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RACELOGIC Support Centre

Benefits of IMU and Kalman filter integration for slip angle measurement

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What is Slip Angle?

Slip angle from a VBOX 3iSL is the difference between the direction a vehicle is traveling (course over ground measured from the primary GPS/GNSS  antenna), known as the Heading, and the direction that the body of the vehicle is pointing (measured using the dual antenna GPS/GNSS antennas), known as the True Heading.

Slip angle and translated slip angle parameters are calculated from these two GPS/GNSS derived components.
 

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Heading

When the IMU Kalman filter is running, the Heading parameter will be processed by the Kalman filter, giving a cleaner heading with Lever Arm compensation. This can be seen by comparing Heading to Raw Heading. This ‘cleaner’ Heading parameter is then used in the Slip angle and Translated slip angle calculations.

True Heading

True Heading channel is not processed by the Kalman Filter, however when an IMU is connected, the VBOX 3iSL will use the IMU’s Yaw rate during translated slip angle calculations. The IMU yaw rate has a lower noise level than the dual antenna yaw rate, resulting in a cleaner translated slip angle measurement parameter set. Note, this will not have any impact on the standard Slip Angle channel as it does not require Yaw Rate for the calculation. Also note that the Kalman filter does not need to be enabled to get this additional benefit.

Conclusion

Heading will be processed by the Kalman filter and translated slip angles will be assisted by the IMU connection. This results in a cleaner and lever arm corrected slip angle and translated slip angle parameter set. For this reason we would recommend IMU Kalman filter for slip angle measurement applications.

Note: If True Heading drops out, no Slip Angle calculations will be made.

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