Abstract
A new method of generating an optimal approach velocity of a manipulator to its environment is presented in order to control the collision forces properly. First, analysis of a contact motion shows the necessity of contact control not only after the collision, as in previous studies, but also before it. Next, using a model of the force-controlled end-effector and its environment, forces generated at the contact are formulated as outputs of an autonomous system of which the initial condition is determined by the approach velocity. The optimal approach velocity is defined as the velocity which minimizes a performance index : the integration of the square deviation of contact forces from an equilibrium forces in the control of contact forces. A proportional relation between the optimal approach velocity and the contact force reference is derived analytically based on a mass-damper-spring model of the force-controlled end-effector and its environment. Results in simulation and experiment are presented to prove the effectiveness of the method.
