Delta-shaped piezoelectric ultrasonic motor for two-dimensional positioning

By fabricating on from lambda-shaped motors, bimorph delta-shaped motors have been developed and tested. A delta motor consists of two piezoelectric layers (bimorph structure) with four input electrodes and one common ground electrode-separated by an inactive bar that aids dimensional control in the sintering process. Two driving sources with a 90 degrees phase difference were used for the x-, z-, and diagonal-axis direction driving. The design of the motor was modified and optimized by changing the relative dimensions and angle of the motor with the aid of ATILA finite element method (FEM) software. The optimum design with a small bandwidth between resonance modes, which provides the largest elliptical displacement, was fabricated using thick films. The fabricated motor size was below 10 mm 2 with several hundreds of nano meter motion at the tip. The speed of revolution, torque and efficiency in the two-dimensional space were measured.