U.S. patent application number 11/390923 was filed with the patent office on 2006-09-28 for fiber optic monitor for railroad switch.
This patent application is currently assigned to Fibera, Inc.. Invention is credited to John C. Tsai.
Application Number | 20060214068 11/390923 |
Document ID | / |
Family ID | 37034265 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060214068 |
Kind Code |
A1 |
Tsai; John C. |
September 28, 2006 |
Fiber optic monitor for railroad switch
Abstract
An improved railroad switch monitoring unit of the type that
determines whether a mobile rail is brought into a closed state or
an open state with respect to a stationary rail. The improvement
comprises a fiber Bragg grating (FBG) included in the monitoring
unit that is used to determine, based on stress able change in the
resonant wavelength of the FBG, whether the mobile rail and the
stationary rail are closed or open.
Inventors: |
Tsai; John C.; (Saratoga,
CA) |
Correspondence
Address: |
INTELLECTUAL PROPERTY LAW OFFICES
1901 S. BASCOM AVENUE, SUITE 660
CAMPBELL
CA
95008
US
|
Assignee: |
Fibera, Inc.
Santa Clara
CA
|
Family ID: |
37034265 |
Appl. No.: |
11/390923 |
Filed: |
March 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60594292 |
Mar 25, 2005 |
|
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Current U.S.
Class: |
246/435R |
Current CPC
Class: |
B61L 5/107 20130101 |
Class at
Publication: |
246/435.00R |
International
Class: |
E01B 7/02 20060101
E01B007/02 |
Claims
1. An improved railroad switch monitoring unit of the type that
determines whether a mobile rail is brought into a closed state or
an open state with respect to a stationary rail, the improvement
comprising: a fiber Bragg grating (FBG) included in the monitoring
unit to determine based on stress able change in the resonant
wavelength of said FBG whether the mobile rail and the stationary
rail are in any of the closed state, the open state, or
neither.
2. A method for determining whether a mobile rail and a stationary
rail of a railroad switch are in a closed state or an open state,
the method comprising: providing a fiber Bragg grating (FBG) placed
such that operation of the mobile rail with respect to the
stationary rail stress ably effects the resonant wavelength of said
FBG; detecting the resonant wavelength of said FBG; and determining
based on the resonant wavelength of said FBG whether the mobile
rail and the stationary rail are in the closed state, the open
state, or neither.
3. The method of claim 2, wherein said step of detecting includes:
defining a closed wavelength to be the resonant wavelength of said
FBG when the mobile rail and the stationary rail are in the closed
state; defining an open wavelength to be the resonant wavelength of
said FBG when the mobile rail and the stationary rail are in the
open state; directing a light beam including at least one of said
closed wavelength and said open wavelength to said FBG via an
optical fiber; receiving any reflected portion of said light beam
back from said FBG via said optical fiber; and sensing whether said
any reflected portion includes any of said closed wavelength and
said open wavelength.
4. An apparatus for monitoring operation of a railroad switch
having a stationary rail and a mobile rail position able into a
closed state or an open state with respect to the stationary rail,
the apparatus comprising: a fiber Bragg grating (FBG); and a mount
holding said FBG such that positioning of the mobile rail with
respect to the stationary rail changes the resonant wavelength of
said FBG.
5. The apparatus of claim 4 wherein a closed wavelength is defined
to be the resonant wavelength of said FBG when the mobile rail and
the stationary rail are in the closed state and an open wavelength
is defined to be the resonant wavelength of said FBG when the
mobile rail and the stationary rail are in the open state, and
wherein the apparatus is comprised within a monitoring system
including: a light source to produce a first light beam including
at least one of said closed wavelength and said open wavelength; a
light receiver to receive a second light beam and sense whether it
includes any of said closed wavelength and said open wavelength;
and an optical fiber to direct said first light beam from said
light source to said FBG and to return any said second light beam
reflected from said FBG to said light receiver.
6. The apparatus of claim 4, wherein said light source includes a
laser.
7. The apparatus of claim 6, wherein said laser concurrently
produces a range of light wavelengths that encompass said closed
wavelength and said open wavelength.
8. The apparatus of claim 6, wherein said laser tune ably produces
a specific light wavelength within a range of light wavelengths
that encompass said closed wavelength and said open wavelength.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/594,292, filed Mar. 25, 2005, hereby
incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates generally to railway safety,
and more particularly to such in railroad track switches or
turnouts.
BACKGROUND ART
[0003] The railroad switch, also commonly called a "turnout," is an
important device for railroad operations. It enables trains to move
from main to branch lines (or vice versa), and allows dispatchers
to schedule operations. FIGS. 1a-b (prior art) show an example of a
typical railroad switch, connecting A and C in FIG. 1a and
connecting A and B in FIG. 1b.
[0004] Railroad switches have historically been operated manually,
but are now usually operated electronically by dispatchers in
control rooms that can be quite far away from the actual railroad
switch locations. The dispatchers thus often lack complete position
information for the trains that are about to pass respective
railroad switches because there is no current device being widely
used to monitor for this.
[0005] Railroad switches are inherently high maintenance devices,
with high wear-out rates. They require routine inspection so that
proper repair or replacement can be made. Nonetheless, many
incidents of failure still occur during the intervals between
routine inspections. Various reasons exist for this. For example,
the wear on them varies considerably, often due to factors that are
unpredictable or not easily monitored. Without limitation, some of
these factors include the number of trains passing and the numbers
of cars in them. Other factors are the weights of the cars and the
conditions of their wheels and carriages. Still other factors are
the train speeds and the weather conditions.
[0006] From 1996 through 2000 approximately 200 accidents each year
were attributable to problems with railroad switches. These
problems were ones such as those noted, as well as others such as
snow or rubbish clogging contacts (causing derailment), ballast
structure changes, and wrong direction switch setting. This amounts
to approximately 20% of the number of railroad accidents that
occurred in each of those years.
[0007] It follows that insuring the proper operation of railroad
switches is still not a well developed art, and that new and
improved systems for this will provide substantial benefits in
railway safety.
DISCLOSURE OF INVENTION
[0008] Accordingly, it is an object of the present invention to
provide an improved system for monitoring railroad switches.
[0009] Briefly, one preferred embodiment of the present invention
is an improved railroad switch monitoring unit of the type used to
determine whether a mobile rail and a stationary rail are closed or
open. The improvement being inclusion in the monitoring unit of a
fiber Bragg grating (FBG) to determine based on changed stress in
the resonant wavelength of the FBG whether the mobile and
stationary rails are closed state, open, or neither.
[0010] Briefly, another preferred embodiment of the present
invention is a method for determining whether a mobile rail and a
stationary rail of a railroad switch are closed or open. A fiber
Bragg grating (FBG) is provided and placed such that operation of
the mobile rail with respect to the stationary rail stress ably
effects the resonant wavelength of the FBG. The resonant wavelength
of the FBG is then detected. And based on the resonant wavelength
of the FBG it is determined whether the mobile and stationary rail
are closed, open, or neither.
[0011] Briefly, another preferred embodiment of the present
invention is an apparatus for monitoring operation of a railroad
switch having a stationary rail and a mobile rail that are position
able to be closed or open. A fiber Bragg grating (FBG) is provide
in a mount holding it such that positioning of the mobile rail with
respect to the stationary rail changes the resonant wavelength of
the FBG.
[0012] These and other objects and advantages of the present
invention will become clear to those skilled in the art in view of
the description of the best presently known mode of carrying out
the invention and the industrial applicability of the preferred
embodiment as described herein and as illustrated in the figures of
the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The purposes and advantages of the present invention will be
apparent from the following detailed description in conjunction
with the appended figures of drawings in which:
[0014] FIGS. 1a-b (prior art) show an example of a typical railroad
switch.
[0015] FIGS. 2a-b are cross-section views showing a switch
monitoring unit in accord with the present invention, wherein FIG.
2a shows a railroad switch in a "closed" position and FIG. 2b shows
the railroad switch in an "open" position.
[0016] FIGS. 3a-c are a left side cross-section, a top plan, and a
right side cross-section views of an exemplary switch monitoring
unit, wherein FIG. 3a particularly depicts an un-actuated condition
and FIG. 3c particularly depicts an actuated condition.
[0017] FIG. 4 is a schematic overview of an application of the
switch monitoring unit with a control system.
[0018] FIG. 5 is a stylized schematic diagram depicting a large
monitoring network of the switch monitoring units with local
control systems and a master system.
[0019] In the various figures of the drawings, like references are
used to denote like or similar elements or steps.
BEST MODE FOR CARRYING OUT THE INVENTION
[0020] A preferred embodiment of the present invention is a fiber
optic monitor for railroad switches. As illustrated in the various
drawings herein, and particularly in the views of FIGS. 2a-b and
FIGS. 3a-c, preferred embodiments of the invention are depicted by
the general reference character 10.
[0021] In this invention, we propose to use fiber Bragg grating
(FBG) sensors to monitor railway track conditions and the contact
of railroad switches. The applicable physics for FBGs has been
described elsewhere, including in widely available optics texts and
in patent applications related to railway operations and safety by
the present inventor, and therefore is not discussed in great
detail herein. In brief, an FBG exhibits a resonant condition
whereby it reflects light of a particular wavelength. As stress is
applied to or removed from the FBG, the resonant wavelength
changes. Accordingly, by providing suitable light and monitoring
for changes in which wavelengths are (or are not) reflected it
becomes possible to determine whether the stress on a FBG has
changed.
[0022] Turning now to FIGS. 2a-b, these are cross-section views
showing a switch monitoring unit 10 in accord with the present
invention. FIG. 2a shows a railroad switch 12 in a "closed"
position and FIG. 2b shows the railroad switch 12 in an "open"
position. The switch monitoring unit 10 here is shown mounted on a
stationary rail 14a, but it can alternately be mounted on a mobile
rail 14b, or anywhere that it is suitably actuated when the
position of the mobile rail 14b changes.
[0023] FIGS. 2a-b are simplified to depict basic principles of
operation. Those skilled in the art, however, will appreciate that
it may be advantageous to employ two switch monitoring units 10,
wherein one is used to monitor for positive positioning of the
mobile rail 14b adjacent to the stationary rail 14a and the other
is used to monitor for positive positioning of the mobile rail 14b
away from the stationary rail 14a.
[0024] FIGS. 3a-c are a left side cross-section view, a top plan
view, and a right side cross-section view of an exemplary switch
monitoring unit 10. FIG. 3a particularly depicts the switch
monitoring unit 10 in an un-actuated condition (e.g., that of FIG.
2b) and FIG. 3c particularly depicts the switch monitoring unit 10
in an actuated condition (e.g., that of FIG. 2a). As can be seen, a
FBG 16 embedded in optical fiber 18 here has a length "X" in FIG.
3a that is stretched to "X+.DELTA." in FIG. 3c. This produces a
corresponding change in the resonant condition of the FBG 16 that
can be usefully monitored.
[0025] FIG. 4 is a schematic overview of an application of the
switch monitoring unit 10 with a control system 20. The control
system 20 includes a light source 22, here a laser, that provides a
light beam 24 having appropriate wavelength characteristics to work
with the FBG 16 in the switch monitoring unit 10. The light beam 24
is carried via optical fiber 18 to the switch monitoring unit 10,
where any wavelength in the light beam 24 that corresponds with the
resonant condition of the FBG 16 there is reflected back, via the
optical fiber 18. In its return path, however, a portion of the
light beam 24 particularly passes through a beam splitter 26 to a
receiver 28 (e.g., a photodetector). The receiver 28 then produces
a signal, which is processed by a signal processor 30, and used by
a logic unit 32 (e.g., a microprocessor) to make a determination
whether the railroad switch 12 is open or closed and to communicate
that information as appropriate.
[0026] Various levels of sophistication can be utilized by the
control system 20. For example, without limitation, the light
source 22 can produce the light beam 24 with
.lamda..sub.3=.lamda..sub.O, wherein .lamda..sub.O is the resonant
wavelength of the FBG 16 when the switch monitoring unit 10 is not
actuated and .lamda..sub.O+.DELTA. is the resonant wavelength of
the FBG 16 when the switch monitoring unit 10 is actuated. The
receiver 28 will then receive most of the light beam 24
(.lamda..sub.3) as long as the switch monitoring unit 10 is not
actuated (i.e., the railroad switch 12 is presumably "open").
Conversely, the light source 22 can be set to produce the light
beam 24 with .lamda..sub.7=.lamda..sub.O+.DELTA., and the receiver
28 will then receive most of the light beam 24 (.lamda..sub.7) only
when the switch monitoring unit 10 is actuated (i.e., the railroad
switch 12 is presumably "closed").
[0027] Such "binary" embodiments can serve in many applications. In
other applications, however, it may be desirable to have more
information. The light source 22 used then can be one able to
produce the light beam 24 with a broad band of wavelengths, say
with .lamda..sub.1-9. The receiver 28 used here can then be one
that monitors for this range of wavelengths. If .lamda..sub.3 is
received most strongly, the control system 20 can report that the
railroad switch 12 is open. If .lamda..sub.7 is received most
strongly, the control system 20 can report that the railroad switch
12 is closed. If any of .lamda..sub.1, 2, 4, 5, 6, 8, 9 is received
most strongly, or if no reflected wavelength is detected at all,
the control system 20 can report that inspection is advisable and
that some manner of repair or replacement may be needed. This can
be termed a pseudo analog approach, wherein a reflected wavelength
other than .lamda..sub.3 (open) or .lamda..sub.7 (closed) has
informative value.
[0028] Since the FBG 16 can detect very small changes, even as
little as a few microns of physical movement, phenomena such as
clogging of the railroad switch 12 due to snow or rubbish, a
malfunction in the closing of the railroad switch 12, or abrupt
changes in the civil structure adjacent to the railroad switch 12,
etc., can all easily be detected and appropriate information can be
reported to a dispatcher or other appropriate authorities in real
time.
[0029] The present invention can also provide a number of optional,
subtle benefits. The distance that the light beam 24 can reliably
travel through the optical fiber 18 can be considerable,
potentially hundreds of kilometers without amplification. The
switch monitoring units 10 can also be connected into parallel or
serial ("Daisy chain") configurations with the optical fiber 18.
Serial arrangements are straightforward. In parallel arrangements,
demultiplexing the various wavelengths in the reflected light beam
24 permits determining the state of the railroad switch 12 at each
switch monitoring unit 10.
[0030] FIG. 5 is a stylized schematic diagram depicting a large
monitoring network 40 of switch monitoring units 10, local control
systems 20, and a master system 42. The switch monitoring units 10
inherently have resonant wavelengths in their respective states of
interest, and these are shown in FIG. 5. The control systems 20 and
the master system 42 communicate via communications links 44.
[0031] A topmost control system 20, 20a in FIG. 5 serially connects
to four switch monitoring units 10 arranged in two pairs. For
example, one pair of the switch monitoring units 10 could be
employed at a first railroad switch, with one configured to reflect
.lamda..sub.1 when it is affirmatively stressed by the switch being
closed and the other configured to reflect .lamda..sub.2 when it is
not stressed by the switch being open. The second pair of switch
monitoring units 10, those using .lamda..sub.3 and .lamda..sub.4,
could then be similarly employed at a second railroad switch 25
kilometers away. If the control system 20, 20a here "sees"
.lamda..sub.1 and not .lamda..sub.2 reflected back, this indicates
that the first (closest) railroad switch is closed. Similarly, if
the control system 20, 20a here sees .lamda..sub.3 and not
.lamda..sub.4 reflected back, this indicates that the first
(furthest away) railroad switch is closed. However, if the control
system 20, 20a sees both .lamda..sub.1 and .lamda..sub.2, or
neither of these, or both .lamda..sub.3 and .lamda..sub.4, or
neither of these, this indicates that something is awry.
[0032] A second topmost control system 20, 20b in FIG. 5 serially
connects to only a single switch monitoring unit 10, but it is one
quite distant from the control system 20, 20b here. As discussed
above, the use of optical fiber 18 (FIG. 4) to connect the switch
monitoring units 10 and the control systems 20 can permit quite
economical and robust use of the present invention even across
quite large distances.
[0033] A third topmost (second bottom most) control system 20, 20c
in FIG. 5 connects to two switch monitoring units 10. One of these
is a stressed unit 10a that is stressed by the mechanical action of
a railroad switch being operated and the other is an unstressed
unit 10b that is not mechanically stressed in this manner. As
described in more detail below, the control system 20, 20c here can
perform a differential comparison of the respective wavelengths
reflected back from these switch monitoring units 10a, 10b to
obtain a higher degree of confidence whether or not the mechanical
action of a railroad switch is what is actually being observed. The
control system 20, 20c and the switch monitoring units 10a, 10b
here are all in relatively close proximity, although there is no
particular need for this to be the case.
[0034] And a bottom most control system 20, 20d in FIG. 5 connects
to many switch monitoring units 10 configured in both serial and
parallel arrangements, and located at varying distances from the
control system 20, 20d and from each other.
[0035] The communications links 44 between the control systems 20
and the master system 42 can be of various types and in various
arrangements, as motivated by the typical factors for communicating
similar distances in similar environments. For example, without
limitation, the control systems 20a, 20b in FIG. 5 communicate with
the master system 42 via conventional telephone lines 44a (or via
dedicated phone lines, or via cellular telephone). The control
system 20c does not communicate directly with the master system 42.
Instead the control system 20b and the control system 20c
intercommunicate directly via an Ethernet local area network
(Ethernet LAN 44b), and the control system 20b "forwards" message
traffic between the control system 20c and the master system 42.
The control system 20d in FIG. 5 communicates with the master
system 42 via the Internet 44c. In this latter exemplary instance,
the control system 20d itself may handle all matters related to
railroad switch operation locally, yet still communicate onward
with the master system 42 so that more detailed analysis or
analysis in combination with information from the other control
systems 20 can also be performed.
[0036] As a device, a FBG is generally subject to temperature as
well as stress. On first consideration, this may seem a
disadvantage. Where that is the case, however, it can be dealt
with. For example, the present inventor's company, Fibera, Inc. of
Santa Clara, Calif. is a provider of a thermal FBGs. Alternately,
the control system 20 can include a compensating capability (e.g.,
a temperature measurement system under control of the logic unit
32). Still alternately, a second FBG 16 can be provided proximate
to the first one, but mounted such that it is not stressed (see
e.g., switch monitoring units 10a, 10b in FIG. 5). Differential
processing of the reflected light from the two FBGs 16 will then be
a very accurate indication of the stress on the first FBG 16 that
is actually attributable to operation of the railroad switch
12.
[0037] On deeper consideration, however, having the FBG 16 subject
to temperature as well as stress can be turned into an advantage.
With relatively little added, the control system 20 can report on
the temperature at one or more railroad switches 12. Thus,
personnel can be made aware if the temperature on a particular
stretch of distant railway line is so hot that the rails there may
have shifted or started to buckle. A railway dispatcher can then
instruct train engineers to proceed at a slower, safer speed on
that localized stretch and a railway traffic clerk can adjust
system-wide scheduling accordingly. Alternately, personnel and
apparatus can be made aware if the temperature on a particular
stretch is approaching or already below freezing. Ice and snow are
notorious for causing railroad switch problems. In many parts of
the world, railroad switches have to be provided with heaters to
melt away ice and snow. The present invention can therefore be
embodied to better inform personnel when ice or snow is a valid
concern, or to automatically engage heaters when and only to the
actual extent needed.
[0038] Traditional, electrically monitored track switches are also
subject to another powerful force of nature, lightning. The
inherent conductive nature of railway rails and the typically long
paths that electrical wiring to and from track switches must travel
puts conventional electrical track switches and their control
systems at great risk. A lightning strike some distance up or down
a railway line can thus disable a track switch. Lightning strikes
anywhere along the electrical wiring path can also induce
electrical noise into the system that triggers false reports or
even burns out switch or control system components.
[0039] In contrast, the present invention is substantially
non-electrical. Aside from the control system 20, which can be
shielded easily, the present invention is simply not effected by
lightning unless it strikes so directly and powerfully that heat or
explosive force physically damages components. As for induced
electrical noise, the FBG 16 and the optical fiber 18 of the
present invention are immune to it.
[0040] Since the FBG 16 in each switch monitoring unit 10 can have
a unique resonant wavelength, the traffic at each of multiple
railroad switches 12 can be monitored distinctly. When a train
passes by or is at rest at the location of a railroad switch 12,
the rails are temporarily deformed by the weight of the train. By
appropriate attachment of a switch monitoring unit 10, this
deformation produces an instantaneous stretch or relaxation to the
FBG 16 that is proportional to the weight of the train. When
multiple switch monitoring units 10 (or the present inventive
switch monitoring units 10 together with other FBG-based railway
systems by the present inventor) are used along a railway track,
the direction and the speed of train movement can be determined.
With two units, determining direction can be as simple as seeing
which switch monitoring unit 10 is actuated first. Since the
position of each switch monitoring unit 10 is fixed, measuring the
amount of time for a train to travel from one to the other permits
speed calculation. Further, if three or more switch monitoring unit
10 are mounted at known positions, the acceleration of a train can
also be calculated. All of this additional information can permit
railway personnel and other appropriate authorities to insure more
efficient and safe railroad operations.
[0041] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only, and that the breadth and scope of the invention
should not be limited by any of the above described exemplary
embodiments, but should instead be defined only in accordance with
the following claims and their equivalents.
* * * * *