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A new variable stiffness actuator and its control method

Lei Zhang (Northwestern Polytechnical University, Xi’an, China)
Wendong Wang (Northwestern Polytechnical University, Xi’an, China)
Yikai Shi (Northwestern Polytechnical University, Xi’an, China)
Yang Chu (Northwestern Polytechnical University, Xi’an, China)
Xing Ming (Northwestern Polytechnical University, Xi’an, China)

Industrial Robot

ISSN: 0143-991x

Article publication date: 15 March 2019

Issue publication date: 5 August 2019



To achieve variable stiffness, this paper aims to design a flexible actuator with variable stiffness by using the magnetorheological effect of magnetorheological fluid. The variable stiffness actuator can well meet the safety requirements of human–robot interaction and be more adaptable to unknown or complex environments. The variable stiffness actuator designed in this study can realize the continuous and controllable change of stiffness compared with the existing actuator.


The principle of variable stiffness actuator is illustrated in detail; the three-dimensional model and mechanical model of the flexible actuator are provided. The magnetic field distribution of the actuator coil is analyzed, and the dynamic model of the actuator is provided.


Output torque test suggests that the magnetorheological fluid variable stiffness actuator (VSAMF) can output a stable torque which meets the designing requirements of the test; sinusoidal follow-up test shows that VSAMF can implement sinusoidal follow-up; variable stiffness test shows that VSAMF can achieve real-time variable stiffness adjustment; the crash test suggests that VSAMF can well protect machines when meeting obstacles.


In this paper, a new variable stiffness joint is proposed through changing the current to change the performance of the stiffness, and it can realize the continuous and controllable change of stiffness.



Zhang, L., Wang, W., Shi, Y., Chu, Y. and Ming, X. (2019), "A new variable stiffness actuator and its control method", Industrial Robot, Vol. 46 No. 4, pp. 553-560.



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