Actuators for high speed high accuracy co-ordinate measuring machines

Describes the Ferranti MIDAS co-ordinate measuring machine (CMM) which consists of three orthogonal axes in X, Y and Z and a Renishaw PH10 two degree of freedom probe capable of rotating ±180° about the probe axis and 0 to 105° perpendicular to the axis. The machine axes are controlled by independent servo loops consisting of a pulse width modulated current amplifier, three phase brushless servomotors with incremental shaft encoders, preamp component for signal conditioning and velocity loop control and a position controller implemented in software and downloaded to transputer. The position loop transducer is a fixed optical grating parallel to each axis of 50 lines/mm