VB3i MANUAL
Page | 21
22 May 2014
Kalman Filter calibration – High dynamic tests
To produce the optimum level of accuracy as quickly as possible, a series of specific manoeuvres can be performed
that help the Kalman filter characterise the outputs from the IMU. Note that while this is recommended, it is not
completely necessary as the Kalman filter will have enough data to achieve accurate results within a few minutes of
normal dynamic driving (including left and right hand turns, braking and accelerating).
Recommended procedure
1. Wait for IMU to complete 30 second stationary initialisation, VB3i front panel IMU LED will change from flashing
orange to flashing green upon completion. If the vehicle moves before initialisation finishes, the 30 second process
will restart once stationary again.
2. Drive in a ‘figure of eight’ at least twice.
These can be as little as 5m in radius (almost full-lock in some vehicles), but 10m is better. The vehicle should be
travelling above 15km/h during this procedure in order to generate sufficient forces for the calibration process.
3. Accelerating hard from standstill to 50km/h or above, perform two brake stops with a decel force of at least 0.5g.
When is the calibration required?
When carrying out high dynamic tests such as braking and ESC testing, this recommended process calibrates the
Kalman filter as quickly as possible. When carrying out low dynamic tests such as driving on urban routes, or doing
long term data collection, then this calibration is not as critical.
Re-running the calibration
The Kalman filter is constantly adapting its calibration depending on the information received from GPS and the IMU.
Therefore, if the vehicle is left stationary for a long time, or the IMU is moved from its mounting position, then the
calibration procedure should be repeated if further high dynamic testing is to be carried out.
The calibration should also be repeated after anything which causes the communication to break between IMU and
VBOX, such as:
Power cycle to either IMU or VBOX.
‘RL Config’ software is used to read IMU settings.
‘VBOX Tools’ software is used to read VBOX settings.
A GPS Coldstart is performed
What happens if this isn’t done?
If this procedure cannot be carried out as above then the speed accuracy will be reduced, especially for the first few
minutes until the Kalman Filter is able to calibrate itself. We strongly recommend that the Kalman Filter is calibrated
when carrying out high dynamic tests.
