Early Piezo-drive systems used 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 amaount 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. However, these systems only provide simple actuation or limited rotational speed and are unable to produce higher speeds or forces.
A new mechanism from Nanomotion, whose products are available in the UK from Micromech, imposes an X-Y bias on the Piezo element to produce an elliptical motion at the driving element tip. When excited at the 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. As the element tip range is in the region of 6um at maximum deflection, very slow and smooth motion can be obtained at much lower bias voltages.
Motor resolution is as low as 5nm and 300um per second. Moreover, the tip can be displaced from +/-10nm to +/-6um and then returned to its original position, using a dc mode from an AB5 amplifier. Motors provide forces from 0.4 to 3.0kg, but when coupled in tandem from one drive amplifer, they can produce linear motion at speeds in excess of 300mm/s and forces greater than 10kg.