A relay-based method for servo performance improvement

This paper proposes a relay-based performance-improving method for servo mechanism systems. The method first utilizes a relay-based feedback technique to identify the model parameters and the Coulomb friction value. Then, based on the identified results, a control algorithm, which consists of a feedforward controller, a time-delay compensator and a sliding mode controller, is designed. The feedforward controller and the time-delay compensator are used to compensate the system dynamics and the external disturbances respectively. Their parameters are decided directly according to the identified values. The sliding mode controller is to stabilize the system, two of whose parameters are one-to-one mapping to the closed-loop characteristic roots. Thus, this method avoids the complicated parameters tuning process, which is attractive in practice to the control engineers. Experimental studies on a linear-motor-driven table illustrate that the proposed method is capable of improving the servo performance greatly and canceling the external disturbances effectively. (C) 2011 Elsevier Ltd. All rights reserved.