Online ISSN
1751-8652
Print ISSN
1751-8644
IET Control Theory & Applications
Volume 2, Issue 5, May 2008
Volumes & issues:
Volume 2, Issue 5
May 2008
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- Author(s): M. Vagia and A. Tzes
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 365 –373
- DOI: 10.1049/iet-cta:20070284
- Type: Article
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p.
365
–373
(9)
A robust proportional integral derivative (PID) controller coupled to a feedforward compensator is designed for set-point regulation manoeuvres of an electrostatic micromechanical system. The system is linearised at multiple operating points, and the feedforward compensator provides the nominal voltage. Perturbations around these points are handled from the PID controller, whose gains are tuned via the utilisation of a linear matrix inequality (LMI) approach, which guarantees robustness against the switching nature of the linearised system dynamics. The maximum microspring-stiffness parametric uncertainty that can be tolerated within this scheme, is computed through the use of the small gain theorem. Simulation studies are presented that proves the efficacy of the suggested scheme. - Author(s): H. Selamat ; R. Yusof ; R.M. Goodall
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 374 –383
- DOI: 10.1049/iet-cta:20070111
- Type: Article
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p.
374
–383
(10)
The instability caused by the conical (or profiled) shape of a solid-axle railway wheelset can be overcome by proper design of the vehicle's primary suspension system but is generally difficult as some of the wheelset parameters, namely the conicity and creep coefficients, are time-varying. To maintain the wheelset stability at high speeds and satisfactory curving performance simultaneously over the whole range of the parameters' variations, the self-tuning linear-quadratic regulator (S-T LQR) for the primary suspension system of a high-speed two-axle railway vehicle has been developed. The objective of the controller was to minimize the lateral displacement of the wheelset relative to track centerline and its yaw angle, on straight and curved tracks. The Continuous-time Least-Absolute Error with Variable Forgetting Factor (C-T LAE+VFF) estimation algorithm has been used to estimate the wheelset parameters before being used in the calculation of the linear quadratic feedback control gain matrix. The simulation results show that the S-T LQR performed better than the fixed-gain LQR for both the conical and profiled wheelset, suggesting that the ability to estimate the time-varying wheelset parameters and use them in the feedback controller design is necessary to produce better primary suspension control performance. - Author(s): F. Wang ; Z.R. Feng ; S. Liu ; P. Jiang
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 384 –391
- DOI: 10.1049/iet-cta:20070359
- Type: Article
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p.
384
–391
(8)
The authors investigate a robust supervisory control problem based on the model of fuzzy discrete event systems. If there are uncertainties in the systems, the model can be assumed to belong to a model set. For all possible models in the set, necessary and sufficient conditions for the existence of a supervisor to achieve the given fuzzy language specification are obtained under complete and partial observations. The relation between the controllability (and observability) with respect to the models and their upper bound is given, based on which the equivalent conditions for the existence of a supervisor are obtained. - Author(s): Y. Park
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 392 –401
- DOI: 10.1049/iet-cta:20070054
- Type: Article
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p.
392
–401
(10)
The author presents a three degrees-of-freedom precision hybrid stage that can move and align an object on it for the measurement of its three-dimensional image using the confocal scanning microscope. The hybrid stage consists of two individually operating x−y−thetas stages, called the coarse stage and the fine stage. The coarse stage is driven by the three linear motors and produces the initial movement of an object. On the other hand, the fine stage is driven by the four voice coil motors and provides the final alignment of it with sub-micron metre accuracy. For control of the hybrid stage, a precision motion controller is proposed. The precision motion controller consists of a position and velocity control loop, an anti-windup compensator to eliminate the windup problem that occurs in the controller, a generator of optimal force, a precision position determiner to determine the exact position of the fine stage and a perturbation observer to observe the perturbation of the fine stage and compensate it. The performances of the precision motion controller of the hybrid stage are evaluated by experiment with a hardware setup. - Author(s): S. Xu and G. Feng
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 402 –408
- DOI: 10.1049/iet-cta:20070221
- Type: Article
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p.
402
–408
(7)
The problem of adaptive robust control for uncertain systems with multiple time delays is considered. The parameter uncertainties are assumed to be time-varying norm-bounded, whose bounds are unknown. The objective is to design adaptive robust state-feedback controllers such that the resulting closed-loop system is globally uniformly exponentially convergent to a ball with a certain convergence rate. In terms of a linear matrix inequality, a sufficient condition for the solvability of this problem is presented and the expression of a desired adaptive robust state-feedback controller is given. It is shown that the result obtained improves certain existing ones in the literature. - Author(s): B. Zhou and G.-R. Duan
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 409 –419
- DOI: 10.1049/iet-cta:20070179
- Type: Article
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p.
409
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(11)
A general nonlinear feedback law for global stabilisation of asymptotically null controllable linear systems with bounded controls is established. It is shown that such a nonlinear feedback law can be constructed in two recursive ways. The results effectively allow for the construction of a hybrid control law which is partly of a nested saturation form and partly of a sum of saturations form, giving more flexibility to the designer. Using the recursive formulation, one can obtain a series of control laws containing the well-known nested type and parallel connections type laws as two special cases. Moreover, the eigenvalues corresponding to the linearised closed-loop system can be arbitrarily assigned within a certain region, which can be further used to improve the system performances. The possible ranges for the controller's parameters are extended with respect to existing results. - Author(s): J. Qiu ; G. Feng ; J. Yang
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 420 –430
- DOI: 10.1049/iet-cta:20070289
- Type: Article
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p.
420
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(11)
The authors deal with mode and parameter-dependent robust mixed ℋ2/ℋ∞ filtering design for a class of discrete-time switched polytopic linear systems. The objective is to design a homogeneous switched mixed ℋ2/ℋ∞ filter guaranteeing the asymptotic stability of the resulting filtering error systems with given performance measures. Based on a switched parameter-dependent Lyapunov function combined with Finsler's lemma, some novel conditions for robust ℋ2 and ℋ∞ performance analysis are proposed and in turn the filter synthesis is developed. It is shown that by using a new linearisation technique combined with a bounding approach, the filter gains can be obtained by solving a set of linear matrix inequalities. Finally, a numerical example is provided to illustrate the effectiveness and less conservatism of the proposed approach. - Author(s): M.N. Alpaslan Parlakçi
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 431 –436
- DOI: 10.1049/iet-cta:20070345
- Type: Article
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p.
431
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(6)
The problem of stability for linear time-delay systems of neutral type is taken into consideration. A new extensively augmented Lyapunov–Krasovskii functional is introduced and a sufficient delay-dependent stability criterion is derived in terms of linear matrix inequalities (LMIs). Utilisation of any model transformation method or any kind of bounding for the cross terms are avoided in the stability analysis. Moreover, in order to reduce the complexity of the solution of the LMI set, the proposed method does not also employ any free weighting matrix relaxation approach. Two numerical examples are illustrated to indicate the effectiveness of the proposed method. - Author(s): D. Xie and X. Chen
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 437 –445
- DOI: 10.1049/iet-cta:20070212
- Type: Article
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p.
437
–445
(9)
We investigate the observer-based switched control design problem for switched linear systems with time delay in detection of switching signal. First, an improved and generalised estimate on the matrix norm is established (Lemma 2 in Section 2). Then, based on two important lemmas, under the assumption that each subsystem is controllable and observable, online and offline observer-based switched control design methods to guarantee the asymptotical and exponential stabilisabilities are given, respectively. Finally, an example is given to illustrate the results. Our results complement the results of Xie et al. about state feedback stabilisation of switched linear systems. - Author(s): D. Qian ; J. Yi ; W. Wang
- Source: IET Control Theory & Applications, Volume 2, Issue 5, p. 446 –447
- DOI: 10.1049/iet-cta:20070456
- Type: Article
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p.
446
–447
(2)
Robust PID control design for an electrostatic micromechanical actuator with structured uncertainty
Self-tuning control for active steering of a railway vehicle with solid-axle wheelsets
Robust supervisory control of fuzzy discrete event systems
Precision motion control of a three degrees-of-freedom hybrid stage with dual actuators
Further results on adaptive robust control of uncertain time-delay systems
Global stabilisation of linear systems with bounded controls by nonlinear feedback
Robust mixed ℋ2/ℋ∞ filtering design for discrete-time switched polytopic linear systems
Extensively augmented Lyapunov functional approach for the stability of neutral time-delay systems
Observer-based switched control design for switched linear systems with time delay in detection of switching signal
Reply: Comment on Design of a stable sliding-mode controller for a class of second-order under-actuated systems
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