Abstract:
A method for locating a rail vehicle along a rail route, along which a waveguide is laid. Temporally successive electromagnetic pulses are fed into the waveguide and, for each emitted pulse, at least one back-scattering pattern generated by vehicle-induced back-scattering of the electromagnetic pulse is received and evaluated. The waveguide has at least one locating section along the rail route, in which locating section the vibration sensitivity of the waveguide and/or the vibration acting on the waveguide is greater or less than outside the locating section. The amplitude of the received back-scattering pattern is evaluated and a location signal is generated if the amplitude of the received back-scattering pattern increases or decreases over the course of time.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method for determining the location of a rail vehicle along a section of rail along which a wavequide is laid. Chronologically successive electromagnetic pulses are fed into the waveguide and in each case at least one backscatter pattern which is generated by vehicle-induced backscattering of the electromagnetic pulse is received for each emitted pulse and evaluated. 
     Such a method is known from International Patent Application WO 2011/027166 A1. In this previously known method, a waveguide is provided for determining the location of a rail vehicle along a section of rail, said waveguide being laid along the section of rail. Electromagnetic pulses are fed into the waveguide in chronological succession. For each emitted pulse, in each case at least one backscatter pattern generated by vehicle-induced backscattering of the electromagnetic pulse is received and evaluated. The location of the rail vehicle on the section of rail is determined by evaluating the backscatter patterns. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is based on the object of specifying a method for determining the location of a vehicle which permits reliable and particularly precise determination of a location. 
     This object is achieved according to the invention by means of a method as claimed. Advantageous refinements of the method according to the invention are specified in dependent claims. 
     Accordingly, according to the invention there is provision that the waveguide along the route has at least one location-determining section in which the vibration sensitivity of the waveguide and/or the vibration acting on the waveguide is greater than or less than outside the location-determining section, the amplitude of the received backscatter patterns is evaluated, and a location signal is generated if the amplitude of the received backscatter patterns increases or decreases in the chronological sequence. 
     A significant advantage of the method according to the invention is to be seen in the fact that in said method a vehicle-location-determining process is possible which is independent of the time period between the transmission of electromagnetic pulses and the reception of the backscatter patterns. In the method according to the invention, a vehicle-location-determining process can be carried out independently of this time period. This is possible since the at least one location-determining section changes the backscatter pattern as such, specifically in terms of the amplitude, with the result that on the basis of the change in the backscatter pattern as such, namely the change in amplitude thereof, a vehicle-location-determining process on the route is possible. Even if fluctuations in timing therefore occur, for example owing to delays within the scope of the generation of pulses and/or within the scope of the evaluation of the backscatter patterns, these do not have any influence on the accuracy of the process of determining the location of the vehicle since the vehicle in the region of the location-determining section or sections would always generate a backscatter pattern whose amplitude characteristic indicates the location-determining section and is independent of the period of time which has passed between the feeding of the pulses into the waveguide and the reception or evaluation of the associated backscatter patterns. 
     In order to permit a process of determining the location of the vehicle at different points on the route or in the region of different points on the waveguide, it is considered advantageous if the route is equipped with a multiplicity of location-determining sections which are provided spaced apart from one another in the waveguide. 
     According to one particularly preferred refinement of the method, there is provision that the location of a rail vehicle which is traveling on a section of track is determined, wherein the vibration, acting on the waveguide, in the location-determining section is increased by means of a local mechanical coupling between the waveguide and the section of track or reduced by means of a vibration-reducing device. 
     Alternatively or additionally, the vibration sensitivity of the waveguide in the location-determining section can be increased or decreased by using in the location-determining section waveguide material with a higher or lower vibration sensitivity than in the two waveguide sections located in front of and behind the respective location-determining section. 
     In addition an additional location-determining signal which indicates the location of the vehicle is preferably generated. 
     Such an additional location-determining signal can be formed, for example, by measuring reflections at interference points which are introduced into the waveguide and whose position is known and by generating the additional location-determining signal if the reception of the backscatter pattern coincides chronologically with a reflection by such an interference point. The arrangement of the interference points and/or the respective length of the interference points preferably forms location coding. 
     Alternatively, such an additional location-determining signal can be formed by measuring the time period between the feeding of the electromagnetic pulses into the waveguide and the detection of the respectively associated backscatter pattern and generating a distance signal which indicates the location of the vehicle as an additional location-determining signal on the basis of the time period. 
     The location signal and the additional location-determining signal are preferably checked for plausibility. 
     Such plausibility checking can be carried out in a particularly simple and therefore advantageous way by comparing, in the case of the formation of a location signal, the position of the vehicle which is indicated by the additional location-determining signal (for example distance signal) with the known position of the location-determining section. 
     A fault signal is preferably generated if the distance between the position of the vehicle indicated by the additional location-determining signal and the known position of the location-determining section exceeds a predefined threshold value. 
     Furthermore, it is considered advantageous if the waveguide along the route has a multiplicity of location-determining sections in which the vibration sensitivity of the waveguide and/or the vibration acting on the waveguide is greater than or less than in the two waveguide sections located in front of and behind the respective location-determining section, and in each case a location signal is generated if the amplitude of the received backscatter patterns in the chronological sequence increases or decreases. 
     When the vehicle drives into the route after an initial generation of the location signal the occurrence of the further location signals is preferably counted, and location-determining information is formed with the respective counter reading. 
     It is also considered advantageous if the arrangement of the location-determining sections and/or the respective length of the location-determining sections forms location coding, and during the evaluation of the chronological sequence of the backscatter patterns the location coding is detected and the location-determining sections are differentiated on the basis of the location coding. 
     The invention also relates to a location-determining device for determining the location of a vehicle along a route, having a waveguide which is laid along the route, a pulse-generating device for generating and feeding chronologically successive electromagnetic pulses into the waveguide, and a detection device for detecting electromagnetic backscatter patterns generated by vehicle-induced backscatter, and an evaluation device for evaluating the backscatter patterns. 
     With respect to such a location-determining device there is provision according to the invention that the waveguide along the route has at least one location-determining section in which the vibration sensitivity of the waveguide and/or the vibration acting on the waveguide is greater than or less than in the two waveguide sections located in front of and behind the location-determining section, and the evaluation device is configured in such a way that it carries out a process of determining the location of the vehicle at least also using the amplitude of the backscatter pattern. 
     With respect to the advantages of the location-determining device according to the invention reference is made to the above statements with respect to the method according to the invention since the advantages of the method according to the invention correspond substantially to those of the location-determining device according to the invention. 
     The waveguide is preferably laid next to a section of track, and the vibration, acting on the waveguide, in the location-determining section is preferably increased by means of a local mechanical coupling between the waveguide and the section of track or reduced by a vibration-reducing device. 
     Additionally or alternatively, the waveguide can have, in the location-determining section, waveguide material with a higher or lower vibration sensitivity than in the two waveguide sections located in front of and behind the location-determining section. 
     The waveguide along the route particularly preferably has a multiplicity of location-determining sections in which the vibration sensitivity of the waveguide and/or the vibration acting on the waveguide is greater than or less than in the two waveguide sections located in front of and behind the respective location-determining section. 
     The arrangement of the location-determining sections and/or the respective length of the location-determining sections preferably forms location coding. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The invention will be explained in more detail below on the basis of exemplary embodiments; in the drawings, in each case by way of example, 
         FIG. 1  shows an exemplary embodiment of a location-determining device according to the invention for determining the location of a vehicle along a route, 
         FIGS. 2-4  show by way of example backscatter patterns which are generated by a vehicle on the route according to  FIG. 1 , 
         FIG. 5  shows an exemplary embodiment of a location-determining device according to the invention in which location-determining sections form location coding, 
         FIG. 6  shows a further exemplary embodiment of a location-determining device according to the invention, 
         FIGS. 7-9  show by way of example backscatter patterns which are generated by a vehicle on the route according to  FIG. 6 , 
         FIG. 10  shows a further exemplary embodiment of a location-determining device according to the invention, and 
         FIG. 11  shows an exemplary embodiment of a connecting element in more detail. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     In the figures, the same reference symbols are always used for identical or comparable components for the sake of clarity.  FIG. 1  shows a location-determining device  10  which comprises a pulse-generating device  20 , a detection device  30 , an optical coupling device  40 , a waveguide  50 , for example in the form of an optical waveguide, and an evaluation device  60 . 
     The pulse-generating device  20  preferably has a laser (not shown further) which permits short electromagnetic, in particular optical, pulses to be generated regularly, for example with a permanently predefined pulse rate, and to be fed into the waveguide  50  via the coupling device  40 . The pulse-generating device  20  is preferably actuated by the evaluation device  60 , with the result that the times of the generation of pulses are at least approximately known to the evaluation device  60 . 
     The detection device  30  has, for example, a photo detector which permits the detection of electromagnetic radiation. The detection device  30  transmits its measurement signals to the evaluation device  60  which evaluates them. 
     In  FIG. 1  it can be seen that the waveguide  50  is arranged along a section of rail  100 . A rail vehicle  110  travels on the section of rail  100  from left to right in the direction P of the arrow. In the illustration according to  FIG. 1 , the movement of the rail vehicle  110  in the direction P of the arrow is symbolized by two further positions (cf. rail vehicle positions  110 ′ and  110 ″). 
       FIG. 1  shows that the waveguide  50  is equipped with location-determining sections  51 ,  52  and  53  in which the vibration acting on the waveguide  50  as a result of the rail vehicle passing is greater than outside the location-determining sections  51 ,  52  and  53 . The increase in the vibration in the location-determining sections  51  to  53  is due, for example, to the fact that the waveguide  50  is mechanically coupled in these sections to the tracks of the section of rail  100  by one or more connecting elements  115  in the form of rods, tubes, pins or the like (cf.  FIG. 11 ). Additionally or alternatively, it is also possible to use in the location-determining sections  51  to  53  a waveguide material which has per se a higher vibration sensitivity than the waveguide material outside the location-determining sections  51 ,  52  and  53 . 
     The location-determining device  10  according to  FIG. 1  can be operated to determine the location of the rail vehicle  110 , for example as follows: 
     The evaluation device  60  actuates the pulse-generating device  20  in such a way that it feeds electromagnetic pulses Pin in chronological succession into the waveguide  50  via the coupling device  40 . The electromagnetic pulses which are generated run from left to right in the direction P of the arrow in  FIG. 1  and are preferably absorbed at the end  50   a  of the waveguide by an absorption device  200 . 
     The waveguide  50  is locally shaken or made to vibrate by the rail vehicle  110  traveling on the section of rail  100 ; this is characterized in  FIG. 1  by arrows with the reference symbol Ms. Owing to these vibrations or owing to shaking of the waveguide  50 , backscattering of the electromagnetic radiation will occur locally in the region in which the rail vehicle  110  is currently located. The backscattered radiation has a backscatter pattern which is characteristic of the shaking which is caused by the rail vehicle  110  and is input into the waveguide  50 . 
     The backscattered radiation runs counter to the direction of travel P of the rail vehicle in the direction of the coupling device  40  and in the direction of the detection device  30  and is detected there by the detection device  30 . The detection device  30  is configured in such a way that it measures the intensity of the radiation which is scattered back and passes on a corresponding measurement signal to the evaluation device  60 . The intensity of the radiation which is scattered back is characterized by the reference symbol Ir(t) in  FIG. 1 . 
     The evaluation device  60  will evaluate the radiation Ir(t) which is scattered back and the backscatter patterns contained therein. If the amplitude of the received backscatter patterns increases in the chronological sequence, it will indicate that one of the location-determining sections  51  to  53  is being passed and generate a location signal So. This will be explained in more detail on the basis of  FIGS. 2 to 4 . 
       FIG. 2  illustrates by way of example a backscatter pattern Rm 1  which arrives in the evaluation device  60  when an electromagnetic pulse has been irradiated into the waveguide  50  by the pulse device  20  at the time t=0. The length of the received backscatter pattern Rm 1  is characterized by the reference symbol dt 1  in  FIG. 2 . 
     The backscatter pattern Rm 1  relates to the position of the rail vehicle according to  FIG. 1  as is characterized there with unbroken lines and the reference symbol  110 . 
     If the rail vehicle  110  then moves further in the direction P of the arrow according to  FIG. 1  and reaches the position characterized by the reference symbol  110 ′, it will cause the location-determining section  51  of the waveguide  50  to experience mechanical oscillations. In the region of the location-determining section  51  the vibration acting on the waveguide  50  and/or the vibration sensitivity thereof is however very much greater than outside the location-determining sections  51 - 53 , with the result that the amplitude of the backscatter pattern is increased. This is illustrated in  FIG. 3 . 
     When the rail vehicle  110  leaves the region of the location-determining section  51  again and arrives in the region between the two location-determining sections  51  and  52  according to  FIG. 1  (cf. the position of the rail vehicle in  FIG. 1  which is characterized by the reference symbol  110 ″), the amplitude of the backscatter pattern will be reduced again to the normal amount. Accordingly, the amplitude of the backscatter pattern Rm 3  (cf.  FIG. 4 ) corresponds again to the original amplitude of the backscatter pattern Rm 1  according to  FIG. 2 . 
     In summary, the evaluation device  60  is therefore able to determine the location of the rail vehicle  110  on the section of rail  100  on the basis of the amplitudes of the backscatter patterns Rm 1 , Rm 2  and Rm 3  because the local position of the location-determining sections  51  to  53  along the section of rail  100  is known. 
     By counting the location signals So generated on the output side by the evaluation device  60  it is therefore possible to track the travel of the rail vehicle. 
     The arrangement of the location-determining sections and/or the respective length of the location-determining sections preferably forms location coding. 
     In addition to a process of determining the location of the rail vehicle  110  on the basis of the location-determining sections  51  to  53 , the detection device  30  can also perform a location-determining process on the basis of the time periods which occur between the feeding of the electromagnetic pulses Pin into the waveguide  50  and the detection of the respectively associated backscatter pattern Rm 1 , Rm 2  and Rm 3 . 
       FIGS. 2-4  show that the time periods between the respective electromagnetic excitation pulse Pin and the associated backscatter pattern Rm 1 , Rm 2  and Rm 3  during the travel of the rail vehicle  110  on the section of rail  100  will increase; this is due to the fact that the transit time of the electromagnetic pulses and the transit time of the electromagnetic backscatter patterns in the waveguide  50  become longer as the distance of the rail vehicle  110  from the pulse-generating device  20  or the detection device  30  becomes longer. 
     The evaluation device  60  is therefore able to determine the distance and therefore the location of the rail vehicle  110  on the basis of the time periods T 1 , T 2  and T 3  and to generate a corresponding distance signal Se which forms an additional location-determining signal. The distance Ls of the rail vehicle  110 ′ in  FIG. 1  can be calculated, for example, according to:
 
 Ls= 1/2* T 2/ V  
 
where V indicates the speed of the pulses in the waveguide  50 . The time period T 2  can be obtained from the measurement according to  FIG. 3 . The factor 1/2 takes into account the fact that the radiation has to pass through the respective waveguide section twice, specifically once in the forward direction and once in the return direction. For the speed V the following applies, for example:
 
 V=c 0 /n  
 
where c0 indicates the speed of light and n the refractive index in the waveguide  50 .
 
     The detection device  30  is therefore able to determine the location of the rail vehicle  110  additionally also on the basis of the time periods T 1 , T 2  and T 3  which pass between the transmission of the pulses Pin and the reception of the respective backscatter pattern Rm 1 , Rm 2  and Rm 3 . 
     It is considered particularly advantageous if, in the case of a process of determining the location of the rail vehicle  110  in the region of one of the location-determining sections  51  to  53  and the generation of a corresponding location signal So, the evaluation device  60  additionally performs plausibility checking. Such plausibility checking can take place, for example, in such a way that when one of the location-determining sections  51  to  53  is detected and a location signal So is generated the evaluation device  60  evaluates the time period between the generation of the pulse and the arrival of the backscatter pattern (cf. time period T 2  according to  FIG. 3 ) and determines the distance Ls of the rail vehicle  110 . Subsequently, the evaluation device  60  can check whether the distance signal Se corresponds to the location signal So which is formed. 
     The evaluation device  60  will for example generate a fault signal F if the difference between the position Ls indicated by the distance signal Se and the known position of the detected location-determining section  51  exceeds a predefined threshold value. The same applies to plausibility checks for the other location-determining sections. 
       FIG. 5  shows an exemplary embodiment of a location-determining device  10  according to the invention in which the waveguide  50  has a multiplicity of location-determining sections  51  to  55  which are arranged in such a way that they form location coding. This location coding makes it possible to detect the location of the rail vehicle  110  on the section of rail  100  without having to observe or count the occurrence of the location-determining sections. 
     For reasons of clarity, the location coding is indicated by a coded arrangement of the location-determining sections  51  to  55  only on the basis of a small number of location-determining sections; it is self-evident that the location coding can be optimized with respect to its accuracy and evaluation capability if a very much larger number of location-determining sections is used. 
     The location coding by coding the location of the arrangement of the location-determining sections can be carried out, for example, in such a way that binary coding patterns are formed by means of the location-determining sections. 
       FIG. 6  shows an exemplary embodiment of a location-determining device  10  in which the waveguide  50  is equipped with location-determining sections  51 - 55  in which the vibration acting on the waveguide  50  as a result of a rail vehicle passing is less than outside the location-determining sections  51 - 55 . The reduction in the vibration in the location-determining sections  51  to  55  is due, for example, to the fact that the waveguide  50  is mechanically entirely or at least to a certain extent decoupled in these sections from the tracks of the section of rail  100  by means of one or more damping elements  116  which each form a vibration-reducing device. Additionally or alternatively, a waveguide material which has per se a lower vibration sensitivity than the waveguide material outside the location-determining sections  51  to  55  can also be used in the location-determining sections  51  to  55 . 
     If the rail vehicle  110  then moves in the direction P of the arrow according to  FIG. 6 , it will cause the location-determining section  51  of the waveguide  50  to experience mechanical oscillations. The vibration acting on the waveguide  50  and/or the vibration sensitivity thereof is however very much less in the region of the location-determining section  51  than outside the location-determining sections  51 - 55 , with the result that the amplitude of the backscatter pattern is reduced. This is illustrated in  FIG. 8 . 
     When the rail vehicle  110  leaves the region of the location-determining section  51  again and arrives in the region between the two location-determining sections  51  and  52  (cf. the position of the rail vehicle characterized by the reference symbol  110  in  FIG. 6 ), the amplitude of the backscatter pattern will increase again to the normal amount. Accordingly, the amplitude of the backscatter pattern Rm 3  (cf.  FIG. 9 ) corresponds again to the original amplitude of the backscatter pattern Rm 1  according to  FIG. 7 . 
       FIG. 10  shows an exemplary embodiment of a location-determining device  10  in which reflections at interference points  117  which are introduced into the waveguide and whose position is known are measured and an additional location-determining signal ZOS is generated if the reception of the backscatter pattern coincides chronologically with a reflection by such an interference point. 
       FIG. 11  shows an exemplary embodiment of a connecting element  115  with which the track  400  of the section of rail  100  is connected to the waveguide  50  in a locally mechanical fashion. The connecting element  115  can be, for example, a rod, a pin or a tube. The connecting element is made to extend perpendicularly from the track  400  through the track bed  410  to the waveguide  50 . 
     Although the invention has been illustrated and described in more detail by means of preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.