| Based on the study of the physiological structure of human ankle joint,the current demand for ankle rehabilitation and the relevant national policies guidance,this paper proposes a new type of parallel spatial mechanism for ankle rehabilitation,and studies its motion performance and motion paths.Firstly,based on the relevant medical knowledge,the analysis of the composition structure,motion modes and range of motion of the ankle joint have been carried out,and an active 3-RPS/R parallel mechanism with 4 DOF and practical structure has been proposed.By the modified K-G formula and the screw theory,the consistency between the mechanism and the motion modes of the ankle joint has been verified,which indicated the feasibility of mechanism design,then the virtual prototype model has been established.Secondly,the mathematical model of the parallel ankle rehabilitation mechanism has been established and kinematic analysis has been carried out.The inverse and positive solutions of the moving platform position of the mechanism have been solved for comparative verification.According to the closed-loop vector method,the variation laws of displacement,velocity and acceleration of the moving pair in each kinematic branch with time have been solved,and the travels of the moving pairs have been calculated.The result shows that the mechanism is easy to control.Thirdly,the numerical discrete search method has been used to draw the workspace of the m echanism moving platform in MATLAB,indicating that the scope of the workspace can meet the requirements of ankle rehabilitation.The maneuverability of the mechanism has been calculated by velocity Jacobian matrix,and the results show that the mechanism has good motion performance,no singularity and far away from the singularity region,which verify the operability of mechanism movement.Finally,use ADAMS to study the kinematics simulation and trajectory planning of the three-dimensional model,and select the characteristic points of the moving platform to display the movement path.By comparing the displacement,velocity and acceleration curves of the moving platform under S-type,T-type and modified T-type motion laws of inversion/eversion and stretching,it is concluded that the modified T-type motion law is more reasonable and can better meet the rehabilitation needs of patients.In this paper,the feasibility and rationality of 3-RPS/R parallel ankle rehabilitation mechanism are proposed and verified by theoretical analysis and simulations,which provides a new solution for ankle rehabilitation and has good theoretical significance and application value. |
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