10.1.1. Traveling wave ultrasonic motors: technology and usage
Traveling wave ultrasonic motors make use of the mechanical vibration of a stator to drive – by friction – a rotor, strongly, which is held against the stator [SAS 93]. The vibration is obtained by the excitation of small piezoelectric elements which deform under the action of a transverse electric field. Figure 10.1 shows a diagram of the piezoelectric motor on which the deformations of the stator are exaggerated.
Traveling wave piezoelectric motors are considered to be 2-phase motors which are supplied with two alternating sinusoidal voltages and are referred to as and . Under the inverse piezoelectric effect, the electric field generates in the exciters’ deformations; for each voltage considered independently, a standing deformation wave is established which is combined with the other to propagate a traveling wave. It is this traveling wave which seems to rotate around the axis of the motor that allows the generation of torque.
Thus, contrary to electromagnetic motors, the ...