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Ceramic servo motors compared with piezo types

Edited by the Manufacturingtalk editorial team Feb 14, 2005

Use of piezo technology in motion and positioning control solutions is not new but the technique employed in these ceramic servo motors is said to be innovative and original.

The employment of piezo technology in motion and positioning control solutions is not new but the technique employed in Nanomotion's ceramic servo motors is innovative and original.

Many earlier piezo-drive systems use a number of piezo elements arranged in line to step the positioning stage along, by passing the holding force from one to the other sequentially.

Other 'Flexure' types of stage move the load by the amount the element expands when biased by a voltage gradient.

Some fine rotary lead-screw stages employ a 'tuning- fork' style operation that causes rotation in a specific direction when a saw-tooth wave form is applied to the piezo element.

In other words they can act only as a simple actuator or provide limited rotational speed but none of the above systems are able to effect high speed or forces.

The Nanomotion patented mechanism utilises a novel X-Y bias on the piezo element to produce an elliptical motion at the driving element tip.

When excited at a carrier frequency of 40kHz with a varying potential, the major axis of the ellipse can be modulated to drive a linear surface at variable speeds using an almost standard servo speed control interface of +/-10V DC.

As the element tip range is around 6 microns at maximum deflection it is evident that exceedingly slow and smooth motion can be obtained at much lower voltages of bias.

The motor resolutions go down as low as 5nm and 300 microns per second.

Using a DC mode from the AB 5 Amplifier, amazingly the tip can be displaced from +/- 10nm, to +/- 6 microns and then returned to the original position.

The motors are available from 0.4 to 3.0kgf force when coupled in tandem from one drive amplifier can produce linear motion at speeds greater than 300mm per sec with forces in excess of 10kgf.

This makes the motors extremely powerful for fine focussing and stage positioning.

They are now being extensively applied to exacting processes by companies in the semiconductor, communications and pharmaceutical industries, the drive mechanism also lends itself ideally to peripherally driven rotary stages as used in telescopes and precision rotary tables.