Rail inspection system

Provided is a rail inspection system capable of accurately detecting a defect of a railroad rail. The system includes: a sensor part group that has a plurality of sensor parts having receiver coils, and first oscillator coils and second oscillator coils corresponding to the receiver coils being arranged in a line parallel in a width direction of a railroad rail to be inspected; an oscillation part that supplies an oscillation signal to each of the first oscillator coils and the second oscillator coils; and a detection part group that has a plurality of detection parts to detect, with respect to an output signal from each of the receiver coils when the sensor part group moves in a laying direction of the railroad rail, a first inspection signal corresponding to a first phase of the output signal and a second inspection signal corresponding to a second phase of the output signal.

TECHNICAL FIELD

The present invention relates to a rail inspection system.

BACKGROUND OF THE INVENTION

As a background art in this technical field, there is disclosed in Patent Document 1. A defect such as a crack may occur in a rail used for a railroad or the like. When such a kind of defect is left, a problem such as a breakage of the rail occurs. Thus, preferably, a nondestructive inspection is performed regularly on the rail. For example, the abstract of the following PTL 1 describes that “according to one embodiment, the present technique provides a testing apparatus for testing material integrity in an object. The testing apparatus includes an electrical conductor and a sensing device. In the exemplary testing device, the electrical conductor extends in a generally linear direction and is configured to route current in a direction generally transverse to a longitudinal axis of the object being tested. Routing of current through the electrical conductor creates remote field eddy current effect, which, in turn, affects a magnetic field around the test object. The testing apparatus also includes a sensing device located at a distance from the electrical conductor and configured to detect magnetic fields generated in response to current routed through the electrical conductor.”

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved

In the technique of Patent Document 1, the magnetic field generated by the eddy current is detected. However, the magnitude of the eddy current is inversely proportional to the square of the distance between testing apparatus and the test object (railroad rail). Thus, an error generated by a vibration of a measuring vehicle (a railroad vehicle for inspecting a state of a track or an overhead line) becomes large, and it is difficult to accurately detect the defect of the railroad rail.

The invention has been made in consideration of the above situation, and an object thereof is to provide a rail inspection system which can accurately detect a defect of a railroad rail.

Solution to Problems

In order to solve the above problem, a rail inspection system of the invention includes: an oscillation part which outputs an oscillation signal of a predetermined frequency; a plurality of sensor parts which face a railroad rail of an inspection target and are arranged in a direction of crossing a laying direction of the railroad rail and which each includes a receiver coil and a first oscillator coil and a second oscillator coil which generate AC magnetic fields in directions opposite to each other with respect to a place where the receiver coil is provided when the oscillation signal is supplied; and a plurality of detection parts which detect a first inspection signal corresponding to a first phase of an output signal and a second inspection signal corresponding to a second phase of the output signal with respect to the output signal output from each of the plurality of receiver coils when the plurality of sensor parts move in the laying direction of the railroad rail.

Advantageous Effects of The Invention

According to the invention, the defect of the railroad rail can be detected accurately.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Configuration of First Embodiment

FIG. 1is a schematic view of a rail inspection system1according to a first embodiment of the invention.

InFIG. 1, the rail inspection system1has a detector2, a processor3, and a cable60connecting both. For example, the rail inspection system1is mounted on a self-propelled measuring vehicle200. The detector2is installed in a position of facing the railroad rail100as an inspection target object, and the processor3is installed in a chamber of the measuring vehicle200.

FIG. 2is a perspective view of the detector2.

InFIG. 2, the detector2has a casing20which is formed in a hollow rectangular parallelepiped shape and a flange25which is fixed on the upper surface of the casing20and has a rectangular plate shape. Through holes25a are formed at four corners of the flange25. In addition, a screw hole (not illustrated) is provided at the position of facing the through hole25a in a place where the detector2is arranged in the measuring vehicle200. A bolt is inserted into the through hole25a, and the bolt is fastened to the screw hole, whereby the detector2is fixed in a predetermined position of the measuring vehicle200. When the detector2is fixed at the predetermined position, the center of the railroad rail100coincides with the center of the detector2. For this reason, the flange25serves as a tool for installing the detector2at the predetermined position in the railroad rail100. A sensor part group21and an amplification filter part group22are fixed on the bottom surface of the casing20.

FIG. 3is a partially cut-away plan view of the detector2.

InFIG. 3, the sensor part group21has a plurality of N (N is plural) sensor parts21-1to21-N which are arranged in a line parallel in a width direction of the railroad rail100. In addition, the amplification filter part group22has the same number of amplification filter parts22-1to22-N. The sensor parts21-1to21-N have oscillator coils5A-1to5A-N (first oscillator coil), the oscillator coils5B-1to5B-N (second oscillator coil), and receiver coils6-1to6-N, respectively. These coils are configured by winding a coated copper wire.

The oscillator coil5A-k (where 1≤k≤N), the receiver coil6-k, and the oscillator coil5B-k are arranged along in a laying direction of the railroad rail100(seeFIG. 1). The receiver coil6-k is arranged to have equal intervals between the oscillator coil5A-k and the oscillator coil5B-k. In the oscillator coils5A-k and5B-k, an alternating current of a predetermined oscillation frequency f (predetermined frequency) is supplied from the processor3(seeFIG. 1) through the cable60. Accordingly, an AC magnetic field is generated from each of the oscillator coils5A-k and5B-k. In the receiver coil6, an induced voltage is generated by interlinked magnetic flux.

The amplification filter parts22-k performs an amplifying and filtering processing on the induced voltage generated in the receiver coil6-k and transmits the result thereof to the processor3through the cable60(seeFIG. 1). The processor3performs an analysis processing on the received signal and detects the defect of the railroad rail100.

In order to generate the above-described AC magnetic field in the detector2, the casing20is preferably made non-magnetic, and a material such as a glass epoxy excellent in an impact resistance and an environmental resistance is preferably used in consideration of outdoor use. In order to prevent the position of each sensor part from being changed by the vibration or the impact, the internal space of the casing20is preferably formed to have a resin mold structure. In addition, a center line CL of the N sensor parts21-1to21-N preferably corresponds to the center of the detector2.

Principle of Defect Detection

FIGS. 4A and 4Bare explanation diagrams of a principle of defect detection according to the present embodiment.

In the oscillator coils5A-k and5B-k, the winding starts or the winding ends of the coated copper wires are connected in series (or in parallel) to each other. When the current is supplied from the processor3, the AC magnetic field of which the phase is inverted is generated. More specifically, the oscillator coils5A-k and5B-k may be connected in series (or in parallel), and an AC voltage may be applied to the series circuit (or parallel circuit). Magnetic fluxes ϕA and ϕB generated by the oscillator coils5A-k and5B-k are propagated to the tread of the railroad rail100through air, so as to generate the flow of the magnetic flux in the railroad rail100.

FIG. 4Aillustrates an example in a case where the vicinity of the receiver coil6-k has no defect particularly such as a crack in the railroad rail100.

In the magnetic fluxes ϕA and ϕB, the components interlinked in the receiver coil6-k have the opposite direction of the magnetic flux, so as to cancel each other. Accordingly, the interlinkage magnetic flux of the receiver coil6-k becomes almost zero, and the induced voltage of the receiver coil6also becomes almost zero. Herein, when the measuring vehicle200(seeFIG. 1) travels, the detector2generates the flow of the magnetic flux on the railroad rail100while moving. Further, the flow of the magnetic flux is constant in the place where there is no defect. Thus, the induced voltage of the receiver coil6becomes almost constant (0).

FIG. 4Billustrates an example in a case where a defective portion102which is a crack is formed in the vicinity of the receiver coil6-k in the railroad rail100. In the illustrated example, the flow of the magnetic flux is disturbed, and the leakage of the magnetic flux occurs from the tread of the railroad rail100. For this reason, when the receiver coil6-k passes near the defective portion102, the induced voltage of the receiver coil6-k becomes a relatively large value.

The defect detection according to the present embodiment detects the generated leakage magnetic field on the basis of the fact that the flow of the magnetic flux generated in the railroad rail100which is an inspection target object is changed in the defective portion102. As an analysis model of the leakage magnetic field, the leakage magnetic field generated in a space can be expressed on the basis of a dipole model. In this model, it is assumed that diamagnetic magnetic loads are uniformly distributed to both end portions of the uniformly-magnetized defective portion102, and the leakage magnetic field can approximate to the spatial magnetic field generated therefrom.

First, inFIG. 4B, it is assumed that the laying direction of the railroad rail100is set to an x direction, a depth direction of the defective portion102is set to a y direction, a direction perpendicular to the paper surface is set to a z direction (not illustrated), and the defective portion102has infinite length in the z direction. Then, spatial magnetic fields Hx and Hy of the x direction and the y direction at a point (x, y, 0) can be expressed by following Expressions (1) and (2).

In Expressions (1) and (2), the width of the defective portion102is set to2a,the depth of the defective portion102is set to d, and m is set as a magnetic load amount.

The magnetic load amount m is approximated by following Expression (3) by using a classical electromagnetic solution to the internal magnetic field of the spheroid present in the ferromagnetic body receiving uniform magnetization.

In Expression (3), H0indicates a magnetic field strength for excitation, n indicates an aspect ratio (d/a) of a crack, and p indicates a relative permeability. In the present embodiment, the receiver coil6-k detects the leakage magnetic field from a direction perpendicular to the laying direction of the railroad rail100as the inspection target object, and the measurement result corresponds to a spatial magnetic field Hy. When parameters other than x are set on the basis of Expression (2), the spatial magnetic field Hy can be expressed as a function of the depth d of the defective portion102, and Hy indicates a change in which a maximum or a minimum appears in an x-axis direction with a central position of the defective portion102as a zero position.

Circuit Configuration of First Embodiment

FIG. 5is a block diagram illustrating the overall configuration of the rail inspection system1according to the present embodiment.

As described above, the rail inspection system1has the detector2and the processor3. Further, the detector2has the sensor parts21-1to21-N of the sensor part group21and the amplification filter parts22-1to22-N. Each sensor part21-k (where 1≤k≤N) has the oscillator coils5A-k and5B-k and the receiver coil6-k.

In addition, the processor3includes amplification parts31-1to31-N, a digital-analog conversion part32, an oscillation part33, detection parts34-1to34-N, an analog-digital conversion part35, a memory part36, and an evaluation device4. Incidentally, the detection parts34-1to34-N are collectively referred to as the detection part group34.

The oscillation part33outputs a sine-wave digital oscillation signal of the predetermined oscillation frequency f (for example, 20 kHz). Incidentally, a frequency other than 20 kHz may be selected as the oscillation frequency f. However, the oscillation frequency f is preferably selected from the frequency in the range of 10 Hz to 100 GHz. This is because when the frequency f is lower than 10 Hz, the sensitivity of the receiver coil6is deteriorated, and when the frequency f exceeds 100 GHz, the impedance of the oscillator coils5A and5B is increased, thereby weakening the magnetic field. In addition, the frequency f is more preferably selected from the range of 1 kHz to 1 GHz, and still more preferably selected from the range of 10 kHz to 100 kHz.

Incidentally, in the railroad line which is actually operated, a circuit maybe configured to include the railroad rail100as a component and be referred to as a “track circuit”. This is because a traffic signal or the like is controlled by detecting whether or not the railroad vehicle is present in a specific section of the railroad, so as to prevent a collision accident. When the frequency used in the track circuit is close to the oscillation frequency f, the sensor parts21-1to21-N may malfunction. However, it is proven from experiments that an effect on the sensor parts21-1to21-N made when the frequency used in the track circuit is separated by ±7% or more from the oscillation frequency f can be almost ignored. Accordingly, the oscillation frequency f is preferably selected from the frequency separated by ±0.07 f or more from the frequency used in the track circuit.

InFIG. 5, the digital-analog conversion part32converts the digital oscillation signal output by the oscillation part33into an analog AC voltage. The amplification part31amplifies the AC voltage and applies the voltage to the oscillator coils5A-k and5B-k in each sensor part21-k (where 1≤k≤N). Accordingly, the AC magnetic field of which the phase is inverted is generated from the oscillator coils5A-k and5B-k.

In addition, the amplification filter parts22-k in the detector2performs the amplifying and filtering processing on a signal sent from the corresponding receiver coil6-k and transmits the signal to the detection part34-k of the processor3. Incidentally, the “filtering processing” is a low-pass filtering processing of mainly removing frequency components of the oscillation frequency f or more. In addition, the detection part34-k generates signals X, Y, R, and θ (these signal will be described in detail later) on the basis of the signal supplied from the amplification filter parts22-k by using a reference signal from the oscillation part33and supplies the signals to the analog-digital conversion part35. The analog-digital conversion part35converts each of the analog signals received from the detection parts34-1to34-N into a digital signal. The digital signal output by the analog-digital conversion part35is stored as data in the memory part36and is supplied to the evaluation device4.

Next, the evaluation device4will be described.

The evaluation device4includes the hardware of a general computer such as a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a HDD (Hard Disk Drive). An OS (Operating System), an application program, various kinds of data, and the like are stored in the HDD. The OS and the application program are developed in the RAM and executed by the CPU. InFIG. 5, the inner portion of the evaluation device4is illustrated with the function realized by the application program or the like as a block.

The evaluation device4includes a control part42, a data processing part43, an output processing part44, an operation input part45, a display part46, and a storage part47.

The evaluation device4executes an inspection processing program which specifies the defect of the railroad rail100on the basis of the inspection data received the detector2, the detection parts34-1to34-N, the analog-digital conversion part35, or the memory part36. Incidentally, in the present embodiment, the “inspection data” corresponds to data of all steps from the receiver coil6of the detector2to the evaluation device4.

The control part42reads the inspection data from the memory part36and controls an arithmetic processing or like. The data processing part43performs an inspection processing on the basis of the inspection data (details are described later). The display part46is a LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube) display, or the like which displays the inspection result or the like. The output processing part44causes the display part46to display the inspection result or the like. At that time, the output processing part44performs a processing for displaying the inspection result with a display format which is easy to understand visually by properly using a format of a graph or a table. The operation input part45is an information input unit such as a keyboard and a mouse. In the storage part47, the data processing part43stores data such as the processed inspection result. In addition, the data stored in the memory part36is also transferred to the storage part47. Incidentally, the data processing part43and the output processing part44load the program or the data stored in the storage part47in the control part42and execute the arithmetic processing to be realized.

FIG. 6is a block diagram of the detection part34-k (where 1≤k≤N).

A received signal SS from the amplification filter parts22-k is supplied to phase comparators74and76. In addition, a reference signal SR1supplied from the oscillation part33(seeFIG. 5) is delayed by time corresponding to the phase of 90° of the oscillation frequency f by a delay circuit72. The delayed reference signal SR1is referred to as a reference signal SR2. The reference signal SR1is supplied to the phase comparator76, and the reference signal SR2is supplied to the phase comparator74. The phase comparator76extracts the components synchronized with the reference signal SR1in the received signal SS. The extracted signal is filtered by a LPF (low-pass filter)80, and the LPF80outputs the result thereof as a cosine signal X (first inspection signal, displaying target signal).

In addition, the phase comparator74extracts the components synchronized with the reference signal SR2in the received signal SS. The extracted signal is filtered by a LPF78, and the LPF78outputs the result thereof as a sine signal Y (second inspection signal, displaying target signal). An arithmetic unit84calculates √(X2+Y2) and outputs the result thereof as an amplitude signal R (displaying target signal). In addition, the arithmetic unit82calculates an arctangent of (Y/X), that is, atan (Y/X) and outputs the result thereof as a phase difference signal θ (displaying target signal).

The detection part34-k supplies the above-described signals X, Y, R, and θ to the memory part36through the analog-digital conversion part35(seeFIG. 5). Incidentally, in the illustrated example, the detection part34-k outputs all the signals X, Y, R, and θ. However, the amplitude signal R and the phase difference signal θ may be calculated on the basis of the cosine signal X and the sine signal Y by the data processing part43(seeFIG. 5) as well as calculated by the detection part34-k.

Herein, the description is given about the reason why the detection part34-k detects the sine signal Y in addition to the cosine signal X. First, if the cosine signal X is emphasized, it is considered that the phase of the reference signal is set such that the amplitude of the cosine signal X is maximized. Then, the set phase is an optimum phase for detecting the cosine signal X. However, the received signal SS is independent for each of the sensor parts21-1to21-N, and the influence of the arrangement place or the manufacturing error is different for each of the sensor parts21-1to21-N. In addition, the optimum phase is varied also by a secular change or a temperature change. Accordingly, it is complicated to set the optimum phase of the reference signal with respect to each of the detection parts34-1to34-N.

The sine signal Y is a signal component which is shifted by a phase of 90° with respect to the excitation magnetic field which excites the rail. As in the present embodiment, when the sine signal Y is detected together with the cosine signal X, the amplitude signal R can be calculated in the arithmetic unit84(or the evaluation device4). Even in a case where the phase difference signal θ is varied, the value of the amplitude signal R becomes constant in principle. Thus, it is possible to omit the processing for optimizing the phase of the reference signal.

Operation of First Embodiment

FIG. 7is a flowchart of the inspection processing program executed by the data processing part43of the evaluation device4.

InFIG. 7, when the processing proceeds to step S2, the data processing part43acquires the inspection data from the storage part47. Next, when the processing proceeds to step S4, the data processing part43associates the position history information of the measuring vehicle200(seeFIG. 1) with the inspection data. The measuring vehicle200has a position measuring function, and the position on the track is sequentially recorded with time. In addition, the inspection data is stored in the storage part47in association with the data measurement time. Accordingly, in step S4, by such data, the inspection data is associated with the position on the track.

Next, the loop of steps S6, S8, and S10is repeated with respect to all the inspection data acquired in step S2. First, in step S6, the data processing part43determines whether or not the inspection data of the processing target is deviated from a reference range, that is, a range in which the data can be estimated to be normal. Herein, when it is determined “Yes”, the processing proceeds to step S8, and the data processing part43determines that the inspection data is abnormal.

On the other hand, when it is determined “No” in step S6, the processing proceeds to step S10, and the data processing part43determines that the inspection data is normal. Further, when the processing of step S6to S10are ended with respect to all the inspection data, the processing proceeds to step S12, the data processing part43causes the storage part47to store the determination result of the normality/abnormality of each inspection data and causes the display part46to display the determination result. Thus, the processing of this routine is ended.

Next, the display mode of the determination result in the above-described step S12will be described with reference toFIGS. 8A, 8B, and 8C.

FIG. 8Ais a plan view illustrating a specific example of the defective portion102formed in the railroad rail100. In the illustrated example, the defective portion102is a groove-shaped defect formed in a direction of crossing the railroad rail100.

FIG. 8Bis an example of a waveform chart of the cosine signal X, the amplitude signal R, and the phase difference signal θ in the vicinity of the defective portion102. Incidentally, the sine signal Y is not illustrated. However, the sine signal Y has the same shape of waveform as that of the cosine signal X (however, both amplitudes are different in general).

InFIG. 8A, the sensor part21-k (seeFIG. 3) moves at a constant speed from left to right. Then, the horizontal axis ofFIG. 8Bindicates the time and the position on the railroad rail100. In addition, the vertical axis ofFIG. 8Bis a “voltage” for the cosine signal X and the amplitude signal R and is an “angle” for the phase difference signal θ. During the section before time t1and after t3, the sensor part21-k is sufficiently separated from the defective portion102. In this case, the cosine signal X almost coincides with a predetermined offset value BL.

In the section of time t1to t2, a negative peak appears in the cosine signal X, and in the section of time t2to t3, a positive peak appears in the cosine signal X. In addition, the amplitude signal R has respective positive peaks in the section of time t1to t2and the section of time t2to t3. In addition, the phase difference signal θ has a substantially trapezoidal waveform.FIG. 8Bshows only each one system of the cosine signal X, the amplitude signal R, and the phase difference signal θ. However, actually, the signals X, Y, R, and θ are obtained in each of the sensor parts21-1to21-N. As illustrated inFIG. 8B, in the cosine signal X, continuous values are obtained along the laying direction of the railroad rail100, and N discrete values are obtained along the arrangement direction (the width direction of the railroad rail100) of the sensor parts21-1to21-N. Accordingly, the measured value of the cosine signal X can be expressed as two-dimensional data.

FIG. 8Cis a display example of the two-dimensional image130on which the two-dimensional cosine signal X is displayed with contour lines in the display part46by the data processing part43. InFIG. 8C, similarly toFIG. 8B, the horizontal axis corresponds to the time and the position on the railroad rail100. In addition, the vertical axis ofFIG. 8Cis a position of the arrangement direction of the sensor parts21-1to21-N (seeFIG. 3), that is, the direction of crossing the railroad rail100. In addition, a number such as “0”, “+10”, and “−10” in the vertical axis indicates a distance from the central position of the railroad rail100in mm units. Incidentally, the width of the tread of the railroad rail100is generally 65 mm.

InFIG. 8C, an area110is an area in which the cosine signal X is close to the offset value BL and is painted out by “green”, for example. In addition, an area114is an area in which the cosine signal X is close to the negative peak and is painted out by “blue”, for example. In addition, an area124is an area in which the cosine signal X is close to the positive peak and is painted out by “red”, for example. Areas111to113correspond to respective ranges of a plurality of stages from the offset value BL toward the negative peak and are set to have colors which vary in a stepwise manner from green toward blue.

In addition, areas121to123correspond to respective ranges of a plurality of stages from the offset value BL toward the positive peak and are set to have colors which vary in a stepwise manner from green toward red via yellow. Accordingly, the user can visually and clearly grasp the position of the defective portion102in the railroad rail100and the depth thereof.

Incidentally,FIG. 8Cshows an example in which the cosine signal X is displayed with contour lines. Instead of the cosine signal X or in addition to the cosine signal X, any one of the sine signal Y, the amplitude signal R, and the phase difference signal θ may be displayed with contour lines. In addition, in the example ofFIG. 8C, the colors of red, blue, green, and the like are associated with signal intensity. However, another display mode (such as lightness and saturation) maybe associated with the signal intensity.

Herein, the description is given about the defect which is generated in the railroad rail used actually. When the wheels of the railroad vehicle roll while coming into contact with the tread of the railroad rail, fatigue accumulates in the railroad rail, and then a crack occurs in a direction parallel to the tread, that is, in the horizontal direction. Such a crack is referred to as a “horizontal crack”. When fatigue further accumulates in the railroad rail in which the horizontal crack occurs, the horizontal crack may grow downward. In this way, the crack growing downward is referred to as a “lateral crack”. Since the lateral crack easily spreads, if it is overlooked, the railroad rail is broken at a high probability. According to the present embodiment, the detection signal corresponding to the depth d of the defect can be output. Thus, the present embodiment is advantageous particularly in that the existence of the lateral crack and the depth thereof can be detected accurately.

Effect of First Embodiment

As described above, in the present embodiment, the detection part group (34) is provided which has a plurality of detection parts (34-1to34-N) which detect the first inspection signal (X) corresponding to the first phase (0°) of the output signal and the second inspection signal (Y) corresponding to the second phase (90°) of the output signal with respect to the output signal output from each of the receiver coils when the sensor part group (21) moves in the laying direction of the railroad rail (100). Thus, the defect of the railroad rail can be detected accurately.

In the present embodiment, the output processing part (44) is further provided which outputs the intensity distributions of the displaying target signals (X, Y, R, θ) corresponding to the plurality of sensor parts (21-1to21-N) as the two-dimensional image (130) when the first inspection signal (X) and the second inspection signal (Y) or the result (R, θ) obtained by performing the arithmetic processing on the first inspection signal (X) and the second inspection signal (Y) are used as displaying target signals. Herein, the two-dimensional image (130) is a contour image in which the display mode (such as color, brightness, and saturation) is set to correspond to the intensity of the displaying target signal (X, Y, R, θ) and is an image in which the position of the railroad rail (100) in the laying direction and the position in the width direction are used as axes. Further, the displaying target signal (X, Y, R, θ) is a signal which has the intensity corresponding to the depth of the defective portion (102) formed in the railroad rail (100), and the two-dimensional image (130) is an image in which the depth of the defective portion (102) is expressed by the display mode (such as color, brightness, and saturation). By these features, the user can more accurately recognize the defect of the railroad rail.

Second Embodiment

Configuration of Second Embodiment

Next, a second embodiment of the invention will be described. Incidentally, in the following description, in some cases, the parts corresponding to respective parts inFIGS. 1 to 8are denoted by the same reference signs, and the description thereof is not given.

Before the configuration of the present embodiment is described, the above-described first embodiment is reviewed again. As illustrated inFIG. 4A, in a case where the railroad rail100has no defect such as a crack, in the magnetic fluxes ϕA and ϕB, the components interlinked in the receiver coil6-k cancel each other, so that the interlinkage magnetic flux becomes zero ideally.

However, when there is a difference between the shapes (such as inner diameter, outer diameter, and coil length) of the oscillator coils5A-k and5B-k, the magnetic fluxes ϕA and ϕB generated in both is not canceled in the receiver coil6-k, and the noise signal having the same frequency as that of the oscillation signal is output continuously from the receiver coil6-k. Naturally, when the processing accuracy of the oscillator coils5A-k and5B-k is made sufficiently high, the noise signal can be reduced to a level at which there is no problem in practical use. However, since the high processing accuracy of the oscillator coils5A-k and5B-k drives cost to increase, it is more preferable to apply an inexpensive coil with low processing accuracy. In this regard, according to the present embodiment, the noise signal is canceled electrically so as to lower the processing accuracy required for the oscillator coils5A-k and5B-k.

FIG. 9is a block diagram illustrating an overall configuration of a rail inspection system1aaccording to the second embodiment of the invention. The appearance configuration of the rail inspection system1aaccording to the present embodiment is similar to that of the first embodiment (seeFIGS. 1 to 3). In addition, the configuration of the detector2is similar to that of the first embodiment (seeFIG. 5). However, instead of the processor3(seeFIG. 5) of the first embodiment, a processor3ais applied in the present embodiment. Incidentally, inFIG. 9, the inner portion of the evaluation device4is not illustrated, but the configuration of the evaluation device4is also similar to that ofFIG. 5.

In the processor3a,correction signal generating parts50-1to50-N and subtraction parts52-1to52-N are provided to correspond to respective amplification filter parts22-1to22-N. Incidentally, the correction signal generating parts50-1to50-N are collectively referred to as a correction signal generating part group50, and the subtraction parts52-1to52-N are collectively referred to as the subtraction part group52. As described above, the noise signal of the oscillation frequency f is superimposed with the induced voltage output by each sensor part21-k (where 1≤k≤N), and the noise signal is amplified in the amplification filter parts22-k. In order to cancel the noise signal, the correction signal generating part50-k is configured to generate the correction signal having almost the same amplitude and phase as those of the noise signal.

The subtraction part52-k cancels the noise signal by subtracting the correction signal from the output signal of the amplification filter parts22-k. Accordingly, the signal obtained by cancelling the noise signal is supplied to the detection parts34-1to34-N. The configuration of the processor3aother than the above-described configuration is the same as that of the processor3(seeFIG. 5) of the first embodiment.

Operation of Second Embodiment

Next, the operation of the present embodiment will be described.FIG. 10is a flow chart of a main routine executed by the evaluation device4(more specifically, the data processing part43illustrated inFIG. 5) illustrated inFIG. 9.

InFIG. 10, when the processing proceeds to step S20, the evaluation device4performs a predetermined initial setting. Next, when the processing proceeds to step S22, the evaluation device4starts communication with the memory part36. Next, when the processing proceeds to step S24, the evaluation device4reads the device setting data from the storage part47. The device setting data includes data such as the amplitude and the phase of the above-described correction signal.

Next, when the processing proceeds to step S26, the evaluation device4determines whether or not the measurement start instruction is input from the user through the operation input part45(seeFIG. 5). Further, in step S26, the processing waits until the measurement start instruction is input. When the measurement start instruction is input, the processing proceeds to step S28, and it determines whether or not the user performs the correction parameter measurement operation by the operation input part45. Incidentally, the correction parameter is a parameter for designating the amplitude and the phase of each correction signal output by the correction signal generating parts50-1to50-N.

Herein, when it is determined “No”, the processing proceeds to step S32, and it is determined whether or not the user performs the data collection operation by the operation input part45. Herein, when it is determined “No”, the processing proceeds to step S36, and it is determined whether or not the user performs a measurement stop operation. Herein, when it is determined “No”, the processing proceeds to step S40, and it is determined whether or not the user performs a communication stop operation. Herein, when it is determined “No”, the processing returns to step S28. Thereafter, these steps are repeated until it is determined “Yes” in any of steps S28, S32, S36, and S40.

In step S28, when it is determined “Yes”, the processing proceeds to step S30. Herein, correction parameter measurement subroutines (FIGS. 11 to 13) to be described later are executed, the amplitude and the phase of each correction signal are determined, and then, the processing returns to step S28. In addition, when it is determined “Yes” in step S32, the processing proceeds to step S34. Herein, the evaluation device4executes a data collection processing. That is, the inspection data is collected through the detector2, and the processing returns to step S32.

In addition, when it is determined “Yes” instep S36, the processing proceeds to step S38. Herein, the evaluation device4stops the measurement of the correction parameter or the inspection data, and the processing returns to step S26. In addition, when it is determined “Yes” in step S40, the processing proceeds to step S42. Herein, the evaluation device4ends the communication with the memory part36and also ends the processing of this routine.

FIGS. 11 to 13are flowcharts of the correction parameter measurement subroutines executed by step S30described above.

In a case where the processing is executed, a railroad rail having no defect (close to a new one) is prepared as the railroad rail100illustrated inFIG. 1and is arranged to face the detector2. The correction parameter measurement subroutines illustrated inFIGS. 11 to 13are sequentially executed with respect to each of the correction signal generating parts50-1to50-N. Herein,FIGS. 11 to 13illustrate the content of the processing for measuring the correction parameter corresponding to one correction signal generating part50-k (where 1≤k≤N). That is, the processing illustrated inFIGS. 11 to 13is repeated N times to measure the correction parameters for all the correction signal generating parts50-1to50-N.

InFIG. 11, when the processing proceeds to step S102, the evaluation device4acquires the measurement data of a predetermined number of (a plurality of) samples. Herein, the “measurement data” is mainly data obtained by measuring the amplitude signal R. More specifically, first, the evaluation device4outputs the digital oscillation signal to the oscillation part33. Next, the evaluation device4sets the initial value of the correction parameter with respect to the correction signal generating part50-k which is a measurement target. Herein, the correction parameter includes an amplitude command value CAN_VOLT2for designating the amplitude of the correction signal and a phase command value CAN_PH1for designating the phase of the correction signal. That is, in step S102, the evaluation device4supplies the amplitude command value CAN_VOLT2and the phase command value CAN_PH1which are predetermined initial values to the correction signal generating part50-k. Accordingly, the correction signal generating part50-k supplies the correction signal having the set amplitude and phase to the subtraction part52-k.

When the oscillation part33outputs the digital oscillation signal, through the digital-analog conversion part32and the amplification part31-k, the oscillator coils5A-k and5B-k generate a magnetic flux, and the receiver coil6-k generates an induced voltage. The amplification filter parts22-k performs an amplification/filtering processing on the induced voltage and supplies the result to the subtraction part52-k. The subtraction part52-k subtracts the correction signal from the output signal of the amplification filter parts22-k and supplies the result thereof to the detection part34-k. Further, the detection part34-k calculates the amplitude signal R on the basis of the output signal of the subtraction part52-k. Accordingly, the measurement data of one sample of the amplitude signal R is obtained.

Herein, in order to secure the accuracy of the amplitude signal R, in step S102, the amplitude signals R of the plurality of samples (more preferably, five or more samples) are measured under the same conditions. Incidentally, instead of the detection part34-k calculating the amplitude signal R, the evaluation device4may calculate the amplitude signal R on the basis of the cosine signal X and the sine signal Y measured by the detection part34-k.

Next, inFIG. 11, when the processing proceeds to step S104, the evaluation device4calculates the average value of the measurement data of the amplitude signals R of the predetermined number of the acquired samples. The calculated average value is an average amplitude value R_p0. Next, when the processing proceeds to step S106, it is determined whether or not the average amplitude value R_p0is less than a predetermined average amplitude reference value R_pth. Incidentally, the average amplitude reference value R_pth is a sufficiently low value, for example, 0.005 V. Herein when it is determined “Yes”, the processing of this routine is ended. This means that the initial value of the correction parameter, that is, the initial values of the amplitude command value CAN_VOLT2and the phase command value CAN_PH1both are sufficiently reliable values, and the amplitude signal R becomes a sufficiently low value with respect to the railroad rail100having no defect. Accordingly, in such a case, the initial value as it is applied as a correction parameter, and this routine is processed.

On the other hand, when the average amplitude value R_p0is equal to or more than the average amplitude reference value R_pth, it is determined “No” in step S106, and the processing proceeds to step S108. Herein, a value of a predetermined variable referred to as an amplitude comparison value CAN_VOLT1is substituted for the amplitude command value CAN_VOLT2. Incidentally, at this time, the amplitude comparison value CAN_VOLT1is set to be a predetermined value slightly larger than zero.

Next, when the processing proceeds to step S110, similarly to the above-described step S102, the measurement data of the amplitude signal R is acquired. At that time, similarly to the case of step S102, the phase of the correction signal is a predetermined initial value. However, the amplitude of the correction signal is set to be the amplitude command value CAN_VOLT2(=amplitude comparison value CAN_VOLT1) set in previous step S108. Next, when the processing proceeds to step S112, on the basis of the measurement data of the amplitude signals R of the predetermined number of the acquired samples, the evaluation device4calculates an average amplitude value R_p1thereof. Next, when the processing proceeds to step S114, 1 is substituted for a stage number ST.

Herein, the meaning of the stage number ST will be described. In the present embodiment, the amplitude signal R is measured while gradually changing the amplitude and the phase of the correction signal generated by the correction signal generating part50-k, so as to obtain the amplitude and the phase in which the average value of the amplitude signal R becomes as small as possible. The result thereof is set to the correction parameter. Herein, a variation unit at the time of gradually varying the amplitude is referred to as an “amplitude increase/decrease value ΔV”. In addition, a variation unit at the time of gradually varying the phase is referred to as a “phase increase/decrease value ΔP”. Herein, the amplitude increase/decrease value ΔV and the phase increase/decrease value ΔP are not constant. The values are initially set to be a large value and gradually changed to a small value, so as to obtain accurate correction parameters as quickly as possible. The stage number ST indicates the stage of reducing the amplitude increase/decrease value ΔV and the phase increase/decrease value ΔP with natural numbers of 1 to 3.

Next, inFIG. 12, when the processing proceeds to step S120, the evaluation device4substitutes a voltage variation unit initial value ΔVD[ST] for the amplitude increase/decrease value ΔV. For example, the voltage variation unit initial value ΔVD[ST] is set to correspond to the stage number ST such that a voltage variation unit initial value ΔVD[1]=0.1 V, a voltage variation unit initial value ΔVD[2]=0.01 V, and a voltage variation unit initial value ΔVD[3]=0.001 V. When step S120is executed first, the stage number ST is 1. Thus, in the above example, the amplitude increase/decrease value ΔV is set to 0.1 V.

Next, when the processing proceeds to step S122, the evaluation device4substitutes the result obtained by adding the amplitude comparison value CAN_VOLT1and the amplitude increase/decrease value ΔV for the amplitude command value CAN_VOLT2. Next, when the processing proceeds to step S124, the measurement data of the amplitude signal R is acquired similarly to the above-described steps S102and S110. Also in this case, the phase of the correction signal is a predetermined initial value. However, the amplitude of the correction signal is the amplitude command value CAN_VOLT2obtained in step S122. Next, when the processing proceeds to step S126, on the basis of the measurement data of the amplitude signals R of the predetermined number of the acquired samples, the evaluation device4calculates an average amplitude value R_p2thereof.

Next, when the processing proceeds to step S128, the evaluation device4determines whether or not the average amplitude value R_p1is smaller than the average amplitude value R_p2. In the above example, the average amplitude value R_p1is an average amplitude value obtained in a case where the CAN_VOLT1is substituted for the amplitude command value CAN_VOLT2. In addition, the average amplitude value R_p2is an average amplitude value obtained in a case where “CAN_VOLT1+ΔV” is substituted for the amplitude command value CAN_VOLT2. If the former is smaller than the latter, the sign (positive or negative) of the amplitude increase/decrease value ΔV has a direction of increasing the average amplitude value and is considered to be an undesirable sign. In this regard, in such a case, when it is determined “Yes” in step S128, the processing proceeds to step S132. In step S132, the evaluation device4inverts the sign (positive or negative) of the amplitude increase/decrease value ΔV.

On the other hand, when it is determined “No” in step S128, the processing proceeds to step S130, and the evaluation device4substitutes the average amplitude value R_p2for the average amplitude value R_p1. This configuration is intended to hold the most preferable (small) value among the average amplitude values obtained previously as the average amplitude value R_p1. When the processing of step S130or S132is ended, the processing proceeds to step S134, and the evaluation device4substitutes the result obtained by adding the amplitude comparison value CAN_VOLT1and the amplitude increase/decrease value ΔV for the amplitude command value CAN_VOLT2.

Next, when the processing proceeds to step S136, the measurement data of the amplitude signal R is acquired similarly to the above-described steps S102and S110or the like. Next, when the processing proceeds to step S138, on the basis of the measurement data of the amplitude signals R of the predetermined number of the acquired samples, the evaluation device4calculates the average amplitude value R_p2thereof. Next, when the processing proceeds to step S140, the evaluation device4determines whether or not the average amplitude value R_p1is smaller than the average amplitude value R_p2.

Herein, when it is determined “No”, the processing proceeds to step S142, and the evaluation device4substitutes the amplitude command value CAN_VOLT2for the amplitude comparison value CAN_VOLT1and substitutes the average amplitude value R_p2for the average amplitude value R_p1. Accordingly, the most preferable (small) value among the average amplitude values R_p2obtained previously is held as the average amplitude value R_p1, and the amplitude command value CAN_VOLT2realizing the average amplitude value R_p1is held as the amplitude comparison value CAN_VOLT1. Further, the processing returns to step S134. Thereafter, as long as the average amplitude value R_p2is equal to or less than the average amplitude value R_p1, the loop of steps S134to S142is repeated.

Herein, when the average amplitude value R_p2obtained in step S138is larger than the average amplitude value R_p1, it is determined “Yes” in step S140, and the processing proceeds to step S144. Herein, the amplitude comparison value CAN_VOLT1is substituted for the amplitude command value CAN_VOLT2. At the time when step S144is ended, when the amplitude of the correction signal is varied with a unit of a present amplitude increase/decrease value ΔV (for example, 0.1 V), the most preferable amplitude (in which the amplitude signal R becomes smaller) is substituted for the amplitude comparison value CAN_VOLT1.

Next, inFIG. 13, when the processing proceeds to step S220, the evaluation device4substitutes a phase variation unit initial value ΔPD[ST] for the phase increase/decrease value ΔP. For example, the phase variation unit initial value ΔPD [ST] is set to correspond to the stage number ST such that the phase variation unit initial value ΔPD[1]=10°, the phase variation unit initial value ΔPD[2]=1°, and the phase variation unit initial value ΔPD[3]=0.1°. When step S220is executed first, the stage number ST is 1. Thus, in the above example, the phase increase/decrease value ΔP is set to 10°.

Next, when the processing proceeds to step S222, the evaluation device4substitutes the result obtained by adding a phase comparison value CAN_PH0and the phase increase/decrease value ΔP for the phase command value CAN_PH1. Incidentally, at this time, the phase comparison value CAN_PH0is the initial value of the phase among the initial values of the above-described correction parameters. Next, when the processing proceeds to step S224, the measurement data of the amplitude signal R is acquired similarly to the above-described step S102(seeFIG. 11). Next, when the processing proceeds to step S226, on the basis of the measurement data of the amplitude signals R of the predetermined number of the acquired samples, the evaluation device4calculates the average amplitude value R_p2thereof.

Next, when the processing proceeds to step S228, the evaluation device4determines whether or not the average amplitude value R_p1is smaller than the average amplitude value R_p2. Herein, when step S128or S142(seeFIG. 12) is executed last, the most preferable (small) value among the average amplitude values R_p2calculated previously is substituted for the average amplitude value R_p1. When it is determined “Yes” in step S228, the processing proceeds to step S232, and the evaluation device4inverts the sign (positive or negative) of the phase increase/decrease value ΔP.

On the other hand, when it is determined “No” in step S228, the processing proceeds to step S230, and the evaluation device4substitutes the average amplitude value R_p2for the average amplitude value R_p1. When the processing of step S230or S232is ended, the processing proceeds to step S234, the evaluation device4substitutes the result obtained by adding the phase comparison value CAN_PH0and the phase increase/decrease value ΔP for the phase command value CAN_PH1.

Next, when the processing proceeds to step S236, the measurement data of the amplitude signal R is acquired similarly to the above-described step S224. Next, when the processing proceeds to step S238, on the basis of the measurement data of the amplitude signals R of the predetermined number of the acquired samples, the evaluation device4calculates the average amplitude value R_p2thereof. Next, when the processing proceeds to step S240, the evaluation device4determines whether or not the average amplitude value R_p1is smaller than the average amplitude value R_p2.

Herein, when it is determined “No”, the processing proceeds to step S242, and the evaluation device4substitutes the phase command value CAN_PH1for the phase comparison value CAN_PH0and substitutes the average amplitude value R_p2for the average amplitude value R_p1. Accordingly, among the average amplitude values R_p2obtained previously, the most preferable (small) value is held as the average amplitude value R_p1, and the phase command value CAN_PH1realizing the average amplitude value R_p1is held as the phase comparison value CAN_PH0. Further, the processing returns to step S234. Thereafter, as long as the average amplitude value R_p2is equal to or less than the average amplitude value R_p1, the loop of steps S234to S242is repeated.

Herein, when the average amplitude value R_p2obtained in step S238is larger than the average amplitude value R_p1, it is determined “Yes” in step S240, and the processing proceeds to step S244. Herein, the phase comparison value CAN_PH0is substituted for the phase command value CAN_PH1. At the time when step S244is ended, when the amplitude of the correction signal is varied with a unit of a present phase increase/decrease value ΔP (for example, 10°), the most preferable phase (in which the amplitude signal R becomes smaller) is substituted for the phase command value CAN_PH1.

Next, when the processing proceeds to step S246, it is determined whether or not the stage number ST is 3. Herein, when it is determined “No”, the processing proceeds to step S248, and the stage number ST is incremented by 1. For example, if the previous stage number ST is 1, 2 is substituted for the stage number ST here. Further, the processing returns to step S120ofFIG. 12.

When the stage number ST is 2, in step S120, the voltage variation unit initial value ΔVD[2], for example, 0.01 V is substituted for the amplitude increase/decrease value ΔV, and the processing of the above-described steps S122to S144is executed. Next, when the processing proceeds to step S220ofFIG. 13, the phase variation unit initial value ΔPD[2], for example, 1° is substituted for the phase increase/decrease value ΔP, and the processing of the above-described steps S222to S244is executed. Next, when the processing proceeds to step S248through step S246, the stage number ST is incremented again, for example, to 3.

When the stage number ST becomes 3, in step S120, the voltage variation unit initial value ΔVD[3], for example, 0.001 V is substituted for the amplitude increase/decrease value ΔV, and the processing of the above-described steps S122to S144is executed. Next, when the processing proceeds to step S220ofFIG. 13, the phase variation unit initial value ΔPD[3], for example, 0.1° is substituted for the phase increase/decrease value ΔP, and the processing of the above-described steps S222to S244is executed.

With the above processing, the amplitude command value CAN_VOLT2and the phase command value CAN_PH1in which the amplitude signal R can be reduced sufficiently are obtained with respect to the railroad rail100having no defect. Next, when the processing proceeds to step S246, the stage number ST is 3, and thus it is determined “Yes”. Accordingly, the processing of the correction parameter measurement subroutines (FIGS. 11 to 13) is ended, and the processing returns to step S28of the main routine (FIG. 10).

Thereafter, when the inspection data is acquired by the data collection processing of step S34, the correction signal generating parts50-1to50-N output respective correction signals on the basis of the amplitude command value CAN_VOLT2and the phase command value CAN_PH1.

Effect of Second Embodiment

As described above, the present embodiment further includes the plurality of correction signal generating parts (50-1to50-N) which output the correction signals which have the same frequency as that of the oscillation signal and the amplitude and the phase different from those of the oscillation signal to the plurality of respective corresponding receiver coils (6-1to6-N), and the subtraction parts (52-1to52-N) which subtract the corresponding correction signals from the output signals of the plurality of sensor parts (21-1to21-N) respectively and supply respective subtraction results to the corresponding detection parts (34-1to34-N).

Accordingly, even in a case where the processing accuracy of the oscillator coils5A-k and5B-k (seeFIG. 4) is low, the noise signal can be cancelled electrically, and the defect of the railroad rail100can be detected precisely.

Third Embodiment

Next, a third embodiment of the invention will be described. Incidentally, in the following description, in some cases, the parts corresponding to respective parts inFIGS. 1 to 13are denoted by the same reference signs, and the description thereof is not given.

FIG. 14is a block diagram illustrating the overall configuration of a rail inspection system1baccording to the third embodiment of the invention. The appearance configuration of the rail inspection system1bof the present embodiment is similar to that of the first embodiment (seeFIGS. 1 to 3). In addition, the configuration of the detector2is similar to that of the first embodiment (seeFIG. 5). However, instead of the processor3(seeFIG. 5) of the first embodiment, a processor3b is applied in the present embodiment. Incidentally, inFIG. 14, the inner portion of the evaluation device4is not illustrated, but the configuration of the evaluation device4is also similar to that ofFIG. 5.

Similarly to the processor3a(seeFIG. 9) of the second embodiment, the processor3b of the present embodiment is provided with the correction signal generating parts50-1to50-N and the subtraction parts52-1to52-N in correspondence to respective amplification filter parts22-1to22-N. However, in the present embodiment, as illustrated inFIG. 14, individual oscillation part33-1to33-N are provided to correspond to the amplification filter parts22-1to22-N. These oscillation part33-1to33-N output the digital oscillation signals and the reference signals of oscillation frequencies f1to fN (predetermined frequency) different from each other.

The oscillation part33-k (where 1≤k≤N) supplies the digital oscillation signal of the oscillation frequency fk to the digital-analog conversion part32and the correction signal generating part50-k and supplies the reference signal of the oscillation frequency fk to the detection part34-k. The digital-analog conversion part32converts the digital oscillation signals of N channels into respective analog signals and supplies the analog signals to the sensor parts21-1to21-N. Accordingly, the receiver coil6-k of the sensor part21-k generates an induced voltage of the frequency fk, and the induced voltage is amplified and filtered by the amplification filter parts22-k.

The correction signal generating part50-k supplies the correction signal of the oscillation frequency fk to the subtraction part52-k, and the subtraction part52-k cancels the noise signal by subtracting the correction signal from the output signal of the amplification filter parts22-k. Accordingly, the signal obtained by cancelling the noise signal is supplied to the detection parts34-1to34-N. The configuration of the processor3bother than the above-described configuration is the same as that of the processor3(seeFIG. 5) of the first embodiment.

As illustrated inFIG. 3, in the detector2, the plurality of sensor parts21-1to21-N are arranged to configure the sensor part group21. However, when the magnetic flux having the same frequency is generated in the oscillator coils5A-1to5A-N and5B-1to5B-N as in the first and second embodiments, an interference may occur to each other. With respect thereto, according to the present embodiment ofFIG. 14, the different oscillation frequencies f1to fN are applied to respective sensor parts21-1to21-N. Thus, the mutual interference of the sensor parts21-1to21-N can be reduced. Incidentally, in a case where the railroad rail100configures apart of the track circuit, all the oscillation frequencies fk (where 1≤k≤N) are preferably selected among the frequencies separated ±0.07 fk or more from the frequency used in the track circuit.

As described above, according to the present embodiment, the oscillation parts (33-1to33-N) output the oscillation signals having different frequencies (f1to fN) to the plurality of sensor parts (21-1to21-N). Accordingly, the interference between the sensor parts (21-1to21-N) can be reduced.

Fourth Embodiment

Next, the fourth embodiment of the invention will be described. Incidentally, in the following description, in some cases, the parts corresponding to respective parts inFIGS. 1 to 14are denoted by the same reference signs, and the description thereof is not given.

In the above-described first to third embodiments, when the traveling speed of the measuring vehicle200(seeFIG. 1) increases, the rail inspection can be executed more quickly. However, when the traveling speed of the measuring vehicle200increases, the vibration of the measuring vehicle200is also increased, and the vibration affects each of the signals X, Y, R, and θ.

Herein, the effect accompanying the acceleration of the measuring vehicle200will be described with reference toFIG. 15. Incidentally,FIG. 15is an example of the waveform chart of the cosine signal X.FIG. 15is a waveform obtained by shortening the waveform of the cosine signal X illustrated inFIG. 8Balong the time axis, and time t1to t3illustrated inFIG. 15corresponds to time t1to t3illustrated inFIG. 8B.

A solid line inFIG. 15is an example of the waveform of the cosine signal X in a case where the speed of the measuring vehicle200is relatively low. In this case, in the section (before time t1and after t3) separated from the defective portion102(seeFIG. 8A), the level of the cosine signal X approximately coincides with the offset value BL. On the other hand, a two-dot chain line is an example of the waveform of the cosine signal X in a case where the speed of the measuring vehicle200is relatively high. When the speed of the measuring vehicle200is increased, the measuring vehicle200is vibrated, and the cosine signal X is varied also in the section separated from the defective portion. For this reason, the variation of the cosine signal X in time t1to t3when the defective portion102appears may be difficult to be distinguished from the variation caused by the vibration.

Hereinbefore, the description is given about the example of the cosine signal X. However, other signals Y, R, and θ are similarly varied by the vibration of the measuring vehicle200. In the present embodiment, the effect caused by the vibration of the measuring vehicle200is compensated to enable the measuring vehicle200to be operated at a higher speed.

Herein, in the section (before time t1and after t3) separated from the defective portion102, the waveforms of the signals Y, R, and θ are similar to the waveform of the cosine signal X. On the other hand, as described inFIG. 8B, the waveforms of the amplitude signal R and the phase difference signal θ in the defective portion102(time t1to t3) are clearly different from that of the cosine signal X. Incidentally, the waveform shape (not illustrated) of the sine signal Y is similar to that of the cosine signal X.

In this regard, for example, when a difference signal R-X is obtained which is the difference between the amplitude signal R and the cosine signal X, the difference signal R-X becomes almost 0 at the section (before time t1and after t3) separated from the defective portion102. On the other hand, at time t1to t3corresponding to the defective portion102, as illustrated inFIG. 8B, the waveform of the cosine signal X and the waveform of the amplitude signal R are different clearly. Thus, the difference signal R-X of both signals is considered to be a signal generating a relevant amplitude. Accordingly, when it is determined on the basis of the difference signal R-X whether or not the defective portion102is present, the effect caused by the vibration of the measuring vehicle200can be reduced.

Next, the configuration of the present embodiment will be described. The overall configuration of the present embodiment is similar to that (seeFIG. 14) of the third embodiment. However, the configuration of the place illustrated inFIG. 16is different. Incidentally,FIG. 16is a circuit diagram of the main parts of the rail inspection system1according to the present embodiment.

InFIG. 16, the detection part34-k (where 1≤k≤N) is similar to those (seeFIG. 6) of the first to third embodiments. In the present embodiment, gain adjustment parts90and92and a differential amplifier94are added to the latter part of each detection part34-k.

The gain adjustment parts90and92may set gains such that the levels of the cosine signal X and the amplitude signal R in the section having on defect become almost equal. Further, the differential amplifier94outputs the difference signal R-X which is the difference between the amplitude signal R and the cosine signal X of which the gains are adjusted. Further, in addition to the signals X, Y, R, and θ, the analog-digital conversion part35converts the difference signal R-X into the digital signal and supplies the signal to the evaluation device4through the memory part36. Further, the evaluation device4detects the defective portion102of the railroad rail100on the basis of the difference signal R-X. The configuration and the operation other than the above description of the present embodiment are similar to those of the third embodiment.

As described above, according to the present embodiment, the defective portion102of the railroad rail100is detected on the basis of the difference signal R-X. Thus, even in a case where the measuring vehicle200travels at high speed, the effect caused by the vibration of the measuring vehicle200can be reduced.

Modifications

The invention is not limited to the embodiments described above, and various modifications are possible. The above-described embodiments are exemplarily presented to comprehensively describe the invention, and thus, the invention is not necessarily limited to an invention including all the configurations described above. In addition, it is possible to replace a certain configuration in one embodiment with a configuration in another embodiment. Further, it is also possible to add a configuration in one embodiment to a configuration in another embodiment. In addition, it is possible to remove some configuration in each embodiment or to add or replace another configuration. In addition, the control lines and information lines illustrated in the drawings indicate what is considered to be necessary for explanation and do not necessarily indicate all control lines and information lines on products. In fact, almost all of the configurations maybe considered to be connected to each other. Examples of possible modifications of the above-described embodiments include the following.

(1) The hardware of the evaluation device4in the above-described embodiments can be realized by a general computer. Thus, the program or the like according to the flowchart illustrated inFIGS. 7 and 10 to 13may be stored in a storage medium or distributed through a transmission path.

(2) The processing illustrated inFIGS. 7 and 10 to 13, and the like is described as a software-like processing using the program in the embodiment. However, some or all of the processing may be replaced with a hardware-like processing using an ASIC (Application Specific Integrated Circuit), a FPGA (field-programmable gate array) or the like.

(3) In the above-described embodiments, the detector2and the processor3are mounted on the measuring vehicle200(seeFIG. 1). However, the detector and the processor may be mounted on a hand cart (not illustrated) or the like to be carried by a user.

(4) In addition, in the above-described embodiments, the detection part34-k (where 1≤k≤N) outputs the cosine signal X, the sine signal Y, the amplitude signal R, and the phase difference signal θ. However, the values obtained by time-differentiating those signals may be output with the signals X, Y, R, and θ (or instead of the signals X, Y, R, and θ). In addition, the time-differentiated values may be displayed on the two-dimensional image130(seeFIG. 8C).

(5) In the fourth embodiment, the difference between the amplitude signal R and the cosine signal X is obtained. However, also in a case where the difference between “any one of the signals X and Y” and “anyone of the signals R and θ” is obtained, the effect caused by the vibration can be reduced, and the defective portion102can be detected similarly. For example, as illustrated inFIG. 17, the phase difference signal θ may be supplied to the gain adjustment part92, and the difference signal θ-X which is the difference between the cosine signal X and the phase difference signal θ may be output from the differential amplifier94.

REFERENCE SIGNS LIST