GB2488886A

GB2488886A - Evaluating the attention of a driver of a motor vehicle

Info

Publication number: GB2488886A
Application number: GB1203880.8A
Authority: GB
Inventors: Thomas Schramm; Christian Rudolf Jerusalem; Oliver Schepp
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-03-11
Filing date: 2012-03-05
Publication date: 2012-09-12
Anticipated expiration: 2032-03-05
Also published as: DE102011013663A1; GB2488886B; GB201203880D0

Abstract

A method for evaluating the attention of the driver of a vehicle 1 comprises the steps of detecting the radius of curvature of a road 2 from a vehicle mounted camera and/or navigation system map; detecting an actual steering angle of the vehicle 1 from an angle sensor on the steering wheel or road wheels; then evaluating the drivers attention on the basis of the deviation between their comparable values. Inattention is assumed when significant deviation 20,21 on a graph plot of the inverse radius of curvature exceeds limit values 17,18 of a tolerance interval, or if actual deviation values change their positive and negative sign more than twice when passing through a curve, or when the steering angle is less than the radius of curvature of the curve. A warning signal may be transmitted to the driver. Deviations 15,19 may be disregarded when non-significant, or if vehicle speed is slow, or if the road curvature is so large it cannot be seen in its entirety.

Description

A METHOD FOR THE EVALUATION OF DRIVER ATTENTION

Description

The present invention relates to a method for the evaluation of the attention of the driver of a travelling motor vehicle.

Apparatuses and methods are known from numerous publica-is tions which monitor steering activities of the driver of a motor vehicle in order to evaluate the quality thereof and to assess the attention level of the driver on the basis of said evaluation and to optionally generate a warning.

A widely used approach for attention evaluation is to monitor the time sequence of steering movements of the driver and to assume lack of attention in the case of fulfillment of predetermined criteria, such as in the case of an abrupt steering movement following the phase of calm steering.

This approach is known from DE 10 2008 056 593 Al and further documents

cited in this specification.

One problem that is common to all these known methods is the lack of consideration of external circumstances. It may be necessary for a fully attentive driver after a phase of calm steering to perform an abrupt steering movement in order to follow a curve of the road after a prolonged straight section. Exclusive monitoring of the steering movement does not allow making any secure evaluation.

A steering assistance system is known from EP 1 602 558 A2, which controls an auxiliary torque by means of images of a camera or map data, which auxiliary torque is exerted by power-assisted steering in order to support the driver over a road section in front of the vehicle. Monitoring of the drivers attention is not provided within the scope of this assistance system.

It is the object of the invention to provide a method for the eva?-s uation of driver attention which prevents evaluation errors which are caused by driving in curves of a road which is travelled by the vehicle.

This object is achieved by a method with the following steps: a) Detection of the radius of curvature of a road section before the vehicle; b) Detection of a steering angle performed by the driver in the motor vehicle; c) Estimation of a first value of a comparative quantity on the basis of the detected radius of curvature; d) Estimation of a second value of the comparative quantity on the basis of the detected steering angle, and e) Evaluation of the attention of the driver on the basis of the deviation between the first and second value of the comparative quantity.

The comparative quantity is only used for the purpose of mak-ing comparable the detected path and the path steered by the driver. The comparative quantity can therefore be a radius of curvature for example, with the first value being the radius of curvature itself as detected in step a) and the second value a radius of curvature resulting from the steering angle as detected in step b). The comparative quantity can also be a steering angle, wherein in this case the first value is appropriately a steering angle required for driving the radius of curvature detected in step a) and the second value the steering angle itself as detected in step b). The comparative quantity can also be a third quantity whose first value can be calculated from the radius of curvature detected in step a) and whose second value can be calculated from the steering angle as detected in step b). Such a third quantity can es- pecially be a lateral acceleration which can be calculated both from the radi- us of curvature and from the steering angle by respectively taking into ac-count the speed of the vehicle.

Different criteria are considered in the evaluation of the atten-tion in step e), which criteria can be used in various embodiments of the method in accordance with the invention either exclusively or also in combi-nation with one another. )

In the simplest of cases a low amount or lack of attention can be assumed when the amount of the deviation exceeds a limit value, wherein said limit value can be chosen appropriately depending on the detected radi-us of curvature of the curve when travelling through a curve.

it is another potential criterion when the deviation changes its plus/minus sign more than twice when passing through a curve. When an attentive driver follows the curve of a road, the path covered by the driver can intersect the curve, i.e. the vehicle wift approach an inner edge of the is roadway when travelling through the curve and will move away from the same when the end of the curve has been reached. For this purpose, the radius of curvature of the distance covered by the vehicle when travelling through a central region of the curve must be slightly larger than the radius of curvature of this region. In order to enable this without leaving the road, the driver needs to use a higher steering angle towards the start and end of the curve than corresponds to the radius of curvature there, or he needs to steer over even before the entrance into the curve. In the one as in the other case, the radius of curvature of the covered distance is locally smaller at the start and end of the curve than the one of the road. Two changes in the sign of the deviation can therefore also be regarded as normal in an attentive driver.

High number of changes in the sign is an indication of insecurity or inatten-tiveness.

It is another indication for inattentiveness when the detected steering angle corresponds to a smaller radius of curvature than the smallest detected radius of curvature of the curve, which therefore means that the driver steers the steering wheel over more strongly than would be required even at the narrowest point of the curve.

The detection of the radius of curvature can be based on imag-es supplied by a camera of the road disposed in front of the vehicle.

In this case, in step a) the path situated in front of the vehicle can be assumed at an at least locally constant distance from a boundary of the road as recognizable from the images of the camera. This corresponds to the assumption that the driver will pass through the curve without inter-secting.

Alternatively, the detection of the radius of curvature can be based on map data of a road travelled by the vehicle.

In this case, the radius of curvature of the path can be assumed to be equal to the radius of curvature of the road at the respective location of the vehicle.

It is more realistic however that when the road has a curve the path detected in step a) will intersect this curve.

Preferably, the inclination of the driver to intersect curves will be evaluated on the basis of the deviation between the first and the second val-ue when travelling through at least one curve, and said inclination will be taken into account in the detection of the path in step a) when passing through a further curve.

Deviations between the first and second value can be disre-garded in the evaluation of driver attention when the speed of the vehicle and/or the radius of curvature lies beneath a predetermined limit value, i.e. especially when the vehicle maneuvers slowly and/or when the radius of cur-vature is so large on a highway for example that the driver is unable to view the curve in its entirety and it can therefore not be passed without repeated steering corrections even with full attention of the driver.

A further subject matter of the invention is a computer program product with a program code means which enable a computer to perform the method as described above.

Further features and advantages of the invention will be ex- plained below in closer detail by reference to the following description of em- bodiments by using the enclosed drawings. This description and the draw-ings will also disclose features of the embodiments which are not mentioned in the claims. Such features can also occur in combinations other than those specifically disclosed herein. The fact that several such features are men-tioned in the same sentence or in another kind of context with respect to each other therefore does not permit the conclusion that they are only able to occur in the specifically disclosed combination. It shall principally be as- sumed instead that individual features of several such features can be omit- ted or modified insofar as this does not question the usability of the inven-tion. The drawings show as follows: Fig. I shows a typical application situation of the method in accordance with the invention in a top view; Fig. 2 shows a block diagram of a system in accordance with the invention for evaluating driver attention; Fig. 3 shows graphs of the curvature of the curve of Fig. I and the path of the vehicle travelling through the same as a function of the distance; Fig. 4 shows a diagram which is provided analogously to Fig. 3, comprising a graph indicating the curvature of the path of the vehicle when intersecting the curve; Fig. 5 shows a top view in analogy to Fig. I of the path of the vehicle when intersecting the curve, and Fig. 6 shows a diagram with a graph in analogy to Figs. 3 and 4, which shows the curvature of the path of the vehicle which is expected by the evaluation system in accordance with the invention after the adjustment to the inclination of the driver to inter-sect curves.

Fig. I shows a schematic top view of a motor vehicle 1 which moves on a road 2. Only one traffic lane of the road 2 is shown, which is de-limited on its right side in the travelling direction of the motor vehicle I by a roadway marking 3 and on its left side by a dashed median strip 4. The mo-tor vehicle is shown at a point in time where it is still moving on a straight section 5 of the road 2, while a curve 6 of the road is already in the field of view of the driver of the motor vehicle I and also the camera 7, which is io preferably attached to an upper region of a windshield of the vehicle I be-tween said windshield and an inside rear-view mirror in order to enable the camera to have a similar field of view Uke the driver.

The camera 7 is a part of an on-board computer system as is shown in Fig. 2, which computer system can be programmed to assume oth-er checking and support tasks in addition to monitoring driver attention. A processor B of the on-board computer system is connected with the camera 7 in order to receive images of the road 2 disposed in front of the vehicle I as recorded by said camera and to identify in said images the boundaries 3, 4 of the traffic lane of the road 2 disposed in front of the vehicle I and to es-timate the curvature of the road 2 on the basis of the progression of the boundaries 3, 4.

An angle sensor 9 which is also connected to the processor 8 is arranged on a steering wheel 10 of the vehicle I or at any other suitable lo-cation of the steering system in order to detect the steering angle of the steering wheel 10 or the running wheels of the vehicle I which are steered by the same. Said steering angle will determine the curvature of the path covered by the vehicle 1, which path will only correspond in a satisfactory manner with the detected curvature of the road 2 when the driver is suffi-ciently attentive during the steering. Since the radius of curvature of the road 2 and the steering angle of the steering wheel 10 are not directly comparable with one another, at least one of the two detected quantities needs to be converted. When disregarding the centrifugal forces acting on the vehicle 1 and the slip resulting therefrom, there is a distinct relationship between the curvature of the path and the steering angle. It is also possible in the conver-sion of the steering angle into a curvature of the path or the conversion of the detected curvature of the road 2 into a steering angle which allows the vehi-cle 1 to follow the progress of the road in a precise manner to consider the vehicle speed and the slip resulting therefrom or a known inclination of the vehicle 1 towards oversteering and understeering.

In the illustration of Fig. 2, the processor 8 is further connected to a vehicle navigation system 11. The navigation system 11 is not mandato-ry within the scope of the present invention, but it can replace the camera 7 to in that its processor 12 determines the current position and travelling direc- tion of the vehicle I in the known manner by means of satellite signals re- ceived via a radio interface 13, and provides information about the next fol-lowing curve of the road 2 travelled by the vehicle 1 from a digital roadmap saved to a memory 14 and reports such information to the processor 8. t5

Preferably, the attention evaluation system comprises both the camera 7 and the navigation system 11 because both systems can advanta-geously support one another. In the simplest of cases the support consists of the fact that the camera 7 can recognize curves which for reasons of scale are not contained in the digital roadmap, and the digital roadmap can still provide information on the curvature of an upcoming curve when the camera 7 is unable to do this due to adverse visual conditions such as darkness, fog or the like. It is also possible to use the information supplied by the naviga-tion system 11 for verifying a curvature estimated on the basis of camera data or to have such information included in the image evaluation in that the direction and an approximate radius of the next curve to be identified in the images of the camera 7 are predetermined to the processor 8. Furthermore, the navigation system 11 can supply additional information especially on the length of a curve to be travelled when it is not visible up to its end in the im-ages of the camera 7.

The radius of curvature of a curve is usually not constant over its entire length. Since a driver requires time when entering curve in order to adjust the steering wheel position and the radius of curvature of the path fol- lowed by his or her vehicle in this time will change continuously, a progres-sion of a curve in which the curvature at the beginning and at the end will increase and decrease gradually and has its maximum in the middle of the curve facilitates travelling through the curve. The processor 8 can take such a progression into account in that it adjusts a model progression as is shown in Fig. 3 as a graph 15 to an image of the curve 6 as supplied by the camera 7 in which the curvature, expressed as an inverse value hr of the local radi-us of curvature, will linearly rise in an initial section of the curve, will remain constant in a middle section and will linearly decrease again in an end sec-tion. Such a curve model has four adjustable parameters, namely the length of its three sections and the curvature of the central section. I0

Since the detection of the curvature of the curve 6 always en-tails a certain amount of uncertainty irrespective of whether it is based on images of the camera 7 or on data of the navigation system 11, the proces- sor 8 implements a tolerance interval 16 around the graph 15, which is lim-ited in Fig. 3 by the dashed graphs 17, 18, within which the curvature of the path of the vehicle I should come to lie, so as to be evaluated as coinciding with the curvature of the curve 6.

A graph 19 in bold print shows a typical progression of the cur-vature of the path of the vehicle 1 calculated from the position of the steering wheel 10 when passing through the curve 6. In this case, the vehicle obvi-ously strictly follows the progression of the curve 6, corresponding to the path designated in Fig. 1 with reference numeral 26; the curvature of path as calculated from the steering wheel position does not leave the tolerance in-terval 16. Non-significant deviations with changing signs between the graphs 15, 19 in the initial section of the curve 6, i.e. in the linearly ascending region of the graph 151 can be caused by the fact that when the driver grips over the steering wheel 10 he or she is unable to rotate it with constant speed, which is therefore is no indication for lack of attention.

There can be indications of lack of attention when at a random location of the curve 6 the curvature of the path of the vehicle is stronger than the maximum curvature c of the graph 17, as illustrated in the example of a graph section 20, or when the curvature of the path of the vehicle 1 de-viates significantly from the tolerance interval 16. The question whether a deviation is significant should appropriately depend both on its strength and its duration, e.g. it can be assumed as a criterion that the area of an area section 22 needs to exceed a minimum value, which area section is delim-ited on the one hand by the tolerance interval 16 and on the other hand by a graph section 21 extending outside of the tolerance interval.

The recognition of an event indicating lack of attention can lead to the consequence either immediately or only when the frequency of such events exceeds the limit value that the processor 8 will actuate a signal transmitter 23 in order to warn the driver.

A progression of the curve of the path of the vehicle 1 when passing the curve 6 which is typical for many drivers is shown in Fig. 4 as a graph 24 which is superimposed on the graphs 15, 17, 18 of Fig. 3. Graph 24 shows that the driver of the vehicle 1 begins to change the steering angle already before the entrance into the curve 6, then maintains the steering an-gle in a substantially constant manner which corresponds to a curvature of the path which lies beneath the tolerance interval 16, and returns to straight travel only shortly after leaving the curve 6 again. The progression of the graph 24 is typically not the result of lack of attention of the driver, but occurs when the driver intersects the curve 6, i.e. when the vehicle 1 follows the path designated in Fig. 5 with reference numeral 25, in the progression of which it temporarily strongly approaches the inner boundary of the curve 6, which in this case is the median strip 4, When passing several curves, the processor 8 compares the progression of the curvature of these curves ac- cording to graph 15 as estimated from the data of the camera 7 or the navi-gation system 11 with the progression of the curvature as actually steered by the driver according to graph 24 and it learns thereby to estimate the inclina-tion of the driver towards intersecting curves and to take this into account in the detection of a path through a curve directly in front of the vehicle. Such learning can occur in such a way for example that the processor 8 deter- mines a compensating factor for the travelled curves by which the progres- sion 15 of the curvature of the travelled curve needs to be vertically com-pressed and horizontally expanded in order to achieve optimal agreement with the actually travelled graph 24, and said corrective factor is applied to the graphs 15, 17, 18, optionally averaged over several curves.

-10 -Fig. 6 shows the result of such a procedure. The graph of the progression of the curvature which was originally determined for the curve 6 is the same as in Figs. 3 and 4 and is designated there with the reference 15. A vertical compression and a horizontal expansion of the graph 15 of 10% for example in this case lead to the graph 15' of Fig. 6. A respective operation on the graphs 17, 18 supplies the graphs 17', 18' delimiting the tolerance interval 16' in Fig. 6. Graph 24 extends completely within the toler-ance interval 16' and will therefore not be misunderstood as a reference to lack of attention. Actual indications to lack of attention can also be in this to case, as described with reference to Fig. 2, an exceeding of the maximum curvature cm of the graph 17' or a significant deviation from the tolerance interval 16'.

-II -

LIST OF REFERENCE NUMERALS

1 Motor vehicle 2 Road 3 Roadway marking 4 Median strip Straight section 6 Curve 7 Camera 8 Processor 9 Angle sensor Steering wheel 11 Navigation system of the vehicle 12 Processor 13 Radio interface 14 Memory Graph 16 Tolerance interval 17 Graph 18 Graph 19 Graph Graph 21 Graph section 22 Area section 23 Signal transmitter 24 Graph Path of the vehicle 26 Path of the vehicle

Claims

-12 -CLAIMS: 1. A method for evaluating the attention of the driver of a motor vehicle (1), comprising the following steps: a) detection of the radius of curvature of a path (26; 25) which is disposed in front of the motor vehicle (1) and is to be passed by said vehicle; b) detection of a steering angle steered by the driver of the motor vehicle (1); c) estimation of a first value (15; 151; 16; 16') of a comparative quantity on the basis of the detected radius of curvature; d) estimation of a second value (19; 24) of the comparative value on the basis of the detected steering angle, and is e) evaluation of the attention on the basis of the deviation be-tween the first and second value of the comparative quantity.
2. A method according to claim 1, characterized in that the comparative quantity is chosen among -a radius of curvature, with the first value (15; 15'; 16; 16') of the de-tected radius of curvature being the radius of curvature itself and the second value (19; 24) being a radius of curvature resulting from the detected steering angle; -a steering angle, with the first value being a steering angle neces-sary for driving the detected radius of curvature and the second value being the detected steering angle itself, and -a lateral acceleration, with the first value being the lateral accelera-tion resulting from the detected radius of curvature and the speed of the vehicle and the second value being the lateral acceleration result-ing from the detected steering angle and the speed of the vehicle.
3. A method according to claim I or 2, characterized in that the attention will be evaluated as low if the amount of the deviation exceeds a limit value, and/or if when passing through a curve (6) the plus/minus sign of the deviation changes more than twice, and/or if when passing -13 -through a curve (6) the detected steering angle corresponds to one that is smaller than the smallest detected radius of curvature (cm).4. A method according to claim 1, 2 or 3, characterized in that the detec-tion of the radius of curvature is based on images of a road disposed in front of the vehicle (1), which images are supplied by a camera (7).
4. A method according to claim 3, characterized in that in step a) the path (26) disposed in front of the vehicle (1) is assumed to be in an at least locally constant distance from a boundary (3; 4) of the road (2).
5. A method according to claim 1, 2 or 3, characterized in that the detec-tion of the radius of curvature is based on roadmap data (14) of a road (2) travelled by the vehicle (1).
6. A method according to claim 5, characterized in that the radius of cur- vature of the path (26) is assumed to be equal to the radius of curva-ture of the road (2) at the location of the vehicle (1).
7. A method according to claim 3 or 5, characterized in that when road (2) comprises a curve (6) the path (25) detected in step a) will inter-sect the curve (6).
8. A method according to claim 7, characterized in that the inclination of the driver to intersect curves is evaluated on the basis of the deviation between first and second value when travelling through at least one curve, and said inclination is taken into account in the detection of the path (25) in step a).* 30
9. A method according to one of the preceding claims, characterized in that the deviation between the first and second value will be disre-garded in the evaluation of the attention of the driver when the speed of the vehicle and/or the radius of curvature lies beneath a predeter-mined limit value.-14 -
10. A computer program product with program code means which enable the computer to perform the method according to one of the preceding claims.