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Design of a torsional compliant mechanism with given discrete torque-deflection points for nonlinear stiffness elastic actuator

Published online by Cambridge University Press:  17 May 2023

Wenjie Ju
Mechanical Engineering School, Tianjin University, Tianjin 300072, China
Bingwei Li
Mechanical Engineering School, Tianjin University, Tianjin 300072, China
Rongjie Kang
Mechanical Engineering School, Tianjin University, Tianjin 300072, China Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China
Songyuan Zhang
State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150001, China
Zhibin Song*
Mechanical Engineering School, Tianjin University, Tianjin 300072, China Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China
Corresponding author: Zhibin Song; Email:


Owing to inherent flexibility, compliant actuator with physical elastic elements can implement compliant interactions between robot and environment. Nonlinear stiffness elastic actuators (NSEAs) use one motor to adjust position and stiffness, which improve compactness of variable stiffness actuators, and consider high torque/force resolution and high bandwidth. The primary challenge of designing a NSEA is designing a reliable compliant mechanism with a given torque-deflection profile. In this study, a general design method of torsional compliant mechanism through given discrete torque-deflection points was proposed, where a chain algorithm based on 2R pseudo-rigid-body model was used to describe the large deformation in elastic elements. Moreover, the theoretical model of stiffness of a compliant mechanism based on series flexible beams was developed. Based on the proposed model, the dimensional parameters of proposed compliant mechanism were designed satisfying the condition of the given torque-deflection points. Finally, simulation and physical experiment of the designed compliant mechanism through three given torque-deflection points are conducted to show the effectiveness of the proposed method. The designed compliant mechanism was tested and evaluated in the self-developed NSEA.

Research Article
© The Author(s), 2023. Published by Cambridge University Press

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