DE102019115719A1 - Driver assistance system for detecting a state variable of an air using a laser beam and a radar wave - Google Patents

Abstract

The invention relates to a driver assistance system (1) for a vehicle (2) for detecting an environment (34) of the vehicle (2), the driver assistance system (1) comprising an oscillator (4) which generates a first radar shaft (10), a first Laser (5), which generates a first laser beam (6), a converter (7) and a phase-locked loop (33) with a reference variable and a phase of the first radar wave (10) as a controlled variable, wherein the converter (7) comprises a first partial beam ( 8) of the first laser beam (6) into a second radar wave (9), a phase of the second radar wave (9) is the reference variable and the driver assistance system (1) the first radar wave (10) and a second sub-beam (11) of the first laser beam (6) simultaneously emits to determine at least one value of a state variable of an air of the environment (34), at least based on a difference between a transit time of the first radar wave (10) and a travel time of the second sub-beam (11).

Description

The invention relates to a driver assistance system for a vehicle for detecting an environment of the vehicle with a laser.

Such a driver assistance system is from the US 2014/0104051 A1 known. Therein, the laser is used to determine a distance between an adjacent further vehicle to the vehicle. A similar application is found in the US 7,742,152 B2 described laser. Furthermore, it is known to detect a state of an air directly surrounding the vehicle with the aid of temperature and humidity sensors of the vehicle. However, if a safety of the vehicle is to be further increased, then it is helpful to detect at least one state variable of the air in a space located in front of the vehicle. For example, with knowledge of the state variable, a probability of black ice formation on a roadway can be calculated.

Based on this, it is the object of the present invention to improve a driver assistance system for a vehicle for detecting an environment of the vehicle such that a state variable of an air of a space located ahead of the vehicle can be determined.

This object is achieved with a driver assistance system having the features of claim 1 and a method having the features of claim 6. Advantageous embodiments of the driver assistance system and further developments of the method are the subject of the dependent claims.

To solve the problem, a driver assistance system for a vehicle for detecting an environment of the vehicle is proposed. The driver assistance system includes an oscillator that generates a first radar wave, a first laser that generates a first laser beam, a converter, and a phase locked loop. The phase-locked loop has a reference variable and a controlled variable. The controlled variable is a phase of the first radar wave. The converter converts according to the invention a first partial beam of the first laser beam into a second radar wave. Furthermore, a phase of the second radar wave is the reference variable of the phase locked loop. The driver assistance system simultaneously transmits the first radar wave and a second sub-beam of the first laser beam in order to determine at least one value of a state variable of an ambient air, at least based on a difference between a transit time of the first radar wave and a travel time of the second sub-beam.

By the respective phase is meant a current angle, measured in radians, of a first and second oscillation, respectively, which generate the first and the second radar wave, respectively. The environment of the vehicle may be further vehicles, air of a directly adjacent to the vehicle space that touches the vehicle, and especially air of a room that is in the direction of travel in front of the vehicle and does not touch the vehicle, hereinafter referred to as the front room designated include. The state quantity of the air is preferably an average temperature of the air in the front space.

The converter preferably comprises a crystal, in particular indium antimonite, and more preferably indium phosphite antimonite. If the first partial beam strikes the crystal, the crystal is converted into an excited state. When the crystal returns from its excited state to its ground state, the crystal releases some of the energy in the form of radar radiation.

The radar radiation here comprises the second radar wave, wherein an energy of the second sub-beam, which is calculated from the product of the Planck constant h and a frequency of the first sub-beam, an integer multiple of an energy of the second radar wave, which consists of a product of the Planck Constant h and a frequency of the second radar wave is calculated.

In order for the first partial beam to reach the converter on the one hand and for the other to be emitted in the direction of an object in front of the vehicle, the first laser beam is converted into at least a first partial beam, which is conducted to the converter, and into a second partial beam, which an output of the driver assistance system is divided. The converter preferably comprises a holder or housing which secures and aligns the crystal.

To generate the second radar wave, the converter may comprise a doped glass fiber, particularly advantageously an ytterbium-doped glass fiber. The converter generates from the first partial beam by inelastic scattering, preferably by Brillouin scattering, the second radar wave. In order to generate the second radar wave, in addition to the first sub-beam according to a special variant, a further laser beam which is in phase synchronization with the first sub-beam can be used. The further laser beam can preferably be divided into a first partial beam of the further laser beam and a second partial beam of the further laser beam. The second partial beam of the further laser beam is emitted in this variant simultaneously with the first radar wave and the second partial beam. In a further variant, the converter consists of a photodiode, which of the first partial beam and the another laser beam or the first partial beam and the first partial beam of the further laser beam is illuminated.

Via a stripline, the second radar wave can be directed to an input of the phase locked loop. The transit time of the first radar wave, hereinafter referred to as the first transit time, and the transit time of the second sub-beam, referred to below as the second transit time, can be determined as follows. Preferably, a first time in which the first radar wave and the second partial beam are transmitted simultaneously in the direction of the object is detected. Following this, a second point in time at which the first radar wave reflected by the object is received by a first detector and a third point in time at which the second partial beam reflected by the object is received by a second detector are detected. The first runtime is the time difference between the second and the first time and the second runtime is the time difference between the third and the first time.

$${\left(\text{n}-1\right)}_{\text{tp}}={\text{K}}_{\mathrm{\lambda }}{\text{D}}_{\text{tp}},$$

$${\text{D}}_{\text{tp}}=\frac{\text{p}\left[1+\text{p}\left(0.817-0.0133\text{t}\right)\times {10}^{-6}\right]}{\left(1+0.0036610\text{t}\right)}$$

$${\left(\text{n}-1\right)}_{\text{tp}}={\left(\text{n}-1\right)}_{\text{s}}\frac{{\text{D}}_{\text{tp}}}{{\text{D}}_{\text{s}}},$$

$${\left(\text{n}-1\right)}_{\text{tp}}=\frac{\text{p}{\left(\text{n}-1\right)}_{\text{s}}}{720.775}•\frac{\left[1+\text{p}\left(0.817-0.0133\text{t}\right)\times {10}^{-1}\right]}{\left[1+0.0036610\text{t}\right]}.$$

wobei D_s ein Dichtefaktor für Luft unter Standardbedingungen mit dem Wert 720,775, n ein von der Wellenlänge abhängiger Dispersionsindex und c₀ die Vakuumlichtgeschwindigkeit ist und K_λ aus der Tabelle V auf Seite 29 in [3] und den Gleichungen 5.1-5.3 in [3] entnommen werden kann. Der Druck p der Luft wird in Torr und Temperatur der Luft t in °C gemessen.The invention is based on the idea that the speed of light of an electromagnetic wave in air depends on a value of the state variable and values of further state variables of the air and a wavelength of the electromagnetic wave. The state variable and the further state variables can be, for example, a temperature, a pressure, a relative humidity and a CO ₂ content of the air. Computational rules that describe a relationship between these state variables and the speed of light in air are in the publication "The Refractive Index of Air," Metrologia 2 (1966), pages 71-80, by B. Edlen [1] and in the publication "The Refractivity of Air", Journal of Research of the National Bureau of Standards, Vol. 86 , No. 1, January-February 1981 , by Frank E. Jones [2] and in the publication "The refraction and dispersion of air for the visible spectrum", Barrell, H .; Sears, JE, Jr., Phil. Trans. Roy. Soc. London, A238: 1-64; 1939, [3] described. For example, the wavelength-dependent speed of light c _λ can be calculated or approximated by a solution of the following equation system, which is described in [2]: $${\text{c}}_{\mathrm{\lambda }}=\frac{{\text{c}}_0}{\text{n}}.$$

$${\left(\text{n}-1\right)}_{\text{tp}}={\text{K}}_{\mathrm{\lambda }}{\text{D}}_{\text{tp}}.$$

$${\text{D}}_{\text{tp}}=\frac{\text{p}\left[1+\text{p}\left(0817-0.0133\text{t}\right)\times {10}^{-6}\right]}{\left(1+0.0036610\text{t}\right)}$$

$${\left(\text{n}-1\right)}_{\text{tp}}={\left(\text{n}-1\right)}_{\text{s}}\frac{{\text{D}}_{\text{tp}}}{{\text{D}}_{\text{s}}}.$$

$${\left(\text{n}-1\right)}_{\text{tp}}=\frac{\text{p}{\left(\text{n}-1\right)}_{\text{s}}}{720775}•\frac{\left[1+\text{p}\left(0817-0.0133\text{t}\right)\times {10}^{-1}\right]}{\left[1+0.0036610\text{t}\right]},$$

where D _{s is} a density factor for air under standard conditions of 720,775, n is a wavelength dependent dispersion index and c _{0 is} the vacuum light velocity and K _{λ is} from Table V on page 29 in [3] and equations 5.1-5.3 in [3]. The pressure p of the air is measured in Torr and temperature of the air t in ° C.

A change in a value of the state variable or the further state variables each have a different influence on a change in the speed of light. In this case, a percentage change in the temperature, the pressure, the relative humidity and the CO ₂ content each act in descending order on a change in the speed of light. In addition, the respective values of the state quantity and the other state variables of the air in the front space usually vary in different degrees along a traveling direction of the vehicle. For example, a change in pressure along the direction of travel is usually lower in percentage than a change in temperature or relative humidity along the direction of travel. If, in addition to the first and second running times, additional values of the further state variables are measured with the aid of sensors of the vehicle, for example a value of the pressure, the relative humidity and the CO ₂ content, the mean temperature of the air can be determined with the aid of all measured variables of the front room are approximated.

This makes it possible to approximate the environmental conditions of the air of the front space, and preferably also a state of a surface of a roadway on which the vehicle is moving, especially in critical weather conditions, such as in black ice or fog. For example, in weather conditions where ice formation is very likely, a minimum change in relative humidity or temperature can cause black ice formation.

Determining the state variable of the air with the aid of the proposed driver assistance system now has several advantages.

By detecting the first and second transit times and in that one wavelength of the first radar wave and a wavelength of the second With the aid of the transit times and the wavelengths, at least two values of interpolation points of at least one of the abovementioned calculation rules for the calculation of the wavelength-dependent speed of light can be determined. With the help of the calculation rules, a system of equations for determining the average temperature of the air of the front room can be set up, which records the first and second transit times and values of the further state variables of the air, such as the relative humidity, the CO ₂ content and / or the Contains pressure.

According to a first variant, it is possible that the values of the further state variables of the air are measured by means of the sensors.

According to a second variant, it may be provided that the values of the further state variables of the air are assumed to be constant for the calculation of the value of the state variable. In this second variant of the calculation of the value of the state variable, preferably values of the further state variables are used which have the average annual air in a region in which the vehicle is at a time in which the transit times are measured. Although the second variant represents a cost-effective method for calculating the value of the state variable, it is inaccurate compared to the first variant.

The wavelength of the radar wave is about 1 mm to 1 cm, hereinafter referred to as the first wavelength, and the wavelength of the second partial beam about 1 nm to 1 .mu.m, hereinafter referred to as the second wavelength. Due to the fact that the second wavelength is smaller than the first wavelength by a factor of about 1000, the two interpolation points are relatively far apart in a possible space from possible interpolation points. This can have the advantage that the system of equations is particularly well conditioned, with good conditioning meaning that an inaccuracy of a single variable, in this case the first and / or second wavelength, relatively little to a change in a variable to be calculated, here the mean Temperature, based on the system of equations.

Another advantage is that the first radar wave is generated by the phase locked loop controlled oscillator using the second radar wave as a reference variable. This causes the first radar wave to each have a fixed phase relationship to the first laser beam, the first and second partial beam and a frequency fluctuation over a time interval of the first radar wave is significantly lower than when using a quartz oscillator as a clock generator for the oscillator. A fixed phase relationship between a first and a second wave means that a phase of the first wave can be described by a product with a phase of the second wave as a first factor and a constant number as a second factor.

Furthermore, if two different quartzes were used, inaccuracy of a particular quartz would be variable with changing environmental conditions, whereby respective frequencies generated by the quartz would be differentially stable over a period of time and could lead to high inaccuracies in measurement.

On the other hand, in the proposed driver assistance system, the first laser functions as a clock for the oscillator, whereby an inaccuracy of the oscillator and thus a phase noise of the first wave can be reduced. The first radar wave having the first wavelength can be made more stable by the second radar wave, i. With a lower phase noise than is generated with a quartz crystal, the value of the state quantity can be determined more precisely.

In an advantageous embodiment, it is provided that the phase-locked loop has at least one first frequency divider with which a frequency of the first radar wave can be set. Due to the fact that the frequency of the first radar wave is adjustable, further values of interpolation points of the calculation rules can be determined. The same advantage arises when the first laser is designed as a tunable laser with which a frequency of the first laser beam can be changed. It is also possible that the converter is adjustable and with the adjustable converter, a frequency of the second radar wave is variable, resulting in the frequency of the first radar wave due to a coupling via the phase locked loop.

However, a particularly simple way of changing the frequency of the first radar wave is provided by the first frequency divider. The first frequency divider is preferably arranged in a feedback path from an output of the oscillator and an input of a phase comparator of the phase locked loop. Advantageously, the phase locked loop has a second frequency divider located in front of a first input of the phase comparator to divide a frequency of the second radar wave. Both frequency dividers can divide a respective input-side frequency by an integer and each output at its output an electromagnetic wave having a frequency equal to a result of this division.

With the aid of the first and the second frequency divider, it is possible to generate the first radar wave with a frequency whose value is in an adjustable ratio to a value of the frequency of the second radar wave and in particular of the first laser beam. The ratio can be given by a quotient, where a dividend of the quotient is a natural number n and a divisor of the quotient is a natural number m. The natural number m indicates the divider ratio of the first frequency divider and the natural number n indicates a divider ratio of the second frequency divider. The values m and n can each be adjusted variably, preferably by means of a control unit, at the first or second frequency divider.

In an advantageous embodiment, the driver assistance system has a second laser which is coupled to the first laser such that the first laser can excite the second laser by means of the first laser beam, the first or second partial beam. The second laser generates a second laser beam having a wavelength different from the second wavelength. The second laser beam has a fixed phase relationship with the first laser beam. This is achieved by coupling the two lasers. The driver assistance system transmits the second laser beam simultaneously with the second partial beam and calculates a third transit time of the second laser beam analogously to the transit time of the second partial beam.

Since the second laser beam has a wavelength which is different from the second wavelength and therefore the second laser beam has a different speed of light in the front space than the second partial beam, a further independent equation of the system of equations for determining the value of the state variable can be formed with the aid of the third transit time. This makes it possible to dispense with at least one measurement of a value of one of the further state variables, for example, a measurement of the value of the pressure.

In a further development, it is provided that the driver assistance system has a further oscillator for generating a third radar wave and a further phase locked loop. The further phase-locked loop controls the further oscillator such that the third radar wave has a fixed phase relationship to the first radar wave and the second sub-beam and has a different frequency than the first radar wave. The driver assistance system transmits the third radar wave, the first radar wave and the second sub-beam simultaneously. This development gives the same advantages as the above-mentioned supplement of the driver assistance system by the second laser, since the wavelength of the third radar wave is different from the first radar wave. Advantageously, in this development, a measurement of the relative humidity can be dispensed with.

To achieve the object, a method for detecting an environment of a vehicle is further proposed with the following steps. In a first step, the first laser beam is generated with the first laser. In a second step, the second radar wave is generated by means of the converter and the first sub-beam of the first laser beam. In a third step, the first radar wave is generated by means of an oscillator, wherein the oscillator is controlled by means of the phase locked loop and a phase of the first radar wave is used as a controlled variable and a phase of the second radar wave as a reference variable. In a fourth step, the first radar wave and the second sub-beam of the first laser beam are emitted simultaneously. In a fifth step, a respective transit time of the first radar wave and of the second sub-beam is measured between the driver assistance system and an object on which the second sub-beam and the first radar wave are reflected. In a sixth step, a value of a state variable of the ambient air is determined based on the transit times.

The value of the state variable can, as described above, be determined with the aid of the equation system and the measured transit time of the first radar wave and the transit time of the second sub-beam.

An advantageous embodiment of the method provides that the steps one to six are performed several times and at least based on the respective measured maturities a model is generated. The model takes into account at least one propagation behavior of the second partial beam and / or the first radar wave as a function of the state variable.

Generating the model means that functions already exist between input values of the model and at least one output value of the model before generating the model, and during the generation, values of parameters of the functions are adapted to values of several data sets. In this case, a single data record is preferably generated when steps one to six have been completed. The individual data record has at least the two transit times and the value of the state variable. Another record is preferably generated when steps one through six have been performed a second time.

The functions take into account a propagation behavior, in particular the speed of light of the first radar wave and the speed of light of the second sub-beam, and can be combined in one first variant contain the above calculation rules. According to a second variant, the functions may also be functions of a neural network which model the propagation behavior after training of the neural network.

According to an advantageous development, when the model is generated, a measured value of the state variable is included. The measured value is measured at a time when the vehicle is in an air volume in which previously the second sub-beam and the first radar wave have propagated.

In this development, the value of the state variable is measured after measuring the respective transit times. Since the vehicle is in the said air volume at the time of measuring the value of the state variable, the measured value of the state variable corresponds approximately to a real value of the state variable which was previously determined with the aid of the measured transit times and the calculation rules described above. Preferably, a difference between the measured value and the determined value of the state variable is detected, and the model, in particular the values of the parameters of the functions, is adapted on the basis of the difference. This development thus makes it possible to correct the model.

A particular embodiment provides that at least one first material property of the object is known when the model is generated, and the first or a further material property of an object to be detected is recognized by means of the model, the measured transit times and at least one measured value of the state variable.

In this embodiment, the model preferably has the measured transit times, the measured value of the state variable, and preferably further values of the further state variables of the air as input values and a material property to be detected of the object to be detected as output value.

Preferably, a modeled intensity of a received signal of the transmitted second partial beam and / or the first radar wave is determined with the aid of the model. Subsequently, a comparison of the modeled intensity with a measured intensity of a received signal of the emitted second partial beam or of the first radar wave is preferably carried out, and the first or a further material property of a further object is determined on the basis of a result of the comparison and a measured value of the state variable.

The advantage of this further development of the method is that, in addition to the measured transit times, the measured intensities of the two received signals are additionally used. Because the transit time is independent of the measured intensities of the received signals, with the aid of the measured intensities of the received signals there is at least one further piece of information via which the first or the further material property can be detected.

One possible application may provide, for example, that it is detected on the basis of the measured intensities of the two received signals that the object has a metallic vapor-deposited surface on which the second partial beam is reflected very well, and the surface is applied on a plastic absorbing the first radar wave. According to a second possible application, it can be detected on the basis of the measured intensities of the two received signals whether the object has a matt black lacquered iron layer which generates a strong radar echo but absorbs large parts of the second partial beam. Furthermore, the measured transit times may be used to determine at which distance a material with the first or the further recognized material property is related to the driver assistance system.

A further variant of the method may provide that a first state of a roadway on which the vehicle is located is determined at least on the basis of the value of the state variable. Furthermore, at least by means of a wheel speed sensor of a wheel of the vehicle and a friction coefficient model for determining a coefficient of friction between the wheel and the roadway, a second state of the roadway can be determined. Subsequently, a comparison between the first state of the roadway and the second state of the roadway can be carried out and the model can be corrected on the basis of a result of the comparison.

• 1 ein Fahrzeug mit einem Fahrerassistenzsystem zur Erzeugung eines Laserstrahls und einer Radarwelle,
• 2 das Fahrerassistenzsystem aus 1 mit einem Laser, einem Konverter und einer Phasenregelschleife,
• 3 ein Verlauf der Radarwelle und ein Verlauf der zum Laserstrahl korrespondierenden elektromagnetischen Welle,
• 4 ein weiteres Fahrerassistenzsystem mit zwei Lasern, einem Konverter und einer Phasenregelschleife.

Further advantages, features and details of the invention will become apparent from the following description and from the figures. In this case, a reference symbol used repeatedly denotes the same component. The figures show schematically in:

• 1 a vehicle with a driver assistance system for generating a laser beam and a radar wave,
• 2 the driver assistance system 1 with a laser, a converter and a phase locked loop,
• 3 a course of the radar wave and a course of the laser beam corresponding to the electromagnetic wave,
• 4 Another driver assistance system with two lasers, a converter and a phase locked loop.

1 shows a driver assistance system 1 for a vehicle 2 to capture an environment 34 of the vehicle 2 , The environment 34 includes in particular an air of a front room 3 moving in the direction of travel in front of the vehicle 2 and does not touch the vehicle, one immediately the vehicle 2 surrounding space 31 and an object 30 , The space 31 preferably adjoins the front room 3 on.

2 shows a schematic view of the driver assistance system 1 , The driver assistance system 1 has an oscillator 4 , the first radar wave 10 generates a first laser 5 , the first laser beam 6 generates a converter 7 and a phase locked loop 33 with a command and a phase of the first radar wave 10 as a controlled variable. The first laser beam 6 is using an optical switch 12 in a first partial beam 8th of the first laser beam 6 and a second sub-beam 11 of the first laser beam 6 divided up. The first partial beam 8th is preferably by means of an optical waveguide on a crystal 13 , which preferably contains indium antimonite directed. The crystal 13 is with the help of a half-open case 14 the converter 7 firmly aligned with the optical fiber. The converter 7 converts the first partial beam 8th in a second radar wave 9 around.

The second radar wave 9 is done with the help of at least one stripline 15 received and to an entrance 16 the phase locked loop 33 directed. The phase locked loop 33 includes a first frequency divider 17 , a phase comparator 18 , a loop filter 19 , the oscillator 4 and a second frequency divider 20 which is in a feedback loop between the oscillator 4 and the first frequency divider 17 located. The phase locked loop 33 regulates the phase of the first radar wave 10 such that the first radar wave has a fixed phase relationship with the phase of the second radar wave 9 Has. In particular, the phase-locked loop controls 33 a frequency of the first radar wave 10 ,

The first radar wave 10 will be at an exit 21 the phase locked loop 33 dissipated and in the direction of an antenna 22 directed. The antenna 22 emits the first radar wave 10 in the front room 3 from. At the same time, the second partial beam 11 to an optical output 23 of the driver assistance system 1 directed. The optical output 23 radiates the second partial beam 11 also and preferably simultaneously to a transmission of the first radar wave 10 in the front room 3 from. To both the first laser 5 as well as the phase locked loop 33 to control, in particular a first division ratio m for the first frequency divider 17 and a second dividing ratio n for the second frequency divider 20 pretend to be the first laser 5 and the phase locked loop 33 with an evaluation and control unit 24 of the driver assistance system 1 connected. About such a connection passes a respective information about when the second partial beam 11 and the first radar wave 10 were sent to the evaluation and control unit 24 ,

The driver assistance system 1 also has a first detector 25 for receiving the second sub-beam 11 , a second detector 26 for receiving the first radar wave 10 after this, just like the second sub-beam 11 on an object 30 was reflected, a first sensor 26 , a second sensor 27 , a third sensor 28 and a fourth sensor 29 on.

The evaluation and control unit 24 Controls and stores a first time in which the first radar wave 10 and the second sub-beam 11 simultaneously in the direction of the object 3 to be sent out. Afterwards, the evaluation and control unit will record 24 a second time in which the on the object 3 reflected first radar wave 10 with the second detector 26 is received, and a third time in which the on the object 3 reflected second partial beam with the first detector 25 Will be received. The first runtime is the time difference between the second and the first time and the second runtime is the time difference between the third and the first time.

Furthermore, the evaluation and control unit determines 24 with the aid of the above-mentioned calculation instructions and preferably with the aid of one with the first sensor 27 recorded carbon dioxide content of the air in the room 31 , one with the second sensor 28 detected a relative humidity of the air in the room 31 and one with the third sensor 29 detected pressure of the air in the room 31 a value of a state quantity in the front room 3 , The state quantity in this embodiment is a mean temperature in the front space 3 , The calculation instructions are preferably in the evaluation and control unit 24 stored or stored in a memory 35 in the form of a first model.

Furthermore, the control and evaluation unit 24 preferably has a second model 32 on, the at least one propagation property of the second sub-beam 11 and / or the first radar wave 10 taken into account as a function of the state variable. For a creation of the model 32 is preferably a plurality of records in the control and evaluation unit 24 stored and values of parameters of the model 32 adapted to the data records.

A single data set preferably comprises the first and the second runtime or the respective ones with the detectors 25 . 26 recorded values and at least a first material property of the object 30 at which the second partial beam 11 and the first radar wave 10 be reflected. Here, the second model 32 For example, be constructed such that the first material property of the object 30 an output value and the remaining above-mentioned values of the individual data set each have an input value of the second model 32 represent.

Within the model 32 may preferably be an intensity of a respective received signal of the first detector 25 or the second detector 26 depending on a respective current value of the first sensor 27 , the second sensor 28 and the third sensor 29 be approximated. The respective modeled intensity of the received signal can then be measured with a measured intensity of a respective received signal of the first detector 25 and the second detector 26 be compared. Based on such a comparison and with the help of one with the fourth sensor 36 measured value of the state variable, the first or a further material property of an object to be detected can be detected. The measured value of the state quantity in this embodiment is a temperature of the air in the room 31 ,

3 shows temporal phase curves φ of a phase over time t, in particular a temporal phase curve 41 the first radar wave 10 and a temporal phase course 42 one to the second partial beam 11 corresponding electromagnetic wave. Out 2 it can be seen that the electromagnetic wave and the first radar wave 10 have a fixed phase relation to each other.

Furthermore, one wavelength of the first radar wave 10 an integer multiple of a wavelength of the first sub-beam 8th and thus also the second partial beam 11 , The value m of the first division ratio becomes the control of the phase locked loop 33 changed, for example, reduced, so changed, for example, increases the wavelength of the first radar wave 10 , A temporal phase progression 43 such a changed first radar wave 10 with a lower wavelength is in 3 shown in dashed lines.

Also the changed first radar wave 10 each has a fixed phase relationship with respect to the second radar wave 9 and the second sub-beam 11 , A phase of the first radar wave 10 and also the changed first radar wave 10 always has a fixed factor with respect to a phase of the second radar wave 8th and a phase of the second sub-beam 11 , the first partial beam 8th and the first laser beam 6 on.

4 shows another driver assistance system 100 , The driver assistance system 100 indicates in addition to the components of the driver assistance system 1 a second laser 51 , a second optical output 52 , a second phase locked loop 53 and a second antenna 54 on. In this variant, the second partial beam 11 by a division of a fourth partial beam 64 generated. The fourth partial beam 64 is due to a division of the first laser beam 6 at the switch 12 won. A division of the fourth partial beam 64 in the second sub-beam 11 and a fifth sub-beam 55 done by another optical switch 56 , With the fifth partial beam 55 becomes the second laser 51 pumped. This causes one with the second laser 51 generated second laser beam 57 in phase synchronization with the first laser beam 6 and thus also to the second partial beam 11 is. The second laser beam 57 points opposite to the second partial beam 11 of the first laser beam 6 a different wavelength.

The second phase locked loop 53 works in the same way and has the same components as the first phase locked loop 33 , However, with the help of the control and evaluation unit 24 another first division ratio m and / or another second division ratio n for the second phase locked loop 53 specified. This generates the second phase-locked loop 53 a third radar wave 58 which also like the first radar wave 10 a fixed phase relationship with the first radar wave 9 having. Thereby, that the second phase locked loop 53 has other divider ratios for the frequency divider has the third radar wave 58 a different frequency compared to the first radar wave 10 , The third radar wave 58 becomes the second antenna 54 directed and from the second antenna 54 in the front room 3 radiated. Likewise, the second optical output directs 52 the second laser beam 57 in the front room 3 ,

With the help of the additional second laser beam 57 and the third radar wave 58 It is possible to determine further supporting points for the calculation rule of the state variable of the air and thereby the value of the state variable of the air as a function of the respective duration of the second partial beam 11 , the second laser beam 57 , the first radar wave 10 and the third radar wave 58 to determine. Both rays 11 . 57 are preferred simultaneously with both radar waves 10 . 58 sent out and a common time of sending out in the control and evaluation unit 24 saved. The second laser beam 57 is with a third detector 37 and the third radar wave 58 with a fourth detector 38 receive.

1 further shows a first wheel speed sensor 39 and a second wheel speed sensor 40 for calculating a coefficient of friction between a roadway 61 and a first wheel 62 and / or a second wheel 63 of the vehicle 2 using a coefficient of friction model, which is advantageous in the control and evaluation unit 24 is included. Using the calculated coefficient of friction, both the first model and the second model 32 Getting corrected.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• US 2014/0104051 A1 [0002]
• US 7742152 B2

Cited non-patent literature

• "The Refractive Index of Air," Metrologia 2 (1966), pages 71-80, by B. Edlen [1] and in the publication "The Refractivity of Air", Journal of Research of the National Bureau of Standards, Vol. 86 , No. 1, January-February 1981 [0012]

Claims (10)

Driver assistance system (1) for a vehicle (2) for detecting an environment (34) of the vehicle (2), the driver assistance system (1) comprising an oscillator (4) which generates a first radar shaft (10), a first laser (5) , which generates a first laser beam (6), a converter (7) and a phase locked loop (33) with a reference variable and a phase of the first radar wave (10) as a controlled variable, wherein the converter (7) comprises a first partial beam (8) of the first Laser beam (6) into a second radar wave (9) converts, a phase of the second radar wave (9) is the command variable and the driver assistance system (1) the first radar wave (10) and a second sub-beam (11) of the first laser beam (6) simultaneously emits, at least on the basis of a difference between a running time of the first radar wave (10) and a running time of the second partial beam (11) to determine at least one value of a state variable of an air of the environment (34). Driver assistance system (1) after Claim 1 , characterized in that the phase locked loop (33) has at least one first frequency divider (17) with which a frequency of the first radar wave (10) is adjustable. Driver assistance system (1) after Claim 1 or 2 , characterized in that the first laser (5) is a tunable laser (5). Driver assistance system (1) according to one of the preceding claims, characterized in that the driver assistance system (1) has a second laser (51) which is coupled to the first laser (5) such that the first laser (5) the second laser (51 ) can excite by means of the first laser beam (6), the first or second sub-beam (11), wherein the second laser (51) generates a second laser beam (57) having a wavelength which is different from a wavelength of the first laser beam (6) said second laser beam (57) has a fixed phase relationship with the first laser beam (6) and the driver assistance system (1) emits the second laser beam (57) simultaneously with the second sub-beam (11). Driver assistance system (1) according to any one of the preceding claims, characterized in that the driver assistance system (1) has a further oscillator for generating a third radar wave (58) and another phase locked loop (53) and the further phase locked loop (53) controls the further oscillator so in that the third radar shaft (58) has in each case a fixed phase relationship to the first radar wave (10) and the second sub-beam (11) and has a different frequency than the first radar wave (10), and the driver assistance system (1) the third radar wave ( 58), the first radar wave (10) and the second sub-beam (11) emits simultaneously. Method for detecting an environment (34) of a vehicle (2) with the following steps: Generating a first laser beam (6) in a first step, Generating a second radar wave (9) by means of a converter (7) and a first partial beam (8) of the first laser beam (6) in a second step, - Generating a first radar wave (10) by means of an oscillator (4) and controlling the oscillator (4) by means of a phase locked loop (33) having a phase of the first radar wave (10) as a controlled variable and a phase of the second radar wave (9) as a reference variable in a third step, Simultaneous emission of the first radar wave (10) and a second sub-beam (11) of the first laser beam (6) in a fourth step, Measuring a respective transit time of the first radar wave (10) and the second sub-beam (11) between the driver assistance system (1) and an object (30) on which the second partial beam (11) and the first radar wave (10) are reflected a fifth step, - Determining a value of a state variable of the air of the environment (34) based on the transit times in a sixth step. Method according to Claim 6 , characterized in that the steps one to six are performed several times and at least based on the respective measured maturities a model is generated, which takes into account at least one propagation behavior of the second partial beam (11) and / or the first radar wave (10) in dependence of the state variable , Method according to Claim 7 , characterized in that when generating the model, a measured value of the state variable is included, wherein the measured value is measured at a time in which the vehicle (2) is in an air volume in which previously the second partial beam (11 ) and the first radar shaft (10) have spread. Method according to Claim 7 or 8th , characterized in that when generating the model at least a first material property of the object (30) is known and using the model, the measured transit times and at least one measured value of the state variable, the first or another material property of an object to be detected is detected. Method according to one of Claims 6 to 9 , characterized in that at least based on the value of the state variable, a first state of a roadway (61) on which the Vehicle (2) is determined, at least by means of a wheel speed sensor (39, 40) of a wheel of the vehicle (2) and a friction coefficient model for determining a coefficient of friction between the wheel and the roadway (61) determines a second state of the road (61) is performed, a comparison between the first state of the roadway (61) and the second state of the roadway (61) is performed and based on a result of the comparison, the model is corrected.

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