Estudo de caso e viabilidade de transdutores Miográficos

Abstract

This final paper will describe a low cost solution for the study of myographic signals, which was initially performed using electrodes. However, due to the complexity of the circuit and the impossibility of reusing the electrodes, the work proposes a feasibility study of the replacement of theses electrodes to piezoelectric sensors, in order to simplify the solution to capture the movement. The resulting signals from the excitation of these transducers have small amplitude and innumerous interferences. Therefore, it is necessary to develop a specific circuit to treat the output signals of the transducers, since the electrode and the piezoelectric have different characteristics. For the electrode, the circuit will consist of an instrumentation amplifier, performing a common rejection mode, in addition to high pass, low pass and band rejects filters. While for the piezoelectric, the signal has a simpler treatment, requiring only a differential amplifier. For the two circuits, the last stage was a voltage adder, to allow the analogue/digital conversion of the entire amplitude from the captured signal. In this way, the work developed will be detailed the environments developed for each sensor used, including a signal conditioning circuit, analog/digital converter, data transfer and analysis of results. On both occasions were observed contractions from biceps, contemplating six different movements. Each movement was repeated ten times, thus, five of these repetitions will be used of adjustment and the other five for validation of these adjustments. In order to aid the experimental process, a test button was used, which remained pressed from the beginning to the end of the contraction, in order to audit the output of the transducer. Analyzing the data, an algorithm was created to detect the moments of onset of contraction, beginning of relaxation and end of movement, from the five adjustment samples in each type of movement.