Development Of Portable Multi-channel Surface EMG Acquisition System

Surface myoelectricity contains movement,excitement,fatigue and other physiological information of a muscle.Surface electromyography(surface electromyography,sEMG)is a time-related graphical record of potential sequences of muscle contractions in the skin surface which can use surface electrodes to collect.The study of sEMG is helpful to deepen the understanding of human motion,neuromuscular diseases,muscle ergonomics,muscle recovery and muscle fatigue.It is of great value and significance to basic medical research,clinical analysis,sports science,ergonomics and rehabilitation therapy.Based on the characteristics of surface EMG signals,a set of portable multi-channel surface EMG acquisition system based on STM32 and Android APP was developed.The development of the lower machine is based on STM32.The design of hardware part includes multi-channel pre-instrumentation amplifier circuit,right leg drive circuit,hardware filters,STM32 minimum system,Bluetooth circuit,ADC conditioning circuit and power system circuit.The design of hardware part includes STM32 peripheral configuration,ADC sampling program,digital filter and communication protocol design.The lower machine has the characteristics of stable power supply,low power consumption and portability.The development of the upper machine is based on Android APP,which includes interface display,teaching materials display,real-time sEMG curve drawing,sEMG signal analysis and data storage function.The upper machine has the characteristics of easy operation and friendly interface.In addition,the article also introduces a variety of surface EMG signals' standardization,including Average EMG(AEMG),Integral EMG(iEMG),Root mean square(RMS),Median frequency(MF),Mean power frequency(MPF),Zero-crossing rate and Complexity.An automatic detection of the starting and ending points algorithm is presented.The algorithm can automatically detect the corresponding sEMG signals of muscle excitability,cut and combine them into the sheared sEMG signal,which is helpful to the normalization analysis of the sEMG signals.Finally,the hardware circuit performance of the system is evaluated from several aspects: common mode rejection ratio,system power consumption,system specifications and so on.The evaluation results show that the system hardware circuit performance is basically qualified which has small noise,lower power consumption,and system specifications are the same as settings basically.Three experiments were carried out to evaluate the performance of the system from the experiments of wrist extensor and fist,grip strength test of isometric strength and upper arm muscle fatigue experiment.The experimental results show the system basically meets the requirements.