3-D Passive Scale Tracking Method for Measuring Motion Errors of Industrial Robots

Abstract

This work presents the development of a 3-D passive scale tracker (3DPST) for industrial robot pose accuracy detection. A nonlinear optimization error parameter identification approach based on a geometric error model is given in order to acquire geometric errors of the instrument precisely and simply. The spatial measurement accuracy of 3DPST has greatly increased after new error parameters adjustment. Additionally, the robot pose errors are measured by 3DPST, and a laser tracker (LT) is employed as a reference tool for simultaneous comparison and verification. Moreover, as a result of the presence of Abbe offsets between the measurement points of the two instruments, orientation errors will affect positioning errors in the comparison procedure. Therefore, it is crucial to apply the Abbe principle while transferring the error values from the LT measurement points to the 3DPST measurement points. According to ISO 9283, the pose accuracy is measured using a cube in the robot workspace. The maximum measurement difference of positioning errors and orientation errors between the two instruments is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 33.1 \mu \text{m}$ </tex-math></inline-formula> and 0.0723°, respectively. This demonstrates that the two instruments’ calibration capabilities are comparable, and 3DPST can complete the pose accuracy calibration of industrial robots.