Failure tolerance through active braking: A kinematic approach

For a manipulator operating in a hazardous or remote environment, an import ant concern is its capability after a component failure, since retrieval or repair is not always possible Methods have been presented in the literatur e for optimizing capabilities after specific types of failures. However tec hniques for achieving failure tolerance when conversion between failure typ es is possible has not been fully explored. This paper presents an approach to improving postfailure performance by converting between locked-joint fa ilures and free-swinging failures through active braking. When a manipulato r is moved slowly, gravitational forces can be used to control the failed j oint in free-swinging mode, allowing the problem to be cast as a kinematic one. The validity of the kinematic formulation and its implementation and g lobal consequences are explored.