DE102009009227B4 - Method for the automatic alignment of a radiation sensor in a vehicle - Google Patents

Abstract

A method for automatically aligning a beam sensor in a motor vehicle, the beam sensor comprising: transmission means for radiation of transmission power directed in azimuth and elevation, reception means for reception of transmission power reflected on objects in azimuth and elevation, signal processing means for processing the received power Control unit for automatically aligning a beam in the elevation direction, controllable means for pivoting an elevation beam direction in a continuous or discrete manner in a predetermined area, the means for pivoting being connected to the control unit so that the beam in the elevation direction is automatically transferred to one of the control unit a predetermined elevation direction is characterized in that the elevation beam direction varies and the intensity of the reflex varies in order to determine an elevation misalignment and / or a correct elevation alignment ions of moving and stationary objects is evaluated, the correct elevation alignment being determined in such a way that the intensity of the reflections from stationary and / or moving objects is strongest there.

Description

The invention relates to a beam sensor system for use in driver assistance systems in motor vehicles, which is adjustable in particular in the elevation direction.

Motor vehicles are increasingly being equipped with driver assistance systems which, with the aid of sensor systems, detect the surroundings and derive automatic reactions of the vehicle from the traffic situation recognized in this way and / or instruct, in particular warn, the driver. A distinction is made between comfort and safety functions.

In the area of comfort functions, FSRA (Full Speed Range Adaptive Cruise Control) currently plays the most important role. The vehicle regulates its own speed to the desired speed specified by the driver, provided the traffic situation permits, otherwise the own speed is automatically adjusted to the traffic situation.

The focus of the safety functions is on reducing the braking distance in emergency situations. The spectrum of the corresponding driver assistance functions ranges from automatic pre-filling of the brake to reduce braking latency (prefill), through an improved brake assistant (BAS +) to autonomous emergency braking.

Radar sensors are predominantly used today for driver assistance systems of the type described above. These work reliably even in poor weather conditions and, in addition to the distance between objects, can also directly measure their relative speed using the Doppler effect.

Since the driver assistance functions described above also require the correct detection of more distant objects (with FSRA a range of up to 200m is required), precise sensor alignment is necessary - in the elevation direction, the typical requirements are a maximum deviation of ± 0.5 ° compared to parallel alignment to the road, in azimuth direction with a maximum deviation of ± 0.3 ° from the straight ahead direction of the vehicle.

If the sensor is misaligned in elevation by more than the above value, z. B. the danger that he looks over moving objects at a great distance or interprets bridges as the end of a traffic jam; The former leads to late reactions in the case of FSRA, the latter can lead to incorrect braking in autonomous braking systems and thus to safety-critical situations up to and including an accident.

The sensors available today can only be aligned using manually adjustable fastenings or holders. The high-precision adjustment of the sensors is a major problem in production and especially in workshops (e.g. when replacing a sensor) - unacceptable errors often occur.

the EP 1 217 686 A2 discloses an automatically adjustable sensor system in which the beam direction can be adjusted by means of an automatically pivotable plate. However, a method for automatic self-adjustment is not specified.

From the US 6,459,476 B2 a laser radar for a vehicle is known, the laser beam being aligned on the basis of the radiation angle and the angular position of the laser radar.

the U.S. 6,157,294 A describes a vehicle control system with a first laser radar for detecting an obstacle and with a second and third laser radar that measure distances between the first laser radar and the road surface at different angles. The system can then determine whether the laser beam is horizontal and correct the inclination of the laser radar if necessary.

the DE 195 36 000 A1 discloses a level setting for distance measuring systems by means of a pulse sensor in vehicles, with a measure of the necessary alignment being obtained by evaluating the distance measured in front of the vehicle and / or the pulse shape of the sensor signal.

From the DE 102 07 437 A1 a radar sensor with a transmitting and receiving device is known, the directional characteristic of which has a plurality of lobes, at least one of which is directed parallel to the road surface, with at least one other lobe being directed obliquely onto the road surface.

Furthermore, the EP 1 217 686 A2 an adjustable radar sensor for detecting the surroundings of a vehicle with an electric drive, the sensor being able to recognize its misalignment from the data obtained. This happens, for example, due to the reflections on the road surface or due to detected, stationary objects in the sensor field of view. The aim of the adjustment is to adjust the sensor parallel to the vehicle's longitudinal axis.

It is therefore the object of the present invention to specify a method for the automatic adjustment of a beam sensor for a motor vehicle, which automatically during the Carries out a sensor adjustment during vehicle operation and / or in a workshop without a person having to initiate or monitor the self-adjustment.

This object is achieved by a method according to the independent claims.

• 1.: a) Querschnitt der beispielhaften Gesamt-Antennenanordnung, b) Wellenleiter (in vereinfachter Darstellung) und Trommel von der Seite.
• 2: beispielhaftes Design der Oberflächenstrukturierung der Trommel
• 3: Sensorjustage mit Hilfe von Metallplatte
• 4: Sensorjustage über Straßenreflexionen

The invention is explained in more detail below with reference to figures and exemplary embodiments. The invention is explained by way of example for a radar sensor system, but the claimed method can be generalized to a lid sensor system with means for pivoting the beam in the elevation beam direction, for example a mirror, metal plate, prism, etc., without any restriction.

• 1 .: a) Cross section of the exemplary overall antenna arrangement, b) waveguide (in a simplified representation) and drum from the side.
• 2 : exemplary design of the surface structure of the drum
• 3 : Sensor adjustment using a metal plate
• 4th : Sensor adjustment via street reflections

In 1a) a cross-section of the exemplary overall antenna assembly is shown; 1b) shows the waveguide components 11 (in simplified representation) and drum 12th of the page. At one end of the waveguide 11 power in the high frequency range is fed in, which propagates along it in the form of an electromagnetic wave. There is a drum in the immediate vicinity of the waveguide 12th , which has a structured metallic surface. The surface structuring of the drum intervenes in the electromagnetic fields around the waveguide and decouples power from the arrangement, which is radiated into the room in the form of a radiation lobe. The direction Θ of the maximum intensity of the radiation lobe results, for example, with a periodic arrangement of structures on the drum by the relationship sinΘ = λ ₀ / λ _g - = λ ₀ / p, where λ _{0 is} the free space wavelength, λ _{g is} the wavelength on the waveguide and p mean the distance between the surface structures on the drum.

The radiation lobe coupled out and directed from the waveguide hits a subreflector working as a polarizer 13th made of a dielectric material with an applied metallic grid 14th or metallic strips. The power is completely reflected on it and onto a main reflector called a twist reflector 15th thrown, which is advantageously designed as a reflect array. Due to a location-dependent reflection behavior, this forms or bundles the radiation lobe additionally in planes parallel to the plane running through the z-axis, which is inclined by the angle Θ with respect to the y-axis, and at the same time causes a polarization rotation of the radiation lobe by 90 °, see above that the power can then pass through the polarizer unhindered.

The antenna arrangement is used not only for the transmission of power, but also for the reception of transmission power reflected from objects - due to the reciprocity theorem, the arrangement works in the reception case in an analogous way as in the transmission case.

In relation to the installation of the sensor in the vehicle, the y-direction represents the direction of travel, the z-direction the vertical. In relation to the overall sensor, the beam bundling and direction in azimuth results from the structure of the drum, which causes power to be decoupled from the waveguide, and the beam bundling and direction in elevation from the design of the reflect array, which contains the power incident there reflected accordingly.

In order to change the azimuth beam characteristic over time, a temporal variation of the surface structure of the drum is necessary. This is achieved in that the drum rotates around its longitudinal axis at a constant speed of rotation and its surface structure changes over the circumferential angle. In 2 an exemplary design of the surface structure of the drum is given.

In order to change the elevation beam direction of the sensor, the main reflector can, for example, be controlled by a stepper motor 19th with a pestle 18th around the fulcrum 17th be pivoted by a range of ± 5-10 °, which corresponds to a variation of the elevation beam direction by ± 10 ° -20 °; an adjustment over the entire elevation range of z. B. 32 ° takes about 0.5s.

1. a) Sensorjustage mit Hilfe von ebener Metallplatte (siehe 3):
   • Zur Justage des Sensors wird das Fahrzeug auf eine waagrechte Fläche gestellt. Vor dem Fahrzeug steht senkrecht in z.B. Im Abstand eine ebene Metallplatte. Der Sensor strahlt auf die Metallplatte, verändert dabei seine Elevationsstrahlrichtung, misst jeweils die von der Metallplatte reflektierte Leistung und stellt anschließend diejenige Elevationsstrahlrichtung ein, bei welcher die Reflexionen an der Metallplatte maximale Intensität haben. Dadurch ist der Sensor in Elevation so justiert, dass er parallel zur Straße schaut.
   • Es sei erwähnt, dass die Metallplatte auch zur Justage in Azimut benutzt werden kann; dazu muss sie senkrecht zur Geradeausrichtung des Fahrzeugs positioniert sein.
2. b) Sensorjustage durch Fahrt mit Hilfe von Reflexionen der Straßenoberfläche (siehe 4): Insbesondere Werkstätten haben den Wunsch, dass sich der Sensor bei einer wenige Minuten dauernden Fahrt selber justiert (denn dazu sind zum einen keine speziellen Zusatzmittel wie eine Metallplatte nötig, und zum anderen können dem Automechaniker keine Fehler durch falsche Ausführung der Justageprozedur passieren). Während einer solchen Justagefahrt schaut der Sensor z.B. im ersten Schritt unter zwei unterschiedlichen Elevationswinkeln schräg auf die Straße und bestimmt dabei jeweils die Entfernung der empfangenen Straßenreflexionen. Damit liegen dann zwei einfache trigonometrische Beziehungen mit den zwei Unbekannten - der Fehljustagewinkel in Elevation sowie die Einbauhöhe des Sensors - vor, woraus der Elevationsfehljustagewinkel in einfacher Rechnung bestimmt werden kann (ist die Sensoreinbauhöhe bekannt, dann reicht die Messung unter einem Winkel). Im zweiten Schritt wird der Sensor unter einem Elevationswinkel von x°, mit x=7-10° und insbesondere x=7°, gegen die Straße geneigt und bestimmt dabei die Relativgeschwindigkeiten der Straßenreflexionen bei unterschiedlichen Winkeln seiner Azimutstrahlrichtung aus. Da diese Relativgeschwindigkeiten proportional zum Kosinus der Azimutstrahlrichtung bezogen auf die Geradesausrichtung des Fahrzeugs sind, kann daraus der Azimutfehljustagewinkel errechnet werden (Azimutfehljustagewinkel ist Differenz zwischen Geradeausrichtung von Fahrzeug und Sensorrichtung).
3. c) Ausrichtung des Sensors in Elevation während der Fahrt mit Hilfe von Reflexionen an stehenden und bewegten Objekten:
   • Zur Elevationsjustage nach Einbau des Sensors oder zur Kontrolle der Elevationsausrichtung während der Fahrt können statt der Reflexionen der Straßenoberfläche auch die Reflexionen an stehenden und bewegten Objekten benutzt werden.
   • Dazu wird die Elevationsstrahlrichtung um ±x° gegenüber derjenigen Richtung durchgestimmt, welche als parallel zur Straße angenommen wird; dieses Durchstimmen wird mehrfach wiederholt und erfolgt insbesondere sehr schnell. Zu den unterschiedlichen Elevationsstrahlrichtungen werden die mittleren Intensitäten der Reflexionen von stehenden und bewegten Objekten ermittelt. Ergibt sich die höchste Intensität bei derjenigen Richtung, welche als parallel zur Straße angenommen wird, hat sich diese Annahme bestätigt. Andernfalls muss die Elevationsausrichtung entsprechend angepasst werden, was je nach Durchstimmweite x in einem Schritt oder iterativ vorgenommen werden kann. Zur initialen Sensorjustage kann die Durchstimmweite x groß gewählt werden (z. B. 10°), da die Fahrerassistenzfunktion dabei ohnehin nicht aktiv sind. Für die Kontrolle der Elevationsausrichtung während der Fahrt ist x aber deutlich geringer zu wählen (z. B. 1°), da dadurch die dann aktiven Fahrerassistenzfunktionen nicht gestört werden dürfen.
   • Mit diesem Verfahren kann auch eine Elevationsfehlausrichtung bedingt durch Beladung des Fahrzeugs erkannt und korrigiert werden.
   • In einer besonderen Ausgestaltung der Erfindung wird die Elevationsstrahlrichtung zur Kontrolle der Justage, insbesondere während des Normalbetriebs des Strahlsensors gegenüber der aktuellen Sollrichtung variiert, wobei der Variationsbereich kleiner als die Elevationskeulenbreite ist und das Variieren sehr schnell (höchstens wenige Sekunden dauernd) erfolgt und vielfach wiederholt wird.
   • In einer vorteilhaften Ausgestaltung wird zu den unterschiedlichen Elevationsstrahlrichtungen des Variationsbereichs aus den Intensitäten der Reflexionen von stehenden und bzw. oder bewegten Objekten ein Reflexionsmaß, z.B. die mittlere Reflexionsstärke, ermittelt und daraus diejenige Elevationsstrahlrichtung mit maximalem Reflexionsmaß bestimmt. In einer besonderen Ausgestaltung wird in dem Fall, dass die Elevationsstrahlrichtung mit maximalem Reflexionsmaß der aktuellen Sollrichtung zumindest näherungsweise entspricht, die Sollrichtung unverändert beibehalten, und andernfalls die Sollrichtung verändert.
4. d) Korrektur von dynamischen Nickwinkeländerungen
5. e) Änderung der Elevationsstrahlrichtung in speziellen Fahrsituation gegenüber einer zur Straße parallelen Ausrichtung:
   • Z.B. kann bei sehr geringer Einbauhöhe des Sensors dieser für kleine Geschwindigkeiten oder im Stillstand schräg nach oben ausgerichtet werden, um die Wahrscheinlichkeit zu reduzieren, dass er unter einem vorausliegenden Fahrzeug durchschaut und dieses deshalb übersieht.
   • Umgekehrt kann der Sensor bei großer Einbauhöhe in solchen Situation schräg nach unten gerichtet werden.

This change in the elevation beam direction is used for different purposes:

1. a) Sensor adjustment using a flat metal plate (see 3 ):
   • To adjust the sensor, the vehicle is placed on a horizontal surface. In front of the vehicle, a flat metal plate stands vertically at a distance, for example. The sensor radiates onto the metal plate, changing its elevation beam direction, measures the power reflected by the metal plate and then sets the elevation beam direction in which the reflections on the metal plate have maximum intensity. This is the sensor adjusted in elevation so that it looks parallel to the road.
   • It should be mentioned that the metal plate can also be used for adjustment in azimuth; to do this, it must be positioned perpendicular to the straight ahead direction of the vehicle.
2. b) Sensor adjustment by driving with the help of reflections from the road surface (see 4th ): Workshops in particular want the sensor to adjust itself when driving for a few minutes (because, on the one hand, no special additives such as a metal plate are required, and on the other hand, the auto mechanic cannot make mistakes by incorrectly executing the adjustment procedure). During such an adjustment run, for example, in the first step the sensor looks obliquely at the road at two different elevation angles and determines the distance of the received road reflections in each case. There are then two simple trigonometric relationships with the two unknowns - the misalignment angle in elevation and the installation height of the sensor - from which the elevation misalignment angle can be determined in a simple calculation (if the sensor installation height is known, the measurement at one angle is sufficient). In the second step, the sensor is inclined towards the road at an elevation angle of x °, with x = 7-10 ° and in particular x = 7 °, and determines the relative speeds of the road reflections at different angles of its azimuth beam direction. Since these relative speeds are proportional to the cosine of the azimuth beam direction based on the straight alignment of the vehicle, the azimuth misalignment angle can be calculated from them (azimuth misalignment angle is the difference between the straight alignment of the vehicle and the sensor direction).
3. c) Alignment of the sensor in elevation while driving with the help of reflections on stationary and moving objects:
   • For elevation adjustment after installing the sensor or for checking the elevation alignment while driving, the reflections on stationary and moving objects can also be used instead of the reflections from the road surface.
   • For this purpose, the elevation beam direction is tuned by ± x ° compared to that direction which is assumed to be parallel to the road; this tuning is repeated several times and in particular takes place very quickly. The mean intensities of the reflections from stationary and moving objects are determined for the different elevation beam directions. If the highest intensity is found in the direction that is assumed to be parallel to the road, this assumption has been confirmed. Otherwise, the elevation alignment must be adjusted accordingly, which can be done in one step or iteratively, depending on the tuning range x. For the initial sensor adjustment, the tuning range x can be selected to be large (e.g. 10 °), since the driver assistance functions are not active anyway. For checking the elevation alignment while driving, however, x should be selected to be significantly lower (e.g. 1 °), since this must not interfere with the driver assistance functions that are then active.
   • This method can also be used to detect and correct elevation misalignment caused by the vehicle being loaded.
   • In a special embodiment of the invention, the elevation beam direction is varied to control the adjustment, in particular during normal operation of the beam sensor compared to the current setpoint direction, the range of variation being smaller than the elevation lobe width and the variation taking place very quickly (lasting at most a few seconds) and being repeated many times .
   • In an advantageous embodiment, a reflection measure, for example the mean reflection strength, is determined for the different elevation beam directions of the variation range from the intensities of the reflections from standing and / or moving objects, and from this the elevation beam direction with the maximum reflection measure is determined. In a particular embodiment, in the event that the elevation beam direction with the maximum reflectance corresponds at least approximately to the current target direction, the target direction is retained unchanged, and otherwise the target direction is changed.
4. d) Correction of dynamic changes in the pitch angle
5. e) Change of the elevation beam direction in special driving situations compared to an alignment parallel to the road:
   • For example, if the installation height of the sensor is very low, it can be aligned obliquely upwards for low speeds or when stationary in order to reduce the probability that it will see through under a vehicle lying ahead and therefore overlook it.
   • Conversely, if the installation height is great, the sensor can be pointed downwards at an angle in such a situation.

Claims (9)

Method for an automatic alignment of a beam sensor in a motor vehicle, the beam sensor comprising: transmission means for radiation of transmission power directed in azimuth and elevation, reception means for reception of transmission power reflected on objects in azimuth and elevation, signal processing means for processing the received power Control unit for automatically aligning a beam in the elevation direction, controllable means for pivoting an elevation beam direction in a continuous or discrete manner in a predetermined area, the means for pivoting being connected to the control unit so that the beam in the elevation direction is automatically transferred to one of the control unit Aligned predetermined elevation direction is characterized in that to determine an elevation misalignment and / or a correct elevation alignment, the elevation beam direction varies and the intensity of the Reflections from moving and stationary objects is evaluated, the correct elevation alignment being determined in such a way that the intensity of the reflections from stationary and / or moving objects is strongest there. Procedure according to Claim 1 , in which a radar sensor system is provided as a beam sensor and objects are evaluated whose distance from the radar sensor system is greater than a threshold value S. Method according to one of the Claims 1 or 2 , wherein the elevation beam direction for checking the adjustment is varied during normal operation of the beam sensor with respect to the current target direction and the range of variation is smaller than that of an elevation lobe width. Procedure according to Claim 3 wherein the variation takes place at most within a few seconds, in particular in a time interval between 2 and 10 seconds, and is repeated several times. Method according to one of the Claims 1 until 4th , whereby a reflection measure, for example an average reflection strength, is determined for the different elevation beam directions of the variation area from the intensities of the reflections from standing and / or moving objects, and that elevation beam direction with the maximum reflection measure is determined. Procedure according to Claim 5 , wherein in the case that the elevation beam direction with maximum reflectance corresponds at least approximately to a current target direction, the target direction remains unchanged, and otherwise the target direction is changed. Method according to one of the Claims 1 until 6th , in which the motor vehicle is at a standstill in order to determine an elevation misalignment and / or the correct elevation alignment, and only a predetermined stationary object is used. Procedure according to Claim 7 , in which a flat metallic mirror or a corner reflector is used as a defined stationary object. Automatically alignable beam sensor for a motor vehicle comprising: - Sending means for radiation of transmission power directed in azimuth and elevation, - Receiving means for receiving transmission power reflected on objects in azimuth and elevation, - Signal processing means for processing the received power - controllable means for pivoting the elevation beam direction in continuously or discreetly in a predetermined area, the means for pivoting being connected to the control unit so that the beam in the elevation direction is automatically aligned in an elevation direction predetermined by the control unit and a control unit for automatically aligning the beam in the elevation direction according to a method the Claims 1 - 8th .

Images