METHOD AND SYSTEM FOR DETERMINING A FORDING SITUATION

Abstract

A driver assistance system includes a first measuring device for determining distances from a water surface, which includes at least two distance sensors. First and second distance sensors are situated laterally on the vehicle with respect to a respective side of the vehicle. The first and second distance sensor measure a first distance from a water surface by determining the distance perpendicularly downward from the respective sensor to the water surface. The system includes a second measuring device for determining an instantaneous roll angle of the vehicle and a processing unit, which is coupled to the first measuring device and to the second measuring device. The processing unit determines at least one first transversal component of the instantaneous flow velocity of the body of water forming the water surface, as a function of the first distance, the second distance and the instantaneous roll angle of the vehicle.

Claims

1. A driver assistance system configured to determine a fording situation of a vehicle, comprising: a first measuring device configured to determine distances from a water surface, including at least two distance sensors, a first distance sensor of the at least two distance sensors being configured to be situated laterally with respect to a first side of the vehicle, and a second distance sensor of the at least two distance sensors being configured to be situated laterally with respect to a second side of the vehicle, the second side being situated opposite the first side, and the first distance sensor being configured to measure a first distance from a water surface, and the second distance sensor being designed to measure a second distance from the water surface; a second measuring device configured to determine an instantaneous roll angle of the vehicle; a processing unit, coupled to the first measuring device and the second measuring device, configured to determine at least one first transversal component of an instantaneous flow velocity of a body of water forming the water surface, as a function of the first distance, of the second distance, and of the instantaneous roll angle of the vehicle.

2. The driver assistance system as recited in claim 1, wherein the driver assistance system additionally includes a third measuring device configured to determine an instantaneous pitch angle of the vehicle, the processing unit being coupled to the third measuring device and configured to determine at least one component of the instantaneous flow velocity as a function of the instantaneous pitch angle of the vehicle.

3. The driver assistance system as recited in claim 1, wherein the first measuring device additionally includes a third distance sensor and a fourth distance sensor, the third distance sensor being configured to be situated on a front bumper of the vehicle, and the fourth distance sensor being configured to be situated on a rear bumper of the vehicle, the third distance sensor being configured to measure a third distance from the water surface, and the fourth distance sensor being configured to measure a fourth distance from a water surface, and the processing unit being configured to determine a second longitudinal component of the instantaneous flow velocity as a function of the third distance, of the fourth distance and of the instantaneous pitch angle of the vehicle.

4. The driver assistance system as recited in claim 3, wherein the driver assistance system further includes a memory unit, which includes a table in which respectively assigned velocity values are stored for a multitude of combinations of measured values for the first distance and the second distance and/or for a multitude of combinations of measured values for the third distance and the fourth distance and/or for a multitude of difference values of the first, second, third and fourth distances, the table being specific to a certain vehicle type.

5. The driver assistance system as recited in claim 1, wherein the driver assistance system includes a warning unit, the processing unit being configured to compare an absolute value of at least one component of the instantaneous flow velocity to a velocity threshold value, and the warning unit being configured to output a warning as a function of the comparison.

6. The driver assistance system as recited in claim 5, wherein the velocity threshold value is predefined as a function of an instantaneous fording depth and/or as a function of an instantaneous driving speed and/or as a function of an instantaneous driving direction of the vehicle and/or as a function of an instantaneous wheel slip.

7. The driver assistance system as recited in claim 1, wherein the first and second distance sensors are each ultrasonic sensors.

8. A vehicle comprising: a vehicle assistance system configured to determine a fording situation of a vehicle, comprising: a first measuring device configured to determine distances from a water surface, including at least two distance sensors, a first distance sensor of the at least two distance sensors situated laterally with respect to a first side of the vehicle, and a second distance sensor of the at least two distance sensors situated laterally with respect to a second side of the vehicle, the second side being situated opposite the first side, and the first distance sensor being configured to measure a first distance from a water surface, and the second distance sensor being designed to measure a second distance from the water surface; a second measuring device configured to determine an instantaneous roll angle of the vehicle; a processing unit, coupled to the first measuring device and the second measuring device, configured to determine at least one first transversal component of an instantaneous flow velocity of a body of water forming the water surface, as a function of the first distance, of the second distance, and of the instantaneous roll angle of the vehicle.

9. The vehicle as recited in claim 8, wherein the first distance sensor and the second distance sensor are each situated on a side mirror of the vehicle.

10. A method for determining a fording situation of a vehicle, wherein the vehicle includes a first measuring device for determining distances from a water surface, including at least two distance sensors, a first distance sensor of the at least two distance sensors being situated laterally with respect to a first side of the vehicle, and a second distance sensor of the at least two distance sensors situated laterally with respect to a second side of the vehicle, the second side being situated opposite the first side, and the vehicle including a second measuring device configured to determine an instantaneous roll angle of the vehicle, the method comprising: measuring a first distance from a water surface using the first distance sensor; measuring a second distance from the water surface using the second distance sensor; determining at least one first transversal component of an instantaneous flow velocity of a body of water forming the water surface as a function of the first distance, the second distance, and the instantaneous roll angle of the vehicle.

11. The method as recited in claim 10, wherein the vehicle includes a third measuring device for determining an instantaneous pitch angle of the vehicle, at least one component of the instantaneous flow velocity being determined as a function of the instantaneous pitch angle.

12. The method as recited in claim 11, wherein the first measuring device includes a third distance sensor and a fourth distance sensor, the third distance sensor being situated on front bumper of the vehicle, and the fourth distance sensor being situated on a rear bumper of the vehicle, a third distance from the water surface being measured using the third distance sensor, and a fourth distance from the water surface being measured using the fourth distance sensor, and a second longitudinal component of the instantaneous flow velocity of the body of water forming the water surface being determined as a function of the third distance, the fourth distance, and the instantaneous pitch angle of the vehicle.

13. The method as recited in claim 12, wherein an absolute value of a component of the instantaneous flow velocity is determined by reading out a table, the table including respectively assigned velocity values for a multitude of combinations of measured values for the first distance and the second distance and/or for a multitude of combinations of measured values for the third distance and the fourth distance and/or for a multitude of difference values of the first, second, third and fourth distances, the absolute value of the component of the instantaneous flow velocity being determined by correcting a velocity value assigned to the measured values for the first distance, and the second distance and/or the measured values for the third distance and the fourth distance, as a function of the instantaneous roll angle and/or of the instantaneous pitch angle.

14. The method as recited in claim 11, wherein an absolute value of at least one component of the instantaneous flow velocity is compared to a velocity threshold value, and a warning is output as a function of the comparison.

15. The method as recited in claim 14, wherein the velocity threshold value is predefined as a function of an instantaneous fording depth and/or as a function of an instantaneous driving speed of the vehicle.

16. A non-transitory computer-readable data medium on which is stored a computer program product including program for determining a fording situation of a vehicle, wherein the vehicle includes a first measuring device for determining distances from a water surface, including at least two distance sensors, a first distance sensor of the at least two distance sensors being situated laterally with respect to a first side of the vehicle, and a second distance sensor of the at least two distance sensors situated laterally with respect to a second side of the vehicle, the second side being situated opposite the first side, and the vehicle including a second measuring device configured to determine an instantaneous roll angle of the vehicle, the program, when executed by a processing unit, causing the processing unit to perform: measuring a first distance from a water surface using the first distance sensor; measuring a second distance from the water surface using the second distance sensor; determining at least one first transversal component of an instantaneous flow velocity of a body of water forming the water surface as a function of the first distance, the second distance, and the instantaneous roll angle of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 schematically shows a vehicle while crossing a moving body of water in a top view.

[0035] FIGS. 2a and 2b schematically show a vehicle including a driver assistance system according to a first embodiment of the present invention while crossing a moving body of water in a front view.

[0036] FIG. 3 schematically shows a vehicle including a driver assistance system according to a second embodiment of the present invention while crossing a moving body of water in a side view.

[0037] FIG. 4 schematically shows a method according to the present invention in the form of a flow chart.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0038] In the following description of the exemplary embodiments of the present invention, identical elements are denoted by the same reference numerals, a repeated description of these elements being dispensed with, if necessary. The figures only schematically represent the subject matter of the present invention.

[0039] FIG. 1 shows a vehicle 1 in a top view, which is in the process of crossing a moving body of water 50, for example a river or a creek. Vehicle 1 is moving in driving direction 80. Flow velocity 70 of body of water 50 is a vector quantity which may be broken down into a longitudinal component 72, in parallel to driving direction 80 of the vehicle or to a geometric longitudinal axis of vehicle 1, and into a transversal component 74 orthogonal thereto, perpendicular to driving direction 80. The absolute values and directions of these two vector components of the flow velocity may be ascertained with the aid of the present invention.

[0040] FIGS. 2a) and 2b) show a vehicle 1 including a driver assistance system according to a first embodiment of the present invention in two different situations.

[0041] FIG. 2a) shows vehicle 1 in a front view. Vehicle 1 is in a fording situation, i.e., it is negotiating a body of water 50. The vehicle is moving on a ground 60 flooded by water in such a way that at least portions of the front tires are situated below water surface 52. Body of water 50 has a current having a transversal component 74 of the flow velocity transversely to vehicle 1. The current causes water to be retained on side 12 of vehicle 1 facing the current, in area 51. This effect is utilized according to the present invention to determine transversal component 74 of the flow velocity. For this purpose, vehicle 1 on its side mirrors 16a and 16b includes a respective distance sensor 14a and 14b designed as an ultrasonic sensor. Distance sensors 14a and 14b are situated in such a way that their respective measuring areas 24a and 24b are essentially downwardly directed in the direction of water surface 52 directly beneath the respective side mirror 16a or 16b. Installation height h.sub.1 of first distance sensor 14a is equal to installation height h.sub.2 of second distance sensor 14b. First distance sensor 14a is thus designed to measure a first distance d.sub.1 from water surface 52 on first side 11 of the vehicle, and second distance sensor 14b is designed to measure a second distance d.sub.2 from water surface 52 on second side 12 of the vehicle. Since the existing current in area 51 on second side 12 of the vehicle results in a certain retention of the water, second distance sensor 14b in the shown situation measures a distance d.sub.2 which is smaller than distance d.sub.1 measured by first distance sensor 14a on first side 11. Since vehicle 1, in the shown situation, exhibits no lateral inclination (roll angle .sub.Roll=0), difference u.sub.12 between measured first distance d.sub.1 and measured second distance d.sub.2 is directly attributable to the current, in particular to the component of the current perpendicular to the geometric longitudinal axis of vehicle 1 (transversal component). The determination of transversal component 74 of the flow velocity takes place with the aid of a processing unit (not shown), which is coupled to distance sensors 14a and 14b and a second measuring device for determining instantaneous roll angle .sub.Roll, as a function of first distance d.sub.1, of second distance d.sub.2 and of instantaneous roll angle .sub.Roll of vehicle 1.

[0042] FIG. 2b) shows a situation in which vehicle 1 is traveling on a ground 60 inclined perpendicularly to the vehicle longitudinal axis. This results in a roll angle, .sub.Roll0, in this example .sub.Roll>0. To determine the transversal component of the flow velocity, roll angle .sub.Roll is determined with the aid of a suitable sensor (not shown), for example an acceleration sensor or a spirit level and taken into consideration in the determination of the transversal component of the flow velocity.

[0043] To find out in which direction the flow velocity is maximal, the orientation of the vehicle may be varied, and the transversal component of the flow velocity may be continuously determined in the process. As soon as vehicle 1 has changed its driving direction once by at least 180, the orientation of the vehicle in which the absolute value of the transversal component of the flow velocity assumes its maximum may be determined via the progression of the measured transversal component of the flow velocity. The associated orientation of the vehicle is then perpendicular to the flow direction.

[0044] In particular in shallow bodies of water, additional distance sensors 14c and 14d, which are situated on the front and rear bumpers of the vehicle, may be used to directly determine a second, in particular longitudinal, component of the instantaneous flow velocity of the body of water. FIG. 3 shows a vehicle 10 thus equipped in a side view.

[0045] Vehicle 10 includes a driver assistance system according to the illustration in FIG. 2 for determining transversal component 74 of the flow velocity. Vehicle 10 is in a fording situation, i.e., it is situated in a body of water 50. The vehicle is standing in this case on a ground 60 flooded by water in such a way that at least portions of the tires are situated below water surface 52. Body of water 50 has a current having a longitudinal component 72 of the flow velocity along vehicle 10. The current causes water to be retained on side 13 of vehicle 10 facing the current, in area 51. This effect is utilized according to the present invention to determine longitudinal component 72 of the flow velocity. For this purpose, vehicle 10 also includes on its bumpers 17c on the front and 17d on the rear in each case a distance sensor 14c and 14d designed as an ultrasonic sensor. Distance sensors 14c and 14d are situated in such a way that their respective measuring areas 24c and 24d are oriented obliquely downwardly directed in the direction of water surface 52 in front of or behind vehicle 10. Installation height h.sub.3 of third distance sensor 14c in this example is equal to installation height h.sub.4 of fourth distance sensor 14d. Third distance sensor 14c is thus designed to measure a third distance d.sub.3 from water surface 52 in front of vehicle 10, and fourth distance sensor 14d is designed to measure a fourth distance d.sub.4 from water surface 52 behind vehicle 10. Since the existing current in area 51 in front of the vehicle results in a certain retention of the water, third distance sensor 14c in the shown situation measures a distance d.sub.3 which is smaller than distance d.sub.4 measured by fourth distance sensor 14d behind the vehicle. Since vehicle 10, in the shown situation, exhibits no longitudinal inclination (pitch angle .sub.Pitch=0), and additionally is not moving, difference u.sub.34 between measured third distance d.sub.3 and measured fourth distance d.sub.4 is directly attributable to the current, in particular to the component of the current in the direction of geometric longitudinal axis 8 of vehicle 10 (longitudinal component). The determination of longitudinal component 72 of the flow velocity takes place with the aid of a processing unit 40, which is additionally coupled to third distance sensor 14c and fourth distance sensor 14d, and of a measuring device for determining instantaneous pitch angle .sub.Pitch of vehicle 10, as a function of third distance d.sub.3, of fourth distance d.sub.4 and of instantaneous pitch angle .sub.Pitch of vehicle 10.

[0046] As an alternative or in addition, sensors 14c and 14d may be designed to detect whether or that an immersion of the respective sensor has taken place. This may take place, for example, by detecting a characteristic signal of an ultrasonic sensor, which is generated when a membrane of the ultrasonic sensor makes contact with a water surface or is situated under water. If it is detected, for example, that third sensor 14c is already in contact with the water surface or is already immersed, while fourth sensor 14d still has no contact with water, a current in the direction of geometric longitudinal axis 8 of vehicle 10 (longitudinal component) may be inferred when the installation heights of sensors 14c and 14d are known.

[0047] FIG. 4 shows a block diagram of procedure 90 of a method according to the present invention, for example, for executing a computer program on a processing unit 40 of a driver assistance system according to the present invention. With the aid of distance sensors 14a and 14b, distance signals d.sub.1 and d.sub.2 are generated, which describe the distance of the respective sensor 14a and 14b from the water surface. These may be results from individual measurements or, for example, average values from multiple measurements. Optionally, with the aid of further distance sensors 14c and 14d, distance signals d.sub.3 and d.sub.4 are also generated, which describe the distance of the respective sensor 14c and 14d from the water surface. These may, in turn, be results from individual measurements or, for example, average values from multiple measurements. A difference value u.sub.12 is formed from distance signals d.sub.1 and d.sub.2. Optionally, a difference value u.sub.34 is formed from distance signals d.sub.3 and d.sub.4. If necessary, predefined installation heights h.sub.1, h.sub.2, h.sub.3, h.sub.4 and other known geometric quantities 85 of the vehicle may be considered in the calculation of difference values u.sub.12 or u.sub.34. With the aid of difference value u.sub.12 and of a roll angle .sub.Roll determined by a suitable measuring device 34, a first component of the flow velocity is calculated in program step 110. For this purpose, a table 130 is also polled, in which flow velocity values assigned to various values of u.sub.12 in a vehicle-specific manner are stored. Optionally, with the aid of difference value u.sub.34 and a pitch angle .sub.Pitch optionally determined by a suitable measuring device 36, a second component of flow velocity is also calculated in program step 110. For this purpose, flow velocity values assigned to various values of u.sub.34 in a vehicle-specific manner are additionally stored in table 130.

[0048] In program step 120, the absolute value of the first determined component and optionally the absolute value of the second determined component of the flow velocity are each compared to a velocity threshold value 135. The velocity threshold value may be predefined as a function of an instantaneous fording depth and/or of an instantaneous driving speed and/or of further driving dynamics variables.

[0049] A piece of warning information 140 is output as a function of the comparison result. For example, at a water depth or fording depth of 15 cm, a flow velocity, in particular, transversely to the vehicle, of 30 km/h may be predefined as the velocity threshold value. In contrast, at a water depth or fording depth of 80 cm, a flow velocity, in particular, transversely to the vehicle, of only 5 km/h may be predefined as the velocity threshold value. As an alternative or in addition, the velocity threshold value may be varied as a function of an instantaneously measured wheel slip. A high wheel slip indicates a ground surface having low friction. In the case of ground surfaces having low friction, the risk of vehicle 1 being swept away by the current may be increased. On the other hand, the current may also be utilized to minimize the slippage of the vehicle on a ground surface having low friction. When the flow direction and flow velocity are known, vehicle 1 may be oriented in such a way that the vehicle offers preferably little resistance to the current. For example, the front of the vehicle, which usually has a lower flow resistance than a lateral surface 11, 12, may be oriented counter to the flow direction. Similarly, as an alternative, the rear could also be oriented counter to the flow direction.