Abstract:
A method for monitoring the blind spot at the side of a motor vehicle, a warning function being activated which gives out a warning to the driver if an object is located in a warning region, includes the following steps: a) determining the relative speed between the object and the motor vehicle, determining the travel direction of the object relative to the motor vehicle, and determining the position of the object relative to the motor vehicle within a sensor region; and b) giving out a warning to the driver if the travel direction of the object corresponds to that of the motor vehicle, the relative speed between the object and the motor vehicle is within a predetermined range, defined by a lower range boundary and an upper range boundary, the predetermined region including the relative speed zero, and the position of the object being within the warning region.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a method and a device for monitoring blind spots of a motor vehicle. 
   BACKGROUND INFORMATION 
   A driver of a vehicle is able directly to examine the region around his vehicle through the vehicle&#39;s windows, and indirectly through the vehicle&#39;s rear view mirrors. In this context, the driver is able to examine through the vehicle&#39;s windows predominantly the region in front of the vehicle and at the sides of the vehicle, whereas the region behind the vehicle may be examined using the vehicle&#39;s inside rearview mirror, and the regions laterally behind the vehicle may be examined using one or more of the vehicle&#39;s outer rearview mirrors. 
   Because of the restricted field of view of the driver and the geometrical relationships in a vehicle, that is, for example, because of posts between the vehicle&#39;s windows that hinder vision, it is generally not possible for the driver of the vehicle to examine all the regions around a vehicle without turning around or turning the head. Directly behind and in front of the vehicle there are regions that the driver is not able to examine. Similarly, there are regions at the side of the vehicle that the driver is not able to examine without a considerable change in the field of vision by turning his head. These difficult-to-examine regions at the sides of the vehicle are designated as blind spot regions of the vehicle, this region varying depending on the size and sitting position of the driver as well as with the kind and the setting of the outside mirrors. 
   European Published Patent Application No. 1 026 522 describes a system for monitoring a region at the side of a vehicle in a dynamic traffic environment. In this context, the system has an IR transmitting unit and an IR receiving unit which are situated at the side of the vehicle. These IR transmitting and receiving units define a lateral region that is to be monitored, an evaluating unit establishing whether an object is located in the monitoring region. The presence of an object in the monitored region is notified to the driver via a suitable display unit. A disadvantage is that object may be pointed out to the driver that are meaningless for the guidance of the vehicle. 
   SUMMARY 
   In a method and a device for monitoring blind spots of a motor vehicle according to example embodiments of the present invention, the driver may only receive a warning if the object detected in the blind spot has a meaning with respect to the guidance of the vehicle. 
   The method, according to an example embodiment of the present invention, for monitoring the blind spot at the side of a motor vehicle, that activates a warning function for giving off a warning to the driver if an object is located in a predefined warning range, has the following steps: a) determining the relative speed v rel  between an object and a motor vehicle, determining the travel direction of the object relative to the motor vehicle and determining the position of the object relative to the motor vehicle within a predefined sensor range; and b) giving out a warning to the driver if the travel direction of the object corresponds to that of the motor vehicle, the relative speed v rel  between the object and the vehicle is within a predetermined range, defined by a lower range boundary v u  and an upper range boundary v o , the predetermined range of the relative speed including zero, and the position of the object (F 2 ) being within the warning range. 
   In this context, the relative speed is with reference to the motor vehicle, e.g., if the relative speed is greater than zero, the object moves faster than the vehicle, and if the relative speed is less than zero, the object is slower than the vehicle, or two-way traffic is involved. Objects may be, for example, pedestrians, vehicles, bicycles, motorcycles, trucks, buses, etc. Furthermore, the travel direction of the object relative to the motor vehicle is defined by the direction of the roadway on which the object is moving relative to the vehicle. In other words, with respect to the motor vehicle, an object is able to have only one of two travel directions, either it moves in the same travel direction as the vehicle or it moves in the opposite travel direction. In the latter case, then, two-way traffic is involved. As a result, an object that has the relative speed of zero with respect to the vehicle, and changes from an outer lane to a lane adjacent to the vehicle, has the same travel direction as the vehicle, although, with respect to the relative speed, it moves in a perpendicular direction toward the vehicle. Furthermore, the sensor range is predefined by the range of the sensor at which it detects objects, and the warning range is the range within which a warning is given off to the driver, e.g., the blind spot region. In this context, the warning range is a part of the sensor range. 
   A warning may also be generated at relative speeds greater than the positive upper range boundary v o , i.e., in an example embodiment a warning is generated in response to all positive relative speeds, if the additional, above-named conditions are satisfied. 
   For example, the predetermined range is defined by the interval of the relative speeds of −30 km/h to +100 km/h, e.g., −15 km/h to +50 km/h, and, e.g., −5 km/h to +30 km/h. This has the background that an object approaching at high speed covers a greater path per unit of time, and consequently has to be monitored already at a greater distance. Example embodiments of the present invention may thus ensure that a driving situation or a warning situation is not only judged based on the fact as to whether an object is located in a static warning range or at a distance or a static warning range or distance that depends on a speed or a driving parameter, but rather, the individual characteristics of the approaching object (such as the speed, the angle, etc. (see  FIG. 8 )) may be incorporated in the judgment, depending on the situation. For the warning function, therefore, for giving out a warning, the distance and the relative speed as well as possibly, in addition, the angular information (see above) are relevant for each recorded object. 
   In an example embodiment, the range boundaries are a function of the speed of the motor vehicle, e.g., at a low speed of the vehicle, the range boundaries are lowered, whereas at a high speed, the range boundaries are shifted to higher relative speeds. 
   The warning function may be independent of the direction of entry of the object into the blind spot, and the direction of exit of the object from the blind spot. Furthermore, the warning function may be independent of the background of the object that enters the blind spot, and independent of standing objects, of their alignment and their background. In an example embodiment, driving situations are classified, each classified driving situation including the information as to whether the warning function is activated or not, when an object enters the blind spot region. The method may also have the following steps: determining the current driving situation of the motor vehicle and the object, ascertaining that classified driving situation which corresponds to the current driving situation, and activating the warning function corresponding to the information of the ascertained classified driving situation. 
   The classification may take into account two additional lanes laterally to the lane of the motor vehicle. This measure is usually sufficient. 
   For example, the evaluation of whether a warning function is triggered in response to the entry of an object into a blind spot or warning range of the motor vehicle, is carried out at both sides of the vehicle, e.g., both sides of the motor vehicle are monitored, in order for the monitoring to cover swinging-in procedures as well as passing procedures or lane change in general. 
   Because an angle is recorded or calculated as an input variable for the warning function in the driving plane of the motor vehicle, which may result from the driving direction of the motor vehicle (F 1 ) and the straight line constructed between a sensor device for monitoring a warning range and the object, additional insights may be obtained for judging the driving situation. If an object is recorded in the warning range (e.g., radial distance undershoots warning threshold), using the additional information on the angle described, a statement may be made as to whether the object is located in an adjacent lane or in a third lane that may be present. If the object is in a third lane, no warning may be required, since swinging out into the middle lane is possible without danger. 
   A device according to an example embodiment of the present invention for carrying out the method explained above includes a sensor device for monitoring a blind spot, the sensor device determining the direction of motion of an object relative to the motor vehicle, the relative speed between the object and the motor vehicle, as well as the position of the object relative to the vehicle, a control unit for valuing the data ascertained, and a warning device for giving out a warning signal to the driver of the motor vehicle as a function of the valuing of the data. The position of the detected object relative to the vehicle may be determined by measuring the radial distance from the vehicle and measuring the angle at which the object is approaching. 
   For example, the control device includes a memory for storing classified driving conditions and a comparator for comparing a current driving condition ascertained by the control unit from the data of the sensor device to the classified driving conditions. 
   The sensor device may be situated in a side mirror, an outer mirror, the rear bumper or a rear light of the motor vehicle, etc. 
   Example embodiments of the present invention are explained below with reference to the appended Figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a blind spot of a motor vehicle. 
       FIGS. 2   a  to  2   c  schematically illustrate warning situations in response to selected driving situation. 
       FIGS. 3   a  to  3   c  schematically illustrates situations without activation of the warning function. 
       FIG. 4  schematically illustrates a preferred speed range. 
       FIGS. 5   a  to  5   d  schematically illustrate possible entry directions and exit directions into and out of a blind spot for vehicles in the same driving direction and for two-way traffic. 
       FIGS. 6   a  to  6   c  schematically illustrate examples of classified driving situations having triggering of a warning signal. 
       FIGS. 7   a  to  7   c  schematically illustrate examples of classified driving situations without triggering of a warning signal. 
       FIG. 8  is a schematic view of a device for monitoring blind spots. 
       FIG. 9  schematically illustrates a possible definition of an angle between the motor vehicle and an object. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a schematic view of so-called blind spots on each side of a motor vehicle. What is shown is a motor vehicle F 1  which is traveling from right to left in the drawing, in the middle lane S 2  of a roadway FB having three lanes S 1 , S 2 , S 3 . Both on the driver&#39;s side and on the passenger&#39;s side, in each case a rectangular region W 1 , W 2  is illustrated, having edges a, b which define, for example, a rectangle of approximately 5 m×5 m. These approximate regions W 1 , W 2  are defined below as blind spot regions or warning regions, which are not able to be examined by the driver in the outside mirrors. The regions depend on the size and the sitting position of the driver, as well as on the type and the setting of the outside mirrors, as well as on the construction of the vehicle itself. 
   Furthermore, the size of the blind spot regions depends on the driving situation, such as the speed. 
   In the following  FIGS. 2   a  to  2   c ,  3   a  to  3   c ,  5   a  to  5   d ,  6   a  to  6   c ,  7   a  to  7   c  and  8   a  to  8   c , that vehicle into whose driver-side blind spot an object is entering, is designated as vehicle F 1 , and the object is specified by an additional vehicle F 2 , which is denoted as the object vehicle. The direction of motion of vehicle F 1 , whose blind spot is being considered, is from right to left in the plane of the drawings. 
     FIG. 2   a  illustrates a passing procedure, in which two vehicles F 1  and F 2  have the same travel direction FR, and vehicle F 1  is being slowly passed by faster object vehicle F 2 . Because of the penetration of object vehicle F 2  into the driver&#39;s side blind spot region W 1  of vehicle F 1 , a warning is triggered. 
     FIG. 2   b  illustrates a situation comparable to that illustrated in  FIG. 2   a , in which object vehicle F 2 , located in blind spot region W 1  of vehicle F 1 , has the same speed as vehicle F 1 . A warning to the driver of vehicle F 1  takes place. 
     FIG. 2   c  illustrates a situation in which object vehicle F 2  slowly drops back compared to vehicle F 1 , which is indicated by the arrow directed rearwardly, and wanders through the blind spot of vehicle F 1 . A warning to the driver of vehicle F 1  takes place. Travel direction FR of the two vehicles F 1 , F 2  is identical. 
   Additional situations, such as those illustrated in  FIGS. 3   a  to  3   c , in which a warning function is triggered by the penetration of an object into a blind spot of a vehicle, may be defined both for the driver&#39;s side and, analogously, for the passenger&#39;s side. 
     FIG. 3   a  illustrates a situation in which object vehicle F 2  enters the driver&#39;s side blind spot W 1  of vehicle F 1  as two-way traffic. In principle, in the case of two-way traffic, no warning may be given. The perception of an object as constituting two-way traffic takes place, for example, by the detection of a negative relative speed V rel  and, judging by the number, high relative speed V rel  (V rel ≦v u , see  FIG. 4 ). 
     FIG. 3   b  illustrates the passing of vehicle F 1  of standing vehicle F 2 . Here, too, there is no warning in response to an entry of a standing vehicle into the blind spot region of another vehicle. The perception of an object as a standing object takes place, for example, by the detected relative speed V rel , which is equal to the characteristic speed V F1  of vehicle F 1 . 
     FIG. 3   c  illustrates a situation in which both vehicles move in the same travel direction FR, and object vehicle F 2  drops back rapidly with respect to vehicle F 1  that is moving in the same direction, which is indicated by the bigger directional arrow illustrated pointing to the right in the drawing. In other words, object vehicle F 2  travels through blind spot region W 1  of vehicle F 1  from front to back, and the situation may be described as a passing procedure of vehicle  1 . No warning takes place in this situation. Relative speed V rel  of object vehicle F 2 , detected by vehicle F 1 , is negative in this context (V rel ≦V u ,  FIG. 4 ). However, inasmuch as the object vehicle drops back slowly (V u ≦V rel ≦0,  FIG. 4 ) no warning takes place. 
   Furthermore, no warning takes place if the blind spot region of a vehicle is empty independently of the background. 
     FIG. 4  illustrates in an illustrated representation the ranges of relative speeds V rel  in which, in response to entry of an object into the blind spot region of a vehicle, a warning takes place or not. In this context, relative speed v rel  is referred to the vehicle, so as to arrive at a correct sign definition. In the case of relative speeds lower than a lower boundary v u  between the vehicle and an object, no warning is triggered, in the case of relative speeds V rel  within a range between the lower boundary v u  and an upper boundary v o , this range including relative speed zero, a warning is triggered, and in the case of relative speeds greater than upper boundary v o , the triggering of a warning is optional. The range boundaries named may be functions of characteristic speed V F1  and of driving parameters (e.g., acceleration procedure, highway travel and expressway travel) of vehicle F 1 . 
     FIGS. 5   a  to  5   d  illustrate possible entry and exit directions in a blind spot of a vehicle for vehicles going in the same travel direction FR and for two-way traffic. The directions used with respect to the possible entry and exit direction, “right”, “left”, “front” and “rear” relate to the direction of motion of object vehicle F 2 . 
     FIG. 5   a  schematically illustrates six possible entry directions, indicated by arrows  1 . 1 ,  1 . 2 ,  1 . 3 ,  1 . 4 ,  1 . 5  and  1 . 6 , in which vehicle F 2  may enter the driver&#39;s side blind spot region W 1  of vehicle F 1 . Also illustrated are three lanes S 1 , S 2 , S 3  of a roadway FB. The arrows have the following meaning:
       1 . 1  Entry direction at an angle left forward by change of vehicle F 2  from lane S 1  to lane S 2  (relative speed greater than zero),     1 . 2  Entry direction forward by vehicle F 2  remaining in lane S 2  (relative speed greater than zero),     1 . 3  Entry direction at an angle right forward by change of vehicle F 2  from lane S 3  to lane S 2  (relative speed greater than zero),     1 . 4  Entry direction to the right by change of vehicle F 2  from lane S 3  to lane S 2  (relative speed equal to zero),     1 . 5  Entry direction at an angle right rearward by change of vehicle F 2  from lane S 3  to lane S 2  (relative speed less than zero), and     1 . 6  Entry direction rearward by vehicle F 2  remaining in lane S 2  (relative speed less than zero).   
     FIG. 5   b  schematically illustrates six possible exit directions, indicated by arrows  2 . 1 ,  2 . 2 ,  2 . 3 ,  2 . 4 ,  2 . 5  and  2 . 6 , in which vehicle F 2  may exit the driver&#39;s side blind spot region W 1  of vehicle F 1 . The arrows have the following meaning:
       2 . 1  Exit direction at an angle right rearward by change of vehicle F 2  from lane S 2  to lane S 1  (relative speed less than zero),     2 . 2  Exit direction rearward by vehicle F 2  remaining in lane S 2  (relative speed less than zero),     2 . 3  Exit direction at an angle right rearward by change of vehicle F 2  from lane S 2  to lane S 3  (relative speed less than zero),     2 . 4  Exit direction at an angle left by change of vehicle F 2  from lane S 2  to lane S 3  (relative speed equal to zero),     2 . 5  Exit direction at an angle left forward by change of vehicle F 2  from lane S 3  to lane S 2  (relative speed greater than zero), and     2 . 6  Exit direction forward by vehicle F 2  remaining in lane S 2  (relative speed greater than zero).   
     FIG. 5   c  schematically illustrates two possible entry directions, indicated by arrows  3 . 1  and  3 . 2 , in which vehicle F 2  may enter the driver&#39;s side blind spot region W 1  of vehicle F 1  as two-way traffic. The arrows have the following meaning:
       3 . 1  Entry direction at an angle left forward by change of vehicle F 2 , that is traveling in the opposite direction to the traffic, from lane S 3  to lane S 2 , and     3 . 2  Entry direction forward by vehicle F 2  remaining in lane S 2 .   
     FIG. 5   d  schematically illustrates three possible exit directions, indicated by arrows  4 . 1 ,  4 . 2  and  4 . 3 , in which vehicle F 2  may exit the driver&#39;s side blind spot region W 1  of vehicle F 1 . The arrows have the following meaning:
       4 . 1  Exit direction at an angle left forward by change of vehicle F 2 , that is traveling in the opposite direction to the traffic, from lane S 2  to lane S 1 ,     4 . 2  Exit direction forward by vehicle F 2 , that is traveling in the opposite direction to the traffic, remaining in lane S 2 , and     4 . 3  Exit direction at an angle left forward by change of vehicle F 2 , that is traveling in the opposite direction to the traffic, from lane S 2  to lane S 3 .   
   The above-named possible entry and exit directions into a blind spot of a vehicle for vehicles going in the same travel direction and for two-way traffic  1 . 1  to  1 . 6 ,  2 . 1  to  2 . 6 ,  3 . 1  to  3 . 2  and  4 . 1  to  4 . 3  are used to define the columns of a matrix that describes classified blind spot situations of the driver&#39;s side. The rows of the matrix are defined by background objects, such as “no objects”, “moving objects”, which are subdivided into “passing”, “same speed”, “dropping back” and “two-way traffic”; and “static objects”, such as “pylons”, “delineators”, “trees”, “traffic jam”, “guardrail” and “tunnel wall”. For every possible classified blind spot situation of the matrix it is stated whether a warning is to be given out in response to the occurrence of the situation. 
     FIGS. 6   a  to  6   c  illustrate three examples of a plurality of possible classified driving situations that have triggering of a warning signal which, in parameterized form, are components of the matrix explained above. 
     FIG. 6   a  illustrates vehicle F 1  moving in lane S 1 , along with object vehicle F 2  traveling behind it, which changes in direction  1 . 1  to lane S 2 , and thereby arrives in blind spot region W 1  of vehicle F 1 . Since the travel directions of the vehicles are identical, the relative speed is greater than zero (and is located within the predefined range v u  to v o ) and the position P of the object is within the warning range, a warning is triggered. The object vehicle leaves the blind spot region of vehicle F 1  again in direction  2 . 6 . 
     FIG. 6   b  illustrates vehicle F 1  moving in lane S 1 . In lane S 2  parallel to it, object vehicle F 2  approaches from behind in direction  1 . 2 , and enters blind spot region W 1  of vehicle F 1 . Since the travel directions of the vehicles are identical, the relative speed V rel  is greater than zero (and is located within the predefined range v u  to v o ) and the position of the object is within the warning range, a warning is triggered. The object vehicle leaves the blind spot region of vehicle F 1  again in direction  2 . 6 . 
     FIG. 6   c  illustrates vehicle F 1  moving in lane S 1 . Because of a change of object vehicle F 2  in direction  1 . 3  to lane S 3 , it arrives in blind spot region W 1  of vehicle F 1 . Since the travel directions FR of the vehicles are identical, the relative speed is greater than zero (and is located within the predefined range v u  to v o ) and the object is located within the warning range, a warning is triggered. The object vehicle leaves the blind spot region of vehicle F 1  again in direction  2 . 6 . 
     FIGS. 7   a  to  7   c  illustrate three examples of a plurality of possible classified driving situations without the triggering of a warning signal. 
     FIG. 7   a  illustrates vehicle F 1  having blind spot region W 1 , which is moving in lane S 1  in predefined travel direction (i.e., in the plane of the drawing, from right to left). In lane S 2 , object vehicle F 2  moves in opposite travel direction  3 . 2 , and enters blind spot region W 1  of vehicle F 1 . No warning is triggered. The object vehicle leaves the blind spot region again in direction  4 . 1 , that is, while changing lanes to lane S 1 . In lane S 3 , an additional vehicle F 3  is moving in opposite travel direction FR to vehicle F 1 . This vehicle is insignificant for the triggering of a warning, since it does not enter blind spot region W 1 . 
     FIG. 7   b  illustrates vehicle F 1  having blind spot region W 1 , which is moving in lane S 1  in predefined travel direction FR (i.e., in the plane of the drawing, from right to left). In lane S 2 , object vehicle F 2  moves in opposite travel direction, in direction  3 . 2 , and enters blind spot region W 1  of vehicle F 1 . No warning is triggered. The object vehicle leaves the blind spot region again in direction  4 . 2 , i.e., it remains in lane S 2 . An additional vehicle F 3  moves in lane S 3  in the opposite travel direction FR to vehicle F 1 . This vehicle is insignificant for the triggering of a warning, since it does not enter blind spot region W 1 . 
     FIG. 7   c  illustrates vehicle F 1  having blind spot region W 1 , which is moving in lane S 1  in predefined travel direction FR (i.e., in the plane of the drawing, from right to left). In lane S 2 , object vehicle F 2  moves in opposite travel direction FR in direction  3 . 2 , and enters blind spot region W 1  of vehicle F 1 . No warning is triggered. The object vehicle leaves the blind spot region again in direction  4 . 1 , i.e., it changes to lane S 1 . In lane S 3  there is a traffic jam having vehicles F 3 , or there are parking vehicles. These vehicles F 3  are insignificant for the triggering of a warning, since they are standing, and, as a result, are treated as background. 
     FIG. 8  schematically illustrates a device for monitoring blind spots. A computing device R receives different data about at least one object F 2  and/or about one&#39;s own driving situation. In this context, the information on object F 2  may be made available by a sensor. It is also possible that information about position P of fixed objects are made available by a memory device (such as a navigation unit). Making available data of a position P for computing device R is illustrated in  FIG. 8  as a broken line arrow. The ascertainment and notification of a travel direction FR may also be made available by a travel direction ascertaining (such as a navigation unit). Optional information branch P is indicated as a broken line in  FIG. 8 . 
   Travel direction determination FRB ascertains travel direction FR from relative speed V rel  to a recorded object. In this context, the curve of relative speed over time may also be drawn upon. Thus, travel direction FR of an object F 2  that is passing in a lane S 2 , S 3 , (V rel &gt;0), which drops back again after the passing procedure (V rel &lt;0), is evaluated as the same travel direction overall. 
   Relative speed V rel , distance d and angle α between motor vehicle F 1  and object F 2  (see  FIG. 9 ) are supplied to computing device R. As additional information, characteristic speed V F1  and signal are available to computing device R via an operation of the left or right blinker BL, BR. Additional information on the driving situation, such as acceleration value, the steering angle of motor vehicle F 1  may be a part of the data supplied to computing unit R. A warning function warns the driver in an information stage I or in a warning stage W 1  according to the following scheme: 
   If a vehicle is recorded in the warning region, this is signaled to the vehicle operator. An intense or urgent warning takes place as soon as the vehicle operator indicates a lane change in this situation by operating a blinker. In this context, the signaling to the vehicle operator may be performed optically and/or acoustically and/or haptically. 
   To the extent that additional regions next to motor vehicle F 1  are monitored by an additional sensor, additional inputs are correspondingly provided at computing device R. 
     FIG. 9  illustrates a possible definition of an angle α, which is recorded as an input variable for the warning function between motor vehicle F 1  and an object F 2 . In this connection, the angle is defined in the travel plane by the travel direction and the straight line that comes about between a sensor device and object F 2  that is to be monitored. How the straight line, and ultimately angle α are exactly defined, in this context (end point at object F 2 , in the middle at vehicle beginning or at the object center of gravity, or at an object point having the least clearance distance, etc), is immaterial if the corresponding circumstances find consideration for a certain and reliable warning function in computing device R or in the sensor or other control units. 
   REFERENCE NUMERAL LIST 
   
       
       F 1  vehicle 
       F 2  vehicle 
       F 3  vehicle 
       FB roadway 
       W 1  blind spot driver&#39;s side 
       W 2  blind spot passenger&#39;s side 
       S 1  lane 
       S 2  lane 
       S 3  lane 
       FR travel direction 
       P position 
       FRB travel direction determination 
       I information stage 
       W warning stage 
       SP memory 
       BL blinker signal left 
       BR blinker signal right 
       R computing unit 
       α angle 
       V F1  initial speed 
       d distance 
       a edge length 
       b edge length 
         1 . 1 - 1 . 6  entry directions 
         2 . 1 - 2 . 6  exit directions 
         3 . 1 - 3 . 2  entry directions 
         4 . 1 - 4 . 3  exit directions 
       v rel  relative speed 
       v o  upper boundary 
       v u  lower boundary