Position control and explicit force control of constrained motions of a manipulator for accurate grinding tasks

On the basis of an analysis of the interaction between a manipulator for a grinding process and a working object in the task space, motions of the constrained dynamic system of the robot are modeled first in this paper. In the model, the constrained forces are included and expressed as a function of the state and input generalized forces by using the equation of constraints. Using this result, a control law is proposed by taking advantage of the redundancy of input generalized forces to the constrained forces. A controller for the grinding robot is then constructed according to this control law and without involving any force sensors. Simulations have been done for justifying the feasibility of the controller by taking an articulated planar two-link manipulator as an example. Results show that the constrained force is explicitly controlled with the proposed control law and the effectiveness of the controller has been verified.