Control strategy and experimental research of a cable-driven lower limb rehabilitation robot

Abstract

This paper aims to solve the problems of the existing limbs rehabilitation robots in terms of configuration limitations, human-machine compatibility, multimodal rehabilitation training. In addition, the control method of the cable tension of cable drive unit (CDU) loading system is studied to improve loading accuracy of cable tension and safety of the rehabilitation training robot. The novelty of this work is to propose a compound correction controller that can not only ensure the tracking accuracy of the cable-driven lower limb rehabilitation robot (CDLR) but also effectively improve the force loading accuracy of the cable tension force. Hence, this paper proposes a CDLR that can realize the active training mode, passive training mode, and assistive training mode. Firstly, the structure and working principle of CDLR is introduced. The dynamic model of the CDU loading system is established and the frequency characteristic of the CDU loading system is analyzed. In order to improve the loading accuracy and response speed of the CDU loading system, a compound correction controller is designed based on the frequency characteristics of the CDU loading system. Finally, the active force servo control experiment and the passive force servo control experiment of the CDU loading system are carried out on the experimental platform. The experimental results show that the compound correction control strategy can meet the requirements of lower limb rehabilitation training in the active force servo control experiment; the compound correction control strategy can significantly improve the loading precision and dynamic performance of the system in the passive force servo control experiment. That is, the compound correction control strategy can meet the requirements of lower limb rehabilitation training. The results provide a basis for the whole robot experiment and human-machine experiments and improve the stability of the CDLR system and patient safety.