Measurement of three degrees of freedom error motions of rotary axis based on auto-collimation principle

Abstract

Due to the components of DD motor exist errors in the process of machining and assembly, which will generate error motions in rotary axis when the DD motor starts running. To solve the above problems, this paper presents a measurement method for three degrees of freedom error motions of rotary axis based on auto-collimation principle. The proposed system consists of two collimated laser, two beam splitters, two quadrant photodiode detectors (QPDs), four lenses and a high precision steel ball mounted on the top of DD motor. The error motions of the rotary axis result in the changes of the position of high precision steel ball. Thus, the shift values of laser beams reflected from the high precision steel ball are detected by the QPDs. The experimental results show that the radial and axial error motions of DD motors is less than 3.2μm and range from -1.5μm to 2μm respectively