Constrained motion control of a robot manipulator

Monitoring of contact type is important to achieve tasks in which an end-effector holding an object makes contact with the constraint surface. The force exerted by the end-effector is usually controlled in a direction normal to the constraint surface, while the position of the end-effector is maintained in the tangential direction. In the paper, the position and force degrees of freedom are specified for constraint surfaces depending on the type of contact. Three types of contact (point, line, and plane) are considered. The type is determined based on the point of contact which is calculated from information received from a wrist force/torque sensor. Experimental results verify the technique for obtaining the type of contact. A reduced order position/force control method is then applied to effectively control the manipulator in orthogonal directions. An example is presented to demonstrate the technique