Vehicle operating parameter determination system and method

• US 20040024565A1
• Filed: 07/10/2003
• Published: 02/05/2004
• Est. Priority Date: 08/05/2002
• Status: Active Grant

• Current Assignee: Robert Bosch Corporation (Robert Bosch GmbH)
• Original Assignee: Robert Bosch Corporation (Robert Bosch GmbH)
• Inventors: Yu, Jingsheng, Breuninger, Christian
• Granted Patent: US 6,816,799 B2
• Time in Patent Office: Days
• US Class Current: 702/151
• CPC Class Codes: B60G 17/0182 involving parameter estimation, e.g. observer, Kalman filter
• CPC Class Codes: B60G 17/0185 for failure detection
• CPC Class Codes: B60G 17/0195 characterised by the regulation being combined with other vehicle control systems conjoint control of vehicle sub-units including control of suspension systems B60W10/22
• CPC Class Codes: B60G 2400/0523 Yaw rate
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2600/082 Sensor drift
• CPC Class Codes: B60G 2600/1871 Optimal control; Kalman Filters
• CPC Class Codes: B60G 2600/1872 Observer; Luaponov function
• CPC Class Codes: B60G 2600/60 Signal noise suppression; Electronic filtering means
• CPC Class Codes: B60G 2800/016 Yawing condition
• 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: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• CPC Class Codes: B60W 2050/0022 Gains, weighting coefficients or weighting functions
• CPC Class Codes: B60W 2050/0031 Mathematical model of the vehicle
• CPC Class Codes: B60W 2050/0052 Filtering, filters
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2520/20 Sideslip angle
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 40/103 : Side slip angle of vehicle body
• CPC Class Codes: B62D 15/0245 : Means or methods for determination of the central position of the steering system, e.g. straight ahead position
• CPC Class Codes: G05B 13/04 : involving the use of models or simulators
• CPC Class Codes: G05B 17/02 : electric

Abstract

A system and method for estimating an operating parameter of a vehicle such as the steering angle offset or body slip angle. The method includes providing a dynamic vehicle model which is valid when the yaw rate and slip angle of the vehicle are either constant or changing. The vehicle model is reformulated to allow for the direct estimation of the steering angle offset value and/or the body slip angle. Estimation of an operating parameter of the vehicle may also include the use of a model difference term which is defined by the difference between a value estimated using the model and a measured value. A method for filtering the steering angle offset value is also provided. The filtering method may utilize a variable filter coefficient which varies in response to changes in the dynamic behavior of the vehicle.

Claims

1. A method of estimating a steering angle offset value in a vehicle having a relative position steering angle sensor, said method comprising:

providing a mathematical expression for calculating an estimated steering angle offset value, {circumflex over (δ

)}_off, based upon at least one measured value of a vehicle operating parameter wherein said mathematical expression is definable by;

selecting a mathematical model to describe the dynamic behavior of the vehicle which includes a first variable, δ

, representing the steering angle of the vehicle; and

substituting, for said first variable, δ

, the sum of a second variable, δ

_Uncenter, representing the relative steering angle position and a third variable, δ

_off, representing the steering angle offset in said model to provide said mathematical expression;

obtaining said at least one measured value for said vehicle; and

estimating said steering angle offset value using said at least one measured value and said mathematical expression.

2. The method of claim 1 wherein said third variable is a state variable with respect to said mathematical expression.

3. The method of claim 1 wherein said at least one measured value includes the yaw rate of the vehicle.

4. The method of claim 1 wherein said at least one measured value includes the yaw rate of the vehicle and the relative steering angle position.

5. The method of claim 1 wherein said at least one measured value includes the yaw rate of the vehicle, the relative steering angle position and the longitudinal velocity of the vehicle.

6. The method of claim 1 further comprising the estimation of the body slip angle of the vehicle using said at least one measured value and said mathematical expression.

7. The method of claim 1 wherein said model comprises:

8. The method of claim 7 wherein said step of substituting the sum of said second and third variables in said model provides a mathematical expression which states:

9. The method of claim 8 wherein said step of substituting the sum of said second and third variables further comprises reformulating said model after substituting said sum, said step of reformulating said model provides a mathematical expression which comprises:

x(k+1)=A(k)x(k)+b(k)·

u(k)+v(k)

y(k)=c^Tx(k)+w(k)

wherein;

k represents a time index,

$A=\left[\begin{array}{ccc}{a}_{11}& a_{12}& b_1\\ a_{21}& a_{22}& b_2\\ 0& 0& 0\end{array}\right],$x^T=[β

{dot over (ψ

)}δ

_Off], $b=\left[\begin{array}{c}{b}_1\\ b_2\\ 0\end{array}\right],$u=δ

_Uncenter,

v(k) represents the process noise,

w(k) represents the measurement noise, and

c^T=[010].

10. The method of claim 1 wherein said step of estimating said steering angle offset value includes use of the mathematical expression which comprises:

{circumflex over (x)}(k+1)=A(k){circumflex over (x)}(k)+b(k)·

u(k)+K(k)(y−

{dot over (y)}) y(k)=c^Tx(k)

wherein

{circumflex over (x)}(k)=[{circumflex over (β

)}{circumflex over (ψ

)}{circumflex over (δ

)}_Off]^T;

{circumflex over (β

)} represents the estimated value of the body slip angle;

{dot over ({circumflex over (ψ

)})} represents the estimated value of the yaw rate;

{circumflex over (δ

)}_off represents the estimated value of the steering angle offset;

K(k) represents a gain matrix.

11. The method of claim 1 further comprising the steps of:

estimating a plurality of steering angle offset values; and

filtering said plurality of estimated steering angle offset values.

12. The method of claim 10 wherein said filtering step comprises using a variable filter coefficient, F_k.

13. The method of claim 11 wherein said variable filter coefficient is calculated using an uncertainty factor, U_k, said uncertainty factor, U_k, being determined using at least one value from the group including the yaw rate of the vehicle, the estimated steering angle position and the lateral acceleration of the vehicle.

14. The method of claim 12 wherein said uncertainty factor, U_k, is determined using the following equation:

U_k=c_ψ

({dot over (ψ

)}·

∫

{dot over (ψ

)}dt)+c_δ

·

|δ

_uncenter+{circumflex over (δ

)}_off|+c_ya_y−

â

_y|,

wherein;

δ

_Uncenter represents the uncorrected relative steering angle position;

{circumflex over (δ

)}_off represents the estimated steering angle offset;

δ

_Uncenter+{circumflex over (δ

)}_off represents the estimated steering angle position;

{dot over (ψ

)} represents the yaw rate of the vehicle;

a_y represents the lateral acceleration of the vehicle; and

c_P, c_δ

, and c_y represent constants.

15. A method of controlling a vehicle, said method comprising:

providing a mathematical expression for estimating first and second vehicle operating parameters wherein said mathematical expression is definable by;

selecting a mathematical model to describe the dynamic behavior of the vehicle;

reformulating said model to provide said mathematical expression wherein said mathematical expression includes a model difference term dependent upon a difference between an estimated value of said second vehicle operating parameter and a measured value of said second vehicle operating parameter;

obtaining a signal representing a measured value of said second vehicle operating parameter;

estimating said first vehicle operating parameter using said mathematical expression wherein calculation of an estimated value for said first parameter includes using said measured value represented by said signal in said model difference term; and

outputting said estimated value for use in an electronic control system for said vehicle.

16. The method of claim 15 wherein said first and second parameters are selected from the group including the steering angle offset, the yaw rate and the body slip angle of the vehicle.

17. The method of claim 15 wherein said first parameter is the steering angle offset and said second parameter is the yaw rate of the vehicle.

18. The method of claim 17 wherein said mathematical expression comprises:

{circumflex over (x)}(k+1)=A(k){circumflex over (x)}(k)+b(k)·

u(k)+K(k)(y−

ŷ

) ŷ

(k)=c^T{circumflex over (x)}(k)

wherein

k represents a time index,

$A=\left[\begin{array}{ccc}{a}_{11}& a_{12}& b_1\\ a_{21}& a_{22}& b_2\\ 0& 0& 0\end{array}\right],<br><br>b=\left[\begin{array}{c}{b}_1\\ b_2\\ 0\end{array}\right],$u=δ

_Uncenter, {circumflex over (x)}(k)=[{circumflex over (β

)}{dot over ({circumflex over (ψ

)})}{circumflex over (δ

)}_Off]^T;

{circumflex over (β

)} represents the estimated value of the body slip angle;

{dot over ({circumflex over (ψ

)})} represents the estimated value of the yaw rate;

{circumflex over (δ

)}_off represents the estimated value of the steering angle offset;

K(k) represents a gain matrix;

(y−

ŷ

) represents said model difference term;

c^T represents an output vector.

19. A method of filtering a plurality of time indexed values in a process for determining a steering angle position of a vehicle having a relative position steering angle sensor, said method comprising:

estimating a plurality of time indexed steering angle offset values;

filtering a plurality of time indexed values which are a function of said plurality of time indexed steering angle offset values using a variable filter coefficient, F_k, said variable filter coefficient, F_k, being determined using an uncertainty factor, U_k, said uncertainty factor, U_k, being determined using at least one value from the group including the yaw rate of the vehicle, the estimated steering angle position and the lateral acceleration of the vehicle.

20. The method of claim 19 wherein said plurality of time indexed values is identical to said plurality of time indexed steering angle offset values.

21. The method of claim 19 wherein said uncertainty factor, U_k, is determined using the following equation:

U_k=c_ψ

({dot over (ψ

)}·

∫

{dot over (ψ

)}dt)+c_δ

·

|δ

_uncenter+{circumflex over (δ

)}_off|+c_y|a_y−

â

_y|,

wherein;

δ

_Uncenter represents the uncorrected relative steering angle position;

{circumflex over (δ

)}_off represents the estimated steering angle offset;

δ

_Uncenter+{circumflex over (δ

)}_off represents the estimated steering angle position;

{dot over (ψ

)}represents the yaw rate of the vehicle;

a_y represents the lateral acceleration of the vehicle; and

c_P, c_δ

, and c_y represent constants.

22. The method of claim 21 wherein said filtering step comprises the use of the formula:

δ

_Off,k+1=δ

_Off,k+Fk·

({circumflex over (δ

)}_Off−

δ

_Off,k)

wherein;

k represents the time index; and

the filter coefficient, F_k, is defined as;

F_k=T(1−

Q_k)

wherein;

Q_k+1=Q_k+T·

(1−

Q_k)

and T is defined as;

T=c₀(1−

U_kQ_k)

wherein;

c_o represents a constant.