METHOD AND SYSTEM FOR RECOGNIZING THE SIGN OF THE VELOCITY OF A VEHICLE AND FOR ESTIMATING THE ROAD SLOPE

• US 20070083314A1
• Filed: 09/13/2006
• Published: 04/12/2007
• Est. Priority Date: 09/14/2005
• Status: Active Grant

• Current Assignee: C.R.F. Societa Consortile Per Azioni
• Original Assignee: C.R.F. Societa Consortile Per Azioni
• Inventors: CORIGLIANO, Emanuel, Borodani, Pandeli
• Granted Patent: US 7,269,494 B2
• Time in Patent Office: Days
• US Class Current: 701/80
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 40/072 Curvature of the road
• CPC Class Codes: B60W 40/076 Slope angle of the road
• CPC Class Codes: G01C 9/00 Measuring inclination, e.g. by clinometers, by levels
• CPC Class Codes: G01P 13/04 Indicating positive or negative direction of a linear movement or clockwise or anti-clockwise direction of a rotational movement

Abstract

A method of estimating the slope of a road surface on which is positioned a motor vehicle provided with a velocity sensor for measuring the modulus of the velocity of the vehicle and with an accelerometer for measuring the acceleration in the longitudinal direction of the vehicle comprises the following operations: a) providing a signal indicating the measurement of the velocity of the vehicle (V1) by means of the velocity sensor; b) providing a signal indicating the measurement of the acceleration in the longitudinal direction of the vehicle (AxVehFilV) by means of the accelerometer; c) processing the velocity measurement signal (V1) and the acceleration measurement signal (AxVehFilV) by means of a mathematical model based on the relation A_x={dot over (ν)}+g sin α, where A_x represents the measurement of acceleration in the longitudinal direction of the vehicle, {dot over (ν)} indicates the component of longitudinal acceleration of the vehicle along the road surface, g is the gravitational acceleration, and α represents the angle of inclination of the road surface, in such a way as to determine an estimated value of the slope of the road surface (StimaPend); d) processing the velocity measurement signal (V1), the acceleration measurement signal (AxVehFilV) and the estimated value of the slope (StimaPend) in such a way as to determine the sign of the velocity of the vehicle (Segno); and e) repeating operations a) to d) recursively according to a predetermined rule, in which the sign of the velocity (Segno) determined in operation d) of a specific recursive step is used as an additional input for operation c) of the successive recursive step to correct the estimated value of the slope (StimaPend).

Claims

1. Method of estimating the slope of a road on which there is positioned a motor vehicle provided with rotational velocity sensor means for measuring the modulus of the velocity of the vehicle and with acceleration measuring means for measuring the acceleration in the longitudinal direction of the vehicle, characterized in that it comprises the following operations:

a) providing a signal indicating the measurement of the velocity of the vehicle (V1, NCltFilV) by means of the said velocity sensor means;

b) providing a signal indicating the measurement of the acceleration in the longitudinal direction of the vehicle (AxVehFilV) by means of the said acceleration measuring means;

c) determining an estimated value of the slope of the road (StimaPend), the said determination of the estimated value comprising, subject to a condition of enabling the estimation, the processing of the velocity measurement signal (V1) and of the acceleration measurement signal (AxVehFilV) by means of a mathematical model based on the relation

A_x={dot over (ν

)}+g sin α

,

where A_x represents the measurement of acceleration in the longitudinal direction of the vehicle, {dot over (ν

)} indicates the component of longitudinal acceleration of the vehicle along the road, g is the gravitational acceleration and a represents the angle of inclination of the road profile;

d) processing the velocity measurement signal (V1, NCltFilV), the acceleration measurement signal (AxVehFilV) and the estimated value of the slope (StimaPend) in such a way as to determine the sign of the velocity of the vehicle (Segno); and

e) repeating operations a) to d) recursively according to a predetermined rule, in which the sign of the velocity (Segno) determined in operation d) of a specific recursive step is used as an additional input for operation c) of a successive recursive step to update the estimated value of the slope of the road (StimaPend).

2. Method according to claim 1, in which the said velocity sensor means comprise wheel sensor means, capable of providing a signal indicating the measurement of the angular velocity of at least one wheel of the motor vehicle, and sensor means of the gearbox primary, capable of providing a signal indicating the measurement of the angular velocity of the primary shaft of the gearbox of the motor vehicle, and in the said operation a) the signal indicating the measurement of the velocity of the vehicle (V1, NCltFilV) is selectively determined, according to the conditions of motion of the motor vehicle, on the basis of the signal indicating the measurement of the wheel sensor means or of the sensor means of the gearbox primary of the motor vehicle.

3. Method according to claim 1, in which the processing of operation c) is implemented by means of a Kalman filter (20) having the form

{circumflex over (x)}(k)=A_d·

{circumflex over (x)}(k−

1)+B_d·

u_d(k−

1)
ŷ

(k−

1)=C_d·

{circumflex over (x)}(k−

1)

where A_d, B_d and C_d are transfer matrices;

k indicates the sampling instant;

u_d is a vector whose first element is the measurement of the velocity of the vehicle corrected with the sign information and whose second element is the measurement of longitudinal acceleration;

{circumflex over (x)} is an estimated state vector, one component of which is a function of the angle of inclination α

of the road.

4. Method according to claim 1, in which operation d) comprises:

storing an initial estimated value α

(t₀) of the angle of inclination of the road, where the instant t₀ represents the moment at which the start of the vehicle'"'"'s movement is detected, in a condition in which the vehicle is not in neutral, or in which the estimated value of the slope which is a function of the said initial value α

(t₀) is greater than a predetermined threshold,

calculating the velocity of the vehicle by integrating the relation {dot over (ν

)}=A_x−

g sin α

the estimated sign of the velocity corresponding to the sign of the variable found by the integration, when the modulus of the said variable exceeds a certain predetermined threshold.

5. Method according to claim 1, in which operation d) comprises the following phases:

storing an initial estimated value α

(t₀) of the angle of inclination of the road, where the instant t₀ represents the moment at which the start of the vehicle'"'"'s movement is detected,

in a condition in which the vehicle is not in neutral, or in which the estimated value of the slope which is a function of the said initial value α

(t₀) is greater than a predetermined threshold, calculating angular velocities O<sub>r—

calcP</sub> and O<sub>r—

calcN</sub>, defined by the following relations;

$\begin{array}{c}{O}_{\mathrm{r\_calcP}}=O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)+\frac{1}{R}<br><br>{\int <br><br>}_0^t<br><br>\left(A_x-g<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}<br><br>\left(t_0\right)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,\\ O_{\mathrm{r\_calcN}}=-O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)+\frac{1}{R}<br><br>{\int <br><br>}_0^t<br><br>\left(A_x-g<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}<br><br>\left(t_0\right)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,\end{array}$

where O<sub>r—

proc</sub> represents the measured modulus of the angular velocity of at least one wheel of the vehicle,

calculating a pair of variables ResP and ResN, defined by the following relations;

ResP=O<sub>r—

proc</sub>−

O<sub>r—

calcP</sub>,
ResN=−

O<sub>r—

proc</sub>−

O<sub>r—

calcN</sub>,

estimating the sign of the velocity (Segno) by comparing the said variables ResP and ResN.

6. Method according to claim 1, in which operation d) comprises the following phases:

storing an initial estimated value α

(t₀) of the angle of inclination of the road, where the instant t₀ represents the moment at which the start of the vehicle'"'"'s movement is detected,

in a condition in which the vehicle is not in neutral, or in which the estimated value of the slope which is a function of the said initial value α

(t₀) is greater than a predetermined threshold, calculating angular velocities O<sub>r—

calcP</sub> and O<sub>r—

calcN</sub>, defined by the following relations;

$\begin{array}{c}{O}_{\mathrm{r\_calcP}}<br><br>\text{\hspace{1em}<br><br>}=\text{\hspace{1em}<br><br>}<br><br>O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)<br><br>\text{\hspace{1em}<br><br>}+\text{\hspace{1em}<br><br>}<br><br>{\int <br><br>}_0^t<br><br>\frac{1}{\text{\hspace{1em}<br><br>}<br><br>J_{\mathrm{eq}}}<br><br>\left(C_T-C_R<br><br>\text{\hspace{1em}<br><br>}-\mathrm{Rmg}<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}(\text{\hspace{1em}<br><br>}<br><br>t_0)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,\\ O_{\mathrm{r\_calcN}}<br><br>\text{\hspace{1em}<br><br>}=-O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)<br><br>\text{\hspace{1em}<br><br>}+\text{\hspace{1em}<br><br>}<br><br>{\int <br><br>}_0^t<br><br>\frac{1}{\text{\hspace{1em}<br><br>}<br><br>J_{\mathrm{eq}}}<br><br>\left(C_T-C_R<br><br>\text{\hspace{1em}<br><br>}-\mathrm{Rmg}<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}(\text{\hspace{1em}<br><br>}<br><br>t_0)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,<br><br>\text{\hspace{1em}<br><br>}\end{array}$

where J_eq represents the equivalent inertia of the vehicle based on the wheels;

C_T is the torque transmitted to the wheels;

C_R indicates the resistant torque at the wheels, including the contribution of the brakes, the friction of the tyres and the aerodynamic resistance of the vehicle;

R represents the radius of the wheels;

m is the mass of the vehicle; and

ω

_wheels indicates the mean angular velocity of the non-driving wheels,

calculating a pair of variables ResP and ResN, defined by the following relations;

ResP=O<sub>r—

proc</sub>−

O<sub>r—

calcP</sub>,
ResN=−

O<sub>r—

proc</sub>−

O<sub>r—

calcN</sub>,

estimating the sign of the velocity (Segno) by comparing the said variables ResP and ResN.

7. Method according to claim 5, in which the said comparison of the variables ResP and ResN is carried out when the value of one of the said variables ResP and ResN exceeds a predetermined threshold (SogliaRes).

8. Computer program product which can be loaded into the memory of a computer and which comprises portions of software code for implementing the method according to claim 1, when the product is run on a computer.

9. System for estimating the slope of a road for a motor vehicle, comprising rotational velocity sensor means for measuring the modulus of the velocity of the vehicle and acceleration measuring means for measuring the acceleration in the longitudinal direction of the vehicle, positioned on board the vehicle, and processing means, connected for operation to the said velocity sensor means and to the said acceleration measuring means, and programmed for:

a) receiving a signal indicating the measurement of the velocity of the vehicle (V1, NCltFilV) provided by the said velocity sensor means;

b) receiving a signal indicating the measurement of the acceleration in the longitudinal direction of the vehicle (AxVehFilV) provided by the said acceleration measuring means;

c) determining an estimated value of the slope of the road (StimaPend), the said determination of the estimated value comprising, subject to a condition of enabling the estimation, the processing of the velocity measurement signal and of the acceleration measurement signal by means of a mathematical model based on the relation

A_x={dot over (ν

)}+g sin α

,

where A_x represents the measurement of acceleration in the longitudinal direction of the vehicle, {dot over (ν

)} indicates the component of longitudinal acceleration of the vehicle along the road, g is the gravitational acceleration and α

represents the angle of inclination of the road profile;

d) processing the velocity measurement signal (V1, NCltFilV), the acceleration measurement signal (AxVehFilV) and the estimated value of the slope (StimaPend) in such a way as to determine the sign of the velocity of the vehicle (Segno); and

e) repeating operations a) to d) recursively according to a predetermined rule, in which the sign of the velocity (Segno) determined in operation d) of a specific recursive step is used as an additional input for operation c) of a successive recursive step to update the estimated value of the slope of the road (StimaPend).

10. System according to claim 9, in which the said velocity sensor means comprise wheel sensor means, capable of providing a signal indicating the measurement of the angular velocity of at least one wheel of the motor vehicle, and sensor means of the gearbox primary, capable of providing a signal indicating the measurement of the angular velocity of the primary shaft of the gearbox of the motor vehicle, and in which the said processing means are programmed to selectively determine the signal indicating the measurement of the velocity of the vehicle (V1, NCltFilV), according to the conditions of motion of the motor vehicle, on the basis of the signal indicating the measurement of the wheel sensor means or of the sensor means of the gearbox primary of the motor vehicle.

11. System according to claim 9, in which the said processing means are programmed in such a way as to implement the processing of operation c) by means of a Kalman filter (20) having the form

{circumflex over (x)}(k)=A_d·

{circumflex over (x)}(k−

1)+B_d·

u_d(k−

1)
ŷ

(k−

1)=C_d·

{circumflex over (x)}(k−

1)

where A_d, B_d and C_d are transfer matrices;

k indicates the sampling instant;

u_d is a vector whose first element is the measurement of the velocity of the vehicle corrected with the sign information and whose second element is the measurement of longitudinal acceleration;

{circumflex over (x)} is an estimated state vector, one component of which is a function of the angle of inclination a of the road.

12. System according to claim 9, in which the said processing means are programmed in such a way that operation d) comprises the following phases:

storing an initial estimated value α

(t₀) of the angle of inclination of the road, where the instant t₀ represents the moment at which the start of the vehicle'"'"'s movement is detected,

in a condition in which the vehicle is not in neutral, or in which the estimated value of the slope which is a function of the said initial value α

(t₀) is greater than a predetermined threshold, calculating angular velocities O<sub>r—

calcP</sub> and O<sub>r—

calcN</sub>, defined by the following relations;

$\begin{array}{c}{O}_{\mathrm{r\_calcP}}=O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)+\frac{1}{R}<br><br>{\int <br><br>}_0^t<br><br>\left(A_x-g<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}<br><br>\left(t_0\right)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,\\ O_{\mathrm{r\_calcN}}=-O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)+\frac{1}{R}<br><br>{\int <br><br>}_0^t<br><br>\left(A_x-g<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}<br><br>\left(t_0\right)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,\end{array}$

where O<sub>r—

proc</sub> represents the measured modulus of the angular velocity of at least one wheel of the vehicle,

calculating a pair of variables ResP and ResN, defined by the following relations;

ResP=O<sub>r—

proc</sub>−

O<sub>r—

calP</sub>,
ResN=−

O<sub>r—

r—

proc</sub>−

O<sub>r—

calcN</sub>,

estimating the sign of the velocity (Segno) by comparing the said variables ResP and ResN.

13. System according to claim 9, in which the said processing means are programmed in such a way that operation d) comprises the following phases:

storing an initial estimated value α

(t₀) of the angle of inclination of the road, where the instant t₀ represents the moment at which the start of the vehicle'"'"'s movement is detected,

in a condition in which the vehicle is not in neutral, or in which the estimated value of the slope which is a function of the said initial value α

(t₀) is greater than a predetermined threshold, calculating angular velocities O<sub>r—

calcP</sub> and O<sub>r—

calcN</sub>, defined by the following relations;

$\begin{array}{c}{O}_{\mathrm{r\_calcP}}<br><br>\text{\hspace{1em}<br><br>}=\text{\hspace{1em}<br><br>}<br><br>O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)<br><br>\text{\hspace{1em}<br><br>}+\text{\hspace{1em}<br><br>}<br><br>{\int <br><br>}_0^t<br><br>\frac{1}{\text{\hspace{1em}<br><br>}<br><br>J_{\mathrm{eq}}}<br><br>\left(C_T-C_R<br><br>\text{\hspace{1em}<br><br>}-\mathrm{Rmg}<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}(\text{\hspace{1em}<br><br>}<br><br>t_0)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,\\ O_{\mathrm{r\_calcN}}<br><br>\text{\hspace{1em}<br><br>}=-O_{\mathrm{r\_proc}}<br><br>\left(t_0\right)<br><br>\text{\hspace{1em}<br><br>}+\text{\hspace{1em}<br><br>}<br><br>{\int <br><br>}_0^t<br><br>\frac{1}{\text{\hspace{1em}<br><br>}<br><br>J_{\mathrm{eq}}}<br><br>\left(C_T-C_R<br><br>\text{\hspace{1em}<br><br>}-\mathrm{Rmg}<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}(\text{\hspace{1em}<br><br>}<br><br>t_0)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>t,<br><br>\text{\hspace{1em}<br><br>}\end{array}$

where J_eq represents the equivalent inertia of the vehicle based on the wheels;

C_T is the torque transmitted to the wheels;

C_R indicates the resistant torque at the wheels, including the contribution of the brakes, the friction of the tyres and the aerodynamic resistance of the vehicle;

R represents the radius of the wheels;

m is the mass of the vehicle; and

ω

_wheels indicates the mean angular velocity of the non-driving wheels,

calculating a pair of variables ResP and ResN, defined by the following relations;

ResP=O<sub>r—

proc</sub>−

O<sub>r—

calcP</sub>,
ResN=−

O<sub>r—

proc</sub>−

O<sub>r—

calcN</sub>,

14. System according to claim 12, in which the said processing means are programmed to execute the said comparison of the variables ResP and ResN when the value of one of the said variables ResP and ResN exceeds a predetermined threshold.

15. System according to claim 13, in which the said processing means are programmed to execute the said comparison of the variables ResP and ResN when the value of one of the said variables ResP and ResN exceeds a predetermined threshold.