Design And Performance Research Of(2-SPU-PU)&R Hybrid Ankle Joint Rehabilitation Mechanism

Ankle joint is a weight-bearing joint of human body,which is easy to be damaged due to its participation in sports.It is extremely vulnerable to injury,and postoperative rehabilitation training is of vital importance.However,the ankle rehabilitation equipment is not enough degrees of freedom and its function is not perfect.In view of the existing problems of ankle rehabilitation,this paper proposes a hybrid ankle rehabilitation mechanism,which can not only realize the rotational movements of ankle joint,but also realize the stretching movement of ankle joint.Firstly,according to the structure,movement mechanism and rehabilitation form of the ankle joint,a 4-DOF ankle joint rehabilitation mechanism with(2-SPU-PU)&R configuration is designed.The hybrid mechanism is composed of a 2-SPU-PU parallel mechanism and a rotational pair R in series.The hybrid mechanism can realize ankle joint single movement,including plantar flexion and dorsiflexion,adduction and abduction,inversion and eversion and stretching,as well as combined motion of multiple forms can be generated.The rehabilitation mechanism is a hybrid mechanism,and the 2-SPU-PU parallel mechanism is taken as the key research object.According to the advantages and disadvantages of driving pattern and the selection principle of driving pair,the driving pairs of(2-SPU-PU)&R hybrid ankle joint rehabilitation mechanism are selected.Secondly,the closed-loop vector method is applied to analyze the inverse position of the 2-SPU-PU parallel mechanism,and an example is given.Based on the inverse equation,the velocity variation and the Jacobian matrix of the 2-SPU-PU parallel mechanism are obtained.According to the the inverse solution,the driving function is set and the SolidWorks software is applied to analyze the workspace of the 2-SPU-PU parallel mechanism by adopting the method of the combination of dynamic and static driving.The factors affecting the workspace are analyzed,and the workspace of the 2-SPU-PU parallel mechanism is solved according to the inverse solution equation using Matlab software.The correctness of the inverse solution equation is verified by the comparative analysis of the workspaces.Thirdly,the model esrtablished in SolidWorks is imported into ADAMS.According to the output trajectory of the moving platform,the inverse kinematics of the 2-SPU-PU parallel mechanism is simulated.The(2-SPU-PU)&R hybrid ankle rehabilitation mechanism is simulated.The simulation results show that the rehabilitation mechanism can reach the rehabilitation movement range of ankle joint and perform compound motion.Finally,Newton-Euler equation is used to solve the driving forces of the limb of the 2-SPU-PU parallel mechanism,and inverse dynamics is simulated.The model of human-machine system is established and simulation of inverse dynamics is carried out using Anybody software.The maximum muscle activity under different rehabilitation states is less than 1 by simulation of inverse dynamics,which does not exceed the maximum strength of the ankle muscle and can increase the strength of the muscle group.The rehabilitation effect of the(2-SPU-PU)&R hybrid ankle rehabilitation mechanism is verified.