Abstract In this paper, a novel design method for compact nonlinear stiffness actuator (NSA) is proposed. By combining cam with off-the-shelf torsion spring and designing the effective profile curve of cam, the proposed NSA can perform desired bidirectional symmetric deflection-torque profiles with monotonic increasing slopes that follow the “low load, low stiffness and high load, high stiffness” principle inspired by biomechanics. To adapt to external loads in different directions, the proposed NSA is designed to have bidirectional symmetric stiffness characteristics by using symmetrical cams and mutilated gear transmission. The derivation process of the effective cam profile curve is introduced in detail. And then, a prototype of the designed NSA is built for verification. Simulated and experimental stiffness tests demonstrate the effectiveness of the proposed design method in realizing desired nonlinear stiffness. Preliminary experiments of step response in controlling torque show good performance of the proposed NSA in terms of dynamic response.

中文翻译：

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具有用户定义偏转扭矩曲线的非线性刚度执行器的新设计方法

摘要 本文提出了一种新型的紧凑型非线性刚度致动器（NSA）设计方法。通过将凸轮与现成的扭力弹簧相结合并设计凸轮的有效轮廓曲线，所提出的 NSA 可以执行所需的双向对称偏转扭矩轮廓，其单调递增斜率遵循“低负载、低刚度和高负载、高刚度”原理受生物力学启发。为了适应不同方向的外部载荷，所提出的 NSA 被设计为通过使用对称凸轮和残缺齿轮传动来具有双向对称刚度特性。详细介绍了有效凸轮轮廓曲线的推导过程。然后，构建设计的 NSA 原型以进行验证。模拟和实验刚度测试证明了所提出的设计方法在实现所需的非线性刚度方面的有效性。控制扭矩的阶跃响应的初步实验表明，所提出的 NSA 在动态响应方面具有良好的性能。