Fractional-order composite control for the transient creep of a piezoelectric actuator

In this study, a fractional-order composite controller is proposed to decrease the settling time and narrow the range of the transient creep of a piezoelectric actuator. The controller is composed of backlash modules and a fractional-order PIλ controller. The backlash modules reduce the effect of the transient creep and the hysteresis, while the fractional-order controller decreases the settling time. Experiments show that the settling time is decreased from 11 ms to 6 ms. The controller exhibits good performance on step creep and hysteresis when the input signal is discretised into steps, whether 10, 20, 40 or 80 steps. All standard deviations are suppressed to levels 39.3% lower than that of a standard PI controller and the range of the transient creep is reduced to 19.46%.