Online ISSN
1751-8652
Print ISSN
1751-8644
IET Control Theory & Applications
Volume 4, Issue 8, August 2010
Volumes & issues:
Volume 4, Issue 8
August 2010
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- Author(s): D. Simon
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1303 –1318
- DOI: 10.1049/iet-cta.2009.0032
- Type: Article
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p.
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The Kalman filter is the minimum-variance state estimator for linear dynamic systems with Gaussian noise. Even if the noise is non-Gaussian, the Kalman filter is the best linear estimator. For nonlinear systems it is not possible, in general, to derive the optimal state estimator in closed form, but various modifications of the Kalman filter can be used to estimate the state. These modifications include the extended Kalman filter, the unscented Kalman filter, and the particle filter. Although the Kalman filter and its modifications are powerful tools for state estimation, we might have information about a system that the Kalman filter does not incorporate. For example, we may know that the states satisfy equality or inequality constraints. In this case we can modify the Kalman filter to exploit this additional information and get better filtering performance than the Kalman filter provides. This paper provides an overview of various ways to incorporate state constraints in the Kalman filter and its nonlinear modifications. If both the system and state constraints are linear, then all of these different approaches result in the same state estimate, which is the optimal constrained linear state estimate. If either the system or constraints are nonlinear, then constrained filtering is, in general, not optimal, and different approaches give different results. - Author(s): M. Cea and M.E. Salgado
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1319 –1329
- DOI: 10.1049/iet-cta.2008.0582
- Type: Article
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p.
1319
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This study deals with achievable performance bounds in the control of multivariable systems having a high degree of sparsity. The systems to be considered are square, linear, stable, time-invariant and discrete-time, and it is assumed that they can be reasonably described by a matrix transfer function, which is diagonal plus one or two off-diagonal elements. The performance is quantified using the 2-norm of the weighted loop sensitivity. The starting point is the achievable performance bound for the decentralised control of a diagonal model. Then, under the assumption that an available sparse model is a better model for the plant, the new achievable performance bound is calculated based on this latter model. With these results, the significance of basing the control design on a model which is more complex than the diagonal one, is assessed. - Author(s): D.V. Dimarogonas and K.H. Johansson
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1330 –1338
- DOI: 10.1049/iet-cta.2009.0229
- Type: Article
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1330
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A distributed control law that guarantees connectivity maintenance in a network of multiple mobile agents is presented. The control law, which lets the agents perform formation manoeuvres, respects sensor limitations by allowing each agent to only take into account agents within its sensing radius. In contrast to previous approaches to the problem, the proposed control law does not attain infinite values whenever an edge of the communication graph tends to be lost. This is achieved via the use of decentralised navigation functions, which are bounded potential fields. The navigation functions are defined to take into account the connectivity maintenance objective. The authors first treat the case of connectivity maintenance for a static communication graph and then extend the result to the case of dynamic graphs. The results are illustrated on a formation control problem. - Author(s): W.-W. Che ; J.-L. Wang ; G.-H. Yang
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1339 –1352
- DOI: 10.1049/iet-cta.2009.0120
- Type: Article
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1339
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(14)
This study is concerned with the quantised H∞ filtering problem for discrete-time systems subject to limited communication capacity, which includes measurement quantisation and random sensor packet losses. By introducing an improved quantised random packet-loss model, the effects of the packet-loss rate and the upper bound of consecutive packet losses and the quantisation on the system performance are considered simultaneously. A quantised H∞ filter design strategy with the minimised static quantiser range is designed to guarantee the error system exponentially mean-square stable and also achieve the prescribed H∞ disturbance attenuation level. A numerical example is given to illustrate the effectiveness of the proposed filter design method. - Author(s): L. Menini and A. Tornambè
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1353 –1365
- DOI: 10.1049/iet-cta.2009.0177
- Type: Article
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p.
1353
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(13)
The Bullard dynamo and the Rikitake system are two well-known non-linear systems, which are used to capture the main aspects of the magnetic field of the Earth, especially those non-linear and chaotic. Aim of this study is two-fold: the review, on the basis of the modern differential geometry, of the dynamical aspects of both systems, and the design, on the basis of the modern geometric control theory, of dynamical algorithms for the estimation of the state variables, which is a challenging problem because of the chaotic behaviour presented by both systems. All the analyses are validated in simulation. - Author(s): J.-H. She ; M. Wu ; Y.-H. Lan ; Y. He
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1366 –1376
- DOI: 10.1049/iet-cta.2008.0420
- Type: Article
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p.
1366
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A low-pass filter is inserted in a repetitive controller to guarantee the stability of the modified repetitive-control system. The control precision strongly depends on the parameter of the filter. This study presents a method of simultaneously optimising the parameters of the low-pass filter and state feedback of a modified repetitive-control system in which the plant contains a class of uncertainties. First, the relationship between the control precision of a repetitive-control system and a low-pass filter is explained. Next, a linear matrix inequality (LMI)-based robust-stability condition is derived for fixed state-feedback gains. This condition is transformed into a generalised eigenvalue problem and is used to calculate the maximum cut-off angular frequency of the low-pass filter. Then, another LMI-based robust-stability condition is derived for a fixed low-pass filter, and is employed to find H∞ static-state-feedback gains. Moreover, an iterative algorithm that combines these two robust-stability conditions is designed that yields the largest bandwidth while guaranteeing closed-loop robust stability. The conservativeness of the result produced by the algorithm is the same as that of the less conservative of the two robust-stability conditions. Finally, two numerical examples demonstrate the validity of the method. - Author(s): A.H. González and D. Odloak
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1377 –1390
- DOI: 10.1049/iet-cta.2009.0316
- Type: Article
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p.
1377
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A model predictive controller (MPC) is proposed, which is robustly stable for some classes of model uncertainty and to unknown disturbances. It is considered as the case of open-loop stable systems, where only the inputs and controlled outputs are measured. It is assumed that the controller will work in a scenario where target tracking is also required. Here, it is extended to the nominal infinite horizon MPC with output feedback. The method considers an extended cost function that can be made globally convergent for any finite input horizon considered for the uncertain system. The method is based on the explicit inclusion of cost contracting constraints in the control problem. The controller considers the output feedback case through a non-minimal state-space model that is built using past output measurements and past input increments. The application of the robust output feedback MPC is illustrated through the simulation of a low-order multivariable system. - Author(s): H. Zhang ; L. Xie ; W. Wang
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1391 –1398
- DOI: 10.1049/iet-cta.2008.0448
- Type: Article
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p.
1391
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(8)
This study, the optimal estimation problem for discrete-time systems with time-varying delay in the measurement channel is studied. First, under the assumption that the time-varying delay is of a known upper bound, the delayed measurement can be redescribed as a measurement with multiple state delays. Then the estimation problem is transformed into one for systems with multiple measurement channels that contain the same state information as the original measurement and each channel has single constant delay. Finally, the authors derive the optimal estimator by adopting a reorganised innovation analysis approach. The estimator is designed by performing a number of Riccati difference equations. - Author(s): Z. Liu
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1399 –1406
- DOI: 10.1049/iet-cta.2009.0279
- Type: Article
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p.
1399
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This study investigates the robust variance control problem of neutral systems, taking parameter uncertainties and time delays into account. By introducing algebraic manipulations and appropriate uncertainty descriptions, the purpose of this problem is to design a static-state feedback controller that does not depend on the parameter uncertainties, such that not only the steady-state variance of each state is not more than the individual pre-specified value but also that the resulting closed-loop system is asymptotically stable simultaneously. Using the linear matrix inequality approach, the existence conditions of such controllers are derived. Furthermore, a numerical example is given to illustrate the effectiveness of the proposed approach. - Author(s): L. Seddiki ; K. Guelton ; J. Zaytoon
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1407 –1420
- DOI: 10.1049/iet-cta.2009.0269
- Type: Article
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p.
1407
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The authors consider the kinematic concepts of a new lower-limb rehabilitation device in closed muscular chain. The proposed control structure is based on a trajectory generator and a continuous non-linear tracking controller. The human efforts applied to this device are considered as external disturbances to the system's dynamics and as inputs to the trajectory generator and allow safe voluntary control of the system by the user. A H∞ control structure based on a Takagi–Sugeno descriptor model is proposed to track the desired trajectories and to attenuate external disturbances. Stability conditions are given in terms of linear matrix inequalities using a fuzzy Lyapunov function. Finally, the simulation results of the proposed control structure for the new rehabilitation device during isokinetic movements illustrate the efficiency of the proposed approach. - Author(s): L. Brus ; T. Wigren ; D. Zambrano
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1421 –1435
- DOI: 10.1049/iet-cta.2009.0315
- Type: Article
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p.
1421
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This study discusses non-linear optimal feedforward control of solar collector plants. The control problem is challenging, with non-linear disturbance effects and long input-dependent transport delays. The controller operates in a model-based predictive control framework, without feedback and constraints, to highlight feedforward controller performance gains. To reduce the computational complexity state extension is avoided when modelling the time delays. The motivation for this is provided by a proof of the equivalence between state extension and direct prediction in optimal control, for non-linear multiple-input–multiple-output (MIMO) systems with time delays in disturbances and controls. The solar collector controller also uses flow-dependent sampling to reduce the time variation of the delays. To obtain an accurate model for feedforward controller design, a black-box recursive prediction error identification algorithm was used for modelling of the non-linear plant using measured data. Experimentally, accurate feedforward control was obtained when the controller design was tested with simulation, using measured disturbances from the plant. About two-thirds of the control effort needed appears to be available by feedforward control only. In order to evaluate the algorithms in difficult conditions, the evaluation was performed on data obtained during a day with partly cloudy weather. This caused large flow variations, and consequently large time delay variations. - Author(s): H. Lee and Y. Kim
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1436 –1450
- DOI: 10.1049/iet-cta.2009.0159
- Type: Article
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A sliding mode control scheme with finite reaching time is proposed for a fault-tolerant satellite attitude control system in the presence of actuator faults and external disturbances. The actuator fault is modelled to reflect the degradation of the actuation effectiveness, and the solar array induced disturbance is considered as external disturbance. The control scheme is designed to perform the rest-to-rest manoeuvre of a satellite system with the degradation of the actuation effectiveness, and the stability analysis is performed using the Lyapunov theorem. Numerical simulations are conducted and the results are compared to verify the performance of the proposed fault-tolerant control scheme. - Author(s): J. Cieslak ; D. Henry ; A. Zolghadri
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1451 –1464
- DOI: 10.1049/iet-cta.2009.0146
- Type: Article
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Loss of control accounts for over 25% of aircraft accidents worldwide. This study presents a fault tolerant flight control strategy for increasing aircraft safety. The work has been undertaken within the Action Group on fault tolerant control (FTC) of the European GARTEUR programme, which develops collaborative efforts in Europe to create new FTC technologies that could significantly advance the goals of the aviation safety. After the fault detection and confirmation by the in-flight dedicated systems, a compensation loop is activated to ensure safe recovery. The design of the FTC loop is achieved without any changes in the nominal (and certificated) flight control system (FCS). The FTC scheme design is formulated as an H∞ strong stabilisation problem. Fault compensability is subsequently discussed and formulated as a trim-deficiency analysis problem. The proposed technique is implemented on the SIMONA flight simulator and evaluated through a pilot experiment. The tested scenario corresponds to the landing approach of a large transport aircraft (B747-100/200). The faulty situation is related to trimmable horizontal stabiliser (THS) failures. Piloted flight simulator experiments show that fault tolerance can be achieved under the condition that there exists sufficient remaining control authority. - Author(s): W.U.N. Fernando and S. Kumarawadu
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1465 –1477
- DOI: 10.1049/iet-cta.2009.0144
- Type: Article
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p.
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Discrete time neuro-compensated dynamic state feedback control system for lateral and longitudinal control of intelligent vehicle highway systems (IVHS) is developed. A discrete time counterpart of the continuous time non-linear IHVS model is obtained in state-space form and the controller is analysed in three stages, with and without compensation mechanisms resulting in an implementation from low to high complexity. Gain parameters of the dynamic state feedback control are optimised with respect to a minimisation of a linear quadratic cost function. The weight convergence of the neuro-compensation algorithm is established in discrete time Lyapunov sense via a graphical method. The performance enhancement of each design stage of the controller is presented and compared with the aid of computer simulations.
Kalman filtering with state constraints: a survey of linear and nonlinear algorithms
Performance bounds on the control of highly sparse discrete-time multivariable systems
Bounded control of network connectivity in multi-agent systems
Quantised H∞ filtering for networked systems with random sensor packet losses
Analysis and observer design for the Bullard and Rikitake dynamos
Simultaneous optimisation of the low-pass filter and state-feedback controller in a robust repetitive-control system
Robust model predictive controller with output feedback and target tracking
Optimal estimation for systems with time-varying delay
Robust variance control for a class of uncertain neutral delay systems
Concept and Takagi–Sugeno descriptor tracking controller design of a closed muscular chain lower-limb rehabilitation device
Feedforward model predictive control of a non-linear solar collector plant with varying delays
Fault-tolerant control scheme for satellite attitude control system
Fault tolerant flight control: from theory to piloted flight simulator experiments
Discrete-time neuroadaptive control using dynamic state feedback with application to vehicle motion control for intelligent vehicle highway systems
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- Author(s): E. Tian ; D. Yue ; C. Peng
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1478 –1488
- DOI: 10.1049/iet-cta.2009.0441
- Type: Article
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p.
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This study is concerned with the reliable controller design for networked control systems (NCS) against both probabilistic sensors faults and actuators faults. The faults of each sensor or actuator occur randomly and their failure rates are governed by two sets of unrelated random variables satisfying certain probabilistic distribution. In terms of the probabilistic failures of every sensor or actuator, new type of distribution-based NCS fault model is proposed. Based on the new built model, reliable controller is designed and sufficient conditions for the exponentially mean square stability (EMSS) of NCS are obtained by using Lyapunov functional method. The main contribution of the proposed fault model and methods lies with its practicality and generalisation, which contains many realistic problems in the NCS, such as probabilistic sensors or actuators failures, partial degradation, data distortion, packet dropout, network-induced delay and so on. Moreover, some existing models in the open literatures are deemed as special cases of the proposed fault model. To illustrate the implementation procedure, a vertical take-off and landing (VTOL) aircraft system is given to show the effectiveness and application of the proposed method. - Author(s): S.J. Yoo ; J.B. Park ; Y.H. Choi
- Source: IET Control Theory & Applications, Volume 4, Issue 8, p. 1489 –1500
- DOI: 10.1049/iet-cta.2009.0280
- Type: Article
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An adaptive formation control method is proposed for multiple uncertain non-holonomic mobile robots at the actuator dynamics level. All parameters of the robot kinematics and dynamics, and actuator dynamics are unknown. The virtual structure with path parameters and the dynamic surface design methodology are combined to design a simpler adaptive formation control scheme than the previous backstepping-based control system. Using the Lyapunov stability theorem, the authors present the adaptation laws for tuning all unknown parameters of multiple mobile robots regardless of considering path parameters in the reference trajectories. In addition, it is proved that all signals in the total closed-loop system are semi-globally uniformly bounded and all formation tracking errors and synchronisation errors of the path parameters converge to an adjustable neighbourhood of the origin. Finally, simulation results demonstrate the effectiveness of the proposed approach.
Reliable control for networked control systems with probabilistic sensors and actuators faults
Adaptive formation tracking control of electrically driven multiple mobile robots
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