Abstract:
A driver assistance system for motor vehicles, having a velocity regulation function for regulating the velocity of the subject vehicle to a nominal velocity, and having an adjacent-lane monitoring function, characterized by a turning assistance function which, when the velocity regulation function is active and an incoming signal indicates an imminent turning process that requires crossing an adjacent lane, monitors the traffic in the adjacent lane with the aid of the adjacent-lane monitoring function, and, as a function of locations and velocities of traffic participants in the adjacent lane, determines a spatial and temporal window for moving into the adjacent lane and adapts the nominal velocity to this window.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a driver assistance system for motor vehicles, having a velocity regulation function for regulating the velocity of one&#39;s own vehicle to a nominal velocity, and having an adjacent-lane monitoring function. 
     BACKGROUND INFORMATION 
     Motor vehicles frequently come equipped with electronic driver assistance systems that provide the driver with vehicle guidance support. What are generally referred to as ACC systems (adaptive cruise control) are known, for example, that are used for regulating the velocity of one&#39;s own vehicle. During free travel of the vehicle, when there is no vehicle in front in one&#39;s own lane, the nominal velocity is a driver-specified velocity. If, on the other hand, a vehicle driving ahead is followed, then the distance thereto is measured using a radar sensor installed in the vehicle, for example, and one&#39;s own velocity is adapted to ensure that the vehicle driving ahead is followed at an appropriate collision-avoidance distance. 
     While the radar sensor of the ACC system typically only monitors the space in front of the subject vehicle, sensors, such as ultrasonic sensors, or laterally and/or rearwardly directed radar sensors are also known that are able to monitor the traffic in adjacent lanes as well. As a further driver assistance function, such sensor systems then make possible what is generally referred to as blind-spot detection (BSD), thus monitoring the blind spot laterally behind the subject vehicle. This function is enhanced by what is generally referred to as a lane change assist (LCA) function, which can be used to also record the distances and relative velocities of vehicles that are located in the adjacent lane behind the subject vehicle and are coming closer to the same. On the basis of these data, a warning can then be issued, for example, in the form of a visual warning signal that is superimposed into the exterior rearview mirror of the vehicle, for instance, when it is not safe to change into the adjacent lane. 
     Another known driver assistance function is a lane keeping support (LKS) which issues a warning to the driver or actively intervenes in the vehicle steering when the driver is unintentionally about to leave the lane driven in so far. The warning can be a haptic signal, for example, such as a steering wheel vibration generated by the power steering. Often, a video camera having an associated image evaluation system is provided for capturing the lane markings on the roadway. This system also serves to improve the identification of the lane traveled in by the subject vehicle in the case of multilane roadways. One&#39;s own lane can, in fact, also be indirectly inferred from the radar sensor signals if there is sufficient traffic density. However, a greater accuracy is provided by the use of a video system. 
     What is commonly known as a multifunction camera (MFC) is often provided as a video camera. It can be utilized for other assistance functions, as well. For example, such a camera can make it easier to classify objects that had been recognized by the radar systems, but, on the basis of the radar signals, were not able to be uniquely classified as passenger cars, trucks, two-wheeled vehicles, pedestrians or the like. In the same way, the multifunction camera makes it possible to visually recognize prohibition signs, in particular speed-limit signs. 
     Today, motor vehicles are also typically equipped with a navigation system. It makes possible automatic route planning on the basis of a stored electronic map. Moreover, by using a satellite-based position-finding system, for example, the navigation system identifies the location of the subject vehicle and is thus able to provide the driver with navigation information. Such navigation systems usually have their own data processing system that functions independently of the remaining assistance functions. However, the navigation system can communicate via suitable interfaces with other components of the driver assistance system, which is why it is likewise to be considered here as an integral part of the vehicle&#39;s driver assistance system. 
     SUMMARY 
     It is an object of the present invention to provide a driver assistance system having an additional assistance function that, in particular, will improve safety and ride comfort during turning processes. 
     This objective is achieved in accordance with the present invention by a turning assistance function which, in response to an incoming signal indicating an imminent turning process that requires crossing an adjacent lane, monitors the traffic in the adjacent lane with the aid of the adjacent-lane monitoring function, and, as a function of locations and velocities of traffic participants in the adjacent lane, determines a spatial and temporal window for moving into the adjacent lane and adapts the nominal velocity to this window. 
     This assistance function is helpful, for example, in situations where the subject vehicle is located in a middle or left lane of a multilane roadway, and the navigation system delivers the information that a right turn is to take place in a few hundred meters. The navigation system will then notify the driver visually and/or acoustically to give him/her the chance to get into the right adjacent lane in good time. A dangerous situation can arise when another vehicle is located in the blind spot in the adjacent lane, or when a vehicle is coming closer at a higher velocity in the adjacent lane, and the driver of the subject vehicle is not able to accurately assess the relative velocity. The known BSD and LCA systems are, in fact, able to warn the driver in such situations; however, it is then left to the driver to deactivate the velocity regulation function and to take over the longitudinal guidance of the vehicle himself/herself, for example, to reduce one&#39;s own velocity to the point where the subject vehicle drops back, behind the vehicle in the adjacent lane and is then able to slip safely into a gap in the adjacent lane. 
     The present invention makes it possible for the driver to be assisted by substantially automating the above described necessary actions of the driver. If at least one other vehicle is located adjacent to, in front of, or behind the subject vehicle in the adjacent lane, then a gap or a window is present in each case in front of and behind this vehicle that permits a safe moving into the adjacent lane in consideration of the necessary safety distances. The turning assistance function according to the present invention uses sensor technology that is already present for the adjacent-lane monitoring function, to identify such windows for turning into the adjacent lane; as the case may be, when a plurality of such windows are present, to select that window which makes it possible to safely move into the adjacent lane while changing the velocity of the subject vehicle to the least possible extent, and to then modify the nominal velocity for the velocity regulation function in a way that allows the subject vehicle to be moved next to this window. 
     Generally, the sensory components required for the turning assistance function in accordance with the present invention are already present because they are also needed for other assistance functions. The present invention may then be readily and cost-effectively implemented by appropriately programming the electronic data processing system that controls the remaining assistance functions (with the exception of the navigation system). 
     Analogously to the situation described above, driving situations are conceivable where the vehicle is traveling on a road having only one single lane for each direction of travel, or is already located in the rightmost lane, but a bicycle route, a pedestrian crosswalk, or a streetcar rail must be crossed for a turning process. For that reason, the term “adjacent lane” is to be understood in a general sense in this Application, and should also include traffic routes for other traffic participants, such as bicycle riders, pedestrians or rail vehicles. 
     Advantageous embodiments and refinements of the present invention are defined in the dependent claims. 
     In one advantageous specific embodiment, the signal that announces a turning process, comes from a route planning system of a navigation system. In principle, however, this signal may also have a different origin. For example, it could be manually input by the driver. If indicated, even the actuation of the turn indicator by the driver may serve to announce an imminent turning process and trigger the turning assistance function. 
     Adapting the nominal velocity does not necessarily signify a velocity reduction. In some cases, the most conveniently situated window for moving into the adjacent lane may also be reached by accelerating the subject vehicle, provided that existing speed limits are thereby considered. Therefore, on the basis of the data from the multifunction camera, or also the data supplied by the navigation system, the assistance function is adapted to automatically check whether there is a speed limit, and to take this information into account when selecting the most favorable window. 
     The windows for moving into the adjacent lane each have a front and/or a rear boundary. These boundaries are determined by the positions of the vehicles in the adjacent lane, as well as by the safety distances to be observed relative to these vehicles. It is understood that these boundaries are not static, but move relative to the subject vehicle, so that adapting the velocity of the subject vehicle generally does not suffice. Rather, is also necessary to time a suitable moment for moving into the adjacent lane. The driver assistance system may also thereby provide support, for instance by outputting acoustic, visual or haptic lane change information to the driver at the appropriate point in time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a symbolic representation of a driver assistance system for motor vehicles; 
         FIG. 2  is a sketch of a traffic situation for clarifying the operation of a turning assistance function; 
         FIG. 3  is a sketch corresponding to  FIG. 2  for the traffic situation at a somewhat later point in time; 
         FIG. 4  is a sketch of a traffic situation for clarifying another operation of the turning assistance function; 
         FIG. 5  is a sketch of a traffic situation where a streetcar track must be crossed when turning off; 
         FIG. 6  is a flow chart for illustrating the principle of operation of the turning assistance function. 
     
    
    
     DETAILED DESCRIPTION 
     In a plan view,  FIG. 1  schematically shows a motor vehicle  10  that is equipped with a driver assistance system according to the present invention. The driver assistance system is constituted in a generally known manner of an electronic data processing system or of a plurality of mutually cooperating data processing systems that receive input signals from various sensory components and transmit output signals to actuators of the motor vehicle, for example to the drive (engine and transmission management), the brake system and the steering system. 
     In the illustrated example, the driver assistance system encompasses a velocity regulation function ACC which, in the first place, evaluates signals from a long-range radar sensor  12  which is installed at the front of the vehicle, locates vehicles in front and other objects in the near field of the subject vehicle  10 , and measures the distances and relative velocities thereof. For purposes of the assistance, a multifunction video camera MFC is provided that likewise observes the near field in front of the vehicle and delivers supplementary information about the located objects, as well as about the road-traffic infrastructure, in particular about lane markings, other traffic routes, such as bicycle routes, streetcar rails and the like, as well as, if indicated, about existing route restrictions, such as speed limits, by recognizing corresponding traffic signs in the video image. 
     As further assistance functions, the driver assistance system includes a blind spot detection BSD and a lane change assist LCA that evaluate the data from two further radar sensors  14  which monitor the space on one side of vehicle  10  next to and behind this vehicle, respectively. These radar sensors  14  are used, in particular, for locating vehicles and other traffic participants in an adjacent lane directly next to the lane traveled by subject vehicle  10 . Radar sensors  14  are thereby also able to measure the relative velocities of the located objects. When it is derived from these data that it is not possible to safely change lanes, but the driver behavior nevertheless indicates an intended lane change, a warning to this effect is superimposed into an exterior rearview mirror  16  of the vehicle. 
     In addition thereto, functions BSD and LCA may also access other sensors, such as ultrasonic sensors, lidar sensors and the like. Since radar sensors  14  monitor first and foremost the space next to and behind subject vehicle  10 , the data from forwardly directed radar sensor  12  may also be evaluated to additionally monitor the adjacent lane. This radar sensor  12  also captures vehicles in adjacent lanes, as long as they are located far enough in front of the subject vehicle. If these vehicles are passed and thereby disappear from the detection range of radar sensor  12 , the probable locations thereof in the adjacent lane may still be estimated by extrapolating the previously measured distance and relative velocity data. 
     In the case of the driver assistance system described here, a lane keeping support LKS is provided as a further assistance function. This function recognizes situations where the driver of subject vehicle  10  is about to cross over the lane markings recognized by video camera MFC. It then outputs a haptic warning signal, for example by inducing a vibration of steering wheel  18  of the vehicle. 
     Finally, a navigation system NAV is provided as a further component of the driver assistance system. With the aid of a position-finding system (for example, GPS), it captures the actual location of subject vehicle  10  and displays this location, along with map information about the surrounding field on a screen  20 . If indicated, the navigation system may also transmit information about speed limits to velocity regulation function ACC and thus ensure that the speed limits are automatically observed, provided that the driver does not override the system. Furthermore, the navigation system may be combined with a communication system that receives information wirelessly about the surrounding field of traffic and updates the same in real time. 
     In addition to these assistance functions, a turning assistance function  30  is provided in accordance with the present invention whose principle of operation is clarified in the following. 
       FIG. 2  illustrates a traffic situation where vehicle  10  equipped with the driver assistance system (discernible by symbolically illustrated radar sensor  12 ) is traveling in a middle lane  22  and is about to pass a vehicle  26  driving in a right adjacent lane  24 . Located further ahead in middle lane  22  is a another vehicle  28  that was detected by radar sensor  12 . Velocity regulation function ACC regulates the velocity of vehicle  10  to ensure that vehicle  28  driving ahead is followed at an appropriate collision-avoidance distance. Thus, vehicles  10  and  28  have the same velocity, as symbolized in  FIG. 2  by vector arrows. 
     In navigation system NAV of vehicle  10 , the route guidance is active, and the navigation system alerts the driver by a voice instruction, by characters on screen display  20  or, as the case may be, also on a heads-up display, that he/she should turn off to the right into a side road  32  after a few hundred meters. The driver of vehicle  10  should, therefore, get into right adjacent lane  24 . However, he/she cannot change over directly into adjacent lane  24  because he/she would then fall short of the safety distance to slower vehicle  26 . On the other hand, he/she can also not complete the passing maneuver to then change into adjacent lane  24  in front of vehicle  26  because he/she would thereby fall short of the safety distance to vehicle in front  28 , as well as the safety distance to (then following) vehicle  26 . 
     In this situation, a turning assistance function  30  becomes active that cooperates with each of the previously mentioned assistance functions, as is symbolically illustrated in  FIG. 1 . In this exemplary case, this turning assistance function serves to reduce the nominal velocity of vehicle  10  to a value that is still below the velocity of vehicle  26  traveling in adjacent lane  24 , so that, relative to vehicle  26 , vehicle  10  drops back until it is able to safely swing into the adjacent lane, behind vehicle  26 . 
     The turning assistance function does not absolutely require that velocity regulation function ACC be already activated beforehand by the driver. Even if ACC were switched off, the ACC function may be automatically activated by the turning assistance function for the purpose of temporarily adapting the velocity to the traffic in the adjacent lane. If the vehicle is not equipped with ACC, rather has only one emergency braking system (collision avoidance system), this emergency braking system may also be utilized as a velocity regulation function in order to control the deceleration of the subject vehicle within the scope of the turning assistance function. 
       FIG. 3  shows the situation at a somewhat later point in time than in  FIG. 2 . The velocity of vehicle  10  has decreased, and the distance both to vehicle  28 , as well as to vehicle  26  has increased correspondingly. At this point in time, there is a sufficient safety distance to vehicle  26 , so that a change to adjacent lane  24  would be possible. 
     In the meantime, one of radar sensors  14  has located another vehicle  34  that is coming closer from behind in adjacent lane  24 . From the absolute velocities of the participating vehicles and the velocities relative to vehicle  10 , safety distances, which vehicle  10  must at least observe relative to vehicles  34  and  26 , are able to be calculated in accordance with known algorithms. In consideration of these safety distances, only a limited window  36  remains (shown in hatched shading in  FIG. 3 ), within which a change to adjacent lane  24  may be safely made. Window  36  moves with vehicles  26  and  34 , and the length thereof may also change over time. 
     At this point, the turning assistance function again increases the nominal velocity for vehicle  10 , thereby allowing it to be adapted to the velocity of window  36 . Moreover, the haptic signal output path of lane keeping support LKS via steering wheel  18  is used for transmitting a lane-change request to the driver, thereby prompting him/her to undertake the lane change at the correct instant, as symbolized in  FIG. 3  by an arrow indicated by a dot-dash line. 
     The relative velocities of vehicles  26  and  34  are continually measured and updated with the aid of radar sensors  12  and  14 . The absolute velocities of these vehicles are then derived by adding the intrinsic velocity of vehicle  10 . Therefore, to determine the optimal point in time for the lane change, turning assistance function  30  is also able to extrapolate into the future the movements of vehicles  26  and  34 , as well as the corresponding movements and, as the case may be, the size variations of window  36 . 
       FIG. 4  illustrates a modified traffic situation that requires a different reaction of turning assistance function  30 . In this example, vehicle  26  has a somewhat lower velocity, and the distance between vehicles  10  and  28  is greater than in  FIG. 2 . Therefore, in this case, there is a large enough window  38  for a change to adjacent lane  24  in front of vehicle  26 , as is symbolized in  FIG. 4  by an arrow indicated by a dot-dash line. Therefore, the turning assistance function instructs that the nominal velocity be increased, and, as soon as subject vehicle  10  has reached the rear boundary of window  38 , the driver receives a lane-change request. 
     When, at the moment that the navigation system announces an imminent turning process, another vehicle (here vehicle  26 ) is located in adjacent lane  24 , for instance next to, somewhat in front of or somewhat behind subject vehicle  10 , then, depending on the traffic situation, the following situations are generally possible. There may be a window  36  behind vehicle  26 , as in  FIG. 3 , or a window  38  in front of this vehicle, as in  FIG. 4 . However, if the traffic in adjacent lane  24  is very dense, it is also possible that there is not a large enough window in front of nor behind vehicle  26 . In such a case, the turning assistance function further decelerates vehicle  10  until a large enough gap  15  opens up in the adjacent lane. Conversely, it is also possible there is a large enough window both in front of vehicle  26 , as well as behind the same, so that the turning assistance function must decide which of the two possible windows should be used. The decision is then dependent upon which of the two windows requires changing the velocity of subject vehicle  10  the least. 
     If there is a speed limit on the traveled route that is captured and reported by the navigation system or by the multifunction video camera, then, in selecting the window, the turning assistance function will also consider that the nominal velocity should not be increased above the authorized speed. 
       FIG. 5  illustrates another traffic situation where vehicle  10  is already traveling in the rightmost lane of a two-lane roadway. In this case, an “adjacent lane”  24 ′ is constituted of a streetcar track laid next to the road that must be crossed when turning off into secondary road  32 . A streetcar  26 ′ is traveling virtually next to vehicle  10 . Here as well, the velocity of vehicle  10  is adapted by the turning assistance function in such a way that the streetcar rail is either crossed behind the streetcar or at an adequate safety distance in front of the same. In contrast to the previously described situations, a slipping into “adjacent lane”  24 ′ is not possible in this case; rather, the streetcar track may only be crossed at that location from where secondary road  32  branches off. The same would also apply if the “adjacent lane” were constituted of a bicycle route, for example. 
     The essential steps of the turning assistance function are illustrated once again in a flow chart in  FIG. 6 . 
     The decision is made in a step S 1  as to whether a turning process is imminent. If this is not the case (N), step S 1  is repeated until the navigation system or the driver himself/herself announces a turning process. If this is the case (Y), it is checked in step S 2  whether the adjacent lane is free. If this is the case (Y), step S 2  is repeated until the lane change to the adjacent lane is concluded. 
     If the adjacent lane is not free (N), i.e., if at least one other traffic participant, such as vehicle  26 , for example, is located in the adjacent lane, then, in step S 3 , the distance and the relative velocity of this other vehicle, as well as, as the case may be, distances and relative velocities of other vehicles in the adjacent lane are measured; on the basis of the absolute velocities and the relative velocities, the safety distances to be observed in each case are calculated, and, on the basis of the locations of the vehicles in the adjacent lane and the safety distances, windows  36 ,  38  in the adjacent lane are calculated. To be more precise, the positions of the beginning and the end of each window are calculated as functions of time, so that even the dynamic changes in this window are considered and may be extrapolated into the future. 
     When at least two large enough windows are present, the most favorably situated window is selected in step S 4 . 
     The nominal velocity of the subject vehicle is adapted in step S 5  in such a way that the subject vehicle arrives next to the selected window and is then adapted to the velocity of the window, i.e., is adapted to the velocities of the vehicles that bound this window. As soon as the subject vehicle reaches a position and velocity where a safe lane change is possible, the driver receives a lane change instruction in step S 6 . 
     In situations where, as in  FIG. 5 , the adjacent lane may only be crossed, but not driven in, step S 6  is eliminated.