ISSN:0890-6327    

DOI:10.1002/acs.4480040602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractHigh‐precision measurements of joint displacements are available on robot manipulators. In contrast, the velocity measurements obtained through tachometers are in many cases contaminated by noise. It is therefore economically and technically interesting to investigate the possibility of accurately estimating the speed from direct available measurements such as the angular positions. This paper proposes a ‘smooth non‐linear observer’ (i.e. an observer with ‘smooth’ or ‘differentiable’ gains) and a modified computed torque law which is a function of estimated velocities and measurement positions for rigid industrial robot manipulators. We derive local conditions for asymptotic stability of the clo

ISSN:0890-6327    

DOI:10.1002/acs.4480040603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this paper our aim is twofold. Firstly, we briefly recall the solution to the dynamic block‐decoupling problem (DBDP) we presented at ‘NOLCOS 89’. This solution generalizes the approach taken for solving Morgan's problem, i.e. the row‐by‐row decoupling problem, by Descusse and Moog. The results we develop here are strongly connected with the structure algorithm of Hirschorn. Using the latter it is possible to exhibit particular (degenerate) controlled invariant distributions which appear to be crucial in the solution of the considered problem. The solution goes through an algorithmic procedure. Secondly, we give a new structure algorithm which makes possible the computation of the aforementioned distributions as well as the differential output rank of the considered system, which we must know for solving the DBDP. It is well known that the differential output rank, and more generally the structure at infinity, can be computed from the structure algorithm of Singh but not from the structure algorithm of Hirschorn. The former provides algebraic quantities (the structure at infinity) while the latter is mainly of interest for knowing geometric quantities (controlled invariant distributions). Our structure algorithm provides both features simul

ISSN:0890-6327    

DOI:10.1002/acs.4480040604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this paper we study a control methodology now often referred to as learning control in the recent control literature. Our primary aim is to establish a mathematical framework which will allow systematic and continuing development of learning control theory. The framework is based on the functional spaces which have been heavily used inH∞control theory. It is then applied to the study of the convergence problems associated with learning control. Three theorems on general convergence conditions are presente

ISSN:0890-6327    

DOI:10.1002/acs.4480040605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe design of observers for elastic joint robots is investigated. Using some structural properties of the robot dynamics, a model‐based observer is proposed which requires only the knowledge of the link positions. The asymptotic stability of the related error dynamics along with an estimate of the region of attraction are also given. The observer performances are analysed by means of simulation test

ISSN:0890-6327    

DOI:10.1002/acs.4480040606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractA unified framework for the stability analysis of robot tracking control is presented. By using an energy‐motivated Lyapunov function candidate, the closed‐loop stability is shown for a large family of control laws sharing a common structure of proportional and derivative feedback and a model‐based feedforward. The feedforward can be zero, partial or complete linearized dynamics, partial or complete non‐linear dynamics, or linearized or non‐linear dynamics with parameter adaptation. As a result, the dichotomous approaches to the robot control problem based on the open‐loop linearization and non‐linear Lyapunov analysis are both included in this treatment. Furthermore, quantitative estimates of the trade‐offs between different schemes in terms of the tracking performance, steady state error, domain of convergence, realtime computation load and required apriorimodel informat

ISSN:0890-6327    

DOI:10.1002/acs.4480040607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractRobust controller design approaches for non‐linear control systems usually require the evaluation of upper bounds on non‐linear quantities of the process for the robustness analysis. The conservatism and usefulness of robustness criteria are determined by the accuracy of the robustness bounds. This contribution deals with the robust control of robot manipulators and presents generally applicable evaluation techniques for bounds on robot manipulator non‐linearities which may be remnants of an incomplete non‐linear decoupling or feedback linearization. These bounds can be used to verify several robust stability criteria for the control of rigid and elastic joint robots. Apparently, these bounds give insight to the strength and significance of non‐linear couplings and may be used to judge whether complicated model‐based control laws should be preferred rather than simple linear

ISSN:0890-6327    

DOI:10.1002/acs.4480040608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe objective of this paper is to explore several robust adaptive control schemes for a class of partially known robot systems described by the equationM(q)q̈ + F(q, q̇)q̇ + G(q) = f(t) wheref(t) is the control input. First we take advantage of any known system dynamics to simplify the adaptive control problem for the unknown portion of the dynamics. Then a model‐reference adaptive control based on the Lyapunov stability criterion is designed for the remaining unknown portion of the plant. Using the Lyapunov approach, under a slowly time‐varying assumption we derive a magnitude bound and amaximum achievable convergence ratefor the error. The magnitude bound as well as the convergence rate are functions of the reference model degree of stability α (‐ α is the maximum real part of model poles).We show that there is an optimal location for the reference model poles that isindependent of the robot dynamics.This value of α is well defined, and if the feedback gains are further increased, making the model more stable,the performance of the adaptive system is degraded.It is also shown that the gains in the adaptive portion of the algorithm may be made as high as desired in order to make the actual performance approach the maximum achievable convergence rate. The effect of these adaptive gainsdoesdepend on the unknown dynamics. Simulation results will demonstrate the improved performance of the adaptive controller and the detrimental effects of high gains on the system performance.Next the slowly time‐varying assumption is relaxed to obtain more realistic bounds on the error. Formulation into a more structured system also allows us to derive a control law that does not require

ISSN:0890-6327    

DOI:10.1002/acs.4480040609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractA new concept of learning control for the improvement of robot motions is proposed, which can be referred to a mathematical modelling of learning and generation of motor programmes in the central nervous system. It differs from conventional classical and modern control techniques. It stands for the repeatability of operating a given robotic system and the possibility of improving the command input on the basis of actual measurement data acquired at the previous operation. Hence adequate conditions on the repeatability and invariance of the system dynamics are assumed, but no precise description of the dynamics is required for construction of the learning algorithms. Two types of iterative learning algorithm are proposed: one uses a PD‐type (proportional and differential) update of input commands and the other a PI‐type (proportional and integral) update where velocity signals are regarded as outputs. It is shown that in both types a better performance is realized at every attempt of operation, provided a desired motion is givena prioriand the actual motion (velocity signals) can be measured at every operation. Further, the robustness of such learning control algorithms with respect to the existence of perturbed errors of initialization of the robot, disturbances and measurement noise during operation is analysed in detail. It is shown that in PD‐type learning laws such errors are neither amplified nor aggregated in later consecutive trials of operation. In the case of PI‐type learning laws it is shown that such a robustness property is assured if a forgetting factor is adequately introduced into the repetitive learn

ISSN:0890-6327    

DOI:10.1002/acs.4480040610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractWe consider a class of uncertain mechanical systems containing flexible elements and subject to memoryless output‐feedback controllers. The damping and stiffness properties of some of the flexible elements are parametrized linearly in μ−1and μ−2respectively, where μ>0 and these components become more rigid as μ approaches zero. We propose a class of ‘stabilizing’ controllers for a system model in which the above components are rigid. Subject to a ‘linear growth condition’, the controllers also stabilize the model in which the components are flexible provided μ>0 is

ISSN:0890-6327    

DOI:10.1002/acs.4480040611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY