Design Of Synchronous Acquisition System For Movement Signal And Surface EMG Signal Of Lower Limb

In recent years,the application of sport biomechanic theory in the fields of sport training and physical rehabilitation has become more and more common.Therefore,an increasing demand on performance of microsensor data collection technology have been put forward.Existing measurements of sport biomechanic are mainly based on motion sensors or optical sensors,and they are rarely combined with s EMG(surface electromyogram)signals.Therefore,the needs of deep research in sports training and physical rehabilitation cannot be satisfied.In view of the above situation,the design of the synchronous acquisition system of lower limb movement signals and s EMG signals has been carried out.Including the design of the s EMG signals acquisition module,and the realization of collecting motion signals and s EMG signals synchronously.First,a s EMG signal acquisition module has been designed,which is based on the STM32 series CPU,and the functional circuit includes pre-differential amplification,band-pass filtering,50 Hz notch filter,signal conditioning circuit and IEEE802.11-based wireless transmission module.This module is able to collect surface EMG signals with high input impedance and high common mode rejection ratio.Besides,the noises above 500 Hz,below 10 Hz and around 50 Hz are effectively filtered out.In terms of data transmission,the TCP/IP protocol has been used to pack signals and communicate with the PC.Second,a time synchronization method for multi-node wireless sensor system with different sampling rates has been proposed.This method based on one-way broadcasting,the upper computer controls the hardware to initialize,start acqusition synchronously,and align the beginning moment of data packet through multi-thread correspondence.In the process of data collection,based on the receiver-receiver mechanism(RR),the linear least squares regression algorithm has been used to reduce the synchronization error caused by clock drift and packet loss.Last,according to the division of human walking movement cycle and the matching of key actions with muscle activation and force mode,a walking experiment was designed to test the synchronization effect of the system.The results show that the system can effectively synchronize surface EMG signals and movement signals,the absolute value of the synchronization error under normal working conditions is basically less than 0.1ms,which can accurately match the movement state of the lower limbs and muscles.It is suitable for the research of comprehensive analysis using surface EMG signals and movement signals.