Design And Simulation Of A Parallel Mechanism For Lower-limb Rehabilitation Based On Biomechanical Analysis

To meet the demands of the development of lower-limb rehabilitation robots and supported by National Natural Science Foundation of China,a new rehabilitation method utilizing the training of main power muscles instead of the simulation of gait trajectory,is proposed in this thesis.Based on the biomechanical simulation,the rehabilitation trajectory planning,kinematic analysis,control and motion simulation of a foot-plated-based three degrees of freedom(DOF)parallel mechanism for lower-limb rehabilitation are systematically investigated.The following works have been accomplished.(1)Based on the biomechanical simulation analysis of lower-limb movements and the basic function of muscles during walking,the main power muscles are determined.Consequently,a new training method utilizing the training of main power muscles instead of the simulation of gait trajectory is proposed,which significantly reduces the complexity of the mechanism designed for lower-limb rehabilitation.The motion type/number and the movement ranges of the moving platform of the foot-plated-based mechanism are obtained.(2)Based on the parabolic transition domain of the linear trajectory,the investigation on trajectory planning of motions of the moving platform is carried out.By taking human anatomy and biomechanical simulation experiments,the combined motion of different degrees of freedom of the platform is achieved,and a compound rehabilitation trajectory substituting for human walking trajectory is determined.Furthermore,an index for evaluating the effectiveness of rehabilitation training is proposed.It has been proved that the strengths and activities of the main power muscles meet the requirements of rehabilitation training intensity.(3)According to the compound rehabilitation trajectory and the requirements for the design of lower-limb rehabilitation mechanisms,a redundant actuated parallel mechanism having two rotational and one translational(2R1T)moving capability is proposed for the development of a lower-limb rehabilitation device.Given the composite rehabilitation trajectory,the numerical simulation of the inverse kinematics of the proposed mechanism is investigated,which lays the foundation for the study of virtual prototype simulation.Moreover,a simulation model of the control system is proposed and the effectiveness of the control method is verified by an example.(4)Based on the analysis of static characteristics of pneumatic muscles,the nonlinear springs are adopted to replace the pneumatic muscles in the virtual prototype simulation by utilizing the experimental results of pneumatic muscles tension and contraction ratio.The simulation results show the motion of the parallel mechanism is stable while the platform tracking the proposed compound rehabilitation trajectory.Hence,the rationality of the design scheme presented is verified.Furthermore,the variation of each pneumatic muscle is obtained with the aid of the proposed control scheme,which proves that the specification of the pneumatic muscle meets the requirement of working pressure.