Despite important advancements in control and mechatronics of myoelectric prostheses, the communication between the user and his/her bionic limb is still unidirectional, as these systems do not provide somatosensory feedback. Electrotactile stimulation is an attractive technology to close the control loop since it allows flexible modulation of multiple parameters and compact interface design via multi-pad electrodes. However, the stimulation interferes with the recording of myoelectric signals and this can be detrimental to control. We present a novel compact solution for simultaneous recording and stimulation through dynamic blanking of stimulation artefacts. To test the system, a feedback coding scheme communicating wrist rotation and hand aperture was developed specifically to stress the myoelectric control while still providing meaningful information to the subjects. Ten subjects participated in an experiment, where the quality of closed-loop myoelectric control was assessed by controlling a cursor in a two degrees of freedom target-reaching task. The benchmark performance with visual feedback was compared to that achieved by combining visual feedback and electrotactile stimulation as well as by using electrotactile feedback only. There was no significant difference in performance between visual and combined feedback condition with regards to successfully reached targets, time to reach a target, path efficiency and the number of overshoots. Therefore, the quality of myoelectric control was preserved in spite of the stimulation. As expected, the tactile condition was significantly poorer in completion rate (100/4% and 78/25% for combined and tactile condition, respectively) and time to reach a target (9/2 s and 13/4 s for combined and tactile condition, respectively). However, the performance in the tactile condition was still good, with no significant difference in path efficiency (38/8%) and the number of overshoots (0.5/0.4 overshoots), indicating that the stimulation was meaningful for the subjects and useful for closed-loop control. Overall, the results demonstrated that the developed system can provide robust closed-loop control using electrotactile stimulation. The system supports different encoding schemes and allows placing the recording and stimulation electrodes next to each other. This is an important step towards an integrated solution where the developed unit will be embedded into a prosthetic socket.

中文翻译：

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紧凑的系统，用于同时刺激和记录，用于闭环肌电控制

尽管在肌电假体的控制和机电一体化方面取得了重要进展，但是用户和他/她的仿生肢体之间的通信仍然是单向的，因为这些系统不提供体感反馈。电触觉刺激是闭合控制回路的一项引人注目的技术，因为它允许灵活地调节多个参数，并通过多焊盘电极实现紧凑的界面设计。然而，刺激干扰了肌电信号的记录，这可能不利于控制。我们提出了一种新颖的紧凑型解决方案，用于通过刺激伪影的动态消隐同时记录和刺激。要测试系统，专门开发了一种传达手腕旋转和手部开度的反馈编码方案，以强调肌电控制，同时仍向受试者提供有意义的信息。十名受试者参加了一项实验，该实验通过在两个自由度目标达成任务中控制光标来评估闭环肌电控制的质量。将具有视觉反馈的基准性能与通过结合视觉反馈和触觉刺激以及仅使用触觉反馈所获得的性能进行了比较。对于成功达到目标，达到目标的时间，路径效率和超调次数，视觉和组合反馈条件之间的性能没有显着差异。所以，尽管有刺激，但仍保持了肌电控制的质量。如预期的那样，触觉条件的完成率（组合和触觉条件分别为100/4％和78/25％）和达到目标的时间（组合和触觉分别为9/2 s和13/4 s）明显较差条件）。然而，在触觉条件下的表现仍然良好，路径效率（38/8％）和超调次数（0.5 / 0.4超调）均无显着差异，表明刺激对受试者有意义且对封闭运动有用回路控制。总体而言，结果表明，所开发的系统可以使用触觉刺激提供鲁棒的闭环控制。该系统支持不同的编码方案，并允许将记录电极和刺激电极彼此相邻放置。