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Control Theory and Applications, IEE Proceedings -

Issue 4 • Date Jul 1999

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Displaying Results 1 - 8 of 8
  • Neural network enhanced generalised minimum variance self-tuning controller for nonlinear discrete-time systems

    Page(s): 319 - 326
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    A neural network enhanced self-tuning controller is presented which combines the attributes of neural network mapping with a generalised minimum variance self-tuning control (STC) strategy. In this way the controller can deal with nonlinear plants, which exhibit features such as uncertainties, nonminimum phase behaviour, coupling effects and may have unmodelled dynamics, and whose nonlinearities are assumed to be globally bounded. The unknown nonlinear plants to be controlled are approximated by an equivalent model composed of a simple linear submodel plus a nonlinear submodel. A generalised recursive least squares algorithm is used to identify the linear submodel and a layered neural network is used to detect the unknown nonlinear submodel in which the weights are updated based on the error between the plant output and the output from the linear submodel. The procedure for controller design is based on the equivalent model, therefore, the nonlinear submodel is naturally accommodated within the control law. Two simulation studies are provided to demonstrate the effectiveness of the control algorithm View full abstract»

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  • Lyapunov inequality and bounded real lemma for discrete-time descriptor systems

    Page(s): 327 - 331
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    A generalised Lyapunov inequality is described which can be reformulated as nonstrict linear matrix inequalities (LMIs), for checking the regularity, impulse immunity, and stability of discrete-time descriptor systems simultaneously. Based on this inequality, a bounded real lemma in nonstrict LMIs is obtained which characterises properties of such descriptor systems, including regularity, impulse-free property, stability, and H norm bound condition. The proofs are purely algebraic, therefore they are simple and definite. These results could play a key role in the LMI-based H controller design for discrete-time descriptor systems View full abstract»

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  • Orthogonal Lyapunov transformations with some applications to stability studies

    Page(s): 333 - 340
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    For continuous-time linear time-varying systems, this paper shows how to determine pointwise orthogonal Lyapunov transformations, reveals their advantage over standard Lyapunov transformations for the nonperiodic case, and outlines some potential applications to stability assessment for both linear and nonlinear systems View full abstract»

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  • Linear predictive control based on approximate input-output feedback linearisation

    Page(s): 295 - 300
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The computational burden related to model-based predictive control (MBPC) of constrained nonlinear systems hampers its real-time application. To avoid this, input-output feedback linearisation (IOFL) techniques are used to linearise the process model over a wide operating range. The resulting linear model is then integrated in a linear MBPC scheme allowing for standard linear control techniques to be applied. However, the process input constraints become nonlinearly related with the optimisation variable due to the state-dependent nonlinear feedback law. In this paper a new method to IOFL of general multivariable discrete-time systems is proposed. By adopting an approximate IOFL based on a suitable linear model approximation, a new linear and state dependent input mapping is obtained which further enables the MBPC solution to be found through a single quadratic programming optimisation. The performance of this new technique is compared with other well-known schemes for the control of a Van der Vusse chemical reaction taking place in a CSTR View full abstract»

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  • Adaptive dual controller for systems with unmodelled effects

    Page(s): 301 - 309
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    An adaptive pole placement controller with dual modification is applied to a dynamic plant which is described by an unknown nonlinear model. Stability of the suggested dual controller, applied together with a robust adaptation scheme, is proved for this system. It is demonstrated that after the insertion of the dual controller, the robust adaptive system remains stable. However, some known assumptions about the unmodelled residuals of the nonlinear plant model should be modified. It is also demonstrated that in the case of no residuals in the plant model, the closed-loop system converges to the model defined by the desired pole positioning. The derived controller is applied to real-time control of hydraulic drive View full abstract»

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  • Integrated sliding-mode adaptive-robust control

    Page(s): 341 - 347
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    An integrated adaptive-robust control methodology based on the sliding mode is developed for the control of nonlinear uncertain systems. The new approach possesses the advantages of both adaptive control and robust control, and eliminates the disadvantages of each. It has the ability to learn like an adaptive controller and the ability to handle various uncertainties and reject disturbances like a robust controller. When compared with pure adaptive control, the approach used improves the transient performance, and when compared with pure robust control, it reduces the conservatism of the design. Furthermore, it guarantees the global asymptotic stability of the closed-loop system. The paper presents the methodology and illustrates the approach using a simple 1-DOF robot in the vertical plane under gravity View full abstract»

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  • Mu-synthesis of robust decentralised PI controllers

    Page(s): 289 - 294
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    A new tuning method for robust decentralised PI controllers is given. The controller tunings are obtained by minimising a robust performance criterion. The cost function to be minimised is derived from the standard μ-synthesis criterion and it takes into account the process uncertainty and the desired performance. A constraint on the variations of the controller outputs can also be added to the performance criterion. The two options, with and without a constraint, respect the specifications in a minimal way to limit the controller output variations obtained from the standard μ-synthesis criterion. These two options and the standard μ-synthesis criterion are compared on an ill-conditioned two-input two-output (TITO) process example. The generalised step response for TITO processes is used to analyse the time behaviour of closed-loop systems View full abstract»

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  • Robust regional stability analysis of continuous time-delay systems

    Page(s): 311 - 317
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    By utilising the matrix measure properties, the authors derive serval robust stability criteria for continuous time-delay systems with time-invariant parameter uncertainties. In particular, considering some required performances, a wedge, a disk, or a strip in the open left half of the complex plane is the stable region of concern. To complete the proof of the proposed results, a certain symmetric property is needed, which has not been addressed in the literature. The author also provides some examples to illustrate the feasibility of the proposed results View full abstract»

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