Force-Torque Control Experiments with the Simulated Space Shuttle Manipulator in Manual Control Mode,

Abstract : An experimental six degree-of-freedom force-torque sensor system was developed at and integrated with the simulated full-scale Space Shuttle Remote Manipulator System (RMS) at the Johnson Space Center. The sensor system provides data on forces and torques acting at the end effector. The sensor data are shown to the operator on a graphics display. The operator's response to the sensor data is through resolved rate manual control of the RMS. The opening/closing of the end effector is also in rate control mode. Two sets of control experiments were conducted using force-torque sensor information. The first set involved the use of a task board equipped with tools and modules. The operator's task was to remove the modules from their holes in the task board or insert them back to their holes. The removal or insertion of one of the modules required the use of tools which also were placed in holes in the task board. The second set of experiments involved the berthing of a payload into a latching mechanism through four V-shaped guides. Altogether more than 50 training runs and 110 recorded test runs were performed. The preliminary control experiments were successful and established the utility of the force-torque sensor system for geometrically and dynamically constrained operations. The sensory feedback significantly reduced the maximum force and torque loads during the constrained operations and permitted operational techniques that were perceived as risky previously. This paper briefly describes the experimental sensor-end-effector-display system.