Symmetric kinematic formulation and non-master/slave coordinated control of two arm robots.

Abstract

Tasks consisting of manipulating an object with two cooperating robots are studied from the standpoints of statics and kinematics; coordinates to describe these tasks are derived theoretically, on which forces, velocities, and positions are defined consistently. Based on those results, a hybrid position/force control scheme which distinguishes neither a master robot nor a slave robot is presented for the coordination of the two robots. In the static and kinematic analyses, the concept of a 'virtual stick' is introduced, which is used to make the motions of the two robots be considered at the centre of the object. Thus, use of the matrix pseudo-inverse technique decouples the motions into absolute and relative motions. Generalized forces, velocities, and positions are derived theoretically in those decoupled subspaces. These forces, velocities, and positions are symmetric functions of the jointspace forces, velocities, and positions. Therefore, the hybrid position/force control scheme using the workspace coordinates derived in this paper is capable of controlling independently either positions or forces on those coordinates without distinguishing a master robot or a slave robot: tasks such as carrying an object by pushing or pulling it with two robots are realized in the framework of a non-master/slave scheme.