This motor’s made for walking

A small Swedish company has utilised piezoelectricity to drive what it claims is the world’s smallest, most precise linear motor that works on an entirely new principle borrowed from nature.

Machined from a single, solid piece, the ant-sized electric motor, called Piezo Legs, has dispensed with the rotor, stator, coils, bearings and electromagnets of conventional motors.

Instead, pairs of legs made from a crystalline ceramic material and directly driven by piezoelectric motion ‘walk’ backwards and forwards to create linear motion.

Developed by Uppsala-based Piezo motor, the motor has pairs of elements arranged like the legs of an ant. By switching the power supply from one side of the pair to the other a walking-like action can be simulated, and careful timing between the different walking pairs ensures that there is sufficient contact with the ground for stability.

In use the motor is turned over on to its back and fixed into position. A rod is then rested on top of the legs, which when activated, will move back and forth.

Per Oskar Lithell, chief executive of Piezo motor, claimed that it overcomes many of the traditional problems of linear motors in small precision applications.

Traditionally, a linear motor uses a screwing mechanism to transfer a rotating motion into a linear one. This requires gears and clutches and takes up space.

The advantage of Piezo Legs is that it operates without any mechanical transmission elements and is therefore far less prone to wear and tear

The motor’s exceptionally accuracy is due to the fact that the size of the steps the motor takes – typically no bigger than a couple of micrometers – can be controlled in the nanometer range.

An impressive turn of speed is another of Piezo Legs’ characteristics. At its lowest setting, a drive rod can apparently take an hour to move 0.7mm (motion that is invisible to the naked eye) while at its fastest, and taking up to 10,000 steps per second, the rod will move at 20mm/s with a force of 8N.

Available in the UK from London-based engineering company Unimatic, the motor is likely to end up in a variety of precision industries. Ericsson has tested the technology on industrial splicing units – small robotic devices that splice fibreoptic cables together, and the motor is currently being looked at by a number of US and Swedish multinationals.

Because applications are in specialised, precision areas, and thanks partly to the ease with which the device can be manufactured, Piezo motor said that it plans to build tailormade motors rather than off the shelf products.