Wedge-type piezoelectric motor is easily subject to disturbance such as friction, preload and temperature change, which influences the performance significantly and reduces the positioning accuracy and reliability. In this study, Exponentially Weighted Moving Average (EWMA) method is considered to use for the velocity-feedback loop, which is included in an Internal Model Control (IMC) to achieve a Run-to-Run IMC (RtR-IMC) control structure. Such control scheme is able to adapt the control command following a changing system dynamics so that it can improve the tracking accuracy and robustness. Friction is also a problem of generating dead-zone area and causes serious nonlinear phenomenon especially while moving direction is changed. A feedforward controller is designed based on the friction model. Moreover, temperature increase appears in long-time operation, which is another factor influential to piezoelectric motor’ performance. Instead of using the Single EWMA method, which cannot efficiently deal with such environmental drift problem, a Double EWMA algorithm is developed. Practical experiment is carried out to verify the performance by using these proposed methods. It concludes that the Double EWMA associated with the friction-model-based feedforward controller is superior to the other methods.

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