PID and PDFF Compensators for Motion Control

Traditionally in servo systems, the PI(D) controller has been widely used, while other types such as the PDF controller has been applied in some applications. In this article, the PDFF controller which has feedforward term in addition to a conventional PDF(Pseudo-Derivative Feedback) controller is introduced. Tracking and regulation characteristics of the PDFF controller in motion control applications are analyzed in terms of classical frequency domain approach. The PDFF controller is shown to be a generalized PI(D) controller, and relative performance of the well-known cascade PI(D) controller and the PDF controller are dealt with as two special cases. A tuning method of this controller to meet desired performance criteria such as dynamic reference tracking, steady-state error and load torque disturbance rejection capability is discussed along with experimental results.