Overview
This biomedical sensor was created for the final project of BIOMEDE 458 (Biomedical Instrumentation and Design). We created an EMG device that would track the position of the patient's foot to verify that their rehabilitation is progressing. This project consisted of procuring sensors, designing a circuit to power and filter the sensors, data analysis on LabVIEW, and displaying the information in a comprehensible manner.
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We started the project by procuring an accelerometer. We decided on using a ADCL335 (spec sheet) since we had it on hand and it was the simplest to implement into our system. Next, we divided the project up into two sections: 1) accelerometer calibration and 2) EMG readings.
1) Accelerometer
The position of the patient's foot was determined by the difference in angles that the foot and shin make during peak exertion and rest. To find this, we first calibrated the sensor such that the patient's resting position correlated to zero degrees.
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To ensure that the x-, y-, and z- axes were consistent between trials, we constructed a box that would hold the accelerometer in a way where each axis would be perpendicular to a box face.
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The sensor assembly would then be placed on the patient's foot and would then be calibrated. The voltages for each axis would then be stored on LabVIEW representing the resting angle.
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During rehabilitative exercises, the ​sensor would measure the peak angle the patient would reach. After the exercise is done, LabVIEW would present the final range of motion which can be tracked.
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2) EMG
The EMG would evaluate the patient's muscle health. To do this, we attached electrode pads on the ends of the tibialis anterior muscle. Since the signals were small and noisy, we created a circuit to amplify and filter the signal for post-processing.
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The figure on the left is the circuit diagram for filtering and amplifying our signal output from the EMG and the figure on the right is the built circuit.
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LabVIEW
LabVIEW is a visual programming language we used to analyze our signal data and to display a visual for the patient / caretaker. Below is the display shown to the patient and the code to create it (code in the google drive).
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Takeaways
This project helped us solidify our knowledge of basic circuits and how to create a biomedical sensor. I was in charge of the accelerometer and also the hardware of the project, so I was able to get more experience on creating/designing circuits and LabVIEW.
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Link to project folder:
Google Drive
