Implementation issues in identifying the failure-tolerant workspace boundaries of a kinematically redundant manipulator

Abstract

In addition to possessing a number of other important properties, kinematically redundant manipulators are inherently more tolerant to locked-joint failures than non- redundant manipulators. However, a joint failure can still render a kinematically redundant manipulator useless if the manipulator is poorly designed or controlled. This paper focuses on the implementation issues involved in identifying a region of the workspace for which task completion is guaranteed in the event of a locked-joint failure for a general class of planar 3R manipulators. The existence of such a region, called a failure-tolerant workspace, will be guaranteed by imposing a suitable set of artificial joint limits prior to a failure. The authors have developed a graphical user interface (GUI) that computes all workspace boundaries of interest for the planar 3R manipulators. This GUI allows the user to explore different robot geometries, and adjust the artificial joint limits, in an attempt to gain further understanding of a manipulator's failure-tolerant workspace.