Joint module angle error analysis and modelling of self-driven articulated arm coordinate measuring machine

The self-driven articulated arm coordinate measuring machine (self-driven AACMM) is a new type of flexible coordinate measuring equipment. The integrated joint module is introduced to the AACMM joint for self-driven control and automatic measurement, resulting in the joint angle error of self-driven AACMM. In this study, an ideal measurement model of the self-driven AACMM have been established. The sources of angle error of joint module is analysed, and single and comprehensive models of the joint module’s angle error are established. Numerical simulation of the angle error model of the single joint module is conducted by MATLAB. An angle error calibration experiment of the joint module is carried out with the photoelectric autocollimator and the metal 36-sided prism. Results show that each joint module produces different torsional deformation due to load. The angle error of joint module 1, 6 are most and least affected by the load torque, the actual average errors of the two are 37.64 arcsec and −0.9632 arcsec, respectively. The simulated and calibrated single-joint module angle error trends are cyclical, and the calibrated angle error range is [−100.4 arcsec, 205.2 arcsec]. The harmonic error component in the harmonic reducer and the magnetic encoder is an important factor of the angle error of joint module. The eatablished angle error model of single joint module can be effiectively applied to comprehensive error compensation for high measurement accuracy of self-driven AACMM.