A novel variable stiffness actuator with a rotary magnetorheological damper

A novel rotary variable stiffness actuator (VSA) is presented to meet the requirements of the variable stiffness drive for a robot joint. Considering the characteristics of a rotary magnetorheological damper (MRD) that has controllable torque and fast response, a servo motor and a rotary MRD are combined to form a VSA. The principle of variable stiffness drive is analyzed according to the frame of the VSA. The rotary MRD for the VSA is designed, and the electromagnetic field distribution in the damper is analyzed with the finite element method. Then, the torque and magnetomotive force value of the damper are calculated. Based on the configuration of the VSA and the mechanical characteristics of the damper, the variable stiffness control method is proposed. Based on these factors, the rotary MRD and the VSA are developed, and the performance tests are worked out. The experimental results show that the test results of the damper torque are close to the calculation results, and different stiffness coefficients can be set in the control program of the VSA. The test results of the stiffness coefficients are close to the set values. Moreover, the approach proposed in this article provides valuable insights into the utilization of rotary MRD for the development of variable stiffness robotic systems.