Self-sensing control of piezoelectric positioning stage by detecting permittivity

• The differential current measurement method is effective for precise positioning control.
• The positioning errors due to hysteresis decreased from 0.8 μm to 0.1 μm for a 10 μm displacement range.
• Permittivity feedback control could reduce the positioning error to ±0.10 μm at most, whereas open-loop control could only reduce it to ±0.45 μm.
• The creep property also could be reduced by permittivity feedback.

Piezoelectric displacement contains hysteresis and creep properties. Therefore, a displacement sensor is indispensable in precise positioning devices; however, the additional space and cost are problems. On the other hand, self-sensing methods that utilize the piezoelectric actuator itself as the displacement sensor have been proposed. With these self-sensing methods, precise positioning becomes possible without an additional displacement sensor. We developed a self-sensing method utilizing the non-hysteresis relationship between the permittivity change and the piezoelectric displacement. Furthermore, a differential current measurement method using two piezoelectric elements with a bimorph actuator could improve the positioning accuracy. In this study, we examine the control of a positioning stage using two multilayered piezoelectric actuators by applying the differential current measurement method for self-sensing control. The results indicate that the differential current measurement method is effective for precise positioning control. The positioning errors due to hysteresis decreased from 0.8 μm to 0.1 μm for a 10 μm displacement range. In addition, permittivity feedback control could compensate for the creep property.