A differential motion planning algorithm for controlling multi-robot systems handling a common object

Multi-robot systems have substantially increased capabilities over single-robot systems and can handle very large or peculiar objects. This paper presents a differential (incremental) motion planning algorithm for an m-robot system (m >or=2) to cooperatively transfer an object from an initial to a desired final position / orientation by rigidly holding it at given respective points Q[sub 1], Q[sub 2],..., Q[sub m]. One of the robots plays the role of a "master" while other robots operate in the "slave" mode maintaining invariant their relative positions and orientations during the system motion. The method employs the differential displacements of the end-effector of each robot arm. Then, the differential displacements of the joints of the m robots are computed for the application of incremental motion control. The algorithm was tested on many examples. A representative of them is shown here, concerning the case of three STAUBLI RX-90L robots similar to 6-dof PUMA robots. The results obtained show the practicality and effectiveness of the method, which, however, needs particular care for completely eliminating the cumulative errors that may occur.