Patent Description:
Railroad inspection typically involves the use of ultrasonic sensors, electromagnetic magnetic sensors, vision sensors, or a combination there of.

The primary internal rail inspection methodology normally employs ultrasonic waves to inspect the majority of the internal structure of the rail and this sensor technology is typically deployed from the upper surface of the rail head <NUM> (<FIG>) using either ultrasonic probes <NUM> mounted inside fluid filled wheel probes <NUM> (<FIG>) or direct contact slider probes <NUM> (<FIG>). In the case of wheel probe deployment the ultrasonic transducers are typically mounted in pliable wheels <NUM> that ride over the upper surface of the rail head <NUM> (<FIG>). These wheels <NUM> are filled with a coupling fluid so that the transducers <NUM> mounted inside can send ultrasonic signals through the pliable wheel membrane and then into the rail using water as a coupling medium. The return signals are processed and used to map the locations of flaws in the rail.

While the prior art rail inspection method utilizes ultrasound, this can also be supplemented by the use of various other electromagnetic inspection techniques such as DC Induction or AC Eddy Current inspection systems and the sensors employed in these techniques again are normally applied for the top surface of the rail head, with the sensors being mounted in either slider or fluid filled wheel probes. Both of the electromagnetic inspection processors involve the injection of a current into the head of the rail, in the case of the DC Induction inspection system this involves the injection of a large direct current into the rail using two sets of contacts or brushes and in the case of the AC Eddy Current inspection system this involves coupling high frequency AC energy into the upper surface of the rail head. Discontinuities in the railhead section cause a disturbance of the current flowing through the railhead and these are detected by the sensors that are located on the rail head, with the a sensors head that responds to the accompanying magnetic field disturbance. Perturbations in the magnetic field around the railhead are detected as induced voltages in the electromagnetic sensors / search coils in the sensing head. The induced voltages produce signal currents that may be processed or displayed to an operator.

Common to all the above prior art inspection / sensing techniques is the desire to accurately / reliably maintain the lateral position the of the various sensors elements (ultrasonic and / or electromagnetic) over the top surface of rail. In the case of the ultrasonic sensors it is desired to maintain their lateral position to within +/- <NUM> mim of the ultrasonic center line of the rail.

Normally the sensors elements detailed above are mounted to a mobile rail inspection vehicle <NUM> (<FIG>) and these inspection vehicles are at times required to inspect rail at speeds in excess of <NUM>/h (<NUM> mph). Typically to provide some method of guiding the inspection sensors reliably over the top of the rail head <NUM>, the sensors are typically mounted from either an adapted bogie <NUM> (<FIG>), a under vehicle supported test carriage (<FIG>) or a gauging axle <NUM> (<FIG>). However, in most cases the mechanical guidance, such as a lateral compensation system <NUM> provided is not enough to maintain the required lateral accuracy of +/- <NUM> for the ultrasonic probes to be able to maintain the ultrasonic center line of rail (<FIG>). This issue is further compounded when the effects of rail head <NUM> wear (<FIG>) are taken into consideration in very tight curves (><NUM> radius).

One issue that arises with the use of ultrasonic transducers occurs on curved sections of the rail. It has been found that the top surface of curved rail sections wear in a manner that causes the ultrasonic beam <NUM> to be refracted away from the rail center line as shown in <FIG>. For rails with a curvature less than <NUM> meters, the refraction of the ultrasonic beam <NUM> may be significant enough in some instances to cause the return signal to miss the zero-degree ultrasonic probe. This issue become worse as the radius decreases. To address this issue, existing inspection systems may include lateral compensation assemblies <NUM> (<FIG>) include a manual control that allows the operator to shift the position of the ultrasonic probe to allow measurement of the return signal.

<CIT> discloses a track inspection vehicle and a method for automatically inspecting rails. The inspection vehicle is provided with ultrasonic proximity sensors suitable for detecting obstacles ahead of the vehicle itself. The vehicle is further provided with a track geometry measurement system which can be provided inter alia with ultrasound sensors. The track geometry measurement system can also provide curvature information to the vehicle control system can direct the proximity management system to direct its sensors into a curve, where by increasing the usable range of the sensor assembly.

<CIT>discloses a carriage for ultrasonic rail testing. This prior art document briefly suggests that mechanical means for measuring track curvature would be employed to provide the necessary control intelligence of the lateral pivotal movement -that is a swing movement in a horizontal plane- of the connecting bar <NUM> and holder <NUM> in a horizontal plane. The piezo-electric acoustic transducers used as ultrasound sensors are secured to the holder <NUM>. <CIT> discloses a third example of a rail fault detection device provided with ultrasonic detectors but lacking a curvature detection system.

Accordingly, while existing rail inspection systems are suitable for their intended purpose the need for improvement remains, particularly in providing a system and method of inspecting rails without requiring operator manual intervention.

According to one aspect of the disclosure, a system for inspecting a rail is provided having the features according to claim <NUM>.

According to another aspect of the disclosure a method of inspecting a rail is provided having the features according to claim <NUM>.

Embodiments of the present invention are directed to a system and method for inspecting rails, such as those used with railroad tracks. Embodiments of the present invention provide advantages in allowing for a compensation of sensors on curved sections of a rail. Further embodiments of the present invention provide advantages in automatically determining the radius of a curved rail and compensating the position of the sensor to allow inspection measurements of the rail independent of speed of a carriage to which the sensor is mounted.

Referring now to <FIG>, a rail inspection system <NUM> is shown having a bogie / test carriage <NUM> that has been adapted to mount various ultrasonic <NUM> and electromagnetic sensors <NUM> that are used to inspect the railroad rails as the vehicle transits over them. It should be appreciated that while the illustrated embodiment bogie <NUM> is mounted under a railway instrument vehicle <NUM> coupled to a railway power vehicle <NUM> as a semi-automatic rail bound test carriage, this is for exemplary purposes and the claims should not be so limited. In other embodiments, the carriage may include a propulsion system (e.g. an engine) and may be operated by a human operator, autonomously operated, remotely operated or a combination of the foregoing. In still further embodiments, the bogie / test carriage <NUM> may be moved or towed by a separate vehicle having its own propulsion system. In an embodiment, the system <NUM> can include both ultrasonic detector systems <NUM> and electro-magnetic (Induction and Eddy Current) detector system <NUM>, the system may equally employ only the ultrasonic measurement sensors <NUM>. All the sensors whether ultrasonic or electro-magnetic are in direct contract with uppers surface of the rail head <NUM> of rail <NUM> (<FIG>).

Referring now to <FIG> and <FIG>, the bogie / test carriage <NUM> further includes an ultrasonic sensor system that includes one or more roller search units (RSUs) <NUM>. Each RSU <NUM> includes a fluid-filled wheel <NUM> formed of a compliant material <NUM> that deforms to establish a contact surface when the wheel <NUM> is in contact with and pressed against the rail <NUM>. The fluid filled wheel <NUM> is mounted on an axle <NUM> attached to the RSU frame so that the fluid filled wheel <NUM> contacts the rail <NUM> as the bogie / carriage <NUM> passes over or is pulled along the rail track. The RSU <NUM> may include many ultrasonic individual ultrasonic probes or transducers <NUM> and includes at least one zero degree ultrasonic transducer <NUM> mounted inside the fluid filled wheel <NUM>. The zero degree ultrasonic transducer <NUM> is configured and positioned for transmitting ultrasonic beams through the fluid in the wheel <NUM> and through the contact surface <NUM> of rail head <NUM> into the rail <NUM> and for receiving a reflected or return beam from the rail <NUM>. The transducers <NUM> generate return signals that are transmitted to a data processing system <NUM> (<FIG>).

Referring now to <FIG>, the signals from Linear Velocity Displacement Transducer (LVDT) <NUM> and Laser <NUM> rail position sensors are used to establish the normal center line of the rail <NUM> and these are processed without the any influence of a curvature sensor <NUM> while the radius of the curve is greater than <NUM> (<NUM> mile).

In an embodiment, the laser system <NUM> is an optical sensor that measures a distance to a location on the rail <NUM> using a laser or other light source. A portion of the laser light is reflected back and received by a photosensitive sensor, such as a photodiode for example. Based on this measured distance, a position of the ultrasonic transducer <NUM> relative to the center of the rail <NUM> may be estimated. It should be appreciated that while embodiments herein refer to the laser guidance system.

If the curvature sensor <NUM> output signal <NUM> indicates that the curve radius is less <NUM> (<NUM> mile), then the output signal <NUM> is used by a servo controller <NUM> to progressively offset the nominal center position of the wheel <NUM> that has been determined or measured by either the Linear Velocity Displacement Transducer (LVDT) Sensor <NUM>, laser <NUM> or other rail center line measurement sensors (e.g. optical measurements of the rail <NUM>). It should be appreciated that dependent on the direction of the curve and individual rails the corrective action applied to the lateral movement will differ. For example, when the rail <NUM> is a left hand curve, the left hand side rails guidance system will be offset towards the gauge side of the rail <NUM> and the right hand side rail will be offset to the field side of the rail <NUM> (<FIG>), conversely for a right hand curve the left hand side rail will be offset to the field side of the rail and the right hand side rail to the gauge side of the rail. In the exemplary embodiment, these lateral corrections of the position of the wheel <NUM> and the electro mechanical servo assembly <NUM>, <NUM> and <NUM> are automatically completed by the servo controller.

Referring now to <FIG>, a schematic embodiment is shown of the ultrasonic inspection sensor system <NUM>. This system includes the ultrasonic roller search unit (RSU) sensors <NUM> that is made up from a plurality of fluid-filled wheels <NUM> that are mounted to the side frames <NUM>.

Referring now to <FIG>, in an embodiment attached to each of the bogie / carriage side frames (left / right side) is a servo control system <NUM> which all the RSU sensors <NUM> on each side of the bogie / carriage <NUM> are suspended. In other words, there is an RSU sensor <NUM> and a servo control system <NUM> associated with each rail <NUM> of the railway being inspected. The each of the servo control systems <NUM> are configured to independently guide the respective left hand and right hand RSU sensor <NUM> down the center line of the rail <NUM>. The servo control system laterally adjusts position the RSU sensor <NUM> so that it to moves across the head of the rail <NUM> in the directions indicated by arrow <NUM>. It should be appreciated that the two independent servo control systems <NUM> may be coupled or linked via the curvature sensor <NUM>. It should also be appreciated that when the bogie / carriage <NUM> is located on a straight section of rail track, the direction <NUM> may be substantially perpendicular to the track and the direction of motion. In other words, with further reference to <FIG>, <FIG> and <FIG>, the direction of the bogie / carriage <NUM> is substantially perpendicular to a longitudinal axis <NUM> of the carriage <NUM> or parallel with the axis <NUM> of the wheels <NUM>. In an embodiment, the RSU <NUM> includes ultrasonic transducers <NUM> that are disposed within a fluid filled wheel or tire <NUM> (<FIG>). Within each RSU <NUM>, the plurality of transducers <NUM> include at least one of zero-degree transducer <NUM>.

The ultrasonic signals emitted from the plurality of transducers <NUM> within the RSU <NUM> are coupled into the rail <NUM> using a water that is sprayed on to the upper surface <NUM> of the rail head <NUM>. The signal / beam path for the plurality of the transducers <NUM> is shown diagrammatically as beams in the rail side / end views of <FIG>. To ensure the RSU's <NUM> are tracking the rail center line the system <NUM> (<FIG>) has an integrated signal monitoring system that continually tracks the ultrasonic signal received back from the rail base <NUM> (<FIG>) of the zero degree transducer <NUM>. In the event that this signal is lost either due to poor RSU <NUM> tracking along the rail <NUM> or due to the lack of effective ultrasonic coupling of the zero degree transducer <NUM> into the rail <NUM>, the system <NUM> will then determine and record this as a section of untested rail.

Referring to <FIG>, in an embodiment each rail <NUM> (left and right) has its own individual servo control system <NUM>. To ensure that each set / side of RSU <NUM> follow the center line of the rail <NUM> one of two or more rail positioning sensors are deployed, such as Laser sensor <NUM> or the Linear Velocity Displacement Transducer (LVDT) sensor <NUM>, or as combination thereof, also other rail position sensors / systems may also be used such as rail profile measurement system or a mechanical gauging test carriage or axle etc. All of these sensor or measurement systems are configured to provide that the RSU <NUM> are guided down the center line of the rail <NUM> and maintain a reliable rail base indication from the zero degree transducer <NUM>. In an embodiment, all the electronic rail center line measurement systems are configured to generate an error signal <NUM> in event that the bogie / test carriage mechanics moves the RSU <NUM> away from the center line of the rail or the position of the rail <NUM> relative to the RSU <NUM> changes due to a change in the distance between the right and left rails as the vehicle <NUM> (<FIG>) progresses along the track. The error signal <NUM> generated in response to movement away of the RSU <NUM> from the center of the rail, is then processed by the servo controller <NUM> and used to provide drive signals that cause the servo actuator <NUM> mechanically (linearly) translate or move a frame <NUM> to which the RSUs <NUM> are mounted from in order to reduce the rail position sensor error signal and therefore re-align the RSUs <NUM> with the Rail Center Line (<FIG>). In an embodiment, manual joysticks <NUM> are provided to allow the operator to manually offset the RSUs <NUM> to offset from the nominal rail center position and to accommodate heavily side worn rail conditions <NUM> (<FIG>).

It has been found that when a generic ultrasonic mobile inspection vehicle (<FIG> or <FIG>) equipped with either a bogie (<FIG>) or test carriage <NUM> or <NUM> (<FIG>) or gauging axle (<FIG>) are used to provide ultrasonic probe deployment system, whether the probe guidance / tracking system is electrical or mechanical, an ultrasonic performance issue is often experienced when inspecting curves with a radius that is typically greater than <NUM>. This performance issue is related to not being able to maintain a reliable return signal using the zero degree transducer <NUM>. As a result, these systems report that the rail in question as untestable. It is has been discovered that this lack of performance cannot be directly attributed to the RSU <NUM> tracking or the dynamic response of the control system, rather it has now been found that the untestable rail situation is due to the zero degree transducer <NUM> beam <NUM> being refracted away from the center line of the rail (<FIG>), this refraction then causes a reduction in the amplitude of the return zero degree transducer signal and hence the system reports the situation as untested rail. The wear that occurs in this situation normally occurs on both rails in either right hand or left hand curves and is shown in <FIG>. As shown in <FIG>, the rail <NUM> and rail <NUM> are on the left hand side of the vehicle and as shown in <FIG>, the rail <NUM> and rail <NUM> are on the right side of the vehicle. As shown in <FIG> it has been discovered that the rail head wear pattern <NUM> for a right hand curve <NUM> (<FIG>) will cause the zero degree transducer's beam <NUM> on the left hand rail <NUM> to be refracted away from the rail center towards the gauge side <NUM> of the rail and towards the field side <NUM> of the right hand rail. Conversely it has been discovered that the rail head wear pattern <NUM> for a left hand curve (<FIG>) will cause the zero degree transducer's beam <NUM> on the left hand rail <NUM> (<FIG>) to be refracted away from the rail center towards the field side <NUM> and towards the gauge side of the right hand rail <NUM>.

It is known the effects of rail head wear in curves on the refraction of the zero degree transducer beam <NUM> can be manually compensated for by either laterally offsetting in a direction indicated by arrow <NUM> or arrow <NUM> (<FIG>) or adjusting the cant-angle-offset <NUM> or cant-angle-offset <NUM> (<FIG>) the RSU <NUM> in the desired direction using the servo control system <NUM> (<FIG>) manual joystick controls <NUM>. The effect of making these adjustments is shown in <FIG> and it should be appreciated that this would then significantly reduce the amount of reported untestable rail caused by the loss of the reflected signals <NUM> from the zero degree probe. However, the main drawback of this manual offset process is that the vehicle operators can only manually compensate for the issue once it has been detected and the same adjustment but in the opposite direction will be required once the vehicle has exited the curve.

With the ultrasonic rail inspection speeds being up to <NUM>/h (<NUM> mph) it can be appreciated that if it takes even a few seconds for the manual adjustment process to be completed many meters of track may be reported as untested. It should be appreciated that embodiments of the present invention provide advantages in of automatically making the tracking adjustments to compensate for the curved track rail head profile wear without the need for any manual operator intervention.

Another desirable feature of a curvature guidance compensation system is for it to provide the required correction in various weather conditions that are experienced throughout the world. This includes rain, snow, sand, wind and many other less specific conditions. Embodiments of the present invention provide advantages in being able to measure the track curvature when only the top surface of the rail head is exposed (e.g. high grass/weeds, deep snow, high ballast, or testing through rail road / level crossings).

In some embodiments, the servo control system <NUM> may further include one or more additional measurement curve sensor's, that either directly or indirectly measure the curvature of the rail track.

Referring now to <FIG>, a system <NUM> is shown that addresses issues related to providing automatic RSU <NUM> positional correction to compensate for the ultrasonic effects of rail head wear in railway curves. The system 41provides an indication of the components used to control the position of the RSU <NUM> on both sides of the vehicle (Left and Right Rails <NUM>). In an embodiment, the system <NUM> uses a curvature sensor <NUM> and in cooperation with guidance application software that resides memory <NUM> in each of left and right servo controllers <NUM> and is executed on the respective processor <NUM> in each of the individual servo controllers <NUM>.

In an embodiment, the curve sensor <NUM> is mounted centrally on the test carriage cross beam <NUM> (<FIG>, <FIG>) and this is used to measure either directly or indirectly, the radius of curvature of the railway track <NUM> by the implied angle of inclination <NUM> (<FIG>) that is measured by the curvature sensor <NUM>. The curvature sensor <NUM> may include be based on an electro-mechanical or optical sensor technology or a combination of the foregoing. The curvature sensor <NUM> measures an angle <NUM> that the carriage <NUM> (<FIG>) is resting or traveling relative to a horizontal plane (e.g. a plane perpendicular to the direction of gravity). In other words, when the railroad track bed is angled, or banked, the curvature sensor <NUM> will measure the angle based on the angle or tilt of the carriage <NUM>. The curvature sensor may be any suitable angle measuring device, such as a single axis curvature sensor <NUM> for example that measures angles up to +/- <NUM> degrees.

As shown in <FIG>, the curvature sensor <NUM> output angular inclination measurement signal <NUM> is feed into both the left and right servo controllers <NUM>. This signal is then processed by the servo controllers <NUM> in accordance with a method <NUM> shown in <FIG>, which modifies the rail tracking error signals 46A, 46B, from either the Linear Velocity Displacement Transducer (LVDT) sensor <NUM> or the Laser rail tracking sensor <NUM>.

Referring now to <FIG> show how the required RSU tracking is automatically modified based on the output of the curvature sensor <NUM> and the left and right servo controllers <NUM> pre / post the correction process for a left hand curve with rail head wear. In this embodiment, the carriage <NUM> is tilted at an angle Θ such that the left rail 30A is lower than then right rail 30B. <FIG> shows the impact of the rail head wear prior to any offset correction process. <FIG> shows how the correction process can be applied by laterally offsetting in the direction of arrow <NUM> the RSU's <NUM> and <FIG> shows how the correction process can be applied by changing the cant angle indicated by arrow <NUM> the RSU's <NUM>.

The control error signal 46A, 46B may be based on measurements performed by the Linear Velocity Displacement Transducer (LVDT) sensor <NUM> or the Laser tracking sensor <NUM>, or a combination of the foregoing. The control error signals 46A, 46B are transmitted to a servo controller <NUM> that actuates and controls the position of an actuator <NUM>. In the exemplary embodiment, the actuator <NUM> is a linear actuator configured to move in a lateral direction, such as a direction indicated by arrow <NUM> for example but could also be applied in a similar method by adjusting the cant angle with a rotational movement of the RSU <NUM> as indicated by arrow <NUM>.

The servo controller <NUM> is a suitable electronic device capable of accepting data and instructions, executing the instructions to process the data, and presenting the results. Servo controller <NUM> may accept instructions through user interface, or through other means such as but not limited to electronic data card, voice activation means, manually-operable selection and control means, radiated wavelength and electronic or electrical transfer. Servo controller <NUM> includes a processor <NUM> coupled to memory <NUM>, such as a random access memory (RAM) device, a non-volatile memory (NVM) device, a read-only memory (ROM) device, one or more input/output (I/O) controllers, and in some embodiments a local area network (LAN) interface device.

The Servo controller <NUM> is capable of converting the analog voltage or current level provided by ultrasonic detector assembly <NUM>, curvature sensor <NUM> and laser rail tracking sensor <NUM> into a digital signal indicative of the quality or strength of the return signal to the ultrasonic transducer <NUM>. The servo controller <NUM> uses the digital signals act as input to various processes for controlling the ultrasonic sensor system.

In general, the servo controller <NUM> accepts data from the Linear Velocity Displacement Transducer (LVDT) sensor <NUM>, the curvature sensor <NUM>, and the laser rail tracking sensor <NUM>. The servo controller <NUM> is given certain instructions for the purpose of comparing the data from sensors <NUM>, <NUM>, <NUM> to predetermined operational parameters. The servo controller <NUM> provides operating signals to actuator <NUM> to change the lateral position or cant angle position of the side frame <NUM> and thus the position of the RSU <NUM> and the ultrasonic transducer <NUM> relative to the rail <NUM>. In an embodiment, the servo controller <NUM> compares the operational parameters to predetermined variances (e.g. voltage greater than or less than a predetermined value) and if the predetermined variance is exceeded, generates a signal that may be used to indicate an alarm to an operator or a computer network.

In an embodiment the servo controller <NUM> receives a signal from the curvature sensor <NUM> that measures the angle of a cross-frame member <NUM>. In an embodiment, the cross-frame member <NUM> is parallel with the direction <NUM> (<FIG>). As a result, the curvature sensor measures angle, tilt or banking of the ground that the rails <NUM> are placed (e.g. angle measured relative to a horizontal plane). It has been found that the radius of curvature of the rail may be estimated based on the angle or tilt of the surface on which the rails are placed. Thus, based on historical data of surface angle vs rail radius of curvature, the servo controller <NUM> may estimate the rail curvature based on the angle measured by the curvature sensor <NUM>.

Referring now to <FIG>, with continuing reference to <FIG>, <FIG>, <FIG> and <FIG>, a method <NUM> is shown for inspecting the rails <NUM>. The method <NUM> begins in block <NUM> where the inspection is started. This may include mounting the system <NUM> (<FIG>) on the railroad track and either coupling the carriage <NUM> to a propulsion source, or initiating a propulsion source of the system <NUM>. The method <NUM> then proceeds to block <NUM> where the angle of the curvature sensor <NUM> is measured relative to a horizontal plane. In an embodiment, a look-up table, a database, a model or other relationship of actual curvature angles and the corresponding inclinometer measurements that were measured while the vehicle passes over curves of known radius's is provided. The method <NUM> then proceeds to block <NUM> where the radius of the rail <NUM> is determined (e.g. via the look-up table). In an embodiment, the radius of the rail is correlated with a signal output (voltage) from the curvature sensor <NUM>.

The method <NUM> then proceeds to query block <NUM> where it is determined whether the radius is less than a predetermined threshold, such as <NUM> meters for example. When the query block <NUM> returns a negative (e.g. radius equal to or greater than <NUM> meters), the method <NUM> loops back to block <NUM> and the process continues. When the query block <NUM> returns a positive (e.g. radius less than <NUM> meters), the method <NUM> proceeds to block <NUM> where lateral offset compensation is applied.

As discussed herein, a technical effect of the offset compensation is to move the position of the RSU <NUM> to improve the reflection of the ultrasonic signal back to the zero-degree transducer to reduce the errors, sometimes referred to as Lack of Expected Response (LER) during the inspection without having manual intervention by the operator. Is should be appreciated that this compensation may be performed and provide advantages in improving the inspection rails independent of the speed of the carriage <NUM>.

In still a further embodiment, the offset compensation is a function of both the curvature sensor <NUM> and the laser rail tracking sensor <NUM>.

In still a further embodiment, the offset compensation is a function of both the curvature sensor <NUM> and the Linear Velocity Displacement Transducer (LVDT) sensor <NUM>.

Technical effects and benefits of some embodiments include providing a system for inspecting a rail, such as that used in railroads, for undesired conditions using an ultrasonic signal. Further technical effects and benefits include the automatic adjustment of the position of an ultrasonic transducer during the inspection based on the curvature of the rail reduce or eliminate the reflection of the ultrasonic signal away from the transducer due to rail wear or deformation.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The term "connected" means a direct connection between the items connected, without any intermediate devices. The term "coupled" means either a direct connection between the items connected, or an indirect connection through one or more passive or active intermediary devices. The term "circuit" means either a single component or a multiplicity of components, either active and/or passive, that are coupled together to provide or perform a desired function. The term "signal" means at least one current, voltage, or data signal. The term "module" means a circuit (whether integrated or otherwise), a group of such circuits, a processor(s), a processor(s) implementing software, or a combination of a circuit (whether integrated or otherwise), a group of such circuits, a processor(s) and/or a processor(s) implementing software.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as arc suited to the particular use contemplated.

Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages.

Claim 1:
A system for inspecting a rail (<NUM>), the system comprising:
an ultrasonic transducer (<NUM>, <NUM>) positioned to emit an ultrasonic beam (<NUM>) onto the rail (<NUM>) and receive a refraction beam (<NUM>), the ultrasonic transducer (<NUM>, <NUM>) being movable between a first position and a second position;
a curvature sensor (<NUM>) operable to measure a change in angle of a carriage (<NUM>) relative to a horizontal plane and determine a radius of the rail (<NUM>) in response to the measured change in angle of the carriage(<NUM>) relative to a horizontal plane; and
a controller (<NUM>) operably coupled to the curvature sensor, the controller (<NUM>) having a processor that is responsive to executable computer instructions when executed on the processor to cause the ultrasonic transducer (<NUM>, <NUM>) to move to receive refraction beam in response to a determination that the radius of curvature of the rail (<NUM>) is less than a predetermined first threshold.