Closed-Loop Control of Grasping With a Myoelectric Hand Prosthesis: Which Are the Relevant Feedback Variables for Force Control?
Closed-Loop Control of Grasping With a Myoelectric Hand Prosthesis: Which Are the Relevant Feedback Variables for Force Control?
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DOI：
10.1109/tnsre.2014.2318431
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发表时间：
2014-09-01
影响因子：
4.9
通讯作者：
Farina, Dario
中科院分区：
文献类型：
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作者：
Ninu, Andrei;Dosen, Strahinja;Farina, Dario
在手假体抓取闭环控制中，反馈给用户的信息通常是实际被控变量，即抓取力。虽然这种选择是直观和合乎逻辑的，但力的产生只是抓取过程中的最后一步。因此，本研究通过改变反馈变量（如闭合速度、抓握力），通过视觉或触觉振动刺激提供给用户，来评估假手在控制抓握强度方面的性能。实验是在13名志愿者身上进行的，他们控制着Otto Bock传感器手速假肢。结果表明，振动触觉模式能够取代视觉反馈。有趣的是，实验表明，直接的力反馈对抓握力的控制不是必需的。受试者确实能够通过预估假体闭合速度的抓握力来预测控制抓握力。因此，没有明确力反馈的抓取不是完全盲目的，这与通常的假设相反。在我们的研究中，我们分析了特定假肢装置的抓取，但结果也适用于具有一个或多个自由度的其他装置。其必要条件是肌电（electromyography， EMG）信号直接按比例控制手部的速度/抓握力，这是肌电控制假肢装置常用的方法。研究结果为闭环肌电控制假肢系统的设计提供了重要依据。
In closed-loop control of grasping by hand prostheses, the feedback information sent to the user is usually the actual controlled variable, i.e., the grasp force. Although this choice is intuitive and logical, the force production is only the last step in the process of grasping. Therefore, this study evaluated the performance in controlling grasp strength using a hand prosthesis operated through a complete grasping sequence while varying the feedback variables (e. g., closing velocity, grasping force), which were provided to the user visually or through vibrotactile stimulation. The experiments were conducted on 13 volunteers who controlled the Otto Bock Sensor Hand Speed prosthesis. Results showed that vibrotactile patterns were able to replace the visual feedback. Interestingly, the experiments demonstrated that direct force feedback was not essential for the control of grasping force. The subjects were indeed able to control the grip strength, predictively, by estimating the grasping force from the prosthesis velocity of closing. Therefore, grasping without explicit force feedback is not completely blind, contrary to what is usually assumed. In our study we analyzed grasping with a specific prosthetic device, but the outcomes are also applicable for other devices, with one or more degrees-of-freedom. The necessary condition is that the electromyography (EMG) signal directly and proportionally controls the velocity/grasp force of the hand, which is a common approach among EMG controlled prosthetic devices. The results provide important indications on the design of closed-loop EMG controlled prosthetic systems.