Dexterity optimization of kinematically redundant manipulators in the presence of joint failures

Abstract

Robotic manipulators working in remote or hazardous environments require additional measures to ensure their usability upon the failure of an actuator. This work considers failure modes that result in an immobilized joint and uses the concept of worst-case dexterity to define kinematic and dynamic fault tolerance measures for redundant manipulators. These measures are then used to specify the operating configuration which is optimal in the sense that the manipulator's dexterity remains high even if one of its joints fails in a locked position. The close relationship between fault tolerance and dexterity is examined using a simple planar manipulator as an example. It is demonstrated that an inverse kinematic function which maintains a high level of fault tolerance also keeps the manipulator in well-conditioned configurations known to have desirable properties.