Kinematic Calibration of the Central Linkage of a Wire-Actuated Parallel Robot: A Comparison Between Two Nonlinear Approaches

In this article kinematic calibration of the central linkage of a wire-actuated parallel robot, which has a parallelogram mechanism in its structure, is discussed. It is shown that the dependency between the parallelogram joint angles affect the conditioning of the identification Jacobian matrix. Through a sensitivity analysis, it is presented that some of the parallelogram link lengths are not identifiable. Two nonlinear calibration approaches, Gauss-Newton and Levenberg-Marquardt, have also been explained and their difference especially when the identification Jacobian matrix is ill-conditioned, are pointed out.