Design, fabrication, and evaluation of stepper motors based on the piezoelectric torsional actuator

This paper deals with the newly developed piezoelectric stepper motors that generate the precise stepping motion using a piezoelectric torsional actuator and a pair of one-way roller clutches. The torsional actuator consists of piezoelectric segments that produce the angular motion associated with its shear mode of piezoelectric ceramics, d15. A pair of one-way roller clutches converts the angular motion of the torsional actuator into continuous stepping rotation with a driving shaft. Because the piezoelectric torsional actuator functions as the driving source at high frequency, a precise step motion can be produced without any conversion mechanism of stepping rotation. In this paper, two types of torsional stepper motors are designed and fabricated. In the design stage, the shear resonance mode of the piezoelectric actuator is analyzed by using a finite-element analysis, and rotation speed and torque measurement are performed. Also, possibility of achieving higher rotation speed using a torsion bar is addressed. Once the proposed piezoelectric stepping motor is miniaturized, it can be used for many compact and precision motion applications.