Analysis of dynamical stability of rigid-flexible hybrid-driven lower limb rehabilitation robot

The research of the safety problem of the cable-driven lower limb rehabilitation robots (CDLR) is not considered in the related report. Hence, the purpose of this paper is to study the dynamical stability evaluation method of a rigid-flexible hybrid-driven lower limb rehabilitation robot system (RFHDLR) to meet the training requirements of different patients in different rehabilitation stages. In order to improve the flexibility and operational performance of the robot system, one rigid motion chain is introduced into the cable-driven parallel robot (CDPR) to form a RFHDLR. Secondly, the motion planning strategy of the rigid motion chain is analyzed. Then, based on the kinematics and dynamics of the robot system, the cable tension performance factor and the system stiffness performance factor of the robot system are defined, and the static stability evaluation method and index of RFHDLR are obtained by the weighting method. Considering the patient's ability to withstand the motion velocity and the effect of the volatility of slide motion velocity of the rigid motion chain on the safety of the robot system, the velocity performance factor of the robot system is proposed. The dynamical stability evaluation method and index of RFHDLR are discussed based on the static stability evaluation method and the velocity influence function. Finally, for the two planning strategies of the rigid motion chain, the experimental study of the planned training trajectory of the lower limb traction point is performed based on simulation analysis. The experimental results verify the correctness of the stability evaluation method and provide a reference for further studying the training task planning and the control strategy.