A miniature disk-pivot piezoelectric motor with double rotors

A miniature disk-pivot piezoelectric motor with double rotors using a vibration mode B11 of one nodal circle and one nodal diameter was designed and fabricated. A disk-pivot structure is used to simulate the wobble vibration and an embedded metal cylinder is used to amplify the displacement to obtain a higher rotation velocity. The structure of the stator is analyzed by using Finite Element Method (FEM) and the vibration mode B11 which the motor needs to drive the rotors is optimized to avoid the influence of any other vibration modes. Compared with the previous piezoelectric motor with one rotor and one ceramic disc structure, the double rotors can result in a lower resonant frequency and a higher output torque of about three times. The outer diameter of the metal/piezoelectric disk and the embedded cylinder is 14 mm and 2.5 mm, respectively. The length of the embedded metal cylinder is optimized to be 7.8 mm. The vibration mode B11 is measured by the laser scanning vibrometer and the resonant frequency is 32.9 kHz. The rotation speed is measured, which could be as high as 7500 rpm under an alternating current 100 Vo-p, and the maximum stalled torque is 0.3 mNm.