The optimization of a symmetrical coplanar trimorph piezoelectric actuator

Piezoelectric actuators are widely used for different applications such as high precision positioning devices, micromanipulation systems, scanning microscopes, and robotic systems. This paper introduces a compact size symmetrical coplanar trimorph piezoelectric actuator for high speed (up to 5000 rpm) rotary motors. The actuator consists of a hollow carbon cylinder and a disc-type coplanar piezoelectric trimorph actuator. The cylinder is glued in the center of the trimorph disc. The electrodes of the piezoelectric layers of the actuator are divided into the four equal sections. Four electric signals with shifted phases by π/2 are applied on the different electrodes, and traveling wave oscillations of the disc and rotational motion of the cylinder are excited. Numerical modelling based on the finite element method was performed to find the resonant frequencies and modal shapes of the actuator and to calculate the trajectories of contact point movements. The optimization of the actuator design has been performed to maximize the oscillation amplitude of the contact point. A prototype actuator was then made, and measurement of the actuator's resonant frequency and rotational speed has been performed. The results of the numerical and experimental investigation are analysed and discussed.