Patent Description:
It is a problem to facilitate satisfactory inspection methods and devices for collection of data for imaging of the material itself and of internal constructions, such as reinforcements, and or flaws and faults, for construction materials.

Solutions have been facilitated for inspection of installations such as pipelines, containers, railway tracks and the like to collect data and to map potential weaknesses and faults. Common for these are that the inspection tools are difficult to adapt in response to the wide variety of materials, surfaces and environments of the materials to be inspected.

It is further a problem with known solutions that the instruments are heavily dependent on using coupling fluid, either inside the instrument or both inside and outside between the instrument surface and the surface of the material to be tested. In these instances it is difficult to facilitate reliable measurements of a ground surface not offering an upward directed surface.

Problems arise also when large constructions are to be surveyed using ultrasonic signal emission and reception for imaging of the underground, since the available tools are more suitable for random sampling of small areas, or the tools are not customized for the task. The result is that the time consumption will be unacceptable high or near <NUM>% coverage, and analysis of the construction material is not achievable.

An even further problem is that unevenness in the surface of the material being tested will cause the instrument to loose contact with the surface of the material to be tested, and hence no valid measurements are being recorded.

<CIT>, <CIT>, <CIT>, and <CIT> disclose wheel probes filled with a coupling liquid.

<CIT> discloses an ultrasonic transmitting or receiving device comprises a ceramic disc transducer supported on an inner flat face of an aluminium hub. The hub is housed within a rim of polymethyl methacrylate, an intermediate oil film acting as a lubricant and acoustic coupling. In use, an air-filled or deformable plastics tyre is held in contact with the specimen.

The present invention provides a device for emission and reception of ultrasonic signal for analysis of large constructions of test material, including test material with uneven surfaces, and ultrasonic data collection. The present invention is flexible and customizable in that it can be adapted to the topology of the surface to be surveyed, amount of simultaneous data collection requirements, low maintenance and high coverage characteristics insensitive of surface structure.

The device is suitable for use analyzing the underground at various depths, the depth range also comprising the layer ranging from the surface and up to <NUM> - <NUM> into the test material, but not excluding other further buried layers. Depending on the requirements to S/N ratio of received data, frequency of transducer emitted signal and strength, rate of sampling, the depth range of the test material analysis can be varied substantially. The aim is to enable identification of weak spots and faults in the underground of the construction/test material, such as faulty or deteriorated reinforcements in a concrete construction, weak spots due to hidden branches or rotten parts in a wood construction, or other faulty parameters in such constructions or the likes. The present invention provides efficient collection of data using ultrasonic transducer technology, with the ability to utilize low frequency emission in the lower frequency ultrasound kHz range, preferably between <NUM> and <NUM>, or more preferably between <NUM> and <NUM>, for better performance in test material such as concrete and wood or the like.

The present invention may further be used for emission of ultrasonic signals in higher frequency ranges up to multi MHz range, preferably between <NUM>,<NUM> - <NUM>. The device may also be used for ultrasonic data collection from more compact test material, such as steel, carbon fiber, glass fiber or the like.

Although some frequency ranges have been specifically discussed in this document, this shall not limit the present invention, and other frequencies may easily be chosen.

The present invention is described in the appended claims. Claim <NUM> describes a device comprising two or more wheel assemblies comprising an inner backing/partial or complete orbital ring and an outer rotatable orbital ring, wherein the inner backing/orbital ring is non-rotating, the wheel assembly further comprising one or more ultrasonic transducers for emission and/or reception of reflected signal, the wheel assembly further comprising a low friction dry material embedded in at least one of the orbital outer ring or the partial or complete inner ring to decrease movement friction between the outer orbital ring and the partial or complete inner ring, the low friction dry material having an acoustic impedance as substantially the same as that of the orbital outer ring, where the one or more transducers are arranged on or integrated in the orbital inner ring.

Examples in the description that comprise a liquid / wet lubricant or low friction medium do not form part of the invention.

The wheel assembly provides in some embodiments connecting means for connecting more than one wheel assembly together in a wheel module mounted on a carriage, such as an instrument carriage.

One or more groups of connected wheel modules may be integrated in a larger group of wheel modules, wherein all transducers are controlled by a central controller, either mounted together with the larger group of wheel modules, or remotely connected via wired/wireless communication.

The wheel modules may be mounted on a custom adapted axle, or the connecting means may provide an axle function where the outer connection means of a wheel module, consisting of one or more wheel assemblies, on either side constitutes a connection point for the instrument carriage.

Each connection point, both between the wheel assemblies and between wheel module and instrument carriage may comprise electrical/signal connections via wire, slip ring contacts, wireless communication, induction contacts and other for transmission of control signals, power, survey data and similar.

The instrument carriage may comprise a motor function for moving the instrument carriage, by transferring a rotating force to one or more of the wheel modules or to a wheel assembly (not shown) dedicated for driving the carriage in a desired direction.

The invention is further explained in the attached figures that should be interpreted as illustrations of possible embodiments of the invention, but do not represent any limitation of the scope of the invention.

In a first embodiment as illustrated in <FIG> of the invention the wheel assembly comprises one transducer module <NUM>, the transducer module <NUM> comprising one or more transducers, with backing and shaft / axle <NUM> that will be stationary while an outer ring/ orbital outer ring <NUM> with a solid or viscoelastic coupling medium, such as an elastomer, is arranged radially outside the transducer module <NUM> with backing / orbital inner ring <NUM> and is rotating when the wheel assembly <NUM> is rolled along a surface under survey.

The transducers in the transducer module can be of any one of or combination of shapes such as: circular, square, concave, convex, single and double curved to achieve different transducer beam focus/defocus.

The one or more transducers <NUM> are completely or partially embedded in the orbital inner ring <NUM> such that the surface of the transducers <NUM> are in direct contact with the orbital inner ring <NUM>. The orbital inner ring is connected to the axle <NUM> in the sense that it is not rotating with the orbital outer ring <NUM> when the wheel assembly <NUM> is rolled along a test surface. The interface <NUM> between the inward facing surface <NUM> of the orbital outer ring <NUM> and/or the outward facing surface <NUM> of the orbital inner ring <NUM> comprises a low friction material or fluid <NUM> having an acoustic impedance in the same order as that of the orbital outer ring <NUM>. The low friction material <NUM>, <NUM> may be one of, but not limited to a polymer or polytetrafluoroethylene (PTFE), Graphite, hexagonal boron nitride, molybdenum disulfide, tungsten disulfide, metal alloys, PVDF or strongly hydrated brush polymers. The intention is to provide a dry interfaces providing a low friction bearing or contact. The wheel <NUM> will in most cases be used in a slow rolling speed action, and therefore the interfaces will not generate a lot of heat, or resistance against the rotational forces. The low friction material <NUM>, <NUM> may be attached to the inward facing surface <NUM> of the orbital outer ring <NUM> and/or the outward facing surface <NUM> of the orbital inner ring <NUM> as a separate layer material, or the layer material may be deposited by sputtering to the inward facing surface <NUM> of the orbital outer ring <NUM> and/or the outward facing surface <NUM> of the orbital inner ring <NUM>. Other known methods for production of the layering may be applied for achieving the same result.

Although not part of the claimed subject-matter, it is an option to use a wet interface, wherein either or both inward facing surface <NUM> and/or outward facing surface <NUM> has an applied film of a low friction fluid, or where the interface <NUM> between the inward facing surface <NUM> of the orbital outer ring <NUM> and/or the outward facing surface <NUM> is defined by a sealed off space <NUM> which is occupied by a low friction fluid which completely fills an enclosed space and provides a low friction bearing function. Such fluids may be selected from the low friction fluid like one of the following, but not limited to: silicon based fluid, mineral or vegetable based oil, synthetic oil, or water alone or in combination with one of the other base oils.

In a second embodiment as illustrated in <FIG> of the invention the wheel assembly <NUM>' comprises a backing <NUM>' where one or more transducers <NUM>' are mounted on the outward facing surface of the backing <NUM>' protruding radially from the backing <NUM>'. A stationary shaft part <NUM>' and a slip ring connector <NUM> (multifunctional) transmit signals and power to and from the transducers <NUM>'. A solid or viscoelastic coupling medium such as an elastomer layer/ orbital outer ring <NUM>' is arranged radially outside the transducer modules <NUM>' with backing <NUM>' and is rotating when the wheel <NUM>' assembly is rolled along a surface to be surveyed. In this embodiment the transduces <NUM>', the orbital inner ring <NUM>' and the orbital outer ring <NUM>' rotates together when the wheel <NUM>' <NUM> is rolled along a surface under survey. The orbital inner ring <NUM>' and/or the orbital outer ring <NUM>' may comprise one or more sensors (not shown) for detecting which part of the wheel assembly is in contact with the surface under test. The wheel may further comprise a controller (not shown) for controlling which transducer to activate, either as a transmitter or receiver or both. The controller may receive signals from the one or more sensors for detecting which part of the wheel assembly is in contact with the surface under test in order to activate only a limited number of transducers <NUM>' which are most optimal oriented towards the surface of the material under test. The sensors detecting which part of the wheel assembly is in contact with the surface under test may be gyro based, pressure based, radar based, sonar based, conductivity based or other.

In yet another embodiment of the wheel as described in <FIG>, the inward facing surface of the orbital inner ring <NUM>' may comprise a circular contact field for connection with an electrical brush connector/slip ring connector <NUM> to an electrical wiring being comprised in the axle. An alternative embodiment of the pattern of the circular contact field <NUM> is shown in <FIG>, wherein the pattern ensures that the slip ring connector <NUM> is in contact with only a portion of the transducers at the same time. Each transducer is in electrical contact with the circular contact field <NUM> at a point radially arranged in line with the transducer position on the orbital inner ring. A portion of the transducers may be a single transducer or more, adapted to how many transducers will be able to transmit and receive signals from the material under test. The use of a patterned circular contact field may simply be to save energy by not activating a number of transducers not able to contribute with meaningful information in the information collection process. Typically only transducers pointing towards the surface of the material under test will contribute to such information collection.

The orbital outer ring <NUM>, <NUM>' is typically configured to have acoustic impedance in the same order as that of the test material such that as little as possible of the out signal is lost when entering the material under test. If the acoustic impedance is too different, a lot of the signal energy will be lost when transmitting from the orbital outer ring <NUM>, <NUM>' and into the material under test.

The material of the orbital outer ring and/or orbital inner ring may further be configured with an elasticity coefficient adapted to the unevenness of the surface of the test material. The purpose of this is to enable, when more wheels are arranged on the same axle as illustrated in <FIG> and <FIG>, and an obstacle is encountered on the surface of the material under test, that only the wheels rolling over the unevenness will be affected of the unevenness. The elasticity of the orbital rings <NUM>, <NUM>', <NUM>, <NUM>' will adapt to the unevenness, and thereby only the actual wheel encountering unevenness will be affected when information is collected from the underground.

There are no limitations to the size parameters of the present invention. Any type of transducer may be used, and wheel sizes such as diameter and width is dictated by the required topography of the test material, the transducer types used for operating in the required frequency range, as well as required impedance in the material of the orbital rings.

A further mechanism for adapting to the unevenness of the surface of the material under test is provided in yet another embodiment of the invention wherein a suspension feature <NUM> is integrated in the wheel assembly. In <FIG> this is pictured in a wheel configuration as shown in <FIG>. Other integrated suspension mechanisms may be used. The independency of the suspension feature <NUM> adapted to the individual wheel <NUM>, <NUM>' provides a further improved characteristics for a system insensitive to obstacles in the path of the wheel modules. Letting the obstacle be avoided by a suspension device <NUM> instead of the more elastic material of the wheels as discussed above may improve the acoustic capabilities of the wheels. Even if one or more wheels may be disabled because of being lifted from the ground by an obstacle, the rest of the wheels being in contact with the surface of the material under test <NUM> will have an acceptable contact and signal response ratio. The latter suspension mechanism may be used to reduce limitation of material impedance compared with material under test as a result of a trade-off due to requirements to elasticity to enable testing rough test material.

The wheel assembly may be comprised of a partial inner ring <NUM> having a smaller diameter than the inner diameter of the outer ring <NUM>, <NUM> as described in <FIG>. The partial inner ring <NUM> may just be a fraction of a ring. The transducer <NUM> may be attached to the inside of the partial inner ring <NUM> or may be fully or partially embedded in the partial inner ring <NUM>. The smaller outer diameter of the partial inner ring <NUM> controls the area <NUM> of contact between the partial inner ring and the inside of the outer ring <NUM>, <NUM>.

Although they are not part of the claimed invention, there are alternative forms of the transducer(s) <NUM> and the coupling medium/ partial inner ring <NUM> than the fraction of an inner ring, for example a cylinder, spherical or coned form presenting a defined contact/coupling area between the coupling medium/ partial inner ring 52and the inside <NUM> of the outer ring <NUM>.

The shape of the orbital outer ring <NUM> may be provided in a form ideal for transmitting the acoustic signals from the transducers <NUM> to the material under test <NUM>, including but not limited to round, rectangle, coned, or pyramid shaped as illustrated in <FIG>.

The material, design and contact areas in the interfaces between the transducers <NUM> and the partial inner ring <NUM>, between the partial inner ring <NUM> and the inside of the outer ring <NUM>, <NUM>, and between the outer ring <NUM> and the material under test <NUM> defines the acoustic fields in the material under test <NUM> emitted from the transducers.

The coupling medium/ partial inner ring <NUM> and the outer ring <NUM>, <NUM> may be suspended in a similar way as discussed above, wherein the suspension feature <NUM> is coupled to the outer ring <NUM>, <NUM>, and the wheel assembly holds the transducer <NUM> and the coupling medium/the partial inner ring <NUM> at a constant radial position directed towards the material under test <NUM> whilst the outer ring <NUM>, <NUM> rotates as the wheel assembly is moved along the surface of the material under test <NUM>. Each wheel assembly of an instrument rig may be individually suspended, such that contact to the surface is maximized irrespective of unevenness in the surface of the material under test <NUM>.

The two contact areas, being comprised of the interface between the inside <NUM> of the outer ring and the outside of the coupling medium/outside of the partial inner ring <NUM>, and the outside of the outer ring <NUM> and the test material <NUM>, may present different acoustic properties varying with the area of the contact interfaces, the material of the outer ring <NUM> and the coupling medium/the partial inner ring <NUM>. Smaller contact areas give larger spread of the emitted signal from the transducer <NUM>. The requirement to acoustic spread may be governed by the state of the surface of the material under test <NUM>. A smooth surface of the test material <NUM>, may allow for wider contact area of the contact interfaces. <FIG> illustrates a coned form of the interface between the outer ring <NUM> and the material under test <NUM>.

The inside <NUM> of the outer ring and/or the outside of the coupling medium/outside of the partial inner ring <NUM> may comprise a lubricating formula, or be of a low friction dry material having required acoustic properties. Such material may for example be ROBALON®, or any type of polymer or polytetrafluoroethylene (PTFE), graphite, hexagonal boron nitride, molybdenum disulfide, tungsten disulfide, metal alloys, PVDF or strongly hydrated brush polymers, or others. The acoustic properties of the wheel assembly should be adapted to the composition of the test material <NUM>.

Using low friction dry materials in the interface <NUM> between the transducer <NUM>, the coupling medium/the partial inner ring <NUM> and the outer ring <NUM>, <NUM> enables adequate signal transmission through the wheel assembly into the material under test <NUM> without requiring any coupling fluid, and hence no need for advanced sealing features to hold the coupling fluid.

The construction of the test instruments can therefore be made much lighter and compact, with a simpler design that is easier to mount and dismount, and parts and materials of the wheel assembly and transducers may be altered to fit the material to be inspected <NUM> more readily.

A further example of a wheel assembly is shown in <FIG>. The transducers <NUM>' are mounted radially partially or completely embedded in a single orbital ring <NUM>, wherein the transducer outer surface represents the orbital outer ring as discussed in the above embodiments. The latter embodiment facilitates for a simpler implementation of production and adding the signal and electrical cabling <NUM> and contact pads <NUM>, and a slip ring contact <NUM>. The wheel may further be implemented without an axle and attached to a bearing wheel <NUM> via for example a ball bearing unit <NUM>. The bearing wheel <NUM> may further have connecting means <NUM>, such as bolt conduits for fastening to a chassis or a second wheel assembly.

In a further embodiment the wheel assembly may have recesses <NUM> for each transducer <NUM>', which completely "buries" the transducer <NUM>' into the single orbital ring <NUM>, The transducer comprising an outer "capsule" <NUM> having an endurable material with a known acoustic impedance and such present an even outer surface and constitute the orbital outer ring <NUM>'.

The transducers may have a physical form such that when mounted around the wheel assembly they will touch the neighbour transducer on both sides, and thus represent a continuous track.

A wide variety of survey tasks ranging from detecting corrosion areas on steel plates, pipes and structures, detecting cracks, flaws and detecting voids and delamination in composite materials, for example Carbone sheets or frames, or even woven fiberglass and glass reinforced plastic as used in light weight boat and airplane constructions. Often there is a need to test/survey a broader depth range than possible with traditional instrumenting. The present invention provides a solution to this in that the design of the wheel assemblies can be very flexibly arranged in modules of single wheel assembly to a multiple wheel assemblies arranged in an array mounted on an axle or on individual adapted frame connection arrangements. Such an embodiment is indicated in <FIG>, where wheel assemblies of the type discussed in <FIG> is individually arranged on corresponding ball bearing connectors <NUM> to a frame <NUM>, the wheels being arranged as three modules <NUM>, <NUM>, <NUM> having different wheel characteristics, and thus enabling a survey that can span several depth ranges simultaneously.

Typically, for controlling a welding seam <NUM>, present invention would be arranged with a number of wheel assemblies arranged perpendicularly on each side of the welding seam <NUM> as described in <FIG>, and rolled in a direction <NUM> along the path of the welding seam <NUM>. Depending on number of wheels and individual characteristic of the wheel assemblies it is possible to cover a wide depth range analysis.

The transducer design will also contribute to the total characteristic of the wheel assemblies. The higher the frequency and diameter of the transducers the narrower the beam angle is, and the more directional can the sound beam be controlled. In the opposite range, for wide beam requirements surveying the near surface area, it is desirable to operate with larger spread, hence lower diameter and lower frequency will achieve this.

Different wave guiding characteristics may also be used, such as shear waves and.

<FIG> illustrates how two arrays of wheel assemblies constituting two wheel modules arranged on two axles <NUM>, <NUM>' coupled to a frame element <NUM>.

One or more wheel assemblies <NUM>, <NUM>' of the invention described above may be mounted in a frame <NUM> as shown in <FIG>. <FIG> show how two wheel modules <NUM>, <NUM>', <NUM> are mounted in brackets/ frame <NUM>. The signaling cables <NUM> are lead through the frame <NUM>.

Another embodiment of the invention is illustrated in <FIG> showing three wheel modules <NUM>, <NUM>', <NUM> of the innovation mounted in a handheld frame <NUM>, where a handle <NUM> is mounted to the frame <NUM>. The handheld device of the invention may be operated to store received signals together with positional information calculated out from a predefined starting pint by registering the movement over the test material by the rolling motion of the wheels of the invention or other mechanisms such as for example a computer mouse device (not show) or infrared measuring means or the like (not shown).

The handheld device may have on board or attachable, via cable, induction or wireless communication access to: energy source, memory, control logic, input and output control ports, display and audio.

Indication lights <NUM> may be arranged on the frame for purposes such as indicating contact status between the device and the test material, alarm status if preset signal pattern is received, or if received signal in a specific position is not valid.

Indication lights may be color-coded, such as for example red light if no contact or green light when contact is detected between the device and test material. Other colors and switching pattern may be use for different purposes. One such purpose may be as a self-test indicator to be run prior to each job. It is also possible to use lights in a calibration routine where for example the device may be rolled over a known test material with a known surface with a known expected test result when transducers emit signals in line with a preset test pattern and frequencies. If expected received signal is verified the device is cleared for operation. Verified device may be identified by a preset light pattern displayed by the indication lights <NUM>.

A connected computer may also be used for purposes of storing, calibration, test and evaluation of test results. Computer may be connected by cable, wireless communication or by transfer of data via a storage memory device. A storage memory device may be detachably mounted to the electronic circuits in the device, or may be connectable via an interface at the time of transfer operation.

The array of transducers may be used in different modes. Two different modes are shown in <FIG>. Other modes can be utilized.

In <FIG>, it is shown a mode for along-track inspection. One array of transducers, e.g. the trailing wheel modules <NUM>, <NUM>', <NUM> of the invention, are used for emitting signals into the underground of the test material, and one array of transducers, e.g. the leading wheel modules <NUM>, <NUM>', <NUM> of the invention is used as receiving means for receiving the emitted signals that has traveled into and through the test material and reflected from this.

In <FIG>, it is shown a mode for cross-track inspection. This is achieved by allocating a number of transducers in one array of transducers for emitting the ultrasonic signal, and a number of transducers of the same array of transducers to receive the signal when reflected from the test material. One transducer may both emit and receive. In one scenario a transducer in the peripheral section of the array of transducers is emitting signals into the underground of the test material and one or more transducers in the mid-section of the array of transducers receives the reflected signals.

It is possible to use more than one array of transducers for receiving, i.e. for the handheld device described above: A transducer in the trailing array of transducers may emit, whilst the two leading arrays of transducers receive, or even all arrays of transducers may be set up to be receiving arrays of transducers were one or more arrays of transducers also emit.

One likely configuration in a system comprising <NUM> arrays of transducers/ wheel modules <NUM>, <NUM>', <NUM> such as in the handheld example above is to use the transducers in the middle array of transducers for emission of ultrasonic signals, and the two outer arrays of transducers/ wheel modules <NUM>, <NUM>', <NUM> for receiving the reflected signal from the test material.

It is also possible to use a single wheel modules <NUM>, <NUM>', <NUM><NUM> of the invention, utilizing the cross-track geometry described above.

Transducers may be used for emission or reception only, and both emission and reception, of ultrasonic signals and reflections. A transducer serving as both emitting and receiving transducer for the same ultrasonic signal, i.e. the transducer emit an ultrasonic signal and then wait for the reflections of the signal and then receive the reflected signal, will only receive and detect reflections from objects or the like or material in the path of the emitted signal. If the object is a small vertical crack below the transducer, the reflected signal may be very weak and difficult to detect. In the present invention will a set of transducers, where each transducer either emit or receive an ultrasonic signal, not only measure reflected signals, but also measure the signal transmitted through the test material, and thus be able to measure the lack of reflection, or for example the time-of-flight diffraction. These types of measurements will provide for better S/N ratio in the measurement data. Such configuration will be able to detect the omission of a reflected signal. For example if the signal is obstructed by an air pocket in the test material, and thus the signal propagation is severely obstructed, the receiving transducer will detect that the signal is not received as expected, and a conclusion may then indicate that there is a blocking medium between the emitting and receiving transducer, such as a crack, hole, non-relaying medium or other.

The above additional ability to detect omission of a reflection may be utilized by a single wheel transducer setup of the invention as explained for <FIG> above. Enhancing the analyzing effect further may be achieved with the present invention by combining the feature explained in <FIG> with the features of using more than one wheel module <NUM>, <NUM>', <NUM> as, one example of which is explained for the transducer setup in <FIG> above. In relation to cracks, obstructions and air pockets, the different transducer setups may be optimized further to detect along track oriented cracks, air pockets, obstructions, with the cross track inspection feature as explained for <FIG> above, or across track oriented cracks, air pockets, obstructions, with the along track inspection feature as explained for <FIG>.

In one embodiment of the invention, the invention may be used to find welding flaws, and delamination/air pockets in sandwich structures, such as used in ships or wings (planes, wind turbines). Such sandwich structures may be constructed of multiple layers of different materials. All with potentially different response features relative ultrasonic signals of specific frequencies. The present invention may be controlled in a manner to optimize the response at the specific depth of the test material where a specific sandwich layer interface is located. One could for example examine the interface between the innermost glass fiber layer and the core material in a <NUM> layer construction comprising an inner glass fiber layer, an outer glass fiber layer and a core polystyrene layer. Other materials and other number of layers may be used.

Another example of embodiment is to use the invention to detect detachments/air pockets under building tiles, such as in a bathroom floor, where the outer layer is ceramic, and the inner layer is of concrete or wood, possibly with a water tight membrane structure in between.

It is also possible to maximize detection capability by executing a regime of emission and reception of reflected signal where a more complex pattern of shifting the feature of each individual transducer dynamically as the ultrasonic data collection is performed. One pattern would be to let each transducer in turn act as the sole emitting source of a ultrasonic signal, and let all transducer of all wheels (if more than one) be receiving the emitted signal. This way it is possible to map the underground in many directions from perpendicular the motion direction to both sides of the emitting transducer. One example outlining one emitting transducer and <NUM> receiving transducers indicated by arrows <NUM> is indicated in <FIG>. Here three arrays <NUM>, <NUM>, <NUM> wheel modules <NUM>, <NUM>', <NUM> of transducers are used. All other combinations may be used from <NUM> emitting and <NUM> to <NUM> (<NUM> is not a limitation but the number used in the <FIG>) receiving. Other transducer combinations may be used.

One possible regime of pattern is to let all transducers in turn be the emitting transducer, and let all transducers act as receivers for all the reflections of an emitted signal. This way it is possible to map all test material from all angles, sideways, forwards, backwards, angled in all directions and directly below. Using the motion of the device of the invention as another parameter it is possible to make several such measurements when moving over the test material. For example an air pocket in the concrete would then be thoroughly exploited from many directions several times, and no "hidden" weaknesses will be omitted.

A different regime is to allocate one or more wheel modules as transmitting transducers, and other wheel modules as receiving transducers, and then activate several transmitting transducers simultaneously, and receive all reflected signals with the remaining transducers operating in receiving mode.

There are no limits to the size of the arrays of transducers or the wheels used.

The transducers may be selected for being used with multiple and variable frequencies.

Examples of execution regimes may include, but is not limited to, different beam-forming techniques. One example of an execution regime may be SAFT (Synthetic Aperture Focusing Technique).

The more detection data that is collected, the better S/N ratio will be possible to achieve in the analysis process when data is analyzed.

Analysis of the data received from the test material may provide for the compilation of detailed 2D and/or 3D images of the test material at various depths below the surface of the test material, typically <NUM> - <NUM> below the surface of the test material.

<FIG> show a system where three pairs of wheel modules <NUM>, <NUM>', <NUM> of the invention is combined to provide a system for inspection of large volumes of test material. Each pair of wheel modules <NUM>, <NUM>', <NUM> is mounted to an individual bracket <NUM>, and the three brackets are mounted to a carriage <NUM>. The carriage further comprises a computing/controlling means <NUM>, a laser measuring device <NUM>, and a display unit <NUM>. Each pair of wheels are individually adapting to the surface, as each section <NUM> of each wheel is individually adapting to the surface.

The device in <FIG>, or any variations of a device of the invention, may have on board or attachable, via cable, induction or wireless communication access to: energy source, data storage, control logic, input and output control ports, display and audio.

Indication lights as described for the handheld device above (not shown in <FIG>) may be comprised in this system as well as in all versions of embodiments of the invention, and for the same purposes as discussed above.

The carriage may comprise means for driving the carriage, e.g. an electromotor (not shown), remote controller features, and further comprise energy source or sources, handles <NUM> for manually pushing and/or steering the carriage and means for wireless communication with an external control unit (not shown).

The control unit may be preprogrammed to guide the carriage to cover all segments of the test material as illustrated in <FIG>. Here a real life representation show the carriage position <NUM>, the direction of movement <NUM>, and the areas that have <NUM>, <NUM>, <NUM>/ have not yet <NUM> been inspected. It may even be possible to distinguish between previous track of inspection <NUM>, current track of inspection <NUM>, and the overlap <NUM> of current track <NUM> of inspection relative to the previous <NUM> track of inspection.

By comparing the received data and the analysis result of this with the corresponding previously performed inspection, it is possible to detect changes in the underground of the test material. For example it may be possible to follow the deterioration of the reinforcement bar in a concrete bridge, and initiate corrective actions at an early stage of deterioration.

The laser unit may be used for measurement of distance in order to define the carriage position on the test material.

Another embodiment example is to use a device of the present invention to sample a painted steel construction. The present invention is able to collect samples of reflected ultrasonic signals that enable the data analysis to uncover cracks and defects in an unparalleled manner without the need to remove paint or other protection layer fixed to the surface of the steel construction.

Using the ability to compose an instrument having wheel modules <NUM>, <NUM>', <NUM> with different characteristics may detect flaws and irregularities on a much wider depth range on any material, or combination of material, wherein the different wheel modules <NUM>, <NUM>', <NUM> may be optimized for use on a specific lever of the test material, whether if that is a thickness measurement of a pipe, deterioration of a hull or tank, a bridge road armoring, a plane wing, radio mast bracket welding or other.

Although the examples given above is directed towards instruments used above ground, it shall be understood that the invention can be adapted to be used in sub-sea environments, wherein the instruments are mounted on for example an ROV to inspect sub s a installations, pipelines, and the like.

Claim 1:
Device for emission and reception of ultrasonic signal to and from a test material (<NUM>), the device comprising two or more wheel assemblies (<NUM>) attachable to an axle (<NUM>), wherein each wheel assembly (<NUM>) comprises:
an orbital outer ring (<NUM>) comprising an inward facing surface (<NUM>);
a solid or viscoelastic partial or complete inner ring (<NUM>, <NUM>) positioned within the orbital outer ring (<NUM>) so as to create an interface between the inward facing surface (<NUM>) of the orbital outer ring (<NUM>) and an outward facing surface (<NUM>) of the partial or complete inner ring (<NUM>, <NUM>), the partial or complete inner ring (<NUM>, <NUM>) being connectable to the axle (<NUM>) in a non-rotating manner and comprising an acoustic impedance in the substantially same order as that of the orbital outer ring (<NUM>);
one or more transducers (<NUM>) fixedly arranged partially or completely embedded in, or fixedly attached to the partial or complete inner ring (<NUM>, <NUM>); a low friction dry material embedded in at least one of the orbital outer ring or the partial or complete inner ring to decrease movement friction between the outer orbital ring and the partial or complete inner ring, the low friction dry material having an acoustic impedance as substantially the same as that of the orbital outer ring (<NUM>), wherein the one or more transducers may be oriented and maintained pointing towards the test material as the outer orbital ring rotates relative to the partial or complete inner ring when moved along the test material.