Design and development of low cost biceps tendonitis physiotherapy monitoring system using surface EMG electrodes for automated rehabilitation
Poo, Tarn Shi
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Electromyogram signal (EMG) is an electrical potential signal generated from EMG electrodes attached on the skin when there is a contraction of muscles. These signals are useful in kinesiology study, biomedical research, clinical usage, physiotherapy and muscle dysfunction diagnosis. However, current acquisition systems that are available in the market are expensive and bulky. Therefore, this research attempts to design and develop a low cost EMG acquisition system for monitoring biceps tendonitis physiotherapy. The proposed EMG acquisition system uses surface EMG electrodes for EMG signal detection. In the design of the EMG acquisition circuit, the EMG signal is amplified in two stages to convert it into an observable scale. The inherent noise acquired from the power line of 50Hz frequency is eliminated with a single hybrid IC notch filter. Then, the rectification and low pass filter modules will convert the EMG signal to a linear envelop waveform. This signal is then sampled by a signal processing module. The analogue linear envelop EMG signal is sampled into a 24 bit digital data. An algorithm is developed and coded to send the digital data into the computer. The digital EMG data is then reassembled and displayed using a software scope on the computer. In order to test the system, 20 subjects are requested to perform a set of rehabilitation exercise and the EMG signals were recorded. The results collected from this proposed EMG acquisition system is compared with the readings obtain from a commercial product. This comparison gives an average error of ±0.05m V in the readings. Hence, the proposed designed is deemed to be satisfactory.