A general and novel approach for parameter identification of 6-DOF parallel kinematic machines

This paper presents an external calibration based approach that enables the geometric parameter errors of 6-DOF parallel kinematic machines (PKM) to be identified using a minimum set of pose error measurements. By taking full advantage of the intrinsic properties of PKM systems, it has been shown that with an endpoint sensor and a dial indicator, the full set of parameter errors can be identified by measuring only (1) the “flatness” of a fictitious plane generated by the tip of the endpoint sensor, (2) the “straightness” and “squareness” of two orthogonal axes, and (3) the orientation error of the end-effector at the initial configuration. Consequently, the burden due to the orientation error measurement of the end-effector can be dramatically reduced. Simulation results of a Stewart platform are given to illustrate the validity and effectiveness of this approach. The proposed method is so general that it can also be used to handle the parameter identification problems of PKM systems with fewer than six degrees of freedom.