GPS assisted vehicular longitudinal velocity determination

• US 20080306687A1
• Filed: 06/05/2007
• Published: 12/11/2008
• Est. Priority Date: 06/05/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Ryu, Jihan, Chen, Cheng-Foo
• Granted Patent: US 8,095,309 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01C 21/10 by using measurements of speed or acceleration G01C21/24, G01C21/26 take precedence

Abstract

A vehicle includes a GPS system and a longitudinal accelerometer. Accelerometer corrections are derived based on GPS velocity data. Individual wheel speeds are determined based on GPS velocity data. Longitudinal vehicle velocity may be determined based on accelerometer data or individual wheel speeds.

Claims

1. Method for determining longitudinal acceleration of a vehicle equipped with a longitudinal accelerometer and a global positioning system (GPS), comprising:

measuring a signal from the longitudinal accelerometer;

determining a sensitivity and bias of the longitudinal accelerometer using a measure of vehicle longitudinal velocity provided by the GPS, a measure of vehicle lateral velocity, and a measure of vehicle yaw rate; and

determining longitudinal acceleration of the vehicle by applying the sensitivity and bias to the measured signal from the longitudinal accelerometer.

2. The method as claimed in claim 1 further comprising:

calculating longitudinal and lateral velocity at the vehicle center of gravity (CG) using GPS velocity and vehicle yaw rate;

calculating individual wheel longitudinal and lateral velocities from the longitudinal and lateral velocity at the vehicle CG and wheel distribution relative to the vehicle CG; and

calculating individual wheel speeds using the individual wheel longitudinal and lateral velocities and steering angles.

3. The method as claimed in claim 2 further comprising:

calculating individual wheel rolling radii using individual wheel rotational speeds and the individual wheel speeds.

4. The method as claimed in claim 1 further comprising:

determining an estimated vehicle longitudinal velocity by integrating the longitudinal acceleration.

5. The method as claimed in claim 2 further comprising:

determining an estimated vehicle longitudinal velocity from the individual wheel speeds.

6. The method as claimed in claim 5 further comprising:

selectively determining the estimated vehicle longitudinal velocity from one of a maximum one of the individual wheel speeds, a minimum one of the individual wheel speeds, and an average of the individual wheel speeds corresponding to un-driven ones of the individual wheels.

7. The method as claimed in claim 2 further comprising:

determining a first estimated vehicle longitudinal velocity by integrating the longitudinal acceleration;

determining a second estimated vehicle longitudinal velocity from the individual wheel speeds; and

determining the vehicle longitudinal velocity as one of the first and second estimated vehicle longitudinal velocities.

12. The method of claim 1 further comprising:

calculating a rolling radius of the wheel using the calculated wheel speed and a rotational speed of the wheel.

8. Method of using a vehicle dynamics control system in a vehicle having a longitudinal accelerometer, a global positioning system (GPS) and a plurality of wheels, comprising:

receiving longitudinal acceleration data from the longitudinal accelerometer;

receiving GPS velocity data from the GPS; and

using GPS velocity data in determining corrections for the longitudinal acceleration data and in determining vehicle velocity.

9. The method of claim 8, further comprising:

calculating longitudinal velocities at all of the plurality of wheels using GPS velocity data if neither an ABS or a TCS is active and if an absolute value of a longitudinal acceleration of the vehicle is less than a vehicle independent threshold for longitudinal acceleration; and

calculating longitudinal velocities only at un-driven ones of the plurality wheels using GPS velocity data if neither an ABS or a TCS is active and if longitudinal acceleration of the vehicle is positive and not less than the vehicle threshold for longitudinal acceleration.

13. The method of claim 8, further comprising:

determining a bias and a sensitivity error each associated with a longitudinal accelerometer.

14. The method of claim 13, further comprising:

obtaining data including longitudinal acceleration, GPS velocity, and yaw rate from a plurality of associated sensors;

storing the obtained data in a buffer if lateral velocity of the GPS velocity is available; and

estimating bias and sensitivity error of a longitudinal accelerometer if lateral velocity of the GPS velocity is available, and if new GPS velocity data is available once the obtained data is stored in the buffer.

10. The method of 9 wherein calculating longitudinal velocities comprises:

calculating longitudinal and lateral velocities of the vehicle at a center of gravity of the vehicle using GPS velocity data; and

calculating longitudinal and lateral velocities at a wheel using the calculated longitudinal and lateral velocities of the vehicle at a center of gravity of the vehicle;

11. The method of claim 10 further comprising:

calculating a wheel speed of the wheel using the calculated longitudinal and lateral velocities at the wheel.