Experimental characterization, modeling and compensation of rate-independent hysteresis of voice coil motors

The hysteresis nonlinearities of a voice coil motor are characterized under different amplitudes and bias levels of input current signals. The measured data reveal that the asymmetric characteristics of the output-input hysteresis loop are strongly dependent on the amplitude and bias of the input signal. A modified Prandtl-Ishlinskii model is proposed in this study to model the rate-independent hysteresis nonlinearities of a voice coil motor. The proposed hysteresis model is composed of a series of generalized operators and an input function based on Fermi-Dirac distribution. Comparisons of the model responses with the measured data under different amplitudes of input current signals indicate that the proposed model can effectively describe the rate-independent nonlinear hysteresis properties of the voice coil motor within the travel range of 4.3 mm. Subsequently, the inverse of the proposed Prandtl-Ishlinskii model is obtained analytically. The inverse model is utilized as a feedforward compensator to compensate the rate-independent hysteresis nonlinearities without using feedback control techniques. The compensation experiments are performed to verify the validity of the inverse model.