Optimal Design of the Elastic Unit for the Serial Elastic Hip Joint of the Lower Extremity Exoskeleton

This paper presents an optimal design method of the Elastic Unit for the Serial Elastic Hip Joint of the Lower Extremity Exoskeleton. The elastic element is a compact torsional elastomer. The design of the elastomer should meet the changes of the torque and stiffness of the hip joint during the movement of the human lower limbs. The design process is realized in two steps. Firstly, determining a basic element for the topology that meets the design criteria. Secondly, iterating in the ANSYS Workbench and optimizing its parameters to minimize the Von Mises Stress (making it less than the yield limit of the material used). After the theoretical results being calculated in the ANSYS Workbench, the torsional deformation angle of the elastomer is obtained by applying the torque simulation with different gradients. Besides, the experimental data is recorded and imported into MATLAB, and the stiffness curve is fitted by the least square method to verify whether the stiffness and linearity meet the design requirements. Finally, the simulation results of torsional elastomer can be obtained that the torque is 50 Nm, flexible Angle is 3°.