Effect of Application Mode of Friction Material on Driving Characteristics of Ultrasonic Motor

Friction material is one of the most important parts in ultrasonic motor. Its application modes affect directly the characteristics of ultrasonic motor. Using two traveling wave ultrasonic motors which the friction material was applied on rotor and stator, respectively, then the rotor and stator were matched with their corresponding stator and rotor to simulate the contact behavior of ultrasonic motor. The variations of load and wear properties of ultrasonic motor with the application modes of friction material were studied. Impedance characteristics of the stator were measured by impedance analyzer before and post applying on friction material layer. The unworn and worn surface morphologies and surface roughness of contact surfaces of the two ultrasonic motors were studied by metalloscope and JB-4C precision roughness instrument. The wear mechanism was analyzed. The results showed that resonance frequency of stator with friction material on decreased slightly. The motor with friction material applied on stator obtained higher stall torque at two ultrasonic motors without loading at same speed. Polishing wear was the dominant mechanism of the stator with friction material, while ploughing wear was the dominant mechanism of the rotor with friction material.