6. (24 marks) Raw EMG and Integrated EMG signals
a. Plot the time-domain raw EMG of the forearm muscle. Please briefly discuss how EMG is different from ECG and PPG in terms of the waveform features. (4 marks)
b. Please compare and briefly discuss the signal amplitudes of ECG and EMG in units of mV. (2 marks)
c. Please realize time integration of EMG as integrated EMG (unit of the signal amplitude mV*sec). What does this integrated EMG portray? (Hint: Integrated EMG is defined as the area under the curve of the rectified EMG signal using a fixed temporal window length.
The rectified EMG signal is obtained by taking the absolute value of the raw EMG signal. You may try various window lengths when performing integration. You may start with a window length of 101 samples, which is equivalent to 101/(fs=500Hz)≈0.2s.)
i. (2 marks) Plot the rectified EMG signal and raw EMG signal in the same figure using
the MATLAB ‘hold on’ command.
ii. (8 marks) Plot the integrated EMG signal
d. Now, let’s extract two groups of signals from this entire raw EMG signal. One group is from sample point 1300 to 2100 and the other is from the 2400th to 3600th samples as the human subject did two separate clenches.
i. Please estimate and plot the power spectrum of the first group EMG signal (sample point 1300 to 2100) using the autocorrelation concept. Please display the power in units of dB. (3 marks)
ii. Please estimate and plot the power spectrum of the second group EMG signal (sample point 2400 to 3600) using the autocorrelation concept. Please display the power in units of dB.(3 marks)
iii. Compare i) and ii). Briefly discuss if and how we can relate the power spectrum to muscle activation at two different clench forces. (2 marks)
