WO2019073024A1

WO2019073024A1 - Lane sensing method

Info

Publication number: WO2019073024A1
Application number: PCT/EP2018/077841
Authority: WO
Inventors: Richard Moore; Manuel Nogueira; Ana ROBLEDA; Lucia TEIJEIRO
Original assignee: Connaught Electronics Ltd.
Priority date: 2017-10-13
Filing date: 2018-10-12
Publication date: 2019-04-18
Also published as: DE102017123842A1

Abstract

The present invention refers to a Method of providing a reliability value for defining the reliability of information provided by a lane sensing process for a vehicle (24), wherein the method comprises the steps of: a) providing information with regard to a position of lane markers (26, 28) relative to the vehicle (24); and b) defining the reliability of the information provided in step a), characterized in that step b) is based on at least one of i) the maximum distance of the outer detected lane marker candidates of a common lane boundary (30, 32); ii) the accumulated length of all detected lane marker candidates; iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers (26, 28); and iv) a probability according to which a lane marker candidate is a lane marker (26, 28).

Description

Lane sensing method

The present invention refers to a lane sensing method. The present invention particularly refers to a lane sensing method for a vehicle which gives an evaluation for the reliability of the sensed lane markers. The present invention further relates to a driver assistance system being adapted for executing such a lane sensing method and to a vehicle comprising such a driver assistance system.

Lane sensing systems and lane sensing methods are widely known in the art. Generally, such systems and such methods determine lane candidates in order to evaluate the predetermined route on a street. Such systems are thus helpful for driver assistance systems which may give information to a driver or which may provide autonomous driving.

US 7,295,682 B2, for example, relates to a driving lane recognition system which can improve the lane recognition accuracy by stably detecting the various kinds of lane markers is disclosed. An image processing means for image-processing a road image taken by a camera has a plurality of different kinds of image processing algorithms. A driving lane is detected by selecting an image processing algorithm suitable for the driving lane out of the plurality of different kinds of image processing algorithms corresponding to a road on which a vehicle is running. Further, the system is adapted for calculating a confidence of the lane recognition.

US 2005/0004753 A1 discloses a method for representing road lanes as data in a database that can be used by a system in a vehicle to provide a safety-related function. Each data representation of a physical road lane includes data indicating start and end points of the represented lane and other data attributes pertaining to the represented lane, including data indicating what physical features are adjacent to the represented lane on right and left sides thereof and data indicating a geometry of the represented lane. Further, at least some of the data representations of lanes are associated with data representations of sublanes. Each data representation of a sublane includes data indicating start and end points thereof, defined relative to the lane of which the sublane is a part. A data representation of a sublane includes at least one data attribute associated therewith that pertains to the represented sublane and that is different than the same attribute of the lane of which the sublane is a part. The database is compatible with navigation-related applications that use a different data model to provide navigation-related functions.

Such methods, however, still give room for improvements especially with regard to evaluating reliability of the information provided by a lane sensing method.

It is thus an object of the present invention to provide a solution providing advantageous evaluation of lane sensing in an easy manner, wherein the reliability of the outcome of a lane sensing method may be determined.

This object is solved at least in part by a method having the features of independent claim 1 . This object is further at least in part solved by a driver assistance system having the features of independent claim 8. Further, this object is solved at least in part by a vehicle having the features of independent claim 10. Advantageous embodiments are given in the dependent claims, in the further description as well as in the figures, wherein the described embodiments can, alone or in any combination of the respective embodiments, provide a feature of the present invention unless not clearly excluded.

In particular, the present invention provides a method of providing a reliability value for defining the reliability of information provided by a lane sensing process for a vehicle, wherein the method comprises the steps of:

a) providing information with regard to a position of lane markers relative to the vehicle; and

b) defining the reliability of the information provided in step a),

wherein

step b) is based on at least one of

i) the maximum distance of the outer detected lane marker candidates of a common lane boundary;

ii) the accumulated length of all detected lane marker candidates;

iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers; and

iv) a probability according to which a lane marker candidate is a lane marker. Such a method may reliably provide a reliability value for a lane sensing process and thus allows evaluating as to how much the outcome of a lane sensing method may be trusted. This may be important for processes or decisions which are based on such outcome like will be described in detail below.

In detail, the method provides a reliability value of an outcome of a lane sensing process for a vehicle. Therefore, the method as described is suited for providing data, especially in the form of one single value for each lane boundary, based on which it is possible to evaluate as to how reliable the data given by a lane sensing process are.

With this regard, a lane sensing process particularly shall mean a process which is adapted for determining lane boundaries which are defined by lane markers, the latter being representative to the course of a route such as on a street. Further, when having determined the lane boundaries, the relative position of the vehicle which is equipped with a driver assistance system for performing this method is determined. This allows giving driving information to a driver, to give a warning to a driver in case the route is left, or even to allow fully automated driving. With this regard, an outcome of the lane sensing process may be processed by a control unit to execute control with regard to lane keeping. Thus, the control unit or a further element which may be part of a driver assistance system may assist the steering so that the vehicle is driven along the lane by controlling a steering actuator or can make a warning to the driver by starting a lane departure warning system when the vehicle is about to depart from the lane. Further, fully automated driving may be realized.

Like it can be seen, it is important for further processes to take into consideration if the information provided by a lane sensing method are more or less reliable. Therefore, the method as describes takes into consideration, that identifying the road lane where the vehicle is driving and locating the vehicle within that lane by a conventional lane sensing system, or lane sensing method, respectively, does not always provide its output with the same accuracy and/or reliability. Therefore, for the consumer systems or processes of that lane location would be of great help to know how reliable that information is in order to adapt its logic accordingly. This is possible by the method as described like will be shown in detail below. The goal of the method as described is thus to provide a method for computing a single value quality measurement or confidence on each of the lane boundaries reported by a road lane marker sensing system.

In order to achieve an evaluation of reliability with regard to lane sensing like described above, the present method provides the following steps.

According to process step a), the present method comprises the step of providing information with regard to a position of lane markers relative to the vehicle. This step may under circumstances be a conventional process step which is performed by methods of and systems for lane marker sensing. Therefore, the outcome of this process step a) particularly are information about the road ahead the vehicle which is defined by the road lane markers and thus by the lane boundaries. Further, process step a) provides information about the position of the vehicle relative to the lane boundaries, or road markers, respectively, of the vehicle which is equipped with a driver assistance system which performs the method as described. Thus, having performed process step a), it is generally possible to determine if the vehicle travels in a safe manner on the road and thus inside the lane boundary.

Like known in the art, in order to achieve this, a respective driver assistance system, also known as lane recognition part, may comprise one or more environmental sensors, such as a camera, as an imaging means for taking an image of a road in front of the vehicle. Further, an image processing means is preferably provided having image processing algorithms for determining lane markers out of detected lane marker candidates. Thus, lane marker candidates are structures which are detected by the one or more environmental sensors and are possible lane markers and may be determined as being lane markers in the lane sensing process. The image of the road in front of the vehicle obtained from the environmental sensor is processed by the control unit to obtain a lane recognition result and thus an outcome of the lane sensing process, or information provided therewith, respectively. The lane recognition result contains displacement information of the vehicle to the lane and curvature information of the lane

According to process step b), the present method provides defining the reliability of the information provided in step a). In other words, process step b) allows that the outcome of step a) and thus the information about the position of the vehicle relative to the lane boundaries as well as the road structure ahead as defined by the lane boundaries, or lane markers, respectively, is evaluated with respect of its reliability and thus how much these information can be trusted. This may be important as further decisions or further process steps which are based on these information may be performed dependent on the definition of the reliability of the outcome of step a) is very reliable or if the information provided are more or less vague. This may, for example, be the case due to bad weather, such as snow or rain or mist, or even due to less colored or damaged lane markers. Therefore, a reliability evaluation may be an important feature for driver assistance systems.

In order to evaluate the information which are provided in process step a) and thus in order to perform process step b), the following is provided.

In detail, it is provided at the method as described and especially for performing process step b) that the latter and thus evaluating the reliability of the outcome of step a) is based on at least one of i) the maximum distance of the outer detected lane marker candidates of a common lane boundary; ii) the accumulated length of all detected lane marker candidates; iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers; and iv) a probability, such as a probability value, according to which a lane marker candidate is a lane marker.

Evaluating the reliability of the outcome of process step a) based on these parameters may provide significant advantages over the solutions of the prior art.

In detail, according to parameter i) and thus with regard to the maximum distance of the outer detected lane marker candidates of a common lane boundary, this parameter refers to a data range of the data which are provided by detecting lane marker candidates and thus essentially by a first step of a lane sensing process. In detail, the maximum distance of the outer detected lane marker candidates of a common lane boundary, especially of lane marker candidates being provided in one set of lane markers and thus defining a single lane boundary, may be provided. This parameter may be measured from the outer sides of the lane marker candidates or from the inner sides, referring to the direction of the defined lane boundary. In other words, the total length of a boundary detected may be taken into consideration. With this regard, it may be commonly provided that the data providing lane marker candidates are provided in a 3D point cloud. The maximum distance of the outer detected lane marker candidates of a common lane boundary in such a 3D point cloud is the euclidean distance between the extreme points of the 3D point cloud data, representing a set of lane markers, which are preferably used in the adjustment of the lane model used in step a) like described down below. It represents how wide the features are distributed in the system's field of view and thus in the coordinates of the respective environmental sensor which is used for sensing the environment and thus for detecting lane marker candidates. With this regard, it can be said that the higher is the distance of the lane marker candidates and thus the higher is the distribution of the underlying data in the 3D point cloud, the more reliable are the detected lane markers. This is mainly due to the fact that the higher the distance, or distribution, respectively, is, the more data are used. The more data used, the higher is the reliability.

Further, and with regard to parameter ii) and thus the accumulated length of all detected lane marker candidates, the sum of the length of the candidate markers which are initially detected bay be taken into consideration. Especially, the sum of the length of the candidate markers which are initially detected for two opposite boundaries bay be taken into consideration separately. This value, or these values, respectively, represent the amount of data being used in the lane boundary computation. The higher is the amount of data used, the more reliable a result of a lane boundary will be.

Optionally, this function can be altered, and a function can additionally be included that monitors both the repeatability of the length of individually detected line segments, and the repeatability of the gaps between line segments. Using this approach allows the system to avoid penalizing the confidence in cases where dashed lines are present. With this regard, a deviating length of the lane marker candidates dependent on the distance from the sensor may be taken into consideration under knowledge of the respective difference and optical effects, like it is possible without problems for the person skilled in the art.

Further, and with regard to parameter iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers may be taken into consideration. With this regard, it is often the case that the lane marker candidates detected are not simply defined as being lane markers, but they can be adjusted according to an algorithm generally known in the art and described below. With this regard, as in any algebra optimization technique, after the lane model adjustment is performed, the distance of any point used in the adjustment to the final lane model boundary obtained can be retrieved. This distance is known as residual. As the sign of the distance is not relevant in this case, the absolute value for each residual is obtained. Then, the mean of the absolute value of the residuals is representing how well the lane boundary model fits the underlying data especially separately for each lane boundary. The lower the mean of absolute residuals, the more reliable a resulting lane boundary will be, since it more accurately fits the detected data.

Further, and with regard to parameter iv), a probability, such as a probability value, or probability metric, respectively, is taken into consideration according to which a lane marker candidate is a lane marker. In other words, this parameter is a mean of detection quality metric. On the detection stage, the algorithms used to identify the candidate features to be a lane marker should provide a quality metric of its estimation. The mean of the quality metric values assigned to the lane markers used in the lane boundary adjustment is obtained as a measurement of the reliability, according to the detection phase, of the lane boundary model. The higher is the mean of the detection quality, the more reliable a lane boundary will be. For example, such a metric may be based on geometric structures which are formed by the entirety of the lane markers. This may thus be based on the fact that lane markers generally do not have a free form, but they form a straight line or a curve, for example. It may then be evaluated in said metric in how far the respective candidates fit in such a structure. However, there are generally a plurality of respective algorithms which may be used with this regard as the person skilled in the art will directly be aware of.

Given the above parameters, it may be provided that only one of the parameters i), ii), iii), and iv) is used, that all of the before-named parameters may be used or that a defined plurality of the before-defined parameters may be used for evaluating the reliability of the lane sensing process. Further, one or more of the parameters i), ii), iii), and iv) may be omitted. The before defined process has significant advantages with regard to providing a reliability value for the detected lane markers and thus for the lane boundaries and the position of the vehicle within the lane. With his regard, advantageously, a reliability value of both thee left boundary and the right boundary of the lane and thus of the lane markers defining the lane boundary provided on the left side of the road in driving direction and of the lane markers defining the lane boundary provided on the right side if the road in driving direction are provided.

With this regard, the method as described is aimed to compute a continuous single- value quality metric for each of the lane boundaries reported by a lane sensing system. The reliability value, or confidence value, respectively, assigned to each lane boundary is based on the above properties or parameters which can be easily extracted from the lane model underlying data. Therefore, this method may be performed with comparably small calculation power and is based on reliable values which may under circumstances be used in other stages.

The reliability value shall mean an index expressing the reliability of the lane recognition result, or the outcome of a lane sensing process, respectively. When the value is small, the possibility of detecting a correct position of the lane is low such as because of difficulty of visually observing the lane markers. Generally, the respective borders may be arbitrarily set. However, the reliability value is an index for judging whether or not the lane markers can be recognized, the value is normalized so as to vary in the range between 0 and 1 . The reliability of the lane recognition result is higher as the confidence is close to 1 , and is lower as the confidence is closer to 0.

It may mainly be developed at a performed lane adjustment stage, as the lane model is being computed, like described in more detail below. It may use as input the candidate lane markers, as a 3D point cloud, in vehicle coordinate system, along with an estimation on the quality of the features detected assigned at the detection phase. Once the lane is adjusted to the 3D point cloud of lane markers detected, the reliability value may be built up.

The method described will thus provide a lane boundary confidence value, or reliability value, respectively, exclusively, by means of the analysis of the underlying data used for the lane boundary computation. Therefore, this method will be able to compact a big amount of information into one unified continuous metric, simplifying the procedure used in the following processes to know and interpret the quality of the lane boundaries reported by a driver assistance system known as lane sensing system. Moreover, in the method as described, the computation of the reliability is easily customized, making it very flexible and appropriate to be adapted to any specific application requirement. This method may thus be used by any lane sensing system which shall report a confidence single value to the lane boundaries location.

The method as described can easily be integrated within a lane sensing system which is aimed to report the location and geometry of the lane which constrains the ego-motion of a host vehicle.

It may be provided that step a) and thus providing information with regard to a position of lane markers relative to the vehicle comprises the steps of: a1 ) detection of lane marker candidates; a2) transferring the lane marker candidates to a coordinate system of the vehicle; and a3) adjusting the lane marker candidates to be a real lane marker. Especially such methods steps are advantageously usable for providing information with regard to a position of lane markers relative to the vehicle and in particular in combination with defining the reliability of the information provided in this step by the steps as described before.

With this regard and especially with regard to step a1 ), according to which lane marker candidates are detected, this step may be performed by a respective environmental sensor, such as by a camera as it is generally known in the art. This phase can be composed of a single sensor or of a respective array of sensors. With this regard, the lane marker candidates and thus such features which are likely to be lane markers and thus represent a lane boundary are detected in the sensor domain or in other words in the coordinate system of the respective sensor. The output of each of the sensors is typically a 2D or 3D point cloud of lane marker candidates, referred to the specific sensor coordinate system, like it is generally known in the art.

These 2D or 3D point cloud of lane marker candidates are thus the outcome of step a1 ) and are transferred to the next step a2). According to step a2), the lane marker candidates are transferred to the coordinate system of the vehicle. In other words, this step provides that the lane marker candidates are set into relation with the vehicle. Thus, in case a plurality of sensors are used, such as in a sensor array, the lane marker candidates detected by the different sensors and present in the coordinate systems of the respective sensors, are transformed to the common vehicle coordinate system. According to this, all features, or lane marker candidates respectively, which are detected in different sensors are referred to the same coordinate system and the relative location between the lane marker candidates and with regard to the host vehicle can be retrieved.

The output of this step a2) is thus a set of lane marker candidates, which may be provided as a 3D point cloud referred to the vehicle coordinate system. As a result, this step allows providing the position of the vehicle in relative position to the lane marker candidates.

According to further step a3) it is provided that the lane marker candidates are adjusted according to be a real lane marker especially according to a predefined probability of each lane marker candidate. Thus, the lane markers that most likely define the lane that is constrained the ego-motion are selected out of the all candidates provided detection step a1 ). A lane model is adjusted to them through any optimization technique. The resulting lane model indicates the left and right boundary location with regard to the host vehicle which represents the output of the lane sensing system.

Like indicated above, such an adjustment may inter alia and in a non-limiting manner be based on geometric structures which are formed by the entirety of the lane markers. This may thus be based on the fact that lane markers generally do not have a free form, but they form a straight line or a curve, for example. Further, subsequent lane markers mostly have the same form. It may thus be evaluated in said step how far the respective candidates fit in such a structure, or how much single lane marker candidates deviate from the respective structure. This allows giving respective predefined probabilities according to which the respective feature being detected and thus the lane marker candidate really is a lane marker and thus reliably represents a lane boundary. However, there are generally a plurality of respective algorithms which may be used with this regard as the person skilled in the art will directly be aware of. Especially the before described embodiment of providing step a) and thus providing information with regard to a position of lane markers relative to the vehicle is advantageous as this step provides a reliable outcome so that the whole method is very reliable.

Apart from that, especially by performing step a) as described above in combination with step b) as described before may give significant synergistic effects. This may be mainly due to the fact that for example step a3) and thus adjusting the lane marker candidates to be a real lane marker may use for its performance parameters which also are used in all of the features i, ii), iii), and iv) I as described above with regard to step b).

Thus, due to these synergistic effects as described above, the method may be performed especially reliably and further by usage of comparably low computational power when using the embodiment as described.

According to a further embodiment, it may be advantageous that the reliability value is determined as a single value for each lane boundary defined by a group of lane markers, wherein the reliability value is based on a likelihood function for each of i), ii), iii), and iv) with usage of a cross-validation process. Especially with regard to this feature, a combination of features i), ii), iii), and iv) may be advantageous in a trustworthy manner to receive a single reliability value which provided information about the reliability of the determination of lane markers ahead.

Proving one single value as reliability value for each boundary may allow an easy estimation on the reliability and may reduce computing power for further processes.

Further, a cross-validation technique is a model validation technique for assessing how the results of a statistical analysis will generalize to an independent data set. Therefore, for solving the likelihood function for each of i), ii), iii), and iv) like described above, it is possible in a reliable manner by using cross-validation to use cross validation and thus to receive a single reliability value for each lane boundary.

With regard to further advantages and technical features of the method of providing a reliability value for defining the reliability of information provided by a lane sensing process for a vehicle, it is referred to the driver assistance system, the vehicle, the figures and the further description.

The present invention further relates to a driver assistance system for a vehicle, comprising at least one environmental sensor which is adapted for sensing the environment of the vehicle, further comprising a control unit for processing the data provided by the at least one environmental sensor, characterized in that the control unit is provided for performing a method of providing a reliability value for defining the reliability of information provided by a lane sensing process for a vehicle like described in detail above.

Therefore, the driver assistance system may be part of the vehicle as it is generally known in the art. It comprises one or a plurality of environmental sensors which are adapted for sensing the environment. For example, one or more cameras may be provided for sensing the environment and especially for detecting lane marker candidates.

Apart from that, a control unit is provided. This control unit is fed with the information provided by the one or more environmental sensors and is adapted for performing the method as described. Having calculated, or defined, respectively the reliability value, the latter may be used e.g. by a system which is suited for performing autonomous driving or it may simply give information to a driver. This may be helpful for the driver to evaluate his driving situation and thus to avoid accidents.

In order to give a warning to the driver or simply to display the defined reliability values, it may further be provided that the driver assistance system further comprises a display unit for displaying a value of reliability of an outcome of a lane sensing process.

With regard to further advantages and technical features of the driver assistance system, it is referred to the method, the vehicle, the figures and the further description.

Following the above, the present invention further relates to a vehicle, comprising a driver assistance system for performing a lane sensing process, wherein the driver assistance system is arranged like described before. Such a vehicle has the advantage of effectively and reliably providing a reliability value with regard to the information provided by a lane sensing process. This may allow autonomous driving having an improved security and additionally may help a driver of the vehicle to take correct decisions.

With regard to further advantages and technical features of the vehicle, it is referred to the method, the driver assistance system, the figures and the further description.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. Individual features disclosed in the embodiments con constitute alone or in combination an aspect of the present invention. Features of the different embodiments can be carried over from one embodiment to another embodiment.

In the drawings:

Fig. 1 shows a schematic block diagram describing process step a) of a method according to the invention according to which information is provided with regard to a position of lane markers relative to a vehicle;

Fig. 2 shows a schematic diagram which may be used in further process step b) according to which the reliability of the information provided in step a) is defined; and

Fig. 3 shows a schematic view of an outcome of the method according to the invention showed in a display of a driver assistance system.

Figure 1 shows a schematic block diagram which shows step a) of an embodiment of a method of providing a reliability value for defining the reliability of information provided by a lane sensing process for a vehicle 24. Thus, figure 1 shows the process of detecting lane markers 26, 28 and the relative position of the vehicle 24 within the lane markers 26, 28 each representing a lane boundary 30, 32 as will be shown in detail with regard to figure 3. Referring back to figure 1 , the blocks 10, 12, 14 are representative of step a1 ) and thus of detection of lane marker candidates, wherein each of the blocks 10, 12, 14 represent the detection of one sensor 34. With this regard and especially with regard to step a1 ), according to which lane marker candidates are detected, this step may be performed by a respective environmental sensor 34, such as by a camera as it is generally known in the art. With this regard, the lane marker candidates and thus such features which are likely to be lane markers and thus represent a lane boundary are detected in the sensor domain or in other words in the coordinate system of the respective sensor. The output of each of the sensors is typically a 2D or 3D point cloud of lane marker candidates, referred to the specific sensor coordinate system, like it is generally known in the art.

These 2D or 3D point cloud of lane marker candidates are thus the outcome of step a1 ) and are transferred to the next step a2) and thus to transferring the lane marker candidates to a coordinate system of the vehicle 24, which is represented by block 16.

According to step a2), the lane marker candidates are transferred to the coordinate system of the vehicle 24. In other words, this step provides that the lane marker candidates are set into relation with the vehicle 24. Thus, in case a plurality of sensors 34 are used, such as in a sensor array, the lane marker candidates detected by the different sensors 34 and present in the coordinate systems of the respective sensors 34, are transformed to the common vehicle coordinate system. According to this, all features, or lane marker candidates respectively, which are detected in different sensors 34 are referred to the same coordinate system and the relative location between the lane marker candidates and with regard to the host vehicle 24 can be retrieved. In case only one sensor 34 is used, of course the coordinate system of the single sensor 34 is transferred to the coordinate system of the vehicle 24.

The output of this step a2) is thus a set of lane marker candidates, which may be provided as a 3D point cloud referred to the vehicle coordinate system. As a result, this step allows providing the position of the vehicle in relative position to the lane marker candidates. This step is transferred to step a3), which describes adjusting the lane marker candidates, such as according to a predefined probability of each lane marker candidate, to be a real lane marker 26, 28 and which is represented by block 18.

According to further step a3) it is provided that the lane marker candidates are adjusted according to a predefined probability of each lane marker candidate to be a real lane marker 26, 28. Thus, the lane marker candidates that most likely define the lane that is constrained the ego-motion are selected out of the all candidates provided detection step a1 ). A lane model is adjusted to them through any optimization technique. The resulting lane model indicates the left and right boundary location with regard to the host vehicle which represents the output of the lane sensing system.

The outcome of this process step a) is thus the location relative to the vehicle 24 of the left lane boundary 30, shown as block 20, and of the right lane boundary 32, shown as block 22.

Having provided information with regard to a position of lane markers 26, 28 relative to the vehicle 24 like defined in process step a) as shown figure 1 , the method further executes process step b) according to which the reliability of the information provided in step a) is defined.

With this regard, step b) is based on at least one of, preferably all of, i) the maximum distance of the outer detected lane marker candidates of a common lane boundary; ii) the accumulated length of all detected lane marker candidates; iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers; and iv) a probability according to which a lane marker candidate is a lane marker.

With this regard and according to parameter i) and thus with regard to the maximum distance of the outer detected lane marker candidates of a common lane boundary, this parameter refers to a data range of the data which are provided by detecting lane marker candidates and thus essentially by a first step of a lane sensing process. In detail, the maximum distance of different lane marker candidates, especially of lane marker candidates being provided in one set of lane markers and thus defining a single lane boundary 30, 32, may be provided. In other words, the total length of a lane boundary 30, 32 detected may be taken into consideration. With this regard, it may be commonly provided that the data providing lane marker candidates are provided in a 3D point cloud. The maximum distance of the outer detected lane marker candidates of a common lane boundary in such a 3D point cloud is the euclidean distance between the extreme points of the 3D point cloud data, representing a set of lane markers 26, 28, which are preferably used in the adjustment of the lane model used in step a).

Further, and with regard to parameter iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers may be taken into consideration. With this regard, it is often the case that the lane marker candidates detected are not simply defined as being lane markers, but they can be adjusted according to an algorithm generally known in the art and described below. With this regard, as in any algebra optimization technique, after the lane model adjustment is performed, the distance of any point used in the adjustment to the final lane boundary 30, 32 obtained can be retrieved. This distance is known as residual. As the sign of the distance is not relevant in this case, the absolute value for each residual is obtained. Then, the mean of the absolute value of the residuals is representing how well the lane boundary model fits the underlying data especially separately for each lane boundary 30, 32. The lower the mean of absolute residuals, the more reliable a resulting lane boundary will be, since it more accurately fits the detected data.

Further, and with regard to parameter iv), a probability, such as a probability value, or probability metric, respectively, is taken into consideration according to which a lane marker candidate is a lane marker 26, 28. In other words, this parameter is a mean of detection quality metric. On the detection stage, the algorithms used to identify the candidate features to be a lane marker should provide a quality metric of its estimation. The mean of the quality metric values assigned to the lane markers used in the lane boundary adjustment is obtained as a measurement of the reliability, according to the detection phase, of the lane boundary model. The higher is the mean of the detection quality, the more reliable a lane boundary will be. For example, such a metric may be based on geometric structures which are formed by the entirety of the lane markers.

In detail and with regard to process step b), in order to provide the reliability value based on the parameters i), ii), iii), and iv) for each of these parameters i), ii), iii), and iv), a custom likelihood function is defined. Of course, in case one or more of the parameters are omitted, the custom likelihood function is provided for the remaining parameters.

According to this, the custom likelihood functions may be defined by intervals which may for example be constant or linear in the following way:

According to this, P(x) is the probability of the lane boundary 30, 32 based on lane marker candidates to be a valid one according to the value of the parameter x in the range [0, 1 ].

Further, p, is the probability of the assessed lane boundary based on the lane marker candidates to be a valid one according to the value of the parameter x, wherein the value of the parameter x is in the range [Ι _ι , Ι,] . Further, p, can be also any function of x, wherein as an example first degree polynomials or constant values may be used. In other words, pi describes the probability of the assessed lane boundary 30, 32 based on the lane marker candidates to be a valid one according to the value of each of the parameters i), ii), iii) and iv).

Hence, depending on the values of the lane boundary parameters and thus especially depending on the values of the parameters i), ii), iii), and iv), the solution of the custom likelihood function will give the basis for a lane boundary quality metric with respect to that particular parameter i), ii), iii), and iv), respectively.

According to figure 2, an example of the custom likelihood function defined for the data range parameter and thus for the parameter i) is shown. With this regard, the x-axis shows the l-value, whereas the y-axis shows the value p(A) and thus in the present case p(i). In order to solve the custom likelihood function, the pairs ( ρ,, I, ) that define the custom likelihood function for each lane boundary 30, 32, reliability values and thus confidence parameters are preferably determined during a cross-validation process. Thus, the l-values are determined by subsequently checking different values and see which values fit best to the respective likelihood function. Then, by solving the respective function, a value P(x) and thus p(i), p(ii), p(iii) and p(iv) may be calculated, wherein the respective values may be in the range of [0,1 ].

The final confidence or quality metric for the lane boundary 30, 32 will be the product of the probabilities assigned for the individual parameters according to the following:

Reliability value = p(i) ^χ p(ii) ^χ p(iii) ^χ p(iv), wherein p(i) is the probability according to parameter i), p(ii) is the probability according to parameter ii), p(iii) is the probability according to parameter iii), and p(iv) is the probability according to parameter iv).

Hence, the reliability value computed represents a single value quality metric for each of the lane boundaries 30, 32 reported by a lane sensing system, preferably comprising parameters i), ii), iii), and iv) possibly being continuous in the range [0, 1 ]. The reliability of the lane boundary reported is increased as the confidence is approaches 1 .

Following, an example image which may be provided in a display 36 of a driver assistance system is shown in figure 3.

Figure 3 shows in a very schematic way, in the center an image of a frontal camera mounted in a vehicle 24. In detail, a route 38 with a left lane boundary 30 and a right lane boundary 32 is shown, the lane boundaries 30, 32 being represented by lane markers 26, 28. Location and geometry of the lane markers 26, 28 is determined by the lane sensing method as described.

As discussed, along with the location and geometry of the lane boundaries 30, 32, the system is providing a single-value confidence estimation and thus a reliability value for each lane boundary 30, 32. Those are the values next to the left box 40 and the right box 42 respectively. The left box 40 and its value is representative of the reliability value for the left lane boundary 30, whereas the right box 42 and its value is representative for the reliability value of the right lane boundary 32. For the sake of simplicity in the representation, the reliability value has been casted to the [0, 100] range instead of the [0,1 ] range like described before.

It can be seen that the reliability value for the left lane boundary is 75, whereas the reliability value for the right lane boundary is 82, wherein the letter L and R stand for the left boundary 30 and the right boundary 32, respectively.

Thus, it can be evaluated that, that the lane provided is comparably reliable.

On the right side of the image, there is a top-view representation of the same lane sensing output. According to this, the vehicle 24 is shown, wherein the position of the vehicle 24 in the route 38 and thus between the lane boundaries 30, 32 is shown. In detail, it is shown that the vehicle travels central between the lane boundaries 30, 32 and thus is driving safely. Further, the sensors 34 are shown which are part of a driver assistance system of the vehicle 24 and which are adapted for sensing the environment of the vehicle 24. According to figure 3, four environmental sensors 34 are shown. Reference signs list

block

vehicle

lane marker

lane boundary

sensor

display

route

box

Claims

Patent claims

1 . Method of providing a reliability value for defining the reliability of information provided by a lane sensing process for a vehicle (24), wherein the method comprises the steps of:

a) providing information with regard to a position of lane markers (26, 28) relative to the vehicle (24); and

b) defining the reliability of the information provided in step a),

characterized in that

step b) is based on all of

i) the maximum distance of the outer detected lane marker candidates of a common lane boundary (30, 32) ;

ii) the accumulated length of all detected lane marker candidates;

iii) the mean deviation of positions of initially detected lane marker candidates to positions of lane markers (26, 28); and

iv) a probability according to which a lane marker candidate is a lane marker (26, 28).

2. Method according to claim 1 , characterized in that step a) comprises the steps of a1 ) detection of lane marker candidates;

a2) transferring the lane marker candidates to a coordinate system of the vehicle (24); and

a3) adjusting the lane marker candidates to be a real lane marker (26, 28).

3. Method according to claim 1 or 2, characterized in that characterized in that step b) is further based on the repeatability of the gaps between lane marker candidates.

4. Method according to any of claims 1 to 3, characterized in that step b) is further based on the repeatability of the length of lane marker candidates.

5. Method according to any of claims 1 to 4, characterized in that the value of

reliability is determined as a single value for each lane boundary (30, 32).

6. Method according to any of claim 5, characterized in that the value of reliability is determined as a single value for each lane boundary (30, 32) based on a likelihood function for each of i), ii), iii), and iv) with usage of a cross-validation process.

7. Driver assistance system for a vehicle (24), comprising at least one environmental sensor (34) which is adapted for sensing the environment of the vehicle (24), further comprising a control unit for processing the data provided by the at least one environmental sensor (34), characterized in that the control unit is adapted for performing a method according to any of claims 1 to 6.

8. Driver assistance system according to claim 8, characterized in that the driver assistance system further comprises a display (36) for displaying the defined reliability value.

9. Vehicle, comprising a driver assistance system for performing a lane sensing

process, characterized in that the driver assistance system is arranged according to any of claims 7 or 8.