Those piezo motors are very useful for small spaces and are quite cost effective. I’ve used them a couple of times on projects at work for positioning and very fine control is achievable due to the minute step size. You can think of them as tiny powered ratchet mechanisms arranged either linearly or in a ring. Each piezo element is arranged so as to contact the driven surface at an angle. When a voltage pulse is applied the piezo chips action is to move the driven surface forwards and slide back on the return part of the stroke. Think of it as having two different frictions higher in the drive direction. To allow bidirectional movement and to create the other frictional part of the ratchet two rows of piezo motor elements are arranged in opposition.
Positional feedback, at least on my projects which were microscope stages and filter actuators, is by optoelectronic scales.
As the motors are essentially piezo chips soldered to PCBs they are very easily designed to make in whatever size and shape you wish. We discovered that the company we used would and did make a motor to our spec as a one off.
They don’t handle loads except for the force produced in the driving direction so bearings etc have to be designed in to the device that the motor is fitted in.
For camera focusing rings they could be termed ultrasonic as the piezo chips are actuated at those sort of frequencies. Each ‘step’ is tiny so to move fast the signal frequency needs to be high.
I was impressed with them.
regards Martin
Edited By Martin Kyte on 23/07/2023 10:01:47