The Principle Behind Our Piezoelectric Motors

PCBMotors consist of two parts: The Stator, which holds the actuators and electrical connecting circuit; and The Rotor, which is pressed onto the surface of the stator and delivers the mechanical output.

A traveling wave is generated over the stator surface, acting like a flexible ring to produce elliptical motion on the rotor interface. The elliptical motion of the contact surface propels the rotor and the connected drive-shaft. The teeth attached to the stator can be used to increase rotational speed. Operation depends on friction between the moving rotor and stator as well as amplitude and quality of the wave traveling on the stator.

basicstatorA traveling wave is generated within the stator by activating two modes simultaneously. These modes are induced by a drive circuit performing cos(w t) and sin(w t) signals, respectively, close to the mechanical resonance of the stator ring. The traveling wave’s direction can be reverse by changing the sign on one of the drive signals. RotorThe rectification of the micro-motion is achieved by pressing the rotor on top of the stator. The frictional force between the two causes the rotor to spin. The resulting motion transfer operates as a gear and leads to a much lower rotation speed than the wave frequency. The rotor could be a special ring-shaped material attached to an output shaft, or it could be an integral part of the application that needs to be turned. Since the rotor is a passive component there is a great deal of freedom in the design. Most important is the surface behavior which must be compatible with the stator teeth material in order to produce the friction needed to drive the application.