Design of the control system for a robotic manipulator for Space-Station On-Orbit Replaceable Unit ground testing

Describes a hierarchical robot controller designed and built at NASA´s Johnson Space Center. The robot used is a six degree-of-freedom hydraulic manipulator equipped with joint position sensors and a wrist force/torque sensor. The objective of the project is to emulate the performance characteristics of the Space Station´s Special Purpose Dexterous Manipulator (SPDM), which will perform various telerobotic external maintenance tasks. Some features implemented in the controller include a resolved position control algorithm, force/moment accommodation, and gravity compensation. This multiple-processor control system is divided, by processor, into a servo controller, a force/moment data filter, a Cartesian-space controller, a host/traffic controller and a network communication controller. This paper describes the functions of each individual processor and the design of their inter-processor communication