A - It's important to understand the requirements of a motion control application in order to properly specify a system. The best way to describe the positioning capabilities and requirements of a system is to specify the resolution, repeatability, and accuracy. System resolution is typically determined by the resolution of the motor or actuator.
Piezoelectric actuators provide nanometer resolution.
Repeatability is the ability of a positioning system to start at one position, move away, and return to that position. 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.