The robustness of an admittance control law designed for force guided assembly to the disturbance of contact friction

The design of an admittance control law for reliable force-guided assembly is addressed. The overall objective is to design the manipulator´s mechanical performance so that, at each possible bounded part misalignment, the contact force always leads to a motion that alleviates the misalignment. The implementation of such an approach using a single nominal velocity and a single admittance function is referred to as force-assembly. Previous work addressing force-assembly of a workpiece into a fixture has shown that when workpiece/fixture contact is frictionless there always exists an admittance control law that ensures the proper insertion of a workpiece into a deterministic future. The authors discuss the identification of the condition that must be satisfied for force-assembly with friction and the optimization of the admittance control law to obtain the maximum value of friction that satisfies the force-assembly conditions for a given workpiece-fixture combination