This paper presents a novel design for a Variable Stiffness 3 DoF actuated wrist to improve task adaptability and safety during interactions with people and objects. The proposed design employs a hybrid serial-parallel configuration to achieve a 3 DoF wrist joint which can actively and continuously vary its overall stiffness thanks to the redundant elastic actuation system, using only four motors. Its stiffness control principle is similar to human muscular impedance regulation, with the shape of the stiffness ellipsoid mostly depending on posture, while the elastic cocontraction modulates its overall size. The employed mechanical configuration achieves a compact and lightweight device that, thanks to its anthropomorphous characteristics, could be suitable for prostheses and humanoid robots. After introducing the design concept of the device, this work provides methods to estimate the posture of the wrist by using joint angle measurements and to modulate its stiffness. Thereafter, this paper describes the first physical implementation of the presented design, detailing the mechanical prototype and electronic hardware, the control architecture, and the associated firmware. The reported experimental results show the potential of the proposed device while highlighting some limitations. To conclude, we show the motion and stiffness behavior of the device with some qualitative experiments.

翻译：本文提出了一种新型变刚度三自由度驱动手腕设计，旨在提升与人及物体交互过程中的任务适应性与安全性。该设计采用混合串并联构型实现三自由度腕关节，通过冗余弹性驱动系统（仅使用四台电机）实现整体刚度的主动连续调节。其刚度控制原理类似于人体肌肉阻抗调节机制：刚度椭球体形状主要取决于位姿，而弹性共收缩作用可调节其整体尺寸。所采用的机械构型实现了紧凑轻量化的装置，凭借其拟人化特征，可适用于假肢与仿人机器人。在介绍装置设计概念后，本文提供了通过关节角度测量估算手腕位姿及调节刚度的方法。随后，本文描述了该设计的首台物理样机，详述了机械原型与电子硬件、控制架构及配套固件。实验结果表明了所提出装置的潜力，同时揭示了部分局限性。最后，通过定性实验展示了装置的运动与刚度特性。