Dynamic hybrid position/force control of robot manipulators-on-line estimation of unknown constraint

A dynamic hybrid position/force control method, which takes into consideration the manipulator dynamics and the constraints on the end-effector specified by the given task, is obtained by extending the method of M.H. Raibert and J.J. Craig (1981). One difficulty in implementing the method is that precise information on the size and position of the object with which the end-effector contacts is not usually available. To cope with this difficulty, a problem of dynamic hybrid control with unknown constraint is studied. An online algorithm is developed that estimates the local shape of the constraint surface by using measured data on the position and force of the end-effector. It is shown by experiments, using a SCARA-type robot, that the combination of this algorithm with the dynamic hybrid control method works fairly well, making the dynamic hybrid control approach more practical.>