Structural design and performance analysis of a self-driven articulated arm coordinate measuring machine

Abstract

To solve the problem that the traditional articulated arm coordinate measuring machine cannot measure automatically, a self-driven articulated arm coordinate measuring machine (AACMM) is proposed. The length of the connecting rods of the AACMM was allocated according to the design indicators. The AACMM virtual prototype was assembled based on the joint module selection and joint component design, and its measurement space range was also verified. The AACMM ideal measurement model was established based on MDH methodology. The static deformation of the structure and the influence of the dynamic flexible deformation on the positioning error of the probe of the measuring machine was analyzed, respectively. The results show that the measurement space range of the AACMM designed in this paper can meet the design index of the measuring radius. The probe position error caused by static deformation of the measuring machine after structural optimization was reduced by an order of magnitude. The positioning error of the probe caused by the dynamic deformation of the AACMM structure meets the positioning accuracy index. In the constant-speed touch measurement stage, the instantaneous position error of the probe changes linearly with time, and the optimal touch speed (6.6 mm/s, 6.4 mm/s) exists to minimize the probe positioning error. During the variable-speed approach stage, the influence of angular acceleration and velocity of each joint on the positioning error of the probe can be negligible when AACMM in the typical posture. In the extreme posture, , the inertial force of the measuring machine structure and the instantaneous position error of the probe are the smallest with the optimal joint angular acceleration ( ) and angular velocity ( ). The structural design and positioning error performance analysis of self-driving AACMM can provide a theoretical research foundation for subsequent trajectory planning and error compensation modeling.

Dynamic error modeling and analysis of articulated arm coordinate measuring machine with integrated joint module

“…During the previous work of the mechanical structural design, it was demonstrated through a simulation that the maximum position deviation occurred in the probe [7] because of the static bending deformation of the articulated arm linkage of the self-driven AACMM. Therefore, the instantaneous spatial attitude of the articulated arm linkage axis should be solved first to improve the dynamic positioning and measurement accuracy of the self-driven AACMM.…”

“…When the integrated joint module rotates at different velocities and accelerations, the dynamic flexible deformation of the measuring machine structure will be transient, thus affecting the smoothness of the measuring machine in automatic control and measurement. The authors have already studied the simulation distribution of the effect of motion parameters on the positioning measurement error of the measuring machine [7], and determined the optimal motion parameters to achieve the best motion smoothness and the least measurement error of the self-driven AACM. Thus, this paper mainly focuses on the numerical simulation based on the Monte Carlo simulation principle [35] to analyze the effect of structural parameters on the dynamic positioning and measurement errors of the self-driven AACMM.…”

“…The authors' group will study the second and third generation prototype to further improve the length measurement accuracy of the measuring machine in the subsequent research. Considering the influence of motion parameters [7], the optimal motion parameters should be determined through calibration first in this paper, and then the workpiece measurement experiments is carried out based on the first-generation measuring machine prototype to verify the effectiveness of the dynamic error model for the compensation of the measurement error.…”

“…In this case, the AACMM cannot meet the demand of online automatic measurement of precision instruments for intelligent manufacturing. To address this issue, the authors in their previous work proposed a self-driven AACMM [7] to achieve self-driven control and automatic measurement with integrated joint modules introduced to its rotary joints.…”

A variable-measurement-space-based method for improving the measurement accuracy of AACMMs

“…The AACMM calibration is achieved by rotating the platform, which greatly simplifies the calibration process. Apart from the novel artifacts, many methods have also been proposed to improve the measurement accuracy and achieve the automatic measurement for AACMMs, such as machine learning method [17,18], self-driven joints [19,20], the combination between laser tracking instruments and industrial robots [21].…”