Control system of the self-mobile space manipulator

Abstract
The self-mobile space manipulator, (SM)/sup 2/, is a simple, 5-DOF, 1/3 scale, laboratory version of a robot designed to walk on the trusswork and other exterior surfaces of Space Station Freedom. It will be capable of routine tasks such as inspection, parts transportation and simple maintenance procedures. The authors have designed and built the robot and gravity compensation system to permit simulated zero-gravity experiments. The authors have developed the control system for the (SM)/sup 2/ including control hardware architecture and operating system, control station with various interfaces, hierarchical control structure, multi-phase control strategy for step motion, and various low-level controllers. The system provides operator friendly, real-time monitoring, robust control for 3-D locomotion movements of the flexible robot. A hierarchical structure allows the control to be executed in various levels autonomously or by teleoperation, and a multiphase control strategy facilitates the control in different tasks. Based on the dynamic model developed, a linear-structured joint-level controller and model-based control scheme with acceleration feedback is being implemented to provide a stable and fast motion. The configuration-independent control scheme allows the control parameters to adapt to changes in system dynamics due to the robot configuration variation. With a variety of low-level controllers which the authors developed, the system has demonstrated robustness to the uncertainties in modeling and in payload.

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