Patent Publication Number: US-11034200-B2

Title: Device for detecting the position of a first or second vehicle to be coupled together

Description:
FIELD OF THE INVENTION 
     The invention relates to a device for detecting the position of a first or second vehicle to be coupled together, having a sensor device which can be arranged on the first or second vehicle and which detects at least one reference point of the other second or first vehicle using sensors. 
     BACKGROUND OF THE INVENTION 
     The first and second vehicle are releasably joined together by compatible coupling means, the first vehicle being the hauling vehicle and for this purpose generally being equipped with an engine to propel it. The second vehicle or vehicles are then a nondriven trailer vehicle, which is hauled by the first vehicle. The first vehicle for example may be a tractor with a fifth wheel and the second vehicle a trailer with a kingpin. Such connected first and second vehicles are also known as an articulated vehicle. Alternatively, the first vehicle may also be a motor car with a pin coupling arranged at its rear end and the second vehicle may be a drawbar trailer with a drawbar eye formed at the end of the drawbar. First and second vehicles coupled together in this way are also called an articulated train. Furthermore, hybrid forms are also conceivable, in which for example the first vehicle is a tractor, with a semitrailer coupled directly to it, and a drawbar trailer coupled to the latter. In an isolated consideration of trailer vehicles, the pulling vehicle, such as the semitrailer, would be the first vehicle and the pulled vehicle, such as the drawbar trailer, would be the second vehicle. 
     There have already been efforts to have the aforementioned vehicles drive autonomously at a depot, that is, without the presence of a driver in the first vehicle. DE 103 22 765 B4 discloses one such automated depot for autonomously driving vehicles. The autonomous driving also includes an automated coupling and uncoupling of the first and second vehicle. The depot may furthermore be equipped with an automatic filling station and/or with an automatic washing station, in order to fuel and wash the respective vehicles as needed. 
     From DE 10 2006 057 610 A1 there is already known an assistance system which is supposed to help the driver in coupling, docking, or driving of the first vehicle under a target object. By a target object is meant a trailer, semitrailer, swap body or loading ramp. The known assistance system comprises basically an image sensor and a calculating unit, with the aid of which the target object height is supposed to be set at the first vehicle. Thus, for example, a particular target object can be recognized by a scene analysis and be coordinated with memorized model data, so that at least an approximate target object height is preset at the first vehicle before the actual coupling is done. The known assistance system, however, is based solely on an image sensor, which provides an image of the second coupling means to an electronic controller, which in turn is supposed to identify the second coupling means with a suitable software. But object recognition by means of an image sensor has proven to be not very reliable, since it is particularly sensitive to changing light conditions and the unavoidable dirt and grime during operation. The becomes especially disadvantageous in the case of autonomously maneuvering vehicles, when no driver is present to intervene in the coupling process. 
     SUMMARY OF THE INVENTION 
     Therefore, the problem which the invention proposes to solve was to provide a device for detecting the position of a first or second vehicle being coupled together that makes possible a reliable and precise coupling independently of prevailing environmental influences. 
     This problem is solved according to the invention by the characterizing features of wherein the sensor device has at least one transceiver unit, and on the at least one reference point there can be fastened a transponder, which reflects a radio signal of the transceiver unit. With the aid of a radio-based locating, the transceiver unit detects the transponder situated in its metered spatial region. The transponder is coordinated with a defined position in regard to the transceiver unit of the other vehicle and is detected by the transceiver unit. The locating results from a measuring of the travel time of radio signals, initiated by the transceiver unit, which signals are received, processed, and reflected by the transponder. From the measurement of the travel time of the radio signal, the direct distance from the transponder to the transceiver unit can be determined in real time. 
     Advantageously, additional information about the vehicle or the type of vehicle to which the transponder is permanently fastened can be stored in the transponder. The vehicle type defines whether the second vehicle is a semitrailer with a kingpin or a drawbar trailer with a drawbar eye formed at the end of the drawbar. In this way, one can prevent, for example, a tractor in autonomous driving mode from wrongly trying to couple onto a drawbar trailer. 
     By a transponder is meant a radio communication device that receives incoming signals and automatically answers or relays them onward. According to the invention, both passive transponders and active transponders can basically be used. Passive transponders draw their energy needed for the communication and the working off of their internal processes exclusively from the read/write unit, in the present case the transceiver unit(s). Passive transponders do not require any power supply of their own and they can work at the comparatively short distances prior to the coupling of the first and second vehicle. The best-known kind of a passive transponder is radio frequency identification RFID. The core of such a passive transponder is the built-in RFID chip. 
     Active transponders have their own power supply. Either they have a built-in battery or they are connected to an outside power grid. Not only does this make possible larger communication ranges, but also the managing of rather large data storages and the operation of integrated sensors can be realized. Due to the need for a power supply in the case of active transponders, one will preferably always resort to passive transponders whenever no additional data needs to be transmitted to the transceiver unit, for example from other sensors connected to the active transponder. 
     Preferably, multiple reference points are present on the other second or first vehicle, at each of which there can be secured a transponder, and each transponder encodes the echo individually such that it can be distinctly coordinated with the particular transponder. The accuracy of the locating can be made more precise if the multiple transponders situated at the respective reference points are arranged at a known distance from one another. In a fleet of vehicles, this distance from the transponder to the vehicle being detected can always be chosen to be the same and can be stored in the transceiver unit. 
     Advantageously the sensor device comprises an electronic controller, which calculates from the travel time of the radio signal the direct distance to the at least one transponder. The electronic controller can either be integrated in the transceiver unit and form an integral component with it or it can be arranged as a separate component on the vehicle. The electronic controller can provide a control signal to the first vehicle based on the measurement of the travel time of the radio signal to the transponder(s), by which the control of the vehicle can be influenced. The control of the vehicle includes a manipulation of the transmission, the engine controls, the steering, the level regulation (air suspension) and/or the brake. 
     It has been found to be particularly favorable when the sensor device comprises at least one antenna which is connected to the respective transceiver unit. Via the antenna, the radio signal of the transceiver unit is emitted and the echo reflected from the transponder(s) is received. Insofar as multiple transceiver units are present, each of the transceiver units can have its own antenna. Usually the antenna is integrated in the respective transceiver unit and forms a common component with it. 
     Preferably the transceiver unit sends and receives a radar signal via the antenna, while advisedly the radio signal is a radar signal in a frequency range of 1 GHz to 10 GHz, especially preferably 4 GHz to 7 GHz, most especially preferably 5 GHz to 6 GHz. 
     The invention also relates to a road train, wherein the road train comprises a first and at least one second vehicle. According to a first preferred embodiment, the sensor device comprises a transceiver unit situated on the first vehicle and at least one transponder situated on the second vehicle. In this way, an at least two-dimensional locating of the second vehicle can be realized during the approach of the first vehicle prior to the coupling. Therefore, the road train in particular involves articulated vehicles whose drawbar trailers are parked free standing and without support elements, such as support jacks, so that the drawbar of the parked second vehicle also remains in a relatively narrow spatial framework and is docked with the pin coupling of the first vehicle during the next coupling event. 
     According to an alternative, second embodiment, a second transceiver unit with a second antenna is arranged in a vertical height clearance from the transceiver unit and is connected to the electronic controller. The two controllers detect the transponder or transponders of the second vehicle and make possible a detecting of its position, especially also its height condition, by means of cross pinpointing or triangulation. Suitable road trains may be both articulated vehicles and also semitrailer trains or hybrid forms of the two. In the case of the latter mentioned semitrailer trains, the front end of the uncoupled semitrailer is supported by support jacks, whereby the height condition of the front end may vary greatly. Thanks to a three-dimensional locating by two transceiver units, semitrailers can also be picked up and coupled especially accurately by autonomous driving tractor vehicles. 
     According to an alternative, third embodiment, an active transponder is situated at the end of the second vehicle facing toward the first vehicle, wherein the active transponder is connected to a height measuring sensor and the measurement signal of the height measuring sensor together with its individual encoding is relayed to the transceiver unit. In this embodiment, the height condition of the coupling means situated on the second vehicle is determined by a height measuring sensor situated for this on the second vehicle, instead of by a second transceiver unit, and a three-dimensional orientation of the second vehicle is determined in this way. The height measuring sensor may be an infrared sensor, ultrasound sensor, laser range finder or mechanical encoder, which determine the extended state of the support jacks and use a potentiometer to put out an electrical voltage varying in dependence on the extended state. The measurement signal of the height measuring sensor, if the latter is connected to an active transponder, is relayed together with its encoding to the transceiver unit. The road trains may be articulated vehicles or semitrailer trains or hybrid forms of the two. 
     Advantageously, the second vehicle comprises a coupling means, which can be in particular a kingpin fastened to the second vehicle. The kingpin is connected firmly to the semitrailer on its bottom side and when coupled onto a first vehicle it is received and locked by its fifth wheel. 
     Favorably, the kingpin comprises a fastening flange, an upper collar connected to the latter at the bottom, a small-diameter locking section and a lower collar, wherein a first recess is made in a bottom side of the lower collar, in which a first transponder is installed. This affords the advantage that the transponder is not surrounded by the steel of the kingpin at the bottom and accordingly it is favorably detected by the transceiver unit(s). Moreover, in the recess the transponder is effectively protected from mechanical influences and not exposed to any wear-related perturbation. The transponder may be additionally evacuated by a plastic in the recess, in particular, covered by a plastic casting compound. 
     Advisedly, the recess is arranged in the swivel axis of the kingpin. Consequently, the transponder is also always situated in the vehicle lengthwise axis of the second vehicle and helps position an autonomously approaching first vehicle likewise in the vehicle lengthwise axis of the second vehicle. 
     Preferably, a trailer plate is formed on a bottom side of the second vehicle, which in the coupled condition is supported on a fifth wheel, wherein a second recess is formed in the trailer plate, in which a second transponder is installed. The trailer plate generally stretches across the entire width of the semitrailer and thereby enables a largely free positioning of the second transponder. Thanks to accommodating the second transponder inside the second recess, it is not detected in the coupled state by the fifth wheel, yet it enables a detecting by the transceiver unit via the downwardly open side of the second recess prior to the coupling. The transponder can additionally be evacuated by a plastic in the recess, in particular, covered by a plastic casting compound. 
     At least one support jack can be arranged on the second vehicle, to which a third and/or fourth transponder is secured. The support jack usually has a stationary section by which the support jack is fastened on the semitrailer, and a telescopic section, at the end of which a support foot is situated, which in the extended state of the support jack makes contact with the ground. The third and/or fourth transponder can favorably be situated on the stationary section, especially if the height of this transponder is supposed to be detected by means of triangulation. Since the support jacks are mounted in pairs and symmetrically on the semitrailer, it makes sense to arrange the third transponder on a support jack and the fourth transponder on the second, opposite situated support jack, in order to obtain reference points which are laterally spaced apart from the vehicle lengthwise axis. 
     Advantageously, the electronic controller receives a signal regarding the height condition of the air suspension. The air suspension, depending on its settings, ensures a lifting of the chassis and thereby may change the height condition of the overall sensor device and hence also the height condition of the antenna(s). Changes in the extension travel of the air suspension are detected by the electronic controller, which compensates for them in relation to the actual height of the antenna(s). 
     It has proven to be especially favorable when a lowest height condition of the antenna(s) above the road level with the air suspension lowered can be entered in the electronic controller. The lowest height condition of the antenna(s) varies for the first vehicles according to the installation location and furthermore it is dependent on the manufacturer of the particular air suspension installed. After the final mounting of the antenna(s), the lowest height of the antenna(s) can be measured and manually programmed in the electronic controller as an offset. The electronic controller can then calculate the actual height of the antenna(s) from a lifting distance of the air suspension and the lowest height condition. 
     According to an alternative, fourth embodiment, the sensor device comprises a transceiver unit situated on the second vehicle and a fifth transponder is situated on the first vehicle. As compared to the previous embodiments, preferably the sensor device is not situated on the first, but instead on the second vehicle, and at least one transponder is situated on the first, instead of the second vehicle. This embodiment makes necessary an independent power supply for the second vehicle, such as a battery or a storage cell, which can also be charged permanently via a solar cell. A road train outfitted in this way corresponds to the first embodiment, yet with first and second vehicles interchanged. In this way, an at least two-dimensional locating of the first vehicle can be accomplished, wherein the measured value identified by the transceiver unit is converted in the electronic controller preferably likewise situated on the second vehicle into a distance value from the transponder(s) and this is sent wirelessly by means of a data radio transmitter to the first vehicle. The first vehicle has a corresponding data radio antenna for this. This is connected in turn to a vehicle controller, which influences the driving functions of the first vehicle and takes on the autonomous maneuvering and coupling. 
     Preferably, at least one support jack is arranged on the second vehicle with a stationary section relative to the second vehicle and a telescopic section, and a sixth transponder is secured to the telescopic section. Especially favorable is the placement of the sixth transponder on a support foot of the telescopic section. In this embodiment, in addition to the two-dimensional position detection, the height condition of the second vehicle is obtained from a measurement of the lift height by means of a support jack. Since the support jack is always secured by its stationary section on the second vehicle at the same distance from the antenna of the transceiver unit and furthermore is oriented at right angles to the trailer plate, the lift height of the support jack can be calculated by a measurement of the distance between the antenna and the sixth transponder. The major benefit of this embodiment is that both the lateral orientation of the first vehicle and the height determination of the second vehicle are done by robust transponders and no other sensor types need to be implemented and calibrated. 
     Advisedly, the first, second and/or fifth transponder is situated in the vehicle lengthwise axis of the first or second vehicle. Thanks to this arrangement, a position detection can be achieved already with one or a few transponders. 
     The coupling means may also be a drawbar eye situated at the end of a drawbar. This configuration is typically relevant to articulated trains. 
     Advantageously, a third recess is formed in the drawbar and/or in a section around the drawbar eye, in which a seventh transponder is installed. The transponder can be additionally evacuated by a plastic in the third recess, in particular, it can be covered by a plastic casting compound. For a rigid drawbar, a transponder so arranged can mark the vehicle lengthwise axis. 
     Advisedly, the second and/or first vehicle has a bodywork floor with two lower corners at its end close to the other first or second vehicle, with an eighth and ninth transponder secured at the lower corners. In this way, reference points situated far away from the vehicle lengthwise axis are measured by the transceiver unit, making possible an especially accurate position detection. 
     Preferably, the second and/or first vehicle has a roof wall with two upper corners at its end close to the other first or second vehicle, and a tenth and eleventh transponder is secured to the upper corners. In this embodiment as well, reference points with maximum lateral offset from the vehicle lengthwise axis are detected and the accuracy of the position detection is improved. Furthermore, the overall height of the second vehicle can be detected for example as additional information and provided to the first vehicle, especially for optimal adjustment of a roof spoiler. 
     It may also be the case that an add-on unit is formed at a front side of the second vehicle, sticking out in the direction of the first vehicle. In this case, a twelfth transponder can be secured to the front side of the add-on unit. Such add-on units often protrude into the standardized contour of the semitrailer or trailer front and minimize the size of the gap remaining between the first and second vehicle. By an add-on unit is meant, for example, refrigerating units. The detection of the front side of the add-on unit prevents a collision between an oversized add-on unit and portions of the first vehicle during the autonomous coupling process. 
     Favorably, at least three of the transponders are arranged at a given distance from each other, since with three reference points a plane is subtended and the position of this subtended plane serves for an especially accurate position detection of the first or second vehicle, given knowledge of other dimensions of the first or second vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding, the invention shall now be explained more closely with the aid of seven figures. There are shown: 
         FIG. 1 : a side view of a device according to a first embodiment, arranged on a tractor, with first and second receiver unit arranged on the rear wall of the driver&#39;s cabin; 
         FIG. 2 : a side view of a device according to the first embodiment, arranged on a tractor, with first and second receiver unit arranged in the area of the fifth wheel and rear axle; 
         FIG. 3 : a perspective front view of a semitrailer with transponders fastened to it; 
         FIG. 4 : a side view of a device according to a second embodiment, arranged on a tractor, with a transceiver unit at the tractor vehicle side and a height measuring sensor at the semitrailer side, prior to the coupling; 
         FIG. 5 : a side view of a device according to a third embodiment, arranged on a tractor, with transponders on the tractor and the support jack; 
         FIG. 6 : a top view of a tractor per  FIG. 5  and 
         FIG. 7 : a side view of a device according to a fourth embodiment, arranged on an articulated train. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an articulated train formed from a first vehicle  10  and a second vehicle  20  in a side view. The first vehicle  10  is in a still separated position in front of the second vehicle  20 , which is standing on its two support jacks  25 . The support jacks  25  are arranged on the second vehicle  20  on both sides of the vehicle lengthwise axis X (see  FIG. 3 ) and hold the end of the second vehicle  20  facing toward the first vehicle  10  in the height condition shown, according to their state of extension. 
     The first vehicle  10  is outfitted with an air suspension  11 , which is braced against rear axles  16  and lowers or raises the vehicle chassis  17  by the lifting distance H Luf  shown in  FIG. 2 . Depending on the lifting distance H Luft , a fifth wheel  12  located on the first vehicle  10  also changes its height condition together with the vehicle chassis  17 . For a coupling of the second vehicle  20  to the first vehicle  10 , the latter moves backwards far enough underneath the second vehicle  20  until a coupling means  21  arranged thereon in the form of a downwardly projecting kingpin  22  achieves an operative engagement with the fifth wheel  12 . 
     The kingpin  22  has an upper fastening flange  22   a , by which the kingpin  22  is firmly connected to the second vehicle  20 , especially being screwed together. Toward the bottom, the fastening flange  22   a  passes into an upper collar  22   b , which adjoins a diameter-reducing locking section  22   c . The locking section  22   c  is bounded at the bottom by a lower collar  22   d , whose diameter agrees with that of the upper collar  22   b . The locking section  22   c  engages with a locking mechanism (not shown) of the fifth wheel  12  and in this way holds the kingpin  22  in pivoting manner in the fifth wheel  12 . Immediately above the kingpin  22  there stretches a trailer plate  24 , fastened to an underside  23  of the second vehicle  20 , which lies against the fifth wheel  12  when the first and second vehicles  10 ,  20  are joined together and slides across the fifth wheel  12  when negotiating curves. 
     For a secure coupling of the second vehicle  20  to the first vehicle  10 , the fifth wheel  12  must be oriented beneath the vertical level of the trailer plate  24 , yet at the same time enable a movement of the kingpin  22  into the fifth wheel  12 , without moving across the fifth wheel  12  on account of the first vehicle  10  being lowered too much. 
     Besides the above described detecting of the height condition of the second vehicle  20 , the first vehicle  10  must also be properly oriented laterally to the kingpin  22  with its fifth wheel  12 . This is especially easily achieved when the position of the kingpin  22  and/or the entire second vehicle  20  can be ascertained with the help of individual reference points  40  defined on it. 
     For this, the vehicles  10 ,  20  are provided with a device for position detection. The device comprises, at the first vehicle  10 , a sensor device  30 , having a transceiver unit  31 , a second transceiver unit  34  and an electronic controller  32 . The two transceiver units  31 ,  34  are spaced apart from each other by a constant vertical height clearance Δh. In the present exemplary embodiment of  FIG. 1 , the transceiver units  31 ,  34  are fastened to the rear wall of a driver&#39;s cabin  18  of the first vehicle  10 . 
     On the second vehicle  20  there are arranged multiple transponders  41 ,  43   a ,  47   a ,  48   a ,  49  at defined reference points  40 , each transponder  41 ,  43   a ,  47   a ,  48   a ,  49  being detected by the transceiver units  31 ,  34 . 
     The first transponder  41  is integrated in the kingpin  22 , which is formed preferably for this purpose on an underside  22   e  of the lower collar  22   d  with a first recess  22   f . The first recess  22   f  is open at the bottom and receives the first transponder  41  therein in protected manner. The first transponder  41  is thus constantly arranged in the vehicle lengthwise axis X of the second vehicle  20  and furthermore is located in the swivel axis S running through the kingpin  22  (see  FIG. 3 ). The first transponder  41  thus also especially effectively supports the orienting of a first vehicle  10  approaching the second vehicle  20  at a slant prior to the coupling process. 
     The support jacks  25 , as can be seen especially well in  FIG. 3 , comprise a stationary section  25   a , with which the support jack  25  is secured to the second vehicle  20 , and a telescopic section  25   b  with a support foot  25   c  at its end. On the stationary sections  25   a  is secured a third and fourth transponder  43   a ,  43   b , only the third front transponder  43   a  in the plane of the drawing of  FIG. 1  being visible. The third and fourth transponders  43   a ,  43   b  arranged on the support jacks  25  are spaced apart from the vehicle lengthwise axis X especially far to the side and assist in performing an especially exact position determination of the second vehicle  20  laterally to the vehicle lengthwise axis X. 
     On the second vehicle  20  shown in  FIG. 1 , at its front end  29 , there can be seen an add-on unit  29   a , which in turn carries the twelfth transponder  49  at its front end  29   b . The twelfth transponder  49  in addition to the position determination also serves for detecting the front end  29   b  of the add-on unit  29   a  and preventing the add-on unit  29   a  from hitting the driver&#39;s cabin  18 . 
     The transceiver unit  31  has an antenna  33  and the second transceiver unit  34  has a second antenna  35 , the antennas  33 ,  35  respectively putting out a radio signal, which for example arrives at the eighth transponder  47   a  and is reflected by it. The eighth transponder  47   a  is arranged at one of the lower corners  27   a  in the transition area of the front end  29  of the second vehicle  20  to its bodywork floor  27 . 
     The respective transceiver unit  31 ,  34  identifies the corresponding radio signal reflected from the eighth transponder  47   a  and provides it to the electronic controller  32 , which calculates from it a distance to the eighth transponder  47   a . The eighth transponder  47   a , shown as an example, lies at the intersection of the distance measurements of the two transceiver units  31 ,  34 . 
     The electronic controller  32  also communicates with a vehicle controller  36 , which influences the indicated air suspension  11  and the components of the first vehicle  10  represented in  FIG. 5 , especially the engine and transmission  14 , the vehicle steering  15  and/or the brake  19 . The vehicle controller  36  provides data to the electronic controller  32  as to the current actual status, such as the lifting distance H Luft  of the air suspension  11 , so that the electronic controller  32  can correct the lowest height condition H A1min  of the antenna  33  and the lowest height condition H A2min  of the second antenna  35  by the lifting distance H Luft  and thus calculate an actual height H A1  of the antenna  33  and an actual height H A2  of the second antenna  35  with respect to the road level GOK. 
     Given the actual heights H A1 , H A2  of the antennas  33 ,  35 , a determination is made for the absolute height of the eighth transponder  47   a  and, if its height does not allow a proper driving of the first vehicle  10  underneath the second vehicle  20 , the air suspension  11  will be further regulated. 
       FIG. 2  shows another exemplary embodiment of the invention, in which the transceiver units  31 ,  34  are offset at the rear end and now are secured in the area of the rear axle  16  and on a stationary part of the fifth wheel  12 . By a stationary part of the fifth wheel  12  is meant first of all one of the bearing blocks  12   a , there being two blocks present, which hold the fifth wheel  12  relative to the vehicle chassis  17 . Oftentimes a supporting crossarm extends between the bearing blocks  12   a  and engages with them, and the second transceiver unit  34  can also be fastened on this. In another embodiment of the fifth wheel  12 , the bearing blocks  12   a  can also be fastened on a bearing plate  12   b , which is usually mounted from above on a vehicle frame and/or auxiliary vehicle frame, not shown here. 
     As long as the transceiver unit  31  is fastened to the rear axle  16  of the first vehicle  10 , no height correction by the lifting distance H Luft  needs to be undertaken, since the rear axles  16  roll along the ground surface GOK and are not raised during the coupling process. 
       FIG. 3  shows in a perspective view the second vehicle  20  and the transponders  47   a ,  47   b ,  48   a ,  48   b  arranged at the front end  29 . The eighth and ninth transponder  47   a ,  47   b  are located in the lower corners  27   a  of the front end  29  of the second vehicle  20 , bordering on the bodywork floor  27 . A tenth and eleventh transponder  48   a ,  48   b  are likewise arranged in upper corners  28   a  on the front end  29  of the second vehicle  20 , adjoining a roof wall  28 . With the aid of the eighth to eleventh transponders  47   a ,  47   b ,  48   a ,  48   b , the sensor device  30  can reconstruct an image of the end face of the second vehicle  20 , so that the first vehicle  10  can then approach the second vehicle  20  targeted exactly for the coupling process. 
       FIG. 4  shows a further embodiment in a side view, in which the sensor device  30  comprises only the single transceiver unit  31 . For the precise detecting of the height condition of the second vehicle  20 , an active transponder  50  is secured on its front end  29  immediately at a joint with the bodywork floor  27 , being situated at first in the active zone of the transceiver unit  31  and serving the purpose of the distance measurement. 
     The active transponder  50  is additionally connected to a height measuring sensor  51 , which measures without contact the vertical distance between the trailer plate  24  and the ground surface GOK. This metered value of the height measuring sensor  51  is continuously transmitted to the active transponder  50  and read out together with its encoding by the transceiver unit  31 . 
     The active transponder  50  may be installed in a second recess  24   a  formed for this purpose in the trailer plate  24 , as well as a second transponder  42  shown for example. 
       FIGS. 5 and 6  show a further exemplary embodiment of the invention, in which the sensor device  30  is arranged on the second vehicle  20 . The transceiver unit  31  with the antenna  33  formed on it is installed in the area of the front end  29  of the second vehicle  20  in the trailer plate  24  and emits a radar signal, which is reflected by two fifth transponders  44  arranged on the first vehicle  10 . The fifth transponder(s)  44  are fixed stationary on the rear wall of the driver&#39;s cabin  18  and enable a position detection of the first vehicle  10  backing up, by means of a distance measurement. 
     The distance of the trailer plate  24  of the second vehicle  20  above the ground surface GOK is an intrinsic feature of the system and it is calculated by a distance measurement from the antenna  33  of the transceiver unit  31  to a sixth transponder  45  situated on the telescopic section  25   b  of the support jack  25 . The sixth transponder  45  is preferably arranged as far below as possible on the telescopic section  25 , especially preferably on the support foot  25   c  of the telescopic section  25   b.    
     The stationary section  25   a  extends downward in its axial direction at a right angle α to the trailer plate  24 , exactly like the telescopic section  25   b  which is guided therein solely in translatory motion. The stationary section  25   a  after the mounting of the device according to the invention is spaced apart at a constant distance b, parallel to the extension of the trailer plate  24 , from the antenna  33  of the transceiver unit  31 . The direct distance between the antenna  33  and the sixth transponder  45  is measured by the transceiver unit  31  and corresponds to a measured distance c. The electronic controller  32  calculates from the constant distance b stored in its memory and the measured distance c a vertical distance a corresponding to the extension status of the support jack  25 . 
     The metered values of the distance measurements to the transponders  44  and the calculated value of the distance a are relayed by the electronic controller  32  via a data radio transmitter  60  arranged on the second vehicle  20  as a data signal  62  to the first vehicle  10 , still at a distance from yet approaching the first vehicle  10  prior to the coupling process, which has a data radio antenna  61  for receiving the data signal  62 , being connected to the vehicle controller  36 . The vehicle controller  36  may also comprise a plurality of vehicle controllers networked together. The vehicle controller  36  exerts influence on the control of engine and/or transmission  14 , the vehicle steering  15  and the brake  19  of the autonomous driving first vehicle  10 . 
       FIG. 7  deals with a road train in the form of an articulated train. The first vehicle has at its rear end a pin or jaw coupling  13 , in which the coupling means  21  of the second vehicle  20  is introduced and locked after coupling on the second vehicle  20 . The coupling means  21  of the second vehicle  20  is a drawbar  26 , which is designed as a rigid drawbar in the exemplary embodiment shown. At its distal end, a drawbar eye  26   a  is formed on the drawbar  26 , through which a coupling pin (not shown) of the pin coupling  13  is inserted after the coupling process. 
     The first vehicle  10  furthermore has a transceiver unit  31  with an antenna  33 , which is likewise arranged at the rear of the first vehicle  10 , close to the pin coupling  13 . In the area of the drawbar eye  26   a , the drawbar  26  has a third recess  26   b , in which a seventh transponder  46  is installed in protected manner. Basically, it is also possible to apply the seventh transponder  46  directly to the surface of the drawbar  26 . In this way, the seventh transponder  46  will be identified even better by the transceiver unit  31 , however it is exposed to a greater risk of damage during driving operation. 
     The contour of the front end  29  of the second vehicle  20  is bounded by an eighth and ninth transponder  47   a ,  47   b  located at the lower corners  27   a  and by a tenth and eleventh transponder  48   a ,  48   b  located at the upper corners  28   a  and their position can be detected by the transceiver unit  31 . In the representation of  FIG. 7 , only the eighth and tenth transponders  47   a ,  48   a  lying in front in the plane of the drawing can be seen. 
     LIST OF REFERENCE SYMBOLS 
     
         
           10  First vehicle 
           11  Air suspension 
           12  Fifth wheel 
           12   a  Bearing block 
           12   b  Bearing plate 
           13  Pin coupling 
           14  Engine and transmission 
           15  Vehicle steering 
           16  Rear axle 
           17  Vehicle chassis 
           18  Driver&#39;s cabin 
           19  Brake 
           20  Second vehicle 
           21  Coupling means 
           22  Kingpin 
           22   a  Fastening flange 
           22   b  Upper collar 
           22   c  Locking section 
           22   d  Lower collar 
           22   e  Bottom of lower collar 
           22   f  First recess 
           23  Bottom side of second vehicle 
           24  Trailer plate 
           24   a  Second recess 
           25  Support jack 
           25   a  Stationary section of support jack 
           25   b  Telescopic section of support jack 
           25   c  Support foot 
           26  Drawbar 
           26   a  Drawbar eye 
           26   b  Third recess 
           27  Bodywork floor 
           27   a  Lower corners 
           28  Roof wall 
           28   a  Upper corners 
           29  Front end of second vehicle 
           29   a  Add-on unit 
           29   b  Front end of add-on unit 
           30  Sensor device 
           31  Transceiver unit 
           32  Electronic controller 
           33  Antenna 
           34  Second transceiver unit 
           35  Second antenna 
           36  Vehicle controller 
           40  Reference point 
           41  First transponder (kingpin) 
           42  Second transponder (trailer plate) 
           43   a  Third transponder (support jack) 
           43   b  Fourth transponder (support jack) 
           44  Fifth transponder (first vehicle) 
           45  Sixth transponder (support jack extended) 
           46  Seventh transponder (drawbar eye) 
           47   a  Eighth transponder (lower corner) 
           47   b  Ninth transponder (lower corner) 
           48   a  Tenth transponder (upper corner) 
           48   b  Eleventh transponder (upper corner) 
           49  Twelfth transponder (add-on unit) 
           50  Active transponder (front edge of second vehicle) 
           51  Height measuring sensor 
           60  Data radio transmitter 
           61  Data radio antenna 
           62  Data signal 
         α a Support jack/trailer plate angle 
         a Trailer plate/GOK spacing 
         b Transceiver unit/support jack spacing 
         c Support jack measuring distance 
         GOK Road level, ground surface 
         Δh Vertical height clearance 
         H A1min  Lowest height, antenna 
         H A2min  Lowest height, second antenna 
         H Luft  Lifting distance, air suspension 
         H A1  Actual height, antenna 
         H A2  Actual height, second antenna 
         S Swivel axis, kingpin 
         X Vehicle lengthwise axis