A New Control Scheme For Bilateral Teleoperating Systems: Performance Evaluation And Comparison

Abstract

This paper evaluates the performance of a new control scheme for bilateral master-slave teleo- perator, introduced earlier, and compares it to pub- lished control methods by using a mathematical cri- terion based on the two-port network model. It is shown that most of the published control laws under investigation do not achieve optimal performance, and the few that do, require perfect estimation (or exact knowledge) of the human operator or master arm dynamics. It is also shown that optimal performance, based on the selected mathematical criterion, can be obtained using the proposed control law: I. INTRODUCTION Teleoperating systems may be viewed as synergistic systems composed of human operators and master-slave manipulators which interact with the physical world. The master, sometimes called hand controller, is used to gen- erate commands (usually position, rate or force commands) to its remotedly located counterpart called slave. In gen- eral, the position/velocity command from the operator is fed forward to the slave, while the reaction force, due to mechanical interaction with the environment, is fed back to the master, providing contact force information to the human operator. By reflecting the measured force back to the master arm, it is said that the teleoperator is controlled bilaterally. One of the main issues in telerobotics is control of master-slave teleoperators. A number of control metho- dologies have been proposed in the teleoperator literature. There are two main methods for controlling master-slave teleoperators. The first, a more traditional approach, uses position and/or velocity error (between the master and slave) to generate a forcehorque command into the master arm. The position/velocity of the master and slave are measured by sensors usually located at the joints. The second method uses direct force feedback, rather than posi- tion and velocity errors, to generate command signals to the master. This method uses a force/torque signal obtained from a sensor, usually located at the end-effector of the slave, to provide the operator with the force feeling of the remotedly located counterpart. The force feedback control is usually considered superior because of the more precise nature of the feedback signal. The two-port model network theory has been exten- sively used for the analysis of circuits in which bi- directional energy flows are present at two distinct pairs of terminals. This method provides a useful linear representa- tion of complex networks which exchange energy. The two-port model theory is also used in bilateral teleoperator systems (1,3-81, with force and velocity sensing at the mas- ter and slave. The interfaces between the human operator and master, and between the environment and slave are ports through which the teleoperator is designed to exchange energy between the operator and environment. Recently, several algorithms have been proposed to