Method for a height measurement in a vehicle, controller, and vehicle

Abstract

The invention relates to a method for measuring a height in a vehicle (10) with a height adjustment function. A sensor (19) for measuring a height is arranged on the chassis (11) of the vehicle (10) or is connected to the chassis (11) at a defined distance thereto. The sensor (19) is arranged such that distances (A, aA) to an axle (14) of the vehicle (10) and in particular to the ground (23) below the vehicle (10) can be detected. The sensor (19) transmit signals in the direction of the axle (14) and in particular the ground (23) and receives reflected signals and the intensities (I) thereof. The sensor (19) additionally at least indirectly detects the time spans between transmitted signals and reflected signals as signal peaks (P1 to P6). The time spans represent the distances (A, aA) of the sensor (19) to the axle (14) and in particular to the ground (23) or can be calculated into the distances (A, aA).

Description

[0001] Method for measuring height in a vehicle, control unit and vehicle

[0002] The invention relates to a method for measuring height in a vehicle with height adjustment, wherein a sensor for measuring height is arranged on a chassis of the vehicle or is connected to the chassis at a defined distance, the sensor is arranged such that distances to an axle of the vehicle and in particular also to the ground beneath the vehicle can be detected and the sensor sends signals in the direction of the axle, receives reflected signals and at least indirectly records their intensities as well as propagation times between sent signals and reflected signals as signal peaks, wherein the propagation times represent the distances of the sensor to the axle and in particular also to the ground or can be converted into the distances.

[0003] The vehicle in question is, in particular, a vehicle with air suspension, especially a commercial vehicle. Other types of suspension and vehicle are also possible, as long as height adjustment is provided.

[0004] Furthermore, the vehicle is particularly equipped with a central control unit for the air suspension or height adjustment. The control unit may also be part of a braking system.

[0005] Furthermore, the vehicle is specifically a trailer vehicle. However, it can also be a towing vehicle.

[0006] Furthermore, the vehicle is particularly equipped with two or more axles. It can also be a single-axle trailer.

[0007] The sensor contains a transmitter and receiver in a single device, or is a combination of transmitter and receiver that are coordinated or interconnected by circuitry. Commercial vehicles and passenger cars can be equipped with a height adjustment system. The height of the chassis above the axles can then be adjusted. In particular, the vehicles are equipped with air suspension, which allows for height adjustment.

[0008] To perform a targeted height adjustment, the current height must be detected. In this context, the use of a sensor is known. This sensor is designed as a transmitter and receiver, transmits signals toward the axis, receives reflected signals, and records their intensities and propagation times as signal peaks. With a known signal speed, the propagation time is also a measure of the distance between the sensor and the axis. When propagation time is mentioned below and in connection with the invention, this also refers in particular to the distance.

[0009] The use of a radar sensor for detecting altitude is known from EP 4 020 012 A1. Also in the context of the present invention, the sensor used is, in particular, a radar sensor.

[0010] Radar sensors for measuring distance and movement around a vehicle have been known for some time, see, for example, BOSCH Automotive Handbook, 27th edition (2011), from page 1154, section "Sensors for Driver Assistance Systems", and subsequent editions.

[0011] Radar sensors for measuring distance and movement in vehicles are also well known, for example the AWRL6432 radar sensor from Texas Instruments Incorporated, USA and the A111 radar sensor from Acconeer AB, Sweden.

[0012] The sensor should reliably detect the position of the axle relative to the chassis, thus enabling the determination of the current distance between the axle and the chassis. In particular, the sensor should also detect the surface on which the vehicle is moving, i.e., the ground.

[0013] Radar sensors and other types of sensors have a spatial beam angle for the emitted signals, such as a cone shape or similar. The sensor is positioned on the chassis in such a way that the axle and / or the ground can be reliably detected. Furthermore, there may be components on the axle and extending from the chassis that are within the beam cone of the sensor's signals and are also detected. The signals reflected by these components are recorded by the sensor, just like the signals from the axle and / or the ground.

[0014] When installing the sensor, it must be calibrated to ensure it can reliably distinguish the axle and / or ground from other components. Calibration should be as automatic as possible.

[0015] The method according to the invention has the features of claim 1. Accordingly, the method for height measurement is used in a vehicle with height adjustment, wherein a sensor for height measurement is arranged on a chassis of the vehicle or is connected to the chassis at a defined distance, the sensor is arranged such that distances to an axle of the vehicle and in particular also to the ground beneath the vehicle can be detected and the sensor sends signals in the direction of the axle, receives reflected signals and at least indirectly records their intensities as well as propagation times between sent signals and reflected signals as signal peaks, wherein the propagation times represent the distances of the sensor to the axle and in particular also to the ground or can be converted into the distances.In particular, the following steps are carried out for calibration: a) different heights of the vehicle are controlled by the height adjustment, b) for each height controlled in step a), the travel times and signal intensities of the reflected signals are determined so that a raw signal data set consisting of the travel times and signal intensities of the signal peaks is created for each controlled height, c) from the travel times and signal intensities determined in step b), the signal peaks are identified which always have the same travel times regardless of the controlled height, d) the signal peaks identified in step c) with always the same travel times together form a background data set which is saved for further use. The method first determines a raw signal data set from the signal peaks with travel times and signal intensities for each controlled height.The height can be varied in different ways, for example, incrementally, so that the height is adjusted by one millimeter, one centimeter, or another amount, in particular by approximately 0.5 mm, starting from a minimum or maximum. A raw signal data set is created for each set height.

[0016] Continuous height adjustment is also possible, for example, at one centimeter per second (1 cm / s). The sensor can transmit its signals at defined intervals and record signal peaks, thus generating raw signal data sets for different heights.

[0017] Using the raw signal data sets, the signal peaks are identified; these are always the same, despite different height settings. Identification can be achieved using mathematical methods. Methods for detecting patterns in data sets are well known from a wide variety of applications and need not be explained in detail here. The identified signal peaks relate to components whose height relative to the chassis is unchanged and which therefore interfere with the height measurement. These include, for example, rods connected to the chassis or other attachments that are firmly attached to the chassis and lie within the sensor's radiation cone. These signal peaks together form the aforementioned background data set, which is saved and can optionally be used in the process.

[0018] According to an optional concept of the invention, the signal peaks of the background data set are subtracted from the signal peaks of all raw signal data sets, so that a corrected signal data set is created for each raw signal data set, which is then saved. The saved corrected signal data sets can optionally be used in the further process. In addition, the peak data sets can also contain further selected signal peaks. Depending on the selection of the signal peaks, a considerable reduction in the size of the individually saved signal data sets is possible, which can simplify subsequent processing. According to an optional concept of the invention, signal peaks are identified in each corrected signal data set which relate to the axis and in particular also to the ground, namely axis signal peaks and in particular also ground signal peaks.The corrected signal data sets only contain the signal peaks of the components whose height is variable relative to the chassis, namely the axle signal peak, in particular the ground signal peak, and possibly other signal peaks. Typically, the axle signal peak is the strongest signal peak with a short propagation time, while the ground signal peak is a relatively strong signal peak with a longer propagation time. Due to the short distance to the sensor and the size of the axle, the axle signal peak will often have the highest intensity of all signal peaks. In a workshop environment, the propagation time of the ground signal peak will be the longest. Axle signal peaks and ground signal peaks can therefore be determined relatively reliably by their signal intensities and propagation times. Corrected signal data sets in which at least the axle signal peak and in particular the ground signal peak are identified are referred to here as peak data sets.

[0019] According to an optional aspect of the invention, at least the axis signal peaks and, in particular, also the ground signal peaks of the corrected signal data sets are stored as peak data sets. In this case, the peak data sets are reduced, corrected signal data sets in which at least the axis signal peaks and, in particular, also the ground signal peaks are identified. In addition, any additional signal peaks present can also be stored in the peak data sets. In extreme cases, the signal peaks of the peak data sets match the signal peaks of the corrected signal data sets.

[0020] Optionally and according to the invention, the method may include the following steps: e) for at least one height of the vehicle, several or all

[0021] Signal intensities are compared to determine a highest signal intensity, f) if the highest signal intensity can be determined, this is defined as part of the axis signal peak, g) if the highest signal intensity cannot be determined, the axis is provided with a reflector to improve the reflection of the transmitted signals, h) after applying the reflector, steps a) to c) are repeated.

[0022] The goal is to determine the axis signal peak. If a signal peak stands out clearly from the other signal peaks, it is likely to be the axis signal peak. A clear difference is not present, for example, if the two highest signal peaks have the same or only slightly different signal intensities. What is considered slight in this sense can be defined by parameters. If no axis signal peak can be determined in this way, the process is interrupted and the axis is provided with the reflector to improve reflection, so that the signal intensity of the axis signal peak is increased. After the reflector has been applied, the described steps e) to g) are repeated. If an axis signal peak can now be identified, the process is continued according to claim 1. The fact that a highest signal intensity cannot be determined can be indicated, for example, by a signal that is recognizable to operators.

[0023] According to an optional aspect of the invention, the highest signal intensity can be selected that which is at least a defined amount higher than any other compared signal intensity. The defined amount is, in particular, an absolute amount or a defined fraction of the comparatively lower or higher signal intensity, for example, 5% or 10%. The intensity itself is defined, in particular, as the ratio of the received reflected signal to the transmitted signal and can be specified as a percentage.

[0024] According to an optional concept of the invention, the signal intensity can be selected as the ground signal peak which has a propagation time that is a defined amount longer than the axle signal peak and, in particular, is also a defined amount higher than neighboring signal intensities. Due to the known diameter of the wheels on the axles, the difference in propagation times between the ground signal peak and the axle signal peak is known within relatively narrow limits. A minimum and a maximum can be specified as the defined amount of the longer propagation time. Furthermore, it can be expected that the ground, due to its surface area, will provide a reflected signal with a relatively high signal intensity. If components arranged on the axle and running below it also provide reflected signals, their signal intensities are likely to be lower. The named constraints allow the ground signal peak to be reliably determined.

[0025] According to an optional concept of the invention, vertical distances to the axle can be calculated and stored from the axle signal peaks by linearization. For calibration purposes, the runtimes representing the different distances can be calculated, provided only the axle signal peak is of interest. However, if the axle signal peak and the ground signal peak are compared, linearizing the axle signal peak can be useful. The reason for this is the chassis geometry with the axle suspension. For example, the axle is held by trailing arms and supported by air springs. When the height is adjusted, the axle moves along a partial circular path, i.e., with a vertical and a horizontal component, both of which are variable.

[0026] In addition, the sensor is often not mounted vertically above the axle. Therefore, the travel time of the axle signal peak cannot be directly converted into the vertical distance between a horizontal plane of the axle and a horizontal plane of the sensor. Rather, the position of the sensor and the pitch circle motion of the axle must be taken into account. This is referred to as linearization. The result of linearization is the vertical axle distances, i.e., the aforementioned vertical distances between the plane of the axle and the plane of the sensor. Linearization is easily accomplished with knowledge of the chassis geometry and the arrangement of the sensor relative to the axle and need not be explained in detail here.

[0027] The peak data sets already mentioned can contain the vertical distances to the axle determined by linearization for the axle signal peaks in addition to or instead of the runtimes / distances. Alternatively, linearized peak data sets are created from the existing peak data sets through linearization and saved. The linearized peak data sets can replace the existing peak data sets or be saved in addition to them. Whether linearization is useful can be assessed based on the deviations between the peak data sets and the linearized peak data sets that occur in practice for a specific vehicle. According to an optional concept of the invention, two or more different heights are controlled for calibration, in particular continuously or cyclically. The background data set can be determined from just two different heights. In particular, more different heights are controlled.

[0028] According to an optional aspect of the invention, at least a minimum and a maximum height of the vehicle are controlled for calibration. At least for the minimum and maximum height of the vehicle, the theoretical distances between the ground and the sensor, as well as between the axle and the sensor, can be determined from the chassis geometry, thus enabling an additional check of the plausibility of the obtained data.

[0029] According to an optional aspect of the invention, all heights can be controlled for calibration from a minimum vehicle height to the maximum vehicle height, or vice versa. For example, the air springs are first deflated and then inflated gradually or continuously until the maximum height is reached. The range from minimum to maximum height then defines the measurement range within which the calibration is performed.

[0030] According to an optional aspect of the invention, a radar sensor can be used as the sensor. The radar sensor is less susceptible to contamination than an optical transmitter-receiver. In particular, the radar sensor operates using the FMCW (Frequency Modulation Continuous Wave) or PCR (Pulse Coherent Radar) method. The radar sensor can operate in a frequency range of 50 GHz to 100 GHz, in particular at approximately 60 GHz or approximately 77 GHz. The radiation angle can be, in particular, 10° to 30°. Alternatively, other sensor technologies can be used, such as ultrasonic sensors or lidar sensors, particularly sensors with a sharp radiation angle.

[0031] According to an optional concept of the invention, the following steps can be provided when peak data sets and background data sets are present after starting the vehicle: at least one current raw signal data set is created, an associated current peak data set is calculated by subtracting the existing background data set from the current raw signal data set, the current axle signal peak is identified within the current peak data set by comparing the current peak data set with the existing peak data sets or by selecting a highest current signal peak.

[0032] Starting the vehicle is defined as switching on the ignition or pressing a start button. Peak data sets and background data sets must already be available. The peak data sets can also be the linearized peak data sets. After the vehicle is started, the sensor is automatically activated and generates a new raw signal data set, which is referred to as the current raw signal data set and is renewed cyclically. The goal is to determine the current axle signal peak and thus the current vehicle height. For this purpose, the existing background data set is subtracted from the current raw signal data set, and a current corrected signal data set and a current peak data set are calculated. The current axle signal peak is determined by comparing the current peak data set with the existing peak data sets or by selecting the highest current signal peak.The current vehicle height can be determined from the transit time of the current axle signal peak. During vehicle operation, the steps are repeated automatically, cyclically, or on demand. The steps are executed, in particular, program-controlled.

[0033] According to an optional feature of the invention, a current vertical distance to the axle can be calculated from the propagation time of the current axle signal peak by linearization. Depending on the chassis geometry and sensor arrangement, the vertical distance and thus also the current vehicle height may differ from the distance between the sensor and the axle.

[0034] According to an optional concept of the invention, the identified current axis signal peak can be checked for plausibility by the following measures: Checking whether the current peak data set has a ground signal peak which matches the identified current axis signal peak in terms of its runtime and / or its signal intensity, or

[0035] Check whether the current peak data set contains other signal peaks whose runtimes and / or signal intensities match the identified current axis signal peak.

[0036] The ground signal peak must be at a certain distance from the axis signal peak, although this distance can only fluctuate slightly. Furthermore, the current ground signal peak must match the same existing peak data set as the current axis signal peak. The same applies to other current signal peaks in the current peak data set. If the check fails to establish plausibility, an error message may be issued.

[0037] According to an optional concept of the invention, depending on the outcome of the plausibility check, another current signal peak can be selected as the current axle signal peak or the previously specified steps can be repeated, in particular for a different height of the vehicle.

[0038] The invention also relates to a sensor for measuring altitude in a vehicle, according to claim 18, with software for implementing the method according to the invention. Sensors as integrated components can be equipped with a processor, memory, and a user-programmable area for processing the acquired data; see also the radar sensors for measuring distance and movement in vehicles mentioned above.

[0039] According to claim 19, the invention also relates to a control unit with software for implementing the method according to the invention. The control unit receives the data from the sensor and controls it. Furthermore, the control unit regulates the height adjustment of the vehicle, for example, by controlling air springs or transfers data to another control unit for height adjustment and / or controlling the air suspension. Finally, according to claim 20, the invention also relates to a vehicle with height adjustment, a chassis, at least one axle, a sensor according to claim 18 or a sensor for height measurement and a control unit according to claim 19.

[0040] Further optional features of the invention will become apparent from the description and the claims. Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. They show:

[0041] Fig. 1 is a bottom view of a vehicle with three axles,

[0042] Fig. 2 the vehicle according to Fig. 1 in a vertical section showing the axle with sensor for height measurement,

[0043] Fig. 3 Sensor and axis to explain the height measurement by time-of-flight detection of reflected signals,

[0044] Fig. 4 Signal peaks of reflected signals with intensities over distances during a first measurement,

[0045] Fig. 5 Signal peaks of reflected signals with intensities over distances in a second measurement,

[0046] Fig. 6 Signal peaks of reflected signals with intensities over distances in a third measurement,

[0047] Fig. 7 shows signal peaks of fixed points on the chassis as a so-called background map, determined from the measurements according to Figs. 4 to 6,

[0048] Fig. 8 shows the signal peaks according to Fig. 4 minus the background map according to Fig. 7, Fig. 9 shows the signal peaks according to Fig. 5 minus the background map according to Fig. 7,

[0049] Fig. 10 shows the arrangement of the sensor relative to the axis and the movement of the axis along a partial circular path to explain the difference between the distance between the sensor and the axis on the one hand and the vertical axis distance on the other.

[0050] Reference is first made to Figs. 1 and 2. A vehicle 10 with chassis 11, body 12, and three axles 13, 14, 15 is height-adjustable by air springs 16, 17. Specifically, a vertical distance VA between the axles 13, 14, 15 and the chassis 11 above them is adjustable by adjusting the air springs 16, 17. Such vehicles have been developed and used for decades for various purposes, in particular as commercial vehicles, including for the transport of goods and / or people. In particular, they are powered vehicles. However, they can also be trailer vehicles.

[0051] Modern vehicles of this type have an electronic control unit 18 for the air suspension. The control unit 18 can be connected to a brake control unit or be part of it.

[0052] As an input variable for controlling the height adjustment, the control unit 18 requires information about the current vertical distance aVA, or alternatively, the current distance aA (Fig. 3 only). This information is supplied by a sensor 19 on an underside 20 of the chassis 11. The sensor 19 here is a radar sensor, which is connected to the control unit 18 in a manner not shown in detail and which is a known component. If the sensor 19 protrudes downwards beyond the chassis 11, the vertical distance VA, aVA refers in particular to the sensor 19, as can be seen from Fig. 2.

[0053] Various types of radar sensors, either currently available or still under development, can be used. In particular, a frequency range of approximately 60 GHz can be used.

[0054] In particular, an FMCW (Frequency Modulation Continuous Wave) radar sensor is used as sensor 19. Such radar sensors are used in the automotive sector for distance detection and interior monitoring. For the present altitude measurement method, the AWRL6432 radar sensor from Texas Instruments can be used, for example.

[0055] Alternatively, a radar sensor operating according to the principle of pulsed radar can be used, in particular a pulsed coherent radar sensor. One such radar sensor is, for example, the A111 Pulsed Coherent Radar (PCR) sensor from Acconeer. The sensor 19 detects objects in a substantially conical, downward-directed area – in its radiation cone, which is referred to here as the signal cone 21 and has an aperture angle of, in particular, 10° to 30°. Primarily, an axle tube 22 of the axle 14 located below the sensor 19 is detected. At the same time, the signal cone 21 also detects a drivable surface below the axle 14, referred to here as the ground 23.

[0056] Similar sensors 19 are installed in differently configured vehicles. In particular, the vertical distance VA between the underside 20 and the axle tube 22 can vary, regardless of the height adjustment already provided. Calibration is therefore required when installing the sensor 19 and its initial commissioning. Calibration should be carried out automatically as far as possible. This would be relatively simple if the sensor 19 could only detect the axle 14 and the ground 23. In practice, additional parts or attachments may be present beneath the chassis 11 and in the area of ​​the axles 13 to 15, which are also located in the area of ​​the signal cone 21 and are also detected. As an example, Figs. 1 and 2 show a rod 24 below the sensor 19 and an attachment 25 on the axle 14. Rod 24 and attachment 25 are clearly located in the area of ​​the signal cone 21.

[0057] The distance measurement by sensor 19 is explained below with reference to Fig. 3. For simplicity, only sensor 19, axle tube 22 of axle 14, and the floor 23 are shown. A reflector (R) facing the sensor (19) can be arranged on the axle tube (22).

[0058] A radar signal with signal cone 21 is emitted by sensor 19 at time t0. At time t8, the radar signal reaches axle tube 22 and at time t14, the ground 23. Signals reflected by axle tube 22 and ground 23—not shown—reach sensor 19 at times t16 and t28 and are detected there. The times t8, t14, t16, and t28 represent only abstract time units relative to t0 and are intended to illustrate that the signal reflected by ground 23 arrives at sensor 19 significantly later than the signal reflected by axle tube 22, with a common signal emitted by sensor 19. In this case, each time point t16, t28 relative to time point t0 represents a propagation time and simultaneously a measure of the distance A between the sensor axis (t16-t0) and the sensor floor (t28-t0). A propagation time of 1 ns corresponds to a signal path of approximately 30 cm and thus a distance of approximately 15 cm.For the sake of simplicity, we will only refer to the distance and not the running time.

[0059] The reflected signals are not uniform, but vary in intensity. The intensity I depends at least on the nature of the detected object and the distance A. Each reflected signal therefore has an individual intensity I in addition to the individual value for the distance A. Intensity I and distance A can be summarized under the term signal peak; they are characteristic data of the same and are provided by sensor 19 for calculations and further processing in the vehicle or are processed in sensor 19.

[0060] The aforementioned reflected signals are signals received by sensor 19, resulting from the reflection of a transmitted signal. Depending on the technology used, sensor 19 transmits individual signals followed by pauses, so that the reflected signals can be reliably received within the pauses. Or sensor 19 transmits a continuous signal that is cyclically modulated. The reflected signals then also exhibit the modulations, but at different times.

[0061] Fig. 4 shows a diagram of the intensities I versus distances A of signal peaks P1 to P6 for a single transmitted signal. These can also be signal peaks for multiple transmitted signals, with the mean values ​​of the signal peaks determined. Signal peaks P1 to P6 relate to the following parts:

[0062] P1 Signal peak of a component fixedly arranged on the chassis 11, for example the linkage 24,

[0063] P2 signal peak of axle 14, namely axle tube 22,

[0064] P3 Signal peak of a component that is fixedly connected to the axis 13, for example the attachment part 25,

[0065] P4 signal peak of another component that is fixedly connected to the chassis 11, not shown in the figures, P5 signal peak of the ground 23, P6 signal peak of a depression in the ground 23, for example a pothole not shown.

[0066] As shown in Figs. 4 and 5, each signal peak P1-P6 is the maximum of a series of adjacent individual peaks e. Each signal transmitted by sensor 19 results in several reflected signals, depending on the shape and structure of a surface detected by the radar beam. For simplicity, three individual peaks are shown for each signal peak in Figs. 4 and 5, and no individual peaks are shown in Figs. 6-9. The number and distribution of the individual peaks, and their distances from one another, can vary considerably from those shown in the figures. The maximum of the individual peaks e is important. The maximum results in the corresponding signal peak P1-P6.

[0067] The possible calibration of the sensor 19 is explained below using Fig. 4 to 10:

[0068] After sensor 19 is installed on chassis 11, a series of measurements is performed. The results are evaluated. The evaluation is saved and used or made available for measurements to be performed during ongoing vehicle operation.

[0069] For the aforementioned series of measurements, the height adjustment of the vehicle 10 undergoes a so-called calibration run. This means that the air springs 16, 17 are controlled stepwise or continuously, so that the height adjustment runs through its entire range from minimum to maximum, or vice versa. Depending on the desired resolution of the various heights, more or fewer measurements are performed with the sensor 19 during the calibration run, and the signal peaks are saved as a raw signal data set.

[0070] Figures 4 to 6 show exemplary signal peaks from three different measurements. Each of the figures 4 to 6 corresponds to a raw signal data set for a specific altitude. The raw signal data set contains the intensity I and distance A for each signal peak.

[0071] Fig. 4 shows the signal peaks of a first measurement with the minimum height of the chassis 11 above the axle 14, corresponding to a distance A between the axle tube 22 and the sensor 19, for example 20 cm. This can be seen from the signal peak P2 at position A = 20 cm. In addition, the other signal peaks P1, P3, P4, P5, P6 are recorded at other positions a. P5 as the signal peak of the floor 23 is located at position A = 60 cm, i.e. 40 cm further away from the sensor 19 than the signal peak P2 of the axle 14. The signal peak P6 shown in dashed lines is a further 20 cm away and does not occur during a calibration drive in a controlled workshop environment with a level floor. In later ferry operation, the signal peak P6 can, for example, indicate a pothole.

[0072] Fig. 5 shows the signal peaks of a measurement with a distance from axis 14 that is 5 cm greater than in Fig. 4, i.e., with signal peak P2 at position A = 25 cm. Signal peaks P3, P5, and P6 are also shifted by 5 cm.

[0073] Fig. 6 shows the signal peaks of a measurement with a distance from axis 14 that is 15 cm greater than in Fig. 4, i.e., with signal peak P2 at position A = 35 cm. Signal peaks P3, P5, and P6 are also shifted by 15 cm.

[0074] When comparing Figs. 4 to 6, the signal peaks P1 and P4 are noticeable. These always have the same distance A, despite height adjustment. These must therefore be reflected signals from components that are fixedly connected to the chassis 11. Because the signal peaks P1 and P4 are constant, they can be easily determined by comparing the raw signal data sets and are shown separately in Fig. 7.

[0075] For altitude measurement using a radar sensor, the signal peaks P1 and P4 cause interference and are therefore referred to as the background and, in Fig. 7, as the background data set. The signal peaks P1 and P4 of the background data set are subtracted from all raw signal data sets created during the calibration run. This operation results in a corrected signal data set for Fig. 4, as shown in Fig. 8 with the remaining signal peaks P2, P3, and P5. Analogously, the corrected signal data set is obtained from Fig. 5, as shown in Fig. 9. In this way, a separate corrected signal data set is created for each altitude detected during the calibration run, which no longer contains the signal peaks of the background data set.

[0076] The corrected signal data sets can be cleaned of signal peaks that are not relevant for further considerations. Corrected signal data sets cleaned in this way are referred to here as peak data sets. The peak data sets contain at least the signal peaks P2 for axis 14 and, in particular, the signal peaks P5 for the ground. Advantageously, selected additional signal peaks are retained. This can facilitate plausibility checks. It is also possible to retain all signal peaks from the corrected signal data sets. The latter then also serve as the peak data sets. Example of a peak data set:

[0077] Measurement at air suspension minimum (analog Fig. 4)

[0078] Included signal peaks P2 P3 P5

[0079] Intensities I 35 16 16

[0080] Distances A 20 30 60

[0081] Peak labels Axis signal peak Ground signal peak

[0082] Theoretically, the signal peaks P2 and P5 for axle 14 and ground 23 should change synchronously during the calibration run, as long as the pressure in the tires 26 does not fluctuate. In fact, the distance A can vary for another reason. As shown in Fig. 10, the axle 14 is articulated, namely on trailing arms 27, which pivot about a pivot point 28. Depending on the chassis geometry and the arrangement of the sensor 19, a relevant effect can arise.

[0083] In the example shown, a smallest distance A1 is assumed between sensor 19 and axle tube 22. The axle tube 22 is not located vertically below the sensor 19. Therefore, the vertical distance VA1 between sensor 19 and axle tube 22 is significantly smaller. As the altitude increases during the calibration run, the axle tube 22 assumes different positions, for example with the distances A2 and A3 and corresponding vertical distances VA2 and VA3. Due to the specified conditions, the vertical distances VA1, VA2, VA3 differ from the distances A1, A2, A3 and also have different relative distances. It can therefore be useful to convert the distances A contained in the corrected peak data sets into the corresponding vertical distances VA depending on the known chassis geometry and the arrangement of the sensor 19.The peak data sets generated in this way are referred to here as linearized peak data sets and can be used instead of the peak data sets or in addition to them. The conversion—linearization—of distances into vertical distances is disclosed, for example, in EP 4 020 012 A1.

[0084] The linearization of the signal peaks can also be performed at an earlier point in time, namely as soon as it is determined which signal peak belongs to axis 14.

[0085] Before the calibration run, it is unclear which signal peaks will correspond to axle 14 and the ground 23. It is generally assumed that the signal peak of axle 14 will have the greatest intensity of all signal peaks, since the axle tube 22 is relatively large and only a short distance from the sensor 19. However, the surface of the axle tube 22 is curved, so the reflected signal is less intense than on a flat surface. To ensure that axle 14 generates the highest signal peak, it may be advisable to attach the radar reflector R to the axle tube 22. This can be determined through a preliminary test.

[0086] The intensity of the signal peak for floor 23 should be somewhat lower, but still very clear, at least in a controlled workshop environment with a level floor 23. Furthermore, in a controlled workshop environment, no signal peaks should occur that have a greater distance A than the signal peak for floor 23. With these precautions and considerations, at least the signal peaks P2 and P5 for axis 14 and floor 23 can be identified from the measurements during the calibration run. All other signal peaks relate either to add-on parts or the background mentioned above.

[0087] The signal peaks P1 and P4 that belong to the background can be determined by evaluating the raw signal data sets determined during the calibration drive. The irrelevant signal peaks outside the background data set can be at least partially excluded by comparing their sizes. For example, only the five highest signal peaks P1 to P5 are recorded in the raw signal data sets during the calibration drive, but not signal peaks with lower intensity. Alternatively, signal peaks with lower intensity are first excluded from the corrected signal data sets, the peak data sets, or the linearized peak data sets. After the entire calibration process has been completed, the background data set, the peak data sets, and / or the linearized peak data sets are saved and can be used later during ferry operation to determine the current altitude of the vehicle.In the stored peak data sets, the signal peaks P2 for axis 14 can be identified and noted as such. Each signal peak in the peak data sets can contain, in addition to the data for intensity I and distance A, the information "axis signal peak," if applicable. Similarly, the signal peak P5 for floor 23 can also contain the information "floor signal peak."

[0088] After calibration has been completed, a current altitude should be continuously determined during subsequent ferry operation. For this purpose, current signal peaks are cyclically recorded using sensor 19, and current peak data sets are generated. The current altitude can refer to a distance between chassis 11 and axle 14, a distance between chassis 11 and ground 23, or other distances that change when the height of the vehicle 10 is adjusted. Since the aforementioned distances are easily convertible into one another, for the sake of simplicity the current distance aA between sensor 19 and axle 14 or the current vertical distance aVA is assumed here as the current altitude. The current distance aA is contained in every current signal peak of axis 14 or can be derived from it. Within a current peak data set, in particular the highest current signal peak is assumed to be the current signal peak of axis 14.

[0089] Alternatively, the current signal peak of axis 14 can be determined from the relative position to other current signal peaks, in particular relative to the current signal peak of the base 23 or relative to other current signal peaks. The relative position of the current signal peaks of the current peak data set under consideration must match the relative position of the signal peaks in one or more of the stored peak data sets. By comparing the current peak data set with the stored peak data sets, the best-fitting stored peak data set can be determined. From this, the signal peak for axis 4, in particular also the signal peak for the base 23 and / or other signal peaks are known and can be adopted as current signal peaks. At least the current signal peak for axis 14 can be identified by comparing the peak data sets with the current peak data set.

[0090] After identifying the current signal peak of axle 14, the current distance aA between sensor 19 and axle 14 can be determined. The current vertical distance aVA can be calculated from the current distance aA either by taking into account the vehicle geometry and the arrangement of sensor 19 on chassis 11 or by using the linearized peak data sets.

[0091] The procedural steps of an exemplary calibration run and the subsequent ferry operation are summarized below.

[0092] Mounting of sensor 19 with calibration run:

[0093] Sensor 19 is attached to the chassis 11;

[0094] Sensor 19 is switched on;

[0095] Sensor 19 generates the first raw signal data set; optional: the highest signal peak is determined as the axis signal peak P2; calibration run to generate all desired raw signal data sets; comparison of the raw signal data sets to determine the background data set; generation of the corrected signal data sets and peak data sets;

[0096] Determination of axis signal peaks P2 and ground signal peaks P5; optional: determination of the measurement range for height adjustment; generation of linearized peak data sets.

[0097] Ferry operation after calibration of sensor 19:

[0098] Vehicle 10 ignition or power supply on;

[0099] Sensor 19 generates current raw signal data set; current peak data set is generated using background data set from calibration run; highest current signal peak is determined as current axle signal peak P2 or to determine the current axle signal peak P2, current peak data set is compared with peak data sets from calibration run; optional: for plausibility check, axle signal peaks P2 and ground signal peaks P5 of the peak data sets from calibration run are used; optional: for plausibility check, further signal peaks from calibration run are used;

[0100] Linearization of the axis signal peak P2; cyclic repetition of the previous steps.

[0101] List of reference symbols as part of the description:

[0102] 10 vehicles

[0103] 11 chassis

[0104] 12 Structure

[0105] 13 Axis

[0106] 14 Axis

[0107] 15 Axis

[0108] 16 air springs

[0109] 17 air springs

[0110] 18 Control unit

[0111] 19 Sensor

[0112] 20 subpage

[0113] 21 signal cones

[0114] 22 axle tube

[0115] 23 Floor

[0116] 24 rods

[0117] 25 Attachment

[0118] 26 tires

[0119] 27 trailing arms

[0120] 28 Pivot point aA distance

[0121] A current distance

[0122] A1 distance

[0123] A2 distance

[0124] A3 Distance aVA current vertical distance e single peaks

[0125] I Intensity

[0126] P1 signal peak

[0127] P2 signal peak

[0128] P3 signal peak

[0129] P4 Signal peak P5 Signal peak

[0130] P6 signal peak

[0131] R Reflector

[0132] TO Time

[0133] T8 time point

[0134] T14 Time

[0135] T16 Time

[0136] T28 Time

[0137] VA vertical distance

[0138] VA1 Vertical distance

[0139] VA2 vertical distance

[0140] VA3 Vertical distance

Claims

Patent claims:

1. A method for measuring height in a vehicle (10) with height adjustment, wherein a sensor (19) for measuring height is arranged on a chassis (11) of the vehicle (10) or is connected to the chassis (11) at a defined distance, the sensor (19) is arranged such that distances (A, aA) to an axle (14) of the vehicle (10) and in particular also to a floor (23) beneath the vehicle (10) can be detected, the sensor (19) transmits signals in the direction of the axle (14) and in particular the floor (23), receives reflected signals, and at least indirectly records intensities (I) of the reflected signals as well as propagation times between transmitted signals and reflected signals as signal peaks (P1 to P6), and the propagation times represent the distances (A, aA) of the sensor (19) to the axle (14) and in particular also to the floor (23) or can be converted into the distances (A, aA), characterized in thatthat the following steps are carried out for calibration: a) different heights of the vehicle (10) are controlled by the height adjustment, b) for each height controlled in step a), the propagation times and signal intensities of the reflected signals are determined, so that for each controlled height a raw signal data set consisting of propagation times and signal intensities of the signal peaks (P1 to P6) is created, c) from the propagation times and signal intensities determined in step b), the signal peaks (P1, P4) are identified, which always have the same propagation times regardless of the controlled height, d) the signal peaks (P1, P4) identified in step c) with always the same propagation times together result in a background data set, which is stored for further use.

2. Method according to claim 1, characterized in that the signal peaks of the background data set are subtracted from the signal peaks of all raw signal data sets, so that for each raw signal data set a corrected signal data set is created, which is stored.

3. Method according to claim 2, characterized in that in each corrected signal data set, signal peaks (P2, P5) are identified which relate to the axis (14) and in particular also to the ground (23), namely axis signal peaks (P2) and in particular also to the ground signal peaks (P5), 4. Method according to claim 3, characterized in that at least axis signal peaks (P2) and in particular also ground signal peaks (P5) of the corrected signal data sets are stored as peak data sets.

5. Method according to claim 3 or 4, characterized by the following steps for determining the axle signal peak (P2): e) for at least one height of the vehicle (10), several or all signal intensities (I) are compared with one another to determine a highest signal intensity, f) if the highest signal intensity can be determined, this is defined as part of the axle signal peak (P2), g) if the highest signal intensity cannot be determined, the axle (14) is provided with a reflector (R) to improve the reflection of the transmitted signals, h) after the reflector (R) has been applied, steps a) to c) are repeated.

6. Method according to claim 5, characterized in that the highest signal intensity is selected which is at least a defined amount higher than any other compared signal intensity (I).

7. Method according to claim 5 or 6, characterized in that the signal intensity (I) is selected as part of the ground signal peak (P5) which has a transit time higher by a defined amount than the axis signal peak (P2) and at the same time is higher by a defined amount than neighboring signal intensities.

8. Method according to one of claims 4 to 7, characterized in that vertical distances (VA, aVA) to the axis (14) are calculated and stored from the transit times of the axis signal peaks (P2) by linearization.

9. Method according to one of claims 1 to 8, characterized in that two or more different heights are controlled for calibration.

10. Method according to one of claims 1 to 9, characterized in that at least a minimum height and a maximum height of the vehicle (10) are controlled for calibration.

11. Method according to one of claims 1 to 10, characterized in that for calibration from a minimum height to a maximum height of the vehicle (10) or vice versa, all heights are controlled.

12. The method according to claim 10 or 11, characterized in that the transit time of the axle signal peak (P2) at minimum height of the vehicle (10) and the transit time of the axle signal peak (P2) at maximum height of the vehicle (10) define a measuring range which is stored.

13. Method according to one of claims 1 to 12, characterized in that a radar sensor is used as the sensor (19).

14. Method according to one of claims 1 to 13, characterized in that, in particular in the case of existing peak data sets and existing background data sets, after starting the vehicle (10) - at least one current raw signal data set is created, - a corresponding current peak data set is calculated by subtracting the existing background data set, - by comparing the current peak data set with the existing peak data sets or by selecting a highest current signal peak, the current axis signal peak (P2) is identified within the current peak data set.

15. The method according to claim 14, characterized in that a current vertical distance (aVA) to the axis (14) is calculated from the transit time of the current axis signal peak (P2) by linearization.

16. Method according to claim 14 or 15, characterized in that the identified current axis signal peak (P2) is checked for plausibility by - Checking whether the current peak data set contains a current ground signal peak (P5) which matches the identified current axis signal peak (P2) in terms of its runtime and / or signal intensity (I), or - Check whether the current peak data set contains other current signal peaks (P1 to P6) which match the identified current axis signal peak (P2) in terms of their runtimes and / or their signal intensities (I).

17. The method according to claim 16, characterized in that depending on the outcome of the plausibility check, another current signal peak is selected as the current axle signal peak (P2) or the steps specified in claim 11 are repeated, in particular for a different height of the vehicle (10).

18. Sensor (19) for measuring altitude in a vehicle (10), with software for carrying out the method according to one of claims 1 to 17.

19. Control device with software for carrying out the method according to one of claims 1 to 17.

20. Vehicle (10) with height adjustment, chassis (11), at least one axle (14), sensor (19) according to claim 18 or sensor (19) for height measurement and control device according to claim 19.

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