摘要:

Adaptive regulation of pulse-width-modulation (PWM) controlled DC-to-DC power supplies is proposed using a suitable combination of dynamical input-output linearization and the ‘backstepping’ controller design method. A nominal parameter, input-dependent, state coordinate transformation of the average PWM converter models leads to a type of pure parameter feedback canonical form associated with the Fliess generalized observability canonical form of such average models. A back-stepping design procedure can then be immediately devised which leads to a dynamical adaptive regulation scheme for the generation of the stabilizing duty ratio function. The validity of the proposed approach, regarding control objectives and robustness with respect to unmodelled, yet unmatched, and bounded stochastic perturbation inputs, is tested through digital computer simulations.

ISSN:0020-7179    

DOI:10.1080/00207179608921694

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Power regulation of horizontal-axis grid-connected up-wind constant-speed pitch-regulated wind turbines presents a demanding control problem with the plant, actuation system and control objectives all strongly nonlinear. In this paper, a novel nonlinear control strategy is devised which, in some sense, optimizes performance across the operating envelope. In comparison with linear control, the nonlinear strategy achieves a substantial improvement in performance. The realization adopted is crucial in attaining the required performance. An extended local linear equivalence condition is introduced which provides a basis for the selection of an appropriate realization. This is an important, and general, issue in the design of gain-scheduled systems and generic realizations, which satisfy the extended local linear equivalence condition, are derived for SISO systems scheduled upon an internal plant or controller variable. For the wind turbine nonlinear controller, realizations which satisfy the extended local linear equivalence condition provide a substantial improvement in performance in comparison with linear control and realizations which do not satisfy this condition.

ISSN:0020-7179    

DOI:10.1080/00207179608921695

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper deals with the design of controllers that correct faulty behaviour of sequential machines caused by corrupted inputs. Alternatively, the results can be interpreted as the design of controllers that steer a sequential machine from an unknown initial condition to a prescribed steady-state course. In these terms, the paper characterizes the uncertainties about the initial condition under which the prescribed steady-state course can be achieved. The paper is written within the input/output framework of nonlinear control, and is motivated in part by potential applications to molecular biology.

ISSN:0020-7179    

DOI:10.1080/00207179608921696

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An algorithm for iterative learning control is developed on the basis of an optimization principle which has been used previously to derive gradient-type algorithms. The new algorithm has numerous benefits which include realization in terms of Riccati feedback and feedforward components. This realization also has the advantage of implicitly ensuring automatic step size selection and hence guaranteeing convergence without the need for empirical choice of parameters. The algorithm is expressed as a very general norm optimization problem in a Hilbert space setting and hence, in principle, can be used for both continuous and discrete time systems. A basic relationship with almost singular optimal control is outlined. The theoretical results are illustrated by simulation studies which highlight the dependence of the speed of convergence on parameters chosen to represent the norm of the signals appearing in the optimization problem.

ISSN:0020-7179    

DOI:10.1080/00207179608921697

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The strong tracking filter (STF) proposed by Zhouet al.in 1992, which was developed for nonlinear systems with white noise, is extended to a class of nonlinear time-varying stochastic systems with coloured noise. A new concept of‘softening factor’is introduced to make the state estimator much smoother; its value can be preselected by computer simulations via a heuristic searching scheme. The STF is then used to estimate the parameters of a class of nonlinear time-varying stochastic systems in the presence of coloured noise. The robustness against model uncertainty of the STF is thoroughly studied via Monte Carlo simulations. The results show that the STF has strong robustness against model-plant parameter mismatches in the statistics of the initial conditions, the statistics of the process noise and the measurement noise, the system parameters, and the parameters in the measurement noise model. To a great extent the STF can give bias-free parameter estimations, where the parameters may be randomly time varying with unknown changing law.

ISSN:0020-7179    

DOI:10.1080/00207179608921698

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A bound for the magnitude frequency domain characteristics associated with the outputs of a wide class of nonlinear systems is derived as a relatively simple function of the generalized frequency response functions and properties of the system inputs. It is shown how the practical computation of the new bound can be easily performed for nonlinear systems with finite but arbitrary order nonlinearities and worked examples are included. The paper is divided into two parts. In Part 1, an expression for the output magnitude bound is derived, properties of the result are discussed and general procedures for the practical computation of the bound are developed. In Part 2 the practical computations associated with applying the bound to the polynomial nonlinear autoregressive model with exogenous input are discussed.

ISSN:0020-7179    

DOI:10.1080/00207179608921699

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An on-line parameter identification problem is formulated for linear time-invariant continuous-time systems with bounded input/output disturbances as well as non-parametric uncertainties characterized either by H2or H∞norms. Based on the formulation, a switching type gradient algorithm is proposed to estimate the parameters of the system from the available input-output data. In spite of the existence of non-parametric uncertainties and disturbances, this on-line algorithm guarantees that the estimation error is monotonically decreasing with respect to time, and the parameter estimate is convergent to a steady-state value under a mild condition. Furthermore, the algorithm is stable in the sense that the estimation error will converge to zero as both non-parametric uncertainties and disturbances gradually diminish. To evaluate the accuracy of the identified parameters, an upper bound on the estimation error is given.

ISSN:0020-7179    

DOI:10.1080/00207179608921700

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A practical stability test for linear retarded delay differential systems is proposed. Based on the fact that all unstable zeros of the characteristic quasipolynomial must lie within a restricted bounded region of the complex plane, the test provides a readily computable necessary and sufficient condition for asymptotic stability. It also copes equally well with both cases of commensurate and non-commensurate delays. Furthermore, a method for evaluating the abscissa of stability of the quasi-polynomial, defined as the largest of the real parts of the zeros of the quasipolynomial, is given. The method is based on a known technique which makes repeated use of a stability test, and thereby avoids the calculation of all the zeros. The stability test and the method for computing the abscissa of stability provide useful computational tools for the design of dynamical systems with delays using the method of inequalities. Numerical examples are given.

ISSN:0020-7179    

DOI:10.1080/00207179608921701

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor