Kinematic calibration of a 6-DOF parallel manipulator based on identifiable parameters separation (IPS)

This paper presents a new calibration method for a 6 degree-of-freedom (DOF) parallel manipulator based on identifiable parameters separation (IPS). This method begins with the parameters separation by the principle of IPS, and then identifies the subsets of the parameters sequentially and respectively. The method aims to identify as many parameters as possible just by simple and direct measuring procedures, which can lower the number of parameters in the complex identification model and thus reduce the coupling effect and uncertainty during identification. Moreover, the reduction of the parameters will allow fewer measurements and faster convergence for the identification algorithm. Firstly, the manipulator is briefly described and its geometric errors are studied. Secondly, the concept of IPS is introduced and the principle of IPS is summarized. Then, according to the proposed method, the corresponding calibration experiment is designed. Lastly, the experiment of this manipulator is conducted and the result shows the validity of the method for accuracy improvement. The rules of IPS and the simplification of complex identification enable the use of this method on other types of parallel mechanisms.