DIRECT VOLUMETRIC ERROR EVALUATION FOR MULTIAXIS MACHINES

A generalized methodology, referred to as direct error analysis, for t he evaluation of the position and orientation errors in the workspace of a multi-axis machine of arbitrary configuration was formulated base d on two important new concepts. First, a modified coordinate frame as signment rule was defined. This rule offers the ability to assign the origins of the joint frames at the physical joint so that the correspo nding homogeneous transformation matrices can overcome the problem wit h the conventional Denavit-Hartenberg rule with respect to small varia tions in link geometry. Second, the concepts of fixed and moving error reference frames for kinematic error motions were introduced. Dependi ng on the joint configuration these frames facilitate the representati on of the true kinematic error motions at both ends of the physical li nk.