On the role the friction plays in an ultra precision positioning system

Friction, due to its destabilizing and drastic magnitude variation between stick and slip, is commonly considered as a detrimental factor to a positioning system. This paper, based on the new knowledge about pre-sliding dynamics, tries to put forward another point of view; it shows that the spring-damper-like property in the pre-sliding phase makes it possible to achieve the so called Precision Limit Position (PLP). With this kind of positioning, the position error and amount of in-position vibration of the system can remain to be equal to the resolution of the position sensor used in the feedback loop. This is, of course, the limit of the precision that a practical positioning system can achieve.