【Prosthetic Hands】18 Third Generation - Electromechanical System and Integration

Now the hardware and the software are ready. The final step is to integrate them into one device. The communication between the MYO armband, the computer and the prosthetic hand is achieved through Bluetooth and WiFi network. The signal path is shown below.

In the connection between MYO armband and the MATLAB program, I utilize the "MYO SDK" by Thalmic Lab and "Myo SDK MATLAB MEX Wrapper" by Mr. Mark Tomaszewski. The acquired EMG signals are sent to the MATLAB program to extract features and classify. The classification results are sent to the microcontroller on the prosthetic hand via WiFi. The microcontroller I use is "NodeMCU", which is quite common in the projects related to IoT. NodeMCU can be programmed with Arduino codes, where I implement Practical Strategy.

Here I would like to talk more about the electromechanical system. The actuators I used are the "KST DS315MG", which can work with 7.4 V (two 18650 batteries in series). The benefit of choosing this servo motor is that it has sufficient torque output and compact size, and its operating voltage range overlaps with that of the NodeMCU. As a result, I can design the circuit simply by adding fuses and a switch without involving any buck–boost converter.

Now I can control the prosthetic hand with my EMG signals. I will display some demo videos in the next article.