We recently introduced the concept of a new human-machine interface (the myokinetic control interface ) to control hand prostheses. The interface tracks muscle contractions via permanent magnets implanted in the muscles and magnetic field sensors hosted in the prosthetic socket. Previously we showed the feasibility of localizing several magnets in non-realistic workspaces. Here, aided by a 3D CAD model of the forearm, we computed the localization accuracy simulated for three different below-elbow amputation levels, following general guidelines identified in early work. To this aim we first identified the number of magnets that could fit and be tracked in a proximal (T1), middle (T2) and distal (T3) representative amputation, starting from 18, 20 and 23 eligible muscles, respectively. Then we ran a localization algorithm to estimate the poses of the magnets based on the sensor readings. A sensor selection strategy (from an initial grid of 840 sensors) was also implemented to optimize the computational cost of the localization process. Results showed that the localizer was able to accurately track up to 11 (T1), 13 (T2) and 19 (T3) magnetic markers (MMs) with an array of 154, 205 and 260 sensors, respectively. Localization errors lower than 7% the trajectory travelled by the magnets during muscle contraction were always achieved. This work not only answers the question: “how many magnets could be implanted in a forearm and successfully tracked with a the myokinetic control approach?”, but also provides interesting insights for a wide range of bioengineering applications exploiting magnetic tracking.

中文翻译：

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肌动能控制界面：前肢截肢可以植入多少个磁铁？来自模拟环境的证据

我们最近介绍了新的人机界面（ 肌动控制界面 ）以控制手部假肢。该界面通过植入到肌肉中的永磁体和位于假牙窝中的磁场传感器跟踪肌肉收缩。之前，我们展示了在非现实工作空间中定位多个磁体的可行性。在此，借助前臂的3D CAD模型，我们按照早期工作中确定的一般准则，计算了三种不同的肘下截肢水平所模拟的定位精度。为了达到这个目的，我们首先确定了可以在近端（T1），中段（T2）和远端（T3）截肢术中适合并跟踪的磁铁数量，分别从18、20和23块合格的肌肉开始。然后，我们运行了一个定位算法，根据传感器的读数估算磁体的姿态。还实施了传感器选择策略（来自840个传感器的初始网格），以优化定位过程的计算成本。结果表明，该定位器能够分别利用154、205和260个传感器阵列准确地跟踪多达11个（T1），13个（T2）和19个（T3）磁性标记（MM）。定位误差始终低于磁铁在肌肉收缩过程中所经过的轨迹的7％。这项工作不仅回答了以下问题：“可以在前臂中植入多少磁铁，并通过肌动力控制方法成功地进行跟踪？”，还为利用磁跟踪的各种生物工程应用提供了有趣的见解。结果表明，该定位器能够分别利用154、205和260个传感器阵列准确地跟踪多达11个（T1），13个（T2）和19个（T3）磁性标记（MM）。定位误差始终低于磁铁在肌肉收缩过程中所经过的轨迹的7％。这项工作不仅回答了以下问题：“可以在前臂中植入多少磁铁，并通过肌动力控制方法成功地进行跟踪？”，还为利用磁跟踪的各种生物工程应用提供了有趣的见解。结果表明，该定位器能够分别利用154、205和260个传感器阵列准确地跟踪多达11个（T1），13个（T2）和19个（T3）磁性标记（MM）。定位误差始终低于磁铁在肌肉收缩过程中所经过的轨迹的7％。这项工作不仅回答了以下问题：“可以在前臂中植入多少磁铁，并通过肌动力控制方法成功地进行跟踪？”，还为利用磁跟踪的各种生物工程应用提供了有趣的见解。