Computing fault tolerant motions for a robot manipulator

We introduce a method of planning fault tolerant trajectories based on the least constraint (LC) framework. Fault tolerance is achieved in two ways: exploiting properties of LC itself, and using a performance measure which assess the fault tolerant potential of a given configuration. LC encourages designs which are based solely on salient constraints of the task, allowing the inherent redundancy of the robot to be used to maintain a safe configuration. We compute the effects of faults on the topology of the configuration space and construct optimal recovery motions for a set of faults. We describe an efficient algorithm for computing the optimal recovery motions for a large number of faults over the entire configuration space simultaneously. A performance measure, called longevity, quantifies the ability of the recovery motions to complete the task. From the performance measure fault tolerant paths are constructed. We look at the simple task of positioning the end effector of a Puma 560 at a given point in the workspace.