Vehicle heading change determination using compensated differential wheel speed
First Claim
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1. A method of compensating for differential wheel speed (DWS) heading determination errors in a navigation system for a vehicle, comprising:
- a) calculating a heading change value according to a DWS formula of;
(dL−
dR)/dWT;
where;
dL is distance traveled as derived from a left wheel sensor, dR is distance traveled as derived from a right wheel sensor, and dWT is the wheel track distance between the left wheel and the right wheel; and
b) compensating for wheel radii change induced error in the heading change value according to the DWS formula by factoring in lateral acceleration, distance through a turn, and a vehicle constant for the course of the vehicle during the heading change.
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Abstract
A vehicle positioning application in a navigation system provides for determining a change of vehicle heading using differential wheel speed sensors and compensates for dynamic and static changes in the wheel radii.
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Citations
15 Claims
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1. A method of compensating for differential wheel speed (DWS) heading determination errors in a navigation system for a vehicle, comprising:
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a) calculating a heading change value according to a DWS formula of;
(dL−
dR)/dWT;
where;
dL is distance traveled as derived from a left wheel sensor, dR is distance traveled as derived from a right wheel sensor, and dWT is the wheel track distance between the left wheel and the right wheel; and
b) compensating for wheel radii change induced error in the heading change value according to the DWS formula by factoring in lateral acceleration, distance through a turn, and a vehicle constant for the course of the vehicle during the heading change. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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3. The method according to claim 2 further comprising:
- recalculating the vehicle constant after each detected turn.
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4. The method according to claim 3 further comprising:
updating the vehicle constant at each detected turn by the formula;
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5. The method according to claim 4 further comprising:
- deriving an estimated lateral acceleration by multiplying yaw rate times speed through the turn.
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6. The method according to claim 5 wherein the yaw rate is determined by the heading change and vehicle speed as derived from wheel speed sensor data.
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7. The method according to claim 1 further comprising:
- detecting that the vehicle has made a turn to trigger the compensating for wheel radii change induced error in the heading change value.
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8. A method of compensating for differential wheel speed heading determination errors in a vehicle navigation system, comprising:
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a) instituting a long term, low weighted correction algorithm for a first heading change value; and
b) correcting the long term, low weighted correction algorithm with a short term, high weighted correction value derived from an inter-wheel differential radius measurement sample between a left wheel and right wheel opposing wheel pair;
wherein said short term, high weighted correction value is derived according to the formula;
dr=rL−
rR;
where;
dr is the inter-wheel radius differential value, rL is the left wheel radius and rR is the right wheel radius, andcalculating an updated, or new, inter-wheel radius differential value, drnew, according to;
drnew=Average (dr);
where;
the average is based on a number of samples,and further adjusting each of the left and right radii by a selected weight whereby, rLnew=rL−
(dr(new)−
dr(old))/selected weight, andrRnew=rR+(dr(new)−
dr(old))/selected weight.- View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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Specification