摘要:

A new method is presented for defining the bounds on achieveable robust performance for stable SISO systems which can be described by approximate linear models. The method provides a tutorial presentation on the use of theH∞-formulation to define performance specifications which can be guaranteed despite the degree of uncertainty in the model. The parametric uncertainty associated with the linear process model is used to contruct a region of achievable performance in performance weight parameter space, which can be used to characterize bandwidth and underdampedness in the achievable closed-loop response. This region is bounded by locii of ‘best performance guaranteeing robustness’ and ‘worst necessary performance’ and also by robust stability constraints. The position and size of the region depends greatly on the level of model uncertainty. Using the performance bounds thus generated, the designer can pick a performance weight which will guarantee robust performance while incorporating his own preferences regarding controller type and response characteristics.

ISSN:0020-7179    

DOI:10.1080/00207179108953674

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Ann × nnon-linear multiple-input multiple-output systemWis presented, known only to belong to a set {W}.Wis embedded in a two-degree-of-freedom feedback structure, {r} is a set of possible command inputs, where for eachr∈ {r} there is a set {Ar} of acceptable outputs. The two degrees of freedom have to be selected such that in response to each command inputr, the plant's outputy∈ {Ar} for allW∈ {W}, A design technique is presented for solving this problem, based on the Horowitz design method for MIMO linear time invariant feedback systems. Sufficient conditions are given under which a solution is guaranteed. A design example is provided.

ISSN:0020-7179    

DOI:10.1080/00207179108953675

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Additive uncertainty of multivariable systems is often assumed to be either unstructured or structured, depending on whether the size or uncertainty is defined in terms of maximum singular value bounds, or bounds on the moduli of individual elements. In many practical situations, however, more information is available, and in particular the frequency response of the elements of uncertainty often display ‘directionality’. To exploit this ‘directionality’ the present paper adopts elliptical rather than circular bounds on the elements of uncertainty and derives an algorithm that generates exact eigenvalue regions which, in turn, can be deployed in the construction of exact generalized Nyquist bands. With the aid of such bands it is possible to get an exact (non-conservative) assessment of the stability margins and of other aspects of the dynamic performance of a much wider class of uncertain multivariable systems.

ISSN:0020-7179    

DOI:10.1080/00207179108953676

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Some algorithms for computing the underlying continuous-time stochastic model from a sampled ARMA model are presented. Three algorithms are given, all having a modest computational complexity. The properties of the algorithms are analysed and also illustrated by means of numerical examples.

ISSN:0020-7179    

DOI:10.1080/00207179108953677

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In adaptive control systems, it is a difficult task to choose an adequate reference model such that the perfect model matching condition can be guaranteed in every adaptive step. This paper presents a new design algorithm for model reference adaptive control systems to synthesize an adaptive controller such that the output error between the reference model and the plant can vanish in a minimax manner, which can improve the transient behaviour of model reference adaptive control systems. In this situation, the stringent matching condition can be relaxed; therefore, the proposed design algorithm is also suitable for unstable or non-minimum phase systems. A series of computer simulations is also included to illustrate the proposed design algorithm.

ISSN:0020-7179    

DOI:10.1080/00207179108953678

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Concerns the problems of decentralized reliable control in linear time-invariant multivariable control systems by the stable factorization approach. Decentralized reliable control is defined as the problem in which the closed-loop system remains stable in spite of failure in the interconnection between the subplants. Based on the decentralized, parametric characterization developed by Desoer and Gündes in 1988, a necessary and sufficient condition for the decentralized version of the strong stabilization problem is first proposed. Next, it is shown that the decentralized reliable stabilization problem is solvable if and only if the augmented plant is decentralized strongly stabilizable. Moreover, it is concluded that the problem of centralized reliable multiple control can be viewed as the problem of decentralized reliable stabilization of an augmented plant.

ISSN:0020-7179    

DOI:10.1080/00207179108953679

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Motivated by recent advances in designing robust adaptive controllers and in dealing with uncertain dynamical systems, a new model reference adaptive control which is robust to a class of unmodelled dynamics and bounded output disturbances in the case of relative degree one is presented. The implementation of the controllers includes a switching mechanism which plays a crucially important role in functions of stabilizing as well as tracking. It is shown that global stability of the overall system is achieved under no assumption of persistency of excitation, and tracking errors will converge to a residual set whose size can be directly related to the size of unmodelled dynamics and of output disturbances explicitly. In the ideal case, the residual set degenerates to a single null point and convergence can be achieved in finite time without any requirement of persistency of excitation.

ISSN:0020-7179    

DOI:10.1080/00207179108953680

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper examines the asymptotic properties of a hybrid adaptive control scheme. While there are many different meanings of the word ‘hybrid’ control in the literature, we are referring to a scheme where the on-line parameter estimation and underlying control design are carried out in a discrete time using digital electronics and do not require any analog multiplications or divisions. This is of critical importance in practice since analog multipliers/dividers are subject to serious drift and offset errors. For such hybrid schemes we establish stability and an output tracking property without recourse to persistence of exitation. The proof of stability requires a sufficiently fast sampling rate for the discrete time parameter estimation and the underlying control design.

ISSN:0020-7179    

DOI:10.1080/00207179108953681

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We present a new approach to solving long-horizon, discrete-time optimal control problems using the mixed coordination method. The idea is to decompose a long-horizon problem into subproblems along the time axis. The requirement that the initial state of a subproblem equal the terminal state of the preceding subproblem is relaxed by using Lagrange multipliers. The Lagrange multipliers and initial state of each subproblem are then selected as high-level variables. The equivalence of the two-level formulation and the original problem is proved for both convex and non-convex cases. The low-level subproblems are solved in parallel using extended differential dynamic programming (DDP). An efficient way to find the gradient and hessian of a low-level objective function with respect to high-level variables is developed. The high-level problem is solved using the modified Newton method. An effective procedure is developed to select initial values of multipliers based on the initial trajectory. The method can convexify the high-level problem while maintaining the separability of an originally non-convex problem. The method performs better and faster than one-level DDP for both convex and non-convex test problems.

ISSN:0020-7179    

DOI:10.1080/00207179108953682

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper looks at the problem of eigenstructure assignment using the system outputs. The algorithm developed is a single pass solution based on the singular value decomposition used to assess rank deficiency. The technique uses metrics to assess the time response, actuator movement and output decoupling of the eigenstructure problem. The paper then applies the algorithm to a multi-input system and demonstrates the use of the decoupling and actuator metrics.

ISSN:0020-7179    

DOI:10.1080/00207179108953683

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor