Method for road grade/vehicle pitch estimation

• US 20030130778A1
• Filed: 01/07/2002
• Published: 07/10/2003
• Est. Priority Date: 01/07/2002
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Brown, Todd Allen, Tseng, Hongtei Eric, Hrovat, Davorin David
• Granted Patent: US 6,714,851 B2
• Time in Patent Office: Days
• US Class Current: 701/45
• CPC Class Codes: B60G 2400/0512 Pitch angle
• CPC Class Codes: B60G 2400/0521 Roll rate
• CPC Class Codes: B60G 2400/0523 Yaw rate
• CPC Class Codes: B60G 2400/104 lateral or transversal with regard to vehicle
• CPC Class Codes: B60G 2400/106 longitudinal with regard to vehicle, e.g. braking
• CPC Class Codes: B60G 2400/208 of wheel rotation
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2400/412 of steering wheel or column
• CPC Class Codes: B60G 2600/044 Alarm means
• CPC Class Codes: B60G 2600/124 Error signal
• CPC Class Codes: B60G 2800/014 Pitch; Nose dive
• CPC Class Codes: B60G 2800/0192 longitudinal with regard to vehicle
• CPC Class Codes: B60G 2800/212 Transversal; Side-slip during cornering
• CPC Class Codes: B60G 2800/702 Improving accuracy of a sensor signal
• CPC Class Codes: B60G 2800/9124 Roll-over protection systems, e.g. for warning or control
• CPC Class Codes: B60R 16/0233 Vehicle tilting, overturning or roll over
• CPC Class Codes: B60R 2021/01184 Fault detection or diagnostic circuits in power circuits B60R2021/01129
• CPC Class Codes: B60R 2021/01306 monitoring vehicle inclination
• CPC Class Codes: B60R 2021/01327 Angular velocity or angular acceleration
• CPC Class Codes: B60R 21/0132 responsive to vehicle motion parameters , e.g. to vehicle longitudinal or transversal deceleration or speed value
• CPC Class Codes: B60T 2250/06 : Sensor zero-point adjustment; Offset compensation
• CPC Class Codes: B60T 8/172 : Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: B60W 2050/0021 : Differentiating means
• CPC Class Codes: B60W 2520/10 : Longitudinal speed
• CPC Class Codes: B60W 2520/105 : Longitudinal acceleration
• CPC Class Codes: B60W 2520/14 : Yaw
• CPC Class Codes: B60W 2520/16 : Pitch
• CPC Class Codes: B60W 2552/15 : Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 30/1819 : Propulsion control with control means using analogue circuits, relays or mechanical links
• CPC Class Codes: B60W 40/109 : Lateral acceleration
• CPC Class Codes: B60W 40/11 : Pitch movement
• CPC Class Codes: B60W 40/112 : Roll movement
• CPC Class Codes: B60W 40/114 : Yaw movement
• CPC Class Codes: B62D 7/159 : characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A control system (13) for an automotive vehicle (10) includes a longitudinal accelerometer (24) that generates a longitudinal acceleration signal corresponding to a longitudinal acceleration of a center of gravity (COG) of the vehicle body. A lateral velocity sensor (22) generates a lateral velocity signal corresponding to the lateral velocity of the vehicle body. A controller (14) is coupled to the yaw rate sensor (18), the longitudinal accelerometer (24) and the lateral velocity sensor (22). The controller (14) determines a longitudinal speed from the longitudinal acceleration signal. The controller determines a vehicle pitch angle in response to the longitudinal speed, the yaw rate signal and the lateral velocity signal.

Claims

1. A method of detecting a vehicle pitch angle for use in stability control system for a motor vehicle, said method comprising the steps of:

generating a longitudinal speed signal corresponding to a longitudinal speed of the vehicle;

generating a longitudinal acceleration signal corresponding to a longitudinal acceleration of the vehicle;

generating a derivative signal corresponding to a derivative of said longitudinal speed;

generating a yaw rate signal corresponding to vehicle yaw rate;

generating a lateral velocity signal corresponding to the lateral velocity of the vehicle; and

determining a vehicle pitch angle based in response to said derivative signal, said yaw rate signal and said lateral velocity signal.

2. A method as recited in claim 1 wherein said step of determining a vehicle pitch angle is performed in accordance with the equation

{dot over (u)}=a_x+rv−

g sin θ

where u is a longitudinal speed and {dot over (u)} is the derivative of the longitudinal speed u,

a_x is the longitudinal acceleration, r is the yaw rate, v is the lateral velocity; and

θ

, the vehicle pitch/road grade angle.

3. A method as recited in claim 1 further comprising the step of controlling a safety device in response to said pitch angle.

4. A method of detecting vehicle pitch angle as described in claim 1, further comprising:

determining a pitch estimation error in response to a pre-calibrated function in response to steering wheel angle, vehicle speed, yaw rate and lateral acceleration).

5. A method of detecting vehicle pitch angle as described in claim 1, wherein determining said pitch estimation comprises determining said pitch estimation error in response to the expression (a_y/g)·

(v_n/u) where;

u is a longitudinal speed and,

a_x is the longitudinal acceleration, v_n is a lateral velocity estimation error; and

θ

is the vehicle pitch/road grade angle.

6. A method of detecting vehicle pitch angle as recited in claim 5, wherein a pitch estimation bound is determined by the equation (a_y/g)·

(v_n/u).

7. A method of detecting a road grade/vehicle pitch angle as described in claim 1, determining an estimated lateral velocity in response to a lateral velocity observer.

8. A method of detecting a road grade/vehicle pitch angle as described in claim 7, wherein said step of determining an estimated lateral velocity in response to a lateral velocity observer comprises determining an estimated lateral velocity in response to a vehicle speed, steering wheel angle, said yaw rate and said lateral acceleration.

9. A method of detecting a road grade/vehicle pitch angle as described in claim 1, wherein said step of determining an estimated lateral velocity comprises determining a lateral velocity estimation error.

10. A method of detecting a road grade/vehicle pitch angle as described in claim 1, further comprising the steps of calibrating said longitudinal acceleration signal, yaw rate signal, said lateral velocity signal.

11. A method of detecting a road grade/vehicle pitch angle as described in claim 1, wherein the step of calibrating comprises during a steady state, generating an adjustment signal.

12. A method of detecting a road grade/vehicle pitch angle as described in claim 1, wherein the step of deriving an adjustment signal comprises deriving an adjustment signal in response to θ

where

tan θ

≈

−

ω

_x/ω

_z

where □

is the total vehicle roll angle and □

is the vehicle (inertial) pitch angle.

13. A method of calibrating sensor pitch alignment for an automotive vehicle, said method comprising the steps of

generating a yaw rate signal corresponding to vehicle yaw rate;

generating a roll rate signal corresponding to vehicle roll rate;

generating a lateral acceleration signal corresponding to vehicle lateral acceleration;

determining when the vehicle is operating in a steady state turning condition; and

generating a pitch angle e when the vehicle is in the steady state turning condition where;

0≈

ω

_x+tan θ

·

ω

_z

where ω

_x and ω

_z, are said roll rate and yaw rate.

14. A control system for an automotive vehicle having a vehicle body comprising:

a yaw rate sensor generating a yaw motion signal corresponding to a yaw motion of the vehicle body;

a longitudinal accelerometer generating a longitudinal acceleration signal corresponding to a longitudinal acceleration of a center of gravity of the vehicle body;

a lateral velocity sensor generating a lateral velocity signal corresponding to the lateral velocity of the vehicle body; and

a controller coupled to said yaw rate sensor, said longitudinal accelerometer and said lateral velocity sensor, said controller determining a longitudinal speed from said longitudinal acceleration signal, said controller determining a vehicle pitch angle in response to said longitudinal speed, said yaw rate signal and said lateral velocity signal.

15. A control system as recited in claim 14, further comprising a safety system coupled to said controller, said controller generating a control signal to said safety system in response to said roll attitude angle, said pitch attitude angle and said yaw attitude angle.

16. A control system as recited in claim 15, wherein said safety system comprises an active brake control system.

17. A control system as recited in claim 15, wherein said safety system comprises an active rear steering system.

18. A control system as recited in claim 15, wherein said safety system comprises an active front steering system.

19. A control system as recited in claim 15, wherein said safety system comprises an active anti-roll bar system.

20. A control system as recited in claim 15, wherein said safety system comprises an active suspension system.