To physically interact with a rich variety of environments and to match situation-dependent requirements, humans adapt both the force and stiffness of their limbs. Reflecting this behavior in prostheses may promote a more natural and intuitive control and, consequently, improve prostheses acceptance in everyday life. This pilot study proposes a method to control a prosthetic robot hand and its impedance, and explores the utility of variable stiffness when performing activities of daily living and physical social interactions. The proposed method is capable of a simultaneous and proportional decoding of position and stiffness intentions from two surface electro-myographic sensors placed over a pair of antagonistic muscles. The feasibility of our approach is validated and compared to existing control modalities in a preliminary study involving one prosthesis user. The algorithm is implemented in a soft under-actuated prosthetic hand (SoftHand Pro). Then, we evaluate the usability of the proposed approach while executing a variety of tasks. Among these tasks, the user interacts with other 12 able-bodied subjects, whose experiences were also assessed. Several statistically significant aspects from the System Usability Scale indicate user's preference of variable stiffness control over low or high constant stiffness due to its reactivity and adaptability. Feedback reported by able-bodied subjects reveal a general tendency to favor soft interaction, i.e., low stiffness, which is perceived more human-like and comfortable. These combined results suggest the use of variable stiffness as a viable compromise between firm control and safe interaction which is worth investigating further.

中文翻译：

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探索假肢的刚度调节及其在操纵和社交互动中的感知功能。

为了与各种各样的环境进行物理交互并满足因地制宜的要求，人类可以适应四肢的力量和僵硬感。在假肢中反映这种行为可以促进更自然，更直观的控制，从而提高假肢在日常生活中的接受度。这项初步研究提出了一种控制假肢机器人手及其阻抗的方法，并探索了在进行日常生活活动和身体社交互动时可变刚度的用途。所提出的方法能够同时并成比例地从放置在一对拮抗肌肉上的两个表面肌电图传感器对位置和刚度意图进行解码。在涉及一名假肢使用者的初步研究中，我们的方法的可行性得到了验证，并与现有的控制方式进行了比较。该算法在柔软的，未充分操作的假肢手（SoftHand Pro）中实现。然后，我们在执行各种任务时评估所提出方法的可用性。在这些任务中，用户与其他12名健全的主体进行了交互，还评估了他们的经验。系统可用性量表中的几个具有统计意义的方面表明，由于其反应性和适应性，用户对可变刚度控制的偏爱于低或较高的恒定刚度。身体强健的受试者报告的反馈显示出倾向于软互动（即低刚度）的总体趋势，这种互动被认为更像人类，更加舒适。