DE102006060892B4 - Method and device for lane keeping assistance for a vehicle - Google Patents

Abstract

Method for lane keeping assistance for a vehicle with a sensor system and a data processing unit, wherein◯ the sensor system detects a predetermined area in front of the vehicle,◯ a reference value for the reflection strength and/or a characteristic shape of the sensor signal caused by this lane marking is stored for at least one type of lane marking, and◯ the current lane is estimated from sensor data recorded from lane markings ahead,◯ the current lane width is estimated from the sensor data of the lane markings currently ahead, it being assumed that the width of the lane ahead corresponds to the current width.

Description

The invention relates to a method and a device for lane keeping support for a vehicle. The method and the device are particularly suitable for motor vehicles that are equipped with an adaptive speed control based on an infrared sensor system.

Methods and devices for lane keeping support are known as state of the art. For example, the patent specification DE 195 07 957 C1 a vehicle with an optical scanning device for a side lane area. The scanning device comprises several infrared transmitting elements and an associated CCD array. The detection area of the scanning device is aligned with potential lane markings to the left and right of the vehicle. The distance and contour of the detected objects are determined. Depending on other parameters, a warning signal is also issued if the vehicle leaves the lane.

The JP 2005 - 332 104 A discloses a lane line detection device capable of detecting a lane line by image synthesis of photographed images. The images are recorded by an imaging device, such as a camera for imaging an area of the road surface. Furthermore, WO 2004 / 021 546 A2 An assistance function with a 3D distance image camera for a means of transport is known, which, in addition to grayscale or color image data, also provides distance data for the detection of objects in the vicinity of the means of transport.

The object of the invention is to present a simple and cost-effective method and a device for lane keeping assistance for a vehicle.

This object is achieved according to the invention by a method and a device according to the independent patent claims. Advantageous further developments can be found in the subclaims.

A method according to the invention for lane keeping support for a vehicle with a sensor system and data processing unit is specified. The sensor system is sensitive to lane markings and detects objects in a predetermined area in the direction of travel in front of the vehicle. The sensor system is preferably arranged in a motor vehicle behind the windshield or near the headlights or in the radiator grille. A reference value for the reflection strength and/or a characteristic form of the sensor signal caused by this lane marking is stored for at least one type of lane marking. The current lane is estimated from sensor data recorded from lane markings ahead.

In an advantageous embodiment of the invention, the sensor system is designed such that it has at least one infrared transmitter and receiver. The distance of objects, in particular lane markings, in front of the vehicle is determined by a suitable measuring method, e.g. pulse transit time measurement.

In a further embodiment of the invention, the sensor system is designed as a camera system that includes at least one image sensor. The distance of objects, in particular of lane markings, is determined directly from the image data, for example in the case of a stereo camera. In the case of a mono camera, the distance of objects is estimated using geometric considerations.

In a preferred embodiment of the invention, the current lane width is estimated from the sensor data of the lane markings currently ahead, whereby it is assumed that the width of the lane ahead matches the current width. The width of the lane ahead is determined, for example, from the distance between the lane markings and the predetermined detection range, in particular the opening angle, of the sensor system.

In an advantageous embodiment of the invention, the current position of the vehicle with sensor system in the lane, i.e. whether the vehicle is in the middle of the lane or rather on the left or right edge, is estimated from the sensor data regarding the lane markings ahead and the predetermined detection range of the sensor system. The detection range of the sensor system is designed, for example, symmetrically to the vehicle's longitudinal axis. If the vehicle is in the middle of the lane, the lane markings to the left and right in front of the vehicle are essentially the same distance away. This consideration can easily be transferred by a specialist to predetermined detection ranges that are not designed symmetrically to the vehicle's longitudinal axis.

In a further embodiment of the invention, the width of the lane ahead is determined. In addition, the vehicle's own movement is recorded. Once the vehicle has arrived at the said location ahead, the previously determined lane width is adopted as the current lane width.

In an advantageous embodiment of the method according to one of the preceding claims, a lane is determined based on the lane markings ahead. For this purpose, a trajectory is calculated which describes the vehicle's own motion as it continues to move in the lane. The calculated trajectory is compared with the vehicle's actual own motion. The current position of the vehicle in the lane is determined from the comparison. If the own motion and trajectory match, it is assumed that the position of the vehicle in the lane is in the middle. Corresponding conclusions are drawn if the own motion is more to the left or right than the trajectory provides.

In a preferred embodiment of the invention, a detection threshold is provided. The detection threshold serves to separate desired signals from objects from undesired signals, e.g. noise, interference signals or signals from irrelevant objects. The detection threshold of the sensor system is set so that road markings are detected with a high probability. It should be noted that the intensity of the signal reflected from a road marking depends on the distance. In a pulse transit time measurement, for example, a detection threshold that decreases with the transit time can be used, since the signal strength of objects further away is smaller than that of objects that are very close to the sensor system.

The inventive method for lane keeping assistance is stored, for example, in a motor vehicle with a sensor system and a data processing unit.

In a preferred embodiment of the motor vehicle with sensor system, lane keeping assistance and adaptive control of the longitudinal speed, e.g. ACC, are based on the data from one sensor system.

• 1: Bestimmung des Objektabstands mit einem monokularen Kamerasystem
• 2: Schematische Darstellung eines Fahrzeugs mit Sensorsystem auf einer Fahrspur
• 3: Winkelabhängiges Empfindlichkeitsprofil eines Sensorsystems mit sieben Kanälen
• 4: Kraftfahrzeug mit Sensorsystem in einer typischen Umgebung

The invention is explained in more detail below using embodiments and two figures.

• 1 : Determination of the object distance with a monocular camera system
• 2 : Schematic representation of a vehicle with sensor system on a lane
• 3 : Angle-dependent sensitivity profile of a sensor system with seven channels
• 4 : Motor vehicle with sensor system in a typical environment

All features described here can contribute to the invention individually or in any combination. The sequence of the process steps is not necessarily predetermined by the order chosen here.

bestimmt. Sind also die vorgenannten Parameter durch eine Justage der Blickrichtung der Kamera bekannt, kann die Entfernung d bestimmt werden. Fahrspurmarkierungen werden z.B. anhand ihrer Form, z.B. unterbrochene oder durchgezogene Linie auf der Fahrbahn, im Kamerabild erkennbar. Mit Kenntnis der Abbildungseigenschaften des Kamerasystems und der obigen Gleichung, wird der Abstand von zwei Fahrspurmarkierungen, die beabstandet in einer Bildzeile y abgebildet werden, berechnet. Der Abstand der Fahrspurmarkierungen gibt die Fahrspurbreite an.In one embodiment, the sensor system is designed as a mono camera system. In 1 A method for determining the distance of a point or object d using a mono camera is shown. The distance to the mono camera is calculated from h the camera installation height, α the camera pitch angle, y the image line of the point, η the pixel size and f the camera focal length. $$d=h\cdot \frac{1-t\cdot \text{tan}\alpha }{t+\text{tan}\alpha }\text{with}t=y\cdot \frac{\eta }{f}$$

determined. If the above parameters are known by adjusting the camera's viewing direction, the distance d can be determined. Lane markings can be recognized in the camera image based on their shape, e.g. broken or solid lines on the road. With knowledge of the imaging properties of the camera system and the above equation, the distance between two lane markings, which are shown at a distance in an image line y, is calculated. The distance between the lane markings indicates the lane width.

For example, an edge detection method and/or a pattern recognition method is used to detect a lane marking. Lane markings are usually arranged in a periodically recurring manner; this property can also be used for detection, e.g. through a frequency analysis of the time-dependent signal.

In one embodiment, the sensor system is designed as an infrared sensor system. The sensor system has a first transmitter-receiver pair that monitors the right half of the total detection area, and a second transmitter-receiver pair that similarly monitors the left half of the total detection area. The distance between objects is determined by pulse transit time measurement. Lane markings that are designed as a broken or solid line on the road are recognized by the signal shape. The reflected signal typically has an extended pulse shape and can thus be distinguished from other objects, e.g. vehicles, which produce a reflected signal with a narrow shape. The same applies to a lane marking of any other shape, which also has a characteristic pulse shape of the reflected signal and can thus be distinguished from other objects. In many countries, for example, lane markings are arranged periodically. net, this property can also be used for detection, e.g. through a frequency analysis of the time-dependent signal.

The reflectivity of the lane markings also remains essentially the same, unless the lane markings are heavily soiled. This means that the amplitude of the reflection signal of lane markings, scaled at 1/x ^4, is also essentially the same. This criterion can also be used to reliably detect lane markings, for example, so that only objects with a specified distance-scaled amplitude are recognized as lane markings.

In 2 a vehicle 1 with an infrared sensor system is shown. Four separate detection areas 6 ad are provided, which are arranged symmetrically to the longitudinal axis of the vehicle 1 and whose opening angle is predetermined with respect to the vehicle's longitudinal axis. Area 6a detects the angle range -b...-a, area 6b detects -a...0, 6c detects 0 ... a and 6d detects a...b. In addition, lane markings 5 are shown. The lane width 2 is determined, for example, as follows: in area 6a, lane markings with associated distance values are detected. Due to the predetermined opening angle -b...-a, the smallest distance is assigned to the angle -b and the largest distance to the angle -a. The same process is carried out in the detection area 6d. Here, too, a distance value is assigned to the angles a and b. In an advantageous embodiment, the distance values of the lane markings 5 are recorded over a predetermined period of time in order, for example, to determine the smallest and/or the largest distance value with greater accuracy. If the distance values for the angles a and -a or b and -b are the same, vehicle 1 is in the middle of the lane. The lane width 2 can be calculated from the distance of the lane marking at a known first angle (here -a or -b) and the distance of the lane marking at a known second angle (here a or b), since for any triangle three pieces of information (sides S or angle W) are sufficient to calculate the three missing pieces of information.

In one embodiment, the sensor system 3 is designed as an infrared sensor system that determines the distance and position of objects. For this purpose, any combination of several transmitters with overlapping transmission ranges and/or receivers with overlapping reception ranges is provided. For example, in 3 an angle-dependent curve of the sensitivity of a sensor system with seven measuring channels is shown. The sensitivity of the individual channels is shown by the seven curves. To determine the position of an object, the signal from two overlapping measuring channels is compared. The position angle of the object is determined from the ratio of the signal strength in a first measuring channel to the signal strength of the same object in a second adjacent measuring channel. The lane width is calculated based on geometric considerations as described above.

In 4 Motor vehicle 1 with sensor system is shown in a typical environment. The vehicle 1 is moving on a two-lane road. Each of the two lanes is bordered by road markings 5. The motor vehicle 1 comprises a sensor system 3. The detection range of the sensor system 3 is shown by the dotted lines in 4 The sensor system 3 is attached to the front of the vehicle 1. The vehicle 1 moves in the middle of the lane. Line 4 indicates the movement of the vehicle 1. The width of the lane ahead is determined, e.g. for the position where the vehicle 1' is located. The movement of the vehicle is recorded, e.g. with a yaw rate and steering angle sensor. At a later point in time, when the vehicle 1 is at the location of the vehicle 1', the previously determined lane width is adopted as the current lane width.

Claims (9)

Method for lane keeping support for a vehicle with a sensor system and a data processing unit, wherein ◯ the sensor system detects a predetermined area in front of the vehicle, ◯ a reference value for the reflection strength and/or a characteristic shape of the sensor signal caused by this lane marking is stored for at least one type of lane marking, and ◯ the current lane is estimated from sensor data recorded from lane markings ahead, ◯ the current lane width is estimated from the sensor data of the lane markings currently ahead, it being assumed that the width of the lane ahead matches the current width. procedure according to claim 1 , wherein the sensor system has at least one infrared transmitter and receiver and the distance of objects, in particular lane markings, in front of the vehicle is determined. procedure according to claim 1 , wherein the sensor system is a camera system and the distance of objects, in particular lane markings, in front of the vehicle is determined from the image data. Method according to one of the preceding claims, wherein the current position of the vehicle with lane keeping assistance on the lane (center, left edge, right edge) is estimated from the sensor data of lane markings ahead and the predetermined detection range of the sensor system. Method according to one of the preceding claims, ◯ wherein a movement of the vehicle is recorded with a sensor system, ◯ the width of the lane ahead is determined, and ◯ this width is adopted as the current lane width at a later point in time, which depends on the vehicle's own movement. Method according to one of the preceding claims, wherein a trajectory is calculated on the basis of the lane ahead, which trajectory describes a movement of the vehicle with sensor system when it continues to move in the lane, and the calculated trajectory is compared with an actual movement of the vehicle in order to determine the current position of the vehicle in the lane. Method according to one of the preceding claims, wherein a detection threshold is specified such that road markings are detected with a high probability. Motor vehicle with a sensor system and a data processing unit on which a method for lane keeping assistance according to one of the preceding claims is stored. Motor vehicle after claim 8 , whereby the data from the sensor system is used for lane keeping assistance and for adaptive control of the vehicle's longitudinal speed.

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