Study of Optimum Surface Electrode Positioning for Myoelectric Signal Detection of Typical Human Grasping

Abstract

Recently, commercially available myoelectric prosthetic hands have complied with advanced technology direction. Unfortunately, there are many customers from middle to low-income groups who emphasize on affordability, especially those living in developing countries. There is a need to build low cost myoelectric prosthetics that use more affordable material, easily operated mechanism, and simple myoelectric control by few channels of myoelectric module. Myoelectric hand uses myoelectric signal from the muscle to activate and control the movement of finger. Typical prosthetic receives the myoelectric signal by placing electrodes on the skin surface of human arm so that it can only capture small magnitude compare to implanting the electrodes inside the muscles. With only a few electrodes, detecting myoelectric signal on the skin surface should take proper and careful procedure. In this research, we used three channels to detect signals from the groups of muscles, which activate the hand to perform grasping flexion as well as its extension. This paper provides a preliminary study of electrode positions that given the best signal strength for five basic hand grasping. Three position scenarios was used to place each channel electrodes set on the top of muscle spots. They are pollicis longus muscles, extensor digitorium superficialis muscle, and between both of the muscles. A biopotential amplifier based on AD620 was used to amplify the signal. Finally, the raw signals were analyzed using DSSF3 software. We identified the position mapping and concluded that all of the three electrode positions are important. To build a hand with the capability of basic grasps, the three electrode positions are needed.