type of load on system stability are discussed. In order to improve system transient stability, nonlinear ac/dc converter control is introduced. The direct linearization method is used for control design. The dynamic analysis results show that these controls affect system stability in different ways. The parameter coordination of controllers are recommended based on the dynamic analysis. It is concluded from the present studies that system stability is improved by the coordination of control parameters and the nonlinear ac/dc converter control stabilize system oscillation caused by the load change and system fault efficiently.
Nonlinear analysis on purely mechanical stabilization of a wheeled inverted pendulum on a slope
Yoshida, Katsutoshi; Hosomi, Kenta
2015-01-01
This paper investigates the potential for stabilizing an inverted pendulum without electric devices, using gravitational potential energy. We propose a wheeled mechanism on a slope, specifically, a wheeled double pendulum, whose second pendulum transforms gravity force into braking force that acts on the wheel. In this paper, we derive steady-state equations of this system and conduct nonlinear analysis to obtain parameter conditions under which the standing position of the first pendulum becomes asymptotically stable. In this asymptotically stable condition, the proposed mechanism descends the slope in a stable standing position, while dissipating gravitational potential energy via the brake mechanism. By numerically continuing the stability limits in the parameter space, we find that the stable parameter region is simply connected. This implies that the proposed mechanism can be robust against errors in parameter setting.
Stability Analysis of Neural Networks-Based System Identification
Talel Korkobi
2008-01-01
Full Text Available This paper treats some problems related to nonlinear systems identification. A stability analysis neural network model for identifying nonlinear dynamic systems is presented. A constrained adaptive stable backpropagation updating law is presented and used in the proposed identification approach. The proposed backpropagation training algorithm is modified to obtain an adaptive learning rate guarantying convergence stability. The proposed learning rule is the backpropagation algorithm under the condition that the learning rate belongs to a specified range defining the stability domain. Satisfying such condition, unstable phenomena during the learning process are avoided. A Lyapunov analysis leads to the computation of the expression of a convenient adaptive learning rate verifying the convergence stability criteria. Finally, the elaborated training algorithm is applied in several simulations. The results confirm the effectiveness of the CSBP algorithm.
Stability Analysis for Stochastic Delayed High-order Neural Networks
无
2006-01-01
In this paper, the global asymptotic stability analysis problem is considered for a class of stochastic high-order neural networks with time-delays. Based on a Lyapunov-Krasovskii functional and the stochastic stability analysis theory, several sufficient conditions are derived in order to guarantee the global asymptotic convergence of the equilibrium point in the mean square. Investigation shows that the addressed stochastic highorder delayed neural networks are globally asymptotically stable in the mean square if there are solutions to some linear matrix inequalities (LMIs). Hence, the global asymptotic stability of the studied stochastic high-order delayed neural networks can be easily checked by the Matlab LMI toolbox. A numerical example is given to demonstrate the usefulness of the proposed global stability criteria.
Fully Parallel MHD Stability Analysis Tool
Svidzinski, Vladimir; Galkin, Sergei; Kim, Jin-Soo; Liu, Yueqiang
2015-11-01
Progress on full parallelization of the plasma stability code MARS will be reported. MARS calculates eigenmodes in 2D axisymmetric toroidal equilibria in MHD-kinetic plasma models. It is a powerful tool for studying MHD and MHD-kinetic instabilities and it is widely used by fusion community. Parallel version of MARS is intended for simulations on local parallel clusters. It will be an efficient tool for simulation of MHD instabilities with low, intermediate and high toroidal mode numbers within both fluid and kinetic plasma models, already implemented in MARS. Parallelization of the code includes parallelization of the construction of the matrix for the eigenvalue problem and parallelization of the inverse iterations algorithm, implemented in MARS for the solution of the formulated eigenvalue problem. Construction of the matrix is parallelized by distributing the load among processors assigned to different magnetic surfaces. Parallelization of the solution of the eigenvalue problem is made by repeating steps of the present MARS algorithm using parallel libraries and procedures. Results of MARS parallelization and of the development of a new fix boundary equilibrium code adapted for MARS input will be reported. Work is supported by the U.S. DOE SBIR program.
Kinematic analysis of rope skipper's stability
Ab Ghani, Nor Atikah; Rambely, Azmin Sham
2014-06-01
There are various kinds of jumping that can be done while performing rope skipping activity. This activity was always associated with injury. But, if the rope skipper can perform the activity in a right way, it is believed that the injury might be reduced. The main purpose of this paper is to observe the stability of rope skipper from a biomechanics perspective, which are the centre of mass, angle at the ankle, knee and hip joints and also the trajectory for the ipsilateral leg between the two types of skip which is one leg and two legs. Six healthy, physically active subject, two males and four females (age: 8.00±1.25 years, weight: 17.90±6.85 kg and height: 1.22±0.08 m) participated in this study. Kinematic data of repeated five cycles of rope skipping activity was captured by using Vicon Nexus system. Based on the data collected, skipping with two legs shows more stable behavior during preparation, flight and landing phases. It is concluded that landing on the balls of the feet, lowering the trajectory positions of the feet from the ground as well as flexion of each joint which would reduce the injury while landing.
Ghosh, Debarchana; Manson, Steven M.
2008-01-01
In this paper, we present a hybrid approach, robust principal component geographically weighted regression (RPCGWR), in examining urbanization as a function of both extant urban land use and the effect of social and environmental factors in the Twin Cities Metropolitan Area (TCMA) of Minnesota. We used remotely sensed data to treat urbanization via the proxy of impervious surface. We then integrated two different methods, robust principal component analysis (RPCA) and geographically weighted ...
Stability analysis for natural slope by kinematical approach
孙志彬; 覃长兵
2014-01-01
The stability of natural slope was analyzed on the basis of limit analysis. The sliding model of a kind of natural slope was presented. A new kinematically admissible velocity field for the new sliding model was constructed. The stability factor formulation by the upper bound theorem leads to a classical nonlinear programming problem, when the external work rate and internal energy dissipation were solved, and the constraint condition of the programming problem was given. The upper bound optimization problem can be solved efficiently by applying a nonlinear SQP algorithm, and stability factor was obtained, which agrees well with previous achievements.
Robust Spectral Estimation of Track Irregularity
Fu Wenjuan; Chen Chunjun
2005-01-01
Because the existing spectral estimation methods for railway track irregularity analysis are very sensitive to outliers, a robust spectral estimation method is presented to process track irregularity signals. The proposed robust method is verified using 100 groups of clean/contaminated data reflecting he vertical profile irregularity taken from Bejing-Guangzhou railway with a sampling frequency of 33 data every 10 m, and compared with the Auto Regressive (AR) model. The experimental results show that the proposed robust estimation is resistible to noise and insensitive to outliers, and is superior to the AR model in terms of efficiency, stability and reliability.
Robust Ambiguity Estimation for an Automated Analysis of the Intensive Sessions
Kareinen, Niko; Hobiger, Thomas; Haas, Rüdiger
2016-12-01
Very Long Baseline Interferometry (VLBI) is a unique space-geodetic technique that can directly determine the Earth's phase of rotation, namely UT1. The daily estimates of the difference between UT1 and Coordinated Universal Time (UTC) are computed from one-hour long VLBI Intensive sessions. These sessions are essential for providing timely UT1 estimates for satellite navigation systems. To produce timely UT1 estimates, efforts have been made to completely automate the analysis of VLBI Intensive sessions. This requires automated processing of X- and S-band group delays. These data often contain an unknown number of integer ambiguities in the observed group delays. In an automated analysis with the c5++ software the standard approach in resolving the ambiguities is to perform a simplified parameter estimation using a least-squares adjustment (L2-norm minimization). We implement the robust L1-norm with an alternative estimation method in c5++. The implemented method is used to automatically estimate the ambiguities in VLBI Intensive sessions for the Kokee-Wettzell baseline. The results are compared to an analysis setup where the ambiguity estimation is computed using the L2-norm. Additionally, we investigate three alternative weighting strategies for the ambiguity estimation. The results show that in automated analysis the L1-norm resolves ambiguities better than the L2-norm. The use of the L1-norm leads to a significantly higher number of good quality UT1-UTC estimates with each of the three weighting strategies.
Robust Change Vector Analysis (RCVA) for multi-sensor very high resolution optical satellite data
Thonfeld, Frank; Feilhauer, Hannes; Braun, Matthias; Menz, Gunter
2016-08-01
The analysis of rapid land cover/land use changes by means of remote sensing is often based on data acquired under varying and occasionally unfavorable conditions. In addition, such analyses frequently use data acquired by different sensor systems. These acquisitions often differ with respect to sun position and sensor viewing geometry which lead to characteristic effects in each image. These differences may have a negative impact on reliable change detection. Here, we propose an approach called Robust Change Vector Analysis (RCVA), aiming to mitigate these effects. RCVA is an improvement of the widely-used Change Vector Analysis (CVA), developed to account for pixel neighborhood effects. We used a RapidEye and Kompsat-2 cross-sensor change detection test to demonstrate the efficiency of RCVA. Our analysis showed that RCVA results in fewer false negatives as well as false positives when compared to CVA under similar test conditions. We conclude that RCVA is a powerful technique which can be utilized to reduce spurious changes in bi-temporal change detection analyses based on high- or very-high spatial resolution imagery.
刘艳; 蒋卫生; 黄发伦
2004-01-01
It has been observed that for many stable feedback control systems, the introduction of arbitrarily small delays into the loop causes instability. Therefore, robustness of stablility with respect to small delays is of great importance. The authors study the robustness with respect to small delays for exponential stability of Pritchard-Salamon systems with admissible state feedback,i.e. the exponential stability of the following systems are equivalent:(x(t)=S(t)x0+∫t0S(t-s)ds)(u(t)=Fx(t),x0∈V,t≥0)(x(t)=S(t)x0+∫t0S(t-s)BFx(s-r)ds)(u(t)=Fx(t-r),x0∈V,t≥0)and obtain a mumber of necessary and sufficient conditions,particularly,frepuency domain characterization for robustness with respect to small delays for exponential stability.
Stability Analysis for a Multi-Camera Photogrammetric System
Ayman Habib
2014-08-01
Full Text Available Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing stability analysis for a single camera. The paper then points out the lack of coverage of stability analysis for multi-camera systems, suggests a modification of the collinearity model to be used for the calibration of an entire photogrammetric system, and proposes three methods for system stability analysis. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration stability, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and stability analysis was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction.
Probabilistic approaches for geotechnical site characterization and slope stability analysis
Cao, Zijun; Li, Dianqing
2017-01-01
This is the first book to revisit geotechnical site characterization from a probabilistic point of view and provide rational tools to probabilistically characterize geotechnical properties and underground stratigraphy using limited information obtained from a specific site. This book not only provides new probabilistic approaches for geotechnical site characterization and slope stability analysis, but also tackles the difficulties in practical implementation of these approaches. In addition, this book also develops efficient Monte Carlo simulation approaches for slope stability analysis and implements these approaches in a commonly available spreadsheet environment. These approaches and the software package are readily available to geotechnical practitioners and alleviate them from reliability computational algorithms. The readers will find useful information for a non-specialist to determine project-specific statistics of geotechnical properties and to perform probabilistic analysis of slope stability.
Pyrosequencing Based Microbial Community Analysis of Stabilized Mine Soils
Park, J. E.; Lee, B. T.; Son, A.
2015-12-01
Heavy metals leached from exhausted mines have been causing severe environmental problems in nearby soils and groundwater. Environmental mitigation was performed based on the heavy metal stabilization using Calcite and steel slag in Korea. Since the soil stabilization only temporarily immobilizes the contaminants to soil matrix, the potential risk of re-leaching heavy metal still exists. Therefore the follow-up management of stabilized soils and the corresponding evaluation methods are required to avoid the consequent contamination from the stabilized soils. In this study, microbial community analysis using pyrosequencing was performed for assessing the potential leaching of the stabilized soils. As a result of rarefaction curve and Chao1 and Shannon indices, the stabilized soil has shown lower richness and diversity as compared to non-contaminated negative control. At the phyla level, as the degree of contamination increases, most of phyla decreased with only exception of increased proteobacteria. Among proteobacteria, gamma-proteobacteria increased against the heavy metal contamination. At the species level, Methylobacter tundripaludum of gamma-proteobacteria showed the highest relative portion of microbial community, indicating that methanotrophs may play an important role in either solubilization or immobilization of heavy metals in stabilized soils.
ANALYSIS OF TIPOVER STABILITY FOR NOVEL SHAPE SHIFTING MODULAR ROBOT
LIU Jinguo; WANG Yuechao; MA Shugen; LI Bin
2006-01-01
A novel three-module robot has been introduced. It can change its configuration toadapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configuration. They are line type, triangle type, and row type. After the factors and the countermeasures of mobile robot's tipover problem are analyzed, stability pyramid and tipover stability index are proposed to globally determinate the mobile robot's static stability and dynamic stability.The shape shifting robot is tested by this technique under the combined disturbance of pitch, roll and yaw in simulation. The simulation result shows that this technique is effective for the analysis of mobile robot's tipover stability, especially for the reconfigurable or shape shifting modular robot.Experiments on three symmetry configurations are made under unstructured environments. The environment experiment shows the same result as that of the simulation that the triangle type configuration has the best stability. Both simulation and experiment provide a valid reference for the reconfigurable robot's potential application.
Stability analysis of an encapsulated microbubble against gas diffusion.
Katiyar, Amit; Sarkar, Kausik
2010-03-01
Linear stability analysis is performed for a mathematical model of diffusion of gases from an encapsulated microbubble. It is an Epstein-Plesset model modified to account for encapsulation elasticity and finite gas permeability. Although bubbles, containing gases other than air, are considered, the final stable bubble, if any, contains only air, and stability is achieved only when the surrounding medium is saturated or oversaturated with air. In absence of encapsulation elasticity, only a neutral stability is achieved for zero surface tension, the other solution being unstable. For an elastic encapsulation, different equilibrium solutions are obtained depending on the saturation level and whether the surface tension is smaller or higher than the elasticity. For an elastic encapsulation, elasticity can stabilize the bubble. However, imposing a non-negativity condition on the effective surface tension (consisting of reference surface tension and the elastic stress) leads to an equilibrium radius which is only neutrally stable. If the encapsulation can support a net compressive stress, it achieves actual stability. The linear stability results are consistent with our recent numerical findings. Physical mechanisms for the stability or instability of various equilibriums are provided.
Matrix properties relating to stability analysis
Di Caprio, U. [ENEL s.p.a., Cologno Monzese (Italy)
2001-03-01
With reference to a multimachine power system are presented properties and conditions to be satisfied by matrices M, K, D (inertia coefficients, synchronizing coefficients and damping coefficients) in order that the system can be stable. The analysis is carried out with the assumption that the transfer-conductances are negligible while the damping effects (of the field and damper circuits) are taken into account. The formulation is general, i.e. it can be applied to any system with n degrees of freedom, subjected to conservative positional forces and to dissipative forces linearly dependent upon the speed. (author)
M. Santhakumar
2009-01-01
Full Text Available Hydrodynamic parameters play a major role in the dynamics and control of Autonomous Underwater Vehicles (AUVs. The performance of an AUV is dependent on the parameter variations and a proper understanding of these parametric influences is essential for the design, modeling, and control of high-performance AUVs. In this paper, the sensitivity of hydrodynamic parameters on the control of a flatfish type AUV is analyzed using robust design techniques such as Taguchi's design method and statistical analysis tools such as Pareto-ANOVA. Since the pitch angle of an AUV is one of the crucial variables in the control applications, the sensitivity analysis of pitch angle variation is studied here. Eight prominent hydrodynamic coefficients are considered in the analysis. The results show that there are two critical hydrodynamic parameters, that is, hydrodynamic force and hydrodynamic pitching moment in the heave direction that influence the performance of a flatfish type AUV. A near-optimal combination of the parameters was identified and the simulation results have shown the effectiveness of the method in reducing the pitch error. These findings are significant for the design modifications as well as controller design of AUVs.
Robustness of arterial blood gas analysis for assessment of respiratory safety pharmacology in rats.
Whiteside, Garth T; Hummel, Michele; Boulet, Jamie; Beyenhof, Jessica D; Strenkowski, Bryan; John, Janet Dell; Knappenberger, Terri; Maselli, Harry; Koetzner, Lee
2016-01-01
Whole body plethysmography using unrestrained animals is a common technique for assessing the respiratory risk of new drugs in safety pharmacology studies in rats. However, wide variations in experimental technique make cross laboratory comparison of data difficult and raise concerns that non-appropriate conditions may mask the deleterious effects of test compounds - in particular with suspected respiratory depressants. Therefore, the objective of this study was to evaluate the robustness of arterial blood gas analysis as an alternative to plethysmography in rats. We sought to do this by assessing the effect of different vehicles and times post-surgical catheterization on blood gas measurements, in addition to determining sensitivity to multiple opioids. Furthermore, we determined intra-lab variability from multiple datasets utilizing morphine and generated within a single lab and lastly, inter-lab variability was measured by comparing datasets generated in two separate labs. Overall, our data show that arterial blood gas analysis is a measure that is both flexible in terms of experimental conditions and highly sensitive to respiratory depressants, two key limitations when using plethysmography. As such, our data strongly advocate the adoption of arterial blood gas analysis as an investigative approach to reliably examine the respiratory depressant effects of opioids. Copyright © 2015 Elsevier Inc. All rights reserved.
Robustness analysis of a green chemistry-based model for the ...
This paper proposes a robustness analysis based on Multiple Criteria Decision Aiding (MCDA). The ensuing model was used to assess the implementation of green chemistry principles in the synthesis of silver nanoparticles. Its recommendations were also compared to an earlier developed model for the same purpose to investigate concordance between the models and potential decision support synergies. A three-phase procedure was adopted to achieve the research objectives. Firstly, an ordinal ranking of the evaluation criteria used to characterize the implementation of green chemistry principles was identified through relative ranking analysis. Secondly, a structured selection process for an MCDA classification method was conducted, which ensued in the identification of Stochastic Multi-Criteria Acceptability Analysis (SMAA). Lastly, the agreement of the classifications by the two MCDA models and the resulting synergistic role of decision recommendations were studied. This comparison showed that the results of the two models agree between 76% and 93% of the simulation set-ups and it confirmed that different MCDA models provide a more inclusive and transparent set of recommendations. This integrative research confirmed the beneficial complementary use of MCDA methods to aid responsible development of nanosynthesis, by accounting for multiple objectives and helping communication of complex information in a comprehensive and traceable format, suitable for stakeholders and
A new framework for comprehensive, robust, and efficient global sensitivity analysis: 1. Theory
Razavi, Saman; Gupta, Hoshin V.
2016-01-01
Computer simulation models are continually growing in complexity with increasingly more factors to be identified. Sensitivity Analysis (SA) provides an essential means for understanding the role and importance of these factors in producing model responses. However, conventional approaches to SA suffer from (1) an ambiguous characterization of sensitivity, and (2) poor computational efficiency, particularly as the problem dimension grows. Here, we present a new and general sensitivity analysis framework (called VARS), based on an analogy to "variogram analysis," that provides an intuitive and comprehensive characterization of sensitivity across the full spectrum of scales in the factor space. We prove, theoretically, that Morris (derivative-based) and Sobol (variance-based) methods and their extensions are special cases of VARS, and that their SA indices can be computed as by-products of the VARS framework. Synthetic functions that resemble actual model response surfaces are used to illustrate the concepts, and show VARS to be as much as two orders of magnitude more computationally efficient than the state-of-the-art Sobol approach. In a companion paper, we propose a practical implementation strategy, and demonstrate the effectiveness, efficiency, and reliability (robustness) of the VARS framework on real-data case studies.
Stability analysis of an aeroelastic system with friction
Tan Tiancai; Li Min; Liu Baihui
2013-01-01
In this paper,harmonic balance method,exact formulation and numerical simulation method are adopted to study the effects of different friction stiffness on the stability of 1.5 degrees of freedom aeroelastic system.On this basis,the expressions of input energy and dissipated energy are deduced,and the energy method is used to reveal the mechanisms of the stable boundary and unstable boundary existing in the system and the effects of different friction stiffness on the stability of the system.Studies have shown that the stability region and the critical aerodynamic damping ratio of the system rise with the increase of the friction stiffness,while the friction stiffness has little effect on the stability boundary.In the analysis of the stability of system,the results of harmonic balance method,exact formulation and Newmark of numerical simulation method are in good agreement.Compared with exact formulation and numerical simulation method,the concept and conclusion of harmonic balance method are simple in the system stability analysis.
Static Voltage Stability Analysis by Using SVM and Neural Network
Mehdi Hajian
2013-01-01
Full Text Available Voltage stability is an important problem in power system networks. In this paper, in terms of static voltage stability, and application of Neural Networks (NN and Supported Vector Machine (SVM for estimating of voltage stability margin (VSM and predicting of voltage collapse has been investigated. This paper considers voltage stability in power system in two parts. The first part calculates static voltage stability margin by Radial Basis Function Neural Network (RBFNN. The advantage of the used method is high accuracy in online detecting the VSM. Whereas the second one, voltage collapse analysis of power system is performed by Probabilistic Neural Network (PNN and SVM. The obtained results in this paper indicate, that time and number of training samples of SVM, are less than NN. In this paper, a new model of training samples for detection system, using the normal distribution load curve at each load feeder, has been used. Voltage stability analysis is estimated by well-know L and VSM indexes. To demonstrate the validity of the proposed methods, IEEE 14 bus grid and the actual network of Yazd Province are used.
Performance and Stability Analysis of a Shrouded-Fan UAV
de Divitiis, Nicola
2009-01-01
This paper deals with the estimation of the performance and stability for a shrouded-fan unmanned rotorcraft whose mission profile also prescribes the flight in ground effect. The not so simple estimation of the aerodynamic coefficients and of the thrust in the various situations makes the performance calculation and the stability analysis difficult tasks. This is due to the strong interaction between the fan flow and shroud that causes quite different flow structures about the airframe depending on flight conditions. A further difficulty is related to the ground effect which produces substantial modifications in the rotor thrust and aerodynamic coefficients. To evaluate performance and stability, two models have been developed. One determines the aerodynamic coefficients of the shroud, whereas the other one calculates thrust and moment of the rotors system. Both models take into account the mutual interference between fan flow and fuselage and ground effect. Performance and stability are then discussed with ...
Stability analysis of embedded nonlinear predictor neural generalized predictive controller
Hesham F. Abdel Ghaffar
2014-03-01
Full Text Available Nonlinear Predictor-Neural Generalized Predictive Controller (NGPC is one of the most advanced control techniques that are used with severe nonlinear processes. In this paper, a hybrid solution from NGPC and Internal Model Principle (IMP is implemented to stabilize nonlinear, non-minimum phase, variable dead time processes under high disturbance values over wide range of operation. Also, the superiority of NGPC over linear predictive controllers, like GPC, is proved for severe nonlinear processes over wide range of operation. The necessary conditions required to stabilize NGPC is derived using Lyapunov stability analysis for nonlinear processes. The NGPC stability conditions and improvement in disturbance suppression are verified by both simulation using Duffing’s nonlinear equation and real-time using continuous stirred tank reactor. Up to our knowledge, the paper offers the first hardware embedded Neural GPC which has been utilized to verify NGPC–IMP improvement in realtime.
Computational Stability Analysis of Lotka-Volterra Systems
Polcz Péter
2016-12-01
Full Text Available This paper concerns the computational stability analysis of locally stable Lotka-Volterra (LV systems by searching for appropriate Lyapunov functions in a general quadratic form composed of higher order monomial terms. The Lyapunov conditions are ensured through the solution of linear matrix inequalities. The stability region is estimated by determining the level set of the Lyapunov function within a suitable convex domain. The paper includes interesting computational results and discussion on the stability regions of higher (3,4 dimensional LV models as well as on the monomial selection for constructing the Lyapunov functions. Finally, the stability region is estimated of an uncertain 2D LV system with an uncertain interior locally stable equilibrium point.
Stability Analysis of Nonuniform Rectangular Beams Using Homotopy Perturbation Method
Seval Pinarbasi
2012-01-01
Full Text Available The design of slender beams, that is, beams with large laterally unsupported lengths, is commonly controlled by stability limit states. Beam buckling, also called “lateral torsional buckling,” is different from column buckling in that a beam not only displaces laterally but also twists about its axis during buckling. The coupling between twist and lateral displacement makes stability analysis of beams more complex than that of columns. For this reason, most of the analytical studies in the literature on beam stability are concentrated on simple cases: uniform beams with ideal boundary conditions and simple loadings. This paper shows that complex beam stability problems, such as lateral torsional buckling of rectangular beams with variable cross-sections, can successfully be solved using homotopy perturbation method (HPM.
Michal Markovich Gordon
Full Text Available MOTIVATION: It has been proposed that clustering clinical markers, such as blood test results, can be used to stratify patients. However, the robustness of clusters formed with this approach to data pre-processing and clustering algorithm choices has not been evaluated, nor has clustering reproducibility. Here, we made use of the NHANES survey to compare clusters generated with various combinations of pre-processing and clustering algorithms, and tested their reproducibility in two separate samples. METHOD: Values of 44 biomarkers and 19 health/life style traits were extracted from the National Health and Nutrition Examination Survey (NHANES. The 1999-2002 survey was used for training, while data from the 2003-2006 survey was tested as a validation set. Twelve combinations of pre-processing and clustering algorithms were applied to the training set. The quality of the resulting clusters was evaluated both by considering their properties and by comparative enrichment analysis. Cluster assignments were projected to the validation set (using an artificial neural network and enrichment in health/life style traits in the resulting clusters was compared to the clusters generated from the original training set. RESULTS: The clusters obtained with different pre-processing and clustering combinations differed both in terms of cluster quality measures and in terms of reproducibility of enrichment with health/life style properties. Z-score normalization, for example, dramatically improved cluster quality and enrichments, as compared to unprocessed data, regardless of the clustering algorithm used. Clustering diabetes patients revealed a group of patients enriched with retinopathies. This could indicate that routine laboratory tests can be used to detect patients suffering from complications of diabetes, although other explanations for this observation should also be considered. CONCLUSIONS: Clustering according to classical clinical biomarkers is a robust
Robust object tracking techniques for vision-based 3D motion analysis applications
Knyaz, Vladimir A.; Zheltov, Sergey Y.; Vishnyakov, Boris V.
2016-04-01
Automated and accurate spatial motion capturing of an object is necessary for a wide variety of applications including industry and science, virtual reality and movie, medicine and sports. For the most part of applications a reliability and an accuracy of the data obtained as well as convenience for a user are the main characteristics defining the quality of the motion capture system. Among the existing systems for 3D data acquisition, based on different physical principles (accelerometry, magnetometry, time-of-flight, vision-based), optical motion capture systems have a set of advantages such as high speed of acquisition, potential for high accuracy and automation based on advanced image processing algorithms. For vision-based motion capture accurate and robust object features detecting and tracking through the video sequence are the key elements along with a level of automation of capturing process. So for providing high accuracy of obtained spatial data the developed vision-based motion capture system "Mosca" is based on photogrammetric principles of 3D measurements and supports high speed image acquisition in synchronized mode. It includes from 2 to 4 technical vision cameras for capturing video sequences of object motion. The original camera calibration and external orientation procedures provide the basis for high accuracy of 3D measurements. A set of algorithms as for detecting, identifying and tracking of similar targets, so for marker-less object motion capture is developed and tested. The results of algorithms' evaluation show high robustness and high reliability for various motion analysis tasks in technical and biomechanics applications.
Robustness analysis of an air heating plant and control law by using polynomial chaos
Colón, Diego [University of São Paulo, Polytechnic School, LAC -PTC, São Paulo (Brazil); Ferreira, Murillo A. S.; Bueno, Átila M. [São Paulo State University - Sorocaba Campus, Sorocaba (Brazil); Balthazar, José M. [São Paulo State University - Rio Claro Campus, Rio Claro (Brazil); Rosa, Suélia S. R. F. de [University of Brasilia, Brasilia (Brazil)
2014-12-10
This paper presents a robustness analysis of an air heating plant with a multivariable closed-loop control law by using the polynomial chaos methodology (MPC). The plant consists of a PVC tube with a fan in the air input (that forces the air through the tube) and a mass flux sensor in the output. A heating resistance warms the air as it flows inside the tube, and a thermo-couple sensor measures the air temperature. The plant has thus two inputs (the fan's rotation intensity and heat generated by the resistance, both measured in percent of the maximum value) and two outputs (air temperature and air mass flux, also in percent of the maximal value). The mathematical model is obtained by System Identification techniques. The mass flux sensor, which is nonlinear, is linearized and the delays in the transfer functions are properly approximated by non-minimum phase transfer functions. The resulting model is transformed to a state-space model, which is used for control design purposes. The multivariable robust control design techniques used is the LQG/LTR, and the controllers are validated in simulation software and in the real plant. Finally, the MPC is applied by considering some of the system's parameters as random variables (one at a time, and the system's stochastic differential equations are solved by expanding the solution (a stochastic process) in an orthogonal basis of polynomial functions of the basic random variables. This method transforms the stochastic equations in a set of deterministic differential equations, which can be solved by traditional numerical methods (That is the MPC). Statistical data for the system (like expected values and variances) are then calculated. The effects of randomness in the parameters are evaluated in the open-loop and closed-loop pole's positions.
Applications of gauge duality in robust principal component analysis and semidefinite programming
Ma, ShiQian; Yang, JunFeng
2016-08-01
Gauge duality theory was originated by Freund [Math. Programming, 38(1):47-67, 1987] and was recently further investigated by Friedlander, Mac{\\^e}do and Pong [SIAM J. Optm., 24(4):1999-2022, 2014]. When solving some matrix optimization problems via gauge dual, one is usually able to avoid full matrix decompositions such as singular value and/or eigenvalue decompositions. In such an approach, a gauge dual problem is solved in the first stage, and then an optimal solution to the primal problem can be recovered from the dual optimal solution obtained in the first stage. Recently, this theory has been applied to a class of \\emph{semidefinite programming} (SDP) problems with promising numerical results [Friedlander and Mac{\\^e}do, SIAM J. Sci. Comp., to appear, 2016]. In this paper, we establish some theoretical results on applying the gauge duality theory to robust \\emph{principal component analysis} (PCA) and general SDP. For each problem, we present its gauge dual problem, characterize the optimality conditions for the primal-dual gauge pair, and validate a way to recover a primal optimal solution from a dual one. These results are extensions of [Friedlander and Mac{\\^e}do, SIAM J. Sci. Comp., to appear, 2016] from nuclear norm regularization to robust PCA and from a special class of SDP which requires the coefficient matrix in the linear objective to be positive definite to SDP problems without this restriction. Our results provide further understanding in the potential advantages and disadvantages of the gauge duality theory.
Vezér, Martin A
2016-04-01
To study climate change, scientists employ computer models, which approximate target systems with various levels of skill. Given the imperfection of climate models, how do scientists use simulations to generate knowledge about the causes of observed climate change? Addressing a similar question in the context of biological modelling, Levins (1966) proposed an account grounded in robustness analysis. Recent philosophical discussions dispute the confirmatory power of robustness, raising the question of how the results of computer modelling studies contribute to the body of evidence supporting hypotheses about climate change. Expanding on Staley's (2004) distinction between evidential strength and security, and Lloyd's (2015) argument connecting variety-of-evidence inferences and robustness analysis, I address this question with respect to recent challenges to the epistemology robustness analysis. Applying this epistemology to case studies of climate change, I argue that, despite imperfections in climate models, and epistemic constraints on variety-of-evidence reasoning and robustness analysis, this framework accounts for the strength and security of evidence supporting climatological inferences, including the finding that global warming is occurring and its primary causes are anthropogenic.
Surficial Stability Analysis for Landslide Prediction
Cho, Sung Eun
2017-04-01
In Korea where rainfall of strong intensities is frequent, the depth of weathered residual soil is shallow in mountainous region. Therefore, full saturation of soil layer caused by the reaching of rainwater from the slope surface to impermeable bedrock is one of important causes of landslide. In this study, a shallow slope failure analysis method for slopes with shallow bedrock was developed to predict landslide based on one-dimensional Green-Ampt model. Constant intensities of rainfall were considered and shallow impermeable boundary condition was imposed on the Green-Ampt model to simulate the impermeable bedrock underlying the shallow weathered residual soil. The prediction results showed that the proposed method can be used to predict the landslide due to rainfall infiltration by efficiently considering the movement of the saturated region in the hillslope with shallow impermeable bedrock. Acknowledgements This research was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2012M3A2A1050981).
Black tea: chemical analysis and stability.
Li, Shiming; Lo, Chih-Yu; Pan, Min-Hsiung; Lai, Ching-Shu; Ho, Chi-Tang
2013-01-01
Tea is the most popular flavored and functional drink worldwide. The nutritional value of tea is mostly from the tea polyphenols that are reported to possess a broad spectrum of biological activities, including anti-oxidant properties, reduction of various cancers, inhibition of inflammation, and protective effects against diabetes, hyperlipidemia and obesity. Tea polyphenols include catechins and gallic acid in green and white teas, and theaflavins and thearubigins as well as other catechin polymers in black and oolong teas. Accurate analysis of black tea polyphenols plays a significant role in the identification of black tea contents, quality control of commercial tea beverages and extracts, differentiation of various contents of theaflavins and catechins and correlations of black tea identity and quality with biological activity, and most importantly, the establishment of the relationship between quantitative tea polyphenol content and its efficacy in animal or human studies. Global research in tea polyphenols has generated much in vitro and in vivo data rationally correlating tea polyphenols with their preventive and therapeutic properties in human diseases such as cancer, and metabolic and cardiovascular diseases etc. Based on these scientific findings, numerous tea products have been developed including flavored tea drinks, tea-based functional drinks, tea extracts and concentrates, and dietary supplements and food ingredients, demonstrating the broad applications of tea and its extracts, particularly in the field of functional food.