On discrete control of nonlinear systems with applications to robotics

Much progress has been reported in the areas of modeling and control of nonlinear dynamic systems in a continuous-time framework. From implementation point of view, however, it is essential to study these nonlinear systems directly in a discrete setting that is amenable for interfacing with digital computers. But to develop discrete models and discrete controllers for a nonlinear system such as robot is a nontrivial task. Robot is also inherently a variable-inertia dynamic system involving additional complications. Not only the computer-oriented models of these systems must satisfy the usual requirements for such models, but these must also be compatible with the inherent capabilities of computers and must preserve the fundamental physical characteristics of continuous-time systems such as the conservation of energy and/or momentum. Preliminary issues regarding discrete systems in general and discrete models of a typical industrial robot that is developed with full consideration of the principle of conservation of energy are presented. Some research on the pertinent tactile information processing is reviewed. Finally, system control methods and how to integrate these issues in order to complete the task of discrete control of a robot manipulator are also reviewed

ARMA models with time-dependent coefficients: estimators and applications

This paper describes a framework for time-dependent modelling of nonstationary signais, based upon autoregressive or ARMA models with time-varying coefficients . Previous works by the author are summarized here : starting front ideas proposed by Rao, Mendel and then Liporace, it is assumed that the coefficients of the model are expressed as linear combinations of known time functions . A class of estimators is described in this text, comprising autoregressive models, moving average models, and also lattice filters, parametrized through reflection coefficients or through Log Area Ratios . Speech synthesis, which is one of the applications for which these models are efficients, concludes the paper.On présente une méthodologie de modélisation des signaux non stationnaires au moyen d'une classe de modèles autorégressifs à moyenne ajustée. Application à la synthèse de la parol

Adaptive Pole Placement Control of Nonlinear Systems

Mechanical Engineerin

A control system design technique for nonlinear discrete time systems

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1988A new control methodology is proposed for use with a class of nonlinear, single-input discrete time systems. The technique is based on a discrete time approach that parallels existing continuous time sliding surface concepts. Modifications to the basic algorithm allow for system models with time-variant or uncertain parameters, time delays in the control input, and external disturbances. A major feature of the method is its straightforward extension to an adaptive control form which can be used to improve performance and maintain stability in the presence of large parametric uncertainty or time-variant behavior. Techniques are proposed for overcoming instabilities that frequently arise when using adaptive control schemes based on reduced order system models or in the presence of disturbances. A framework is provided for the practical application of the methodology to continuous time systems. The discrete time nature of the development makes it especially well suited to applications where sensor data is infrequently available or computational power is limited. An experimental study is performed using an underwater remotely operated vehicle to verify the validity of the approach. The ability of the method to use a nonlinear model and adapt to large parametric uncertainty is shown to result in improved performance over the use of a linear or time-invariant model.Finally, the United States Navy and the National Science Foundation are gratefully acknowledged for their financial support of my graduate education. This research was also sponsored in part by ONR Contract N00014-36-C-0038, ONR Grant N00014-87- J-1111 (formerly N00014-87-G-0111), NSF Grant 8611640-ECS, and NRL Contract N00014-88-K-2022

Proceedings of the NASA Conference on Space Telerobotics, volume 5

Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotics technology to the space systems planned for the 1990's and beyond. Volume 5 contains papers related to the following subject areas: robot arm modeling and control, special topics in telerobotics, telerobotic space operations, manipulator control, flight experiment concepts, manipulator coordination, issues in artificial intelligence systems, and research activities at the Johnson Space Center