Piezoelectric motors suffer from a relatively short operating life. Increasing the durability of the motor requires an understanding of the failure modes of the motor and implementation of a strategy to couteract them. To this end, a study of the stresses in the stator of the traveling-wave piezoelectric motor has been performed at S&T and Honeywell, KCD. In particular, stresses near the edges of the motor have the largest influence on the life of the motor. Reducing these stresses and determining their magnitudes are current research topics.
FE Analysis of 8 mm Ring Motor Operation MPEG (349K)
FE Analysis of 0.668" Disk Motor PZT Internal Stresses (34K)
FE Analysis of 0.668" Disk Motor Stator Vertical Deflection (51K)
FE
Analysis of 0.668" Disk Motor Stator Von Mises Stresses (51K)
An overall model of the traveling-wave piezoelectric motor has been formulated by James Friend and Dr. Dan Stutts at S&T. It includes a complete piezoelectric forcing model, an annular plate vibration analysis with prediction of the resulting motion of the attached teeth, and a contact model to predict motor torque and speed. A preprint of a paper submitted to the Journal of Sound and Vibration is here and some of the results of the model is provided in the following figures for an 0.668" disk traveling-wave motor. A subsequent paper is in preparation that describes the contact model used in these figures.
Forcing due to PZTs on Stator Plate (51K)
0.668" Disk Motor Plate Mode Shape due to Forcing (Analytical Prediction) (51K)
Analytical Prediction of Tooth Displacement of 0.668" Motor (60K)
Deformation of friction liner due to teeth in 0.668" Motor (9.7K)
Normal force between teeth and friction liner in 0.668" Motor (17K)
Tangential friction force between each tooth and friction liner of 0.668" Motor (17K)
Dan Stutts has written a short paper on the relationship between the impedance measured with a piezoelectric beam and the electromechanical coupling in the beam. The paper is available here.
A large amount of literature has been written on piezoelectric motor systems, primarily related to motor designs and control system designs. There are a large number of patents related to the motors as well. In our reference list, we provide a large number of references to these papers and to related works important for anyone preparing to work with the motors.
One of the difficulties in making the piezoelectric motor is the bonding of the piezoelectric layers to the stator. This note contains some suggestions for improving the bonding in the stator.