Robotic grinding force regulation: design, implementation and benefits

The design and implementation of force control for robotic rigid disk grinding are described. Experiments were conducted using a PUMA 762/VAL II industrial robot equipped with a 4-hp pneumatic grinder and a JR³ force sensor. An external, 386-based host microcomputer, communicating with VAL II online, performs the force control algorithm calculations. The robotic grinding force model used was an experimentally verified analytic model. It was found that the grinding forces are very sensitive to the robot arm stiffness. Also, the end-effector path tracking errors, caused by the limited accuracy of the PUMA robot, significantly affect the grinding forces. The experimental results show, however, that a finely tuned PID force-feedback controller is able to maintain the grinding forces at a specified value. It can effectively compensate for force errors caused by both step force disturbances and robot path-tracking errors. The benefits of such force control are demonstrated by improved profiles of finished workpieces