Piezo technology in "beetle drive"

Edited by the Engineeringtalk editorial team Sep 4, 2003

A linear motor the size of an insect and able to lift 1000 times its own weight is now available from mechatronics expert Unimatic Engineers.

A linear motor the size of an insect and able to lift 1000 times its own weight is now available from mechatronics expert Unimatic Engineers.

The design is based around pairs of piezoelectric swinging legs that allow the motor to 'walk' and was developed by Swedish company PiezoMotor.

Piezo technology is based on a laminate of ceramic layers, each of which expands by a different amount when subjected to a tiny electrical charge.

Because the layers are bonded one to another, the differential expansion between the layers causes deflection out of the plane of lamination, in a manner similar to a bimetallic strip.

Thus a piezoelectric leg can be made to flick back and forth and imitate walking.

The voltages involved are so tiny that they pose no danger to operators, nor could they even cause a spark which could trigger a larger problem.

Similarly the legs of the piezo motor are miniscule, but speeds up to tens of millimetres per second can be achieved because they can swing at 10,000 steps per second or more.

This also allows accuracy and resolution of positioning to nanometre levels.

It is expected that the motor will be custom designed for each application, although Unimatic will be promoting the technology using demonstrator units which are about 20mm long and weigh 20g.

The associated control electronics are similar to those required for a conventional brushless motor.

"This is a fundamentally new technology", explains Unimatic's MD Martin Stevens, "so we are developing a strategy to introduce it to potential users".

He expects early uses to be as replacements for conventional technologies, but is excited by the potential for opening up completely new areas of application.

The power to weight ratio, for instance, points Stevens toward medical uses in permanent implants such as pacemakers; temporary inserts such as endoscopes, and for all manner of low-intrusive keyhole surgery techniques.

The aerospace and automotive industries are already showing keen interest, because they always have weight and space restrictions.

Uses in explosive atmospheres could also prove a rich vein, as could operator safety critical applications and high accuracy positioning.

Being basically of unitary construction there is little chance of parts wearing out and consequent failure, so high reliability and long life applications are also target areas for Unimatic.

"Piezo produces linear motion directly, doing away with the need for a mechanical rotary to linear conversion mechanism, which in conventional systems is subject to wear, failure, inaccuracies and inefficiencies", observes Stevens.

"The only wear is likely to be on the soles of the piezo feet, so the developers have fitted them with little shoes".

"It's attention to detail like this that is allowing us to offer a viable technological alternative to engineers and developers striving to create the next generation of design in their own industries".