From Piezoelectric Actuator to Piezomotor

This paper discusses the ways to achieve a macroscopic motion from the very small strain generated in basic piezoelectric actuators. The first part reviews the operating principle and force-displacement characteristics of some types of piezoelectric actuators, bulk-type, multilayer, benders, flextensional and Langevin transducers. The second part focuses on the different ways to convert this small displacement into macroscopic sliding motion, usually through friction forces. Regardless of the actual use of the active piezoelectric elements, it is shown that the characteristics of each motor can be derived from the trajectory of the contact point between the active stator and the slider, either with a reversible or hysteretic motion. Finally, the third part shows two recent prototypes of piezomotors that have been built and tested in our lab: an Inchworm and a linear-traveling-wave motor.