Linear piezoelectric motor using a hollow rectangular stator

We propose a linear piezoelectric motor using a hollow rectangular stator that can translate a load placed inside it by a direct-drive. This stator structure enables a quick response and high resolution by few components. These advantages are suited for controlling autofocus and zoom mechanisms in imaging devices. In this study, we verify the feasibility of the driving principle that uses two vibration modes in the bending and longitudinal direction of a hollow rectangular plate. We design a hollow linear piezoelectric motor by a finite element method analysis and evaluate the performance of the prototype motor by experiments. In the prototype motor, the stator measures 60 mm in height and width and 4.1 mm in thickness (the length in slider travel direction), and a slider with a side length of 42 mm is inserted into the stator. The performance parameters of the linear motion, such as thrust force and speed, are evaluated experimentally. By optimizing the preload between the stator and the slider, the motor thrust force has improved to over 0.5 N at 70 V_p−p, which is a practical force for moving a certain lens unit.