pankarfa / accelerometer-calibration

A general method (with Python scripts) for calibrating accelerometer sensors.

Accelerometer Calibration Procedure

A general method (with Python scripts) for calibrating accelerometer sensors.

Developed By: Michael Wrona, B.S. Aerospace Engineering

GitHub: @michaelwro

YouTube: @MicWro Engr

Blog: mwrona.com

Pip Install Python3 Dependencies

$ pip3 install numpy matplotlib pandas  # pip for Windows

Conda Install Python3 Dependencies

(myenv) $ conda install -c conda-forge numpy matplotlib pandas

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IMPORTANT: Before following these steps, I highly recommend watching the video I created about this process. You can watch it at this link.

Step 1: Output Comma-Separated Data

record-data.py expects to read comma-separated accelerometer data from a serial connection. Each sensor is different, so you will need to write your own microcontroller code to output comma-separated accelerometer measurements to a serial port, similar to this format:

0.0642208,-0.05490976,1.02357024

Step 2: Configure record-data.py

Open record-data.py in a text editor. Change the variables at the top as required.

Step 3: Measure Accelerometer Data

Once you can output comma-separated raw accelerometer measurements over a serial connection, you can begin logging data. Run record-data.py to begin logging data. Have the accelerometer flat and stationary and press ENTER as prompted. Then, type 'm' as prompted to take a measurement. Move the accelerometer to a different orientation, then take another measurement. Repeat for many accelerometer orientations (sideways, upside down, left, right, etc.).

Step 4: Save Measurements to File

Once you are satisfied with the number of measurements, type 'q' to save the measurements to a tab-delimited file.

Step 5: Calibrate with Magneto

Magneto is an ellipsoid-fitting software used to calibrate accelerometer and magnetometer sensors. Magneto expects raw measurements to be input as a tab-delimited text file. The norm of the gravitational field will be the ideal magnitude of your accelerometer measurements. For example, my accelerometer output data in G's, so my norm/magnitude would be 1. Load your text file generated by record-data.py, then click 'calibrate.' BAM! It's that easy!

Step 6: Visualize Results

Open plot-calibration-data.py in a text editor. Copy the A^-1 matrix and bias vector values to the Python code and specify the tab-delimited text file of uncalibrated measurements. Run the code and compare uncalibrated and calibrated data!

Resources

• Magneto download link
• YouTube video
• GitHub code repo