Kinematic road gradient estimation

Patent metadata

Field	Value
Publication number	US-9454508-B2
Application number	US-201313735327-A
Country	US
Kind code	B2
Filing date	Jan 7, 2013
Priority date	Aug 31, 2012
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

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.

First claim

What is claimed is:

1. A vehicle comprising:
a navigation system configured to generate output indicative of a measured vertical displacement of the vehicle;
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 a system output based on a predicted vehicle speed, wherein the system output includes a predicted vertical displacement, and
generate output indicative of a kinematic quality factor corresponding to an availability of the kinematic road gradient estimation;
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.

2. The vehicle of claim 1 further comprising: an inertial sensor for providing a signal indicative of the longitudinal acceleration.

3. 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.

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

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

6. A vehicle system comprising:
a controller configured to:
calculate a vehicle pitch angle based on a suspension damping effect and a suspension stiffness value selected using a phase plane gain scheduling rule; and
generate output indicating a kinematic road gradient estimation using an extended Kalman filter having a system input based on a longitudinal acceleration and an acceleration offset based on the vehicle pitch angle, and a system output based on a predicted vehicle speed.

7. The vehicle system of claim 6 wherein the acceleration offset is based on a lateral velocity, a lateral offset and the vehicle pitch angle, and 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.

8. The vehicle system of claim 6 wherein the acceleration offset is based on a lateral velocity, a lateral offset and the vehicle pitch angle, and 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.

9. The vehicle system of claim 6 wherein the acceleration offset is based on a lateral velocity, a lateral offset and the vehicle pitch angle, and 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.

10. The vehicle system of claim 6 wherein the acceleration offset is based on a lateral velocity, a lateral offset and the vehicle pitch angle, and 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.

11. The vehicle system of claim 6 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.

12. The vehicle system of claim 6 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 the suspension damping effect and the suspension stiffness value from predetermined data based on the state and a derivative of vehicle speed using the phase plane gain scheduling rule; and
calculate the vehicle pitch angle using a transfer function based on the suspension damping effect and the suspension stiffness value.

13. The vehicle system of claim 6 wherein the controller is further configured to:
calculate the vehicle pitch angle based on a vehicle speed, the longitudinal acceleration and a vertical acceleration.

14. The vehicle system of claim 6 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.

15. A method for operating a vehicle based on an estimated kinematic road gradient comprising:
receiving input indicative of a measured vertical displacement of the vehicle;
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, wherein the system output comprises a predicted vertical displacement;
generating a kinematic quality factor that corresponds to an availability of the kinematic road gradient estimation;
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.

16. The method of claim 15 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 the vehicle pitch angle;
wherein the system input further comprises the acceleration offset.

Assignees

• Ford Global Tech Llc

Inventors

• Yu Hai
• Lu Jianbo
• Boesch Mathew Alan
• Mcgee Ryan Abraham

Classifications

• B60W40/13

  Load or weight · CPC title

• B60W2520/105

  Longitudinal acceleration · CPC title

• B60W2520/10

  Longitudinal speed · CPC title

• B60W2520/16

  Pitch · CPC title

• B60W40/076 Primary

  Slope angle of the road · CPC title