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RACELOGIC Support Centre

Kalman Filter Calibration - IMU04


When using IMU filter it is important to perform the full calibration procedure before meaningful testing commences. The calibration procedure is a series of specific manoeuvres that should be performed that help the Kalman filter characterise the outputs from the IMU. 

If the calibration procedure is not performed, the Kalman filter will still function, but may not produce the high level of accuracy until dynamic manouevres in the X and Y plane have been performed (i.e. left and right hand turns, braking and accelerating). This should occur after a few minutes driving.

Recommended procedure

  1. Park the vehicle in an open area where the GNSS antenna has a clear view of the sky.
  2. Make sure that you have RTK fix. 
  3. Remain static and wait for the IMU to complete the 30-second stationary initialization.

    Note: If the IMU detects movement before the initialisation finishes, the 30-second process will restart when the vehicle is stationary again.
  4. When the LED on the front panel of the IMU changes from flashing orange to flashing green, drive forward to complete the initialisation of the IMU. 
  5. Continue to an open area to perform the calibration procedure.
  6. Drive in a figure of eight at least twice. The vehicle should be at a speed of more than 5 km/h during this procedure to generate sufficient force for the calibration process.

Note: If you cannot do figure of eights, you can perform left/right slalom-type manouvres to achieve a similar effect. 


KF Calibration.png

  1. Accelerate hard from a standstill to 50 km/h or above. Perform a brake stop with a deceleration force of at least 0.5 g. You must perform this step twice. 

kf_calibration2 (1).png

When is the calibration required? 

Re-running the calibration

The Kalman Filter is constantly adapting its calibration depending on the information it receives from the GNSS receiver and the IMU. Therefore, if the vehicle is left stationary for a long time, or if an External IMU is moved from its mounting position, you should repeat the calibration procedure.

The calibration should also be repeated if there has been a communication break between the VBOX unit and the External IMU, such as:

  • You power cycle either the VBOX unit or the External IMU.
  • You change the VBOX IMU settings.
  • You use the VBOX Setup Software to read the VBOX unit's settings.
  • You use the VBOX Setup Software to read the External IMU settings.
  • You perform a GNSS Coldstart.

What happens if this isn’t done?

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