Two Degrees of Freedom Position Control using Reference Model for Motor Drives

When a servo motor controlled by the conventional PI controller is employed to drive a mechanical load such as a robot manipulator, the response of position control is limited because of the elasticity and the non-linear characteristics of the mechanical load. In order to solve this problem, we propose a new position controller based on the two degrees of freedom control method. In this controller, we incorporate a reference model which is a position control system model with desirable dynamic performance. By utilizing the output signals of this reference model as feedforward control signals, the command input response can be improved to a great extent independent of the disturbance response which is affected by the characterisitics of the mechanical load. We also propose an auto-tuning method of this controller. Experimental results clarify that our controller has excellent dynamic performance compared with the conventinal PI controller and show that the auto-tuning of the controller gains is executed correctly.