The present invention relates to railway monitoring systems.
Various measurement mechanisms have been used to monitor various aspects of a railway system. Axle counter and wheel imbalance weighting system are two popular measurement mechanisms among them.
Conventionally, an axle counter uses magnetic fields to count the axles of a passing train, and a typical wheel imbalance weighting system uses a strain gauge sensor in a bridge circuit to measure the load of the train. Disadvantages exist with these conventional mechanisms, for example, installation of some conventional measurement mechanism may not be easy. More importantly, performance of these conventional mechanisms may be affected by external electromagnet radiation. This may deteriorate the reliability of these conventional measurement mechanisms, especially in an AC railway system, since lots of noises could be introduced to these conventional measurement mechanisms. In addition, these conventional measurement mechanisms need to be individually installed onto the railway. This may not be convenient if a significant number of measurement mechanisms are needed. Neither can it be convenient to set up a centralized railway monitoring system due to the complexity of collection of all the results from each individual measurement mechanism.
Therefore, it is an object of the present invention to provide an improved railway monitoring system that may solve at least part of the problems, or at least provide the public with a useful choice.
According to an aspect of present invention, a railway monitoring system firstly includes an optical fiber. A first part of the fiber is attachable to one of a pair of tracks of a rail, and a characteristic of the first part of the fiber is variable in correspondence to variance of a characteristic of said one track where the first part of fiber is attached. The system also includes an optical signal emitter connected to the fiber for emitting an optical signal into the fiber, and the fiber generates at least a first altered optical signal, which contains information relating to the variance of the characteristic of the part of the fiber. The system further includes an optical signal analyzer connected to the fiber for receiving and analyzing the first altered optical signal so as to ascertain the variance of said characteristic of said one track based upon the information contained in the first altered optical signal.
Preferably, both the emitter and the analyzer are connected to an end of the fiber, and the first altered optical signal is a signal reflected by the fiber towards the end.
According to another aspect of the present invention, a process for monitoring a railway system includes
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which description illustrates by way of example the principles of the invention.
As shown in
An optical signal interrogator 111, also connected to the end 109, receives these reflected signals and further detects a shift in the wavelength of each reflected optical signal as discussed in details below. The interrogator then passes the detection results to a computer 113 for analysis thereof. Based on these reflected optical signals, the interrogator 111 and the computer 113 are able to ascertain certain situations in the tracks 103, 105 and further to monitor the railway. It is noted that the exemplary system merely has an optical fiber in the railway region and therefore is not affected by external electromagnet radiations.
Working principles of a Bragg grating is discussed with reference to
In addition, as shown in
Therefore, in the system 100, when an axle of a train passes over a portion of one of the tracks where a Bragg grating, for example S1, is mounted, the portion of the track experiences a tensile strain due to the pressure or weight exerted thereon by the axle of the train. Since the Bragg grating S1 is fixedly mounted to the track 103 and extends parallel to the track 103, the Bragg grating S1 experiences the same tensile strain as the track. Such a tensile strain leads to a shift in the wavelength of the optical signal reflected by the Bragg grating S1, and this shift is proportional to the tensile strain both the Bragg grating and the track experience and correspondingly to the pressure exerted on the track. By detecting this shift by the interrogator 111, the system 100 thereby obtains information relating to the tensile strain both the Bragg grating and the track experience and correspondingly the pressure exerted on the track. When the axle leaves the portion of the track, both the track and the Bragg grating S1 restore quickly such that the shift in the wavelength of the reflected signal by S1 decreases to zero accordingly, and the Bragg grating S1 is then ready for the next tensile strain, which may caused by another axle.
Therefore, based on the shifts in the wavelengths of the reflected optical signals by the Bragg gratings, the system 100 is able to ascertain certain situations in the tracks 103, 105 and further to monitor the railway.
1. Axle Counter
The exemplary system 100 can be used to count the number of axles of a passing train by counting the number of successive shifts in the wavelength of optical signal reflected by one of the Bragg gating. The system 100 is also able to determine the end of the train if it does not detect any shifts in the wavelength during a predetermined period, which is designed to be substantially longer than a possible maximum period of time for two adjacent axles to pass through the Bragg grating.
2. Speed Detector
Since the physical separation between the axles of a train is generally known, the exemplary system 100 may easily ascertain the instantaneous speed of the train by using the period of time taken for successive axles to pass through a particular Bragg grating.
3. Headway Optimization
The exemplary system 100 can easily find out the start and end of a passing train. The exemplary system 100 can further ascertain a period of time between two successive trains by
The information about the period of time between two successive trains can then be used by the exemplary system 100 to control the speed of these two trains.
4. Flood Detector
It is understood that changes in either the tension in the fiber or the environment temperature will lead to shifts in the wavelength of the optical signal reflected by the Bragg grating. It is further understood that flooding may generally cause a sudden change in the environment temperature. Therefore, when the exemplary system 100 detects a shift in the wavelength of the reflected signal while simultaneously does not detect any substantial variance of this shift during a predetermined period, the exemplary system 100 may trigger a flooding alert. The predetermined period is preset to be at least longer than the possible maximum period of time for two adjacent axles to pass through a particular Bragg grating. Therefore, if the system 100 does not detect any substantial changes of the shift in the wavelength of a reflected optical signal during the predetermined period, it is very likely that there are not any trains passing through the Bragg grating. Therefore, the shift in the reflected wavelength is very likely caused by the change in the environment temperature, and a very possible reason for the change in the environment temperature is the occurrence of flooding.
5. Wheel Imbalance Weighting System
As the Bragg gratings S1-S8 are installed on the two tracks of a rail, the computer can process the data received from the interrogator to evaluate whether there is any imbalance between the two tracks of the rail.
6. Train Weighting System
Since the shift in the reflected wavelength reflects the strain, which the track experiences and which relates to the weight thereabove, the weight of a train can be measured by adding all the strain measurements along the entire train. Such a weighting system is particularly useful in the situations when the train is static or moves at a relatively low speed.
7. Train Identification
As shown in
It is understood that a number of Bragg gratings can be created in a single optical fiber as illustrated in the exemplary embodiment to monitor various factors of the railway system for a long distance. Alternatively, more than one fibers can be used in the system, each with a plurality of Bragg gratings created therein. Furthermore, each Bragg grating can be mounted to the tracks in a direction non-parallel to its respective track. In that case, the tensile strain the Bragg gratings experience may not be the same as the one the tracks experience. But the tensile strain the Bragg gratings experience is still relevant, if not exactly proportional to the one the tracks experience. Therefore, the system 100 is still able to ascertain the tensile strain the tracks experience based on the shifts in the wavelengths of the optical signals reflected by the Bragg gratings.
In addition, the exemplary system 100 uses the optical signals reflected by the Bragg gratings. It can be understood from
Number | Date | Country | Kind |
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04251840.7 | Mar 2004 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CN05/00385 | 3/25/2005 | WO | 12/26/2006 |