Patent Publication Number: US-2017349171-A1

Title: Controlling a protection device of a motor vehicle

Description:
CROSS REFERENCE 
     The present application claims the benefit under 35 U.S.C. §119 of German Patent Application No. DE 102016209735.0 filed on Jun. 2, 2016, which is expressly incorporated herein by reference in its entirety. 
     Field 
     The present invention relates to an active protection device for a motor vehicle. In particular, the present invention relates to controlling the protection device. 
     Background Information 
     One or multiple driver assistance systems are provided on board a motor vehicle, which may support a driver in predetermined driving situations. For example, an adaptive cruise control (ACC) may be provided, which maintains the speed of the motor vehicle at a predetermined value and at the same time prevents the motor vehicle from rear-ending a preceding motor vehicle. Such assistance systems may be configured to improve their determination or intervention results based on surroundings information. 
     German Patent Application No. DE 10 2014 204 383 A1 relates to a driver assistance system which scans surroundings of the motor vehicle and divides these into areas of differing criticality. Areas considered to be critical may be analyzed longer than less critical areas. 
     German Patent Application No. DE 10 2013 226 004 A1 provides for carrying out an automated emergency braking when a driver-controlled use of brakes is considered to be too sluggish. 
     It is an object of the present invention to provide an improved technique for controlling a motor vehicle including a protection device. Preferred specific embodiments are described herein. 
     In accordance with the present invention, a method is provided for controlling a motor vehicle including steps of determining a position of the motor vehicle; determining topographical surroundings of the position based on pieces of map information; and controlling, based on the determined topographical surroundings, an active protection device on board the motor vehicle if a collision of the motor vehicle with another object is imminent. The pieces of topographical information may in particular be provided based on pieces of map information or with the aid of a surroundings sensor system. 
     The active protection device is configured to assume or influence a longitudinal or transverse control of the motor vehicle. For example, an automatic brake assistance system may be configured to forcibly cause an emergency braking of the motor vehicle. The topographical surroundings of the position may be determined based on map data which are either present locally on board the motor vehicle or may be procured via a mobile data transmission connection. By controlling the active protection device as a function of the determined topographical surroundings, it is possible, on the one hand, to improve a determination as to whether or not the protection device is to intervene, and, on the other hand, the manner in which the protection device takes action may be adapted as a function of the surroundings. 
     It is preferred that it is determined, based on the determined topographical surroundings, whether or not a collision with the other object is imminent. The other object may in particular be detected with the aid of a sensor on board the motor vehicle. Occasionally, however, measuring or processing errors occur, so that an object is determined where in fact none is present. Conversely, an actually present object may also not be detected by the sensor, for example since the object is partially or entirely shadowed by a structure or vegetation. Taking the topographical surroundings into consideration, the detection and, if necessary, the identification of the object or the determination of its movement may be subjected to a plausibility check. Objects subjected to a plausibility check may have improved relevance for the decision as to whether or not the collision with the other object is impending. 
     It is furthermore preferred that a trajectory of the motor vehicle or of the other object is predicted based on the determined topographical surroundings. It may be assumed, for example, that the motor vehicle will continue to move on a road or on a path. Various other possible trajectories may thus be discarded. Similarly, it may be predicted that the other object, which in particular may include another motor vehicle or another road user, behaves correspondingly. The type of the other road user (pedestrian, bicyclist and the like) may be used to reduce the number of possible trajectories or those considered to be plausible. 
     In one further specific embodiment, surroundings of the motor vehicle are scanned with the aid of a sensor, the scanning being interpreted based on the determined topographical surroundings. In particular, poor scans, for example due to unfavorable incident light or vibration, may be improved by the interpretation aid based on the topographical surroundings. 
     It is furthermore preferred that the function of the protection device on board the motor vehicle is controlled based on the determined topographical surroundings. For example, a restraint system for passengers may operate in different manners, these manners possibly being dependent on the type of hazard for the occupants apparent from the pieces of topographical information. 
     In one specific embodiment, the protection device is controlled as a function of whether the motor vehicle is situated in the area of an intersection. For example, it may be continuously determined when a collision with the object will take place based on a present situation. This time is also referred to as Time To Collision (TTC) and may be determined assuming various scenarios. When this time drops below a predetermined threshold value, the protection device may be triggered. The threshold value may be made dependent on the type of topological surroundings in which the motor vehicle is situated. For example, the threshold value may be raised in the area of an intersection in order to counteract the particularly frequent accident type of a collision with another motor vehicle in the case of intersecting traffic. 
     In one further specific embodiment, the protection device is controlled as a function of whether the motor vehicle is situated in the area of a tight curve. In such a driving situation, there is an increased risk that the motor vehicle partially uses the lane for oncoming traffic. Moreover, oncoming traffic may erroneously be interpreted as cross traffic which is on a collision course. Consequently an—unjustified—activation of the safety function may occur. To avoid this, it may be useful in such a situation to react later, and thus less frequently, than at an intersection, for example. For this purpose, in particular the above-mentioned threshold value for the TTC may be lowered. 
     A control device for a motor vehicle includes a positioning unit for determining a position of the motor vehicle; a data source for pieces of map information for determining topographical surroundings at the position; and a processing unit. The processing unit is configured to control a protection device on board the motor vehicle if a collision of the motor vehicle with another object is imminent. 
     The control device may contribute to improving a conventional protection device either in its response behavior or in its execution behavior. The control device may in particular be designed as a programmable microcomputer and optionally may be designed having another control device integrated on board the motor vehicle. 
     In different specific embodiments, the protection device may act in different manners. In a first specific embodiment, the protection device includes an output unit for a warning directed at a driver of the motor vehicle. The warning may be output acoustically, visually or haptically. In a second specific embodiment, the protection device includes an influencing unit for a driver-controlled acceleration request. In particular, the acceleration request of a driver may not be met when it is determined that in this case a collision with another object is imminent. In a third specific embodiment, the protection device includes a braking unit which may automatically activate a braking system on board the motor vehicle in order to decelerate the motor vehicle or maintain it at a standstill. In yet another specific embodiment, the protection device includes an activation unit for a passive protection device, such as an airbag or a seat belt tensioner. 
     The present invention is described in greater detail below with reference to the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a system including a motor vehicle. 
         FIG. 2  shows a flow chart of a method for controlling the motor vehicle from  FIG. 1 . 
         FIG. 3  shows an exemplary driving situation of the motor vehicle from  FIG. 1  at an intersection. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG. 1  shows a system  100  including a motor vehicle  105 . A control device  110  for controlling a protection device  115  is situated on board motor vehicle  105 . Control device  110  includes a processing unit  120  and a data memory  125  or a wireless interface  130 . With the aid of an interface  135 , processing unit  120  is connected to protection device  115 , and preferably to a positioning unit  122 . Optionally, additionally a sensor  140  is configured to scan surroundings  145  of motor vehicle  105  and, in particular, to scan an object  150  in surroundings  145 . Object  150  may be a stationary or mobile obstacle, with which a collision by motor vehicle  105  is to be avoided. 
     With the aid of positioning unit  122 , a position of motor vehicle  105  may be determined. For this purpose, positioning unit  122  may in particular include a receiver for signals of a satellite-based positioning system. Positioning unit  122  may be part of a navigation system for guiding motor vehicle  105  to a predetermined destination. In one specific embodiment, positioning unit  122  is configured to determine a highly precise position in the range of approximately 1 to 2 cm. In one other specific embodiment, a positioning may be used which is less precise, for example of approximately 1 to 5 m. 
     Pieces of topographical information about surroundings  145  at the determined position may either be taken from data memory  125  or be received via wireless interface  130 . In one specific embodiment, specific pieces of topographical information may be requested via wireless interface  130 , for example by a central server, indicating the determined position. Pieces of topographical information may also be provided with the aid of sensor  140 , which in particular may include a video camera, by scanning surroundings  145  of motor vehicle  105 . Wireless interface  130  may enable a data connection to a data traffic network such as the Internet. Processing unit  120  is configured to control either a triggering of protection device  115  or the execution of the function of protection device  115  based on the determined topographical surroundings  145 . In this way, an unwarranted activation of protection device  115  may be avoided or a functional benefit of protection device  115  may be improved. 
     In one specific embodiment, it is determined, based on the scanning of surroundings  145 , with the aid of sensor  140 , whether a collision risk with object  150  exists. Since such a measurement is always subject to error, an object  150  may erroneously be determined; this is also referred to as a ghost target. Additionally, it is possible that a traffic situation is misjudged, and a seemingly critical situation in reality is harmless. In general, erroneous activations of protection device  115  may be minimized by triggering protection device  115  as late as possible. A sensory or situational uncertainty may thus be minimized prior to triggering protection device  115 . 
     For example, pieces of topographical information of surroundings  145  may be utilized to detect the progression of a roadway on which motor vehicle  105  or object  150  is situated, or to have an improved overview of an intersection of multiple roads. Correctly and incorrectly assessed objects  150  may thus be distinguished from one another in an improved manner. The criticality of a traffic situation may be assessed more reliably. 
     Protection device  115  may trigger different measures on motor vehicle  105 . One variant is considered hereafter by way of example, which intervenes in an intersection situation during an impending collision with cross traffic. This function is referred to as Front Cross Traffic Assist (FCTA). Within the scope of the FCTA, usually pieces of visual information about approaching cross traffic are scanned with the aid of sensor  140  upon entering a complex intersection. If it is determined that a collision of motor vehicle  105  with object  150  is imminent, a starting or an acceleration of motor vehicle  105  from the creeping mode is prevented. If motor vehicle  105  is already moving at a predetermined speed, for example between 10 km/h and 60 km/h, an automatic partial or full brake application may be initiated when an impending collision with the cross traffic is determined. If a collision is not preventable, a passive safety system on board motor vehicle  105 , such as an airbag, may be automatically triggered. 
     For the decision as to whether protection device  115  (the airbag) is to be triggered, the positions of motor vehicle  105  and/or of object  150  may be predicted. Since the intention of the drivers is usually not known, the prediction may be based on different maneuvers, for example braking, accelerating, turning, defensive or sporty driving style and the like. Out of all variants, the longest Time To Collision is selected. The least critical, i.e., the safest, maneuver is then assigned to this TTC. If the longest TCC drops below a predetermined threshold value, protection device  115  is triggered. 
     It is provided to control protection device  115  based on pieces of information about topographical surroundings  145  of motor vehicle  105 . 
       FIG. 2  shows a flow chart of a method  200  for controlling motor vehicle  105  from  FIG. 1 . Method  200  is in particular configured to run on control device  110 , and in particular processing unit  120 . For this purpose, processing unit  120  may include a programmable microcomputer, and method  200  may be present in the form of a computer program product at least in parts. 
     In a step  205 , the position of motor vehicle  105  is determined. In a step  210 , topographical surroundings  145  at the determined position are determined. In a step  215 , it may be determined whether motor vehicle  105  is situated in the area of a topographical territory categorized as hazardous, for example in the area of a curve or an intersection of two or multiple roads. If this is not the case, method  200  may terminate or recommence. 
     Otherwise, object  150  in surroundings  145  is scanned with the aid of sensor  140  in an optional step  220 . If no object  150  is present in surroundings  145 , method  200  may also terminate or recommence. 
     If an object  150  has been found, a trajectory of motor vehicle  105  is preferably predicted concurrently in a step  225 , and a trajectory of object  150  is predicted in a step  230 . In both steps  225 ,  230 , a plurality of different trajectories may be determined, which in particular may be identified based on the determined topographical surroundings  145 . 
     In a step  235 , it is determined whether a collision of motor vehicle  105  with object  150  is imminent. For this determination, the pieces of topographical information of surroundings  145  may be used again. In one specific embodiment, multiple different future scenarios were determined in steps  225  and  230 , preferably all of which are analyzed in step  235 . Whether or not a collision between motor vehicle  105  and object  150  is imminent in a certain scenario may be determined based on a time which remains until the collision according to the corresponding scenario being below a predetermined threshold value. This remaining time (Time To Collision, TTC) may be determined for all scenarios. If all TTC are above a predetermined threshold value, no collision is imminent, and method  200  may terminate or recommence. It is preferred that the threshold value is varied as a function of topographical surroundings  145  of motor vehicle  105 . For example, the threshold value may be the greater, the more complex an intersection is which motor vehicle  105  approaches. By raising the threshold value, the functional benefit of the safety function may be increased. 
     If it was determined that a collision is imminent, in a step  240  protection device  115  may not only be triggered, but also be controlled based on the determined topographical surroundings  145 . 
       FIG. 3  shows an exemplary driving situation of motor vehicle  105  from  FIG. 1  at an intersection  300  of a first road  305  with a second road  310 . Motor vehicle  105  approaches intersection  300  on first road  305 . Object  150  from  FIG. 1  is also a motor vehicle here and approaches intersection  300  on second road  310 . A visibility obstruction  315  is situated at one corner of intersection  300 , which may impair a correct scanning of motor vehicle  150  on the part of motor vehicle  105 . Multiple alternative first trajectories  320  for first motor vehicle  105  and multiple alternative second trajectories  325  for second motor vehicle  150  are plotted by way of example. Usually it is not known for either of motor vehicles  105 ,  150  which of the possible trajectories  320  or  325  they will pursue. However, different combinations of trajectories  320 ,  325  may be analyzed as to whether or not a collision between motor vehicles  105 ,  150  is imminent. 
     In one specific embodiment, non-drivable maneuvers of one of motor vehicles  105 ,  150  are excluded in the collision prediction. Such a maneuver may include a departure from roads  305  and  310 , for example. The number of the trajectory combinations to be checked may thus be significantly reduced. 
     Impermissible turning maneuvers of one of motor vehicles  105 ,  150  may also be excluded from the collision prediction. Other maneuvers which are not permissible according to the road traffic ordinances, such as driving on a one-way road in the wrong direction or turning into the wrong direction, may also be excluded. 
     The above-described threshold value for the determination of whether or not a collision is imminent may in particular be increased when motor vehicle  105  is situated on a subordinate road  305 , i.e., does not have the right of way with respect to motor vehicle  150 . The safety function may thus intervene sooner or more progressively. 
     In one specific embodiment, a driver of motor vehicle  105  is given a visual indication of potentially approaching cross traffic in the form of motor vehicle  150  at an early stage (approximately 5 seconds prior to passing second road  310 ). A prediction horizon on this order of magnitude of time is considered long, so that it is not possible to exclude a situational uncertainty, and accordingly an unwarranted activation of protection device  115 . However, since the warning is only useful in the area of an intersection  300 , a piece of information about cross traffic outside intersection  300  would only interfere with or distract the driver of motor vehicle  105 . It is thus preferred to output pieces of information about the cross traffic of motor vehicle  150  only to the driver of motor vehicle  105  when it was established, based on the pieces of topographical information, that motor vehicle  105  is situated in the area of an intersection  300 . 
     In a situation other than that illustrated in  FIG. 3 , motor vehicle  105  is situated in the area of a tight curve, in particular a tight left turn. Due to the curve, an oncoming motor vehicle has a certain speed in the transverse direction with regard to motor vehicle  105 , so that it may erroneously be identified as cross traffic. By having knowledge of the topographical information of the curve, an erroneous triggering of protection device  115  may be suppressed in an improved manner. Moreover, protection device  115  may be operated more conservatively, so that it is triggered later than in another situation. In this way, an erroneous triggering may thus be less likely or less frequent. 
     In yet another specific embodiment, a reaction to an object  150  which is not moving along one of roads  305 ,  310  may be discarded or postponed to a later point in time. 
     In one further specific embodiment, a reaction to an object  150  may take place later or not at all if it is not situated on a roadway  305 ,  310 . A so-called “ghost target” may thus be suppressed in an improved manner. 
     In yet another specific embodiment, a reaction to an object  150  situated behind visibility obstruction  315  may not take place or may take place delayed. In such a situation, it may be assumed that an indication of object  150  represents an erroneous measurement, which was recorded, for example, due to a reflection on a wall or a glass pane by sensor  140 . Due to the plausibility check based on topographical map data, an erroneous triggering of protection device  115  may be avoided in an improved manner. 
     According to the present invention, a driving situation of motor vehicle  105  may be better determined and/or a decision as to whether and how protection device  115  is to be triggered may be made in an improved manner based on a scanning of surroundings  145  of motor vehicle  105 , for example with the aid of sensor  140 , and topographical data of surroundings  145 .