Method and apparatus for detecting railway activity

A highly reliable early warning system that can provide efficient detection of railway activity and early warning of dangerous railway conditions to train operators and to central dispatch control offices. The warning system has an acoustic sensor circuit coupled to the railway for detecting sound waves resulting from physical vibrations thereon, an acoustic analyzer unit for analyzing the sound waves detected on the railway to identify any suspect conditions thereon and to generate an alarm if such a suspect condition is identified, and an acoustic signal processing unit for storing detected sound waves in a sound file for quick retrieval and analysis. The alarm signal may be transmitted over any communications system to the central control office and to trains traveling on the dangerous track. The stored sound files may be locally retrieved or downloaded to a remote location over a cellular system, thus enabling the analysis of the actual sound generated by the dangerous condition to determine the cause therefore.

FIELD OF THE INVENTION 
This invention relates to warning systems, and more particularly to railway 
warning and alarm systems. 
BACKGROUND OF THE INVENTION 
Heretofore, railroad-crossing warning systems use pole lines connected to 
trackside devices to communicate vital train information to passing 
motorists and pedestrians. That is, present day railroad warning systems 
use pole lines to transmit a signal to a flashing light and a retractable 
gate to warn pedestrians and motorists that a train is approaching the 
railroad crossing. 
In addition, present day railroad warning systems use trackside devices to 
communicate critical railway acoustic activity over the pole lines. The 
usefulness of pole lines to report such activity has become suspect, 
however, due to their high cost of construction and maintenance, 
disadvantageous effect on the surrounding community, and susceptibility to 
adverse weather conditions. Moreover, presently there are no warning 
systems that provide early detection of railway activity (e.g. vandalism 
and dangerous conditions), and provide early warning of that activity to 
trains traveling on the railway and to a central train dispatch office. 
Some prior art systems use remote-controlled companion railway cars to 
explore the track immediately in from of the locomotive and immediately 
report back any vital alarm data to the locomotive via a private radio 
system. Such a system, however, does not provide a means for substantially 
identifying the actual problem that exists on the rail, nor does such a 
system provide early notice of such dangerous conditions (i.e. vandalism, 
fallen rocks, and defective rails) to a central train dispatch office 
monitoring the railway safety and railway traffic. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention is directed to a highly reliable early 
warning system that can provide efficient detection of railway activity 
and early warning of suspicious conditions to both train operators and a 
central dispatch office. To attain this, the present invention provides a 
warning system having an acoustic sensor circuit coupled to the railway 
for detecting sound waves resulting from physical vibrations thereon, an 
acoustic analyzer unit for analyzing the sound waves detected on the 
railway to identify any suspect conditions thereon and to generate an 
alarm if such a suspect condition is identified, and an acoustic signal 
processing unit for storing detected sound waves in a sound file for quick 
retrieval and analysis. 
In one embodiment of the invention, the acoustic sensor circuit has an 
acoustic sensor coupled to each rail of the railway through a sensing bar. 
The analyzer unit has a pair of filters coupled to the acoustic sensors, 
and a logic circuit coupled to the pair of filters. The acoustic signal 
processing unit has an analog to digital converter coupled to the acoustic 
sensors, and a digital signal processor coupled to the analog to digital 
converters and a controller having internal storage. 
In such an embodiment, each acoustic sensor monitors its respective rail 
for sound waves and outputs an analog signal (i.e. V1 for rail 1 and V2 
for rail 2) indicating the sound waves detected on thereon. The outputs V1 
and V2 are then communicated to the logic circuit of the acoustic analyzer 
unit through filters, and to the acoustic signal processing unit. To 
determine if a dangerous condition exists on either rail or both, the 
logic circuit compares the detected, filtered signals V1 and V2 to a 
predetermined threshold V.sub.o, and compares the absolute difference 
between signals V1 and V2 (i.e. .vertline.V2-V1.vertline.) to a 
predetermined threshold difference X.sub.o. If either of these comparisons 
reveal a condition above the threshold V.sub.o and/or X.sub.o, then the 
logic circuit generates an alarm signal. When such an alarm is detected, 
the acoustic signal processing unit converts the actual sound waves V1 and 
V2 into digital format and stores the digital information in a sound file 
for easy retrieval. As a result, suspect conditions on the rail can be 
detected at an early stage, and the actual sound waves that indicate a 
suspect condition can be retrieved, replayed and analyzed, thus providing 
early warning of and a means for identifying any dangerous conditions on 
the railway.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION 
Referring now to FIG. 1, there is shown one embodiment of a warning system 
according to the present invention, hereinafter referred to as warning 
system 10. As shown, warning system 10 has an acoustic detector circuit 
11, an acoustic analyzer 12, an acoustic signal processing unit 13, a 
wireless communications device 14, and a data communications device 15. 
Acoustic detector circuit 11 has an acoustic sensor 16 coupled to one rail 
through a sensing bar 18, and an acoustic sensor 17 coupled to the other 
rail through a sensing bar 19. The outputs of acoustic sensors 16 and 17 
are coupled to acoustic analyzer 12 and acoustic signal processing unit 
13. Acoustic analyzer 12 has filters 20 and a logic circuit 21 which is 
coupled to wireless communications device 14. Acoustic signal processing 
unit 13 has an analog to digital (A/D) converter 22, a digital signal 
processor 23 and a controller 24 which is coupled to data communications 
device 15. In addition, acoustic signal processing unit 13 has a serial 
port 25 for connecting to an external data retrieval device 26. 
In operation, acoustic sensors 16 and 17 detect sound waves on their 
respective rails through their respective sensing bars 18 and 19. That is, 
sensing bar 18 detects sound waves on its respective rail and outputs an 
analog signal V1, and sensing bar 19 detects sound waves on its respective 
rail and outputs and analog signal V2. Analog signals V1 and V2 are then 
sent through acoustic sensors 16 and 17, respectively, to acoustic signal 
analyzer 12 for possible alarm generation and to acoustic signal 
processing unit 13 for possible storage. 
Upon reaching acoustic signal analyzer 12, signals V1 and V2 are each 
passed through filters 20 which pass only a range of frequencies to logic 
circuit 21. Logic circuit 21 detects for unbalanced sound wave signals 
between the rails and for high pitched sound waves indicating a problem or 
a possible dangerous condition exists on the railway. If such an 
unbalanced condition or a high pitched sound is detected, logic circuit 21 
generates an alarm. 
For example, logic circuit 21 can detect unbalanced rail activity by taking 
the absolute value of the difference between V1 and V2 (i.e. 
.vertline.V2-V1.vertline.) and compare that to some threshold or 
acceptable difference between the rails X.sub.o. If the difference is 
greater than predetermined threshold difference X.sub.o, then logic 
circuit 21 generates an alarm signal indicating a possible problem between 
the rails. Likewise, logic circuit 21 can detect whether a single rail has 
a possible dangerous condition by comparing the individual signals V1 and 
V2 to some threshold V.sub.o. If the difference between V1 or V2 and 
V.sub.o is greater than zero, then logic circuit 21 generates an alarm 
signal indicating a possible problem with one or both of the rails. 
FIG. 2 shows a functional block diagram of one method of sensing acoustic 
soundwaves on the rail and generating an alarm signal if a problem is 
detected thereon. As shown, sensing bar 31 is coupled to one rail of the 
train track and sensing bar 32 is coupled to the other rail of the track. 
The acoustic waves V1 and V2 generated on the track by some activity (i.e. 
an approaching train or fallen rocks hitting the rail) are coupled to 
acoustic sensors 33 and 34, respectively, through sensing bars 31 and 32, 
respectively. The signals V1 and V2 are then sent through band pass 
filters 35 and 36, respectively, thus leaving filtered signals V1' and 
V2', respectively. Filtered signals V1' and V2' are then sent to logic 
circuit 37 which performs the signal analysis, as described above, to 
generate an alarm signal, if necessary. 
The sensing bars 31 and 32 can be made of a small diameter steel material 
having a fixed length with a constant resonant frequency. Acoustic sensors 
may be a piezoelectric type sensitive directional microphone with a 
built-in low noise amplifier. Such directional microphones convert the 
detected sound pressure to the electrical signals V1 and V2, wherein the 
frequency response of the directional microphone may range from 30 Hz to 
30 Khz. The dynamic sensitivity range of the microphones, however, should 
be very wide to insure proper detection for all possible acoustic sources. 
To avoid interference with existing track circuit operation, the sensors 33 
and 34 should be electrically isolated from the sensing bars 31 and 32. In 
addition, the acoustic sensors 33 and 34 and the sensing bars 31 and 32 
should be fully encapsulated and molded for electrostatic protection. 
Moreover, bandpass filters 35 and 36 are chosen to only pass the band 
frequencies of interest for the railroad application. 
Referring now back to FIG. 1, the alarm signal generated by logic circuit 
21 is sent to wireless trackside device 14 which communicates on a 
wireless communications system. As a result, wireless trackside device 14 
provides the means for transmitting the alarm signal over a wireless 
communications system to train operators and to central office 
dispatch/control centers for early warning of a possible dangerous 
condition on the track. 
One embodiment of such a wireless communications system is shown in FIG. 3, 
hereinafter referred to as wireless communications system 45. As shown, 
wireless communications system 45 has a plurality of wireless trackside 
devices 41 positioned along railroad track 40. The alarm signal generated 
at location 47 is transmitted over wireless communications system 40 
through wireless trackside devices 41 to control point 42, wherein the 
alarm signal is sent over a packet data network 43 to a central dispatch 
center 44. As a result, the communication of the alarm signal over 
wireless trackside devices 41 can be through any message-hopping method. 
As a result, after receiving the alarm signal, the wireless trackside 
devices 41 may broadcast both the alarm signal and an emergency message to 
warn train operators traveling on the railway upon which the dangerous 
condition was detected. 
In addition to sending the detected signals V1 and V2 to acoustic analyzer 
12, the detected signals V1 and V2 are also sent to acoustic signal 
processing unit 13, wherein the acoustic signals V1 and V2 are stored in a 
sound file for later retrieval. FIG. 4 shows a functional block diagram of 
one embodiment of the acoustic signal processing unit 13 shown in FIG. 1. 
As shown, detected analog signals V1 and V2 are input to A/D converters 51 
and 52, respectively, thus outputting digital signals V1" and V2" to 
digital signal processors (DSP's) 53 and 54, respectively. DSP's 53 and 54 
generally provide filtering, level detection, and sound waveform 
generation functions for the acoustic signal processing unit. In addition, 
DSP's 53 and 54 may also provide audio signature analysis for special 
function recognition, wherein the special functions include identifying 
the type of vandalism, the type and speed of a passing train, and track 
integrity monitoring. 
The acoustic signal processing unit also has a main controller 55 which 
provides control and interface functions and a storage device 56 for 
storing the sound waves. As a result, DSP's 53 and 54 may send digital 
sound waveforms or signal V1" and V2", respectively, to main controller 55 
for storage in storage device 56. 
As shown in FIG. 1, the alarm signal generated by logic circuit 21 is also 
sent to acoustic signal processing unit 13. That is, in referring to FIG. 
4, the alarm signal is sent to main controller 55. In addition, main 
controller 55 has two serial ports 57 and 58 which provide interfaces for 
remote download/alarm function (i.e. serial port 57) and local 
retrieval/maintenance function (i.e. serial port 58). As a result, a 
suspicious sound waveform file stored in storage device 56 may be 
downloaded to a dispatch center via a cellular data system, and may be 
retrieved locally via a personal computer (PC) or laptop computer through 
a sound card located therein. 
Thus, the warning system of the present invention provides early warning of 
dangerous conditions on a railway to both a central dispatch control 
office and oncoming trains, and a means for retrieving and analyzing the 
actual sound waves generated by such dangerous conditions to identify the 
actual problem thereon. 
The above description includes exemplary embodiments and methods of 
implementing the present invention. References to specific examples and 
embodiments in the description should not be construed to limit the 
present invention in any manner, and is merely provided for the purpose of 
describing the general principles of the present invention. It will be 
apparent to one of ordinary skill in the art that the present invention 
may be practiced through other embodiments.