Electronics and medical applications that involve focusing, scanning, adjustment, and inspection often use sub-micrometer positioning. Piezo motors are usually used here because they move precisely, even down to a few nanometers. For example, in a measuring application, piezo motors might power a linear actuator that slowly carries small objects past a sensor recording geometric data.
However, piezo actuators have limited feed length and cannot transport significant payload. In addition, these motors can take a long time to move parts into and out of a target “active measuring” area — because most are actually slowed down by the very multi-stage, wide-stepped, play-free reduction gearing that maintains the high resolution of their low-speed moves in the first place.
Another way to power positioners is to use two drives: A piezo rotary motor plus a faster dc motor — both mounted on a common spindle. In this design, the dc drive gets the mechanism to target quickly (with its good feed rate) while the piezo motor delivers high motion resolution once it reaches that target.