A New Study on the Relative Kinematic Accuracy Reliability of a Novel Exoskeleton with Series-Parallel Topology

An excellent exoskeleton worn by the operator might be able to move with a high degree of accuracy and repeatability. Based on the previous kinematic accuracy reliability model, this article proposes two new definitions of the relative kinematic accuracy reliability to investigate the motion accuracy ability of a novel exoskeleton with series-parallel topology thoroughly. According to the new definitions, the calculating results show that x-, y-, and z-directions of the exoskeleton end-effector have different motion accuracy abilities, the motion accuracy ability of x is the best of all, and the motion accuracy ability of y is better than that of z. To study error sources, we illustrated the geometric tolerances and driving errors, which cause the uncertainties of the exoskeleton end-effector. The effects of geometric tolerances and driving errors on kinematic accuracy reliability and relative kinematic accuracy reliability, which are the sensitivity analyses, were numerically simulated and elucidated. The results reveal that the error sensitivity in the x-direction is the lowest and the error sensitivity in the y-direction is lower than that in the z-direction. Besides this, the effects of driving errors on the motion ability of all directions of the exoskeleton end-effector are larger than those of geometric tolerances. This approach for modeling and calculating kinematic accuracy reliability, relative kinematic accuracy reliability, and their sensitivity analysis provides a novel and unique reference standard for exoskeleton and other mechanism design.