High-speed force controller for SCARA robots

The SCARA (selective compliance assembly robot arm) robot has horizontal compliance. However, the amount and direction of compliance must be controlled before the robot can be used in actual applications. The authors have developed an active compliance controller that uses force sensors on the wrists of the robot to determine the contact forces acting on the end effector. The sensors feed this information to the trajectory generator of the robot controller. The controller achieves high-speed control (the sampling time is 1 ms) by performing all control operations in parallel using two MB8764 digital signal processors. The stability of the control was analyzed for joints having an arm that is not rigid. The force control can be stabilized by keeping the force feedback gain reasonably small