In-vehicle determination of the relative center of gravity height
Relative center of gravity height in a motor vehicle changes from a nominal value to an actual value depending upon vehicle loading. Method and apparatus for determining actual relative center of gravity height are disclosed.
1. Method for determining relative CG height in a vehicle, comprising:
monitoring a nominal relative CG height value;
sensing vehicle roll;
determining a plurality of CG height candidates at a plurality of instances based upon vehicle dynamics data collected during the vehicle roll; and
estimating relative CG height based on the nominal relative CG height value and selective updates based upon the plurality of CG height candidates.
2. The method of claim 1 , wherein the estimating relative CG height based on the nominal relative CG height value and selective updates based upon the plurality of CG height candidates comprises:
initially setting the relative CG height to the nominal relative CG height value; and
iteratively comparing and selectively updating the relative CG height to each of the plurality of CG height candidates.
3. The method of claim 2 , wherein the selectively updating the relative CG height comprises:
comparing the CG height candidate to the relative CG height; and
qualifying the CG height candidate to update the relative CG height based upon the CG height candidate falling within a searching range of the relative CG height.
4. The method of claim 2 , wherein the selectively updating the relative CG height comprises a priori application of a Kalman filter to qualify each of the plurality of CG height candidates to update the relative CG height.
5. The method of claim 1 , further comprising:
resetting the relative CG height to the nominal relative CG height value based upon an indication of vehicle load change; and
wherein the sensing of vehicle roll is initiated upon the resetting.
6. The method for determining relative CG height in a vehicle, as claimed in claim 1 wherein sensing vehicle roll comprises sensing vehicle roll within a predetermined range.
7. The method for determining relative CG height in a vehicle as claimed in claim 1 wherein said nominal relative CG height value comprises a calibration.
8. The method for determining relative CG height in a vehicle as claimed in claim 1 wherein said nominal relative CG height value comprises a previously determined relative CG height.
9. The method for determining relative CG height in a vehicle as claimed in claim 1 wherein said method is performed at least once per ignition cycle of the vehicle.
10. The method of claim 1 , wherein the sensed vehicle roll comprises measurements from yaw and roll gyros.
11. Method for determining relative CG height in a vehicle, comprising:
monitoring a vehicle dynamics state;
monitoring an initial value of relative CG height estimate;
monitoring an initial state of relative CG height;
determining a plurality of CG height candidates based on the initial value of relative CG height estimate, the initial state of relative CG height, and an initial searching range parameter for CG height candidates;
estimating a vehicle dynamic state corresponding to the CG height candidates;
determining innovations of each vehicle dynamics state estimate with respect to the sensed vehicle dynamics state;
updating the value of relative CG height estimate with one of the CG height candidates corresponding to a lowest innovation of the determined innovation among all CG height candidates;
reducing the searching range parameter for CG height candidates; and
updating the state of relative CG height based on the initial state of relative CG height and the updated value of relative CG height estimate.
12. The method of claim 11 , wherein the vehicle dynamics state comprises at least one of vehicle roll rate and vehicle yaw rate.
13. The method of claim 11 , wherein the initial value of relative CG height estimate comprises a calibration.
14. The method of claim 11 , wherein the initial state of relative CG height comprises a calibration.
15. The method of claim 11 , wherein the vehicle dynamics state is estimated based on a Kalman filtering process.
16. The method of claim 11 , wherein the state of relative CG height is updated iteratively through a plurality of instances.
17. The method of claim 11 , wherein the initial value of relative CG height estimate is the value of relative CG height estimate determined in a previous estimation cycle.
18. The method of claim 11 , wherein the initial state of relative CG height is the state of relative CG height determined in a previous estimation cycle.
19. Apparatus for determining relative CG height in a vehicle, comprising:
a plurality of vehicle dynamics sensors adapted to provide vehicle dynamics data;
a controller adapted to receive the vehicle dynamics data and including a computer readable storage medium storing computer code adapted for determining relative CG height of the vehicle based on said vehicle dynamics data, said computer code including programming to:
monitor a nominal relative CG height value;
sense vehicle roll;
determine a plurality of CG height candidates at a plurality of instances based upon vehicle dynamics data collected during the vehicle roll; and
estimate relative CG height based on the nominal relative CG height value and selective updates based upon the plurality of CG height candidates.