Dection Of SEMG From Extrinsic Hand Muscles Based On Electrode Array

The hand is one of the most fascinating and sophisticated biological motor systems,and its complex biomechanical and neural architecture of hand poses challenging questions for understanding the control strategies that underlie the coordination of finger movements and forces required for a wide variety of behavioral tasks. Movements and forces of human hand depend on muscle contractions, thus surface electromyography (sEMG) can be utilized to evaluate fingers'biomechanical characteristics. This paper which study the control strategies of neuromuscular system to finger movement is of great importance in the field of rehabilitation medicine, ergonomics, sport medicine, neurophysiology and kinesiology.Because of the inability of the traditional (2 electrode) recording configuration to detect activity at the level of single motor units, and the value of high-density sEMG has been proven in fundamental research and specific diagnostic questions. However, its applications are no broad partly due to limitations of construction principles of conventional electrode array systems. On this basis then, we developed a type of thin, highly flexible, linear and 2-D multi-electrode sEMG grid device, which is manufactured using flexprint techniques. The material (Polyimide, 50μm thick) used as electrode carrier allows this new sensor to own higher mechanical flexibility;electrodes with gold-coated (2μm thick) surface have a lower resistance;And adhesive electrode array is attached to the skin using specially prepared double sided adhesive tape whose was made of acrylic polymer. Test of electrical characteristic shows this electrode device has lower impedance and well repeatability; high baseline stablility, best sEMG signals and a low signal noise level guarantee its practical application.Strain gauges modelled JHBM convert fingertip force signals into microvolt-level voltage signals, these voltage signals were amplified by means of the two-stage amplifiers which consist of instrumentation amplifier AD620 and operational amplifier OP07, and then complete analog-digital conversion of the fingertip force information using a data acquisition card USB6008 of NI company.This paper conduct the preliminary exploration for control mechanism that multi-digit muscle regulate finger's motor function utilizing designed devices. The experimental task consist of the four force levels (6N, 8N, 10N, 12N) of separate index finger (I) and middle finger (M), as well as the three force levels (8N, 12N, 16N) of the combination of index finger and middle finger (IM). Five healthy volunteers were required to produce a certain force to match the target force for 5s, and 6-channel sEMG was recorded using a two-deminsion electrode array over FDS simultaneously. sEMG of each channel was extracted based on the effective force segment, and these sEMG were band-pass filtered with frequency range of 20-500Hz respectively, then RMS, Ptotal and Pmax of sEMG for each channel was calculated and colorful topographical maps were constructed for the study of spatial activity. Our experimental results reveal three findings: (1) the spatial distribution region and activation intensity increase with the finger's force production, and the position of highest RMS was shifted towards radial while finger's force production changed; (2) the sensitivity of sEMG, defined as the slope of RMS v.s. force strength, differed from the electrode locations; (3) the activation patterns of FDS are markedly affected by the finger's active patterns under the same force level,and FDS's activation intensity and region of index finger is observably larger than other patterns designed in our study. These preliminary experimental results indicate that the characteristic distribution of sEMG depends on the finger's force production level, electrode location and finger's active pattern. The current work suggests that spatial-temporal recruitment of FDS's motor units is affected by force production levels and finger's active pattern, and sEMG's characteristic parameters such as RMS,Ptotal as well as Pmax can be used as key parameters to reflect muscle activation level and describe finger's actions and spatial activity of multi-digit muscles.