Designing piezoceramic actuators and motors

Abstract

Piezoelectric actuators have high energy densities and are capable of producing high force, high bandwidth output. However, they lack the stroke required by many practical applications. Solid-state mechanisms have been designed that utilize flexure hinges to efficiently amplify the stroke of a piezoelectric stack element up to five times. The designs avoid the losses encountered in traditional hinge joints, which are primarily due to tolerance problems, and they minimize losses due to material strain. The mechanisms have been successfully employed in micropositioners for several different applications, including mirror positioners for wavefront compensation and proof mass actuators for vibration suppression. Piezoceramic actuators have also been employed in very high stroke mechanisms: linear and rotary motors. These motors fall into two classes, the ultrasonic motors and the quasistatic type motors. The ultrasonic motors, such as the traveling wave motor, must run at very high frequencies, usually at the resonance frequency of the stator. The quasistatic type motors, such as the inchworm motors, are able to run at low frequencies, but also can be operated at resonance to achieve higher speeds. Both inchworm motors and ultrasonic motors have been successfully demonstrated as prototype devices.