Online ISSN
1751-8652
Print ISSN
1751-8644
IET Control Theory & Applications
Volume 2, Issue 1, January 2008
Volumes & issues:
Volume 2, Issue 1
January 2008
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- Author(s): J. Feng ; J. Lam ; S. Xu ; Z. Shu
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 1 –6
- DOI: 10.1049/iet-cta:20070044
- Type: Article
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The authors deal with the problem of exponential stabilisation for continuous-time stochastic systems. Several equivalent characterisations are presented for exponential stability of continuous-time stochastic systems. The relationship between decay rate and the spectral abscissa of an operator associated with a stochastic system is investigated. On the basis of this relationship, optimal controllers are designed for continuous-time stochastic systems. Finally, an example is provided to illustrate the method. - Author(s): Y.B. Zhao ; G.P. Liu ; D. Rees
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 7 –15
- DOI: 10.1049/iet-cta:20070005
- Type: Article
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7
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A predictive control and scheduling co-design approach is proposed to deal with the controller and scheduler design for a set of networked control systems which are connected to a shared communication network. In the proposed approach, a predictive controller is applied to generate the control predictions for each system using delayed sensing data and previous control information, and a time delay compensator is designed at the actuator side to actively compensate for the network-induced delay in the forward channel when the control action is taken. Two different scheduling algorithms, the existing static rate monotonic (RM) scheduling algorithm and a new dynamic scheduling algorithm called dynamic feedback scheduling (DFS), are considered to schedule the transmissions of the control signals generated by the predictive controller, which are packed and transmitted to the actuator in one packet simultaneously. Both the scheduling algorithms are designed with the guarantee of the stability of all the systems, which is achieved by ensuring that the time delay of the systems do not exceed the upper bound under which the systems are stable. It is also pointed out that the RM algorithm is a special case of the proposed DFS algorithm, in the sense that the former can work only in a private network environment, whereas the latter extends its application to such networks where other components occupying the network. Simulations for both the RM and the DFS algorithms, illustrate the validity of the proposed approach. - Author(s): P. Lanusse ; H. Benlaoukli ; D. Nelson-Gruel ; A. Oustaloup
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 16 –23
- DOI: 10.1049/iet-cta:20060491
- Type: Article
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The control of time-delayed perturbed systems is easy when time delay affects system inputs or outputs. In the more difficult case when system states are affected, CRONE (fractional order) control-system design (CSD) methodology can be adapted and used. Stability analysis is achieved using interval analysis. An academic time-delayed system is used to illustrate the robust CSD methodology and the robust stability analysis. In order to provide a reduced-order robust controller, a reduced-order Padé approximation of the nominal system is selected as the nominal plant. - Author(s): R. Bárcena and A. Etxebarria
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 24 –31
- DOI: 10.1049/iet-cta:20070088
- Type: Article
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24
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The performance of digitally controlled systems can be improved by using properly adjusted fractional-order hold (FROH) circuits instead of the common zero-order hold. Nevertheless, some of the previous analytical results formerly presented in the bibliography are exclusively applicable to zero-free second-order continuous-time plants. Consequently, the related FROH tuning methods may only be used in such cases. The mentioned results are extended to first-order plus time-delay systems. In this way, the application of FROH circuits in a wide range of industrial digital control systems is allowed. - Author(s): H.K. Lam and W.K. Ling
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 32 –39
- DOI: 10.1049/iet-cta:20070126
- Type: Article
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The sampled-data fuzzy control of nonlinear systems is presented. The consequents of the fuzzy controller rules are linear sampled-data sub-controllers. As a result, the fuzzy controller is a weighted sum of some linear sampled-data sub-controllers that can be implemented by a microcontroller or a digital computer to lower the implementation cost. Consequently, a hybrid fuzzy controller consisting of continuous-time grades of memberships and discrete-time sub-controller is obtained. The system stability of the fuzzy control system is investigated on the basis of Lyapunov-based approach. The sampling activity introduces discontinuity to complicate the system dynamics and make the stability analysis difficult. The proposed fuzzy controller exhibits a favourable property to alleviate the conservativeness of the stability analysis. Furthermore, linear matrix inequality-based performance conditions are derived to guarantee the system performance of the fuzzy control system. An application example is given to illustrate the merits of the proposed approach. - Author(s): A.C.-Y. Lin ; H.-N. Huang ; Y.-C. Su ; C.-Y. Shiu ; J.-L. Hwang
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 40 –50
- DOI: 10.1049/iet-cta:20060530
- Type: Article
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A fuzzy controller to implement tissue control method (TCM) proposed by Lin et al. (in physiol Meas, 2006) to measure the instantaneous arterial blood pressure is presented. The TCM adopts a piezo-actuator to move the pressure transducer up and down to maintain the mean blood pressure measured on the skin by tracking the variation in the blood pressure. Since the operation of the piezo-actuator exhibits hysteresis behaviour in the actuator movement, the controller should have the ability to track the blood pressure variation as well as compensate for the hysteretic movement. A Takagi–Sugeno fuzzy model is adopted to represent the Bouc–Wen model in describing the hysteresis with parameters identified from the dynamic responses of the actuator. On the basis of the model, a stable fuzzy observer is developed to linearise the movement of the piezo-actuator, and a PI controller is designed to track the variation in blood pressure. The designed fuzzy controller has successfully tracked various command signals during software and hardware tests. The fuzzy controller is located in an instrument that measures the instantaneous blood pressure. The experimental results show that the proposed fuzzy controller is feasible and satisfactory for controlling the piezo-actuator. - Author(s): W. Xie
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 51 –55
- DOI: 10.1049/iet-cta:20060501
- Type: Article
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A kind of new linear matrix inequality (LMI)-based formulation is presented for multi-objective H∞/α-stability controller synthesis of linear time invariant (LTI) systems. New LMI-based conditions enable to parameterise controllers without involving the Lyapunov variables in the formulation. With this feature, multi-objective controllers can be designed, with non-common Lyapunov variables and two additional adjustable scalars. Furthermore, to find the minimum possible cost, LMI-based conditions can be solved by the grid of the space which is composed of these scalars. When compared with previous results based on a common Lyapunov function, this provides less conservative results. Finally, two numerical examples are included to illustrate the effectiveness of the proposals. - Author(s): A.-G. Wu and G.-R. Duan
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 56 –60
- DOI: 10.1049/iet-cta:20070083
- Type: Article
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A matrix equation AV+BW=EVF+R is considered, where E, A, B and R are matrices with appropriate dimensions, F is an arbitrarily given Jordan matrix and V and W are the matrices to be determined. A complete explicit general solution for this equation is established based on elementary transformations of polynomial matrices. The proposed solution does not involve the derivative of polynomial matrices and not require the eigenvalues of matrix F to be known. When the eigenvalues of matrix F are prescribed, the solution for matrices V and W can be obtained by carrying out singular value decompositions, thus possesses good numerical stability. An example is employed to illustrate the effect of the proposed approaches. - Author(s): J. Jugo ; I. Lizarraga ; I. Arredondo
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 61 –71
- DOI: 10.1049/iet-cta:20060461
- Type: Article
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The methodology for the nonlinear modelling and analysis of active magnetic bearing (AMB) systems in the harmonic domain (HD) is presented. This approach is based on the HD linearisation of the AMB system around nonlinear stationary solutions at different rotating speeds. The main advantage obtained is the representation of the periodic LTV models that describe the steady-state dynamics for each speed, by means of LTI models in the HD. In order to show its possibilities, the proposed approach is applied to an AMB laboratory testbed based on the MBC500 Rotor Dynamics from Launchpoint Technologies. This analysis explains the nonlinear nature of the response that appears at high speeds, due to the large oscillations introduced by the shaft unbalance, and detects a low-frequency gain loss when increasing the rotating speed. This phenomenon causes the instability of the system, leading to destructive crashes. In addition, the analysis allows to take into account the effect of the delay introduced by the calculation time in the system behaviour when the controller is implemented by using digital devices. - Author(s): R.-J. Wai and J.-D. Lee
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 72 –86
- DOI: 10.1049/iet-cta:20060527
- Type: Article
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72
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The levitation control in a linear magnetic levitation (maglev) rail system is a subject of considerable scientific interest because of highly nonlinear and unstable behaviours. The authors mainly focus on the sequential developments of backstepping-based control systems including a backstepping control (BSC), an adaptive BSC (ABSC) and an adaptive dynamic surface control (ADSC) for the levitated positioning of the linear maglev rail system. In the proposed ADSC system, a filter mechanism is incorporated with BSC to cope with the problem of the explosion terms caused by repeated differentiations in backstepping design procedure. Moreover, a robust observer is designed for predicting system uncertainties to solve the trouble of chattering phenomena caused by a sign function in BSC and ABSC law despite the utilisation of a fixed value or an adaptive tuning algorithm for the lumped uncertainty bound. The effectiveness of the proposed control schemes for the levitation control of a maglev system is verified by numerical simulations and experimental results, and the superiority of the ADSC system is indicated in comparison with the BSC and ABSC systems. - Author(s): J. Qiu ; Y. Xia ; H. Yang ; J. Zhang
- Source: IET Control Theory & Applications, Volume 2, Issue 1, p. 87 –93
- DOI: 10.1049/iet-cta:20070070
- Type: Article
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p.
87
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The problem of robust state feedback control using delta operator approach for a class of linear fractional uncertain systems with time-varying delays is investigated. Based on Lyapunov–Krasovskii functional in delta domain, a new delay-dependent state feedback controller is presented in terms of linear matrix inequalities. The sampling-period T is an explicit parameter, and thus it is easy to observe and analyse the effect of the state feedback controller with different sampling periods. The proposed method can unify some previous related continuous and discrete systems into the framework of delta operator systems. Numerical examples are given to illustrate the effectiveness of the developed techniques.
Stabilisation of stochastic systems with optimal decay rate
Integrated predictive control and scheduling co-design for networked control systems
Fractional-order control and interval analysis of SISO systems with time-delayed state
Mitigating the effect of fractional time delays in hybrid control systems
Sampled-data fuzzy controller for continuous nonlinear systems
Implementation of fuzzy controller for measuring instantaneous arterial blood pressures via tissue control method
Multi-objective H∞/α-stability controller synthesis of LTI systems
Explicit general solution to the matrix equation AV+BW=EVF+R
Nonlinear modelling and analysis of active magnetic bearing systems in the harmonic domain: a case study
Backstepping-based levitation control design for linear magnetic levitation rail system
Robust stabilisation for a class of discrete-time systems with time-varying delays via delta operators
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