Method and apparatus for determining a degree of wetness of a road
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-18
- Publication Date
- 2026-04-08
AI Technical Summary
Existing methods for determining the degree of wetness of a road surface are not precise or reliable enough, particularly for automated and autonomous vehicles, as they often require additional sensors and are costly.
A method and device using a microphone arrangement on a vehicle to detect noise level differences between front and rear acoustic signals, correlated with the vehicle's driving speed, to determine the road's wetness level, eliminating the need for moisture sensors and leveraging existing microphones for emergency vehicles.
This approach provides a precise and cost-effective means to determine road wetness, enhancing the reliability of longitudinal and lateral control adaptations based on road grip and environmental detection, with optional validation from optical rain sensors for increased accuracy.
Smart Images
Figure EP2024060637_05122024_PF_FP_ABST
Abstract
Description
[0001] Method and device for determining the wetness level of a road surface
[0002] The invention relates to a method for determining the degree of wetness of a roadway according to the preamble of claim 1.
[0003] The invention further relates to a device for determining a degree of wetness of a roadway according to the preamble of claim 6.
[0004] DE 102 59 979 A1 discloses a method for determining road conditions during the driving operation of a motor vehicle. A portion of the sound generated when a vehicle tire rolls on a roadway is detected, and a sound level signal describing this sound is generated using the detected sound. Furthermore, a frequency signal describing the sound level signal is determined. This frequency signal is divided into two sub-ranges by a cutoff frequency, each of which is assigned to a corresponding frequency band. For two frequency bands from the assigned sub-range of the frequency signal, an intensity value is determined, which is representative of the sound intensity present in a frequency band.Furthermore, an intensity ratio is calculated by dividing a first intensity value of a first frequency band by a second intensity value of a second frequency band, whereby the intensity ratio is used to determine the road condition. The road condition is determined as the thickness of a water film on the road surface.
[0005] Furthermore, DE 42 13221 A1 discloses a method for detecting the wetting of a road surface with a liquid, wherein the road surface is driven over by a vehicle whose wheels roll on the road. The method comprises the following steps: - detecting a splashing water noise or a rolling noise of a wheel of the motor vehicle using a microphone arranged on the motor vehicle and generating an output signal corresponding to the detected noise,
[0006] - Bandpass filtering of the output signal to separate a frequency range characteristic of the wetting of the road surface,
[0007] - RMS value formation of the filtered output signal,
[0008] - Low-pass filtering of the effective value,
[0009] - Assigning the effective value to a value of the wetting of the road surface while compensating for the influence of variables other than wetting on the effective value and
[0010] - Output this value.
[0011] From DE 102004 016 900 A1 a method for determining a water film height on a road surface is known, wherein it is provided that sound emissions at the front wheel and the rear wheel are recorded and compared with each other by means of microphones and that the water film height is determined from the signal difference.
[0012] DE 102019 203 191 B3 discloses a method for detecting a wet road surface using an acoustic sensor system. It involves arranging ultrasonic transducers in the area of the front and rear bumpers and determining their noise levels. In this method, the noise levels of the ultrasonic transducers are correlated with additional data acquired by a sensor system for detecting road irregularities, so that a consistently wet road surface can be distinguished from one with water-filled bumps.
[0013] From DE 102019 218492 A1 a method is known in which the wetness values of a road surface are recorded acoustically at the front, rear and sides of the vehicle using ultrasonic sensors and, depending on the wetness values, a moving object in the vehicle's surroundings is detected.
[0014] From DE 102020 216 574 A1 a method for determining the wetness value of a road surface is known, wherein capacitive sensors are provided at the front and rear of the vehicle, the frequency change of which is used to determine wetness parameters.
[0015] The invention is based on the object of providing a novel method and a novel device for determining the wetness level of a roadway. This object is achieved according to the invention by a method having the features specified in claim 1 and by a device having the features specified in claim 6.
[0016] Advantageous embodiments of the invention are the subject of the subclaims.
[0017] In a method for determining the wetness level of a road surface based on acoustic signals, these are recorded by means of a microphone arrangement arranged on a vehicle driving along the road.
[0018] According to the invention, while the vehicle is traveling on the road, front acoustic signals are recorded by means of at least one front external microphone arranged in the region of a front end of the vehicle, and rear acoustic signals are recorded by means of at least one rear external microphone arranged in the region of a rear end of the vehicle. Furthermore, while the vehicle is traveling on the road, an evaluation determines a noise level difference between the front acoustic signals and the rear acoustic signals. The degree of wetness of the road is determined from a predefined value matrix based on the noise level difference and the current driving speed of the vehicle.
[0019] For automated, especially highly automated or autonomous vehicles, it is important to detect the wetness of the road surface in order to adapt longitudinal and / or lateral control to a wetness-dependent view of environmental detection sensors and a wetness-dependent road grip.
[0020] This method enables a particularly precise and reliable determination of the wetness of the road surface. Particularly advantageously, microphones already provided on the vehicle for detecting special acoustic signals from emergency vehicles can be used to detect the acoustic signals. This eliminates the need for wetness sensors, for example, those located in a vehicle's wheel arch, resulting in a particularly low material and cost requirement for implementing the method.
[0021] In one possible embodiment of the method, the value matrix is determined in vehicle-specific driving tests for different wetness levels and different driving speeds. Noise level differences between the acoustic signals recorded by the external microphones are determined for different wetness levels at different driving speeds and plotted in the value matrix. Such a value matrix enables a particularly simple and reliable determination of the wetness of the road surface during vehicle operation.
[0022] In another possible embodiment of the method, the amount of spray is first determined based on the noise level difference. The degree of wetness of the road surface is derived from the amount of spray, with the wetness being inferred to be increasing with increasing spray amount. Since the noise level at the front external microphone increases only slightly with increasing spray amount, while the noise level at the rear external microphone increases significantly, spray, as a parameter directly dependent on the wetness of the road surface, is particularly suitable for simple, precise, and reliable detection of the wetness of the road surface.
[0023] In a further possible embodiment of the method, noise level differences between the acoustic signals recorded by the external microphones are determined in the value matrix for different degrees of wetness and different driving speeds of the vehicle as a function of a quantity of spray dependent on the degree of wetness and are plotted in the value matrix, so that a simple determination of the quantity of spray from the matrix and, consequently, a simple determination of the degree of wetness from the determined quantity of spray is possible.
[0024] In another possible embodiment of the method, the wetness level determined based on the noise level difference is checked for plausibility using data obtained using an optical rain sensor. Such a rain sensor, which is often already provided for rain-sensor-controlled control of a windshield wiper in the area behind a vehicle's windshield, can further increase the reliability of determining the wetness level.
[0025] The device for determining the wetness level of a roadway based on acoustic signals detected by a microphone arrangement arranged on a vehicle traveling on the roadway comprises, according to the invention, at least one front external microphone arranged in the region of a front end of the vehicle for detecting front acoustic signals while the vehicle is traveling on the roadway, and at least one rear external microphone arranged in the region of a rear end of the vehicle for detecting rear acoustic signals while the vehicle is traveling on the roadway. Furthermore, the device comprises an evaluation unit for determining a noise level difference between the front acoustic signals and the rear acoustic signals and for determining the wetness level of the roadway from the noise level difference and a current driving speed of the vehicle from a predetermined value matrix.
[0026] This device enables particularly precise and reliable determination of the wetness of the road surface. Particularly advantageously, microphones already provided on the vehicle for detecting special acoustic signals from emergency vehicles can be used to detect the acoustic signals. This eliminates the need for wetness sensors, for example, those located in a wheel arch of the vehicle, resulting in particularly low material and cost requirements for the implementation of the device.
[0027] Embodiments of the invention are explained in more detail below with reference to drawings.
[0028] It shows:
[0029] Fig. 1 shows schematically a plan view of a vehicle on a roadway and
[0030] Fig. 2 shows a schematic block diagram of a device for determining the wetness level of a road surface.
[0031] Corresponding parts are provided with the same reference numerals in all figures.
[0032] Figure 1 shows a plan view of a vehicle 1 traveling on a wet roadway FB. Figure 2 shows a block diagram of a possible embodiment of a device 2 for determining a wetness level NG of the roadway FB, wherein the vehicle 1 includes the device 2.
[0033] The device 2 comprises a microphone arrangement 3 with two external microphones 3.1, 3.2, wherein one of the external microphones 3.1 is a front external microphone 3.1 arranged in the region of a front end of the vehicle 1, and an external microphone 3.2 is a rear external microphone 3.2 arranged in the region of a rear end of the vehicle 1. For example, the front external microphone 3.1 is arranged in the region of a front bumper or a front bumper fascia, and the rear external microphone 3.2 is arranged in the region of a rear bumper or a rear bumper fascia.
[0034] The device 2 further comprises an evaluation unit 4, a value matrix 5 coupled to the evaluation unit 4 or included therein and a speed sensor 6 which supplies the evaluation unit 4 with a current driving speed v of the vehicle 1.
[0035] In embodiments of the device 2 not shown in detail, this can comprise further external microphones 3.1, 3.2, wherein, for example, two front external microphones 3.1 are arranged in the region of the front end of the vehicle 1 and two rear external microphones 3.2 are arranged in the region of the rear end of the vehicle 1.
[0036] To determine the degree of wetness NG of the roadway FB, front acoustic signals S1 are recorded by the front external microphone 3.1 and rear acoustic signals S2 are recorded by the rear external microphone 3.2 while the vehicle 1 is traveling on the roadway FB.
[0037] Spray detection is performed using a delta analysis of the two acoustic signals S1, S2, performed by the evaluation unit 4. As the amount of spray increases, the noise level at the front external microphone 3.1 increases only slightly. In contrast, the noise level at the rear external microphone 3.2 increases significantly with increasing amount of spray. Thus, spray, as a parameter directly dependent on the wetness level NG of the road surface FB, allows the wetness level NG of the road surface FB to be derived from this.
[0038] Since the amount of spray on vehicle 1 depends on its driving speed v, the degree of wetness NG is determined retroactively from the amount of spray as a function of the current driving speed v.
[0039] The wetness level NG is determined by comparing the amount of spray determined at the current driving speed v with the values stored in the value matrix 5. The value matrix 5 is determined in particular in driving tests on a vehicle-specific basis for a respective vehicle 1 or a respective vehicle type, for example a sedan, station wagon, off-road vehicle, van, sport utility vehicle, etc., for different wetness levels NG and different driving speeds v, whereby for different wetness levels NG at different driving speeds v, noise level differences between the acoustic signals S1, S2 recorded by the external microphones 3.1, 3.2 are determined and plotted in the value matrix 5. The noise level differences are also determined as a function of the respective amount of spray and plotted in the value matrix 5.
[0040] During operation of the vehicle 1, a value of a quantity of spray corresponding to a pair of values consisting of the determined noise level difference and the current vehicle speed v is read from the value matrix 5 thus generated, and the wetness degree NG of the road surface FB dependent thereon is determined from this value.
[0041] Different levels of spray quantity can be stored in the value matrix. These levels divide the spray quantity into, for example, "no spray," "light spray," "moderate spray," and "high spray." Depending on these levels, the resulting wetness level (NG) can also be classified into "dry," "light," "medium," and "high."
[0042] For example, value matrix 5 is generated as a 5x4 matrix for five different driving speeds v of vehicle 1 and the four degrees of spray quantity: "no spray," "light spray," "medium spray," and "high spray." The driving speeds v are, for example, 20 km / h, 40 km / h, 60 km / h, 80 km / h, and 100 km / h. Deviating from this, more driving speeds v and / or finer subdivisions with small intervals between the driving speeds v are also possible. A maximum driving speed v for value matrix 5, for example, is a maximum speed permitted in automated ferry operation. A different classification of the degrees of spray quantity is also possible.
[0043] If the value matrix 5 is used during ferry operation of vehicle 1 for the above-described determination of the wetness level NG from the current driving speed v and the determined amount of spray, the following relationships between the current driving speed v, the determined respective amount of spray and the wetness level NG result for the example described above: Driving speed v=20 km / h and wetness level NG "light": "light spray"; Driving speed v=60 km / h and wetness level NG "light": "light spray"; Driving speed v=100 km / h and wetness level NG "light": "medium spray";
[0044] Driving speed v=20 km / h and wetness level NG "medium": "light spray": Driving speed v=60 km / h and wetness level NG "medium": "medium spray": Driving speed v=100 km / h and wetness level NG "medium": "high spray";
[0045] Driving speed v=20 km / h and wetness level NG "high": "medium spray"; driving speed v=60 km / h and wetness level NG "high": "high spray"; driving speed v=100 km / h and wetness level NG "medium": "high spray";
[0046] As can be seen in the example described, different amounts of spray can be assigned different wetness levels NG at the same driving speed v. In this case, one possible embodiment provides that the higher wetness level NG is assumed during automated ferry operation, and that automated ferry operation is carried out depending on the higher wetness level NG. If the driving speed v is reduced in such a case, for example, if the driving speed v is reduced from 100 km / h to 60 km / h with "high spray," it becomes clear that the wetness level NG is "high."
[0047] In a further possible embodiment, the evaluation unit 4 is additionally coupled to an optical rain sensor 7, wherein the wetness level NG determined from the noise level difference based on the previous description is checked for plausibility with data D determined by the optical rain sensor 7. Such a rain sensor 7 is already used, for example, in vehicle 1 for rain-sensor-controlled activation of a windshield wiper and is arranged, for example, in the area behind a windshield of the vehicle 1. By means of such a plausibility check, the reliability of the determination of the wetness level NG can be further increased.
[0048] In a possible embodiment of the device 2, acoustic signals S1, S2 detected by means of the external microphones 3.1, 3.2 are used, regardless of the number of external microphones 3.1, 3.2, for example in addition to detecting special acoustic signals from emergency vehicles present in an environment of the vehicle 1.
Claims
Patent claims 1. Method for determining a degree of wetness (NG) of a roadway (FB) based on acoustic signals (S1, S2) which are detected by means of a microphone arrangement (3) arranged on a vehicle (1) traveling on the roadway (FB), characterized in that during a journey of the vehicle (1) on the roadway (FB) - front acoustic signals (S1) are detected by means of at least one front external microphone (3.1) arranged in the region of a front end of the vehicle (1), - rear acoustic signals (S2) are detected by means of at least one rear external microphone (3.2) arranged in the region of a rear end of the vehicle (1), - in an evaluation, a noise level difference between the front acoustic signals (S1) and the rear acoustic signals (S2) is determined and - the degree of wetness (NG) of the road surface (FB) is determined from a predetermined value matrix (5) based on the noise level difference and a current driving speed (v) of the vehicle (1).
2. Method according to one of the preceding claims, characterized in that the value matrix (5) is determined in driving tests vehicle-specifically for different degrees of wetness (NG) and different driving speeds (v), wherein for different degrees of wetness (NG) at different driving speeds (v) noise level differences between the acoustic signals (S1, S2) recorded by means of the external microphones (3.1, 3.2) are determined and plotted in the value matrix (5).
3. Method according to claim 1 or 2, characterized in that - based on the noise level difference, an amount of spray is first determined and - the wetness level (NG) of the road surface (FB) is derived from the amount of spray, whereby the wetness level (NG) increases with the amount of spray.
4. Method according to claim 3, characterized in that in the value matrix (5) for different degrees of wetness (NG) and different driving speeds (v) of the vehicle (1) as a function of a quantity of spray dependent on the degree of wetness (NG), noise level differences between the acoustic signals (S1, S2) detected by means of the external microphones (3.1, 3.2) are determined and plotted in the value matrix (5).
5. Method according to one of the preceding claims, characterized in that the degree of wetness (NG) determined on the basis of the noise level difference is checked for plausibility with data (D) determined by means of an optical rain sensor (7).
6. Device (2) for determining a degree of wetness (NG) of a roadway (FB) on the basis of acoustic signals (S1, S2) detected by means of a microphone arrangement (3) arranged on a vehicle (1) traveling on the roadway (FB), characterized by - at least one front external microphone (3.1) arranged in the region of a front end of the vehicle (1) for detecting front acoustic signals (S1) while the vehicle (1) is traveling on the roadway (FB), - at least one rear external microphone (3.2) arranged in the region of a rear end of the vehicle (1) for detecting rear acoustic signals (S2) while the vehicle (1) is traveling on the roadway (FB), - an evaluation unit (4) for determining a noise level difference between the front acoustic signals (S1) and the rear acoustic signals (S2) and for determining the degree of wetness (NG) of the road surface (FB) from the noise level difference and a current driving speed (v) of the vehicle (1) from a given value matrix (5).