Processing of Railway Track Data

Abstract

The quality of a railway track ( 11 ) may be assessed with transducers on a track recording vehicle ( 10 ). The received data are filtered in a way that introduces phase shifts, the filtration process having an associated transfer function (H). An inverting transfer function H<The is therefore selected which inverts at least the phase differences of the transfer function (H) of the filter. A multiplicity (N) of successive data samples are stored in a memory, each with an indication of the corresponding position or time, and an output data sample is calculated as the integral of the product of the stored data samples with an impulse function (F) centred on the middle stored sample. The impulse function F (T) is related to the inverting transfer function H<The. As each data sample is moved into the memory the oldest such sample is deleted, and on each occasion an output data sample is calculated. The resulting output data stream represents the original data, without the phase shifts that were caused by the filtration process.

1 . A method of obtaining data on the quality of a railway track, the method comprising 
 a) receiving from a track recording vehicle data concerning variations of a parameter, the data comprising samples, obtained in either the spatial or the temporal domain, which have been subjected to a filtration process having an associated transfer function (H);    b) selecting a transfer function H T  which inverts at least the phase differences of the transfer function H of the filter;    c) temporarily storing a multiplicity (N) of sequentially-received samples in a memory, each said sample being stored with an indication of the corresponding position or time;    d) generating an output data sample by calculating the integral of the product of the stored data samples with an impulse function (F), wherein the impulse function is deduced from the selected transfer function H T  according to the equation:                H   T     ⁡     (   jω   )       =       ∫     -   ∞     ∞     ⁢       F   ⁡     (   t   )       ⁢     ⅇ     jω   ⁢           ⁢   t       ⁢     ⅆ   t                 if time (t) is the appropriate variable, or, if expressed in terms of distance (s)                H   T     ⁡     (   jω   )       =       ∫     -   ∞     ∞     ⁢       F   ⁡     (   s   )       ⁢     ⅇ     jω   ⁢           ⁢   s       ⁢           ⁢     ⅆ   s                 e) storing the next successive sample of data in the memory and deleting the oldest sample stored in the memory, and repeating the step of generating an output data sample;    and    f) repeatedly performing the preceding step.    
   
   
       2 . A method as claimed in  claim 1  wherein the selected transfer function H T  is such as to reverse both the changes in phase and the changes in amplitude due to the filtration process.  
   
   
       3 . A method as claimed in  claim 1  wherein the impulse function is centred on the ((N+1)/2) th  stored sample.  
   
   
       4 . A method as claimed in  claim 3  wherein the multiplicity is an odd number.  
   
   
       5 . A method as claimed in  claim 1  wherein the method is performed within a track recording vehicle.  
   
   
       6 . An apparatus for performing a method as claimed in  claim 1.