Lecture Notes in Control and Information Sciences 233. Editor: M. Thoma

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1 Lecture Notes in Control and Information Sciences 233 Editor: M. Thoma

2 Pasquale Chiacchio and Stefano Chiaverini (Eds) Complex Robotic Systems ~ Springer

3 Series Advisory Board A. Bensoussan M.J. Grimble P. Kokotovic H. Kwakernaak J.L. Masse)" Editors Dr Pasquale Chiacchio Dr Stefano Chiaverini Dipartimento di Informatica e Sistemistica, Universith degli Studi Napoli Federico II, Via Claudio 21, Napoli, Italy ISBN Springer-Verlag Berlin Heidelberg New York British Library Cataloguing in Publication Data Complex robotic systems. - (Lecture notes in control and information sciences ; 233) 1.Robotics I.Chiacchio, Pasquale II.Chiaverini, Stefano 629.8'92 ISBN Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the L~rary of Congress Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of ticences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. Springer-Verlag London Limited 1998 Printed in Great Britain The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The pubnsher makes no representation, express or impued, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. Typesetting: Camera read)" by editors Printed and bound at the Athenmum Press Ltd., Gateshead, Tyne & Wear Printed on acid-free paper

4 No' si volta chi a stella ~ fisso. Leonardo da Vinci

5 Preface The challenges that mankind must face in this era of astonishing progress in technology calls for the development of a common and up-to-date worldwide knowledge base. When working at this book our intention was to realize a small contribution to the achievement of this goal within the field of Robotics. Robotic systems have proven themselves to be of increasing importance and are widely adopted to substitute for humans in repetitive and/or hazardous tasks. Their diffusion has outgrown the limits of industrial applications in manufacturing systems to cover all the aspects of exploration and servicing in hostile environments such as undersea, outer space, battlefields, and nuclear plants. Complex robotic systems, i.e. robotic systems with a complex structure and architecture, are gaining increasing attention from both the academic community and industrial users. The modeling and control problems for these systems cannot be regarded as simple extensions of those for traditional single manipulators since additional complexity arises: to accomplish typical tasks there is the need to ensure coordinated motion of the whole system together with management of interaction between each component of the system. This book focuses on two examples of complex robotic systems; namely, cooperating manipulators and multi-fingered hands. In April 1997 we organized a Tutorial Session on these topics at the IEEE International Conference on Robotics and Automation held in Albuquerque, NM, collecting contributions from distinguished scientists throughout the world. The collected material was of high quality and up-to-date, thus we thought it could be of interest to a wider audience. Therefore, we asked all the contributors to further extend their manuscripts; all of them agreed and the result of this joint effort is this book. Although the book is the outcome of a joint project, the individual contributions are attributed as detailed in the following. We feel the need to thank our colleagues for their motivation during the project. vii

6 viii Preface In Chapter 1, Masaxu Uchiyama gives a general perspective of the state of the art of multi-arm robot systems. After outlining the historical evolution of studies in this area, he gives the fundamentals of kinematics, statics and dynamics of such systems. Chapter 2 has been written by John T. Wen and Lee S. Wilfinger. They extend the manipulability concept commonly used for serial manipulators to general constrained rigid multibody systems. The concepts of unstable grasp and manipulable grasp are also introduced. In Chapter 3 we present the kinematic control approach for a dualarm system. An effective formulation is presented which fully characterizes a coordinated motion task, and a closed-loop algorithm for the inverse kinematics problem is developed. A joint-space control scheme based on kineto-static filtering of the joint errors is devised and analyzed. Michael A. Unseren in Chapter 4 reviews a method for dynamic load distribution, dynamic modeling, and explicit internal force control when two serial link manipulators mutually lift and transport a rigid object. A control architecture is also suggested which explicitly decouples the two set of equations comprising the model. Ian D. Walker devotes Chapter 5 to a survey of design, analysis, and control of artificial multi-fingered hands and corresponding research in the area of machine dexterity. An extensive bibliography is also provided. In Chapter 6 Friedrich Pfeiffer presents optimal coordination and control of multi-fingered hands for grasping and regrasping. The method is applied to an experimental setup consisting of a hand with hydraulically driven fingers which ensure good force control. The book is addressed to graduate students as well as to researchers in the field. We hope they will find it useful and fruitful. Napoli, Italy, September 1997 Pasquale Chiacchio, Ste/ano Chiaverini Contributors, in chapters' order, are: Masaru Uchiyama, Tohoku University, Japan; John T. Wen and Lee S. Wilfinger, Rensselaer Polytechnic Institute, U.S.A.; Pasquale Chiacchio and Stefano Chiaverini, Universit/~ di Napoli Federico II, Italy; Michael A. Unseren, Oak Ridge National Laboratory, U.S.A.; Inn D. Walker, Clemson University, U.S.A.; Friedrich Pfeiffer, Technische Universit t M/inchen, Germany.

7 Contents Multi-arm robot systems: A survey Introduction Dynamics of multi-arm robots Derivation of task vectors External and internal forces/moments External and internal velocities External and internal positions/orientations Hybrid position/force control Load sharing Practical implementation Advanced topics Multi-flexible-arm robots Slip detection and robust holding Conclusions References Kinematic manipulability of general mechanical systems Introduction Differential kinematics and static force model Differential kinematics Force balance Velocity and force manipulability ellipsoids Serial manipulators Velocity ellipsoid Force ellipsoid Configuration stability and manipulability Internal force and virtual velocity Illustrative examples Simple two-arm example Planar Stewart platform example ix

8 CONTENTS Six-DOF Stewart platform example Effects of arm posture and bracing on manipulability Effect of arm posture Effect of bracing Effect of brace location Effect of brace contact type Comparison of manipulability ellipsoids Conclusions References Kinematic control of dual-arm systems Introduction Cooperative task description Differential ldnematics Inverse kinematics algorithm Cooperative system modeling Joint space control Stability analysis Imperfect compensation of gravity terms Addition of a force loop Conclusions References Load distribution and control of interacting manipulators Introduction System description and dynamics System variables and coordinate frames Manipulator dynamics Object dynamics A general framework for load distribution Identifying motion inducing and internal stress components of (~ Y) Choosing matrix M Modeling of ldnematic coupling effects Derivation of rigid body model in joint space Reduced order model Control architecture Conclusions References

9 CONTENTS xi Multi-fingered hands: A survey Robot hand hardware Key issues underlying multifingered manipulation Contact conditions and the release of constraints Ongoing research issues Grasp synthesis Grasp stability The importance of friction Finger force distribution issues Varying contacts: Rolling and sliding Kinematics of rolling contact Grasp compliance and control Further research issues Current limitations Conclusions References Grasping optimization and control Introduction Grasp strategies ,3 The TUM-hydraulic hand The design Measurement and control Examples Conclusions References