Abstract:
A method for calibrating a vehicle surroundings sensor ( 15 ) includes the steps of attaching at least one target pair ( 20, 22 ) to the rear wheels ( 12, 14 ) of a motor vehicle ( 7 ); recording the target pair ( 20, 22 ) using at least one measuring unit ( 32, 46 ) and determining the vehicle axis ( 64 ) from the recording; placing a target ( 16, 18 ) in a known position relative to a vehicle surroundings sensor adjustment or calibration element ( 62 ); fastening at least one measuring unit ( 32, 46 ) by means of fastening adapters ( 34, 48 ) to a running rail ( 4, 6 ); recording the target ( 18 ) placed on the vehicle surroundings sensor adjustment and determining the angular position of the vehicle surroundings sensor adjustment or calibration element ( 62 ) relative to the vehicle axis ( 64 ); aligning the vehicle surroundings sensor adjustment or calibration element ( 62 ) relative to the vehicle axis ( 64 ); and adjusting the vehicle surroundings sensor ( 15 ) relative to the vehicle axis ( 64 ).

Description:
CROSS-REFERENCE 
     The invention described and claimed hereinbelow is also described in PCT/EP2009/061006, filed on Aug. 26, 2009 and DE 10 2008 042 018.2, filed on Sep. 12, 2008. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method for adjusting or calibrating a vehicle surroundings sensor, and to a vehicle surroundings sensor adjustment or calibration system. 
     “Driving assistance systems”, which monitor the vehicle surroundings and deliver related information to the driver, are being used in an increasing number of motor vehicles. Many systems even actively intervene in the vehicle operation and automatically brake or accelerate the vehicle. Other systems monitor e.g. the vehicle position relative to the road using markings on the road. As soon as the vehicle approaches the edge of the road, this can be communicated to the driver acoustically and/or visually. 
     These driving assistance systems must be aligned at least relative to the axis of the motor vehicle. Therefore, they must be calibrated or adjusted at certain intervals of time. This type of calibration or adjustment of driving assistance systems is highly complex and results in high additional costs for the equipment required for this purpose. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a vehicle surroundings adjustment or calibration system and a related method for adjusting or calibrating a vehicle surroundings sensor that makes it possible to perform a calibration or adjustment of this type in a simple and cost-effective manner. 
     Using the method, according to the invention, for adjusting or calibrating a vehicle surroundings sensor according to the independent method claim, and using the vehicle surroundings sensor adjustment or calibration system according to the independent device claim, the targets and the measuring units of the chassis measuring device are used to determine the position of the vehicle surroundings sensor adjustment or calibration element and, therefore, of the vehicle surroundings sensor relative to the driving axis and, based thereon, the vehicle surroundings sensor can be adjusted or calibrated. 
     The driving axis is determined by the position of the wheels on the rear axle, and can deviate from the longitudinal mid-plane of the motor vehicle. 
     According to the invention, common targets can be used to adjust or calibrate the vehicle surroundings sensor. To “adjust” is understood to mean adjusting the vehicle surroundings sensor itself, and to “calibrate” is understood to mean the computation-based compensation of measured values ascertained using the vehicle surroundings sensor. 
     The adjustment or calibration, according to the invention, of a vehicle surroundings sensor is easy to perform, and even unknown targets can be used, that is, targets that do not have a known configuration of control points. 
     According to the invention, all vehicle surroundings sensors located on or in the motor vehicle can be adjusted or calibrated. The vehicle surroundings sensors to be adjusted or calibrated according to the invention can be e.g. optical, radar-based, or ultrasound-based vehicle surroundings sensors. 
     The method, according to the invention, for adjusting or calibrating a vehicle surroundings sensor, and the vehicle surroundings sensor adjustment or calibration system according to the invention do not require any additional measuring elements or, in particular, any electronics on the adjustment or calibration device, thereby reducing costs considerably. 
     Compared to chassis measuring devices having CCD (Charge-Coupled Device) technology, the further advantages results that additional electronics on the adjustment or calibration device, and the associated cables, can be eliminated, and it is possible to check the vehicle surroundings sensors even across long distances, thereby eliminating the restriction that the distances between the measuring elements on the motor vehicle and the measuring elements on the adjustment or calibration device be short. 
     Compared to 3D chassis measuring device that are permanently installed in front of the measurement station, the advantages result that no additional cameras are required on the adjustment or calibration device, and that the distance between the adjustment or calibration device and the motor vehicle need not be determined manually e.g. using a tape measure. 
     In summary, the method, according to the invention, for adjusting or calibrating a vehicle surroundings sensor is therefore easy to carry out, and the adjustment or calibration system according to the invention is easy to operate and is cost effective. 
     According to an advantageous embodiment in which the distance of the vehicle surroundings sensor adjustment or calibration element to the front axle is also determined, a dynamic distance measurement is made possible, and a manual measurement of distance between the adjustment and calibration device and the motor vehicle is eliminated, which often must be carried out when using chassis measuring devices having CCD technology, in which conventional units must be adapted to the vehicle wheel using clamping units. 
     The advantageous developments of the vehicle surroundings sensor adjustment or calibration system, and the further resultant advantages that are described below also result in a similar manner for the method, according to the invention, for adjusting or calibrating a vehicle surroundings sensor, and these are to be explicitly considered to also be disclosed. To prevent repetition, these method-based developments and the associated advantages will not be repeated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in the following in greater detail using embodiments, with reference to the attached  FIGS. 1 through 3 . 
         FIG. 1  shows a schematic diagram of a first vehicle surroundings sensor adjustment or calibration system according to an embodiment of the invention; 
         FIG. 2  shows a second vehicle surroundings sensor adjustment or calibration system according to a second embodiment of the invention; and 
         FIG. 3  shows a schematic diagram of a third vehicle surroundings sensor adjustment or calibration system according to a third embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a schematic diagram of a first vehicle surroundings sensor adjustment or calibration system  2 . 
     First vehicle surroundings sensor adjustment or calibration system  2  includes a motor vehicle  7  that is situated on running rails  4  and  6  of a measurement station having a chassis measuring device. To simplify the depiction, only wheels  8 ,  10 ,  12  and  14  of vehicle  7  are shown, and the dimensions of the body of vehicle  7  are indicated merely using a dotted outline. The front axle and rear axle of motor vehicle  7  are indicated using dashed transverse lines. Geometric driving axis  64  is shown as a dashed arrow that extends from the center point of the rear axle to the center point of the front axle. Approximately in the center of its front side, the motor vehicle includes a vehicle surroundings sensor  15  that should be adjusted or calibrated using first vehicle surroundings sensor adjustment or calibration system  2 . 
     Chassis measuring device includes targets  16 ,  18 ,  20  and  22  that are fastened to wheels  8 ,  10 ,  12  and  14  of motor vehicle  7  using quick clamping units  24 ,  26 ,  28  and  30 , and a left measuring unit  32  and a right measuring unit  46  that are fastened to running rails  4  and  6  using fastening adapters  34  and  48  approximately in the center relative to the longitudinal extension of running rails  4  and  6 , and extend outwardly therefrom. Targets  16  through  22  are disk-shaped in design and point outwardly. The main direction of extension of targets  16  through  22  can extend in a perpendicular plane through the rotational axis of wheels  8  and  10 , and  12  and  14 , as shown in  FIG. 1  as an example. 
     Left measuring unit  32  includes an outer, forward-pointing measurement camera  36 , an inner, forward-pointing measurement camera  38 , an outer, rearward-pointing measurement camera  40 , and an inner, rearward-pointing measurement camera  42 . In a similar manner, right measuring unit  46  includes an inner, forward-pointing measurement camera  50 , an outer, forward-pointing measurement camera  52 , an inner, rearward-pointing measurement camera  54 , and an outer, rearward-pointing measurement camera  56 . The field of vision of rearward-pointing measurement cameras  40  and  42  of left measuring unit  32 , and the field of vision of rearward-pointing measurement cameras  54  and  56  are each dimensioned such that they fully encompass left rear target  20  and right rear target  22 . 
     Measuring units  32  and  46  shown in  FIG. 1  are mobile measuring units that are hung on running rails  4  and  6  using fastening adapters  34  and  52 , or are screwed together with running rails  4  and  6 . A magnet adaption is likewise possible. Basically, measuring units  32  and  46  can be connected to running rails  4  and  6  in any suitable manner. The advantage of providing detachable connections is that measuring units  32  and  46  can be easily removed and used at other workstations. 
     Measuring units  32  and  46  include cross-referencing that, in the figure, is embodied as cross-reference cameras  44  and  58  that point in the transverse direction of the vehicle and detect optical features on the particular opposite running rail or measurement units  32  and  46  to thereby determine the position of measuring units  32  and  46  relative to each other. For example, the optical features can be designed as LEDs on diametrically opposed cross-reference cameras  44  and  58 . Cross-reference cameras  44  and  58  are disposed above or below running rails  4  and  6 , but definitely underneath the bottom of motor vehicle  7 , such that the transverse line of sight is unrestricted. 
     Furthermore, measuring units  32  and  46  can also include tilt sensors, which are not depicted here, and which are used to determine the tilt of measuring units  32  and  46 . The line of sight used for cross referencing between transverse reference cameras  44  and  58  is depicted in  FIG. 1  using a dotted transverse line. 
     Targets  16  and  18  are shown as dashed lines on front wheels  8  and  10 . 
     A frame  60  is disposed in front of the measurement station, which is oriented transversely to the vehicle and extends from a width position left of left running rail  4  to a width position right of right running rail  6 . Receptacles, which are not shown in  FIG. 1 , are disposed on the lateral ends of frame  60 , into which targets  16  and  18  of front wheels  8  and  10  can be inserted. 
     Two arrows are used in  FIG. 1  to show how targets  16  and  18  of front wheels  8  and  10  are removed therefrom and are attached to lateral receptacles in frame  60 . 
     A vehicle surroundings sensor adjustment or calibration target  62  is disposed on rearward-pointing side of frame  60 , which extends approximately from a width position that corresponds to the right end of left running rail  4 , to a width position that corresponds to the left end of right running rail  6 . 
     The focal distance of forward-pointing measurement cameras  36  and  38  of left measuring unit  32 , and the focal distance of forward-pointing measurement cameras  50  and  52  of right measuring unit  46  can each be changed such that targets  16  and  18  attached to front wheels  8  and  10  are located entirely within their field of vision, and such that targets  16  and  18  disposed in lateral receptacles of frame  60  are located entirely within their field of vision, as indicated in  FIG. 1  using dotted lines. 
     The vehicle surroundings sensor adjustment or calibration systems shown in  FIGS. 1 through 3  also include a not-shown data processing unit or evaluation unit that receive signals from the measurement cameras or the reference cameras and the vehicle surroundings sensor and determine the relevant chassis parameters on the basis of these signals. 
       FIG. 2  shows a second vehicle surroundings sensor adjustment or calibration system  68 . 
     Second vehicle surroundings sensor adjustment or calibration system  68  differs from first vehicle surroundings sensor adjustment or calibration system  2  in that the vehicle surroundings sensor is disposed in the center of rear end of motor vehicle  7 , frame  72  having forward-pointing vehicle surroundings sensor adjustment or calibration target  74  is disposed behind motor vehicle  7 , and rear targets  20  and  22  are moved from the position on rear wheels  12  and  14  indicated using dashed lines to the lateral receptacles in frame  72 . 
     Accordingly, the fields of view of forward-pointing cameras  36  and  38  of left measuring unit  32 , and forward-pointing cameras  50  and  52  of right measuring unit  46  are dimensioned such that they fully encompass front targets  16  and  18 . The focal distances of rearward-pointing cameras  40  and  42  of left measuring unit  32 , and of rearward-pointing cameras  54  and  56  of right measuring unit  46  can be adjusted such that rear targets  20  and  22  are located entirely within the field of vision of cameras  40 ,  42 ,  54  and  56  when they are attached to rear wheels  12  and  14 , and when they are attached to the lateral receptacles in frame  72 . 
       FIG. 3  shows a schematic diagram of a third vehicle surroundings sensor adjustment or calibration system  76 . 
     Third vehicle surroundings sensor adjustment or calibration system  76  differs from first vehicle surroundings sensor adjustment or calibration system  2  in that vehicle surroundings sensor  78  is placed in a right front corner region of motor vehicle  7 , frame  80  and vehicle surroundings sensor adjustment or calibration target  82  located on its front side is designed slightly smaller than in  FIG. 1 , and frame  80  and target  82  are disposed in a position to the right in front of motor vehicle  7  having an oblique orientation. 
     Arrows are likewise used in  FIG. 3  to indicate how the positions of front targets  16  and  18  are switched between front wheels  8  and  10 , and the lateral receptacles in frame  80 . There is no line of sight between forward-pointing cameras  36  and  38  of left measuring unit  32  and front left target  16  disposed in left receptacle in frame  80  since there is a motor vehicle  7  disposed therebetween. However, targets  16  and  18  that are placed on frame  80  are located in the field of vision of forward-pointing cameras  50  and  52  of right measuring unit  46 . To this end, the focal distance and field of vision of cameras  50  and  52  can be changed such that right front target  18  disposed on right front wheel  10  is situated entirely in its field of vision, and targets  16  and  18  disposed in lateral receptacles in frame  80  are situated entirely in their fields of view. 
     The method for adjusting or calibrating vehicle surroundings sensor  15  of motor vehicle  7  is explained below in detail: 
     Using clamping units  24  through  30 , targets  16  and  18  are fastened to front wheels  8  and  10 , and targets  20  and  22  are fastened to rear wheels  12  and  14  of motor vehicle  7 , wherein, in the simplest embodiment, it is sufficient to only attach targets  20  and  22  to rear wheels  12  and  14  of motor vehicle  7  because this enables the geometric driving axis of motor vehicle  7  to be determined very accurately. 
     Measuring units  32  and  46  are then fastened to running rails  4  and  6  using fastening adapters  34  and  48 , if they are not already located there. 
     Next, targets  16  and  18  are recorded by forward-pointing measurement cameras  34 ,  36 , and  50  and  52 , and rear targets  20  and  22  are recorded by rearward-pointing measurement cameras  40 ,  42  and  54 ,  56 . Targets  16 ,  18 ,  20  and  22  are then rotated into a second target position, either by displacing the motor vehicle on running rails  4  and  6 , or by rotating targets  16  through  22  relative to wheels  8  through  14  which remain fixed in position. Targets  16  through  22  are now recorded once more by measurement cameras  36  through  42  and  50  through  56 . On the basis of these recorded images of targets  16  through  22 , the data processing unit can now determine vehicle axis  64 , and it is sufficient to consider targets  20  and  22  on rear wheels  12  and  14 , as mentioned previously. 
     Next, front targets  16  and  18  are removed from front wheels  8  and  10 , and are attached to lateral receptacles in frame  60 . Targets  16  and  18  on frame  60  are then recorded once more by forward-pointing cameras  36  and  38 , and  50  and  52 ; targets  16  and  18  are then rotated on the frame, and an image of targets  16  and  18  is then captured again by cameras  36 ,  38  and  50 ,  52  in the second rotated target position. 
     The data processing unit can now determine the angular position of vehicle surroundings sensor adjustment or calibration element  62  relative to vehicle axis  64 . 
     Vehicle surroundings sensor adjustment or calibration element  62  can then be aligned relative to vehicle axis  64  and, in a subsequent step, it can be adjusted or calibrated. 
     If the distance of targets  16  and  18  to measuring units  32  and  46  and, therefore, to the front axle of the motor vehicle, is also determined, the data processing unit can also determine the position of vehicle surroundings sensor adjustment or calibration element  62  relative to front axle  64  of motor vehicle  7 , and, in fact, on the basis of vehicle axis  64  that was determined and the distance of targets  16  and  18  to motor vehicle  7  that was determined, and on the basis of the angular position, that was determined, of vehicle surroundings sensor adjustment or calibration element  62  relative to vehicle axis  64 . 
     The method for adjusting or calibrating vehicle surroundings sensor  70  of second vehicle surroundings sensor adjustment or calibration system  68  proceeds analogously, except that, in this case, rear targets  20  and  22  are removed from rear wheels  12  and  14  and are attached to lateral recesses in frame  72  disposed behind motor vehicle  7 , and that targets  20  and  22  are recorded in two target positions by rearward-pointing cameras  40  and  42 , and  54  and  56 . 
     The method for adjusting or calibrating vehicle surroundings sensor  78  likewise proceeds analogously to the method for adjustment or calibrating vehicle surroundings sensor  15  of first vehicle surroundings sensor adjustment or calibration system  2 , although in this case targets  16  and  18  disposed in lateral recesses in frame  80  are each recorded in two target positions by forward-pointing measurement cameras  50  and  52  of right measuring unit  46 .