Abstract:
A method for assisting a driver of a vehicle when parking in a parking space is disclosed. The method involves measuring a possible parking space, calculating a parking trajectory on the basis of a current parking space geometry determined from the measurement of the parking space and on the basis of a vehicle position relative to the parking space, and a parking process is subsequently carried out during which the vehicle is steered along the parking trajectory into the parking space, continuing to determine, during the parking process, the current parking space geometry and is compared with a previous parking space geometry determined before the start of the parking process, where, if the two parking space geometries differ from one another, a deviation which is present is evaluated and the parking trajectory corrected and/or re-calculated.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method for assisting a driver of a vehicle when parking in a parking space according to the preamble of Claim  1 , a driver assistance device according to the preamble of Claim  19  and a computer program product according to the preamble of Claim  21 . 
     Known driver assistance devices for assisting a driver of a vehicle when parking in a parking space, referred to below for short as parking systems, calculate, at the start or before the start of a parking process, a path for the parking of the vehicle, referred to as the parking trajectory. This path is calculated on the basis of the parking space geometry and of a vehicle position relative to this parking space. In this context, a parking system measures, with a measuring device which comprises suitable sensors, these being ultrasonic sound sensors (ultrasonic park assist sensors; UPA sensors) which are mounted, for example, at the front and/or rear of the vehicle and/or to the side of the vehicle, a possible parking space, calculated from the parking space data and the parking space geometry obtained therefrom, the parking trajectory and subsequently carries out the parking process by steering the vehicle along the parking trajectory into the parking space, for example by active steering intervention or by driving instructions to the driver. During the parking process, the distance from objects which bound the parking space is monitored by the sensors. 
     Current parking systems freeze the calculated path before and at the start of the parking process. Furthermore, currently used measuring devices for sensing the parking space geometry have a variation which can act disadvantageously on the parking result, i.e. on the placing of the vehicle, achieved at the end of the parking process, in a target position or in a target orientation in the parking space. 
     SUMMARY OF THE INVENTION 
     It can therefore be considered an object of the invention to develop a method for assisting a driver of a vehicle when parking in a parking space, which method permits a satisfactory parking result independently of the variation of a measuring device used and independently of a parking space geometry which is possibly sensed in an insufficient way. 
     The object is achieved by means of a method for assisting a driver of a vehicle when parking in a parking space, in which method
         a possible parking space is measured, and a vehicle position relative to the parking space is preferably determined at the same time,   a parking trajectory is calculated on the basis of the parking space geometry which is determined from the measurement of the parking space, and on the basis of a vehicle position relative to the parking space, and   a parking process is subsequently carried out during which the vehicle is steered along the parking trajectory into the parking space.       

     According to the invention there is provision for the parking space geometry to continue to be determined during the parking process on the basis of current sensor data which are acquired by a suitable sensor system for measuring the parking space, and for said parking space geometry to be compared with the parking space geometry determined before the start of the parking process, wherein, if the two parking space geometries differ from one another, a deviation which is present is evaluated and the parking trajectory is, if appropriate, corrected and/or re-calculated. 
     By means of the invention, information which is first determined during the parking process and in that case with improved accuracy may be converted to a usable form and therefore contribute to improving the parking result, in particular in difficult situations, and thus ultimately to improving the usability and customer satisfaction of a parking system. 
     The method according to the invention has, compared to the prior art, the advantage that if sensor data are present during the parking process which permit better placing of the target position/target orientation of the vehicle in the parking space, said method permits corresponding correction of the parking trajectory. The method according to the invention therefore provides the possibility of a path correction during the parking phase or a correction of the parking trajectory during the parking process on the basis of current, and therefore more accurate, sensor data. 
     The steering of the vehicle along the parking trajectory can be implemented as guided parking or as semi-automatic parking or as fully automatic parking. 
     One advantageous refinement of the invention provides that if the difference between the parking space geometry determined before the parking process and that determined during the parking process is small, and for example lies within the respective system-conditioned variation, the original parking space geometry and therefore the parking trajectory calculated before the start of the parking process is retained, and if the parking space geometry determined during the parking process differs significantly from the originally determined parking space geometry and this difference is relevant for the parking result, the parking trajectory is re-defined or corrected on the basis of the parking space geometry currently determined during the parking process. 
     Another advantageous refinement of the invention provides that the distance from objects which bound the parking space is monitored, for example by means of a suitable sensor system or by means of suitable sensors, during the parking process. 
     One particularly advantageous refinement of the invention provides that a comparison between the parking space geometry determined before the parking process and that determined during the parking process is carried out by sensing, during the entry into the parking space, the lateral distance, to the left and right of the vehicle, from objects which bound the parking space and by comparing said lateral distance with the distances which are expected on the basis of the originally sensed parking space geometry and the current vehicle position. 
     It is also conceivable that a comparison between the parking space geometry determined before the parking process and that determined during the parking process is carried out by sensing, during the entry into the parking space, the profile, to the left and right of the vehicle, of objects which bound the parking space, wherein, if it can be detected on the basis of the profile that the parking space has an orientation which differs from the parking space geometry determined before the parking process or form the original definition, the parking trajectory is correspondingly corrected. 
     In order to determine the orientation of the parking space, the profile of the two lateral objects is preferably represented in each case as a straight line. If both straight lines extend approximately in parallel, the mean value of the two straight lines is preferably adopted as the orientation of the parking space. 
     In the event of a deviation of the profile of the measured straight lines from the real straight lines, lateral distance data can be used to correct the parking trajectory during the parking process, for example by means of ultrasonic sound sensors which are mounted laterally on the rear bumper. In the event of parallel displacement of the straight lines, the parking trajectory can be corrected with the evaluation of these ultrasonic sound sensors essentially by corresponding parallel displacement. In contrast, in the event of a directional offset of the straight lines, the target angle of the parking trajectory can be corrected with the ultrasonic sound sensors which are mounted laterally on the rear bumper. 
     If both straight lines do not extend sufficiently in parallel but have the same orientation with respect to the original target orientation, the straight line which differs the least from the original target orientation is preferably adopted as the orientation of the parking space. If both straight lines do not extend sufficiently in parallel and are oriented differently with respect to the original target orientation, a mean value of the two straight lines is preferably adopted as the orientation of the parking space. If both straight lines do not extend sufficiently in parallel and are oriented differently with respect to the original target orientation, the original target orientation is preferably retained. Advantages of these refinements of the method according to the invention are that as a result it is possible not only to park in parking spaces which are oriented virtually at a right angle to the carriageway but also in what are referred to as oblique parking spaces. 
     One advantageous refinement of the invention provides that, in order to determine the parking space geometry during the parking process, a measuring device is provided which is primarily provided for assisting the driver of the vehicle in a situation other than that during a parking process. 
     Alternatively, in order to determine the parking space geometry during the parking process, a measuring device is provided which is provided specially for assisting the driver of the vehicle during a parking process. 
     The measuring device can comprise ultrasonic sound sensors installed in the vehicle, for example additional lateral ultrasonic sound sensors in the rear part of the vehicle and/or a camera which is present in the vehicle, for example a reversing camera and/or radar sensors, for example a sensor system for monitoring the blind spot. 
     One particularly advantageous refinement of the invention provides that, in order to determine the parking space geometry before and/or during the parking process, parking space markings are captured, for example, by a reversing camera and detected, for example, by means of suitable image processing, wherein the position and orientation of the parking space markings are determined. Since these parking space markings are generally located in the edge region of a camera image before the start of the parking process, determination only becomes appropriate during the parking process, but at least the accuracy of the determination is improved if the parking space marking migrates in the direction of the centre of the image during the parking process. This applies in particular to adverse light conditions and/or contrast conditions. 
     Another particularly advantageous embodiment of the invention provides that, in order to determine the parking space geometry before and/or during the parking process, a profile of the kerb is sensed and/or determined, for example on the basis of distance data and/or visually, for example by means of a camera. 
     A further particularly advantageous refinement of the invention provides that there is additionally provision for the target parking position and/or orientation in the parking space to be verified and confirmed or corrected by the driver, for example by means of a representation of the parking situation on a display. This may be done, for example, by superimposing, for example on an image of the reversing camera, a target parking position which is determined by the system. 
     The invention can advantageously be applied in particular in conjunction with a driver assistance device for assisting the driver of a vehicle when parking in a parking space. Such a driver assistance device preferably comprises:
         means for measuring a parking space before and during a parking process,   a microprocessor which is connected to the means and has associated storage means for calculating and/or correcting a parking trajectory on the basis of the parking space geometries which are determined from the measurement of the parking space before and during the parking process, and on the basis of a vehicle position relative to the parking space, wherein the microprocessor with associated storage means compares the parking space geometry determined during the parking process with the parking space geometry determined before the start of the parking process, and if the two parking space geometries differ from one another a difference which is present is evaluated and the parking trajectory is, if appropriate, corrected and/or recalculated, and   means for carrying out the parking process during which the vehicle is steered along the parking trajectory into the parking space.       

     One advantageous application of the method according to the invention arises in conjunction with a driver assistance device which permits guided parking or semi-automatic parking or fully automatic parking of a vehicle along the parking trajectory into the parking space. 
     One particularly advantageous refinement of the invention relates to a computer program product stored on a computer-compatible medium, comprising computer-readable program means which, when the computer program product is executed on a microprocessor with associated storage means or on a computer, cause the latter to carry out a method according to the invention as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention are illustrated in the figures of the drawing and will be explained in more detail below. In said drawings: 
         FIG. 1  shows a schematic illustration of a first parking process, 
         FIG. 2  shows a schematic illustration of a second parking process, 
         FIG. 3  shows a schematic illustration of a third parking process with parallel deviation of a real lateral object from the measured object, and 
         FIG. 4  shows a schematic illustration of a fourth parking process with a directional offset of one or both real lateral objects. 
     
    
    
     DETAILED DESCRIPTION 
     A first exemplary embodiment of a method according to the invention is explained below with reference to  FIG. 1 .  FIG. 1  shows a correction according to the invention of a parking trajectory  01  and therefore of the lateral positioning of a vehicle  02  in a parking space  03  in a right-angled parking situation on the basis of additional lateral ultrasonic sound sensors in the rear bumper of the vehicle  02 . 
     Due to a measurement error during the original parking space measurement before the start of a parking process, a system view has resulted in which an object  07  which bounds the parking space  03  on the right, here another parked vehicle  07 , is not located in its actual position but rather in an erroneous position  08 . On the basis of the erroneous parking space geometry which was determined from the measurement of the parking space  03  before the start of the parking process and corresponds to the system view, and on the basis of a vehicle position relative to the parking space  03 , a parking trajectory  04  has initially been calculated in which the vehicle  02 , when steered along the parking trajectory  04  into the parking space  03 , would not be positioned centrally as desired but rather off-centre in the parking space  03  due to the measurement error. 
     In order to correct this, the lateral distance  06  from the objects  09 ,  07  to the left and right of the vehicle  02  is sensed during the entry into the parking space  03 , as illustrated in  FIG. 1 , and said lateral distance  06  is compared with the distances which are expected on the basis of the originally sensed geometry and the current vehicle position. 
     The offset is detected and the parking trajectory  01  is correspondingly corrected so that, instead of the parking trajectory  04  which is based on the measurement error and which reflects the erroneous system view before the start of the parking process, the parking trajectory  05  which is adapted to the actual situation is now present, and the vehicle  02  is now moved along said parking trajectory  05  into a final target position in the parking space  03 . 
     Alternatively, the lateral distances  06  can be sensed during the parking process by means of radar sensors which are present for monitoring the blind spot. As a result, no additional costs are incurred for specific sensors or for a specific sensor system. 
     A second exemplary embodiment of a method according to the invention is explained below with reference to  FIG. 2 .  FIG. 2  shows an inventive correction of a parking trajectory  11  and therefore the target orientation of the vehicle  12  in a parking space  13  given a non-right-angled parking situation on the basis of additional lateral ultrasonic sound sensors in the rear bumper of the vehicle  12 . 
     A parking trajectory  14  is also initially calculated here on the basis of a measurement of the parking space before the start of a parking process, and said parking trajectory  14  would lead to an unsatisfactory parking result owing to insufficient measurement of the parking space  13  due to the non-right-angled parking situation. 
     The determination of the target orientation of the vehicle  12  in a parking space  13  which is not oriented at a right angle to a road which is illustrated schematically by arrow F is difficult since as a rule sufficient information is not available from the determination of the parking space geometry due, for example, to shadowing of the objects  17 ,  19  which bound the parking space laterally. The target orientation has hitherto typically been defined at a right angle to the road F of the vehicle  12  as the latter travels past the parking space  13 . 
     For this reason, according to the invention the profile of the objects  19 ,  17  to the left and right of the vehicle  12  is sensed during the entry into the parking space  13 . If it is possible to detect on the basis of the profile that the parking space  13  has an orientation or geometry which deviates from the original definition, the parking trajectory  11  is correspondingly corrected so that, instead of the original parking trajectory  14 , a parking trajectory  15  which is adapted to the actual situation is now present, and the vehicle  12  is moved along said parking trajectory  15  into its final target position in the parking space  13 . 
     One possible way of detecting the orientation of the parking space  13  may be here to represent the profile of the two lateral objects  17 ,  19  as a straight line. 
     If both straight lines extend approximately in parallel, the mean value of the two straight lines is adopted as the orientation of the parking space  13 . 
     If both straight lines do not extend sufficiently in parallel but have the same orientation with respect to the original target orientation, the straight line which deviates the least from the original target orientation is adopted as the orientation of the parking space  13 . 
     If both straight lines do not extend sufficiently in parallel and are differently oriented with respect to the original target orientation, either a mean value of both straight lines can be adopted as the orientation of the parking space  13  or the original target orientation can be retained. 
     A significant advantage of this second exemplary embodiment is that as a result it is possible not only to park in parking spaces  13  which are oriented virtually at a right angle to the carriageway or to a road F but also in what are referred to as oblique parking spaces. 
     An exemplary embodiment of a method according to the invention provides correction of the parking trajectory on the basis of parking space markings which are detected by a reversing camera. 
     Parking space markings can be sensed by a reversing camera and detected by means of suitable image processing. In this context, the position and orientation of the parking space markings are determined. 
     Since these parking space markings are generally located in the edge region of the camera image before the start of the parking process, determination only becomes appropriate during the parking process but at least the accuracy of the determination improves if the parking space marking migrates in the direction of the centre of the image during the parking process. This applies in particular to adverse light conditions and/or contrast conditions. 
     It is also conceivable that a profile of the kerb is determined instead of a parking space marking. 
     A third exemplary embodiment of a method according to the invention will be explained below with reference to  FIG. 3 . This figure shows an inventive correction of a parking trajectory  21 , and therefore for the purpose of driving a vehicle  22  into a parking space  23  in a parking situation in which the real position of a vehicle  29   b  deviates from the measured position (vehicle  29   a ) through parallel displacement. As a result of evaluation of the distance data of laterally mounted ultrasonic sound sensors in the rear bumper of the vehicle  22 , the parking trajectory  21  which is firstly determined on the basis of the measured values can be recalculated here in the direction of the new parking trajectory  24  (represented by dashed lines) taking into account the lateral distance values from the real position of the vehicle  29   b , said lateral distance values having been measured during the parking process. 
     In a fourth exemplary embodiment of a method according to the invention, an explanation is given on the basis of  FIG. 4  as to how, in the case of a directional offset of the initially measured straight line of a vehicle  39   b  (or vehicle  37   b ) with respect to a real vehicle  39   a  (or vehicle  37   a ), the target angle of the parking trajectory  31  is corrected with respect to a new parking trajectory  34  (represented by dashed lines) using the distance values of the ultrasonic sound sensors on the parking vehicle  33 , said sensors being mounted laterally on the rear bumper. 
     In summary, the invention provides that the geometry of the parking space is determined by means of a suitable sensor system during the parking process and compared with the geometry determined before the start of the parking process. If the two geometries differ from one another, the deviation which is present is evaluated. This permits correction of the parking trajectory on the basis of current sensor data during the parking process. 
     If the difference is small and is due, for example, to the respective system-conditioned variation, the original geometry is retained. 
     If the geometry which is determined during the parking process differs significantly from the original geometry and this difference is relevant for the parking result, the parking trajectory is redefined or corrected on the basis of the currently determined geometry. 
     By means of the invention, information which is firstly determined during the parking process and in that case determined with improved accuracy can be converted into a usable form and therefore contribute to improving the parking result, in particular in difficult situations, and therefore to ultimately increasing the usability and customer satisfaction of a parking system. 
     A suitable sensor system here is, in addition to the ultrasonic sound sensors already installed in the vehicle, an existing camera, for example a reversing camera or radar sensors, for example a sensor system for monitoring the blind spot. It is also conceivable to install a sensor system which is provided especially for redetermining the parking space geometry during the parking process, for example additional lateral ultrasonic sensors in the rear region of the vehicle. 
     Basically it is conceivable, in addition to the specified measures, to have the driver perform verification and confirmation or correction of the target parking position and/or target orientation in the parking space, for example by means of a representation of the parking situation on a display. This may be done, for example, by superimposing a target parking position determined by the system on an image of the reversing camera, for example.