Key Lab for Health Informatics of Chinese Academy of Science, Shenzhen, China.
Ann Biomed Eng. 2011 Jun;39(6):1779-87. doi: 10.1007/s10439-011-0265-x. Epub 2011 Feb 4.
Historically, the investigations of electromyography (EMG) pattern recognition-based classification of intentional movements for control of multifunctional prostheses have adopted the filter cut-off frequency and sampling rate that are commonly used in EMG research fields. In practical implementation of a multifunctional prosthesis control, it is desired to have a higher high-pass cut-off frequency to reduce more motion artifacts and to use a lower sampling rate to save the data processing time and memory of the prosthesis controller. However, it remains unclear whether a high high-pass cut-off frequency and a low-sampling rate still preserve sufficient neural control information for accurate classification of movements. In this study, we investigated the effects of high-pass cut-off frequency and sampling rate on accuracy in identifying 11 classes of arm and hand movements in both able-bodied subjects and arm amputees. Compared to a 5-Hz high-pass cut-off frequency, excluding the EMG components below 60 Hz decreased the average accuracy of 0.1% in classifying the 11 movements across able-bodied subjects and increased the average accuracy of 0.1 and 0.4% among the transradial (TR) and shoulder disarticulation (SD) amputees, respectively. Using a 500 Hz instead of a 1-kHz sampling rate, the average classification accuracy only dropped about 2.0% in arm amputees. The combination of sampling rate and high-pass cut-off frequency of 500 and 60 Hz only resulted in about 2.3% decrease in average accuracy for TR amputees and 0.4% decrease for SD amputees in comparison to the generally used values of 1 kHz and 5 Hz. These results suggest that the combination of sampling rate of 500 Hz and high-pass cut-off frequency of 60 Hz should be an optimal selection in EMG recordings for recognition of different arm movements without sacrificing too much of classification accuracy which can also remove most of motion artifacts and power-line interferences for improving the performance of myoelectric prosthesis control.
从历史上看,基于肌电图 (EMG) 模式识别的多功能假肢意图运动控制分类研究采用了 EMG 研究领域常用的滤波器截止频率和采样率。在多功能假肢控制的实际实现中,希望具有更高的高通截止频率以减少更多的运动伪影,并使用更低的采样率来节省假肢控制器的数据处理时间和内存。然而,尚不清楚高高通截止频率和低采样率是否仍然保留了足够的神经控制信息,以便准确分类运动。在这项研究中,我们研究了高通截止频率和采样率对识别健全受试者和上肢截肢者的 11 类手臂和手部运动的准确性的影响。与 5-Hz 高通截止频率相比,排除低于 60Hz 的 EMG 成分会降低 11 个运动分类的平均准确性 0.1%,而在桡骨 (TR) 和肩部离断 (SD) 截肢者中分别增加了 0.1%和 0.4%。使用 500 Hz 而不是 1 kHz 采样率,上肢截肢者的分类准确性平均仅下降约 2.0%。与通常使用的 1 kHz 和 5 Hz 值相比,采样率和高通截止频率为 500 和 60 Hz 的组合仅导致 TR 截肢者的平均准确性降低约 2.3%,SD 截肢者降低 0.4%。这些结果表明,对于识别不同的手臂运动,采样率为 500 Hz 和高通截止频率为 60 Hz 的组合应该是 EMG 记录的最佳选择,而不会牺牲太多的分类准确性,这也可以消除大部分运动伪影和电源线干扰,从而提高肌电假肢控制的性能。