WO1999051996A1

WO1999051996A1 - Method and apparatus for detecting harmonic rocking in railcars

Info

Publication number: WO1999051996A1
Application number: PCT/US1999/006985
Authority: WO
Inventors: David H. Halvorson; Ralph L. Kitson
Original assignee: Westinghouse Air Brake Company
Priority date: 1998-04-02
Filing date: 1999-03-31
Publication date: 1999-10-14
Also published as: AU3373199A

Abstract

An improved method and apparatus for detecting excessive harmonic rock in railcars (14) moving on rails (15) in which a signal processor (20) analyzes signals generated by a distance sensor (11) to determine whether the railcar (14) is experiencing excessive harmonic rock. The distance sensor (11) repeatedly measures the distance between railcar (14) and rail (15), or between railcar (14) and the railcar truck frame (17), then transmits measured distances to signal processor (20). Signal processor (20) determines harmonic rock amplitude and harmonic rock frequency. Signal processor (20) triggers alarm (16) if harmonic rock amplitude is excessive. Signal processor (20) triggers alarm (16) if harmonic rock frequency is excessive.

Description

Method and Apparatus for Detecting Haiaonie Rocking in Railcar3

Background

The present invention relates generally to the field of detecting undesired harmonic rocking motion in vehicles and more particularly to an improved method and apparatus to detect and signal excessive amplitude and frequency of the harmonic rocking motion of a railcar. The railcar harmonic rock detector uses information from a distance sensor to identify harmonic rock before such harmonic rock results in an accident or incident.

Railcars tend to bounce, rock, and sway when moving along railroad tracks. All these modes of vibration are undesirable because they may damage cargo or, in severe forms, result in derailment or other damage to equipment. In particular, harmonic resonance in such vibration may result in amplification of rocking motion until it becomes excessive and causes derailment or other accident or incident.

Severe harmonic rocking is a significant cause of freight car derailments in the United States and worldwide. Accidents caused by harmonic rock-off derailments over the past five years have caused over $16 million in damage in the United States.

The use of distance sensors on railcars is known in the prior art for such purposes as detecting the load on a railcar and controlling the braking system in response to the detected load. An example of the use of a distance sensor for purposes such as detecting load in a railcar and controlling the braking system in response to the detected load is disclosed in U.S. Patent No. 5,603,556 to Douglas D. link, which is incorporated her-in by reference. It is known that such sensors may be used to αetect that a derailment has occurred. One of the ways in wmch some embodiments of the present invention improve upon the prior art is that these embodiments of the present invention enable the detection not only of derailments that have occurred, but may also be used n detecting harmonic rock which may be a precursor to derailment. By detecting harmonic rock before derailment occurs, the present invention may aid in preventing derailment accidents and incidents and the resulting damage.

Known methods of detecting harmonic rock generally rely on expensive equipment used only in the detection of harmonic rock. For example, harmonic rock may be detected by use of an accelerometer attached to the railcar. Such methods, however, tend to be prohibitively costly in that the additional equipment required to detect harmonic rock adds excessively to the cost of operating the railcar. The present invention, in some embodiments, detects excessive harmonic rock before derailment using distance sensing equipment that may be used on the railcar for other purposes in addition to detecting harmonic rock.

The use of a distance measuring sensor instead of, for example, an accelerometer to detect harmonic rock is particularly advantageous because it may avoid the necessity for adding expensive new equipment. The railcar or equipment consist may be equipped with one or more distance measuring sensor. Such distance measuring sensors and associated processors may be used not only for detecting excessive harmonic rock, but also for such purposes as detecting the load on the railcar, as disclosed in U.S. Patent No. 5,603,556, which is expressly incorporated herein by reference. A particularly useful aspect of the present invention is its use to detect excessive harmonic rock of components which may also be used for other purposes on a railcar and train.

— 2 — The present invention relates generally to the detection and elimination of harmonic rock in moving railcars. The present invention preferably includes a detector and a signal processor. The detector measures the distance between the railcar and the rail or between the railcar and the supporting wheel assembly, here in after referred to as a "truck". The detector generates a series of signals corresponding to and denoting the instantaneous distance between the railcar and the rail (or railcar truck frame) as measured by the detector. The signal processor processes the series of signals denoting the measured instantaneous distance between the railcar and the rail (or railcar truck frame) . By processing the series of signals denoting the measured instantaneous distance between the railcar and the rail, the signal processor detects whether harmonic rock is occurring. If the processor determines that harmonic rock is occurring, the signal processor will in some embodiments then trigger an alarm. After the alarm is triggered, corrective action may be implemented to eliminate the harmonic rock. Corrective action may be implemented by a train operator alerted by the alarm, or may be implemented automatically in control systems responsive to the alarm.

Brief Description of the Drawings

Fig. 1 is a side view of a railway car equipped to detect undesirable vibration in accord with one embodiment of the current invention.

Fig. IA is a side view of a railway car equipped to detect undesirable vibration in accord with a second embodiment of the current invention. Fig. 2 is a schematic diagram of one embodiment of the harmonic rock detector of the present invention.

Fig. 3 is a block diagram illustrating an exemplary process of the present invention for detecting excessive harmonic rock.

— 4 — Detailed Description

In one embodiment the present invention may be used by railroads to improve safety in providing railroad transportation. Railroad transportation is any form of non- highway ground transportation that runs on rails or electromagnetic guideways, including but not limited to (a) commuter or other short-haul railroad passenger service in a metropolitan or suburban area and (b) high speed ground transportation systems that connect metropolitan areas, without regard to whether they use new technologies not associated with traditional railroads.

A derailment occurs when one or more than one unit of rolling stock equipment leaves the rails during train operations. Significant damage occurs every year in accident/incidents including derailments caused by harmonic rock off. Accident/incidents attributable to this cause are tabulated in the annual Accident Incident Bulletin published by the FRA. Additional railroad accident information is available from the Federal Railroad Administration, Office of Safety, RRS- 22, 400 Seventh Street S.W., Washington, D.C. 20590. One example of a particular problem solved by the present invention is the problem of accidents and incidents resulting from harmonic rock off.

On-track equipment is railroad rolling stock used to transport freight or passengers. It includes locomotives, railcars, maintenance equipment, and one or more locomotives coupled to one or more cars. A railcar is: (a) any unit of on- track equipment designed to be hauled by locomotives, or (b) any unit of on-track work equipment such as a track motorcar,

— 5 — highway-rail vehicle, push car, crane, or ballast tamping machine. A railcar includes on-track equipment designed to carry freight, railroad personnel, or passengers. The term railcar includes, for example, boxcars, covered hopper cars, flatcars, refrigerator cars, gondola cars, hopper cars, tank cars, cabooses, stock cars, ventilation cars, and special cars. It also includes on-track maintenance equipment and locomotives. A train is a locomotive or locomotives coupled with or without cars. A train may be made entirely of self-propelled units designed to carry passengers, freight traffic, or both.

Any observed phenomena can be classified as deterministic or nondeterministic. Deterministic data are those that can be described by a specific mathematical relationship. However, there are many data that are not deterministic, also called random, because each observation of the phenomena is unique. Any observation will represent only one of many possible results that might have occurred. Deterministic data described by a specific mathematical relationship can be categorized as periodic or non-periodic. Periodic data can be sinusoidal or complex periodic, representing a combination of two or more discrete frequencies in which the waveform exactly repeats itself. Non-periodic data includes transient data. A sample record is a single time history representing a phenomena observed over a finite length of time.

Railcars in motion tend to vibrate. The frequency of vibration in moving railcars is affected by many factors . Among these factors are the speed with which the train is moving; the load in the railcar; the load in adjacent railcars;- the condition of the track; and the condition of the railcar including its suspension system. Under certain conditions, these factors may combine to produce harmonic resonance in the

— 6 — vibration experienced by the railcar. When such harmonic resonance occurs, the amplitude of vibration may increase to the point of causing an accident or incident including possible derailment.

An embodiment of the railcar harmonic rock detector of the present invention uses a distance measuring sensor that measures the distance between a fixed location of the railcar and the rail. The distance sensor may be any type of distance sensing device including but not limited to ultrasonic sensors, optical sensors, acoustic sensors, or radar sensors. For example, some sensors of these types are described for measuring the load on a railcar in US Patent No. 5,603,556, which is expressly incorporated herein by reference.

The sensors described in the above-mentioned US Patent No. 5,603,556, must provide a constant output (with a given railcar load) to the brake controller in order to function reliably as a load sensor. Thus, load sensor output as described in the '566 patent must not be affected by the harmonic rocking of the car or other short term changes in the distance measurement. In order to provide a stable measure of load the load sensor described in the '556 patent must either have a sampling period that is much longer than the period of the harmonic rocking or multiple samples must be averaged over a period much longer than the harmonic rocking.

Harmonic rocking generally has a frequency of less than two cycles per second. Electronic sensors, for example, may have sampling frequencies from 5 to 10,000 samples per second. Because the sampling frequency of electronic sensors is generally much larger than the harmonic rocking frequency, averaging techniques are used to provide the load sensor output as described in the '556 patent. An embodiment of the present invention takes advantage of the instantaneous information from the distance sensor to determine the amplitude and frequency of the harmonic rocking of the railcar. Because the maximum harmonic rock frequency is in the range of 2 Hertz and the minimum sample frequency is greater than 5 Hertz, the Nyquist sampling criteria is satisfied. In one embodiment of the present invention the instantaneous samples can be used to determine the peak to peak amplitude of the harmonic rocking simply by subtracting the maximum distance measurement from the minimum distance measurement. This measurement can be smoothed by utilizing multiple peaks to provide a more average peak to peak value. The frequency of the harmonic rocking can be calculated by determining when the instantaneous distance measurements cross the average distance measurement and by determining whether the instantaneous measurement is increasing or decreasing. The harmonic rock period is then the time between successive positive (or negative) average distance crossings. Harmonic rock frequency is, of course, the reciprocal of the harmonic rock period. This measurement may also be smoothed by using multiple average crossings to provide a more average frequency value.

In an alternative embodiment of the present invention, harmonic rock frequency and amplitude may be calculated using a well known numerical technique such as, for example, a fast Fourier transformer. Others of skill in the art will recognize that equivalent techniques for calculating harmonic rock amplitude and frequency exist.

In one embodiment, the harmonic amplitude and frequency measurements can be compared to threshold limits to determine whether the railcar is operating in a "safe region". If either the amplitude or frequency is outside the safe operating limit,

— 8 — an alarm may be used to indicate a potentially unsafe operating condition. The train's speed may then be adjusted to reduce the harmonic rocking to a safer level. By providing near real-time detection of excessive harmonic rocking, the train crew may be able to avoid a derailment. The detection of excessive harmonic rocking will indicate that either the track or the railcar is in need of maintenance to prevent future occurrences of excessive harmonic rocking. Since it is expected that distance sensors will be installed on many or all railcars in a train, alerts from many railcars would indicate a problem with the track while isolated alerts would indicate a problem with the railcar or the specific sensor.

If harmonic rock is detected in only a single railcar on the train, it is possible that -there is some problem with the railcar or with the detector itself. Possible problems with the railcar would include, for example, defects or wear in the suspension or undercarriage of the railcar producing excessive harmonic rock. A problem in the sensor itself may result, for example, from mechanical or electrical failure or defect in the system. In either case, the railcar may be separately inspected to identify and correct the cause of the problem.

If harmonic rock is detected from multiple railcars simultaneously, it is unlikely that the detecting results from defects in the particular railcars or the particular sensors. The persons controlling the train may then take corrective action to dampen or eliminate the harmonic rock. Alternatively, automatic systems responsive to the harmonic rock detector may take corrective action automatically. Such corrective action may include altering the speed of the train. By taking such corrective action when harmonic rock is first detected, it may

— 9 — be possible to avoid derailment or other accidents resulting from harmonic rock.

Fig. 1 illustrates one exemplary embodiment of a rail car harmonic rock detector (10) in accordance with the invention. A distance sensor (11) is mounted on a railcar (14) riding on a rail (15) . A distance sensor (11) may be mounted underneath the railcar (14) (but may be mounted elsewhere) and senses the instantaneous distance between the railcar (14) and the rail (15). The distance sensor (11) operates to measure the instantaneous distance between the railcar (14) and the rail (15) . The distance sensor (11) transmits to a signal processor (20) the measured distance between the rail (15) and the railcar (14). The distance sensor (11) measures the distance between the railcar (14) and the rail (15) repeatedly, then transmits the measurements to the signal processor (20) . In one embodiment, the time between measurements is fixed so that the distance is measured periodically. In alternative embodiments the time between distance measurements may vary. For example, the distance sensor (11) may transmit to the signal processor (20) both the distance measured between the railcar (14) and the rail (15) and the time at which the distance was measured or the signal processor (20) may poll the sensor at selected times. In another alternative embodiment, the distance sensor (11) may transmit to the signal processor (20) both the distance measured between the railcar (14) and the rail (15) and the time interval elapsed between the current distance measurement and the prior distance measurement. The signal processor (20) processes the information received responsive to the distance sensor (11). In some embodiments, the signal processor (20) determines whether the railcar (14) is experiencing excessive harmonic rock relative to the rail (15) . In an alternative embodiment, the

— 10 — signal processor (20) analyzes data received from the sensor to determine information relevant to harmonic rock, then displays this information in a suitable format (which may, for example, be tabular or graphical) for an observer such as, for example, a train operator to determine if harmonic rocking is excessive. If the railcar (14) is experiencing excessive harmonic rock relative to the rail (15), the signal processor (20) generates a signal indicating harmonic rock. An alarm (16) responsive to the signal generated by the signal processor (20) may be provided to indicate excessive harmonic rock.

Fig. IA illustrates an alternate embodiment of a rail car harmonic rock detector (10') in accordance with the present invention. A distance sensor (11') is mounted on a railcar (14') riding on a rail (15'). A distance sensor (11') mounted underneath the railcar (14') and senses the instantaneous distance between the railcar (14') and the railcar truck frame (17). The distance sensor (11') operates to measure the instantaneous distance between the railcar (14') and the railcar truck frame (17). The distance sensor (11') transmits to a signal processor (20') the measured distance between the railcar truck frame (17) and the railcar (14'). The distance sensor (11') measures the distance between the railcar (14') and the railcar truck frame (17) repeatedly, then transmits the measurements to the signal processor (20'). In one embodiment, the time between measurements is fixed so that the distance is measured periodically. In alternative embodiments the time between distance measurements may vary. For example, the distance sensor (11') may transmit to the signal processor (20') both the distance measured between the railcar (14') and the railcar truck frame (17) and the time at which the distance was measured, or the signal processor (20') may poll the sensor at

— 11 — selected times. In another alternative embodiment, the distance sensor (11') may transmit to the signal processor (20') both the distance measured between the railcar (14') and the railcar truck frame (17) and the time interval elapsed between the current distance measurement and the prior distance measurement. The signal processor (20') processes the information received responsive to the distance sensor (11') . In some embodiments, the signal processor (20') determines whether the railcar (14') is experiencing excessive harmonic rock relative to the rail (15). In an alternative embodiment, the signal processor (20') analyzes data received from the sensor to determine information relevant to harmonic rock, then displays this information in a suitable format (which may, for example, be tabular or graphical) for an observer such as, for example, a train operator to determine if harmonic rocking is excessive. If the railcar (14') is experiencing excessive harmonic rock relative to the rail (15), the signal processor (20') generates a signal indicating harmonic rock. An alarm (16) responsive to the signal generated by the signal processor (20') may be provided to indicate excessive harmonic rock.

In the illustrated embodiment of Fig. 2, the harmonic rock detector (10) includes a distance sensor (11) and a signal processor (20) . Those of ordinary skill in the art will appreciate that the distance sensor (11) may be of various types and that the depiction of Fig. 2 similarly applies to the system of Fig. IA. For example, the distance sensor (11) may be of the type disclosed in U.S. Patent 5,603,556, which is incorporated herein by reference. The distance sensor (11) may include a signal generator for generating and directing a pulse or signal coward the rail (15) and a receiver for receiving a reflected signal as it is reflected from the rail (15) . The distance

— 12 — sensor (11) may be, for example, a radar type device, but may also be any other type of position or distance sensors including but not limited to optical sensors, acoustical sensors, ultrasonic sensors, electronic sensors, magnetic sensors, or electromagnetic sensors.

The signal processor (20) in the illustrated embodiment of Fig. 2 is coupled with the distance sensor (11) and is responsive to the distance sensor (11) . Those of ordinary skill in the art will appreciate that signal processor (20) may be of various types. For example, the signal processor (20) may be a programmable digital computer of the 8-bit variety. The signal processor (20) may also be another form of programmable digital computer, a form of analog computer, a signal processing discrete circuit, or any other , form of signal processor known to those of skill in the art. The signal processor (20) in the illustrated embodiment of Fig. 2 is capable of receiving signals or data at the same rate at which the distance sensor (11) transmits signals or data representing the measured distance between the railcar (14) and the rail (15).

The alarm (16) may be of various types which are known to those of skill in the art. For example, the alarm (16) may generate a visual and audible signal detectable by those operating the train who may, for example, change the train's speed in response thereto. Alternatively, alarm (16) may be coupled to the train' s control systems to take corrective measures automatically in response to detected harmonic rock. Such corrective measures may include, for example, altering the speed of the train. Alternatively, an embodiment of the present invention may include no separate alarm but only an interconnection between the signal procession or (20) on the train's control systems.

~ 13 — Fig. 3 illustrates one embodiment of a method by which the present invention detects harmonic rock in railcars. In distance measurement step (51), the distance sensor process (50) detects the distance between the rail and the railcar. The frequency with which this distance is measured in the illustrated embodiment should be about twice the maximum frequency of harmonic rock or greater. In data signaling step (52) , the distance sensor process (_.50) passes the measured distance to a signal processor process (60) for analysis to determine if excessive harmonic rock is occurring. In the repetition step (53) , the distance measurement step 51 and the data signaling step (52) are repeated.

In data collection step (61) of the illustrated embodiment of the signal processing process (60) , a sample record is constructed from a series of distance measurements . The sample record is initialized using the first distance measurement. The sample record is constructed by waiting for a distance measurement to be passed from the distance sensor process (50) , then annexing that distance measurement to previously passed distance measurements. The greater the total number of distance measurements used for a given sample record, the longer the time interval over which motion is sampled. Virtually any number of distance measurement can be used to construct a sample record. For a measurement frequency of 38 hertz, sample records have been constructed using 128 distance measurements and using 256 distance measurements. After a full sample record has been constructed, when a new distance measurement is received from the distance sensor (11) , the oldest distance measurement is removed from the sample record.

In a calculation step (62) in the illustrated example process of Fig. 3, the amplitude and frequency of harmonic rock

— 14 are calculated using the data in the sample record. In one embodiment, approximate peak to peak amplitude may be calculated by subtracting the minimum distance measurement from the maximum distance measurement. This measurement may be smoothed by using multiple peaks to provide a more average peak to peak value. The frequency of harmonic rocking may be calculated by determining when in the sample record the instantaneous measurements pass across the average distance measurement and by determining whether the instantaneous measurement is increasing or decreasing. The harmonic rock period is then the time between two successive crossings in the same direction of instantaneous data over the average distance.

Harmonic rock frequency may be calculated from harmonic rock period by methods well-known to those of skill in the art. Those of ordinary skill in the art will recognize that other methods may be employed to determine amplitude and frequency of harmonic rock from the sample record. For example, in another embodiment, the well known frequency analysis algorithm, fast fourier transform (FFT) may be used. In general, any computational method by which amplitude and frequency of harmonic rock may be calculated from a sample record is acceptable and equivalent. The most desirable method will depend on multiple factors including such factors as computational power of the signal processor process (60) .

In a comparison step (S3) of the illustrated example process of Fig. 3, the calculated values of harmonic rock amplitude and frequency are compared to threshold limits or to acceptable range of amplitude and frequency to determine if harmonic rock poses a danger. The threshold limit or acceptable range values of amplitude and frequency may be stored permanently in the signal processor process (60) or dynamically

~ 15 — determined. The threshold limit value or acceptable range values are thus trigger values.

If the threshold limit or acceptable range values are exceeded, then, in the illustrated example process of Fig. 3, the signal processor process (60) generates an alarm signal in an alarm step (64) . In the alarm step (64), an alarm signal is generated in response to signal processor process (60) detecting excessive harmonic rocking in comparison step (63) . After comparison step (63) and (if indicated) alarm step (64), repetition step (65) repeats data collection step (61), calculation step (62), comparison step (63), and (if indicated) alarm step (64). Alternatively, the signal processor (20) may provide the amplitudes and frequency to a display or control system. >

In one specific embodiment, the distance sensor (11) is a radar type sensor for measuring the height of the railcar (14) above the rail (15) . One type of distance sensor (11) tested is a Micropower Impulse Radar Rangefinder from Lawrence Livermore National Laboratories. For sensing height of the railcar (14) above the rail (15), the radar is set to scan about 38 times per second. With a scan rate of 38Hz, a sample of 128 to 256 scans gives good results with considerable harmonic rocking revealed in the instantaneous data. The detector is mounted to minimize errors in distance measure due to effects such as misalignment of the detector and curvature of the tracks. For example, the detector may be mounted close to the wheel so as to minimize effects from curvature of the track.

Those of ordinary skill in the art will appreciate the various trade-offs associated with installation of the distance sensor (II) in different places on the railcar. Installation of the distance sensor (11) will be important for highly reliable

— 16 — operation. For example, the optimum result, the installation should precisely point the distance sensor (11) at the center of the railhead. In embodiments in which the distance sensor (11) is a radar, the beam of the radar can be optimized by configuring it as close to perpendicular to the railhead as possible. Combinations of low height mounting, long cars, and center of the car mounting reduce performance. It is advantageous to keep other reflectors out of the radar beam, especially those reflectors that are closer to the radar than the desired target. Also, in some embodiments, performance can be improved if the package is designed to minimize the opportunity for ice and slush to stick to the radar.

Rail height sensing using a radar range finder may, for example, use an antenna beam width of about 60 degrees in order to minimize missed targets, where 60 degrees is the interior angle of a cone. Missed targets in rail height sensing are due to such problems as installation pointing errors, car rocking, truck hunting, side-to-side motion due to wheel-to-rail flange clearance, and track curvature.

It is believed that better results may be achievable in a radar range finder by referencing the leading edge of the pulse width output to the transmitter main bang. Also, two or more distance sensors (11) may be used for reliable measurements, especially on long cars .

In an alternative embodiment using a radar range finder, an automatic gain control is added to the receiver. This is done to compensate for the fact that the amplitudes of the reflections from the rail have considerable variation. This variation can occur due to misalignment between the radar and the rail that can cause the reflection to scatter. A minimum threshold stop was added to a constant fraction discriminator

— 17 — that s used to detect the leading edge of the reflection in the A-Scan output and toggle the pulse to a lower state. The minimum threshold stop eliminates spurious reflection signals and leakage signals. A first reflection capture may be added to keep the camera locked on the railhead when there are stronger reflections such as a switch plate just below the rail. Special antennas may be used to reduce leakage and optimize for the specific mounting.

The signal processor in a specific embodiment may comprise a single board 486 computer with a 6 megabyte PCMCIA solid state disk. In another embodiment for use in more economical applications, the signal processor may be an 8 bit computer with sufficient random access memory to store a sample record and sufficient read only memory to store signal processing programs and threshold limits .

While the foregoing description sets forth an embodiment of the present invention useful in detecting harmonic rock m railcars, those of ordinary skill in the art will appreciate that the practical application of the present invention is not limited to that environment. In particular, the alternative embodiments of the present invention may be implemented n other vehicles such as trucks for use in operations on highways or such as airplanes for use m operations on runways. Such alternative implementations different fields of art are believed to differ only substantially from the embodiment specifically described herein.

While particular embodiments of the Method and Apparatus for Detecting Harmonic Rocking in Railway Cars of the invention has been shown and described, it will be appreciated by those skilled n the art that changes and modifications may be made thereto without departing from the invention in its broader

— 18 — aspects and as set forth in the following claims. As is conventional, the use of the indefinite article in these claims means at least one, or one or more.

~ 19 —

Claims

ClaimsWhat is claimed is:

1. A device for detecting harmonic rock in a railcar on a rail, the device comprising: a detector configured for repeatedly making distance measurements between the railcar and the rail; a signal processor, coupled to the detector, which analyzes the distance measurements between the railcar and the rail to determine whether the railcar is experiencing harmonic rock and which generates a signal in response thereto.

2. A device for detecting harmonic rock in a railcar on a rail, said device comprising: means for measuring the distances between the moving railcar and the rail; means for using the distances between the railcar and the rail for determining the existence of harmonic rock.

3. A method for detection of harmonic rocking in a railcar, said method comprising: measuring distances between the railcar and the rail; and analyzing the distances to determine if the railcar is experiencing harmonic rock.

4. The device of claim 1, wherein said signal comprises an amplitude measurement and a frequency measurement.

5. The device of claim 4 wherein said amplitude and said frequency are then displayed.

ΓÇö 20 --

6. The device of claim 4 wherein the said amplitude and the said frequency are used to control railcar operations.

7. The device of claim 1, wherein the detector makes the distance measurements between the moving railcar and the rail at least 5 times per second.

8. The device of claim 1, wherein the signal processor comprises a general purpose computer programmed to detect excessive harmonic rock.

9. The device of claim 8 wherein: the general purpose computer is programmed to calculate harmonic rock amplitude from the distance measurements between the railcar and the rail; and the general purpose computer is programmed to compare harmonic rock amplitude to a fixed harmonic rock amplitude limit, and to signal that harmonic rock is excessive when harmonic rock amplitude transcends the fixed harmonic rock amplitude limit.

10. The device of Claim 8 wherein: the general purpose computer is programmed to calculate harmonic rock frequency from distances measured between the moving railcar and the rail; and the general purpose computer is programmed to compare harmonic rock frequency to a fixed harmonic rock frequency limit, and to signal that harmonic rock is excessive when harmonic rock frequency transcends the fixed harmonic rock frequency limit.

^┬½ 21 ΓÇö

11. The device of claim 1 wherein the signal processor calculates an approximate peak to peak amplitude by subtracting a minimum distance measurement from a maximum distance measurement.

12. The device of claim 1 further comprising:

An alarm activated in response to the signal processor signal when the signal processor determines that the railcar is experiencing excessive harmonic rock.

13. The device of claim 12 further comprising: a train having control systems wherein the control systems respond to the alarm to reduce harmonic rock.

14. The device of claim 1 wherein: the distances are measured at regular time intervals.

15. The device of claim 1 further comprising a timer for measuring a time interval between making distance measurements, wherein the signal processor analyzes the time interval.

16. The device of claim 1 wherein the detector is a radar-type device .

17. The device of claim 2 further comprising means for determining whether the harmonic rock frequency and the harmonic rock amplitude indicate excessive harmonic rock.

18. The method of claim 3 wherein the said analyzing includes a determination of whether harmonic rocking is excessive.

ΓÇö 22 ΓÇö

19. The method of claim 3 wherein measuring the distance between the railcar and the rail comprises: generating a signal characterized by a known speed of signal propagation; directing the signal from the railcar to the rail such that the signal is reflected from the rail to the railcar as a reflected signal; detecting the. reflected signal; and measuring the time between generating the signal and detecting the reflected signal; computing the distance traveled by the signal based on the time measured and the known speed of signal propagation.

20. The method of claim 3 further comprising: collecting the distances measured in a sample record and wherein the steps, of analyzing the distances measured further comprises analyzing said sample record.

21. The method of claim 3 wherein analyzing the distances measured to determine if the railcar is experiencing excessive harmonic rock further comprises: calculating an harmonic rock amplitude and an harmonic rock frequency; determining whether the harmonic rock amplitude indicates excessive harmonic rock; and determining whether the harmonic rock frequency indicates excessive harmonic rock.

ΓÇö 23

22. The method of claim 3 further comprising: comparing the detection of harmonic rock for a plurality of railcars .

23. The method of claim 3 wherein analyzing the distances further comprises calculating an appropriate peak to peak amplitude by subtracting a maximum distance from a minimum distance.

24. A device for detecting harmonic rock in a railcar having a railcar truck frame, said railcar on a rail, the device comprising: a detector configured for repeatedly making distance measurements between ,the railcar and the railcar truck frame; a signal processor, coupled to the detector, which analyzes the distance measurements between the railcar and the railcar truck frame to determine whether the railcar is experiencing harmonic rock and which generates a signal in response thereto.

25. A device for detecting harmonic rock in a railcar having a railcar truck frame, said railcar on a rail, said device comprising: means for measuring the distances between the moving railcar and the railcar truck frame; means for using the distances between the railcar and the railcar truck frame for determining the existence of harmonic rock.

ΓÇö 24 ΓÇö

26. A method for detection of harmonic rocking in a railcar having a railcar truck frame, said rail car on a rail, the method comprising: measuring distances between the railcar and the railcar truck frame; and analyzing the distances to determine if the railcar is experiencing harmonic rock.

27. The device of claim 24, wherein said signal comprises an amplitude measurement and a frequency measurement.

28. The device of claim 27 wherein said amplitude and said frequency are then displayed.

29. The device of claim 27 wherein the said amplitude and the said frequency are used to control railcar operations.

30. The device of claim 24, wherein the detector makes the distance measurements between the moving railcar and the railcar truck frame at least 5 times per second.

31. The device of claim 24, wherein the signal processor comprises a general purpose computer programmed to detect excessive harmonic rock.

ΓÇö 25 ΓÇö

32. The device of claim 31 wherein: the general purpose computer is programmed to calculate harmonic rock amplitude from the distance measurements between the railcar and the railcar truck frame; and the general purpose computer is programmed to compare harmonic rock amplitude to a fixed harmonic rock amplitude limit, and to signal that harmonic rock is excessive when harmonic rock amplitude transcends the fixed harmonic rock amplitude limit.

33. The device of Claim 31 wherein: the general purpose computer is programmed to calculate harmonic rock frequency from distances measured between the moving railcar and the railcar truck frame; and the general purpose computer is programmed to compare harmonic rock frequency to a fixed harmonic rock frequency limit, and to signal that harmonic rock is excessive when harmonic rock frequency transcends the fixed harmonic rock frequency limit.

34. The device of claim 24 wherein the signal processor calculates an approximate peak to peak amplitude by subtracting a minimum distance measurement from a maximum distance measurement.

35. The device of claim 24 further comprising:

26

36. The device of claim 35 further comprising: a train having control systems wherein the control systems respond to the alarm to reduce harmonic rock.

37. The device of claim 24 wherein: the distances are measured at regular time intervals.

38. The device of claim 24 further comprising a timer for measuring a time interval between making distance measurements, wherein the signal processor analyzes the time interval.

39. The device of claim 24 wherein the detector is a radar-type device .

40. The device of claim 25 further comprising means for determining whether the harmonic rock frequency and the harmonic rock amplitude indicate excessive harmonic rock.

ΓÇö 27 ΓÇö