Vibration control of a coordinate measuring machine

A comparative study of two vibration reduction schemes, the command preshaping technique and the feedforward control technique, is presented. The objective is to drive the end-point of a coordinate measuring machine along a commanded trajectory without any oscillations at the end-point. This is achieved by designing appropriate controllers for the system based on a robust control scheme. This scheme consists of two nested feedback loops-an inner loop to control the motor position and an outer loop to control the position of the end-point. The controllers based on the two vibration reduction schemes are designed for the outer loop to make the system vibration-free. It is shown that the command preshaping scheme is a special case of the feedforward control scheme. The design method is illustrated with a numerical example