Error modeling for sensitivity analysis and calibration of the tri-pyramid parallel robot

Abstract

Developments in machine tooling technology are driven by a demand for high-precision machining of various materials. However, high-precision machining using a kinematic model with nominal values is associated with inaccuracy as the machine errors are not accounted for. Therefore, it is important to precisely determine the machine error factors to produce an accurate error model. Complex models that use iterative calculation in the calibration process are time-consuming and resource-intensive. In this paper, a simplified error model was applied to a translational parallel tri-pyramid robot with three degrees of freedom (DOF). The sources of kinematic error were joint errors, kinematic parameter errors, and actuator control errors; 90 errors were identified in total. The full error model was defined using a linearized homogeneous transformation matrix (HTM) and the Denevit–Hartenberg (DH) parameters. The 27 dominant error sources affecting the accuracy of the platform position were selected by a sensitivity analysis method. After the error reduction model based on these sources was established, the calibration was performed by simulation. The calibration simulation results suggest that the model accuracy could be improved from 0.85 to 0.26 mm.