Error sources in touch-trigger probing by a planar robot arm

The accuracy of touch-trigger probing by a robotic manipulator is determined by the accuracy of the robot forward kinematic model to estimate the stylus sphere position from angular positions of rotary axes. While many past works employ a robot kinematic model only containing the Denavit-Hartenberg (DH) errors as error sources, this paper presents the application of a novel model, containing the angular positioning and radial error motions of all the rotary axes, to the robotic probing. In the probing of a straightedge, the experiments show that a large portion of a higher frequency component in the probed profiles is attributable to the angular positioning error motion of rotary axes. On the other hand, a lower frequency “waviness” component is attributable more to the DH errors. As a fundamental study, this paper targets the probing by a planar robot arm, as it has a simpler kinematics, with significantly less error parameters, than a six-axis robot. • Accuracy of robotic probing is determined by accuracy of robot kinematic model. • A novel model containing rotary axis angular positioning error motions is applied. • Contributions of individual error sources are experimentally studied. • Experiments show significant influence of angular positioning error motions.