Design, comprehensive evaluation, and experimental study of a cable-driven parallel robot for lower limb rehabilitation

The stability of the rehabilitation robot system is an important prerequisite for the safety of patients' rehabilitation training, and there are few studies on the evaluation method of the stability of the cable-driven rehabilitation robot. Hence, this paper aims to study the evaluation method of the dynamical stability of a cable-driven lower limb rehabilitation robot (CDLR) through comprehensive consideration of the position, cable tension, system stiffness, and velocity of the traction point. The structure and working principle of the CDLR is introduced. The position performance factor, the cable tension performance factor, and the system stiffness performance factor are defined based on the kinematics, dynamics, and system stiffness model of the CDLR. The evaluation index of the static stability of the CDLR is presented by comprehensively considering three performance factors. Considering the safety and comfort of the patients' training, a velocity influence function is given. Combined with the evaluation index of the static stability and the velocity influence function, the evaluation index of the dynamical stability of the CDLR is proposed. Finally, the stability distribution laws of the CDLR are presented by simulation and experimental study. The rationality and correctness of the stability evaluation index are verified by experiments. The experiment results provide an important reference for structural design, rehabilitation training task planning, and control strategy of the CDLR.