Decentralized Admittance Control for a Multi-manipulator System: Implementation and Analysis

A decentralized strategy for object transportation is presented, assuming that the object is grasped by a team of N cooperative manipulators. The proposed strategy consists of two steps. First, each robot estimates the wrenches applied to the object by all the others robots, even without all-to-all communication. Second, an admittance control scheme is used to limit internal wrenches, preventing excessive stresses that could affect manipulation stability and object integrity. Stability is proven under the assumption of a spring connection between each robot end-effector and its grasping point on the object. A work cell with two 7-degree-of-freedom (DOF) and one 6-DOF robotic manipulators was used to validate the strategy. Experimental results show that the controller effectively reduces internal wrenches, confirming the feasibility and robustness of the decentralized approach in cooperative manipulation.