Grinding experiment by direct position / force control with on-line constraint estimation

Based on the analyses of the interaction between a manipulator's hand and a working object, a model representing the constrained dynamics of the robot is first discussed. The constrained forces are expressed by an algebraic function of states, input generalized forces, and constraint condition, and then direct position / force controller without force sensor is proposed based on the algebraic relation. To give the grinding system the ability to adapt to any object shape being changed by itself, we added new estimating function of time-varying constraint condition in real time for the adaptive position / force control. Evaluations through simulations and real grinding experiments by fitting the changing constraint surface with spline functions, indicate that reliable position / force control and shape-grinding can be achieved by the proposed methodology.