The motion of PZT actuators is not highly repeatable. Thus, if you need repeatable positioning, a separate position encoder or sensor is required. Accuracy is the ability of a positioning system to move to a particular position relative to an absolute standard. The accuracy of a positioning system is typically 10 to 20 times greater than the repeatability. Absolute position accuracy is typically needed for the most demanding metrology applications and requires that thermal drift, structural resonances, mechanical deflection, Abbe errors, and bearing errors be minimized.
Piezoelectric actuators are ideal for high-accuracy positioning systems.