The variable stiffness joint is a kind of flexible actuator with variable stiffness characteristics suitable for physical human–robot interaction applications. In the existing variable stiffness joints, the antagonistic variable stiffness joint has the advantages of simple implementation of variable stiffness mechanism and easy modular design of the nonlinear elastic element. The variable stiffness characteristics of antagonistic variable stiffness joints are realized by the antagonistic actuation of two nonlinear springs. A novel design scheme of the equivalent nonlinear torsion spring with compact structure, large angular displacement range, and desired stiffness characteristics is presented in this article. The design calculation for the equivalent quadratic torsion spring is given as an example, and the actuation characteristics of the antagonistic variable stiffness joint based on the equivalent quadratic torsion spring are illustrated. Based on the design idea of constructing the antagonistic variable stiffness joint with compact structure and high compliance, as well as the different design requirements of the joints at different positions of the multi–degrees of freedom robot arm, nine types of mechanical schemes of antagonistic variable stiffness joint with the open design concept are proposed in this article. Finally, the conceptual joint configuration schemes of the robot arm based on the antagonistic variable stiffness joint show the application scheme of the designed antagonistic variable stiffness joint in the multi–degrees of freedom robot.

变刚度关节是一种具有变刚度特性的柔性执行器，适用于物理人机交互应用。在现有的变刚度关节中，对抗性变刚度关节具有变刚度机构实现简单、非线性弹性元件易于模块化设计的优点。对抗变刚度关节的变刚度特性是通过两个非线性弹簧的对抗驱动来实现的。本文提出了一种结构紧凑、角位移范围大、刚度特性理想的等效非线性扭转弹簧的新颖设计方案。以等效二次扭转弹簧的设计计算为例，阐述了基于等效二次扭转弹簧的对抗变刚度关节的作动特性。基于构建结构紧凑、高柔顺性的对抗变刚度关节的设计思想，以及多自由度机械臂不同位置关节的不同设计要求，提出了九种对抗变刚度的力学方案本文提出了具有开放式设计理念的刚度接头。最后，基于对抗变刚度关节的机械臂概念性关节配置方案展示了所设计的对抗变刚度关节在多自由度机器人中的应用方案。