The invention discloses a method for detecting
radial motion error of a high-speed principal axis by adopting a multi-circle superposition three-
point method. Three
laser displacement sensors are distributed around the high-speed principal axis which is provided with an angle
encoder that has N lines and is connected with a scaling circuit; when the scaling circuit counts for Z times in an accumulating way and Z can not be divided exactly by N, the scaling circuit outputs sampled signals, and a trigger sensor implements sampling once; by repeating in this way, the principal axis is evenly distributed with n points for sampling by rotating the principal axis for a plurality of times to complete a sampling period; after every time of sampling, the sampling value is transmitted to an industrial computer through a
USB interface and is then recorded; according to the requirements of detection accuracy, the sampling work having a plurality of sampling periods is carried out, the average sampling value of n points of every
laser displacement sensor is calculated, and the deviation from circular form, the eccentric error and radial turning error of the principal axis which are obtained by separation are calculated. The method is not sensitive to the performance of the
laser displacement sensor and is suitable for detecting
radial motion error of the high-speed principal axis.