Abstract:
A sensor for a vehicle includes a sensor housing, a surface of which sensor housing has at least three areas defining at least three reference measuring fields. Positions of the at least three reference measuring fields define a reference plane. The reference measuring fields have (i) a surface texture which enables tactile position determination of the reference measuring fields, and/or (ii) a surface characteristic which enables optical position determination. The detected positions of the reference measuring fields are used to define the reference plane. A mechanical sensor axis of the target sensor is defined as extending orthogonally to the reference plane. The mechanical sensor axis is used to (a) ascertain an angle of deviation between the mechanical sensor axis and a known sensor axis of the sensor, and/or (b) align the mechanical sensor axis to a travel axis of the vehicle.

Description:
BACKGROUND INFORMATION 
     The manufacture of radar sensors for vehicles is subject in particular to the tolerances of the used mechanical components on or in which the antennas of the radar components are mounted. This typically results in a mechanical sensor axis and a radar sensor axis that deviate from one another. 
     The radar sensor is assembled in the vehicle so that the radar axis is aligned at a precisely defined angle with respect to the travel axis. This may be performed in two ways in particular. 
     The sensor is installed on the vehicle and is in operation. This means that it is transmitting radar waves. Actual value α of the azimuth angle and the elevation angle of the radar axis in relation to the travel axis of the vehicle is ascertained from the reflected radar intensities. Deviations from the setpoint value, i.e., the angle between the radar axis and the travel axis, are corrected with the aid of adjusting means on the radar sensor holder or on the radar sensor itself. This type of adjustment may also be referred to as an active adjustment. 
     In particular, it is disadvantageous that a radar sensor must be in operation for the adjustment and in this respect transmits radar waves that may interfere with electrical consumers, for example. 
     For the second type of adjustment which may also be referred to as a passive adjustment, a mirror adhered to or vapor-deposited on the radar sensor is additionally used. At the radar sensor manufacturing plant, an angle deviation β between the radar axis and a mirror normal is ascertained and stored in the sensor. A deviation y of the mirror normal with respect to the travel axis is then measured by the vehicle manufacturer. The stored values are read out, calculated, and taken into consideration as correction factors. The radar axis is corrected to the travel axis via an adjustment. 
     It is disadvantageous in particular that the mirror position may change over time due to aging of the adhesive foil. In particular, the properties of the adhesive foil under the mirror change over the service life of the sensor. For example, it becomes brittle due to high temperatures or swells due to high humidity. As a result, the originally measured and stored deviations of the radar axis and the mirror normal no longer match the actual values. As a result, passive adjustment is not possible in a service case, i.e., in particular during a function test of the radar sensor. 
     Moreover, the reflectivity may decrease due to contamination of and/or oxidation of and/or mechanical influences on the reflective layer. A passive adjustment may not be reliably ensured in a service case. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is therefore to provide a sensor, an adjusting method, and a measuring method that overcome the known disadvantages and allow correct adjustment in a service case. 
     According to one aspect of the present invention, a sensor including a sensor housing is provided. Moreover, at least three reference measuring fields situated on the sensor housing are provided. The three reference measuring fields are preferably separated from one another, in particular parallel to one another. A reference plane may be formed with the aid of the three reference measuring fields. A normal to the reference plane is defined as a mechanical sensor axis. 
     According to another aspect, an adjusting method for a sensor situated in a vehicle including a sensor housing is provided, a reference plane being formed with the aid of at least three reference measuring fields in such a way that a mechanical sensor axis runs orthogonally to the reference plane. The mechanical sensor axis is then aligned relative to a travel axis of the vehicle. 
     According to another aspect, a measuring method for a sensor including a sensor housing is provided, a reference plane being formed with the aid of at least three reference measuring fields in such a way that a mechanical sensor axis runs orthogonally to the reference plane. An angle deviation between the mechanical sensor axis and a sensor axis is then ascertained. The measuring method may preferably be performed at a sensor manufacturing plant. In this respect, the measuring method may also be referred to as an industrial measuring method, for example. 
     With the aid of the three reference measuring points, it is advantageously possible to reliably determine the mechanical sensor axis at any time over the entire service life of the sensor. No special reflective surfaces, e.g., mirrors or corresponding vapor depositions, are needed. Angle deviations between the sensor axis and the mechanical sensor axis measured at a manufacturing plant and stored in the sensor advantageously do not change over the service life and thus remain valid. A quick and particularly cost-effective adjustment in a service case is thus possible. 
     The sensor is preferably a wave sensor. This means that it transmits physical waves that may be reflected by objects or obstacles. The sensor preferably receives the reflected physical waves and may detect them. For this purpose, the sensor has a corresponding transmitter and/or a corresponding receiver or detector. A sensor axis is defined in particular as an axis parallel or collinear to a wave vector             corresponding to the propagating wave transmitted by the sensor.
     According to one specific embodiment, the sensor is a radar sensor and/or an ultrasound sensor. This means that the sensor transmits radar waves and/or ultrasound waves. Therefore, a distance between a vehicle and an object preceding the vehicle, e.g., a preceding vehicle, may thus be detected in an advantageous manner. In this case a sensor axis is defined in particular as an axis parallel or collinear to a wave vector             of the radar wave or the ultrasound wave. In the case of a radar wave that is an electromagnetic wave, wave vector           is perpendicular to E-field vector           and perpendicular to B-field vector          . In the case of a radar sensor, the sensor axis may also be referred to as a radar sensor axis. In the case of an ultrasound sensor, the sensor axis may also be referred to as an ultrasound sensor axis.
     According to one specific embodiment, at least one reference measuring field is designed for tactile and/or optical position determination. As a result, the position of the reference measuring field may be determined tactilely in an advantageous manner with the aid of a scanner or several scanners. In particular, the position of the reference measuring field may be determined optically in an advantageous manner with the aid of a laser. All three reference measuring fields are preferably designed for tactile and/or optical position determination. In particular, the reference plane may be defined in a particularly simple manner with the aid of the measured positions of the three reference measuring fields. 
     According to another specific embodiment, at least one reference measuring field includes a flat surface. In this case, the reference measuring field may also be referred to as a reference measuring surface. In particular, the reference measuring field is formed as a flat surface. All three reference measuring fields are preferably formed as a flat surface. In particular, the three flat surfaces are situated parallel to one another, and the three flat surfaces are preferably on one plane. In general, the reference measuring fields may be situated in particular on a common plane, preferably when the three reference measuring fields are situated parallel to one another. According to another specific embodiment, the surface may be rough and/or reflective. This allows more precise and simpler optical and/or tactile position determination in particular. 
     According to another specific embodiment, at least one reference measuring field is an integral part of the sensor housing. All three reference measuring fields are preferably an integral part of the sensor housing. The reference measuring field or the reference measuring fields is/are preferably integrated into the sensor housing. As a result, it is advantageously possible that the reference measuring fields may be formed during the manufacture of the sensor in/on the sensor housing so that a particular position of the reference measuring fields advantageously does not change over time, in particular over the service life of the sensor. The reference measuring field or reference measuring fields is/are preferably situated directly on a dome, in particular a radome or mounting dome, and/or on a sensor lens. The sensor housing preferably has several, preferably four, domes, in particular radomes or mounting domes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an active adjustment in a known sensor. 
         FIG. 2  shows a passive adjustment in another known sensor. 
         FIG. 3  shows an oblique view of a sensor according to the present invention. 
         FIG. 4  shows a side view of the sensor from  FIG. 3 . 
         FIG. 5  shows a schematic view of another sensor according to the present invention. 
         FIG. 6  shows a flow diagram of an adjusting method. 
         FIG. 7  shows a flow diagram of a measuring method. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a side view of a sensor  101  according to the related art. Sensor  101  includes a square sensor housing  103  having a sensor lens cover  105 . Sensor lens cover  105  has a concave area  107 . Sensor lens cover  105  also has two tabs  109  that may engage in corresponding receptacles or projections  111  on sensor housing  103  so that sensor lens cover  105  is attached to housing  103 . Sensor housing  103  also has four adjusting means  113  which are situated on the four corners of sensor housing  103 . Adjusting means  113  are also designed to secure sensor housing  103  in or on a vehicle (not shown). For example, adjusting means  113  may include screws so that a distance between the corresponding corner of sensor housing  103  and the corresponding attachment position in the vehicle may be set. This setting option is represented by a double arrow  114 . 
     A travel axis of the vehicle identified by reference numeral  115  is also shown. In general, a travel axis of the vehicle is the axis along which the vehicle moves forward or backward. A sensor axis is identified by reference numeral  117 . An angle α identifies an angle deviation between travel axis  115  and sensor axis  117 . Only an angle deviation α in relation to the figure plane is shown in  FIG. 1 . An angle deviation in relation to a plane perpendicular to the figure plane may occur. Angle deviation α identifies an azimuth angle and/or an elevation angle of sensor axis  117  in relation to travel axis  115 . 
     In the case of an active adjusting method, sensor  101  is installed on the vehicle and is in operation, i.e., it transmits physical waves. Angle deviation α of the azimuth angle and the elevation angle of the sensor axis in relation to the travel axis are ascertained from the reflected wave intensities. Angle deviation α may also be referred to as an actual value. Deviations from a setpoint value (angle between sensor axis  117  and travel axis  115 ) may be corrected with the aid of adjusting means  113 . 
       FIG. 2  shows a side view of another known sensor  201 . Sensor  201  has an identical design to that of sensor  101  from  FIG. 1 . Moreover, sensor  201  includes a mirror  203 , which is adhered to sensor lens cover  105 . However, mirror  203  may also be vapor-deposited on sensor lens cover  105 . 
     An angle deviation β between sensor axis  117  and a mirror normal  205  is ascertained at a sensor manufacturing plant and is stored in sensor  201 . A deviation Y of mirror normal  205  and travel axis  115  is measured at a vehicle production plant. The stored values, in particular angle deviation β, are read out, calculated, and taken into consideration as correction factors. Sensor axis  117  is corrected to travel axis  115  with the aid of adjusting means  113 . 
       FIG. 3  shows an oblique view of the front of a sensor  301  according to the present invention. Sensor  301  includes an octagonal sensor housing  303  having an octagonal sensor lens cover  305 . Sensor lens cover  305  has a concave area  307  curving away from sensor housing  303 . The octagonal specific embodiment shown here is only an example and is not limiting. According to other specific embodiments (not shown), a square shape, in particular a quadratic shape, preferably a rectangular shape, may be provided. In particular, a circular shape may also be provided. Sensor housing  303  and cover  305  are preferably made of plastic. 
     Sensor lens cover  305  also includes a planar area  309 , which surrounds concave area  307 . Reference measuring fields  313   a ,  313   b , and  313   c  are situated in three corner areas  311   a, b, c , respectively, in planar area  309 . Reference measuring fields  313   a ,  313   b , and  313   c  are preferably designed as a flat surface. In particular, reference measuring fields  313   a, b, c  are designed for optical and/or tactile position determination so that a position of corresponding reference measuring field  313   a ,  313   b , and  313   c  may be detected. For example, reference measuring fields  313   a, b, c  may have a rough surface and/or a reflective surface. Therefore, the position of a defined point on the three reference measuring fields  313   a ,  313   b , and  313   c  may be measured in particular with the aid of scanners or optical tools, such as a laser, so that a reference plane is defined in an advantageous manner. Such a point may also be referred to as a reference measuring point. Sensor  301  is preferably fixedly positioned in a defined position. Reference measuring fields  313   a, b, c  preferably have a surface of at least 25 mm 2 . Reference measuring fields  313   a, b, c  are preferably rectangular, preferably quadrangular, and preferably have a length of 5 mm and a height of 5 mm. According to another specific embodiment, reference measuring fields  313   a, b, c  may also be formed differently. This means in particular that reference measuring field  313   a  may have a rough surface, for example, and reference measuring fields  313   b  and  313   c  may have a reflective surface. They may also differ with respect to shape and size, for example. 
     Sensor housing  303  also includes four adjusting means  315  whose height is adjustable, for example with the aid of screws. Adjusting means  315  are also used to secure sensor housing  303  and thus sensor  301  in or on the vehicle. In this respect, adjusting means  315  may also be referred to as fastening means. Analogously to sensors  101  and  202 , sensor lens cover  305  includes on two opposite sides two tabs or snap-in pins  317 , which may engage in corresponding locking protrusions  319  of sensor housing  303 , so that cover  305  is securely fastened to housing  303 . 
     As is apparent in  FIG. 3 , reference measuring fields  313   a, b, c  have a circular shape. Moreover, sensor lens cover  305  has a fourth reference measuring field  313   d  situated in a fourth corner area  311   d . A particularly sensitive and precise definition of the reference plane is made possible by a fourth reference measuring field. 
       FIG. 4  shows a side view of sensor  301  from  FIG. 4 . An adjustment option is shown here by double arrow  317 . Reference plane  319  defined by the four reference measuring fields  313   a, b, c, d  is also shown. A normal to reference plane  319  is identified by reference numeral  321  and corresponds to a mechanical sensor axis. A sensor axis is identified by reference numeral  323 . An angle deviation between sensor axis  323  and mechanical sensor axis  321  is identified by δ. 
     Angle deviation δ between sensor axis  323  and mechanical sensor axis  321  is ascertained at a sensor manufacturing plant in particular and stored in sensor  301 . At a vehicle manufacturer or a maintenance company performing a function test of sensor  301 , for example, a deviation between mechanical sensor axis  321 , i.e., the normal of reference plane  319 , and a travel axis (not shown) is measured. The stored values, in particular deviation δ, are read out, calculated, and taken into consideration as correction factors. Sensor axis  323  may be aligned to the travel axis with the aid of the adjusting means. 
     Both when ascertaining angle deviation δ and when ascertaining the deviation between mechanical sensor axis  321  and the travel axis, reference plane  319  is formed with the aid of four reference measuring fields  313   a, b, c, d  in that a corresponding position of reference measuring fields  313   a, b, c, d  is detected in particular with the aid of optical and/or tactile measuring methods. Sensor  301  is preferably designed as a radar sensor. 
       FIG. 5  shows another sensor  501  according to the present invention. The sensor includes a sensor housing  503 , which has three reference measuring fields  505 . Sensor  501  is designed as a radar sensor. 
       FIG. 6  shows a flow diagram of an adjusting method for a sensor situated in a vehicle including a sensor housing. For example, this may be a sensor  301  or  501 . A reference plane is formed in a first step  601  with the aid of at least three reference measuring fields, a mechanical sensor axis running orthogonally to the reference plane. The mechanical sensor axis is aligned relative to a travel axis in a subsequent step  603 . 
       FIG. 7  shows a flow diagram of a measuring method for a sensor including a sensor housing. For example, this may be a sensor  301  or  501 . A reference plane is formed in a first step  701  with the aid of at least three reference measuring fields, a mechanical sensor axis running orthogonally to the reference plane. An angle deviation between the mechanical sensor axis and a sensor axis is ascertained in a subsequent step  703 . According to one specific embodiment (not shown), this angle deviation may be stored in the sensor and used as a correction factor in the adjusting method according to the present invention. 
     In summary, a core of the present invention is to provide a sensor having at least three reference measuring fields, the reference measuring fields being able to be situated preferably on the radome and/or a sensor lens so that a mechanical sensor axis may be determined reliably at any time over the service life. The position of the three reference measuring fields is selected in particular in such a way that they do not change their position with respect to the sensor axis over the service life. In contrast to the related art, no particularly reflective surfaces, such as mirrors or vapor depositions, are needed, so such a mirror may advantageously be dispensed with. As a result, costs and materials are saved in particular. The originally stored values regarding the deviations remain valid in particular over the service life of the sensor. Since it is possible to determine the reference plane using three reference measuring fields, the adjusting method may also be referred to as a 3-point adjusting method. The measuring method may also be referred to as a 3-point measuring method. The sensor is preferably designed as a radar sensor, preferably as a medium-range radar sensor. According to further preferred specific embodiments, the sensor may also be designed as a short-range radar sensor, a medium-range radar sensor, or as a long-range radar sensor. The measuring method and the adjusting method may be applied or performed accordingly using the above-mentioned sensors.