Kinetostatics modeling and elasto-geometrical calibration of overconstrained parallel manipulators

Abstract

Overconstrained parallel manipulators have garnered increasing attention due to their higher stiffness resulting from redundant wrenches and improved performance by eliminating clearances and backlashes through forced assembly, as compared to non-overconstrained counterparts. However, a challenge arises in calibrating these manipulators due to non-ideal geometry, which introduces mechanical strains in the structure. Consequently, identifying the geometrical errors of the manipulators becomes difficult without considering the effect of elastic deformations. The primary contribution of this work is to propose an efficient kinetostatic modeling and elasto-geometrical calibration method that enables simultaneous identification of both geometric parameters and compliance parameters in overconstrained parallel manipulators. Initially, a kinetostatic model considering both geometric errors and flexible deformations is proposed using an error equivalent method. Subsequently, a unified error model encompassing geometric and compliance parameters is derived through projection operations. To validate the effectiveness of the proposed method, experiments are conducted on a 3-DOF translational manipulator. The results demonstrate a significant reduction in residual errors of the manipulator using the proposed approach.