An experimental study on compliance control for a redundant personal robot arm

Human–robot interaction represents a critical factor in the design of personal robots as well as in the implementation of robot behavior and control. This work investigates and proposes solutions to the problem of controlling an anthropomorphic robot arm for personal assistance, by dealing with the peculiarities of its design, i.e. the mechanics of its cable-actuated, intrinsically compliant structure, and by emphasizing its potential in applications of physical and functional interaction with the environment and with human users. To satisfy the requirements of increasing the safety in the interaction and the robot functionality in tasks performed in cooperation with humans, three solutions are developed and tested for the considered personal robot. The initial idea is aimed at developing an efficient as well as computational convenient interaction control strategy, i.e. a compliance control scheme in the Cartesian space. The analysis of its limited performance suggests two further control strategies, i.e. a compliance control scheme in the joint space and an impedance–compliance control scheme. Their compared analysis points out that all the three solutions can safely operate in the human environment, but from a functional point of view only the last two schemes can effectively control the personal robot arm in its whole workspace. The paper describes the mechanics of the considered robot arm, with special regard to its anthropomorphism and cableactuation and presents in details the three control schemes. They are critically evaluated through the experimental results achieved in tasks of physical and functional interaction with the environment and with human users. The impedance–compliance controller emerges as the more appropriate to the addressed application as well as to the peculiar cable-actuated structure. © 2003 Elsevier Science B.V. All rights reserved.