Two-Stage Actuation Control System for CNC Contouring Systems

A CNC contouring system in which each axis is driven by a two-stage actuation system, where the first stage is a DC servo drive and the second one is piezoelectric microactuator, is discussed. In this system, the contour error, caused by the first stage due to dynamic response diferences between the axes, is decomposed to components which are used as position references for the second stage of each axis. With this arrangement the required travel of the second stage is kept within the travel range of the microactuator. Additional velocity feed-forward loop was added to the first stage which substantially reduces the contour error and thus the travel range requirement from the microactuator. Simulation studies show that the proposed controller has superior performance compared with current control schemes.