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三自由度变刚度驱动腕关节的设计，旨在提升与人及物体交互过程中的任务适应性和安全性。该设计采用混合串并联构型，通过冗余弹性驱动系统，仅使用四个电机即可实现三自由度腕关节，并能够主动且连续地调节整体刚度。其刚度控制原理类似于人体肌肉阻抗调节，刚度椭球的形状主要取决于姿态，而弹性协同收缩则调节其整体大小。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，有望适用于假肢和仿人机器人。在介绍该装置的设计理念后，本文提出了利用关节角度测量值估计腕关节姿态并调节其刚度的方法。随后，本文描述了所提出设计的首台物理样机，详细阐述了机械原型与电子硬件、控制架构及配套固件。实验结果表明了该装置的潜力，同时也指出了其局限性。最后，通过定性实验展示了该装置的运动与刚度特性。