Linear Piezoelectric Actuator

Linear actuators have been developed in many research fields and industries because of the increased demand for high precision positioning systems. Especially, linear actuators were recently employed to a component in various types of camera equipment such as a zoom, Image stabilizer.
I would like to tell you about linear actuators that I have developed. One of actuators that I involved is Tiny Ultrasonic Linear Actuator (TULA). Actually, I didn't evolve the development of  this actuator it self but  I have studied on control method for this actuator. The reason why I'd like to introduce about it is that it's one of the very interesting and attracting linear actuators. The structure and principle of this actuator shows below.



1. Structure and principle of TULA (HP Ko et al., 2006 and WS Jung et al., 2009)



As shown, it has very simple and tiny structure. The diameter of this actuator I used is approximately Ø3 mm. it uses inertia displacement. For instance, the shaft and mobile element goes up together when the shaft slowly goes up, and then if the shaft goes down quickly, the shaft goes down, leaving the mobile element because of the inertia displacement, and vice versa. If you want to know its information more, please take a look at www.piezo-tech.com. For your convenience to understand this linear actuator, I inserted movies below (from Piezo-tech.com).

What is an ultrasonic motor?

Basically, an USM (Ultrasonic motor) consists of a rotor, a stator, and piezoelectric ceramics.
Here, Piezoceramics can produce electricity when subjected to mechanical stress like a hit, twist, pressure, it called Piezoelectric effect. On the contrary, when the electricity is given to piezoceramics, it can be contracted or expanded to certain direction. this is inverse piezoelectric effect. USMs use this effect.
USM is based on ultrasonic vibrations of the stator, obtained by piezoceramics. Another component, the rotor can be moved by this vibration.
Why uses USM? because it has the following advantages:
high resolution, quick response, low power consumtion, no break mechanism, small size and weight, no electromechanical noise, and so on.
Today, I'd like to briefly introduce a rotary typed ultrasonc motor.

Left figure shows the structure of the rotary typed USM produced by Piezo technology in Korea. Many pieces of piezoceramics attached to the stator (white color), and the rotor and stator combine with pressure of the spring. when the stator generates vibrations such as a travelling wave, the rotor can be moved by friction between the stator.
below shows the simulation of rotary typed USM and movie of panasonic usm to help you understand better.  I'm currently developing MRI-guided prostate surgical robot with this typed USM.