Research On The Kinematic Design And Static Performance Analysis Of A Foot-Plate-Based Gait Trainer

Driven by the requirements of the innovation of lower-limb rehabilitation robots,this thesis proposes a new lower-limb rehabilitation robot with the support of the National Natural Science Foundation of China,focusing on its kinematic design,semi-analytical stiffness modeling and finite element analysis(FEA).The following works have been accomplished.To meet demands of lower-limb rehabilitation,a three degrees of freedom(DOF)foot-plate-based gait trainer is proposed.The topology and movement characteristics of the parallel mechanism involved are briefly analyzed.Then the forward and inverse kinematic analytical model of the parallel mechanism is derived utilizing vector-chain method,resulting in the analytic expression of forward/inverse kinematics.Drawing on screw theory,the generalized Jacobian is developed,based on which the kinematic optimization of the mechanism is investigated.With the aid of the analytical model of inverse kinematics,a method for searching the boundary of orientation reachable workspace(ORW)is presented by considering the restriction of the shrinkage ratio of the pneumatic artificial muscle(PAM).Based on the principle of virtual work and the method of substructure synthesis,a semi-analytical stiffness modeling approach is proposed by taking the elastic deformation of all branches and the rotatable holder into account.According to the mechanical structure and the static characteristic of each branch and the rotatable holder,the compliance matrix of each component and the stiffness matrix of the parallel mechanism are derived.By taking experimental study,the static performance of the PAM is investigated,leading to the expression of the component stiffness of the PAM.Consequently,the linear stiffness of the reference point and the angular stiffness of the platform at the initial pose are evaluated by semi-analytical stiffness modeling method,and the distribution of the stiffness in the ORW is obtained.With the aid of SAMCEF and the static and dynamic performance prediction software developed by Tianjin University,the FEA model of the parallel mechanism is established to achieve the static performance estimation of the mechanism as a whole.In this wary,the linear stiffness of the reference point and the angular stiffness of the platform within the ORW are evaluated and compared with those of the semi-analytical model in order to verify its effectiveness.The investigation carried out in this thesis is of great importance to enhance the kinematic and static performance of the foot-plate-based gait trainer.