Yost Labs’ 3 Space IMU Calibration
To ensure that both of the robot's Yost Labs’ 3-Space Inertial Measurement Units (IMU's) return accurate sensor readings, they must be calibrated occasionally. Additionally, if running the robot in a new setting (with potentially different magnetic field strengths), it may be a good idea to recalibrate the IMUs.
Before continuing with the calibration, download the free Yost Labs 3-Space Sensor Software Suite, which is available for both Mac OSX and Windows (No Linux :-/).
The calibration process for both IMU's is exactly the same. As such, I will cover the process for one IMU and then you can repeat the process for the second.
- Connect the IMU to your computer via micro USB cable
- Launch the 3-Space Suite application (download above)
- Select the appropriate COM Port and click Connect. The GUI should now show a visual of your IMU's orientation. Don't worry if the orientation is noisy or inaccurate, we haven't calibrated yet!
- Download the settings file from the IGVC Google Drive (IGVC/Previous Year Resources/2018-2019 Season/Software/Yost Lab's 3-Space IMU Settings) (This file is not public; you must have access to the RJ Google Drive to access it)
- Click the Sensors tab and select Load Settings From File. Select the file that you downloaded in the previous step. To view the settings, click the Sensors tab, click Settings, and select Advanced. Your settings should now look like this:
- Sphere Calibration: To calibrate for the Earth's magnetic field, we make use of Yost Lab's Sphere Calibration Wizard. To run this, click Sensor, click Calibration, and select Run Sphere Calibration Wizard. Now, spin the IMU around all axes until you have densely covered the whole sphere with magnetometer measurements. The more samples the better, I find that >400 samples densely covering the sphere provides good results.
- Gradient Descent Calibration: To calibrate the IMU's accelerometer and compass, we run the Gradient Descent Calibration Wizard. click Sensor, click Calibration, and select Run Gradient Descent Calibration Wizard. Now, follow the on-screen instructions, making sure that the IMU is properly oriented for each step.
- Finally, in the main app window, click Commit Settings in the Commands section in the bottom right
That's it, after running both calibration wizards you should find that the IMU provides accurate orientation readings. If you want to confirm that the accelerometer's acceleration readings and the gyroscope's angular readings make sense, click Data Charts in the Commands section and double-check that the readings make sense.
To calibrate the second IMU, run the same commands as above.