Online ISSN
1751-8652
Print ISSN
1751-8644
IET Control Theory & Applications
Volume 1, Issue 4, July 2007
Volumes & issues:
Volume 1, Issue 4
July 2007
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- Author(s): S. Drid ; M. Tadjine ; M.-S. Naït-Saïd
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 861 –868
- DOI: 10.1049/iet-cta:20060053
- Type: Article
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p.
861
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(8)
A robust vector control intended for a doubly fed induction motor (DFIM) mode is considered. The state-all-flux induction machine model with a flux orientation constraint is replaced by a simpler control model. The double-flux orientation leads to orthogonality between the stator and rotor fluxes, resulting in a linear and decoupled machine control and an optimal developed torque. The inner flux controllers are designed using the Lyapunov linearisation approach. This flux control is exponentially stabilised independently of the speed. Associated with sliding-mode control, this solution shows good robustness with respect to parameter variations, measurement errors and noisse. Finally, a speed controller is designed using two methods: the first with a PI controller and the second with the Lyapunov method associated with a backstepping procedure, especially employed for the unknown load torques. This second solution shows good robustness with respect to inertia variation and guarantees torque and speed tracking. The global asymptotic stability of the overall system is proven theoretically. The simulation and experimental results largely confirm the effectiveness of the proposed DFIM system control. - Author(s): H.H. Choi
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 869 –874
- DOI: 10.1049/iet-cta:20060142
- Type: Article
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869
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The sliding-surface design problem for unmatched uncertain systems is considered. In the literature, it has been shown that if a system with unmatched uncertainties satisfies an invariance condition, then there exists a linear switching surface such that the sliding-mode dynamics restricted to the switching surface are not only stable but completely invariant to unmatched uncertainties. Frequency domain interpretations of the invariance condition of the sliding-mode control theory are given. It is shown that a certain H∞-norm bound constraint should be satisfied in order to guarantee the invariance condition. It is also shown that the invariance condition is guaranteed for any unmatched uncertainties satisfying a certain minimum phase condition. These results can be used to efficiently design a sliding surface. Finally, the effectiveness of the results is verified via some numerical design examples. - Author(s): C.-C. Hua ; X.-P. Guan ; G. Feng
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 875 –879
- DOI: 10.1049/iet-cta:20060404
- Type: Article
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875
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The state-feedback control problem for a class of time-delay systems is investigated. The considered nonlinear systems have a triangular structure. By constructing a novel Lyapunov–Krasovskii functional, an adaptive state-feedback controller is designed via a backstepping method. The resulting closed-loop system is proved to be stable in the sense of uniform ultimate boundedness. Simulations are performed to verify the effectiveness of the proposed method. - Author(s): N. Wang ; W. Xu ; F. Chen
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 880 –886
- DOI: 10.1049/iet-cta:20060193
- Type: Article
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880
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A new output-feedback sliding-mode control scheme is proposed to deal with a class of relative-degree-2 uncertain linear systems. The controller is composed of linear filters and a single relay, without any real-time differentiators employed. Based on a specific characteristic of singularly perturbed sliding-mode systems, robust stabilisation, disturbance attenuation and asymptotic output tracking are also realised. Simulations show the simplicity and efficiency of this method. - Author(s): Y.X. Yao and A.V. Radun
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 887 –892
- DOI: 10.1049/iet-cta:20060257
- Type: Article
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887
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A robust proportional integral (PI) observer design for time-delay systems is proposed. It is based on the factorisation approach for time-delay systems. A PI observer in the general form is used. The existence condition for all PI observers is obtained. The parameterisation for all PI observers and their error dynamics for time-delay systems are given. It is indicated that the proposed PI observer is composed of an identity PI state observer and a disturbance signal attenuator. A systematic design procedure for a robust PI observer is presented. - Author(s): S.K. Nguang ; W. Assawinchaichote ; P. Shi
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 893 –908
- DOI: 10.1049/iet-cta:20060369
- Type: Article
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893
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(16)
Examination is made of the problems of designing robust ℋ∞ state-feedback and output feedback controllers for a class of uncertain Markovian jump nonlinear singularly perturbed systems described by a Takagi–Sugeno fuzzy model with Markovian jumps. Based on the linear matrix inequality (LMI) approach, LMI-based sufficient conditions for the uncertain Markovian jump nonlinear singularly perturbed systems to have an ℋ∞ performance are derived. To alleviate the ill-conditioning resulting from the interaction of slow and fast dynamic modes, solutions to the problems are given in terms of linear matrix inequalities that are independent of the singular perturbation ɛ, when ɛ is sufficiently small. The proposed approach does not involve the separation of states into slow and fast ones and it can be applied not only to standard, but also to nonstandard nonlinear singularly perturbed systems. A numerical example is provided to illustrate the design developed in this paper. - Author(s): Y.-J. Kim and M.-T. Lim
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 909 –914
- DOI: 10.1049/iet-cta:20050479
- Type: Article
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909
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A new algorithm for the closed-loop parallel optimal control of weakly coupled bilinear systems with respect to performance criteria using the successive Galerkin approximation (SGA) is presented. From the spirit of the general weak coupling theory, the Hamilton–Jacobi–Bellman equation (HJB: which is related to optimal control problems) is decomposed into three independent HJB equations. The optimal control law consists of the solutions to sub-equations using the SGA method in parallel. The main contributions are as follows: (i) design of a closed-loop optimal control law for weakly coupled bilinear systems using the SGA method and (ii) reduction of the computational complexity when the SGA method is applied to the high-order systems. - Author(s): F.U. Rehman and M.M. Ahmed
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 915 –924
- DOI: 10.1049/iet-cta:20060189
- Type: Article
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915
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The authors present a simple steering control algorithm for a class of non-holonomic wheeled mobile robots. Five different types of wheeled mobile robots are considered. The feedback controls are piece-wise constant, states dependent and the method is based on the construction of a cost function V, which is sum of two semi-positive definite functions V1 and V2. The first m state variables can be steered along the given vector fields directly using the classical controls and remaining n–m state variables can be steered along the missing Lie brackets indirectly. The task of the control strategy is to decay the non-differentiable cost function along the controlled system trajectories only asymptotically. The beauty of the algorithm is that it does not require the conversion of the system models into ‘chained form’ and does not rely on any special transformation techniques. - Author(s): F.N. Chowdhury and W. Chen
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 925 –932
- DOI: 10.1049/iet-cta:20060274
- Type: Article
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p.
925
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An effective control system is typically expected to possess the capability of maintaining specified system performance despite changes in system parameters (faults). In some design strategies, this implies that the ‘faults’ are automatically ‘tolerated’ without being explicitly detected. On the other hand, early fault detection is a basic requirement of a fault diagnosis system, which is necessary for the long-term reliability of engineering systems. In order to achieve both effective control and long-term reliability, we propose a combined strategy, using separate loops for control and fault detection. A simulation example shows the effectiveness of the proposed scheme. - Author(s): D.Y. Chao
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 933 –936
- DOI: 10.1049/iet-cta:20060275
- Type: Article
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Current deadlock control approaches for S3PGR2 (systems of simple sequential processes with general resources requirement) suffer from incorrect or restricted liveness characterisation based on the concept of deadly marked siphons (DMSs) or max-controlled siphons have been demonstrated. Non-live transitions may exist when there are no DMSs. It is live when all siphons are max-controlled – restricted since it may be live when not max-controlled. We replace it with a new liveness condition called max'-controlled siphons. - Author(s): Y. Choi
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 937 –945
- DOI: 10.1049/iet-cta:20050512
- Type: Article
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937
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The PID (proportional-integral-derivative) state estimator to make an output feedback PID controller is suggested for Lagrangian systems. When an inverse optimal PID controller (full state feedback) is utilised with a PID state estimator, an output feedback PID control system recovers the extended disturbance input-to-state stability like a full state feedback PID control system, if only one condition for an estimator gain parameter is satisfied. The condition is derived from the stability proof and it depends only on the proportional gain value among the gains in the PID controller. Also, the performance of the suggested PID state estimator can be predicted by the proportional relation between the size of estimation error and the square of the estimator gain parameter. - Author(s): J. Zhou
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 946 –954
- DOI: 10.1049/iet-cta:20050382
- Type: Article
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First, the harmonic Lyapunov equations claimed on the Hilbert space l2 are restricted to the Banach space l1 for asymptotic stability of finite-dimensional linear continuous-time periodic (FDLCP) systems. Second, solutions to the harmonic Lyapunov equations are scrutinised. Third, the harmonic Lyapunov equations are connected with periodic matrix differential (PMD) Lyapunov equations. The connection sheds new light on periodic solutions to the PMD Lyapunov equations. Fourth, the trace formula of the H2 norm for FDLCP systems is shaped with periodic solutions to the PMD Lyapunov equations. Finally, an algorithm for computing periodic solutions to the PMD Lyapunov equations is proposed, which involves only solutions to algebraic Lyapunov equations. There are numerical examples to illustrate the results. - Author(s): Z. Li ; J. Zhang ; M. Zhao
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 955 –967
- DOI: 10.1049/iet-cta:20060218
- Type: Article
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955
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The importance of siphons is well recognised in the analysis and control of deadlocks in Petri nets. Deadlock prevention problems are considered for S4PR, a class of generalised Petri nets, that can model well a large class of flexible manufacturing systems (FMS). Siphons in a plant net model are divided into elementary and dependent ones. Deadlock prevention is achieved by adding monitors (control places) to make every elementary siphon satisfy the maximal controlled-siphon property. Conditions are developed under which a dependent siphon is maximally controlled when its elementary siphons are so. The max-controllability of a dependent siphon is ensured by properly supervising the control depth variables of its elementary siphons via linear integer programming techniques. Compared with existing methods, this policy requires a much smaller number of supervisory monitors. Finally, the application of this approach is illustrated by an FMS example. - Author(s): J. Wang ; P. Houlis ; V. Sreeram ; W. Liu
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 968 –974
- DOI: 10.1049/iet-cta:20050406
- Type: Article
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A new model reduction method, based on frequency fitting, is proposed for single-input discrete-time singular (non-causal) systems. The reduced-order models are obtained by minimising the least square frequency response error between the original system and the reduced-order model. Finally, the method is illustrated by a numerical example and is compared with other related techniques. - Author(s): A.-G. Wu ; G.-R. Duan ; Y. Zhao ; H.-H. Yu
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 975 –978
- DOI: 10.1049/iet-cta:20060366
- Type: Article
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In terms of the original system matrices, a new criterion is given for the I-controllablisability of descriptor linear systems. The range of the dynamical orders that the resultant closed-loop system can achieve is also characterised. A general parameterisation of all the I-controllablising controllers that make the resultant closed-loop system have the desired dynamical order is presented. The design is based on orthogonal matrix transformations that can be implemented in a numerically stable way. - Author(s): L.-H. Chang and A.-C. Lee
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 979 –986
- DOI: 10.1049/iet-cta:20060338
- Type: Article
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979
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This study presents the use of Tustin's friction model and a disturbance observer to improve the steady-state error of a bi-axial inverted pendulum system. Then, a three-phase controller, including a swing-up control, a sliding-mode with feedback linearisation to control the angle of the pendulum, and a sliding-mode plus PID control for the pendulum-cart system is employed to eliminate the system's nonlinear and unstable characteristics. Experimental results reveal that the pendulum maximum angle of operation is ±14°(X-axis)/±12° (Y-axis); the steady-state error of the pendulum angle is ±0.2° (X-axis)/±0.3°(Y-axis), and the cart position is within±4 mm. Experimental results are illustrated and films are provided at the website http://midistudio.myweb.hinet.net to show the effectiveness and robustness of the proposed control schema. - Author(s): S. Bogosyan ; M. Barut ; M. Gokasan
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 987 –998
- DOI: 10.1049/iet-cta:20060329
- Type: Article
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p.
987
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(12)
An extended Kalman filter (EKF)-based estimation approach is developed for the simultaneous estimation of rotor (Rr) and stator (Rs) resistances, the uncertainties of which are commonly known to cause problems in flux and velocity estimation for sensorless control over a wide speed range. The proposed ‘braided’ EKF approach is based on the consecutive operation of two EKF algorithms running in turn, at each sampling interval and is the first reported study in induction motor sensorless control achieving the accurate estimation of Rs, Rr, which is reported as a challenge in the literature. The braided-EKF also improves the estimation of flux and velocity over a wide range, including persistent operation at zero speed. The proposed algorithm is tested with simulations and experiments at high, low and zero speed under challenging load torque, velocity and Rs, Rr variations. A significant improvement is achieved over conventional single EKF schemes and compatible, if not better results are obtained with previously reported sensorless estimation methods, with no need for signal injection or for different algorithms for different parameters and speed ranges. - Author(s): S.M. Lee and S.C. Won
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 999 –1007
- DOI: 10.1049/iet-cta:20060203
- Type: Article
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p.
999
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Robust model predictive control technique is proposed for constrained nonlinear systems are modelled as systems with sector-bounded nonlinearities. The controller design problem is formulated as a minimisation of the upper bound of a finite-horizon cost function subject to cost monotonicity. For cost monotonicity, a linear matrix inequality (LMI) condition for terminal inequality is derived using a parameter-dependent terminal weighting matrix. The optimisation problem that satisfies the terminal inequality is solved by semidefinite programming involving LMIs. Numerical examples are included to illustrate the effectiveness of the proposed method. - Author(s): H.-S. Ahn and Y.Q. Chen
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1008 –1014
- DOI: 10.1049/iet-cta:20060172
- Type: Article
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1008
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The state-dependent nonlinear external disturbance compensation problem is considered. No prior information about the disturbance is assumed except the periodicity of the disturbance with respect to a state variable, which is termed a ‘state-dependent periodic disturbance.’ The key idea of the proposed new adaptive compensation method is to make use of this known state-dependent periodicity. In the first period, an adaptive compensator is designed to guarantee the ℒ2-stability of the overall system. From the second period and onwards, a state-periodic adaptive compensator is designed to stabilise the system by using the information stored in the previous period. The Lyapunov stability analysis is performed on the evolution along the trajectory axis. The validity of the proposed state-periodic adaptive control method is illustrated through a simulation example. - Author(s): L. Liu and D.A. Cartes
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1015 –1022
- DOI: 10.1049/iet-cta:20060065
- Type: Article
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1015
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High power and high performance applications of permanent magnet synchronous motors (PMSM) are increasing. PMSM models with accurate parameters are required for precise control and fault diagnostic systems. An adaptive synchronisation based parameter identification method for the PMSM with a nonlinear structure is proposed. During the identification, the PMSM's dynamic response is synchronised with another system of similar dynamic structure. The algorithm is different from the commonly known adaptive estimator. A globally converged feedback control is applied to the reference model. Lyapunov function analysis and LaSalle's invariance principle are used to assure performance. To validate the proposed identification approach, both simulation and experiments are performed for the identification of motor parameters in a PMSM servo system. During experiments, the method is further improved to counteract voltage measurement problems brought by high frequency switching devices. The results demonstrate the effectiveness of this approach. - Author(s): S. Wu and L. Hong
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1023 –1032
- DOI: 10.1049/iet-cta:20060034
- Type: Article
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1023
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When traditional single-point target tracking algorithms are directly applied to multiple-point rigid targets, filter divergence and data association problems occur. By introducing the concepts of global motion, local motion and structure parameters, and employing motion-induced invariants on local motion and structure parameters, we have developed several kinematic and measurement models to simultaneously estimate the motion and structure information of a 3D rigid-body target from high range resolution (HRR) and ground moving target indicator (GMTI) measurements. To test the ability of the proposed modelling methods in handling false alarms, occlusions and HRR measurements without correspondence information, several data association approaches are also proposed, that is permutation, combination-permutation, dummy measurements, and dynamically changing the interested number of scattering centres. Simulation results have shown that the proposed modelling methods can successfully estimate both the motion and structure information of an object by using HRR and GMTI measurements with a proper data association method. - Author(s): E.I. Silva ; D.A. Oyarzún ; M.E. Salgado
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1033 –1045
- DOI: 10.1049/iet-cta:20050515
- Type: Article
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This paper discusses optimal control problems in which the controller must satisfy sparsity structure constraints. Conditions are derived under which the optimal controller associated to an unconstrained quadratic performance index is naturally structured and, as a consequence, the sparsity constraint imposed on the controller has no impact on the optimal loop performance. The results are then applied to study the control of triangular plants that have to be controlled by triangular controllers. We derive explicit characterisations of the Youla parameter that defines an optimal triangular controller and of the performance loss associated to the structural restriction imposed on the controller. - Author(s): S.M. Mahdi Alavi ; A. Khaki-Sedigh ; B. Labibi ; M.J. Hayes
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1046 –1053
- DOI: 10.1049/iet-cta:20060378
- Type: Article
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An improved design procedure for multi-input/multi-output (MIMO) quantitative feedback theory (QFT) problems involving tracking error specifications (TESs) has been presented. Appropriate transformation of the MIMO system to a series of equivalent single-input/single-output (SISO) problems is presented that motivates an improved synthesis procedure using feedback compensator and pre-filter transfer function matrices (TFMs). The key features of the procedure are that, for each equivalent SISO problem, (i) interactions and the effects of uncertainty are treated as an output disturbance, and (ii) sufficient conditions can be determined that assure desired levels of robust performance within the bandwidth region at a transformation cost that can be computed a priori. This paper also considers how the individual elements of the pre-filter TFM can be designed for MIMO QFT problems with a reduced level of conservatism and over-design using existing SISO methods. A benchmark quadruple-tank process is considered to illustrate the benefits of the new design paradigm. - Author(s): S. Sivrioglu
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1054 –1059
- DOI: 10.1049/iet-cta:20050473
- Type: Article
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This research aims to test the limits of control effectiveness for an active magnetic bearing (AMB) system subjected to external acceleration disturbances. An adaptive output backstepping controller is designed to compute nonlinear control currents of the magnetic bearing by accepting that the rotor and AMB parameters are unknown. The control currents of the electromagnets of the active magnetic bearing is switched according to the rotor position. The adaptive backstepping controller is experimentally verified in an AMB test system with vibrating base and the results are compared with proportional integrative derivative (PID) control results for the maximum amplitude of applicable disturbance. - Author(s): X.-Z. Dong
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1060 –1067
- DOI: 10.1049/iet-cta:20060173
- Type: Article
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The problem of strictly dissipative control for discrete singular systems with or without parameter uncertainties is focused. A necessary and sufficient condition in terms of linear matrix inequalities (LMIs) is derived guaranteeing the admissibility and strict dissipativeness of a linear discrete singular system. Then, the existence condition of a state feedback strictly dissipative controller is given by using matrix inequalities (MIs). As for an uncertain discrete singular system, the uncertainties are assumed to be time-invariant and norm-bounded appearing in both the state and input matrices. A sufficient condition is obtained such that the uncertain system is generalised quadratically stable and strictly dissipative. Moreover, a state feedback robust strictly dissipative controller is also constructed by using the solution of MIs. - Author(s): D.-J. Wang
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1068 –1074
- DOI: 10.1049/iet-cta:20060322
- Type: Article
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A new synthesis procedure of PID (proportional-integral-derivative) controllers for nth-order all pole plants with dead-time is developed via a parameter space approach. A necessary and sufficient condition-based graphical stability criterion is applied to determine the complete stabilising regions of PID controllers. First, the admissible stabilising range of the proportional-gain is derived in terms of a version of the Hermite–Beihler theorem applicable to quasi-polynomials. Then, the boundaries of the stabilising region in the integral-derivative plane are drawn directly, not calculated mathematically, for a fixed value of proportional-gain in the stabilising range. An algorithm for determining the stabilising parameter set of the PID controller is also proposed. Finally, numerical examples are given to show the shapes of the stabilising regions of the PID controllers for different order plants with dead-time. - Author(s): H. Huang and D.W.C. Ho
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1075 –1085
- DOI: 10.1049/iet-cta:20060313
- Type: Article
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The problem of delay-dependent robust fuzzy control for stochastic nonlinear systems with parameter uncertainties and time-varying delay is considered. A generalised Takagi-Sugeno fuzzy model is introduced to represent a stochastic nonlinear system in which the consequent parts are composed of a set of uncertain stochastic time-varying delay systems. Delay-dependent stability criterion is first obtained such that for all admissible uncertainties, the overall fuzzy system is asymptotically stable in the mean square. Then, based on the stability criterion and the parallel distributed compensation scheme, a state feedback fuzzy controller is proposed to guarantee the asymptotical stability in the mean square for the closed-loop system. These conditions are expressed in terms of linear matrix inequalities, and are dependent on the size of the time delay and on the size of the derivative of time delay. Finally, a simulation example is given to illustrate the effectiveness of the developed method. - Author(s): S. Ma ; Z. Cheng ; C. Zhang
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1086 –1095
- DOI: 10.1049/iet-cta:20060131
- Type: Article
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The robust stability and robust stabilisation problems for time-varying delay discrete singular systems with parameter uncertainties are discussed. A delay-dependent linear matrix inequality (LMI) condition to enable time-varying delay discrete standard state-space systems to be stable is given. Based on this condition and the restricted system equivalent transformation, the delay-dependent LMI condition is proposed for the time-varying delay discrete singular systems to be admissible. With this condition, the problems of robust stability and robust stabilisation are solved, and the delay-dependent LMI conditions are obtained. Numerical examples illustrate the effectiveness of the proposed method. - Author(s): H.-Y. Chung ; S.-M. Wu ; F.-M. Yu ; W.-J. Chang
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1096 –1103
- DOI: 10.1049/iet-cta:20060227
- Type: Article
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The design of a static output feedback fuzzy controller for nonlinear systems based on Takagi–Sugeno (T–S) fuzzy models is addressed. To avoid complex mathematical derivations and conservative results, a genetic algorithm (GA) is integrated with a linear matrix inequality (LMI) optimisation to seek the static output feedback gains that satisfy the Lyapunov stability inequalities with a decay rate constraint. To do so, the fitness function of the GA must be made up of constraints that are derived from some fundamental control theories, the Lyapunov stability criteria and LMI solver. To improve the computational efficiency of the GA and LMI solver, a fitness function, called the hierarchical fitness function structure, is built on a hierarchical structure such that the GA can in turn deal with stability inequalities. The relaxed syntheses of static output feedback fuzzy control are then easy to implement without using complex mathematical derivations. - Author(s): P.-K. Huang ; P.-H. Shieh ; F.-J. Lin ; H.-J. Shieh
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1104 –1113
- DOI: 10.1049/iet-cta:20060371
- Type: Article
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A sliding-mode controller (SMC) for a two-dimensional piezo-positioning stage is proposed. A mathematical model representing the motion dynamics of the stage is developed in which a hysteresis friction force describing the hysteresis behaviour of one-dimensional motion is used and a non-contant stiffness with the cross-coupling dynamics due to the effect of bending of lever mechanism in the x and y axes is also included. Based on the dynamic model, the proposed SMC with an asymptotic sliding surface is designed. A stability anslysis is performed, and the transient performance is governed by the choice of control parameter values. With the proposed control scheme, the piezo-positioning stage is suitable for practical applications, especially in microscopy, with its need for validity of various trajectories. Experimental results show that the proposed controller provides high-performance dynamic characteristics and robustness to external load. - Author(s): İ. Polat ; E. Eşkinat ; İ.E. Köse
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1114 –1121
- DOI: 10.1049/iet-cta:20060326
- Type: Article
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A methodology for controlling nonlinear mechanical systems expressed in non-singular parametric descriptor quasi-linear parameter varying form is developed. For mechanical systems, this form is naturally obtained through the Lagrangian formulation. Use of this form avoids the explicit inversion of the mass matrix, thus eliminating the additional resulting linear fractional parameter dependence complexity. Parametric Lyapunov functions are used for the design. Sufficient conditions for the stability and dynamic output feedback control with guaranteed induced ${\cal L}_2$-norms from the disturbance to the controlled output are given. The conditions for the reduction of the solvability conditions to finite-dimensional linear matrix inequalities are provided. The results are shown on a two-link flexible manipulator example. - Author(s): J.L. Douce ; W.D. Widanage ; K.R. Godfrey
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1122 –1130
- DOI: 10.1049/iet-cta:20060333
- Type: Article
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The relationships between the magnitude and phase of the frequency response of a stable linear minimum phase system have been examined by several authors, including Bode, and they prove valuable in the design of a wide range of systems. It is shown that direct application of the expressions to estimate either the phase response from a known gain response, or the gain response from a known phase response, can lead to rather inaccurate results. It is also shown that the accuracy can be significantly improved using appropriate extrapolation of the relevant expressions and functions at high and low frequencies. A range of numerical examples demonstrates the improved accuracy as the extrapolation process is refined, and provides a comparison with the situation where the initial given data are not limited in bandwidth. - Author(s): X. Jiang and Q.-L. Han
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1131 –1140
- DOI: 10.1049/iet-cta:20060238
- Type: Article
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The problem of H∞ filter design for linear systems with interval time-varying delay is investigated. The interval time-varying delay is considered as two cases: continuous and differentiable with the bounded derivative of the time-varying delay. Neither model transformation nor bounding techniques for cross terms is employed. A delay-dependent sufficient condition on the existence of an H∞ filter is derived in the form of non-convex matrix inequalities by introducing a new Lyapunov–Krasovskii functional which is based on both left and right endpoints of the time-varying delay interval. In order to find a feasible solution to the non-convex matrix inequalities, a minimisation problem is formulated and the problem can be solved by using a cone complementarity. Finally, two examples are given to illustrate the effectiveness of the proposed method. - Author(s): J. Dong and G.-H. Yang
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1141 –1148
- DOI: 10.1049/iet-cta:20060234
- Type: Article
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The state feedback H∞ control problem for standard discrete-time singularly perturbed systems with polytopic uncertainties is considered. Two methods for designing H∞ controllers are given in terms of solutions to a set of linear matrix inequalities, where one of them is with the consideration of improving the upper bound of singular perturbation parameter ε. Moreover, a method of evaluating the upper bound of singular perturbation parameter ε with meeting a prescribed H∞ performance bound requirement is also given. Numerical examples are given to illustrate the effectiveness of the proposed methods. - Author(s): X. Hong and R.J. Mitchell
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1149 –1159
- DOI: 10.1049/iet-cta:20060018
- Type: Article
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A new identification algorithm is introduced for the Hammerstein model consisting of a nonlinear static function followed by a linear dynamical model. The nonlinear static function is characterised by using the Bezier–Bernstein approximation. The identification method is based on a hybrid scheme including the applications of the inverse of de Casteljau's algorithm, the least squares algorithm and the Gauss–Newton algorithm subject to constraints. The related work and the extension of the proposed algorithm to multi-input multi-output systems are discussed. Numerical examples including systems with some hard nonlinearities are used to illustrate the efficacy of the proposed approach through comparisons with other approaches. - Author(s): F. Tao and Q. Zhao
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1160 –1168
- DOI: 10.1049/iet-cta:20050492
- Type: Article
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In this paper active fault-tolerant control (FTC) is designed in a stochastic framework. The fault-tolerant control system (FTCS) is formulated as a set of linear systems governed by two continuous-time finite-state Markov chains, which are used to characterise the system failure modes and the fault detection and isolation (FDI) scheme. This framework is widely accepted for stability analysis of FTCS; however, the design of a controller only accessing the FDI mode is still a challenging problem. We solve this synthesis problem by using convex optimisation techniques. First, a sufficient condition for the mean exponential stability is given in terms of a linear matrix inequality (LMI). The results are then extended to uncertain systems design for stability and in system performance using a stochastic integral quadratic constraint. Due to the complexity of the problem, the controller is obtained using the iterative LMI technique. - Author(s): Y. Xia ; G.P. Liu ; P. Shi ; J. Chen ; D. Rees ; J. Liang
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1169 –1175
- DOI: 10.1049/iet-cta:20060479
- Type: Article
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The problem of sliding-mode control is investigated for a class of uncertain linear systems with input-delay in discrete time. First, a predictor in discrete time is introduced, which converts the original system with input delay to an equivalent system without the explicit appearance of time delay and makes the control problem solvable. Then, sliding-mode controls are constructed for both systems with and without bounded disturbance. Simulation studies show the effectiveness of the control scheme. - Author(s): A.H. Besheer ; H.M. Emara ; M.M. Abdel Aziz
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1176 –1185
- DOI: 10.1049/iet-cta:20060217
- Type: Article
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The problem of robustly stabilising a class of nonlinear systems using an H∞ fuzzy observer-based controller is considered. A class of nonlinear systems is approximated by a Takagi–Sugeno fuzzy model. A sufficient condition is derived to ensure the robust stability of the fuzzy observer-based controller with guaranteed H∞ disturbance attenuation level. The observer and controller design problem is cast in the form of bilinear matrix inequalities (BMIs). Using a two-step procedure, these BMIs are reduced to two sets of linear matrix inequalities that can be solved very efficiently using convex optimisation techniques. The proposed design procedure extends previous results by considering both the premise uncertainty and the consequent uncertainty simultaneously. Furthermore, a modified two-step procedure is suggested for plants with linear output equation. Finally, a simulation example illustrates the validity and applicability of the given approach. - Author(s): B.L. Ma
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1186 –1187
- DOI: 10.1049/iet-cta:20060495
- Type: Article
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- Author(s): A. Dhawan and H. Kar
- Source: IET Control Theory & Applications, Volume 1, Issue 4, p. 1188 –1190
- DOI: 10.1049/iet-cta:20060327
- Type: Article
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Robust backstepping vector control for the doubly fed induction motor
Frequency domain interpretations of the invariance condition of sliding mode control theory
Robust stabilisation for a class of time-delay systems with triangular structure
Output-feedback second-order sliding-mode control of uncertain linear systems with relative degree 2
Proportional integral observer design for linear systems with time delay
Robust ℋ∞ control design for fuzzy singularly perturbed systems with Markovian jumps: an LMI approach
Parallel optimal control for weakly coupled bilinear systems using successive Galerkin approximation
Steering control algorithm for a class of wheeled mobile robots
A dual-loop scheme for fault-tolerance and early fault detection
Max'-controlled siphons for liveness of S3PGR2
PID state estimator for Lagrangian systems
Harmonic Lyapunov equations in continuous-time periodic systems: solutions and properties
Liveness-enforcing supervisor design for a class of generalised petri net models of flexible manufacturing systems
Optimal model reduction of non-causal systems via least squares frequency fitting
A revisit to I-controllablisability for descriptor linear systems
Design of nonlinear controller for bi-axial inverted pendulum system
Braided extended Kalman filters for sensorless estimation in induction motors at high-low/zero speed
Robust constrained predictive control using a sector bounded nonlinear model
State-dependent periodic adaptive disturbance compensation
Synchronisation based adaptive parameter identification for permanent magnet synchronous motors
Modelling 3D rigid-body object motion and structure estimation with HRR/GMTI measurements
On structurally constrained ℋ2 performance bounds for stable MIMO plant models
Improved multivariable quantitative feedback design for tracking error specifications
Adaptive backstepping for switching control active magnetic bearing system with vibrating base
Robust strictly dissipative control for discrete singular systems
Stabilising regions of PID controllers for nth-order all pole plants with dead-time
Delay-dependent robust control of uncertain stochastic fuzzy systems with time-varying delay
Delay-dependent robust stability and stabilisation for uncertain discrete singular systems with time-varying delays
Evolutionary design of static output feedback controller for Takagi–Sugeno fuzzy systems
Sliding-mode control for a two-dimensional piezo-positioning stage
Dynamic output feedback control of quasi-LPV mechanical systems
Evaluation of the relationship between gain and phase using extrapolation techniques
Delay-dependent H∞ filter design for linear systems with interval time-varying delay
Robust H∞ control for standard discrete-time singularly perturbed systems
Hammerstein model identification algorithm using Bezier–Bernstein approximation
Synthesis of active fault-tolerant control based on Markovian jump system models
Sliding mode control of uncertain linear discrete time systems with input delay
Fuzzy-based output-feedback H∞ control for uncertain nonlinear systems: an LMI approach
Comment: Design of a stable sliding-mode controller for a class of second-order underactuated systems
Comment: Robust optimal guaranteed cost control for 2D discrete systems
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