Prediction of Touch-Trigger Probing Error Profiles by a Six-Axis Robot

There is a growing need for “in-line measurement” of geometric accuracy of the manufactured parts in the manufacturing line. An industrial robot with a touch-trigger probe installed to its end effector can be potentially applied to such an inline measurement as a portable coordinate measuring machine (CMM). However, the absolute positioning accuracy of robots is often very poor compared to the conventional CMMs. This paper presents that the accuracy of robotic touch-trigger probing can be improved by using the kinematic model containing the angular positioning error of each rotary axis as error sources. The measurement accuracy of robotic touch-trigger probing is experimentally investigated in the straightness measurement of a pre-calibrated artefact, placed at various positions within the workspace of the robot. Significant influence of the rotary axis angular positioning errors on the straightness measurement by robotic probing is revealed.