Adaptive whitening of the electromyogram to improve amplitude estimation
Adaptive whitening of the electromyogram to improve amplitude estimation
复制标题
DOI：
10.1109/10.844217
复制
发表时间：
2000-06-01
影响因子：
4.6
通讯作者：
Farry, KA
中科院分区：
文献类型：
--
作者：
Clancy, EA;Farry, KA
先前的研究表明，白化表面肌电图（EMG）可以改善EMG幅度估计（其中EMC幅度定义为EMG的时变标准差）。然而，传统的白化通过线性滤波器似乎击中在低EMG幅度水平，也许是由于在测量的EMG中的加性背景噪声，本文描述了一种自适应白化技术，克服了这个问题，级联的非自适应白化滤波器，自适应维纳滤波器，和自适应增益校正。这些阶段可以从两个、五秒持续时间、恒定角度、恒定力的收缩校准，一个在参考水平[例如，50%最大自主收缩（MVC）]，一个在0%MVC。在实验研究中，受试者使用实时EMC幅度估计来跟踪均匀密度、带宽受限的随机目标。自适应白化或多通道处理将跟踪误差大约减小到使用测力计信号作为反馈所获得的误差的一半。在1.00 Hz的带宽，所有的EMG处理器的错误相当于测力计信号，反映了在这个任务中的错误是由主体的无法跟踪目标在这个带宽。加性噪声电平、平滑窗口长度和跟踪带宽的增加会削弱白化的优势。
Previous research showed that whitening the surface electromyogram (EMG) can improve EMG amplitude estimation (where EMC amplitude is defined as the time-varying standard deviation of the EMG). However, conventional whitening via a linear filter seems to hit at low EMG amplitude levels, perhaps due to additive background noise in the measured EMG, This paper describes an adaptive whitening technique that overcomes this problem by cascading a nonadaptive whitening filter, an adaptive Wiener filter, and an adaptive gain correction. These stages can be calibrated from two, five second duration, constant-angle, constant-force contractions, one at a reference level [e,g,, 50% maximum voluntary contraction (MVC)] and one at 0% MVC, In experimental studies, subjects used real-time EMC amplitude estimates to track a uniform-density, band-limited random target, With a 0.25-Hz bandwidth target, either adaptive whitening or multiple-channel processing reduced the tracking error roughly half-way to the error achieved using the dynamometer signal as the feedback. At the 1.00-Hz bandwidth, all of the EMG processors had errors equivalent to that of the dynamometer signal, reflecting that errors in this task were dominated by subjects' inability to track targets at this bandwidth. Increases in the additive noise level, smoothing window length, and tracking bandwidth diminish the advantages of whitening.