Saturation avoidance methods for serial robots operating under a failure

When a robot actuator fails and loses some of its capabilities, the task of a fault-tolerant controller is to isolate the failure and complete the ori ginal task without interruption. As the robot controller attempts to accomp lish this demanding task, it may encounter the unexpected problem of actuat or saturation since the original task needs to be done with reduced resourc es and likely extra control efforts due to the compensation for large error s. To deal with this challenging problem, torque redistribution method and time regulation method are presented. These methods are tested on the model of a 4-degree-of-freedom revolute serial robot. The simulations provide en couraging results to verify the two methods to be able to tackle the satura tion avoidance problem. A basis of comparison for these methods employed on a serial robot is also addressed. (C) 1999 John Wiley & Sons, Inc.