A cooperative fault tolerance strategy for distributed object lifting robots

A distributed and cooperative fault-clearing strategy for a team of object lifting robots is introduced It is assumed that one of the robots misses a portion of its lifting power and the robots must redistribute the load among themselves to perform their task. Two distributed and cooperative methods for the load reallocation among the position-controlled robots without requiring them to change their grasp positions are introduced. The first method benefits from the existing redundancy in the number and in the lifting power of the robots. In the second method, the object is tilted in order to move the ZMP (Zero Moment Point) away from the faulty robot and, consequently, redistributing the load. Difficulties in controlling ZMP movements are pointed out. Therefore, the second fault clearing procedure is designed such that the ZMP position is controlled without resorting to sophisticated or centralized control algorithms. The stability of the proposed methods is discussed. Simulation results are given to support the developed methods.