Tracking control of a giant magnetostrictive actuator with stress-dependent hysteresis compensation

Effective employment of giant magnetostrictive actuator (GMA) is limited in trajectory-tracking applications due to hysteresis nonlinearity, especially it is stress-dependent. In this paper, the properties of stress-dependent hysteresis for GMA are studied and a stress-dependent hysteresis model is given by extending modified Prandtl-Ishlinskii model to describe hysteresis effects. The identification method of this model is given and constraint conditions are also discussed to guarantee the unique existence of its analytical inverse, which is attractive to real-time control. Subsequently, the inverse stress-dependent hysteresis model is applied to cancel the hysteresis of GMA for the real-time microposition tracking control. A comparison is made between control with stress-dependent hysteresis compensation and control with stress-independent hysteresis compensation. Experimental results show that RMS tracking errors are reduced by if the rate-dependent hysteresis compensation is added. In order to improve control accuracy, a PID feedback controller is incorporated with a feedforward loop. Experimental results show that tracking results are improved greatly by augmenting the feedback loop with hysteresis compensation in the feedforward loop.