In order to improve the measurement accuracy of articulated arm coordinate-measuring machines (AACMMs), a new kind of AACMM based on an indexing joint structure is proposed in this paper. The working principle of the indexing joint is introduced, and a kinematic model of the measuring machine is established based on this principle. The influence weight of the angle error for each joint on the measurement accuracy is analyzed by simulations, and the changes in the accuracy, measurement space and flexibility of the measuring machine before and after adopting the indexing joint are compared. The results show that the use of the indexing joint can effectively improve the measurement accuracy of the AACMM, and the replacement of the first two joints with the indexing joints has the most obvious improvement effect on the measurement accuracy, and has little influence on the measurement space and flexibility. The indexing joint-based AACMM can provide a new idea for the research of improving the measuring accuracy of the AACMM.

Kinematic calibration is an effective way to improve the accuracy of articulated arm coordinate measuring machine (AACMM). In this paper, a multi-point calibration method for AACMM based on observation index is proposed. First, the kinematic model is established according to the D-H method, and the measurement error model is established on the basis of the D-H model. Then, the feasibility of using the observation index to evaluate the posture of AACMM is analyzed, and simulations are carried out to verify the correlation between the level of the observation index and the quality of the calibration results. In the simulation, the influence of the number of measurement positions and the number of measurement points on the calibration results are studied in combination with the observability index, and on this basis, a multi-point calibration method is proposed. Finally, experiments are carried out to verify the superiority of the multi-point calibration method. The results show that, compared with the single point calibration method, the multi-point calibration method can improve the measurement accuracy by 31.58%, and the average measurement error of the AACMM after the multi-point calibration method is 0.0091 mm.