METHOD FOR DETERMINING THE CURRENT ANGLE OF LATERAL INCLINATION OF A ROADWAY

Abstract

The present invention relates to a method for determining the current angle of lateral inclination (a) of a roadway by means of a vehicle, at least comprising the steps of: a) determining the current radius of curvature (K) of the roadway; b) measuring the current velocities v(1,2) of at least two different wheels of the vehicle, one of the wheels with the velocity v(1) lying closer to the current curve center point of the roadway; c) calculating the current radius of lateral inclination (Q) of the roadway using the current wheel velocity v(1), the wheel distance (d) and the difference between the wheel velocities measured in method step b); d) calculating the current angle of inclination (a) of the vehicle on the roadway using the quotient of the radius of curvature (K) determined in method step a) and the current radius of lateral inclination (Q) calculated in method step c). The present invention further relates to the use of the method to monitor and/or control a vehicle, to a driver assistance system designed to carry out the method according to the invention, and to a vehicle having such a driver assistance system.

Claims

1. A method for determining the current angle of lateral inclination a of a roadway by vehicle, comprising: a) determining a current radius of curvature K of the roadway; b) measuring current velocities of at least two different wheels of the vehicle, one of the wheels with the velocity lying closer to a current center of the curve on the roadway; c) calculating a current radius of lateral inclination Q of the roadway on the basis of the current wheel velocity, a wheel distance and the difference between the wheel velocities measured in method step b); and d) calculating the current angle of lateral inclination a of the roadway using the quotient of the radius of curvature K determined in method step a) and the current radius of lateral inclination Q calculated in method step c).

2. The method as claimed in claim 1, the current radius of lateral inclination Q of the roadway being determined in method step c) using the following formula I: $Q=\frac{v\left(1\right)*d}{v\left(2\right)-v\left(1\right)}$

3. The method as claimed in claim 1, the current angle of inclination α of the roadway being determined in method step d) using the following formula II: $\alpha =\arccos \left(\frac{K}{Q}\right)$

4. The method as claimed in claim 1, the velocities of wheels of one vehicle axle being measured in method step b).

5. The method as claimed in claim 1, the velocities measured in method step b) being adjusted as a function of the tire pressure of the respective wheel.

6. The method as claimed in claim 1, method steps b)-d) only being carried out in those cases in which in method step a) the current radius of curvature K of the roadway is less than or equal to 3000 m.

7. The method as claimed in claim 1, the current radius of curvature K of the roadway being determined in method step a) from GPS or camera data.

8. The method as claimed in claim 1, wherein the method is used as part of a routine for monitoring and/or controlling a vehicle.

9. A driver assistance system for a motor vehicle, comprising: at least two wheels with velocity sensors; a control unit; and a GPS module or a camera, the control unit being in electrical contact with the velocity sensors of the wheels and with the camera or GPS module, and the control unit being set up to carry out the method as claimed in claim 1.

10. The driver assistance system as claimed in claim 9, the driver assistance system being set up to postulate, as a function of the current vehicle velocity v.sub.current, k.sub.fric a lateral friction coefficient of the roadway, a gravitational acceleration g, K.sub.following the radius of curvature K of the roadway directly ahead, a selected point in time t, Δt a time interval and C.sub.exp an experimental factor and according to the following mathematical relationship:
V.sub.current.sup.2(t)<C.sub.exp. k.sub.fric. g. K.sub.following(t +Δt), an estimate of the safety of traversing the next curve at the current vehicle velocity and, in cases where the square of the vehicle velocity is greater than the right-hand part of the mathematical relationship, issue a warning to the driver or reduce the velocity of the vehicle.

11. A vehicle with a driver assistance system as claimed in claim 9.

Description

[0046] In the drawings:

[0047] FIG. 1 schematically shows a representation of a vehicle traveling on an inclined and curved roadway;

[0048] FIG. 2 schematically shows a representation of the variables used in the method according to the invention;

[0049] FIG. 3 schematically shows a representation of the variables used in the method according to the invention;

[0050] FIG. 4 schematically shows a representation of an embodiment of a system according to the invention.

[0051] FIG. 1 schematically shows a driving situation of a vehicle (2) on a roadway (1). The roadway (1) is delimited by the left edge (4) and right edge (5) of the roadway, the edges of the roadway (4, 5) being defined on the basis of the direction of travel of the vehicle (2). In the figure, the rear view of the vehicle (2) is shown schematically. The edges of the roadway (4, 5) are at different heights, so that the vehicle axis of the vehicle (2) is shown inclined. For example, this figure may relate to a movement of a vehicle (2) on a curve to the left, it also being possible for example that only the current section of the roadway is approximated by the circles shown. In this example, the vehicle has two rear wheels (6, 7), the rear wheel (6) lying closer to the center of the curvature of the roadway. The right wheel (7) is further away from the center of the curve to the left. The wheel distance d of the vehicle is obtained from the distance between the right wheel (7) and the left wheel (6).

[0052] FIG. 2 shows a roadway situation that is comparable to FIG. 1, the vehicle having been omitted from this illustration for the sake of clarity. The roadway (1) is delimited by the left edge (4) and right edge (5) of the roadway, the edges of the roadway (4, 5) having different heights. The right edge (5) of the roadway is shown higher compared to the left edge (4) of the roadway. The current radius of curvature K of the roadway (1) is obtained from a two-dimensional projection of the roadway (1) and extends from the center of the circle (9) to the right edge of the roadway (5). This distance is also known as the inverse of the curvature. Differences in height of the edges of the roadway are not taken into account in this projection, since it is a purely two-dimensional projection of the current roadway situation. The specific circle fitting that is appropriate for the roadway situation can be obtained, for example, via tabulated values that are stored as a function of the GPS position.

[0053] In contrast to the current radius of curvature K of the roadway (1), the radius of lateral inclination Q is obtained from a distance that takes into account the inclination of the roadway (1). The radius of lateral inclination Q of the roadway (1) is obtained in FIG. 2 from the distance (10, 4). Thus, the radius of lateral inclination Q of the roadway (1) differs both in the starting point on the axis of the circle and by the end point at the left edge (4) of the vehicle, which in this example coincides with the left edge (4) of the roadway. In cases where the vehicle is smaller than the roadway (1), the radius of lateral inclination Q is based on an imaginary line through the right wheel (7) and left wheel (6) of the vehicle to the center of the circle (10), the radius of lateral inclination Q only being obtained from the distance from the center of the circle to the wheel closest to the curve, in this case the left wheel (6). Taking into account the gradient of the roadway, there is a different radius, which is all the more different the greater the gradient of the road.

[0054] Based on the assumption that the angular velocities of the right wheel (7) and left wheel (6) of the vehicle must be the same, the following relationship is obtained for the current angular velocity w(t) of the individual wheels:

[00003]$\omega \left(t\right)=\frac{v\left(1\right)}{Q}=\frac{v\left(2\right)}{Q+d}$

[0055] The current angular velocity is therefore obtained from the current velocity of the left wheel (6) v(1), which must be equal to the angular velocity of the right wheel (7) with the velocity v(2). This equation can be solved on the basis of the radius of lateral inclination Q and gives:

[00004]$Q=\frac{v\left(1\right)*d}{v\left(2\right)-v\left(1\right)}$

[0056] On the basis of this equation, the current angle of inclination a is obtained as

[00005]$\alpha =\arccos \left(\frac{K}{Q+d}\right)\approx \arccos \left(\frac{K}{Q}\right)$

[0057] This relationship is obtained on the assumption that the wheel distance d is very small compared to the radius of lateral inclination Q.

[0058] FIG. 3 describes the same situation as in FIGS. 1 and 2, the roadway having been omitted for the sake of clarity. The current radius of curvature K of the roadway is obtained from the distance (9, 6), i.e. from the center axis of the circle to the wheel furthest away from the curve, the right wheel (6). The radius of lateral inclination Q is obtained from the distance (10, 7), i.e. from the center axis of the circle to the left wheel (7) of the vehicle. As shown above, the current angle of lateral inclination a of the roadway can be determined from the two variables K and Q.

[0059] FIG. 4 schematically shows an embodiment according to the invention of a driver assistance system according to the invention. A vehicle (2) which has rear wheels with Hall sensors (13) is shown. Furthermore, the vehicle (2) has a control unit in the form of an ECU (Electronic Control Unit, 12) and a GPS module (11) or a camera (11). The individual components of the system are at least electrically connected via the control unit (12) and the ECU (12) is set up to perform the required steps of the method according to the invention and to determine the angle of inclination of the roadway (1) using the camera/GPS data and the velocity data of the wheels.

LIST OF REFERENCE SIGNS

[0060] 1 Roadway

[0061] 2 Vehicle (rear view)

[0062] 3 Vehicle axis

[0063] 4 Left delimitation of the roadway

[0064] 5 Right delimitation of the roadway

[0065] 6 Left wheel of the vehicle

[0066] 7 Right wheel of the vehicle

[0067] 8 Center of curve

[0068] 9 Radius of curvature K of the roadway

[0069] 10 Radius of lateral inclination Q

[0070] 11 GPS sensor or camera

[0071] 12 ECU

[0072] 13 Rear wheel with velocity sensors