DE102019212668A1 - Method and device for real-time determination of properties of a roadway currently being used by a vehicle - Google Patents

Abstract

A method for real-time determination of a surface condition of a roadway currently being driven on by a vehicle comprises the optical detection, in several discrete wavelengths or wavelength ranges, of the light reflected from a surface of a roadway section illuminated by a light source with properties known for the discrete wavelengths or wavelength ranges, and the Determination of the ratios of light incident on the road surface and reflected light at the several discrete wavelengths or wavelength ranges. On the basis of a comparison of provided reference values of the ratios of incident and reflected light at the several discrete wavelengths or wavelength ranges for a multitude of surface conditions of a multitude of different road surfaces with the ratios of incident and reflected light determined for the currently traveled section of the road at the several discrete wavelengths or wavelength ranges a probability for the presence of a certain road surface and surface condition can be determined, which correlates a probability with the degree of agreement of the ratios of incident and reflected light with the corresponding reference values. A related technique uses reflected sound waves in a similar way. The surface condition determined can be used to control systems to influence the driving dynamics.

Description

FIELD

The present invention relates to the determination of surface conditions, in particular to the determination of those conditions of surfaces of roadways which are important for driving vehicles on.

BACKGROUND

Many land vehicles are designed for operation on more or less well-developed, predominantly paved roads or are operated on such roads.

While an essential property of the road surface when operating land vehicles on unpaved roads and roads is the presence of more or less large and deep ruts and potholes or the general strength of the road surface, and a layer of ice or a film of water are of rather minor importance as a condition The change in the static friction properties of the road surface, for example through layers of snow or ice, water, oil or lubricating films on paved paths and roads play a major role in the safe operation of vehicles. The degree of change in the static friction properties due to these generally temporary coverings also depends on the surface roughness and the material of the surface itself, which, however, change only slowly, if at all.

The static friction properties are of great importance for the adhesion between the tread of the tire and the road surface, which in turn has a decisive influence on the maximum possible acceleration or deceleration and the lateral tracking.

In order to prevent the wheels from spinning and the vehicle slipping away, a driver of a land vehicle must visually detect a state of a section of the road ahead in the direction of travel and adjust the speed of the vehicle and the steering movements in advance.

The correct assessment of the surface condition of a roadway through visual detection requires a great deal of experience. Nevertheless, misjudgments can occur, for example in the case of poor visibility, glare from sunlight or the light from the headlights of oncoming vehicles, or from the reflection or diffraction of light from layers of air at different temperatures directly above the road surface.

Current rain or snowfall are easily recognizable for any driver, and the immediate consequence of this, namely a film of water or a layer of snow on the road, is obvious, so that a driver would adjust the speed of the vehicle accordingly.

A temperature sensor present in many vehicles for determining the ambient temperature of the vehicle can only determine the air temperature at a distance from the road surface. From this it can be estimated whether a road is possibly slippery, especially after prolonged cold spells in which the ground has cooled down significantly, an indicated air temperature that is sufficiently far above the freezing point of water can lead to the erroneous assumption that a layer of ice cannot form on the road surface. The combination of current temperature data with data from a rain sensor available for automatic control of the windshield wipers of the vehicle or a camera provided for this purpose also does not provide any reliable information about the actual road condition. It cannot be determined, for example, whether a road is still slippery or whether de-icing agent or sand has already been applied.

The sensors for driving dynamics systems available in many vehicles, for example ESP, ABS, ASR and the like, can also provide information about the conditions of the road surface, but only for an area of the road surface that is already under the vehicle or under the contact patch of the tires. A predictive adjustment of the speed and driving style is therefore not possible for a single vehicle. In addition, meaningful sensor values are only available shortly before or when a limit range is reached, so that, for example, with a very cautious driver, none of the driving dynamics systems would respond and detect a possibly slippery road. In addition, the individual tires of the vehicle, i.e. tire type, tread type, tread depth, tire pressure, and the like play an essential role for the static friction between the road surface and the contact area of the tire and thus for the point in time at which a driving dynamics system would actively intervene.

Vehicles are increasingly being provided with means of communication by means of which they can exchange information about traffic situations and also road or lane conditions. These means of communication include, for example, those known by the abbreviations Car-to-Car (C2C) or Vehicle-to-Vehicle (V2V) Concepts and systems for direct communication between vehicles. Systems that enable vehicles to communicate with one another, if necessary via fixed transmitting and receiving stations on the road, are known under the abbreviations Car-to-X (C2X) or Vehicle-to-X (V2X). By means of these systems, vehicles driving ahead or oncoming vehicles can report actually determined conditions of the road surface by analyzing their sensors for vehicle dynamics systems, but with the restrictions of accuracy as explained in the preceding paragraph.

However, the mere possibility of communication between vehicles does not offer any advantage if there is no other vehicle in communication range that has detected and can transmit states of the road surface.

DESCRIPTION

It is therefore an object of the present invention to specify a method and a device for real-time determination of a surface condition of a roadway currently being driven on by a vehicle, which avoid or reduce one or more of the disadvantages or inadequacies of known systems. Another object of the present invention is to provide a method for improved vehicle dynamics control based on the detected surface condition and a corresponding device for a land vehicle.

A method for real-time determination of a surface condition of a roadway currently being traveled by a vehicle according to a first aspect of the invention comprises the optical detection of the light reflected from a surface of a roadway section illuminated by a light source. The detection takes place at several discrete wavelengths or wavelength ranges. The properties of the light source, in particular the intensity or amplitude of the light hitting the road surface, are known for the multiple discrete wavelengths or wavelength ranges, so that from the proportions of the reflected light at the multiple discrete wavelengths or wavelength ranges that, taken together, represent a spectral fingerprint , the surface condition of the road can be inferred. It does not matter whether the road section is illuminated with light in discrete wavelengths or wavelength ranges, or with light that is present in a continuous spectrum, as long as the amplitudes of the light in the detected wavelengths or wavelength ranges are known.

The method according to the first aspect further comprises determining the ratios of light incident on the road surface and reflected light at the plurality of wavelengths or wavelength ranges to one another, and providing reference values of the ratios of incident and reflected light to one another for a plurality of surface conditions of a plurality of different road surfaces .

The method according to the first aspect also includes comparing the ratios of incident and reflected light determined for the road section at the multiple discrete wavelengths or wavelength ranges to one another with the reference values provided for the multiple surface conditions for a large number of different road pavements. The degree of correspondence between the ratios of incident and reflected light with the corresponding reference values indicates a probability of the presence of a specific road surface and surface condition.

In one or more embodiments, the method includes, in addition to detecting the light reflected from the road surface, determining the intensities of the light incident on the road surface from the light source at the multiple discrete wavelengths or wavelength ranges, i.e. determining the spectral properties of the light source. This is particularly advantageous when a light source with an unknown spectrum is used to illuminate the roadway. The spectral properties of the light source are determined at least for the wavelengths or wavelength ranges in which the light reflected from the road surface is detected. The amplitudes in the respective recorded wavelengths or wavelength ranges are of particular interest here. The recorded spectral properties of the light source are used in the method as normal values to which the recorded values of the reflected light are set in relation. Since, as a rule, there is no corresponding sensor located directly on the road surface, the determination of the spectral properties of the light source can also take place with sensors arranged at known installation locations on the vehicle. The respective installation location and the respective direction of incidence of light and the distance from the light source can be used to determine correction values.

This embodiment is particularly advantageous when the light from an external light source is used to determine surface conditions, for example the light from the sun, oncoming vehicles or vehicles driving ahead, or street lighting. Sunlight has a Well-known spectrum, so that the determination of the intensity of the light hitting the road surface is comparatively easy for the detected wavelengths or wavelength ranges. In addition, the sun is very far away, so the direction of the incidence of light can easily be determined. With other light sources, determining the direction and possibly the distance of the incident light is somewhat more complex. The direction and distance of a light source can be determined, for example, by means of cameras arranged on the vehicle, for example cameras for lane keeping assistants or traffic sign recognition and the like. The use of radar or lidar sensors arranged on the vehicle to detect the direction and distance is also conceivable. When using external light sources at a greater distance from the sensors or cameras, the frequency analysis method must be adapted from near-field to suitable far-field methods according to the distance between the light source.

In one or more embodiments of the method, the light source is arranged on the vehicle which is carrying out the method. The light source is set up to illuminate the roadway section one after the other with light in one of the several discrete wavelengths or wavelength ranges. This can be done, for example, with a corresponding headlight that repeatedly illuminates the road surface with light of different wavelengths or wavelength ranges. If the vehicle moves during the detection, different road sections are at least partially illuminated with light of different wavelengths or wavelength ranges. This can be taken into account when detecting the reflected light from the lane sections, for example with a camera, in that successively recorded images are overlaid with the individual colors depending on the speed of the vehicle and the duration of the lighting, so that images for each lane section are available that are illuminated with light of all wavelengths or wavelength ranges. The sequence of lighting with the different colors and the recording of images with the camera is synchronized accordingly.

A suitable light source is, for example, a headlight that illuminates the roadway with light in the primary colors red, green and blue. If the color change is sufficiently rapid, the lighting is perceived as white light by a human observer, so that appropriately equipped headlights or fog lights of the vehicle can be used for the lighting.

Suitable illuminants that emit light at one wavelength or in a comparatively narrow wavelength range with sufficient power and enable rapid switching on and off are available in the form of light-emitting diodes. If light in particularly narrow-band wavelength ranges is required, quantum dot light-emitting diodes or laser light sources can be used.

It is also possible to use white light sources that generate monochromatic light in the desired wavelengths or wavelength ranges by means of suitable color filters. The color filters can also be set up as replaceable filters, so that light of different colors can be generated by means of a white light source.

In order to absorb as little extraneous light as possible with the sensor, the light source and the sensor can be arranged on the underside of the vehicle, for example in the middle below the vehicle. Here, the distance between the light source and the road surface as well as the road surface and the sensor can be kept particularly small. In order to achieve as homogeneous an illumination as possible of a section of the road surface despite the small distance, suitable lens systems can be provided.

In one or more embodiments, the method also includes receiving one or more sensor values or additional information from the incomplete group including a local temperature, a date, a time of day, a geographical position, and a local or regional weather report. Alternatively or additionally, in this embodiment, the method can include receiving static or only slowly changing roadway properties from a database, such as, for example, the material of the roadway, surface roughness and the like. The database can be arranged in a vehicle which is set up to carry out the method, for example in a database of a navigation system, or can be arranged outside the vehicle and connected to it via a data connection.

The sensor values and additional information can be used, for example, to check the plausibility of a state of the surface of a roadway determined using the method.

If, for example, a condition of the surface of a roadway determined with the method does not correspond to a measured local outside temperature, a season, a time of day, e.g. day or night, an altitude determined by the date and the geographical position, e.g. northern or southern hemisphere above sea level and / or a local or regional weather report If, for example, the method in a coastal region determines an icy roadway at midday in midsummer, then it can be assumed with a high degree of probability that the method has determined an incorrect state. The result of the method can then be discarded, the sensors can be checked, or the application of the method is suspended until further notice, for example until the sensors have been checked or repaired in a workshop.

The one or more sensor values or additional information and / or roadway properties can also be used for a preselection of reference values for the comparison.

If, for example, a surface of a road section currently being traveled on is known, or its type or properties, reference values for other surfaces can be excluded from the comparison, which reduces the effort for the comparison and the probability of an incorrect result.

In one or more embodiments, the method also comprises linking a determined surface condition with an associated geographic position and transmitting the determined surface condition and the linked geographic position to one or more vehicles located in a certain radius or to an external database.

The geographical position required in some embodiments of the method can be provided, for example, by a navigation system arranged in the vehicle.

The transmission to one or more vehicles located within a certain radius does not necessarily refer to a radius around the location at which a surface condition was determined, but can also refer to the transmission to oncoming vehicles located on the same road section at a later point in time . The limitation to a certain radius is only intended to ensure that there is no transmission to vehicles which are located on a road section of another road in the vicinity.

The transmission to an external database can take place via a cellular network or via receivers of a C2X system placed on the street.

The transmission of the determined surface condition of a roadway section to other vehicles makes it possible to warn vehicles that do not have devices for detecting a surface condition of a bad road condition or dangerous surface conditions of roadway sections. When transferred to a database, such vehicles can call up the information from the database, for example in accordance with a route planned in a navigation system or for a region in which the vehicle is located.

In one or more embodiments of the method in which the light source is arranged on or in the vehicle, the light source illuminates the lane section ahead in the direction of travel. The reflected portions of the light are naturally smaller than with an arrangement of light source and sensor, which are optimally arranged at a fixed angle to one another. Nevertheless, because of the always existing roughness of the surface of the roadway, a certain proportion of the light is reflected back, which can be used for the detection of surface properties of a roadway.

In one or more embodiments of the method, the light source illuminates the lane section with light of a specific polarization. In particular on the surface of water films or layers of ice, the part polarized perpendicular to a plane of polarization is reflected more strongly than the part polarized parallel to the plane of polarization. This effect can also be used to detect layers of ice or water films on road surfaces.

In one or more embodiments of the method in which the lane section is illuminated by the light of vehicles driving ahead or oncoming vehicles, the method also includes the detection of the vehicle model. This information can be used to call up properties of the lighting used in this vehicle model from a database, in particular properties relating to the spectrum of the vehicle lighting. The vehicle model can be identified by means of image recognition, for example, whereby features such as the shape, the distance and the arrangement of the headlights to one another or the outline of the vehicle can be used. The images fed to the image recognition can originate, for example, from a camera which is already available for traffic sign recognition or a lane departure warning. However, the vehicle model can also be determined through vehicle-to-vehicle communication. Properties of the light source can also be transmitted from the vehicle whose light source illuminates the roadway.

A suitable means for detecting light in several discrete wavelengths or wavelength ranges is, for example, a color camera, composes the color images from image points recorded in the primary colors red, green and blue. This color camera can be seen as a minimalistic multispectral sensor.

Cameras that are also sensitive in other wavelength ranges, for example in the near infrared range with a wavelength between 780 nm and 3 µm and / or the ultraviolet range of light with a wavelength between 10 nm and 390 nm, can still detect the material and surface conditions of a roadway improve significantly. The CMOS or CCD sensors used in today's color cameras can often already be used in these wavelength ranges; all that matters is the application of suitable filter layers.

In principle, it is possible to implement at least some of the above-described embodiments of the method using cameras that are already provided on the vehicle. It is therefore possible, for example, to use cameras for traffic sign recognition or for lane departure warning systems, but also cameras that are predominantly oriented downwards, for example to support a parking process by providing corresponding images. Cameras of the latter type are often arranged in the exterior mirrors of vehicles, and their images are combined with those from cameras looking forwards or backwards in order to generate a virtual view of the vehicle from a bird's eye view. Some vehicles are already provided with lighting that illuminates the area next to the vehicle doors or projects a manufacturer's logo onto the floor.

These light sources, whose properties are known and which are located in a favorable spatial arrangement in relation to cameras installed in the exterior mirrors and looking downwards, can also be used to determine the condition of the road surface, albeit only the condition of one below the vehicle located lane section can be determined. If necessary, these light sources have to be modified or supplemented in order to provide illumination at further required discrete wavelengths or wavelength ranges.

A method for real-time determination of a surface condition of a roadway currently being traveled by a vehicle according to a second aspect comprises the emission of sound waves with different frequencies onto a section of the roadway surface. The sound waves can be emitted at discrete frequencies or as noise with a known spectral distribution, for example via a loudspeaker arranged close to the surface. A frequency sweep or chirp can also be used for this method. It is also conceivable to use the rolling noise of the tires. For this purpose, reference spectra made available for certain tire types and tread depths can be used, which were determined for driving on certain road surfaces at different speeds. The tread depth can for example be determined after resetting when fitting new tires on the basis of the distance covered. A change between summer and winter tires can also be taken into account accordingly.

The method according to the second aspect also comprises the recording of sound waves reflected from the section of the road surface with one or more sound sensors. Directional microphones, for example, can be used for this purpose.

The method according to the second aspect further comprises comparing the amplitudes of the sound waves recorded for the road section at the different frequencies with reference values provided for a plurality of surface conditions for a plurality of different road surfaces, the degree of correspondence with one of the reference values having a corresponding probability for the Indicates the presence of an associated road surface and surface condition. In this aspect, instead of optical reflection spectra, acoustic reflection spectra are used to record the surface condition of a roadway. It is easy to see here that a comparatively smooth and closed layer of ice on a roadway reflects a different spectrum of sound waves than a more open-pored surface of a roadway not covered by ice.

The methods according to the first and the second aspect can also be combined, for example in order to increase the recognition accuracy, for example when two materials are similar in terms of acoustic properties, for example surface hardness, roughness, damping, scattering. In this case, the optical detection can provide further information that provides information about the condition of the surface. The relationships between optical and acoustic detection can be modeled and optimized for machine learning using suitable input parameters.

A method for dynamically influencing a driving dynamics control of a vehicle as a function of a state of a road surface according to a third aspect comprises a real-time determination of the surface state of a vehicle currently traveled lane by means of one or more of the methods described above, or receiving a current state of a currently traveled lane, for example from other vehicles or a database external to the vehicle.

A vehicle dynamics control is to be understood in this context as a control which, by means of targeted interventions in the brake control, engine control, control of steering and / or chassis components, etc., has an influence on a currently maximum possible acceleration, deceleration, maximum speed and / or speed the change in the steering angle, etc., takes. The vehicle dynamics control can be implemented in a single control device, or in a plurality of control devices that each control one or more of the components mentioned above. A vehicle dynamics regulation can also be controlled or achieved in a summarized manner by a vehicle stability system (ESP system).

The method accordingly comprises the activation of the one or more control units that implement the vehicle dynamics control, or the corresponding control of an ESP system in order to achieve one of the effects listed in the following, not closed list, for example limiting a maximum for one Vehicle acceleration permissible torque on one or more wheels, automatic influencing of differentials on one or more axles of the vehicle, in particular the complete or partial locking of the differentials, the limitation of a maximum speed that can be reached, the reduction of a current speed to one depending on the condition of the road surface adjusted maximum value, or the limitation of the maximum speed of the change in the steering angle, for example by actively counter-holding by means of an electric power steering or by reducing the steering assistance. It is also possible to influence the intervention and / or response behavior of the ESP system of a vehicle as a function of a detected surface condition, the ESP system then correspondingly activating further control devices that implement the vehicle dynamics control. It is also conceivable to use control of an electric power steering system to steer the vehicle into an area of the roadway that has more favorable properties for driving on, depending on a recognized state of a surface. For example, in the case of a ruts recognized by the method according to the first aspect, which is partially filled with water, ice or snow, an automatic steering intervention can lead the vehicle out of the ruts into a possibly dry area or area located next to the ruts where no closed water film has formed. The steering intervention naturally takes place within the framework of the available lane width, taking into account the width of the vehicle, and also taking into account the presence of other road users.

In one embodiment of the method according to the third aspect, properties of the tires of the vehicle and of the vehicle drive are taken into account when influencing the vehicle dynamics control, that is to say whether the vehicle is driven on one axle or on all axles. The method accordingly includes receiving properties of the tires of the vehicle and data describing the vehicle drive.

In the above-described method for detecting a surface condition of a roadway, sensor data from the vehicle dynamics control can be used to improve the reference values. If, for example, the visual or acoustic detection of the current surface condition indicates that there is no slippery road surface, but the slip control or ESP must intervene, then the properties determined for this section of the road by optical or acoustic detection can be re-classified with the properties actually determined when driving on to improve the reliability of the analysis. This can be done in the vehicle itself by an artificial intelligence or an entity set up for machine learning, which has the advantage that the vehicle's own sensors are better coordinated with one another, or in corresponding external entities that implement an artificial intelligence or machine learning. The result of the recursive improvement by the external instances can also be made available to other vehicles, with improved references or parameters of internal instances of machine learning or artificial intelligence also being able to be shared with other vehicles or a central database.

The reference values or reference patterns that are always required in the methods described above can be generated in advance by a large number of measurements under controlled and defined conditions. For this purpose, particularly precise measuring devices are used, the precision of which goes far beyond that of the sensors installed in the vehicles. In order to generate a manageable number of reference values or reference patterns from the large number of measurements, methods for machine learning or artificial intelligence can be used. It is also conceivable to adjust the reference values or reference patterns regularly. This can be determined by vehicles while driving Surface conditions of road sections and the associated values of the sensors used for detection can be fed back to the processes for machine learning or the artificial intelligence. As a result, among other things, the influence of the sensors that are usually comparatively less precise in the vehicles can be gradually reduced.

In addition to determining whether a road surface is covered by a film of water or a layer of ice, or whether de-icing agents or blunting agents have already been applied, the methods described above can also be used to detect liquid or solid hazardous substances on the road surface. Reference values for the different reflection or absorption properties of chemical substances for light at different wavelengths can also be provided for this purpose. Corresponding devices can be provided, for example, in vehicles used by the fire service or the police.

A detection of oil films on roadways is also possible with the methods described above. If an oil film is detected on a roadway, information can automatically be sent to a service that will remove or neutralize the oil film or clean the road.

With the arrangement of devices according to the invention for the detection of surface conditions on vehicles that travel on certain specified routes in regular service, a needs-based street cleaning can also be triggered for these routes.

It is also possible to use one or more of the methods described above to determine road damage and their geographical position, and to transfer these to a database. For example, repairs to road pavements often have a slightly different surface quality than the rest of the road, which can easily be determined using the methods described above. If such a “patch” is detected, a picture can also be taken and sent to a database. An authority charged with the maintenance of roads can read the information about road damage from the database for a change, especially a deterioration in the "patch", and take and coordinate suitable measures. The position of cracks in the road surface or of potholes can also be determined in this way and transferred to the database. If no damage to the road surface is entered in the database for a certain position, it can be assumed that the damage is new. Expediently, data on the properties of the camera system with which the image was recorded are transmitted together with the image in order to enable a corresponding perspective rectification of the camera image. When road damage is detected, sensor data from the vehicle's wheel suspension or acoustic recordings from a microphone can also be used, which have corresponding characteristics for certain road damage.

• 1 ein stark vereinfachtes Flussdiagramm eines erfindungsgemäßen Verfahrens gemäß dem ersten oder zweiten Aspekt,
• 2 eine exemplarische Darstellung des Spektrums der Sonneneinstrahlung außerhalb der Atmosphäre,
• 3 eine exemplarische Darstellung der Durchlässigkeit der Atmosphäre über das Spektrum der Sonneneinstrahlung,
• 4 eine exemplarische Darstellung des Reflexionsgrads unterschiedlicher typischer Fahrbahnmaterialien,
• 5 eine exemplarische Darstellung des Reflexionsgrads unterschiedlicher Beläge auf Fahrbahnoberflächen,
• 6 eine exemplarische Darstellung des Reflexionsgrads von Wasser im Vergleich zu dem von Fahrbahnmaterialien,
• 7 eine erste schematische und stark vereinfachte Anordnung einer Lichtquelle und eines Sensors zur Echtzeitbestimmung eines Oberflächenzustands einer von einem Fahrzeug momentan befahrenen Fahrbahn,
• 8 eine zweite schematische und stark vereinfachte Anordnung einer Lichtquelle und eines Sensors zur Echtzeitbestimmung eines Oberflächenzustands einer von einem Fahrzeug momentan befahrenen Fahrbahn,
• 9 eine dritte schematische und stark vereinfachte Anordnung einer Lichtquelle und eines Sensors zur Echtzeitbestimmung eines Oberflächenzustands einer von einem Fahrzeug momentan befahrenen Fahrbahn,
• 10 eine vierte schematische und stark vereinfachte Anordnung einer Lichtquelle und eines Sensors zur Echtzeitbestimmung eines Oberflächenzustands einer von einem Fahrzeug momentan befahrenen Fahrbahn, und
• 11 eine fünfte schematische und stark vereinfachte Anordnung einer Lichtquelle und eines Sensors zur Echtzeitbestimmung eines Oberflächenzustands einer von einem Fahrzeug momentan befahrenen Fahrbahn.

Exemplary configurations of the invention are described below with reference to the accompanying drawings. In the drawing shows

• 1 a greatly simplified flow diagram of a method according to the invention according to the first or second aspect,
• 2 an exemplary representation of the spectrum of solar radiation outside the atmosphere,
• 3 an exemplary representation of the permeability of the atmosphere across the spectrum of solar radiation,
• 4th an exemplary representation of the degree of reflection of different typical road materials,
• 5 an exemplary representation of the degree of reflection of different pavements on road surfaces,
• 6th an exemplary representation of the degree of reflection of water compared to that of road materials,
• 7th a first schematic and greatly simplified arrangement of a light source and a sensor for real-time determination of a surface condition of a roadway currently being driven on by a vehicle,
• 8th a second schematic and greatly simplified arrangement of a light source and a sensor for real-time determination of a surface condition of a roadway currently being used by a vehicle,
• 9 a third schematic and greatly simplified arrangement of a light source and a sensor for real-time determination of a surface condition of a roadway currently being used by a vehicle,
• 10 a fourth schematic and greatly simplified arrangement of a light source and a sensor for real-time determination of a surface condition of a roadway currently being driven on by a vehicle, and
• 11 a fifth schematic and greatly simplified arrangement of a light source and a sensor for real-time determination of a surface condition of a roadway currently being used by a vehicle.

Identical or similar elements are identified by the same reference symbols in the figures.

1 shows a greatly simplified flow diagram of a method according to the invention 100 for real-time determination of a surface condition of a roadway currently being driven on by a vehicle according to the first or second aspect. In step 102 the light reflected from a surface of a lane section illuminated by a light source with properties known for the discrete wavelengths or wavelength ranges is optically detected. In step 104 the ratios of light incident on the road surface and light reflected at the multiple discrete wavelengths or wavelength ranges are determined, and in step 108 with in step 106 for a multitude of surface conditions of a multitude of different road surfaces provided reference values of the ratios of incident and reflected light at the several discrete wavelengths or wavelength ranges. The degree of correspondence between the ratios of incident and reflected light with the corresponding reference values indicates a probability of the presence of a specific road surface and surface condition.

2 shows an exemplary representation of the spectrum of solar radiation outside the earth's atmosphere at wavelengths between approximately 480 nm and 2400 nm, as an example of known properties of a light source that can be used for the method according to the invention. The earth's atmosphere sometimes has very different permeabilities for different wavelengths, so that on the ground, i.e. on the surface of a roadway, not all wavelengths are present in the same proportions to one another.

3 shows an exemplary representation of the permeability of the atmosphere across the spectrum of solar radiation in dry air without cloud cover approximately at sea level. A low permeability or strong absorption between 1300 nm and 1500 nm wavelength and between 1800 nm and 2000 nm wavelength can be clearly seen. If different surface conditions of roadways show particularly significant differences in these wavelength ranges, corresponding lighting must also be provided in daylight. 2 and 3 are approximately aligned with one another with respect to the wavelengths indicated on the abscissa, so that an assessment of the radiation energy actually hitting the ground under the indicated atmospheric conditions is facilitated.

4th shows an exemplary representation of the degree of reflection of different typical roadway materials, in the figure for concrete, gravel or gravel and asphalt over a wavelength range of approx. 450 nm to 2500 nm.

The clearly different values of the reflection for all three materials at wavelengths in the range between 600 nm and about 1250 nm can be clearly seen. In this wavelength range, the intensity of the solar radiation arriving on the ground is still comparatively high, see 2 and 3 so that a strong signal can be expected.

5 shows an exemplary representation of the degree of reflection of different pavements on road surfaces in a wavelength range from approx. 400 nm to 2500 nm. Here it is easy to see that especially at wavelengths above 700 nm the differences between frost, fine grain snow , Snow of medium grain size (medium grain snow) and snow of large grain size (coarse grain snow) sometimes significant differences in the degree of reflection occur. Compared to the significantly lower degrees of reflection of concrete, gravel or gravel and above all asphalt across all wavelengths, it is easy to see that a road surface made of these materials that is covered by a layer of frost or snow also differs at wavelengths below 700 nm clearly differs from a free surface in terms of its degree of reflection. 4th and 5 are approximately aligned with one another with respect to the wavelengths indicated on the abscissa in order to facilitate the comparison of the degrees of reflection.

6th shows an exemplary representation of the degree of reflection of water compared to that of road materials. The upper part of the figure corresponds to this 4th . Compared to all three exemplary roadway materials, water has a comparatively low degree of reflection over all wavelengths, so that a largely closed water layer, which, for example, entails the risk of aquaplaning, can be easily detected over a large wavelength range. The ones in the 6th The graphs shown are approximately aligned with one another with respect to the wavelengths indicated on the abscissa in order to facilitate the comparison of the reflectivities.

7th shows a first schematic and greatly simplified arrangement of a light source 700 and a sensor 702 for real-time determination of a surface condition of a vehicle 704 currently used lane 706 . In the figure are the light source 700 and the sensor 702 For example. Arranged in or on an outside mirror not shown in the figure. sensor 702 can be, for example, a downward-facing camera arranged in or on the exterior mirror, which is used to generate a virtual bird's eye view and which covers the area to the side of the vehicle. Light source 700 In addition to illuminating the road surface to identify its condition, it can also be used to illuminate the area next to the vehicle, which makes it easier for a driver or passenger to identify the ground next to the vehicle. In addition, the light source can be used to project a manufacturer's logo or the like onto the background.

8th shows a second schematic and greatly simplified arrangement of a light source 700 and a sensor 702 for real-time determination of a surface condition of a vehicle 704 currently used lane 706 . In the figure are light sources 700 and sensor 702 mounted underneath the vehicle, causing the sensor 702 falling extraneous light is reduced, which can lead to higher accuracy.

9 shows a third schematic and greatly simplified arrangement of a light source 700 and a sensor 702 for real-time determination of a surface condition of a vehicle 704 currently used lane 706 . Light source 700 is in this figure by the headlights of the vehicle 704 formed, which illuminate the area of the road ahead in the direction of travel. The light cone is indicated in the figure by the solid lines emanating from the headlights. sensor 702 is formed by one or more cameras, which are available, for example, for a lane departure warning function or traffic sign recognition. camera 702 also records that from the headlights, among other things 700 illuminated area of the roadway, indicated in the figure by the dashed arrows.

10 shows a fourth schematic and greatly simplified arrangement of a light source 700 and a sensor 702 for real-time determination of a surface condition of a vehicle 704 currently used lane 706 . Light source 700 in this example includes the headlights of an oncoming vehicle 708 which is also the lane of the vehicle 704 illuminate. The spectral properties of the light source 700 are the sensor 702 in vehicle 704 not known in advance, so the vehicle can 708 this over a wireless connection 710 to the vehicle 704 to calibrate the sensor accordingly. For this purpose, versions of vehicle-to-vehicle communication means according to different standards can be used. The spectral properties of a light source 700 can in a corresponding memory of vehicle 708 be saved. sensor 702 , in the example again a camera, which can also be used for a lane departure warning function or traffic sign recognition, detects the light source 700 illuminated area and evaluates the spectral properties of the light reflected from the road surface in comparison to those of the vehicle 708 transmitted spectral properties of the light source 700 to determine the condition of the road surface.

11 shows a fifth schematic and greatly simplified arrangement of a light source 700 and a sensor 702 for real-time determination of a surface condition of a vehicle 704 currently used lane 706 . The situation is similar to that in 10 shown, with no communication between vehicles in this example 704 and 708 consists. camera 702 can do this in addition to that of light source 700 illuminated area of the roadway 706 also the light source 700 record it yourself and use the directly received spectrum as a reference. Alternatively, there can be from the camera 702 captured image of the vehicle 708 can also be used to determine the vehicle type by means of image recognition, and to retrieve properties from a database for headlights used in the recognized vehicle type.

Claims (14)

A method (100) for real-time determination of a surface condition of a roadway currently being driven on by a vehicle, comprising: - optical detection (102), in several discrete wavelengths or wavelength ranges, of the surface illuminated by a light source with properties known for the discrete wavelengths or wavelength ranges Lane section of reflected light, - determining (104) the ratios of light incident on the road surface and reflected light at the multiple discrete wavelengths or wavelength ranges to one another, - providing reference values of the ratios of incident and reflected light at the multiple discrete wavelengths or wavelength ranges to one another for a large number of surface conditions of a large number of different road surfaces, and - discretely comparing the ratios of incident and reflected light determined for the road section in the case of the plurality en wavelengths or wavelength ranges with the for the A large number of surface conditions for a large number of different road pavements provided reference values, the degree of correspondence between the ratios of incident and reflected light with the corresponding reference values indicating a probability of the presence of a specific road pavement and surface condition. Method (100) according to Claim 1 , further comprising: - determining the intensities of the light incident on the road surface (706) from the light source (700) at the plurality of discrete wavelengths or wavelength ranges. Method (100) according to Claim 1 , wherein the light source (700) is arranged on the vehicle (104) and is configured to illuminate the roadway section one after the other with light in one of the plurality of discrete wavelengths or wavelength ranges, and wherein the method further comprises: - synchronizing the optical detection with the Changing the wavelength or the wavelength range of the light source, and superimposing the detected road sections illuminated with light of different wavelengths or wavelength ranges, taking into account a speed of the vehicle present during the detection. The method (100) according to one or more of the preceding claims, wherein the comparing further comprises: - Receiving one or more sensor values or additional information from the incomplete group including a local temperature, a date, a time of day, a geographical position, a local or regional weather report, and / or - Receiving static or slowly changing roadway properties from a database, and - Checking the plausibility of the result of the comparison using the sensor values, the additional information and / or the received roadway properties, and / or - Use of the sensor values, the additional information and / or the received roadway properties to select reference values for the comparison. The method (100) according to one or more of the preceding claims, further comprising: - Linking a determined surface condition with an associated geographical position, and - Transmission of the determined surface condition and the linked geographical position to one or more vehicles located in a certain radius or to an external database. Method for real-time determination of a surface condition of a roadway currently being driven on by a vehicle, comprising: - Radiation of sound waves with different frequencies onto a section of the road surface, - Recording the sound waves reflected from the section of the road surface with one or more sound sensors, - Compare the amplitudes of the sound waves recorded for the road section at the different frequencies (frequency analysis) with reference values provided for a large number of surface conditions for a large number of different road surfaces, the degree of correspondence with one of the reference values having a corresponding probability of the presence of an associated road surface and Surface condition. Method for real-time determination of a surface condition of a roadway currently being used by a vehicle according to one of the Claims 1 to 5 , comprising: - Radiation of sound waves with different frequencies onto a section of the road surface, - Recording of the sound waves reflected by the section of the road surface with one or more sound sensors, - Comparing the amplitudes of the sound waves recorded for the road section at the different frequencies (frequency analysis) with reference values provided for a multitude of surface conditions for a multitude of different road surfaces, the degree of correspondence with one of the reference values indicating a corresponding probability of the presence of an associated road surface and surface condition. Procedure according to Claim 6 or 7th wherein radiating the sound waves comprises radiating noise of known spectrum, chirp, or discrete frequencies. Procedure according to Claim 6 or 7th wherein the emission of the sound waves comprises the rolling noise of the rolling tires, and wherein the reference values are selected for the particular speed being driven and properties of the type of tire used on the vehicle. Method for dynamically influencing a driving dynamics control of a vehicle as a function of a condition of a road surface, comprising: Detecting a state of a surface of a roadway currently being driven on in real time by means of a method according to one of the Claims 1 - 9 , or receiving a current state of a surface of a currently traveled lane, and - actuation of the vehicle dynamics control, depending on the state of the surface of the currently traveled lane, for: - limiting a maximum permissible torque for a vehicle acceleration on one or more wheels, - automatic Influencing differentials on one or more axles, - limiting a maximum speed, - reducing a speed to a maximum value adapted to the condition of the road surface, - changing the response and / or intervention behavior of an ESP system, and / or - limiting a maximum speed the change in the steering angle. Device for real-time determination of a surface condition of a roadway (106) currently being driven on by a vehicle (104) with at least one light source (700) and a sensor (702) as well as one or more processors and associated memory, the processor being configured to carry out the method according to one of the Claims 1 - 9 execute. Land vehicle with a device according to Claim 11 . Computer program product, comprising instructions which, when the program is executed by a computer, cause the program to run, the method according to one of the Claims 1 - 10 execute. Computer-readable data carrier on which the computer program product is after Claim 13 is stored.

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