KINEMATIC ROAD GRADIENT ESTIMATION

• US 20140067154A1
• Filed: 01/07/2013
• Published: 03/06/2014
• Est. Priority Date: 08/31/2012
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Yu, Hai, Lu, Jianbo, Boesch, Mathew Alan, McGee, Ryan Abraham
• Granted Patent: US 9,454,508 B2
• Time in Patent Office: Days
• US Class Current: 701/1
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 40/076 Slope angle of the road
• CPC Class Codes: B60W 40/13 Load or weight
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00

Abstract

A vehicle and a vehicle system are provided with a controller that is configured to generate output indicative of a kinematic road gradient estimation using an extended Kalman filter. The extended Kalman filter includes a system input based on a longitudinal acceleration and an acceleration offset, and a system output based on a predicted vehicle speed. The acceleration offset is based on at least one of a lateral velocity, a lateral offset, and a vehicle pitch angle. The controller is further configured to generate output indicative of a kinematic quality factor corresponding to an availability of the kinematic road gradient estimation.

Claims

1. A vehicle comprising:

a controller configured to;

generate output indicative of a kinematic road gradient estimation using a filter having a system input based on a longitudinal acceleration, and a system output based on a predicted vehicle speed, and

generate output indicative of a kinematic quality factor corresponding to an availability of the kinematic road gradient estimation.

2. The vehicle of claim 1 wherein the controller is further configured to:

estimate a state indicative of an acceleration due to gravity based on a difference between the system output and a measured vehicle speed; and

calculate the kinematic road gradient estimation using a kinematic equation based on the state.

3. The vehicle of claim 1 further comprising:

an inertial sensor for providing a signal indicative of the longitudinal acceleration.

4. The vehicle of claim 1 further comprising:

a navigation system configured to generate output indicative of a measured vertical displacement of the vehicle, wherein the system output further comprises a predicted vertical displacement;

wherein the controller is further configured to;

estimate a first state indicative of an acceleration due to gravity based on a difference between the system output and a measured vehicle speed and a difference between the system output and the measured vertical displacement,

estimate a second state indicative of an acceleration due to a vehicle pitch angle based on a difference between the system output and the measured vehicle speed and a difference between the system output and the measured vertical displacement, and

calculate the kinematic road gradient estimation based on the first state and the second state.

5. The vehicle of claim 1 wherein the controller is further configured to:

lock the output indicative of the kinematic road gradient estimation when a vehicle speed is less than an exit speed threshold.

6. The vehicle of claim 1 wherein the system input further comprises an acceleration offset corresponding to lateral vehicle dynamics.

7. The vehicle of claim 1 wherein the kinematic road gradient estimation is independent of a vehicle pitch angle.

8. A vehicle system comprising:

a controller configured to generate output indicative of a kinematic road gradient estimation using an extended Kalman filter having a system input based on a longitudinal acceleration and an acceleration offset, and a system output based on a predicted vehicle speed;

wherein the acceleration offset is based on at least one of a lateral velocity, a lateral offset, and a vehicle pitch angle.

9. The vehicle system of claim 8 wherein the controller is further configured to:

evaluate a vehicle turning condition based on input indicative of a yaw rate; and

estimate the lateral velocity based on an integration of input indicative of a lateral acceleration when the vehicle turning condition corresponds to a dynamic driving condition.

10. The vehicle system of claim 8 wherein the controller is further configured to:

evaluate a vehicle turning condition based on input indicative of a yaw rate; and

derive the lateral velocity from the yaw rate when the vehicle turning condition corresponds to a steady state condition.

11. The vehicle system of claim 8 wherein the controller is further configured to:

evaluate a vehicle turning condition based on input indicative of a yaw rate;

calculate a body roll angle based on input indicative of a lateral acceleration when the vehicle turning condition corresponds to a dynamic driving condition; and

estimate the lateral offset based on the body roll angle.

12. The vehicle system of claim 8 wherein the controller is further configured to:

evaluate a vehicle turning condition based on input indicative of a yaw rate;

calculate a body roll angle based on the yaw rate when the vehicle turning condition corresponds to a steady state condition; and

estimate the lateral offset based on the body roll angle.

13. The vehicle system of claim 8 wherein the controller is further configured to:

estimate the vehicle pitch angle using a dynamic pitch compensation based on a vehicle speed and the longitudinal acceleration.

14. The vehicle system of claim 8 wherein the controller is further configured to:

estimate a state indicative of an acceleration due to gravity based on a difference between the system output and a measured vehicle speed;

select a general suspension damping effect and a suspension stiffness value from predetermined data based on the state and a derivative of vehicle speed using a phase plane gain scheduling rule; and

calculate the vehicle pitch angle using a transfer function based on the general suspension damping effect and the suspension stiffness value.

15. The vehicle system of claim 8 wherein the controller is further configured to:

calculate the vehicle pitch angle based on a vehicle speed, the longitudinal acceleration and a vertical acceleration.

16. The vehicle system of claim 8 wherein the controller is further configured to:

estimate a state indicative of an acceleration due to gravity based on a difference between the system output and a measured vehicle speed; and

calculate the vehicle pitch angle based on a vehicle speed, the longitudinal acceleration, a vertical acceleration and the acceleration due to gravity.

17. A method for operating a vehicle based on an estimated kinematic road gradient comprising:

generating output indicative of a kinematic road gradient estimation using an extended Kalman filter having a system input based on a longitudinal acceleration, and a system output based on a predicted vehicle speed; and

generating a kinematic quality factor that corresponds to an availability of the kinematic road gradient estimation.

18. The method of claim 17 further comprising:

estimating a state indicative of an acceleration due to gravity based on a difference between the system output and a measured vehicle speed; and

calculating the kinematic road gradient estimation based on the state.

19. The method of claim 17 further comprising:

receiving input indicative of a measured vertical displacement of the vehicle, wherein the system output further comprises a predicted vertical displacement;

estimating a first state indicative of an acceleration due to gravity based on a difference between the system output and a measured vehicle speed and a difference between the system output and the measured vertical displacement;

estimating a second state indicative of an acceleration due to a vehicle pitch angle based on a difference between the system output and the measured vehicle speed and a difference between the system output and the measured vertical displacement; and

calculating the kinematic road gradient estimation based on the first state and the second state.

20. The method of claim 17 further comprising:

receiving input indicative of a yaw rate; and

estimating an acceleration offset based on the yaw rate, wherein the acceleration offset includes at least one of a lateral velocity, a lateral offset, and a vehicle pitch angle;

wherein the system input further comprises the acceleration offset.