摘要:

A new modified adaptive algorithm with a non-linear decay term is proposed to guarantee the robust global stability of continuous-time model reference adaptive control (MRAC) systems to unmodelled dynamics in the plant. The fundamental approach is due to Kosut and Friedlander (1985), but different robust stability results and adaptive features are shown because of the non-linear decay term. A sufficient condition to find the design parameters in the decay term which ensure the robust result is proved and its dependence on the tuned gains and unmodelled dynamics is discussed. The merits and demerits of our new algorithm are also discussed using a simple example for illustration.

ISSN:0020-7179    

DOI:10.1080/00207178808906045

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A rigorous derivation is given of the polynomial method for finding Wiener filters in both discrete-time and continuous-time. In each case the method involves one spectral factorization and the solution of one diophantine equation. The theory is applicable in multivariable situations but simple scalar examples are included here to compare the polynomial approach with the basic Wiener method.

ISSN:0020-7179    

DOI:10.1080/00207178808906046

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In virtually every application of optimum linear-quadratic regulator (LQR) theory there exists a hidden region of ‘unreachable poles’ (in the left half-plane) whichcannot be realized as optimum closed-loop poles. These regions of unreachable closed-loop poles are not visible using the solution procedures ordinarily employed in LQR applications and their lurking presence has (apparently) been overlooked by many professors, textbook writers and industrial users of LQR control theory for the past 25 years. The existence of these regions of unreachable poles represents a serious defect in the LQR method because those regions may (and oftendo!) contain closed-loop pole patterns which are considered highly desirable by classical control engineering standards, i.e. by ITAE and other classical standards of ‘ideal’ transient response. We first show how one can identify the regions of unreachable poles in an LQR problem. Then, it is shown how one can modify conventional LQR theory to overcome this defect and makeallunreachable poles (in the left half-plane) become reachable. By this means, an explicit formula is derived for the LQR state-weighting matrix Q which will automatically produce ITAE orany otherarbitrarily prescribed closed-loop pole patterns in the left half-plane.

ISSN:0020-7179    

DOI:10.1080/00207178808906047

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The distributed systems considered are those with a characteristic equation expressed in terms ofu = √s, wheresis the usual Laplace transform variable. The discrete delayhenters the characteristic equation as a term or terms with a factor exp(−sh). The stability boundary method requires four steps: (a) the stability or instability ath = 0 is determined; (b) values ofutaking the formu = exp (iπ/4)v,vreal, at which a change of stability may take place, are determined by solving a polynomial equation inv; (c) the sign of the gradientdRes/dhis deduced simply at each of these values; (d) finally, thehvalues corresponding to the critical values ofvare found (or possibly just arranged in order, if qualitative results suffice). Stability changes require a consistent sequence of the signs ofdRes/dhashincreases.

ISSN:0020-7179    

DOI:10.1080/00207178808906048

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In this paper we study the global stabilization of a class of non-linear uncertain systems while decoupling the output from external disturbances to any specified degree of accuracy. The class of non-linear systems considered could be viewed as a generalization of uniform rank multivariable linear systems which have the property that all their infinite zeros are of the same order. Although the plants considered are non-linear, the compensator developed here is linear. Our compensator which achieves global exponential stability and almost disturbance decoupling of the output requires only output feedback rather than full state feedback. Model uncertainty is dealt with either by restricting the uncertain elements to particular subspaces satisfying the so-called ‘matching conditions’ and/or by treating a family of plants 𝓅 for which a single controller simultaneously globally exponentially stabilizes all the plants in 𝓅 while achieving almost disturbance decoupling of the output.

ISSN:0020-7179    

DOI:10.1080/00207178808906049

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A frequency-domain approach to arbitrary finite spectrum assignment for multivariable delay systems is developed, and a practical example is presented for illustration.

ISSN:0020-7179    

DOI:10.1080/00207178808906050

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A stable multivariable adaptive control scheme, which uses different sampling rates in different output measurements, is proposed. This control scheme is suitable for the class of multi-input, multi-output systems,G(z) = A−1(z)B(z), in whichA(z) is nearly diagonal, and outputs have separate dominant time constants. Advantages of using multirate sampling are the reduction in computational load and the improvement of system robustness with respect to sampling. Local stability of the closed-loop system is guaranteed by introducing a time-varying deadzone in the estimation algorithm. The results are verified by both simulation and experiment.

ISSN:0020-7179    

DOI:10.1080/00207178808906051

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper shows that based on the recent development of observer design solution, an observer pole selection method can be formulated to minimize the observer gain to the system input. It is proved that this method is a deterministic approach to the recovery of the loop transfer function and robustness of direct state feedback systems.

ISSN:0020-7179    

DOI:10.1080/00207178808906052

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A novel hierarchical integrated system optimization and parameter estimation technique is described which determines the optimum steady state operation of an interconnected industrial process in spite of deficiencies in the model. The technique is iterative and involves successive solutions of system optimization and model parameter estimation problems, utilizing information feedback from the real process. Particular emphasis is given to a strategy where the coordination task is divided into two nested iterative loops, with the inner loop optimization containing a self-adaptive model. Derivatives of real process measurements required by the outer loop iteration are also used to update the model. New modifiers are introduced to cater for the output-dependent constraints. This model-based double-loop iterative strategy retains an important practical advantage in that it reduces the required number of set point changes to the real process. Optimality properties and convergence conditions are investigated. A simulation study is also presented.

ISSN:0020-7179    

DOI:10.1080/00207178808906053

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A general approach for designing and the theory for analysing robust direct and indirect adaptive-control schemes for continuous-time plants is presented. The design approach involves the development of a general robust adaptive law and the use of the certainty equivalence principle to combine it with robust model reference and pole placement control structures. The global stability properties and robustness of the developed adaptive control schemes are established by using a general theory which relates the properties of signals in the mean sense over intervals of time. The developed theory and design approach are used to analyse and compare the robustness properties and performance of a wide class of robust adaptive laws which employ a dead-zone, fixed-σ, ϵ1, and a switching-σ modification as well as their variations.

ISSN:0020-7179    

DOI:10.1080/00207178808906054

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor