Method for determining a temperature of a body panel

Abstract

The invention relates to a method for determining a temperature (T) of a body panel (2) of a motor vehicle (1) by means of an ultrasonic sensor (3) mounted in a concealed manner on the body panel (2), comprising: taking (S1) measurements by means of the ultrasonic sensor (3), in each case comprising emitting an ultrasonic pulse by means of the ultrasonic sensor (3) and determining peaks (9) in an ultrasonic signal profile (10) received by the ultrasonic sensor (3) in response to the emission; comparing (S2) the determined peaks with a plurality of probability distributions (11-13) calibrated in advance for different temperatures (T), which probability distributions indicate, depending on an amplitude (A) of a respective peak (9), a probability (p) that the peak (9) is structure-borne sound, in order to determine one of the probability distributions (11-13) best matching the determined peaks (9); and determining (S3) one temperature (T) of the body panel (2) as the temperature (T) assigned to the probability distribution (11-13) that best matches the determined peaks (9).

Description

[0001] 2023PF00672

[0002] 1

[0003] METHOD FOR DETERMINING THE TEMPERATURE OF A BODY SHEET

[0004] The present invention relates to the field of ultrasonic sensor technology for motor vehicles and more specifically to a method for determining the temperature of a body panel, a control unit for carrying out the proposed method and a motor vehicle with the control unit.

[0005] Motor vehicles can be equipped with ultrasonic sensors that measure the vehicle's surroundings by emitting ultrasound and receiving reflected ultrasound from the environment. The resulting information about distances to and the location of reflection points in the environment can be provided to a driving or parking assistance system and / or visualized for the driver.

[0006] It is known that such ultrasonic sensors can be concealed and mounted on the inside of a vehicle body panel. In this case, the body panel is acoustically coupled to the vibrating diaphragm of the ultrasonic sensor and itself acts as a diaphragm. However, this presents the problem that the ultrasonic sensor registers not only ultrasonic echoes from the vehicle's surroundings but also structure-borne sound echoes reflected back from the body panel. The intensity of the structure-borne sound echo is generally temperature-dependent, as the damping properties of the body panel are strongly temperature-dependent.

[0007] In this context, DE 10 2019 123 822.6 proposes a method for computational noise compensation in which real-time environmental information detected by, for example, a concealed ultrasonic sensor is subtracted from reference environmental information detected by the ultrasonic sensor in order to computationally compensate for the disruptive structure-borne noise. The temperature dependence of structure-borne noise is taken into account in 2023PF00672.

[0008] 2. This is taken into account by re-acquiring the reference environmental information when the temperature changes. However, it is not specified how the temperature change is detected.

[0009] US Patent 2020 / 0033473A1 discloses a method for operating an ultrasonic sensor concealed on a vehicle component, in which a threshold is used to suppress interference signals. The threshold is adjusted depending on the instantaneous properties of the vehicle component, in particular depending on the temperature of the vehicle component as measured by a temperature sensor.

[0010] Against this background, one object of the present invention is to improve the computational compensation of noise and, in particular, the determination of the temperature of a vehicle component.

[0011] According to a first aspect, a method for determining the temperature of a motor vehicle body panel using an ultrasonic sensor concealed on the body panel is proposed. The method comprises: a) performing a number of measurements with the ultrasonic sensor, each comprising emitting an ultrasonic pulse with the ultrasonic sensor and determining a number of peaks in an ultrasonic signal waveform received by the ultrasonic sensor in response to the emission of the ultrasonic pulse;b) Comparing the peaks determined in step a) with several probability distributions, pre-calibrated for different temperatures, which, depending on at least one amplitude of each peak, indicate a probability that the peak represents structure-borne sound reflected back from the body panel, in order to determine which of the several probability distributions best matches the peaks determined in step a); and c) Determining a temperature of the body panel as the temperature that corresponds to the probability distribution determined in step b) that best matches the identified peaks. 2023PF00672;

[0012] 3

[0013] Accordingly, the temperature of the body panel can be determined or estimated by means of an ultrasonic measurement using the ultrasonic sensor that is already available, and the temperature sensor used for this purpose in the prior art can advantageously be dispensed with.

[0014] The motor vehicle can be, for example, a passenger car or a commercial vehicle, such as a truck, a bus or a tractor.

[0015] The body panel can be any component of the outer shell of the motor vehicle made of sheet metal, such as a fender panel, a side sill, a door panel, or the like.

[0016] The ultrasonic sensor can, for example, comprise an ultrasonic membrane, a piezoelectric element attached to the inside of the ultrasonic membrane, and a control circuit for the piezoelectric element. Controlled by a control device of the vehicle, the control circuit can set the piezoelectric element, and via the piezoelectric element the ultrasonic membrane, into vibration, thereby emitting ultrasonic signals into the surroundings of the vehicle, but also into the bodywork.When a reflected signal component of such an emitted ultrasound signal from the environment (ambient sound) and / or from the body sheet (structure-borne sound) reaches the ultrasound membrane again, this reflected signal component excites the ultrasound membrane and, via the ultrasound membrane, the piezoelectric element to vibrations, which are converted by the piezoelectric element into an electrical signal, so that the control device can detect a received ultrasound signal profile using the control circuit.

[0017] Concealed mounting of the ultrasonic sensor on the body panel means, in particular, that no opening is provided in the body panel for the ultrasonic membrane of the ultrasonic sensor, but rather that the ultrasonic membrane of the ultrasonic sensor rests against an inner surface of the body panel from the inside. 2023PF00672

[0018] 4 is pressed. It is also conceivable that the piezoelectric element is attached directly to the inside of the body panel and a section of the body panel itself is used as the ultrasonic membrane.

[0019] With such concealed mounting, ultrasound is inevitably emitted not only into the vehicle's surroundings but also into the bodywork, and reflected structure-borne sound from the bodywork is received by the ultrasonic sensor. This means that, due to the concealed mounting of the ultrasonic sensor, the received ultrasonic signal can also contain a structure-borne sound component. Traditionally, attempts were made to dampen and suppress the structure-borne sound component using a butyl material; however, there is a growing trend to reduce the damping and to computationally filter out the structure-borne sound component when the vehicle is operating for obstacle detection in slow-moving or stationary vehicles.

[0020] This means that when the ultrasonic sensor is concealed on the body panel, a butyl damping material or similar can either be omitted or designed in such a way that structure-borne sound components reflected in the body panel can still penetrate to the ultrasonic diaphragm of the ultrasonic sensor. For example, a damping pad with a diameter of only about 10-15 cm can be used.

[0021] A signal waveform (the ultrasound signal waveform) is understood to be a processable and analyzable representation of the corresponding signal (received ultrasound signal component) over a predefined time period. For example, the signal waveform could be a sample of the signal at a suitable sampling frequency, for instance, in the range of a few megahertz. The term "signal waveform" or "ultrasound signal waveform" also encompasses a signal waveform derived from the raw signal waveform, obtained through signal processing. To reduce the processing load, the ultrasound signal waveform can, for example, be based on a resolution of approximately 50 ps to 200 ms, preferably approximately 100 ps. 2023PF00672

[0022] 5 per sampling, downsampled. It is also conceivable to downmix the raw ultrasound signal, for example, in an IQ mixer implemented as a DSP; in this case, the ultrasound signal used in the proposed method can, for example, include the downmixed i-signal and the downmixed q-signal. It is equally conceivable to simply generate an envelope of the raw ultrasound signal. The downsampling and / or downmixing and / or envelope generation can, for example, be performed by the ultrasound sensor before the received ultrasound signal, thus downsampled, downmixed, or envelope-converted, is transmitted to the control device in order to save transmission bandwidth.

[0023] The signal waveform can exist as a signal, for example as an analog or digital signal, i.e. as a signal in transit, or the respective signal waveform can exist as static data (a sequence of samples stored in working memory or the like).

[0024] It should be noted that the ultrasound signal profile can only be recorded for a specific time period of interest, ranging from an initial time after the ultrasound pulse is emitted to a second time after. The initial time can be chosen taking into account a decay time. The second time can be chosen based on the time after which no structure-borne sound echoes are expected. This time can be determined according to t = s * c, where t = time, s = distance to the ultrasound sensor, and c = ultrasonic velocity in sheet metal at the respective temperature, with the distance s being chosen taking into account the dimensions of the body panel.

[0025] A peak in the signal waveform refers to a local maximum in the amplitude of the received ultrasound signal waveform and / or its envelope. That is, a necessary condition for the presence of a peak is, for example, that the amplitude of the sample identified as the peak is higher than the amplitudes of the preceding or subsequent samples of the ultrasound signal waveform. However, further 2023PF00672

[0026] 6

[0027] Criteria such as a minimum height, a minimum width, a shape criterion, a minimum distance since the emission of the ultrasound signal, and the like, are used to actually identify peaks and reduce noise.

[0028] Any functionality suitable as a probability distribution can take as input data from the tip, in particular its amplitude and preferably its position within the ultrasound signal, and output the probability that the tip is structure-borne sound. The probability distribution can be implemented as a parameterizable mathematical model, particularly preferably as a gamma distribution function, with the parameters defined during the pre-calibration. Alternatively, the probability distribution can be in the form of a histogram showing the number of tips measured during pre-calibration for each of several bins, or a similar representation.

[0029] "Pre-calibration" or "preliminary calibration" refers to calibration under controlled conditions, such as in a workshop, development laboratory, or similar environment. Controlled conditions include, in particular, temperature and the absence of obstructions in the ultrasonic sensor's field of view, ensuring that only structure-borne sound is measured during calibration. Further details of the calibration process are described later.

[0030] A probability distribution is particularly "best fitting" if a parameter describing a deviation of a distribution of the peaks determined in step a) from the probability distribution is minimal, i.e. smaller than the corresponding parameter for each of the other pre-calibrated probability distributions.

[0031] The proposed steps are preferably performed by a central control unit of the motor vehicle, which is communicatively connected to the ultrasonic sensor. The steps can also be performed in parallel or sequentially with multiple ultrasonic sensors. The determined temperature can be used when controlling different 2023PF00672

[0032] 7

[0033] Functionalities can be used. For example, an overheating protection warning could be issued to protect vehicle occupants if the temperature exceeds a threshold.

[0034] Particularly preferably, the specific temperature can be used to filter structure-borne noise from the received ultrasonic signal waveform by adjusting a parameter for filtering structure-borne noise depending on the temperature, selecting a temperature-dependent reference signal waveform from among several to be subtracted from the ultrasonic signal waveform, adapting probability functions for distinguishing between structure-borne noise and ultrasonic reflections from the environment to the temperature, and the like. If the distances to and positions of reflection points on obstacles in the vicinity of the vehicle are then determined using the ultrasonic signal waveform filtered in this way depending on the temperature, structure-borne noise can advantageously be filtered out more effectively and the accuracy of obstacle detection improved.

[0035] In this context, "number" means a number of N>1, that is, a number of one or more elements. In contrast, "plurality", "several", and the like mean a plurality of N>1, that is, two or more elements.

[0036] It is understood, however, that the proposed method works better the more measurements are performed, since with an increasing number of measurements the statistical power of the sample advantageously increases and random deviations are increasingly averaged out. In particular, the proposed method for temperature determination implicitly assumes that only structure-borne sound is recorded during a measurement in step a). If an obstacle is present in the field of view of the ultrasonic sensor at this time, peaks in the ultrasonic signal resulting from this obstacle could distort the temperature determination. However, with a sufficiently high number of measurements, such effects become irrelevant. 2023PF00672

[0037] 8

[0038] The expression that a peak "is structure-borne sound reflected back from the body sheet" is intended to describe, in particular, in a concise way, the fact that the occurrence of the peak is due to a reflection of the ultrasonic signal component propagating in the body sheet at a reflection point in the body sheet, such as an edge or a bend thereof, back to the ultrasonic sensor.

[0039] "Determining a temperature" can also be understood as "indirectly measuring the temperature" or as "estimating the temperature".

[0040] According to one embodiment, the pre-calibrated probability distributions indicate the probability that the tip is structure-borne sound, furthermore depending on the time of occurrence of the tip in the received ultrasound signal waveform.

[0041] Accordingly, it is advantageous to achieve an even more precise determination of the temperature and an even more precise obstacle detection.

[0042] This means that it is possible to take into account a situation in which the distribution of the amplitudes of structure-borne sound echoes measured during calibration varies at a given temperature depending on the signal transit time (distance traveled by the ultrasound signal), and / or the sensitivity for the detection of structure-borne sound can be varied depending on the distance, for example to adjust the sensitivity or aggressiveness of the structure-borne sound detection in certain distance ranges.

[0043] This means that the probability distribution can be a function that accepts, as input data, not only the amplitude of each peak but also the time of its occurrence in the received ultrasound signal. The time can be specified as a time interval or as a distance converted according to s=t*c. 2023PF00672

[0044] 9

[0045] According to another embodiment, the pre-calibrated probability distributions are calibrated at the factory on the body panel or on a prototype of the body panel.

[0046] This means that the calibration advantageously does not necessarily need to be performed on the same body panel, but can be carried out on a prototype and then applied to all produced examples of that body panel. The prototype preferably exhibits the same structure-borne sound characteristics as the later production models.

[0047] The plant where the factory calibration takes place can be a plant of an automobile manufacturer or a supplier that, for example, supplies the body panel or the body panel equipped with the concealed pre-mounted ultrasonic sensor.

[0048] According to a further embodiment, in step b) for each of the different temperatures, the probabilities that the respective peak is structure-borne sound are summed up based on the probability distribution pre-calibrated for the respective temperature for the specific peaks from each of the number of measurements, and the pre-calibrated probability distribution that best fits the peaks for which the largest sum of probabilities results is determined.

[0049] Accordingly, a simple procedure for determining the best-fitting probability distributions is advantageously provided. This is because the probability distribution that yields the highest cumulative probability that all measured peaks are structure-borne sound best describes the distribution of the peaks. 2023PF00672

[0050] 10

[0051] According to a further embodiment, in steps a) and b) only peaks are taken into account that occur within a period after the emission of the ultrasound pulse, within which structure-borne sound reflections are expected and no ground reflections are expected.

[0052] Accordingly, the ultrasound signal profile only needs to be recorded over the period in question.

[0053] The period during which ground reflections, i.e., reflections from a road surface, are expected depends on the geometry, i.e., the installation position and orientation of the body panel and the sensor mounted on it. Depending on the geometry, this period may overlap with the period during which structure-borne sound is expected. By disregarding the period during which ground reflections are expected (i.e., by not recording the ultrasonic signal profile during this period or by not considering peaks detected during this period), it is advantageous to prevent ground reflections, whose amplitude typically varies depending on the nature of the ground surface, from affecting the calibration result and / or the temperature measurement result.

[0054] According to one embodiment, steps a) to c) are each carried out with several ultrasonic sensors concealed on the same body panel, and the temperature of the body panel is determined as the average of the temperatures determined with each of the ultrasonic sensors in the respective step c).

[0055] This means that step c) is performed for each of the ultrasonic sensors, and the temperatures determined in this way are averaged. The averaged temperature represents the final result of the determination in step c). 2023PF00672

[0056] 11

[0057] In this way, the precision of the temperature determination can be advantageously increased further, as systematic errors that can occur with each individual ultrasonic sensor are averaged out.

[0058] According to a further embodiment, the method further comprises d) adjusting at least one parameter used to distinguish structure-borne sound echoes from ultrasonic echoes from the environment of the motor vehicle depending on the determined temperature of the body sheet metal.

[0059] Accordingly, temperature determination can advantageously be used to improve the differentiation between structure-borne sound and ultrasound from the environment.

[0060] The parameter can be an amplitude threshold or a parameter of a probability function used for differentiation. Selecting one of several reference signal waveforms pre-calibrated for different temperatures for subtraction from the ultrasound signal waveform can also be considered "adjusting at least one parameter".

[0061] According to a further embodiment, the method further comprises e) detecting and / or tracking an obstacle in the vicinity of the motor vehicle by means of a peak in an ultrasonic signal waveform received during a measurement carried out with the ultrasonic sensor, which is detected as an ultrasonic echo from the vicinity of the motor vehicle using at least one adapted parameter.

[0062] This means that the proposed method according to the present and further embodiments can also be described as a method for detecting and / or tracking an obstacle in the vicinity of a motor vehicle. Here, the accuracy of distinguishing between structure-borne sound and ultrasound from the vehicle's surroundings, and thus the precision of detection and / or tracking, can be advantageously improved by using the temperature-dependent parameter. 2023PF00672

[0063] 12

[0064] Detecting an obstacle can include, in particular, determining a distance to the obstacle and / or the position of the obstacle.

[0065] A distance to the obstacle can be detected, in particular, by determining the distance between the obstacle and the ultrasonic sensor based on the time of occurrence of a peak, which has been detected as an ultrasonic echo from the vicinity of the vehicle, in the ultrasonic signal profile, according to the following formula: s= 1 / z (c * t), where t = time difference between the appearance of the tip and the emission of the ultrasonic pulse, c = ultrasonic speed in air (possibly at an outside temperature determined by a temperature sensor), and s = distance to the obstacle. The factor 1The formula / z takes into account that the ultrasound signal travels to the obstacle and back again, thus covering twice the distance. In other words, it can be determined that a reflection point at the obstacle lies on a circle with radius s around an installation position of the ultrasound sensor.

[0066] In a more general case, where the ultrasonic pulse is received by a first ultrasonic sensor and the peak occurs in an ultrasonic signal waveform recorded by a second ultrasonic sensor, there is a reflection point on an ellipse whose foci form the installation positions of the two ultrasonic sensors, and which is defined as the set of all points for which the sum of the distance to the first and the distance to the second focal point corresponds to the signal propagation time, i.e., c * t.

[0067] The position of an obstacle can be determined, in particular, by measuring distances using several ultrasonic sensors mounted at different positions and then performing a lateration (trilateration, multilateration) based on the measured distances and the known installation positions of the sensors. Lateration can be intuitively described as determining the intersection points of circles and / or ellipses and / or fitting tangent lines to the circles and / or ellipses. 2023PF00672

[0068] 13

[0069] Tracking an obstacle can involve cyclically performing measurements with one or more ultrasonic sensors. If an obstacle is detected in the first measurement cycle, attempts are made to attribute spikes from subsequent measurements to the same obstacle using plausibility considerations (for example, by comparing the obstacle's position predicted based on past detections with its measured position in the following measurement cycle). Lower thresholds or probability distributions can be used for tracking to detect even weak spikes, while a higher threshold can be used for the initial detection of an obstacle.

[0070] According to another embodiment, the at least one parameter is a threshold value for the amplitude of the tip, above which the tip is treated as an ultrasonic echo from the environment of the motor vehicle.

[0071] According to a further embodiment, the at least one parameter is an index for selecting one of several reference signal profiles pre-calibrated for different temperatures, which are subtracted from the received ultrasonic signal profile during measurements with the ultrasonic sensor in order to filter out structure-borne sound.

[0072] According to a further embodiment, adjusting the at least one parameter in step d) includes selecting the one of the several pre-calibrated probability distributions that was determined in step b) to be the best fit for the peaks, and in step e) only those peaks are used for obstacle detection and / or tracking for which, based on the probability distribution selected in step d), there is a probability that the respective peak is structure-borne sound below a predetermined threshold. 2023PF00672

[0073] 14

[0074] This means that the pre-calibrated probability distributions can advantageously be used not only to determine the temperature of the vehicle body panels, but also to discriminate between structure-borne sound and ultrasound from the vehicle's surroundings. For the probability distribution determined to be best suited to the current temperature, all peaks resulting from structure-borne sound should have a high probability of being structure-borne sound. If a subsequent measurement with the ultrasound sensor reveals a peak in the received ultrasound signal waveform with a low probability, this peak is likely due to a reflection of the ultrasound signal from the vehicle's surroundings.

[0075] According to a further embodiment, the method comprises factory calibration of the probability distributions by: arranging the body panel or a prototype of the body panel with the ultrasonic sensor concealed thereon in a temperature chamber; setting one of the different temperatures in the temperature chamber; and for each of the set temperatures, performing a number of measurements with the ultrasonic sensor, each comprising emitting an ultrasonic pulse with the ultrasonic sensor and determining peaks in an ultrasonic signal waveform received by the ultrasonic sensor in response to the emission of the ultrasonic pulse, and calibrating the probability distribution for the respective temperature at least according to a distribution of the amplitudes of the peaks detected at the respective temperature.

[0076] Accordingly, a procedure for pre-calibrating the probability distributions is specified.

[0077] "At least according to an amplitude distribution" is to be understood in particular as "at least according to an amplitude distribution and optionally also according to a signal transit time distribution (or times of peak occurrence in the respective ultrasound signal waveform)." 2023PF00672

[0078] 15

[0079] Calibration can include, in particular, fitting the probability distribution to the frequency distribution of the specific peaks, which depends at least on the amplitude (and optionally on the signal propagation time), and / or adopting the frequency distribution as the probability distribution.

[0080] The method according to the present embodiment can be carried out fully automatically using a robot or as a human-machine interaction, in which at least the step of performing the measurements and the step of calibrating are carried out by a machine (a control unit or a computer).

[0081] Whether the set temperature has been reached can be determined, for example, using a laser thermometer. If the set temperature is not reached, the setting can be adjusted accordingly until the set temperature is reached.

[0082] According to one embodiment, the different temperatures (T) cover a temperature range from 0 °C to 60 °C, preferably from -20 °C to 80 °C, particularly preferably from -50 °C to 100 °C.

[0083] Accordingly, typical temperature ranges to which a car body panel may be exposed in different climate zones are covered.

[0084] Preferably, the number of different temperature T is at least 3, preferably 5, particularly preferably 10, even more preferably 20 and most particularly preferably 50, 100 or 150 support points within the temperature range.

[0085] According to a second aspect, a computer program product is proposed which includes commands that, when the program is executed by a control unit of a motor vehicle, which furthermore has a body panel and a concealed component on the body panel 2023PF00672

[0086] 16 mounted ultrasonic sensors, cause the control unit to execute the procedure described above.

[0087] A computer program product, such as a computer program tool, can be provided or delivered from a server on a network, for example, as a storage medium such as a memory card, USB stick, CD-ROM, DVD, ROM, PROM, EPROM, flash memory, or as a downloadable file. This can be done, for example, in a wireless communication network by transmitting the corresponding file containing the computer program product or tool.

[0088] According to a third aspect, a control unit is proposed which is configured to determine the temperature of a body panel of a motor vehicle by means of an ultrasonic sensor concealed on the body panel and comprises: a) a first unit configured to perform a number of measurements with the ultrasonic sensor, each comprising emitting an ultrasonic pulse with the ultrasonic sensor and determining peaks in an ultrasonic signal waveform received by the ultrasonic sensor in response to the emission of the ultrasonic pulse;b) a second unit configured to compare the identified peaks with several probability distributions pre-calibrated for different temperatures, which, depending on at least one amplitude of each peak, indicate a probability that the peak represents structure-borne sound reflected from the body panel, in order to determine which of the several probability distributions best matches the peaks identified by the first unit; and c) a third unit configured to determine a temperature of the body panel as the temperature associated with the probability distribution determined in step b) that best matches the identified peaks.

[0089] The respective unit can be implemented in hardware and / or software. In a hardware implementation, the respective unit can, for example, be a computer or a microprocessor. In a software implementation, 2023PF00672

[0090] 17

[0091] The implementation of each unit can be a computer program product, a function, a routine, an algorithm, a part of program code, or an executable object. Furthermore, each of the units mentioned above can also be part of a higher-level control system of the motor vehicle, such as a central electronic control unit and / or an engine control unit (ECU).

[0092] According to a fourth aspect, a motor vehicle is proposed, comprising a body panel, an ultrasonic sensor concealed on the body panel, and the control unit of the third aspect.

[0093] The embodiments, advantages and features described for the proposed method of the first aspect apply accordingly to the proposed computer program product of the second aspect, the proposed computer program product of the third aspect and the proposed motor vehicle of the fourth aspect.

[0094] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0095] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures.

[0096] Fig. 1 shows a side view of a motor vehicle according to exemplary embodiments;

[0097] Fig. 2 schematically shows a concealed ultrasonic sensor; 2023PF00672

[0098] 18

[0099] Fig. 3 shows steps of a calibration procedure according to a first embodiment;

[0100] Fig. 4 shows an external view of a prototype of the body panel with concealed ultrasonic sensor of the motor vehicle from Fig. 1;

[0101] Fig. 5 is a representation of a received ultrasound signal waveform;

[0102] Fig. 6 a)-c) shows a plot of the amplitudes of peaks determined in several measurements against the signal propagation time at different temperatures;

[0103] Fig. 7 shows several probability distributions pre-calibrated for different temperatures;

[0104] Fig. 8 shows steps of a method for determining a temperature according to a second embodiment;

[0105] Fig. 9 illustrates functional units of a control unit according to the second embodiment;

[0106] Fig. 10 shows an external view of a body panel with several concealed ultrasonic sensors according to a further development of the second embodiment;

[0107] Fig. 11 shows steps of a method for detecting and / or tracking an obstacle in the vicinity of a motor vehicle according to a third embodiment; and 2023PF00672

[0108] 19

[0109] Fig. 12 shows a received ultrasound signal waveform that includes structure-borne sound and ambient sound.

[0110] In the figures, identical or functionally equivalent elements have been given the same reference symbols, unless otherwise indicated.

[0111] Fig. 1 shows a side view of a motor vehicle 1 according to exemplary embodiments. The motor vehicle 1 has a driver's door 2 (example of a body panel) on which one or more ultrasonic sensors 3 are concealed. Furthermore, a control unit 4 is installed, for example, in an engine compartment, or alternatively at another suitable location, of the motor vehicle 1. This control unit is communicatively connected to the ultrasonic sensor 3, for example, via a wired connection using a bus or network, or wirelessly, and is configured to carry out the method described below according to the second or third exemplary embodiment or its further developments.

[0112] Fig. 2 illustrates the principle of concealed mounting of the ultrasonic sensor 3 in a view of the body panel 2 from the inside. A substantially circular damping material 8 is arranged on an inner surface of the body panel 2. The damping material 8 can be, for example, butyl and adheres to the body panel 2 by adhesion. A holder 5 is bonded to the damping material 8. This holder has a hollow cylindrical section 6 and a flanged section 7 projecting outwards from the hollow cylindrical section 6. The ultrasonic sensor 3 is inserted into the hollow cylindrical section 6 of the holder 5 with its ultrasonic diaphragm (not visible), to which an adhesive pad (not visible) is applied, facing downwards.During installation, the ultrasonic sensor 3 is pressed against the body panel 2, causing the ultrasonic membrane to come into firm, flat contact with the body panel 2 via the adhesive pad and be acoustically coupled to it. The damping material 8 is dimensioned such that structure-borne sound waves propagating in the body panel 2 when the ultrasonic membrane of the ultrasonic sensor 3 vibrates, and from the body panel 2023PF00672.

[0113] The sound waves 20 are reflected back to the ultrasonic sensor 3 from sheet metal 2, dampened, but not completely blocked. Reasons for this choice of dimensions for the damping material 8 include material savings; the need to excite structure-borne sound vibrations to achieve radiation of the ultrasonic waves into the environment; and also the desire to be able to receive structure-borne sound waves from the body sheet metal 2 in order to implement, for example, the proposed method or other structure-borne sound-based applications, such as touch detection or the like.

[0114] Fig. 3 shows steps of a calibration procedure according to a first embodiment; and Fig. 4 shows an external view of a prototype 21 of the body panel 2 from Fig. 1 with a concealed ultrasonic sensor 3 mounted according to the first embodiment. With reference to Fig. 3 and Fig. 4, a calibration procedure according to a first embodiment will now be described. The presented calibration procedure can be carried out fully automatically at the factory by a control unit (not shown), an industrial PC (not shown), or semi-automatically as a human-machine interaction.

[0115] In the calibration procedure, in step S1 1, the prototype 21 of the body panel 2 from Fig. 4, with the ultrasonic sensor 3 concealed on it, is placed in a temperature chamber (not shown). The temperature chamber allows a constant temperature to be set and maintained. The temperature chamber can be provided with a sound-absorbing inner lining, such as acoustic foam, so that the inner walls of the temperature chamber do not reflect incident ultrasound back to the ultrasonic sensor 3. Alternatively, the temperature chamber can be sufficiently large such that the walls of the temperature chamber are not within the field of view of the ultrasonic sensor 3 when the prototype 21 is positioned in the temperature chamber.

[0116] In step S12, a first temperature, for example T = 20 °C, is set. Preferably, one then waits until the set temperature T is reached in the temperature chamber, and particularly preferably, one waits until the prototype 21 of the body- 2023PF00672

[0117] The set temperature T has been reached in the body sheet 21. For this purpose, the temperature of prototype 21 of the body sheet 2 can be measured with a laser thermometer, for example.

[0118] In step S13, several measurements are then performed with the ultrasonic sensor 3 for the set temperature T. That is, the ultrasonic diaphragm of the ultrasonic sensor 3 is set into vibration to generate an ultrasonic pulse. The ultrasonic sensor 3 is then switched to a measurement mode, and an ultrasonic signal waveform 10 (Fig. 5) is recorded over a predetermined period, indicating the incident ultrasonic signal components (reflected back from the prototype 2 of the body panel 2). Peaks 9, 91-93 (Fig. 5) are then determined in the recorded, received ultrasonic signal waveform 10 (Fig. 5).

[0119] Fig. 5 is an exemplary representation of a received ultrasound signal waveform 10. Shown here is an envelope of the received raw signal. The envelope initially shows a transient phase over time, which lasts until time ti. Subsequently, several peaks 9, i.e., a first peak 91, a second peak 92, and a third peak 93, can be seen in the envelope of the ultrasound signal waveform 10. Finally, the signal drops to essentially zero by time te. Since the temperature chamber, as described above, is configured such that it reflects essentially no ultrasound back to the ultrasound sensor 3 when the prototype 2 is correctly positioned in the temperature chamber, it can be assumed that each of the peaks 91-93 is structure-borne sound reflected back from the prototype 21 of the body panel 2.Thus, the period from to te is a time after the emission of the ultrasonic pulse, within which structure-borne sound reflections are expected. In the following, only peaks 9 from this period are considered. It should be noted that if, due to the installation geometry, ground reflections were also to be expected in part of the period ti to te when the actual body panel 2 is installed in the motor vehicle 1 (Fig. 1), the time te can also be reduced such that only structure-borne sound reflections are expected in the period to to te, but no ground reflections. 2023PF00672.

[0120] 22

[0121] Reference is again made to Figures 2 to 5. In step S13, a multitude of measurements are successively carried out in the manner described, a respective ultrasound signal profile 10 is received, and one or more respective peaks 9 are determined therein.

[0122] Fig. 6 a) shows a plot of the amplitudes A of the peaks 9 determined in the several measurements against the signal propagation time t at a temperature T = 20°C. As can be seen in Fig. 6 a), the amplitudes A of the peaks 91-93 resulting from structure-borne sound are relatively low, independent of the signal propagation time t, when compared to the measurements at higher temperatures described later in Fig. 6 b) and Fig. 6 c). Although not apparent in Fig. 6 a), it has been experimentally shown that the amplitudes essentially follow a gamma distribution; that is, the frequency of a particular amplitude plotted against the amplitude follows the gamma distribution.

[0123] In step S14, a probability distribution, such as the gamma distribution, is fitted to the distribution of amplitudes of the peaks recorded at temperature T = 20 °C, as plotted in Fig. 6 a). For this purpose, the amplitude measurement points shown in Fig. 6 a) can be transferred to a histogram, which is generated for several amplitude bins (defined as sections of A). n <= A < (A n +AA = A n+i ), for n=1, 2, ....) indicate how often a peak 91-93 was determined whose amplitude A falls within the respective bin. A numerical representation of the probability distribution can be obtained by normalizing the histogram. This numerical representation can subsequently be used as a pre-calibrated probability distribution for the temperature T = 20 °C. Alternatively, a mathematical model, such as the gamma distribution, can be used: 2023PF00672

[0124] 23 with A=amplitude, r=Euler's gamma function, e=Euler's number, W(A) = probability density value for the amplitude A and the parameters b and p, can be fitted to the normalized histogram, that is, the parameters b and p can be analytically or numerically iteratively fitted so that the gamma distribution best describes the histogram, and the parameters b and p determined for the temperature T=20°C can subsequently be used as the pre-calibrated probability distribution (as its defining parameters).

[0125] Step S15 checks whether a calibration should be performed for another temperature. If so ("Y" at S15), the process branches back to step S12, and steps S12 to S15 are repeated for the next temperature. Otherwise ("N" at S15), the calibration procedure ends.

[0126] In the present example, calibration is performed for temperatures T = 20 °C, T = 40 °C, and T = 60 °C. Figures 6a) to 6c) show the plot of the amplitudes A of the structure-borne sound peaks 9 determined during the multiple measurements against the signal propagation time t at the respective temperature.

[0127] Fig. 7 shows the several probability distributions 1, 12, 13 pre-calibrated for the different temperatures T=20 °C, T=40 °C and T=60 °C, which in the example shown are modeled and parameterized gamma distributions. More precisely, probability distribution 11 comprises several gamma distributions for different signal propagation time bins at times ti, ta, ts, t4, ts. Here, the nth bin is defined as a segment of t n -0.5 At <= t < t n + 0.5 At, and the corresponding gamma distribution is at t nThe gamma distribution is shown in the diagram. To obtain or parameterize the respective gamma distribution, only peaks 9 were used in step S14 whose signal propagation times fell within the corresponding signal propagation time bin. Each of these gamma distributions exhibits a maximum at the amplitude that occurred most frequently in the corresponding signal propagation time bin in the associated plot from Fig. 6 a)-c). As can be seen in Fig. 7, 2023PF00672

[0128] 24 The different gamma distributions at each of the temperatures T for the different signal propagation time bins are essentially identical. However, this need not be the case; depending on the component geometry and properties, it is conceivable that the amplitude distributions are dependent on the signal propagation time. Thus, the probability p that a given peak 9 is structure-borne sound can be derived from the pre-calibrated probability distributions 1, 12, 13, depending on both the amplitude A of the peak 9 and the time t of the occurrence of the peak 9 in the received ultrasound signal waveform 10.

[0129] However, in some variants, it is also conceivable that a pre-calibrated probability distribution 1 1 comprises only a single gamma distribution, which is applied independently of the signal propagation time and specifies the probability p that a given peak 9 is structure-borne sound only as a function of the amplitude A of the peak 9. In this case, no signal propagation time bins need to be formed during calibration.

[0130] It should be noted that the temperatures of 20 °C, 40 °C, and 60 °C are shown for illustrative purposes only. Preferably, the temperatures iterated in the method shown in Fig. 3 cover a wide temperature range, for example, from 0 °C to 60 °C, more preferably from -20 °C to 80 °C, and more preferably from -50 °C to 100 °C. Furthermore, within this wide temperature range, the temperatures for which probability distributions 1 1 - 13 are pre-calibrated preferably cover more, and more preferably significantly more, than 3 data points (temperatures for which probability distributions 1 1 - 13 are calibrated) to enable more accurate temperature determination. The number of data points can be selected appropriately according to the desired accuracy.

[0131] The probability distributions 11, 12, 13, calibrated in this way, can be advantageously applied in the second or third embodiment of the procedure described below. 2023PF00672

[0132] 25

[0133] Fig. 8 shows steps of a method for determining a temperature according to a second embodiment, and Fig. 9 illustrates functional units of the control unit 4 (Fig. 1) according to the second embodiment. The functional units 41, 42, 43 can be configured, for example, by loading a computer program product into the control unit 4 and executing it, thereby causing the control unit 4 to configure the functional units 41, 42, 43 and to display the information shown in Fig.

[0134] To carry out the 8 shown procedures with steps S1, S2 and S3.

[0135] Reference is made to Fig. 1, Fig. 5, Fig. 8 and Fig. 9. In step S1, the first unit 41 of the control unit 4 performs one or preferably several measurements with the ultrasonic sensor 3, which is concealed on the front driver's door 2 of the motor vehicle 1. During each measurement, an ultrasonic pulse is emitted by the ultrasonic sensor 3 and an ultrasonic signal waveform 10 is received. Peaks 9, 91-93 are identified in the received ultrasonic signal waveform 10.

[0136] In step S2, the second unit 42 of the control unit 4 compares the peaks 9, 91-93 determined in step S1 with the several probability distributions 11-13 (Fig. 7) previously calibrated for different temperatures T. These distributions were obtained, for example, using the method of the first embodiment and are stored in a memory such as a ROM, PROM, EPROM, or flash memory (not shown) of the control unit 4. The second unit 42 then determines which of the previously calibrated probability distributions 11-13 (Fig. 7) best matches the peaks 9, 91-93 determined in step S1.

[0137] Different methods of comparison are conceivable. In one variant, the second unit 42 can, in the same way as described for pre-calibration in step S14 (Fig. 3) of the first embodiment, generate a histogram—or several histograms for different signal propagation delay bins—using the amplitude values ​​of the peaks 9, 91–93 determined in step S1, normalize the histograms, and then fit a gamma distribution or another mathematical model to the histograms. The parameters of a 2023PF00672

[0138] The frequency distribution obtained in this way can then be compared with the parameters of the pre-calibrated probability distributions 11-13 (Fig. 7). The best-fitting probability distribution 11-13 (Fig. 7) can then be determined to be that of the probability distributions 11-13 (Fig. 7) whose parameters deviate least from the parameters of the determined frequency distribution.

[0139] In another, particularly preferred variant, the comparison can be carried out by performing the following steps for each of the temperatures T for which a pre-calibrated probability distribution 1 1 -13 (Fig. 7) is available: For each peak 9, 91 -93 determined in step S1, the probability p that the respective peak 9 is structure-borne sound is taken from the amplitude A of the peak 9, 91 -93 of the probability distribution 1 1 -13 (Fig. 7) for the respective temperature. If the probability distribution for the respective temperature includes more than one gamma distribution (or Poisson distribution, or histogram) for different signal propagation time bins at the same temperature T, the one of the gamma distributions (Poisson distributions, histograms) is used in whose signal propagation time bin the signal propagation time t of the determined peak 9 falls.The probabilities obtained in this way for all of the peaks determined in step S1 are summed up, and a summed probability will be included that the peaks determined in step S2 are structure-borne sound.

[0140] The steps just described are repeated for each of the probability distributions 11-13 (Fig. 7) pre-calibrated for different temperatures T. Then, the pre-calibrated probability distribution 11-13 (Fig. 7) with the largest sum of probabilities p (the highest summed probability) is selected. In this way, a probability distribution 11-13 (Fig. 7) is selected that indicates structure-borne sound for the greatest number of the determined peaks 9. It is assumed that the measurement in step S1 is performed while there is no obstacle in the field of view of the ultrasonic sensor 3 in the vicinity of the vehicle 1. In this case, all of the peaks in 2023PF00672 are...

[0141] 27

[0142] Step S2 determined peaks around structure-borne sound, and the one of the probability distributions 1 1 -13 (Fig. 7) for which the highest summed probability for structure-borne sound results best describes the actual situation.

[0143] It should be noted that in step S1, a larger number of measurements are preferably carried out over a certain period of time. This takes advantage of the fact that the temperature of the body panel 2 changes only relatively slowly. If many measurements are carried out over a certain period, then even an obstacle in the vicinity of the vehicle 1, which is in the field of view for only some of the many measurements and produces a spike that is not attributable to structure-borne noise, will not significantly affect the result of the comparison in step S2.

[0144] Then, in step S3, the temperature T that corresponds to the most suitable probability distribution 1 1 -13 is determined to be the temperature T of the body panel 2.

[0145] Thus, according to the second embodiment, a method is specified which is advantageously able to determine the temperature T of the body panel 2 without requiring a separate temperature sensor.

[0146] It is understood that, according to an advantageous further development of the second embodiment, in step S1 only peaks 9 are used in the period to-te (Fig. 5), within which structure-borne sound reflections are expected and no ground reflections are expected.

[0147] It is understood that the precision of the temperature determination can be further improved if, as shown in Fig. 10, several ultrasonic sensors 31-33 are concealed on a body panel 2' according to a preferred embodiment, and the method of the second embodiment is carried out with each of the several ultrasonic sensors. 2023PF00672

[0148] The process is carried out using 28 ultrasonic sensors 31, 32, 33, and the final temperature T of the body panel 2' is determined as the average of the preliminary temperatures T determined with each of the ultrasonic sensors 31, 32, 33. Such averaging is particularly advantageous when a large number of pre-calibrated probability distributions 11, 12, 13 (Fig. 7) are available, which cover the temperature range of interest with very fine granularity, for example, in temperature steps of 2 °C, preferably 1 °C, and especially preferably 0.5 °C. In this case, it is to be expected that a different temperature value T will result with each execution of steps S1-S3 with one of the ultrasonic sensors 31-33, and averaging in this case leads closer to the actual temperature value T.It should be noted that in this case, during pre-calibration using a prototype 22 of the body sheet 2', respective probability distributions 11-13 (Fig. 7) for different temperatures T can be calibrated separately for each of the several ultrasonic sensors 31 , 32, 33, which may differ from each other for different ultrasonic sensors 31 , 32, 33.

[0149] Fig. 11 shows steps of a method for detecting and / or tracking an obstacle in the vicinity of a motor vehicle 1 according to a third embodiment; and Fig. 12 shows a received ultrasonic signal waveform 10', which includes structure-borne sound and ambient sound. The third embodiment is described with reference to Figs. 1, 4, 11 and 12.

[0150] The third embodiment is based on the second embodiment and / or one of its preferred further developments, and steps S1 to S3 are identical to those of the second embodiment and / or one of its preferred further developments. That is to say, in steps S1 to S3, a temperature T of the body panel 2 is first determined in the manner described above.

[0151] In step S4, the following then occurs depending on the determined temperature T of the body panel.

[0152] 2 at least one parameter adjusted to distinguish between structure-borne sound reflections 2023PF00672

[0153] 29 uses ultrasonic reflections from the environment of the motor vehicle 1. This is explained in more detail below with the help of examples.

[0154] In step S5, a further measurement is carried out with the ultrasonic sensor 3 in the manner described above, and an obstacle in the vicinity of the motor vehicle 1 is detected and / or tracked by means of a peak 9 in an ultrasonic signal waveform 10' received during the further measurement carried out with the ultrasonic sensor 3, wherein the peak 9 is a peak 94 which is identified as an ultrasonic echo from the vicinity of the motor vehicle 1 using the at least one adapted parameter.

[0155] Here, using the peak 94, which is identified as ambient sound, a distance from the ultrasonic sensor 3 to the presumed obstacle in the vicinity of the vehicle 1 is determined, for example. For this purpose, the distance d can be determined from the signal travel time t2 at which the peak 94 occurs, according to the formula d=c*t2, where c denotes the speed of sound in air.

[0156] Preferably, the method is repeated with several ultrasonic sensors 31-33 (Fig. 10) mounted at different positions on the body panel 2', and / or with several ultrasonic sensors (not shown) mounted on different body panels (2, 2' and others). In this case, by laterally adjusting the several determined distances using the known installation positions of the ultrasonic sensors 3, 31-33 used for measurement, a position of the suspected obstacle in the vicinity of the motor vehicle 1 can also be determined.

[0157] Obstacle detection and / or tracking in step S5, taking into account the determined temperature, is repeated regularly. Similarly, but at longer intervals, steps S1 to S5—that is, temperature determination followed by obstacle detection and / or tracking—are also repeated regularly. 2023PF00672

[0158] 30

[0159] That is, according to the third embodiment, the precision of the distinction between structure-borne sound and ambient sound, and thus the precision of the detection and / or tracking of obstacles in the vicinity of the motor vehicle 1, can be advantageously improved using the temperature T determined according to the method of the second embodiment.

[0160] Fig. 12 shows an ultrasonic signal waveform 10' received during the subsequent measurement from step S5. Reference is also made to Figs. 1, 4, 11, and 12. The ultrasonic signal waveform 10' comprises peaks 91, 92, and 93, which originate from structure-borne sound reflected from the body panel 2, and a peak 94, which originates from ambient sound reflected from the surroundings of the vehicle 1 back to the ultrasonic sensor 3. As can be seen in Fig. 12, in the present example (at the temperature underlying this example), the ambient sound has a higher amplitude A of the corresponding peak 94 than the structure-borne sound (peaks 91, 92, and 93).

[0161] According to a variant of the third embodiment, in step S4, at least one parameter is selected as a threshold value for the amplitude A of peaks 9, 91-94, depending on the temperature T determined in step S3. If this threshold is exceeded, a peak 94 exceeding the threshold is treated as an ultrasonic echo from the surroundings of the vehicle 1. The threshold value can be determined, for example, based on the probability distribution 11-13 (Fig. 7) pre-calibrated for the respective temperature T, to an amplitude value at which the probability p, according to the distribution (gamma distribution or the like), has fallen below a predefined threshold value after reaching a maximum with increasing amplitude. If the probability distribution 11-13 (Fig. 7) consists of different gamma distributions (normalized histograms, Poisson distributions, or the like),Since the parameter for different signal propagation delay bins includes at least one parameter that is adjusted, it can accordingly include several distance-dependent amplitude thresholds. 2023PF00672.

[0162] 31

[0163] According to another variant of the third embodiment, in step S4, at least one parameter, b, p, is fitted to a probability distribution used to distinguish structure-borne sound from ambient sound, depending on the temperature determined in step S3. In other words, the probability distribution 11-13 (Fig. 7) corresponding to the determined temperature is selected as suitable, and for each of the peaks 91-94 identified in the ultrasound signal waveform 10' received in step S5, a probability p is determined, based on the selected probability distribution 11-13 (Fig. 7), that the respective peak 91-94 is structure-borne sound. Based on the determined probability p, it is decided whether the peak, as with peaks 91-93, is structure-borne sound or, as with peak 94, ambient sound.For example, peak 94 can be identified as ambient sound because the probability p assigned to it is below a predetermined threshold.

[0164] According to the present variant, an even finer distinction between structure-borne sound and ambient sound is possible. Particularly at higher temperatures, for example, a peak with an amplitude A that is lower than the expected amplitude A of structure-borne sound can be interpreted as ambient sound.

[0165] The two variants can also be combined: For the initial detection of peaks 94, which are ambient sound, the amplitude threshold according to the first variant can be used, while for tracking, i.e. for re-detecting a corresponding peak 94 in a subsequent measurement, the selected probability distribution 11-13 (Fig. 7) can be used.

[0166] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. 2023PF00672

[0167] 32

[0168] As an example, the body panel 2 is a front driver's door of the motor vehicle 1; however, any body component can be provided as a sheet metal part with a concealed ultrasonic sensor 3, such as a fender, a side sill, a passenger door, a rear passenger door, a tailgate, or the like. The methods for calibrating, determining a temperature, and determining an obstacle according to the described embodiments can be applied to any of these body panels.

[0169] The respective pre-calibrated probability distributions 1, 12, 13 were described as one or more gamma distributions. However, other distributions can be parameterized, for example, a Poisson distribution. It is also conceivable not to parameterize any mathematical model at all, but simply to use the normalized histograms generated from a plot as in Fig. 6 as the numerical probability distribution.

[0170] For the first embodiment, a preliminary calibration was described using a prototype 21 of the body panel 2. However, it is also conceivable to carry out the preliminary calibration for each specific body panel 2 or even to perform it on a sample basis for every 10th, 100th, 1000th, or 10000th of a series of produced body panels 2 of the same vehicle model.

[0171] The presented method for pre-calibrating the first embodiment is purely exemplary. The presented methods according to the second and third embodiments need not include the steps of the first embodiment. The pre-calibrated probability distributions 1 1 -31 (Fig. 7) for carrying out the method of the second and third embodiments can be obtained in any way, for example, by computer simulations, or can be provided by a manufacturer of the body panel 2, the ultrasonic sensor 3, or the like. 2023PF00672

[0172] 33

[0173] REFERENCE MARK LIST

[0174] 1 motor vehicle

[0175] 2.2' Body panel, front driver's door

[0176] 3 Ultrasonic sensor

[0177] 4 Control unit

[0178] 5 bracket

[0179] 6 hollow cylindrical section

[0180] 7 Flange section

[0181] 8 Damping material

[0182] 9 top spots

[0183] 10, 10' Ultrasound signal waveform

[0184] 11-13 Probability distribution

[0185] 21, 22 Prototype of the body sheet metal

[0186] 31-33 Ultrasonic sensors

[0187] 41-43 functional units

[0188] 91 first peak

[0189] 92 second top

[0190] 93 third top

[0191] 94 peaks, which are due to ambient sound

[0192] A Amplitude

[0193] S1-S3 Steps for Determining a Temperature

[0194] S4-S5 Steps for identifying or tracking an obstacle

[0195] S11-S15 Steps for Calibrating t Signal propagation time to-te Signal propagation times

Claims

2023PF00672 34 PATENT CLAIMS 1. Method for determining a temperature (T) of a body panel (2) of a motor vehicle (1) by means of an ultrasonic sensor (3) concealed on the body panel (2), comprising: a) performing (S1) a number of measurements with the ultrasonic sensor (3), each comprising emitting an ultrasonic pulse with the ultrasonic sensor (3) and determining a number of peaks (9) in an ultrasonic signal waveform (10) received by the ultrasonic sensor (3) in response to the emission of the ultrasonic pulse;b) Comparing (S2) the peaks determined in step a) with several probability distributions (11, 12, 13) previously calibrated for different temperatures (T), which, depending on at least one amplitude (A) of a respective peak (9), indicate a probability (p) that the peak (9) is structure-borne sound reflected back from the body panel (2), in order to determine one of the several probability distributions (11, 12, 13) that best matches the peaks (9) determined in step a); and c) Determining (S3) a temperature (T) of the body panel (2) as the temperature (T) that is assigned to the probability distribution (11, 12, 13) determined in step b) that best matches the determined peaks (9).

2. Method according to claim 1, wherein the pre-calibrated probability distributions (11 , 12, 13) further specify the probability (p) that the tip is structure-borne sound, depending on a time (t) of the occurrence of the tip (9) in the received ultrasound signal profile (10).

3. Method according to one of the preceding claims, wherein the pre-calibrated probability distributions (11 , 12, 13) are calibrated at the factory on the body panel (2) or on a prototype (21 ) of the body panel (2). 2023PF00672 35 4. Method according to one of the preceding claims, wherein in step b) for each of the different temperatures (T) the probabilities (p) that the respective peak (9) is structure-borne sound are summed up for each of the number of measurements based on the probability distribution (11 , 12, 13) pre-calibrated for the respective temperature (T) and the pre-calibrated probability distribution (11 , 12, 13) that best fits the peaks (9) is determined for which the largest sum of the probabilities (p) is obtained.

5. Method according to one of the preceding claims, wherein in steps a) and b) only peaks (9) are taken into consideration which occur within a period after emission of the ultrasound pulse within which structure-borne sound reflections are expected and no ground reflections are expected.

6. Method according to one of the preceding claims, wherein steps a) to c) are each carried out with several ultrasonic sensors (31 , 32, 33) concealed on the same body panel (2), and the temperature (T) of the body panel (2) is determined as the mean of the temperatures (T) determined with each of the ultrasonic sensors (31 , 32, 33) in the respective step c).

7. Method according to any of the preceding claims, further comprising: d) adjusting (S4) at least one parameter used to distinguish structure-borne sound echoes from ultrasonic echoes from an environment of the motor vehicle (1) depending on the determined temperature (T) of the body panel (2).

8. Method according to claim 7, further comprising: e) detecting and / or tracking (S5) an obstacle in the vicinity of the motor vehicle (1) by means of a tip (94) in a position equipped with the ultrasonic sensor (3) 2023PF00672 36 performed measurement received ultrasound signal profile (10), which is recognized as an ultrasound echo from the environment of the motor vehicle (1) using at least one adapted parameter.

9. Method according to claim 7 or 8, wherein the at least one parameter is a threshold value for the amplitude (A) of the tip (9, 91-94), above which the tip (94) is treated as an ultrasonic echo from the environment of the motor vehicle (1).

10. Method according to claim 8, wherein the adjustment of the at least one parameter in step d) comprises selecting the one of the several pre-calibrated probability distributions (11, 12, 13) that was determined in step b) to be the best fit for the peaks (9), and in step e) for detecting and / or tracking an obstacle only peaks (94) are used for which, based on the probability distribution (11, 12, 13) selected in step d), there is a probability (p) that the respective peak (94) is structure-borne sound that is below a predetermined threshold.

11. Method according to any of the preceding claims, further comprising factory calibration of the probability distributions by: Arranging (S11) the body panel (2) or a prototype (21) of the body panel (2) with the ultrasonic sensor (3) concealed on it in a temperature chamber, Setting (S12) one of the different temperatures (T) in the temperature chamber; for each of the set temperatures (T), performing (S13) a number of measurements with the ultrasonic sensor (3), each comprising emitting an ultrasonic pulse with the ultrasonic sensor (3) and determining peaks (9) in one of the 2023PF00672 37 Ultrasound sensor (3) received in response to the emission of the ultrasound pulse Ultrasound signal waveform (10), and Calibrating (S14) the probability distribution (11 , 12, 13) for the respective temperature (T) at least according to a distribution of the amplitudes (A) of the peaks (9) recorded at the respective temperature (T).

12. Method according to one of the preceding claims, wherein the different temperatures (T) cover a temperature range from 0 °C to 60 °C, preferably from -20 °C to 80 °C, particularly preferably from -50 °C to 100 °C.

13. Computer program product comprising commands which, when the program is executed by a control unit (4) of a motor vehicle (1), which further comprises a body panel (2) and an ultrasonic sensor (3) concealed on the body panel (2), cause the control unit (4) to carry out the method according to any one of claims 1 to 10.

14. Control unit (4), configured for determining a temperature (T) of a body panel (2) of a motor vehicle (1) by means of an ultrasonic sensor (3) concealed on the body panel (2), comprising: a) a first unit (41) configured to perform a number of measurements with the ultrasonic sensor (3), each comprising emitting an ultrasonic pulse with the ultrasonic sensor (3) and determining peaks (9) in an ultrasonic signal waveform (10) received by the ultrasonic sensor (3) in response to the emission of the ultrasonic pulse; b) a second unit (42) configured to compare the determined peaks (9) with several probability distributions (11, 12, 13) pre-calibrated for different temperatures (T), which, depending on at least one amplitude (A) of a respective peak (9), specify a probability (p) that the peak is 2023PF00672 38. Structure-borne sound reflected from the body sheet (2) to determine one of the several probability distributions (11, 12, 13) that best matches the peaks (9) determined by the first unit; and c) a third unit (43) configured to determine a temperature (T) of the body sheet (2) as that assigned to the probability distribution (11, 12, 13) determined in step b) that best matches the determined peaks (9).

15. Motor vehicle (1) comprising a body panel (2), an ultrasonic sensor (3) concealed on the body panel (2), and the control unit (4) according to claim 14.

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