A real-time control system for a mobile dexterous 7 DOF arm

This paper describes the design and implementation of a real-time control system with multiple modes of operation for a mobile redundant dexterous manipulator. The manipulator under study is a seven degree-of-freedom (DOF) arm from Robotics Research Corporation, mounted on a motorized platform. The manipulator-plus-platform system has 2-DOF for the task of hand placement and orientation. The redundancy resolution is achieved by accomplishing two additional tasks using the configuration control technique. The system allows a choice of arm angle control or collision avoidance for the seventh task and platform placement or elbow angle control for the eighth task. In addition, joint limit avoidance task is automatically invoked when any of the joints approach their limits. The system is robust to singularities, and also provides the capability of assigning weighting factors to end-effector and redundancy resolution tasks. The motion control algorithms are executed at 1.1 ms on two MC68040 processors in a VME-bus environment running the VxWorks real-time operating system. The paper describes the hardware and software components of the VME environment. Experimental results are also presented