【Prosthetic Hands】10 Second Generation - EMG Acquisition and Classification

 I used two sets of wet electrodes, each contained three electrodes, to detect EMG signals from the two main forearm muscle groups. The electrodes I adapted are the follow ones:

The glue and the conductive gel usually fail after five times of usage, which was in fact, quite annoying. Though it was not reusable, I managed to acquire EMG signals from them through frequently changing the electrodes. I placed the electrodes just like the colored dots below.

The acquired EMG signals were sent to MATLAB program. The program will identify the peak in a certain period of time and use the data that are closest to the peak (either before or after)  to generate a data set. This data set is then considered a single motion and could be utilized to generate a classifier using K-nearest neighbor method. 

The UI I made with C# is shown below. Each time after user places the electrodes, he/she has to perform wrist flexion, wrist extension, flat and fist for several times so that the program can use these signals to create a new model. Because the overall magnitude of the EMG signals may change according to the placement of the electrodes, I add a function to calibrate the magnitude of the signals.

To be honest, the idea to use wet electrodes was.... not quite feasible because it's time-consuming and bothering for users to reposition the electrodes every single time. Also, since the electrodes I used were not reusable, there will be an extra cost on the electrodes. Based on the recognition results, the EMG signals acquired from this type of electrodes were not reliable enough as well. 

Nonetheless, the experience to acquire EMG signals with relatively inferior electrodes was still rewarding because I did learn lots of knowledge regarding how to process physiological signals and how to combine C# UI with MATLAB codes. The experience eventually helped a lot when I was developing my new prosthetic hand.

Thank you again for reading my articles! I will discuss the relocation of actuators and the new mechanisms applied to compensate the reduction of actuator number in the next article.