Abstract:
The invention discloses a method of determining the ability of a vehicle to pass through a restricted gap in the roadway, including the steps of: detecting a restricted gap in the roadway, defining an image of the vehicle, and comparing the vehicle image with the restricted gap.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention discloses a method of determining the ability of a vehicle to pass through a restricted gap in the roadway and a system of assisting the vehicle&#39;s driver for this purpose. 
     It finds particular application in the field of motor vehicles. 
     2. Description of the Related Art 
     While a vehicle is being driven, there is likelihood that a restricted gap may be encountered on the roadway in the direction of travel. A gap of this type in the roadway may be, for example, a narrowing at road works, a tunnel, restricted headroom under a bridge or a parking space. The restriction may be formed by a limited width of the roadway and/or limited headroom and/or restricted length. 
     It was oftentimes difficult to determine whether the vehicle is able to pass through the restricted gap in the roadway without damage. 
     There is, therefore, a need for an improved system and method for determining whether the vehicle is able to pass through a restricted gap in a roadway. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a method and an associated driver assistance system making it possible to determine whether the vehicle is able to pass through a restricted gap in the roadway without damage. 
     According to the invention, this object is achieved by a method of determining the ability of a vehicle to pass through a restricted gap in the roadway including the steps of:
         detecting a restricted gap in the roadway,   defining an image of the vehicle, and   comparing the vehicle image with the restricted gap.       

     A method of this type has the advantage of making it possible to determine in a simple manner whether the vehicle will pass through the gap. It thus avoids damage to the vehicle or, more seriously, avoids accidents. Furthermore, it provides a means of assisting a user of the vehicle to maneuver the vehicle. 
     In a non-limitative embodiment, comparison of the vehicle image with the gap is automatic. This is faster than a comparison made by the vehicle driver and allows the driver to react more rapidly when a restricted gap is encountered in the roadway. In addition, it avoids the driver having to make a manual comparison. 
     In a non-limitative embodiment, the gap is represented on a display and an image of the vehicle is shown in the plane of the image and on a dimensional scale commensurate with the size of the gap, so that a comparison of the gap with the vehicle image can be made to visually determine whether the vehicle can pass through the gap without damage. 
     Thus, if the dimensions of the vehicle image are smaller than the clearance dimensions of the gap, the vehicle can pass there through without damage. The means providing the image then determine whether the vehicle is able at a later time to pass without damage through the gap located further ahead at the time of the comparison. 
     In a non-limitative embodiment, the restricted gap shown on the display forms part of an image of the environment recorded by means of a camera. In this image of the environment shown on the display, the vehicle image is projected so that it corresponds, in the plane of the image of the gap, to the dimensional scale of the latter. 
     In a non-limitative embodiment, when the comparison is made by the driver of the vehicle, to project the vehicle image in the gap on the display, the plane of the image and the position of the vehicle image are manually adjustable on the display so that the vehicle image can be moved to the location of the gap. To make this adjustment, the driver can use manually-operated means, for example sliding, rotary and push button switches. The driver can also re-position the image on the display to the appropriate location of the gap and, once there, can then modify the dimensional scale so that the dimensional scale of the vehicle image corresponds to the gap or to its environment. 
     In a non-limitative embodiment, the position and the plane of the vehicle image are automatically transferred on the display to the location of the gap. By virtue of this, manual movement of the vehicle image on the display can be dispensed with. 
     When the vehicle image on the display is moved to the location of the gap and the dimensional scale is adjusted accordingly, it can be determined whether the vehicle is able to pass through the gap without damage. 
     In a non-limitative embodiment, the gap is fixed in the display. This avoids the gap moving at the same time as the vehicle is moving. 
     In a non-limitative embodiment, the vehicle image is sized in relation to a speed of the vehicle and a projection distance, the latter being the distance between the front of the vehicle and the image. This enables the driver to ascertain how his/her position is changing in relation to the gap. 
     In a non-limitative embodiment, the vehicle image is defined in relation to a model of the vehicle. Thus, the exact dimensions of the vehicle are taken into account during the comparison between the image and the gap. The comparison is thus more precise. 
     In a non-limitative embodiment, in the case where the vehicle image and zones delineating the gap (for example a tunnel entrance, bridge support and/or road works barrier) overlap, a warning signal is emitted. This serves to warn the driver that the vehicle is unable to pass through. 
     In a non-limitative embodiment, the vehicle image is represented by the outline of the vehicle and/or a line depicting its outline. If a line or a semi-transparent image is provided, the advantage is that the zone situated within the vehicle outline thus depicted is not masked on the display. 
     In a non-limitative embodiment, to correctly adjust the size of the vehicle image in the gap, provision can be made to show in the bottom part of the display a travel path of the vehicle towards the vehicle image. 
     It extends in particular along the roadway, up to the vehicle image, the width of the travel path corresponding in particular to the width of the vehicle image (taking into account the width of the wheels) in the respective plane of the image. If the travel path is shown in the form of a bar, this bar becomes narrower in perspective from the bottom edge of the image up to the vehicle image. With the aid of the travel path depicted on the display, it is then possible to obtain a correct dimensional scale of the vehicle in the plane of the image or to the position of the gap. To set the correct dimensional scale, the travel pathway can be selected along the roadway, the bottom edge of the vehicle image being adjusted to the height of the gap. 
     In a non-limitative embodiment, it is possible that the width and/or height of the vehicle are made visible for a user of the vehicle in the direction of travel in front of the vehicle by means of light sources disposed on the vehicle. By virtue of this, the driver is able, by observing the environment in front of him and/or the display, to determine where the vehicle will go if it continues in the same direction or if it is possible to pass through the gap in the direction taken. Consequently, the driver is guided even more effectively and the risk of collision when passing though the gap is reduced. The light sources can in particular emit colored light. 
     In a non-limitative embodiment, it is possible to arrange for the light sources to transmit along the roadway and/or to project onto the roadway two lines delineating the width and/or height of the vehicle. 
     The foregoing object is also achieved by a driver assistance system implementing the method according to the invention, including:
         a camera to record the environment,   an evaluation unit, this unit including:
           image analysis means to detect a restricted gap in the roadway,   means of comparing the gap with an image of the vehicle, and   
           a display.       

     In a non-limitative embodiment, a reproduction of the recorded environment and an image of the vehicle are shown on the display. 
     In a non-limitative embodiment, the assistance system additionally includes manually-operated adjustment means and/or an automatic adjustment unit to adjust the position and the plane of the vehicle image and to re-position the vehicle image on the display. 
     In a non-limitative embodiment, the assistance system additionally includes light sources such that the width and/or height of the vehicle are made visible for a user of the vehicle. 
     These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the invention will be better understood by reference to the description and the non-limitative figures in which: 
         FIG. 1  is a schematic representation of a driver assistance system according to the invention; 
         FIG. 2  illustrates a first example of a display generated by the system according to  FIG. 1 ; 
         FIG. 3  illustrates a second example of a display generated by the system according to  FIG. 1 ; 
         FIG. 4  illustrates a third example of a display generated by the system according to  FIG. 1 ; and 
         FIG. 5  illustrates a fourth example of a display generated by the system according to  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The driver assistance system  10  depicted schematically in  FIG. 1  includes:
         a camera  12 ,   an evaluation unit  14 , this unit including:
           image analysis means or image analyzer  14   a  to detect a restricted gap in the roadway through which the vehicle needs to pass,   comparator means or a comparator  14   b  for comparing the gap with an image of the vehicle, and   
           a display  16 .       

     In a non-limitative embodiment, the system  10  additionally includes:
         two light sources  15 , and   adjustment means or adjustment  18  operated by the vehicle user, which by way of non-limitative examples can be tactile switches of the sliding, rotary or pushbutton type such as a rotary button and/or a trackball, connected to the evaluation unit  14 .       

     In a non-limitative embodiment, the comparison means  14   b  include an automatic adjustment unit to adjust the position and the plane of a vehicle image on the display  16  and to move the vehicle image to the location of the gap. 
     As will be seen in detail below, an image (which may also be referred to as a profile) of the vehicle will be defined and subsequently compared to a restricted gap in the roadway that has been previously detected. This image takes into account at least one dimension (width/height/length) of the vehicle and the comparison is made between at least one vehicle dimension and the gap depending on the type of restriction in the roadway (road, tunnel, bridge, parking space, etc.). For example, if the restriction is a bridge, the height of the vehicle is taken into account, if the restriction is a tunnel, the height and the width of the vehicle are taken into account, and if the restriction is a parking space, the length of the vehicle may also be taken into account. As will be seen, this image and the gap may or may not be displayed on the display  16 . 
     The vehicle environment located ahead of the vehicle in the direction of travel is recorded by the camera  12 . 
     The description below can also apply in the reverse direction of travel. 
     This recorded environment can be shown on the display  16 . When the environment is thus displayed, both light sources  15  (illustrated schematically in  FIG. 1 ) emit two lines  17  delineating the width of the vehicle b along the roadway. These lines  17  are visible for the driver of the vehicle by observing the environment in the direction of travel. Where appropriate, the light sources  15  can be designed so that the lines  17  emitted thereby are visible on the display  16  for the driver. In particular, laser light sources can be used as the light sources  15 . The light sources  15  can in particular be mounted in the housing of each headlamp. Other types of sources can of course be used. 
       FIGS. 2 ,  3  and  4  illustrate for example an image of the environment recorded by the camera  12 . The image of the environment shows the roadway  20 , the path of the vehicle being delineated on the left-hand side by a median line  22  and on the right-hand side by a pavement  24 . Oncoming traffic  26  is traveling in the opposite lane. As can be seen on the display image, the vehicle is approaching an underpass which is restricted on its right-hand side by bridge supports  28 . The area between the bridge support  28  and the oncoming traffic  26  represents a restricted gap in the roadway  30 . The gap is detected and determined by the image analysis means  14   a . In a first non-limitative example, such image analysis means  14   a  are described in the document “Rapid Object Detection Using a Boosted Cascade of Simple Features—P. Viola—Mitsubishi Electric Research Labs, M. Jones—Compaq CRL—Conference on computer vision and pattern recognition 2001”. A second non-limitative example of such analysis means is described in patent application FR 05 11 488, which was published as French Patent Application No. 2893173, which is equivalent to U.S. Patent Publication No. 2007/0198189, all of which are incorporated herein by reference and made a part hereof. 
     The driver assistance system  10  makes it possible to determine whether the vehicle is able to pass through the restricted gap  30  in the roadway  20  without damage. 
     To this end, in a first non-limitative embodiment, the display  16  depicts, as shown in  FIGS. 2 ,  3  and  4 , an image  32  of the vehicle in which the driver is located. 
     In a first variant, the image  32  is in the form for example of a solid line representing the outline of the vehicle viewed from the rear or from the front. Another shape more basic than the vehicle outline may of course be used, such as a square or a parallelepiped. It will be noted that it is also possible to represent the length of the vehicle by means of the image  32 . 
     A travel path  34  depicted in graphical form in the Figures, extending along the roadway  20 , in the direction of the vehicle image  32 , is shown in the bottom area of the display  16 . The width b of the travel path  34  corresponds to the width of the vehicle image  32  in the plane of the respective image (taking into account the width of the wheels). By reason of the perspective representation, the width b becomes narrower in relation to the location of the plane of the associated image. The distance a, shown in  FIG. 2 , from the bottom edge of the display image to the bottom edge of the vehicle image  32  corresponds to the distance of the vehicle in relation to the restricted gap  30 . 
     On the image of the environment recorded by the camera  12 , shown in  FIGS. 2 ,  3  and  4 , the restricted gap  30  is situated in front of the vehicle in the direction of travel. The travel path  34  therefore also extends in a straight line in the direction of travel. The lines  17  are not shown on the display  16  in  FIG. 2 . In the case where the lines  17  emitted by the light sources  15  are shown on the display  16 , these lines  17  will delimit the travel path  34  in the situation represented by the display  16 . If the restricted gap  30  in the roadway  20  is not located in a straight line in the direction of travel ahead of the vehicle, the lines  17  will not overlie the lines of delimitation of the travel path  34 , but will present another direction. 
     It is also possible to represent trajectories  35  corresponding to the steering angle of the wheels as shown in  FIG. 3  as a solid bold line. These trajectories  35  are represented by lines depicting the path of the wheels projected as far as the restricted gap  30 . The fact of showing the wheel trajectories enables a driver to park more easily, for example, when he wishes to maintain a distance between vehicles, or to drive more easily on a winding road. The driver is thus able detect and avoid obstacles on the wheel trajectory or to work out an overlap. It will be noted that the wheel trajectories are not necessarily parallel to the travel path  34 . 
     It will be noted that the trajectories  35  can be adjusted by taking into account the steering angle. The latter is given for example by a sensor and computed for example relative to the vertical axis of the vehicle. At this moment, it is referred to as the yaw angle. The lines representing the trajectories  35  may therefore be curved lines rather than straight lines. 
     The trajectories  35  can be divided into two types, one for the front wheels, and one for the rear wheels. This makes it possible to take account of the turning radius which is different for these two types of wheels. 
     The vehicle image  32  shown in  FIG. 2  or  3  can be repositioned and its size adjusted on the display  16  using the manually-operated adjustment means  18 . Repositioning can be effected continuously or gradually in a series of steps. Thus, it is possible to move the vehicle image  32  to the position of the restricted gap  30  in the roadway  20  and to adjust the dimensional scale so that the dimensional scale of the image  32  matches that of the restricted gap  30  shown and is located in its image plane. 
     To assist the driver to reposition the vehicle image  32  on the travel path  34 , use may also be made of placement aids such as vertical and horizontal lines  36  extending on either side of the vehicle image  32 , as shown in  FIG. 3  as bold dotted lines. 
       FIG. 4  shows a combination of three different dimensional scales of the images  32 , which are located in three different image planes. The largest vehicle image  32 ′ shown is located in the image plane as the vehicle enters the underpass. The middle-sized vehicle image  32 ″ shown corresponds to the dimensional scale of the vehicle inside the underpass. The third and smallest representation of the vehicle image  32 ′″ corresponds to the dimensional scale of the vehicle as it is leaving the underpass and is located in the associated image plane. 
     It will be noted that the position of the restricted gap  30  through which the driver wishes to pass is preferably fixed in the display  16 . Thus, according to whether the vehicle is moving forward or reversing in the direction of the restricted gap  30 , the image  32 ,  32 ′,  32 ″ of the vehicle adapts to the image of the restricted gap  30 , and the latter does not move on the display  16 . 
     It will be further noted that the size of the vehicle image  32  can be adapted in relation of a projection distance d 2  and the speed of the vehicle Vit. Thus, the travel path  34  is set at the precise initial distance a between the vehicle and the restricted gap  30  in the roadway  20 . Taking into account the speed of the vehicle Vit, and multiplying it by the travel time T, a travel distance d 1  and a projection distance d 2  equal to the initial distance a less the distance d 1  is obtained. The vehicle image  32  is thus re-sized so that it increases in size as the vehicle approaches the restricted gap  30  in the roadway  20 . A correspondence is thus established between the size of the vehicle image  32  and the projection distance d 2 , the projection distance being the distance between the front of the vehicle and the image  32 . Such a correspondence between different sizes of the image  32  and different values of the projection distance d 2  can be stored in memory in the vehicle. 
     It will also be noted that it is possible to set the projection distance d 2 , either to a minimum and/or to a maximum, for example at the factory. 
     In a second non-limitative variant of this first embodiment, the display  16  shows, as illustrated in  FIG. 5 , an aerial view image  32  of the vehicle in which the driver is located, together with its environment. This type of display  16  is referred to as a “bird&#39;s eye view” and is described in a non-limitative example in the document “Improvement of driving safety using a virtual driver—F. Holzmann, et al—Daimler Chrysler AG, Truck Product Creation—Ecole Polytechnique de Lausanne—Technical University of Munich”, and in particular in Section IV A and B. Such a display  16  makes it possible to check the length/width of the vehicle relative to a restricted gap  30 , such as for example a parking space, or may be used simply to show oncoming or cross traffic, and to check that the vehicle does not overshoot the road at a junction, as illustrated in  FIG. 5 . This type of view is thus also suited in particular to warning the driver of dangers arising at the side of the vehicle. For example, if the driver&#39;s maneuvering strategy is inappropriate for entering a parking space, a warning signal can be displayed such as for example a red indicator on the side of the vehicle where there may be a danger. 
     Other types of view can of course be used, such as a 3D view of the vehicle. 
     Consequently, comparison of the vehicle image  32  with the internal width of the restricted gap  30  shown in the corresponding image plane makes it possible to determine whether the vehicle is able to pass through the restricted gap  30  without damage. The driver can make this comparison in particular by observing the vehicle image  32  and the restricted gap  30  on the display  16 . 
     In a second more perfected embodiment, this comparison can be performed automatically by means of the evaluation unit  14 , by the image analysis means  14   a  which detect the restricted gap  30 , and by the comparison means  14   b . Appropriate processing of the image makes it possible to compute the inside width of the restricted gap  30  and to compare the vehicle image  32  with the respective image plane. In another variant, the comparison is made by positioning both respective images  32  of the vehicle and the restricted gap  30  in the same plane to make the comparison (by adjusting for example the position and the plane of the vehicle image  32  and by moving it to the location of the restricted gap  30 ). 
     In this case, the comparison is not made by the driver. 
     The display  16  need not therefore display either the image  32  of the vehicle or the image of the restricted gap  30 . A visual signal can be generated on the display  16  to tell the driver if he can pass through without damage. Also, the display  16  need not be active. At this time, another interface can be used such as an audible and/or tactile interface (not shown) to tell the driver if he can pass through without damage. It is thus perfectly possible to have a camera  12  including video sensors without having a visual interface. 
     Of course, a third embodiment can be provided wherein the comparison is automatic, while the display  16  still shows the vehicle image  32 , the restricted gap  30  and the environment. This is performed by virtue of the automatic adjustment unit of the comparison means  14   b  which makes is possible to adjust the position and the plane of a vehicle image  32  on the display  16  and to move the vehicle image  32  to the location of the restricted gap  30 . 
     Thus, if it is determined (visually by the driver and/or by the emission of an optical and/or audible signal and/or tactile signal) that the vehicle can pass through the restricted gap  30  without damage, the driver can concentrate on what is happening ahead and drive in an appropriate manner through the restricted gap  30 . 
     It will be noted that this is facilitated by the lines  17  in that the driver is informed as to whether the direction of travel he has taken is correct in order to pass through the restricted gap  30  without damage. He is therefore able to concentrate on what is happening in front of the vehicle, taking account of the lines  17 , and turn his attention away from the display  16 . The lines  17  therefore help the driver to pass through the restricted gap  30  without damage. The light sources  15  can in particular emit a colored light which stands out from the environment and is dearly visible to the driver. Similarly, the lines  17  can be shown in color on the display  16 . 
     In the case where it is not possible to pass through the restricted gap  30  without damage, a warning signal can be also given to the driver. The warning signal given to the driver in case of overlap can be optical, audible or tactile. For example, an acoustic signal can be emitted or warning symbols can appear on the display  16 , such as “proceed”, “proceed slowly”, “do not proceed”, etc. Other driver assistance systems can also be activated, in particular automatic braking of the vehicle can be initiated in case of imminent collision. 
     It is also possible that other driver assistance systems, to activate forced turning and/or forced braking for example, can be linked to the warning signal. 
     It will be noted that, in a general manner, in order to determine the vehicle image  32  (whether or not it is shown on the display  16 ), the parameter used is the vehicle model which makes it possible to have the exact dimensions of the vehicle. Thus, the vehicle model is stored in memory in the vehicle, either at the factory or retrofitted. 
     In addition, parameters such as for example the width of the doors or the length of the tailgate can also be used to determine, in particular when the vehicle is stationary, whether it is possible to open the doors or tailgate when the vehicle is positioned in a restricted gap  30  in the roadway  20  such as a parking space. The vehicle model can be recorded at the factory or retrofitted. 
     Other parameters can also be taken into account such as the presence of bicycles on the roof or a detachable roof rack. These parameters can be stored in memory, at the initiative of the vehicle user, via a suitable interface (for example on startup of the driver assistance system  10 ), or automatically by means of presence sensors for example. 
     In a non-limitative embodiment, the driver assistance system  10  can cooperate with an obstacle detection system  40  such as that illustrated in  FIG. 1 . This obstacle detection system  40  serves to determine whether there is an obstacle on the travel path  34 , i.e. between the vehicle and the restricted gap  30 , and the nature of the obstacle (vehicle, motorcycle, etc.) and whether the obstacle is moving or stationary. Such a system is based for example on one or more sensors (vision, radar, ultrasound, laser etc.) well known to the person skilled in the art, and/or on the combination of data generated by these sensors. A non-limitative example of an obstacle detection system  40  using a radar sensor is described in the document “Object classification with automotive radar—F. Kruse, F. Folster, M. Ahrholdt, M M. Meinecke, H. Rohling—Technical University of Hamburg-Harburg, Dpt of Telecommunications—Volkswagen AG, Research Electronic Systems”. Another non-limitative example of an obstacle detection system  40  using another type of sensor is described in the document “Vehicle Detection and Compass Applications using AMR Magnetic Sensors—M J. Caruso, L S. Withanawasam—Honeywell, SSEC” and in particular in the sections on AMR Sensor Applications and Vehicle Classification. 
     The obstacle detection system is either automatic or semi-automatic. In the latter case, a suitable interface enables the vehicle user to define the obstacle himself. 
     Thus if such an obstacle, such as a car for example, is present in the travel path  34 , a signal is emitted (audible, visual, etc.) to warn the driver not to proceed. 
     In a non-limitative embodiment, the driver assistance system  10  can also cooperate with on-board systems  50  in the vehicle, such as side mirror controls, so as to automatically control these systems. For example, if the driver wishes to park in a narrow parking space, the driver assistance system  10  detects that the space is too narrow and can emit a warning signal as seen previously, but can also automatically fold away a side mirror if this is sufficient to enter the parking space. The same applies to the obstacle detection system  40  which can also cooperate with on-board systems  50 . 
     These automatic controls can be an option to be activated by the driver via a suitable interface. It is also possible to apply this automatic control to the doors or tailgate of the vehicle, or to gradual actuation of the brake pedal or automatic parking systems. 
     Thus, the driver assistance system  10  can be used in the case where the vehicle is moving (in forward or reverse, on the road or when the driver wishes to park in a parking space for example), and also in the case where the vehicle is stationary (for example when a user of the vehicle wishes to open a door). It thus makes it possible to avoid accidents and damage to the vehicle, and also serves to assist the driver in correctly maneuvering his vehicle. 
     While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.