Coordinating two serially connected robots for generating large Cartesian velocities

Two serially connected robots in which the base of one robot is held by the end-effector of the other are more capable than a single robot. Serial connection of two robots can enlarge work space and generate large Cartesian force and Cartesian velocities. Two coordination methods are proposed for the robots to generate large Cartesian velocities while avoiding degeneracy. The first method, which is based on a least-energy consumption criterion, decomposes a desired Cartesian velocity into two velocities, one for each robot. Robot joint velocities are then adjusted using a null space approach to avoid degeneracy. The second method includes a degeneracy index in the cost function. As a result, joint velocities are obtained without any further adjustment. For real time applications, computationally simple methods are presented. The results are verified by case studies