摘要:

An adaptive learning control scheme is presented for uncertain robotic systems that is capable of tracking the entire profile of the reference input. The control scheme consists of three control blocks: a linear feedback, a feedforward error compensation and a learning strategy. At each iteration, the linear feedback with the feedforward error compensation provides stability of the system and keeps its state errors within uniform bounds. The learning strategy, on the other hand, estimates the desired control input and uncertain system parameters, which are used to track the entire span of a reference input over a sequence of iterations. In contrast with many other learning control techniques, the proposed learning algorithm neither uses derivative terms of feedback errors nor assumes any perturbations on the learning control input as a prerequisite. The parameter estimator neither uses any joint acceleration terms nor uses any inversion of the estimated inertia matrix, which makes its implementation practical. The proposed controller is superior to the high-gain feedback based learning controller (Kucet al.1991) because the magnitude of linear feedback gains required to guarantee convergence of the learning controller can be made much smaller thereby solving the problems of actuator saturation or actuator overdesign. The convergence proof of the learning scheme with or without parameter estimation is given under mild conditions on the feedback gains and learning control gains. Under the condition of persistent excitation in the domain of iteration sequence, it is proved that the estimated system parameters also converge to the true parameters.

ISSN:0020-7179    

DOI:10.1080/00207179608921719

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Recently, a new class of adaptive control schemes, motivated from nonlinear systems theory, has been proposed for minimum phase linear time invariant plants. Under certain assumptions on the plant transfer function, these schemes guarantee uniform signal boundedness and good transient and steady-state response for the regulation or tracking error. Despite the good performance properties of the proposed schemes, their practicality relies very much on their robustness properties with respect to plant model uncertainties. These robustness properties have to be established and understood for application purposes. The purpose of this paper is to analyse the stability properties of this new class of adaptive controllers in the presence of ‘ reasonable’ classes of plant model uncertainties. We first indicate that the same non-robust behaviour that appears in the case of the traditional adaptive controllers without modifications may be exhibited by this new class of adaptive controller. We then propose design modifications and establish robustness with respect to a general class of multiplicative plant perturbations and bounded input-output disturbances.

ISSN:0020-7179    

DOI:10.1080/00207179608921720

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We consider the class of control systems that consist of a linear time-invariant forward path and a memoryless (possibly time-varying) nonlinear feedback. In this work we extend the small gain theorem in ℒ∞for these systems, in two ways. On the one hand, we generalize the approach to nonlinearities with bounds of arbitrary shape. On the other hand, we add structure to the analysis, dividing the vectors involved in the problem (outputs, nonlinearities, disturbances) into smaller dimension subvectors. This leads to less conservative conditions in the cases in which some structure of the nonlinearity is known. One important application is to the closed-loop robust stability analysis of a nonlinear plant controlled by a feedback linearizing and stabilizing controller. This is the case of an uncertain nonlinear model to be controlled, affected by measurement noise and external disturbances.

ISSN:0020-7179    

DOI:10.1080/00207179608921721

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper presents a method to construct an improved Lyapunov function for power system stability analysis, based on the generalized multivariable Popov criterion developed by Moore and Anderson. The method has been evaluated in two different power systems. Calculation results show that compared with the traditional Lure Lyapunov functions, the proposed Lyapunov function can detect a stability region much closer to the true power system stability boundary.

ISSN:0020-7179    

DOI:10.1080/00207179608921722

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The effect of vibrations applied to a flexible beam is investigated. A thorough analysis of an (n + l)-link approximation to the flexible beam is presented, with bounds on the vibrations (guaranteeing stability) amplitude and frequency calculated. The main conclusion, which is quantified as well in our analysis, is that the vibrations act to ‘ rigidify’ the flexible beam. This conclusion brings very interesting potential applications. Some very preliminary laboratory experiments are also presented.

ISSN:0020-7179    

DOI:10.1080/00207179608921723

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper presents an efficient and systematic approach to designing a feedback controller and an observer for non-redundant linear multi-degrees of freedom mechanical systems including actuator dynamics. Taking into account the system symmetries, four block canonical forms are introduced. The submatrices of the block normal forms produce two matrix polynomials. Based on them, the pole placement method can be successfully applied to design both the state feed-back controller and the observer. To implement the controller and observer designed, symbolic computation is used.

ISSN:0020-7179    

DOI:10.1080/00207179608921724

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper presents recursive algorithms for state bounding, using ellipsoidal sets to describe the state uncertainties and to bound the process and observation noises. The algorithms optimize each stage of updating, according to the minimum-volume and minimum-trace criteria. Simulations compare the performance of the bounding algorithms with that of a Kalman filter, and investigate the influence of noise distribution within the bounds.

ISSN:0020-7179    

DOI:10.1080/00207179608921725

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The (J,J')-lossless factorization plays an important role inH ∞ control theory, just like the Wiener-Hopf factorization does in LQG theory, for continuous-time systems. In this paper, the theory ofJ-lossless factorization is extended to discrete-time systems. The notionJ-lossless conjugation, which is a powerful tool for computingJ-lossless factorization in continuous-time systems, is also extended to discrete-time systems. These extensions are far from trivial. The discrete-time versionJ-lossless conjugations and factorizations turns out to be much more complicated, reflecting the complicated nature of the discrete-time Riccati equations.

ISSN:0020-7179    

DOI:10.1080/00207179608921726

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper discusses a method to compute a kernel representation of the largest controlled invariant subspace in the kernel of the output mapping of a structured system. The graph of the structured system is used to make the relevant equations, and then a formula manipulation package can be used to compute a condensed kernel representation, or even an image representation, of the largest controlled invariant subspace.

ISSN:0020-7179    

DOI:10.1080/00207179608921727

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor