A JOINT ERROR-FEEDBACK APPROACH TO INTERNAL FORCE REGULATION IN COOPERATING MANIPULATOR SYSTEMS

When two or more open chain manipulators cooperate to manipulate the s ame object-such as in mechanical grippers, walking machines, and coope rating manipulator systems-closed kinematic chain, redundantly actuate d mechanisms are formed. Control approaches for this type of system fo cus on the more computationally intensive inverse plant control laws o r on hybrid force-position techniques. Although local control schemes, using only position and rate errors to generate control forces, are w idely used for control of open-chain serial-link robotic mechanisms, t hese simple and effective control laws have not been considered for co ntrol in cooperating manipulator applications because of concerns over instability due to the unspecified distribution of control forces amo ng the redundant control actuators. Recent work has shown that the loc al approach to cooperating system control results in a known force dis tribution among the control actuators and can be proven globally stabl e with a reasonable choice of control parameters. In this work, the kn own distribution of forces in the cooperating systems is used to devel op an analytic description of the internally transmitted forces seen b y the cooperating systems using the local control scheme. This descrip tion of the internal forces is used to modify the trajectory command i n such a way as to control the internal forces of the system. The resu lting control law is shown in simulation to produce good trajectory tr acking as well as desired internal forces. (C) 1997 John Wiley & Sons, Inc.