Design and Research of Flexible Joint with Variable Stiffness Based on Torsion Spring

In order to improve the dynamic characteristics of the robot, a flexible joint mechanism based on torsion spring is designed, featuring active and passive stiffness adjustment based on torsion spring. Taking the change of the size of the torsion spring as the mechanism, the stiffness of the rotary joint of the robot can be adjusted through the compact design. The flexible joint adopts the central symmetric design and produces the axial force to squeeze the disc spring. Moreover, it is converted into radial force through the steel ball and the cone disk, which prevents the inner diameter of the torsion spring from changing and realizes the active-passive control of the stiffness. On this basis, the mechanical model of the variable stiffness joint is established. The variable stiffness curve is calculated by MATLAB and verified by ABAQUS. The results show that the stiffness of the robot joint can be changed by changing the structural parameters during the torsion process, and the designed mechanism meets the requirements of variable stiffness of robot joints