METHOD FOR DETERMINING A VISIBILITY

Abstract

Disclosed is a method for determining a visibility using a sensor unit, in particular a lidar sensor, including having the sensor unit emit a transmission signal, capturing a received signal backscattered by an object, determining the distance from the object using the received signal, and determining the visibility on the basis of the ascertained distance from the object and/or the strength of the received signal.

Claims

1-15. (canceled)

16. A method for determining a visibility using a lidar sensor, said method comprising: having the lidar sensor emit a transmission signal; capturing a received signal backscattered by an object; determining the distance from the object using the received signal; and determining the visibility based on at least one of the ascertained distance from the object and the strength of the received signal.

17. The method according to claim 16, wherein the distance of a first detection at which the object was detected for the first time is used in order to determine the visibility.

18. The method according to claim 17, wherein an initial value is specified for the distance of the first detection.

19. The method according to claim 18, wherein the visibility is determined using a comparison between the initial value and the currently existing distance of the first detection.

20. The method according to claim 19, wherein an initial value of the strength which the received signal has at a definable distance from the object is specified.

21. The method according to claim 20, wherein the visibility is determined using a comparison between the initial value and the received signal strength currently existing at the definable distance from the object.

22. The method according to claim 21, wherein the size of the deviation from the initial value is determined using the comparison and the visibility is classified by a correlation with the size of the deviation.

23. The method according to claim 22, wherein multiple measuring points of at least one of the distance and of the received signal strength are averaged, and the average is used in order to determine the visibility.

24. The method according to claim 23, wherein the visibility is determined using a comparison between the average and the respective initial value.

25. The method according to claim 16, wherein the visibility is determined on the basis of the ascertained distance from the object and on the basis of the strength of the received signal, wherein a plausibility check is provided in order to validate the visibility conditions ascertained during this against one another.

26. The method as set forth in claim 16, further comprising: assigning the determined visibility to one of a plurality of visibility classes using at least one parameter; assigning a recommended speed to each of the visibility classes; emitting the recommended speed of the respective visibility class to a vehicle operator.

27. The method according to claim 26, wherein the restriction of the vehicle operator by the visibility is provided as a parameter, wherein the restriction is in particular specified as quantified visibility classes and/or quantified visibility restrictions.

28. The method according to claim 16, further comprising correlating the determined visibility with characteristics of the roadway wherein the characteristics of the roadway are enlisted in order to emit a warning or a speed recommendation or to carry out an intervention.

29. The method according to claim 16, further comprising providing at least one of an optical warning and ab acoustic warning in order to notify the determined visibility.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The disclosure will be explained in greater detail below with reference to expedient exemplary embodiments, wherein:

[0025] FIG. 1 shows a simplified schematic diagram of a typical driving scenario;

[0026] FIG. 2 shows a simplified schematic diagram of an evaluation possibility of the method according to one embodiment, and

[0027] FIG. 3 shows a simplified diagram of the relationship between the determination of the visibility and speed recommendation.

DETAILED DESCRIPTION

[0028] A typical scenario with two vehicles 1, 2, in which the first vehicle 1 is following the second vehicle 2 or approaching an object (in this case vehicle 2), is depicted in FIG. 1. Instead of the second vehicle 2, another, possibly stationary object could, however, also be provided such as, e.g., a traffic pole or a guardrail. In vehicle 1 there is a clearance-measuring system having a sensor unit 1.1, by means of which, e.g., the clearance a from the vehicle 2 can be ascertained. The measurement is effected in that the sensor unit 1.1 emits a transmission signal 1.2 by means of a transmitting unit, which transmission signal is reflected by the vehicle 2 (not depicted in FIG. 1 for the sake of clarity). The reflected signal is subsequently received as a received signal by a receiver unit of the sensor unit 1.1. A second receiver unit is not required. As a general rule, a sensor unit 1.1 has a measurement threshold, within which an object or an obstacle can be captured. As a consequence, it is only possible to capture the object with a defined clearance or within a defined distance from the object. In particular, the sensor unit 1.1 can comprise a lidar (light detecting and ranging) sensor. For example, the transmitting unit can, e.g., comprise a laser diode, by means of which a light or laser signal can be transmitted. Alternatively or additionally, other sensors known from the prior art (radar, camera) can, however, also be provided.

[0029] The current visibility, i.e., a weakening of the transmitting unit and/or a reduction of the reception sensitivity of the receiver unit of the sensor unit 1.1, can be determined by virtue of reflections and diffusions by particles and flecks, using the first capturing of the object, i.e., of the first detection. The visibility can consequently be securely captured or identified with the aid of two variants V1, V2.

[0030] The results of multiple (clearance) measurements which have been generated, e.g., by the sensor unit 1.1 are depicted in FIG. 2, wherein each measuring point of the sensor (or the received signal strength) is assigned to a typical distance by means of a distribution curve. Furthermore, the two variants V1 and V2 for determining the visibility are depicted in a considerably simplified manner using the white arrows.

[0031] In the case of the first variant V1, a statistical evaluation is effected in such a way that the distance a is ascertained, at which distance an object is identified for the “first time” (correspondingly with a low received signal strength) when the vehicle is moving towards the object, the so-called first detection. In the event of adverse visibility or in the event of the visibility deteriorating, this distance (or the distribution curve) of the first detection is displaced towards a shorter distance, i.e., the obstacle is detected later in time and with a smaller clearance from the object. This effect occurs as a result of the beams of the lidar system being significantly attenuated in poor visibility conditions such as, e.g., fog, high humidity or spray, as a result of which the range of the system is reduced, so that the clearance at which the object can be detected by the measuring system decreases. Conversely, this means that in the event of the distribution curve being displaced, according to FIG. 2, in the direction of a shorter distance, i.e., along the x-axis in the direction of the y-axis as depicted by the arrow marked with V1, worse visibility conditions exist or the visibility has deteriorated, e.g., as a result of water particles finely distributed in the air, e.g., in the event of fog, wet conditions or spray.

[0032] In order to carry out the method, an initial value W1 for the distance of the first detection can, for example, be specified. The initial value W1 for the distance of the first detection is preferably specified by the manufacturer or during the initial commissioning, i.e., at a time at which, e.g., the prevailing visibility conditions are good. This initial value W1 can then in each case be compared with the value of the distance of the first detection, which is currently ascertained by the clearance sensor. From this comparison, a value for the deviation can then be calculated. Depending on this deviation, the currently existing visibility is then inferred, for example by storing tolerances and/or thresholds in the system which, if they are exceeded, indicate a deterioration of the visibility. Furthermore, the size of the deviation from the respective initial value W1 is determined using the comparison, wherein the visibility is graduated by correlating the gradations with the size of the deviation. For example, the visibility can be classified in visibility classes, e.g., “good” or “bad” or according to the restriction of the visibility (significant, medium or slight restriction) or into specific weather events (snow, rain, fog, spray and the like).

[0033] Alternatively or in addition to the first variant V1, the visibility can also be determined according to the second variant V2. In the case of variant V2, a statistical evaluation is effected in such a manner that a typical distance with a corresponding distribution can be deduced using a defined received signal strength.

[0034] In the same way, an initial value W2 of the strength which the received signal has at a definable distance from the object can also be specified, in order to determine the visibility. The visibility prevailing at any one time is likewise determined using a comparison between the initial value W2 of the received signal strength and the received signal strength currently existing or measured at the definable distance from the object. The visibility classes can then be classified or specified in a correlating manner with the received signal strength (e.g., high received signal strength stands for good visibility or a small restriction of the visibility).

[0035] Due to worsening visibility, the distance (the distribution curve) is displaced at the defined received signal strength towards a shorter distance. This effect occurs as a result of the fact that the optical signals are attenuated in poorer visibility conditions so that a lower received signal strength exists and the obstacle has to be brought closer to the measurement system in order to obtain the initially defined received signal strength again. Conversely, this means that if the distribution curve is displaced towards a shorter distance, i.e., as depicted by the arrow marked with V2, along the x-axis in the direction of the y-axis, it is possible to infer poorer visibility conditions. A displacement is identified by the measurement results moving away over time from the original (stored) measured values or initial values W1, W2. The displacement is a function of adverse visibility conditions, or a (technology-based) inference of the adverse effect on the view can be drawn using the size of the displacement. Other vehicles, or roadside boundary posts, road signs, trees and the like can be enlisted as obstacles or objects to be evaluated (the respective “obstacle class” has a typical distance at which the obstacle can be captured for the first time by a system for capturing the surroundings if the view is unrestricted, and can consequently be enlisted as a reference). The method can consequently be applied with all clearance-measuring systems and is expressly not restricted to just lidar sensors.

[0036] In order to improve the determination reliability, it is also possible to average multiple measuring points of the distance or of the receiver signal strength, as depicted in a very simplified manner in FIG. 2. Said average can subsequently be enlisted in order to determine the visibility. The visibility can then be determined using a comparison between the average and the respective initial value W1 or W2. Furthermore, a plausibility check can also be provided, e.g., by checking or validating the visibility which has been ascertained by the first variant against the result of the visibility determination by utilizing the second variant. In the same way, the visibility which has been ascertained by the second variant can also be checked or validated against the first variant.

[0037] Multiple measuring points of the distance or of the received signal strength can consequently also be simply averaged during the evaluation in order to make the determination even more secure. Thanks to such an averaging, measuring errors or erroneous individual measured values can be relativized, so that this cannot lead to misinterpretations by compensating for the deviating measured values by averaging with other measurement results.

[0038] The functional dependence between the current visibility and a speed recommendation or speed regulation is depicted by way of example in FIG. 3. A maximum vehicle speed is generated and displayed as a recommendation by an independently functioning assistance system depending on the current visibility (ascertained, e.g., with a lidar-based clearance measuring system). The display can be effected optically or acoustically. The visibility can either be determined using the method according to the invention or in another way such as, e.g., using transmitted information (car-to-car, car-to-X transmissions).

[0039] In summary, the vehicle operator can be provided with an independently functioning assistance function according to the invention (determination of visibility via lidar and resulting, recommended speed limitation). In particular, road safety can be particularly improved on routes which do not have digitization or a speed indication for adapting the speed in the event of adverse visibility conditions, so that the disclosure represents a very special contribution to the field of driver assistance functions.

LIST OF REFERENCE NUMERALS

[0040] 1 First vehicle [0041] 1.1 Sensor unit [0042] 1.2 Transmission signal [0043] 2 Second vehicle [0044] a Distance [0045] V1 First variant [0046] V2 Second variant [0047] W1 Initial value [0048] W2 Initial value