A Hybrid Feedforward-Feedback Hysteresis Compensator in Piezoelectric Actuators Based on Least-Squares Support Vector Machine

Hysteresis nonlinearity of piezoelectric actuators degrades the positioning accuracy of micro/nanopositioning systems. To overcome this problem, an innovative hysteresis compensator based on least-squares support vector machine (LSSVM) is proposed in this paper. First, the LSSVM hysteresis modeling is presented using nonlinear auto regressive eXogenous (NARX) structure. To compensate for the hysteresis behavior, two feedforward control schemes according to different inputs of NARX model are proposed and analyzed separately. Then, a hybrid feedforward controller combining both the control schemes is put forward to revise the model input. To further improve the tracking performance, the hybrid feedforward control combined with the feedback control is realized. The comparative study reveals the superior tracking performance of feedforward-feedback control scheme over hybrid feedforward control or feedback control. Moreover, the hybrid feedforward-feedback control scheme is capable of tracking different testing waveforms with negligible errors, which confirms the effectiveness and generalization ability of the proposed approach.