## A motor with no revolving parts?

Illustration of a piezo-ceramic motor in action

It is not often that one sees something truly revolutionary. But last week I discovered a motor which had no revolving components and my jaw dropped open.

Periodically at NPL we have ‘supplier fairs’, a chance for NPL’s preferred suppliers to tell us about their new products. I went down last Wednesday with one thing on mind – free pens – but quickly got distracted. I spoke to a supplier (Heasons) who make linear translation stages. These are clever devices which move a carriage  along a track and position it precisely in one place or another. I have used these devices before and it is really satisfying to write software that controls the motion of carriage  and makes it move to a particular position within a hundredth of a millimetre or so of a target position – often at every high speeds. I was familiar with these products so – after acquiring free pen – I asked the salesman if there was anything new…

He showed me a small carriage moving backwards and forwards under control along a track – and then he told me that the motor driving this had no revolving parts. Like you, my first thought was: ‘How can a motor have no revolving parts?’ The answer is that it has vibrating parts – you have to look at the movie to understand – and even then it’s surprising. Basically, a piece of piezo crystal is made to ‘wiggle’. It has a piece of hard ceramic glued to it which butts up against a bearing surface on the object that needs to be moved.

When no power is applied to the crystal it simply acts like a brake, pressing against the bearing surface. But as the piezo is made to wiggle in a circular pattern, it drags the bearing surface of the carriage with it, moving around 300 nanometres for each wiggle.  Now that’s not much, but if the piezo wiggles 40,000 times a second, that amounts to 12 millimetres per second, which is a perfectly respectable speed. The motor shows no backlash, and can be positioned to much better than a single wiggle – to within a hundred nanometres or so of a target position.

This is the first piece of piezo-technology that I have seen which looks to me like ‘the future’. It is lighter, better, and cheaper to manufacture than conventional motors. And it can be miniaturised to a ridiculous extent: the salesman took great pleasure in showing me the second smallest motor they sold which looked like piece of straw! I am sure that I have seen the future!

WARNING! pun approaching….

This is a device which is revolutionary by virtue of the absence of  revolutionary parts.

SORRY 😉

### 3 Responses to “A motor with no revolving parts?”

1. Nestor Says:

I’m sure I remember being told that powered camera zoom lenses (and possibly autofocus mechanisms) work on the same principle. Albeit on a larger scale.

2. protonsforbreakfast Says:

Absolutely correct.

3. Peter Says:

Like this… gripping and releasing…
http://en.wikipedia.org/wiki/Piezoelectric_motor
Cool stuff