DE102022131957A1 - Method for measuring body height - Google Patents

Abstract

Method for measuring the body height of a motor vehicle by determining the distance between the body and a chassis part by means of a radar measurement, wherein the chassis part is exposed to environmental influences which can lead to deposits or contamination, wherein a transmitting and receiving device for radar waves transmits a radar signal directed at the chassis part and receives and processes reflected radar radiation, wherein during the evaluation of the reflected signals a correction of the distance calculated with the aid of the reflected signals is carried out (position correction) if a signal of reflected radar radiation is detected in an expected time interval, the base of which extends essentially within the expected time interval and which has at least two separately determinable signal peaks occurring one after the other over its course.

Description

The invention relates to a method for measuring the body height of a motor vehicle by determining the distance between the body and a chassis part by means of a radar measurement, the chassis part being exposed to environmental influences that can lead to deposits or contamination. A transmitting and receiving device for radar waves sends out a radar signal aimed at the chassis part, receives the reflected radar radiation and processes it, the reflected signals being evaluated using an algorithm stored in a control unit assigned to the transmitting and receiving device and the distance of the chassis part from the transmitting and receiving device, which can be calculated from the travel times of the transmitted and reflected signals, being determined. The invention also relates to a device for carrying out the method and to a motor vehicle with such a device.

Today's electronic chassis controls in motor vehicles, and especially in trucks, buses or trailers, rely on signals from sensors that can be used to measure the height of the superstructure or body above the axle. These measured values reflect current loading and driving conditions and thus represent the input signals that a level control system needs so that the control algorithm stored there can actually work.

Mechanical height sensors are known as relatively simple sensors, for example the frequently used angle of rotation sensors, with the help of which a spring travel is converted into a rotary movement via a lever mechanism, which allows a change in the height of a vehicle axle or a chassis element to be determined. The lever mechanism of such angle of rotation sensors is naturally relatively susceptible to damage or contamination. Icing in particular can affect such a system. In addition, appropriate installation space is required in the chassis area and noticeable tolerance chains must be taken into account.

The DE 102 55 438 A1 discloses, however, a device for determining the vehicle height above the road in the area of a wheel of a vehicle, in which a distance sensor is arranged for contactless measurement of a chassis part, in this case the wheel or the axle of the vehicle. One embodiment disclosed therein includes a radar sensor as a distance sensor. However, dirt or icing in the chassis area can sometimes significantly change the measurement result.

Another type of altitude sensor reveals the EN 10 2005 008 403 A1 . This describes a sensor device for measuring the spring travel of wheels or axles of vehicles, which is arranged inside an air spring bellows and emits a radar or high-frequency signal, which is received again after being reflected on a reference or reflection surface. Environmental influences are less relevant in such a system, but the sensors provided can only be integrated into the suspension components with relatively high effort.

The object of the present invention was therefore to provide a method for measuring the body height of a motor vehicle by means of radar measurement with a simply constructed sensor unit that is easy to mount in or on the vehicle, with the aid of which the body height or the distance of a chassis part from the body can be measured with as little influence as possible from environmental influences.

This problem is solved by the features of the main claim. Further embodiments are disclosed in the subclaims. Also disclosed is a device for carrying out the method and a motor vehicle with such a device.

When evaluating the reflected signals, a position correction, namely a correction of the distance calculated with the aid of the reflected signals, is carried out when a signal of reflected radar radiation is detected in an expected time interval, the base of which extends essentially within the expected time interval and which has at least two separately determinable signal peaks occurring one after the other over its course.

The method according to the invention is based on the consideration that the occurrence of two separately identifiable signal peaks occurring one after the other in the expected range can theoretically be attributed to the fact that a radar beam has irradiated not just one but several reflection surfaces or has penetrated different materials, but that the real distance of the chassis part to the transmitting and receiving device cannot be determined from a conventional evaluation of the distances between the supposed reflection surfaces that can be calculated from the travel times of the reflected signals. In these cases of the occurrence of two separately identifiable signal peaks occurring one after the other, it is assumed that the vehicle part is dirty and a position correction is carried out in the manner according to the invention. Only with the The inventive identification of the signal peaks (peak identification) and the proposed algorithms for position correction make it possible to achieve the degree of accuracy required for a vehicle's level control system, for example, in determining distance. However, the signal peaks can only be clearly determined if the extent or thickness of the contamination on the chassis part is greater than the resolution of the radar radiation.

zugrunde gelegt wird, wobei
µ = Permeabilität des Verschmutzungs- oder Ablagematerials,
ε = Permittivität des Verschmutzungs- oder Ablagematerials
c₀ = Ausbreitungsgeschwindigkeit der Radarwelle
n = Brechungsindex des Verschmutzungs- oder Ablagematerials.In a further development of the invention, the correction of the distance calculated with the aid of the reflected signals is carried out by using in the algorithm a propagation speed c _m of the radar waves in the pollution or deposit material, which depends on the irradiated pollution or deposit material and the associated refractive index, according to the relationship $$c_m={\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="DE102022131957A1\_0006.png"\; state="\{\{state\}\}">c</figure-callout>}}_0/n={\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="DE102022131957A1\_0006.png"\; state="\{\{state\}\}">c</figure-callout>}}_0/\sqrt{\mu \epsilon }$$

is used as a basis, whereby
µ = permeability of the contaminant or deposit material,
ε = permittivity of the contamination or deposit material
c ₀ = propagation speed of the radar wave
n = refractive index of the contamination or deposit material.

In another embodiment, the correction of the distance calculated with the help of the reflected signals (position correction) is carried out by using an estimated mean propagation velocity c _m in the algorithm, which depends on the irradiated contamination or deposit material and the associated refractive index and is valid for different materials.

Permeability is a measure of the permeability of material to magnetic fields, permittivity the dielectric conductivity of material. A good approximation value for various common contamination materials can be obtained if one assumes that contamination of chassis parts by ice formation occurs relatively frequently, namely by assuming a refractive index for ice known from the literature of n _ice = 1.78885 [ice: -20° C, for frequencies > 100 kHz].

• - aus einem ersten Abstand d₀, der aus der Laufzeit des Signals zum Zeitpunkt der ersten Intensitätsspitze/Signalspitze berechnet wird und der dem Abstand zwischen der Sende- und Empfangseinrichtung und der Oberfläche des Verschmutzungs- oder Ablagematerials entspricht,
• - und aus einem zweiten Abstand d_A, der aus der Laufzeit des Signals zum Zeitpunkt der zweiten Intensitätsspitze/Signalspitze berechnet wird,

wobei der reale Abstand d nach der Beziehung ermittelt wird $$d=d_0+\frac{1}{\sqrt{\mu \epsilon }}\left(d_A-d_0\right)$$

wobei
µ = Permeabilität des Verschmutzungs- oder Ablagematerials,
ε = Permittivität des Verschmutzungs- oder Ablagematerials.A further development is that the correction of the distance calculated using the reflected signals (position correction) is carried out by determining the real distance d of the chassis part from the transmitting and receiving device using the algorithm

• - a first distance d ₀ , which is calculated from the propagation time of the signal at the time of the first intensity peak/signal peak and which corresponds to the distance between the transmitting and receiving device and the surface of the contaminant or deposited material,
• - and from a second distance d _A , which is calculated from the transit time of the signal at the time of the second intensity peak/signal peak,

where the real distance d is determined according to the relationship $$d={\mathrm{<figure-callout\; id="0"\; label="d"\; filenames="DE102022131957A1\_0006.png"\; state="\{\{state\}\}">d</figure-callout>}}_0+\frac{1}{\sqrt{\mu \epsilon }}\left(d_A-d_0\right)$$

where
µ = permeability of the contaminant or deposit material,
ε = permittivity of the contaminant or deposit material.

The distance d _A is the distance resulting from the travel time of the signal after reflection from the surface of the chassis part which is located below a deposit or contamination on the chassis part.

Such a position correction makes it possible to determine the actual distance of a chassis part that reflects a radar beam aimed at it with sufficient accuracy even if the chassis part is covered with foreign material, for example if it is dirty or has traveled. If, as was previously the case in the state of the art, the measured travel times of the signals were converted to the actual distances without correction and also used as a value for the distance of the chassis part, this would very quickly result in information that would be completely unsuitable for level control with increasing contamination and, depending on the thickness and type of deposit/contamination, could deviate by several centimeters from the actual distance value. In this respect, the method according to the invention using radar distance measurement achieves a significant improvement in level control even under unfavorable environmental conditions.

A further development of the method is that if a threshold value for the intensity of the reflected radar radiation is undershot or if a threshold value for the distance between the signal peaks is exceeded, an error signal is generated by the algorithm stored in the control unit. If the signal width, characterized by the distance between the signal peaks, is too large or the intensity of the signal is too low, this can be an indication of a too severe contamination, which can no longer be compensated for by a position correction according to the invention. Such an error signal can then be the trigger for indicating to the driver of the vehicle that the signal quality has fallen below a threshold below which exact level control can no longer be ensured and that the chassis part must therefore be cleaned.

A further development of the method consists in the transmission and reception device for radar waves sending out a radar signal aimed at an axle, receiving the reflected radar radiation and processing it in its control unit using the algorithm. Since the axle of a vehicle is essentially an unsprung mass or one that is only sprung by tires and is therefore more or less directly in contact with the road surface via the tires or wheels, measuring the distance of an axle is a particularly simple way of carrying out the method.

This also applies to a device suitable for carrying out the method for measuring the body height of a motor vehicle by determining the distance between the body and a chassis part covered in deposits or dirt using a radar measurement, in which a transmitting and receiving device for radar waves arranged on the body sends out a radar signal directed at an axle and receives and processes radar radiation reflected from the surfaces of the axle and/or the deposits there. The connection of a radar sensor to the body or to yellow parts belonging to the body in conjunction with the radar radiation directed at an axle for distance/height measurement represents a structurally simple solution that can be implemented in almost all models, particularly in the case of trucks or trailers.

A further embodiment of the device according to the invention for carrying out the method consists in that the transmitting and receiving device for radar waves is arranged in such a way that the radar signal is directed at an angle to the vehicle axle, so that deposits adhering to the axle are not penetrated or are only penetrated in peripheral areas. In the structurally simple design already described above with a sensor attached to the body that applies radar radiation to a vehicle axle, relatively heavy dirt can, under certain circumstances and over time, settle on the top of the axle and affect the measurement or lead to the error signals already mentioned. A sensor that sends a radar beam directed at an angle to the axle does not penetrate the maximum thickness of the deposit/dirt, but at most an peripheral area. This significantly reduces the possibility of incorrect measurements of the distance between the sensor and the axle.

A further development of the device according to the invention consists in that the transmitting and receiving device is operated with high-frequency radar radiation in the millimeter wave range. For example, a coherence pulse radar with 60 GHz or 77 GHz is suitable here, but a continuous wave radar (FMCW - Frequency Modulated Continuous Wave Radar) can also be used.

A further embodiment of the device according to the invention for carrying out the method consists in that the transmitting and receiving device for radar waves has a lens to improve the signal-to-noise ratio (SNR). This improves the detection of signal peaks, which then form the basis for the position correction according to the method according to the invention.

The device according to the invention is particularly suitable for use in the chassis of trucks, i.e. of motor vehicles of larger dimensions, also in the area of the chassis assemblies, where other distance measuring systems require a relatively large amount of effort.

• 1 eine prinzipiellen Darstellung einer erfindungsgemäße Messeinrichtung,
• 2 die Grundlagen des erfindungsgemäßen Verfahrens anhand eines dem Meßprinzip geometrisch angepassten Diagramms, welches die den jeweiligen Abständen zugeordneten Intensitäten der reflektierten Signale darstellt.

The invention will be explained in more detail using an embodiment.

• 1 a schematic representation of a measuring device according to the invention,
• 2 the principles of the method according to the invention using a diagram geometrically adapted to the measuring principle, which shows the intensities of the reflected signals assigned to the respective distances.

1 shows in the form of a basic representation a measuring device 1 according to the invention for measuring the body height 2 relative to the axle 3 of a motor vehicle, here a truck not shown in detail, which rolls on a roadway 9 with its wheels 8 located on the axle 3.

The measuring device has a radar sensor 4 designed as a transmitter-receiver, here a coherence pulse radar with 60 GHz, which emits a pulsed radar beam onto a vehicle part, namely onto the vehicle axle 3 of the truck. The sensor 4 is arranged on the body 5 and sends a radar signal 6 directed towards the axle 3, which is reflected both by surfaces of the axle 3 and by deposits/contamination on the axle. dirt 7 and penetrates the latter.

Other chassis parts such as suspensions, handlebars, suspension, etc. are not shown here for the sake of clarity.

2 clarifies the basics of the measuring principle of the method according to the invention using a basic representation in which the transmitting and receiving device for radar waves, here the radar sensor 4, sends out a radar signal directed at the axis 3 and receives and processes the reflected radar radiation. The reflected signals are evaluated and determined using an algorithm stored in a control unit assigned to the transmitting and receiving device.

For this purpose, the 2 a geometrically adjusted diagram is inserted, which shows the curves of the reflected radar signals and the intensities of the reflected signals assigned to the respective distances, namely their signal peaks, the so-called "peaks". Also shown is again a contamination/deposit 7, which is located on the axis 3. In comparison to 1 The display here is rotated by 90°.

Looking at 2 the individual signal peaks or the curves of the reflected signals, one first recognizes the curve 10 with its signal peak 10a, which corresponds to a reflected signal that would be received if there were no contamination 7 on the axle 3. The signal peak 10a would in this case represent the actual distance d of the axle 3 or its axle surface from the sensor 4. The actual distance d of the axle 3 corresponds to the body height 2 in 1 .

However, with the presence of contamination 7, the reflected signal produces a curve 11 with its signal peaks 11a to 11d.

This is where the method according to the invention comes into play, in which, when evaluating the reflected signal 11, a correction of the distances calculated using the reflected signals or their signal peaks 11a to 11c is carried out when a signal 11 of reflected radar radiation is detected in an expected time interval 12, the base of which extends essentially within the expected time interval 12 and which has at least two separately determinable signal peaks 11a and 11b occurring one after the other over its course. The remaining signal peaks 11c and 11d of the signal 11 reflected from a dirty axle 3 are outside the expected time interval 12 and are therefore not considered.

If one were to determine only the distances d ₀ and d _A to the transmitting and receiving device 4 corresponding to the travel times of the signal peaks 11 a and 11 b of the reflected signal 11 and to assume the second signal peak 11 b as the actual distance of the axis 3, this in the usual assumption that the first signal peak 11 a corresponds to the surface reflection of the dirt, this would result in a position error 13 which deviates considerably from the actual value of the axis distance 2. Only with a position correction according to the method according to the invention can the actual axis distance d or the body height 2 be determined.

Reference symbol (part of the description)

1

Measuring device

2

Body height relative to axle

3

axis

4

Radar sensor

5

body

6

Radar signal

7

Deposits/contamination on the axle

8th

wheel

9

roadway

10

Signal curve of the reflected signal without contamination

10a

Peak of the signal curve 10

11

Signal curve of the reflected signal with contamination

11a - d

Peaks of the signal curve 11

12

Expected time interval

13

Position error

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 10255438 A1 [0004]
• DE 102005008403 A1 [0005]

Claims (11)

Method for measuring the body height of a motor vehicle by determining the distance between the body and a chassis part by means of a radar measurement, the chassis part being exposed to environmental influences which can lead to deposits or contamination, a transmitting and receiving device for radar waves emitting a radar signal directed at the chassis part and receiving and processing reflected radar radiation, the reflected signals being evaluated with the aid of an algorithm stored in a control unit assigned to the transmitting and receiving device and the distance of the chassis part from the transmitting and receiving device which can be calculated from the travel times of the reflected signals being determined, characterized in that when evaluating the reflected signals, a correction of the distance calculated with the aid of the reflected signals is carried out (position correction) if a signal of reflected radar radiation is detected in an expected time interval, the base of which extends essentially within the expected time interval and which has at least two separately determinable signal peaks occurring one after the other over its course. Procedure according to Claim 1 , in which the correction of the distance calculated with the aid of the reflected signals (position correction) is carried out by using in the algorithm a propagation speed c _m of the radar waves in the pollution or deposit material, which depends on the irradiated pollution or deposit material and the associated refractive index, according to the relationship $$c_m=c_0/n=c_0/\sqrt{\mu \epsilon }$$

is used as a basis, where µ = permeability of the contamination or deposit material, ε = permittivity of the contamination or deposit material c ₀ = propagation speed of the radar wave n = refractive index of the contamination or deposit material. Procedure according to Claim 1 , in which the correction of the distance calculated with the aid of the reflected signals (position correction) is carried out by using an estimated mean propagation velocity c _m in the algorithm, which depends on the irradiated contamination or deposit material and the associated refractive index and is valid for different materials. Method according to one of the Claims 1 until 3 , in which the correction of the distance calculated with the aid of the reflected signals (position correction) is carried out by determining a real distance d of the chassis part from the transmitting and receiving device with the aid of the algorithm - from a first distance d ₀ , which is calculated from the propagation time of the signal at the time of the first intensity peak/signal peak and which corresponds to the distance between the transmitting and receiving device and the surface of the contamination or deposit material, - and from a second distance d _A , which is calculated from the propagation time of the signal at the time of the second intensity peak/signal peak, the real distance d being determined according to the relationship $$d=d_0+\frac{1}{\sqrt{\mu \epsilon }}\left(d_A-d_0\right)$$

where µ = permeability of the contaminant or deposit material, ε = permittivity of the contaminant or deposit material. Method according to one of the Claims 1 until 4 , in which an error signal is generated by the algorithm stored in the control unit if a threshold value for the intensity of the reflected radar radiation is undershot or if a threshold value for the distance between the signal peaks is exceeded. Method according to one of the Claims 1 until 5 , in which the transmitting and receiving device for radar waves transmits a radar signal directed onto an axis, receives the reflected radar radiation and processes it in its control unit. Device for measuring the body height of a motor vehicle by determining the distance between the body and a chassis part covered with deposits or dirt by means of a radar measurement according to one of the Claims 1 until 6 , in which a transmitting and receiving device for radar waves arranged on the body transmits a radar signal directed at an axle and receives and processes radar radiation reflected from surfaces of the axle and/or the deposits there. Facility according to Claim 7 , in which the transmitting and receiving device for radar waves is arranged in such a way that the radar signal is directed at an angle to the vehicle axis, so that deposits adhering to the axis are not penetrated or are penetrated only in peripheral areas. Facility according to Claim 7 or 8th , in which the transmitting and receiving device is operated with high-frequency radar radiation in the millimeter wave range. Facility according to one of the Claims 7 until 9 , in which the transmitting and receiving device for radar waves has a lens to improve the signal-to-noise ratio. Motor vehicle, preferably truck, with a device according to one of the Claims 7 until 10 .

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