FIELD This invention relates to the field of non-destructive testing using a climbing robot. More particularly this invention relates to the detection and characterisation of defects on and around composite or at least partly composite materials, and a metal material such as aluminium or an aluminium alloy, used in aircraft fuselages and/or parts. BACKGROUND

Owners and/or operators of aircraft perform routine maintenance in order to check that the surfaces and structures of their aircraft are free from defects which could compromise the safety of the vessel when in flight, such as fine surface breaking cracks for example. Even very small surface cracks or defects, which may be almost invisible to the naked eye, can cause failure of parts and lead to issues once in flight.

Composite materials are becoming more widespread in the aviation industry, particularly in aircraft fuselages, and other parts such as rudders, elevators, flaps and spoilers. Defects in these composite materials may not immediately be visible to the human eye, for example due to the layered nature of composites, delamination can occur, and due to the hollow, honeycomb nature of the internal composite structure water ingress can occur. Although composite and partly composite aircraft parts are considered stronger than those made of more traditional materials, this increased strength is directional - they can be weaker under loading from different directions or in different circumstances, for example when walked on by a person. This can mean traditional methods for inspecting these materials that require walking on the parts are no longer suitable. Therefore, more advanced techniques are required to inspect composite or part composite aircraft parts for defects. Existing techniques for identification of defects in traditional materials include naked eye and assisted visual methods, ultrasonic, and eddy current devices. Such devices usually probe the structure normal to its surface, and are used manually. Manual inspection for cracks or defects is challenging and time consuming, and expensive due to the need for instance to take a large number of readings at set intervals for instance. Existing techniques for identification of defects in composite materials include thermographic imaging, ultrasonic thickness testing, and eddy current testing. Thermal imaging, alternatively known as thermography or infrared thermography works by applying heat to a portion of the surface of an area of a material being tested and then acquiring a thermal image of the sample surface as the heat dissipates into the material using an infrared camera . Flaws within the material, including those not easily visible to the human eye can be detected using thermal imaging. Defects such as for example water ingress and delamination will result in a different rate of heat dissipation than in a defect free structure, which can be picked up by the infrared camera.

Ultrasonic testing involves timing the propagation of ultrasonic waves directed through a material. It requires an ultrasonic transducer or transmitter and a receiver. A transmitter can emit waves through a material towards a receiver or alternatively a transducer performs both the transmitting and receiving when the wave is intended to be reflected . The thickness of the material and the presence of cracks, delamination, voids, inclusions etc. can be determined by comparing the real propagation time with the expected propagation time based on type and thickness of material, angles of incidence and distance between transducers. Currently, inspection using for example thermal imaging is manual and involves at least two highly trained people using handheld equipment to inspect a part stage by stage, usually an area of about 50mm square each time. This can be a very time consuming process and often requires parts to be removed from their in use position on the aircraft to be tested. Similarly, other non-destructive inspection techniques require highly trained persons using scanning equipment and are time consuming.

It is an object of at least some embodiments of the invention to provide improved or at least alternative equipment for non-destructive inspection of an aircraft body. SUMMARY OF INVENTION

In a first broad aspect the invention consists a robot for non-destructive inspection of an aircraft body comprising a chassis configured to carry non-destructive inspection equipment, and a passive adhesion mechanism adapted to provide a passive adhesion force between the robot and the aircraft body. Preferably the passive adhesion mechanism comprises one or more suction pads adapted to retain a passive adhesion force between the robot and the aircraft body during movement. In at least some embodiments the passive adhesion mechanism further comprises an actuator or actuators adapted to cause movement of one or more suction pads toward and away from the aircraft body.

Preferably the chassis comprises one or more wheels, rollers, or tracks adapted to contact the aircraft body. Preferably the chassis further comprises a motor adapted to drive one or more wheels, rollers, or tracks when energised, to move the chassis on the aircraft body.

In at least some embodiments the non-destructive inspection equipment is arranged such that it enables the robot to perform continuous identification of defects on the aircraft body. The aircraft body may comprise a material that is at least in part composite, or alternatively the aircraft body may comprise a metal material such as typically aluminium or an aluminium alloy.

In some embodiments the non-destructive inspection equipment is integrally or

permanently mounted to the chassis or a housing of the chassis. In other embodiments the non-destructive inspection equipment is releasably mounted to the chassis.

In some embodiments the non-destructive inspection equipment comprises equipment adapted to enable the robot to perform thermal imaging of the aircraft body. Preferably the non-destructive inspection equipment comprises a thermal source and an infrared camera.

In some embodiments the non-destructive inspection equipment comprises equipment adapted to enable the robot to perform ultrasonic inspection of the aircraft body. Preferably the non-destructive inspection equipment comprises at least one ultrasonic transducer, or at least one transmitter and at least one receiver.

In some embodiments the non-destructive inspection equipment comprises equipment adapted to enable the robot to perform eddy current inspection of the aircraft body.

Preferably the non-destructive inspection equipment comprises at least one eddy current probe. In some embodiments the non-destructive inspection equipment comprises equipment adapted to enable the robot to perform visual inspection of the aircraft body. Preferably the non-destructive inspection equipment comprises at least one visual imaging camera. In some embodiments the non-destructive inspection equipment is adapted to enable the robot to perform thermal imaging of the aircraft body, and is further adapted to perform at least one of ultrasonic inspection, eddy current inspection, or visual inspection.

In at least some embodiments the non-destructive inspection equipment is mounted to the robot using an actuating carriage. Preferably the actuating carriage is removable from the robot.

In a second broad aspect the invention consists a method for non-destructive inspection of an aircraft body using a robot comprising positioning non-destructive inspection equipment on the robot, adhering the robot to the aircraft body using a passive adhesion mechanism adapted to provide a passive adhesion force between the robot and the aircraft body, moving the robot on the aircraft body, and performing non-destructive inspection of the aircraft body using said non-destructive inspection equipment. The method may further comprise continually moving the robot as it performs nondestructive inspection of the aircraft body. The method may further comprise performing non-destructive inspection of the aircraft body and detecting defects in the aircraft body in real-time. The non-destructive inspection equipment may comprise equipment adapted to enable the robot to perform thermal imaging of the aircraft body.

The method may further comprise positioning an infrared camera on the robot at a known distance from the aircraft body, positioning a thermal source over an area of the aircraft body, applying heat from the thermal source onto the area of the aircraft body changing the temperature of the area of the aircraft body, and collecting infrared images from the area of the aircraft body using the infrared camera . The method may further comprise identifying defects in the aircraft body using the infrared images. The method may further comprise positioning the infrared camera rearward of the position of the thermal source. The non-destructive inspection equipment may comprise equipment adapted to enable the robot to perform ultrasonic inspection of the aircraft body. The non-destructive inspection equipment may comprise at least one ultrasonic transducer, or at least one transmitter and at least one receiver.

The non-destructive inspection equipment may comprise equipment adapted to enable the robot to perform eddy current inspection of the aircraft body. The non-destructive inspection equipment may comprise at least one eddy current probe, or at least one array of eddy current probes.

The non-destructive inspection equipment may comprise equipment adapted to enable the robot to perform visual inspection of the aircraft body. The non-destructive inspection equipment may comprise at least one visual imaging camera . The non-destructive inspection equipment may comprise equipment adapted to enable the robot to perform thermal imaging of the aircraft body, and further adapted to perform at least one of ultrasonic inspection, eddy current inspection, or visual inspection.

In this specification :

· 'passive adhesion' or 'passive suction' means, unless otherwise stated, adhesion or suction created by a vacuum-based adhesion mechanism in which power is required to generate or release relative vacuum between a cup or similar contacting a surface, but not to maintain it, and passive adhesion system has a corresponding meaning .

· 'defects' includes, unless otherwise stated cracks, cuts, corrosion, disbanding, dents, delamination, water ingress/intrusion, pits, holes, edges, and discontinuities.

• 'aircraft body' means, unless otherwise stated, any external surface of an aircraft, including the fuselage, wings, tail, rudder, elevators, spoilers, slats, aileron, and flaps and other control surfaces.

· 'non-destructive inspection' means, unless otherwise stated, any non-destructive analysis technique used to inspect, test or evaluate the properties of a material, surface, component or system without causing damage.

• 'comprising' means 'consisting at least in part of. When interpreting a statement in this specification and claims that includes 'comprising', features other than that or those prefaced by the term may also be present. Related terms such as 'comprise' and 'comprises' are to be interpreted similarly. BRIEF DESCRIPTION OF DRAWINGS

The invention is further described with reference to the accompanying figures which show embodiments of the invention by way of example, and in which :

Figure 1 is a side elevation view from outside of a tracked climbing robot without inspection equipment.

Figure 2 is a cross-section view of the climbing robot of Figure 1 along line I-I of Figure 3.

Figure 3 is a front elevation view of the climbing robot of Figures 1 and 2.

Figure 4 is an underside view of the climbing robot of Figures 1 to 3. Figure 5 is a schematic plan view of the climbing robot of Figures 1 to 4, also showing, as shaded areas, some (but not all) locations where one or more non-destructive inspection equipment carried by the robot may be positioned when attached to the robot chassis i.e. 'payload' areas of the robot. Figure 6 is a perspective view of a climbing robot equipped with a camera system positioned to one side of the robot.

Figure 7 is a perspective view of a climbing robot equipped with a camera system positioned at the front of the robot.

Figure 8 is a view of a robot traversing an aircraft body with non-destructive inspection equipment mounted to the front and rear of the robot.

Figure 9 is a perspective view of a climbing robot equipped with a thermographic imaging system comprising an infrared camera and a thermal source positioned at the front of the robot.

Figure 10 is a top view of a robot traversing an aircraft body with non-destructive inspection equipment mounted to the front of the robot. Figure 11 is a perspective view of a climbing robot equipped with an ultrasonic transducer positioned at the front of the robot.

Figure 12 is a perspective view of a climbing robot equipped with a probe for eddy current testing positioned at the front of the robot.

Figure 13 is a perspective view of the rear portion of an aircraft body, showing the tail, rudder and elevators and a climbing robot inspecting a portion of the vertical rudder. Figure 14 is a perspective view of the middle portion of an aircraft body, showing a fuselage, a wing with flaps and a climbing robot inspecting a portion of the wing.

Figure 15 is a perspective view of a carriage which may attach to a robot in order to position one or more pieces of non-destructive inspection equipment.

DETAILED DESCRIPTION OF EMBODIMENTS Robot

Typically an industrial robot used in the inspection system of the invention comprises a passive vacuum based adhesion mechanism that is designed to adhere the robot to a surface on which the robot moves such as an inclined or inverted surface, while maintaining vacuum, and drive system arranged to move the robot on the surface, during which movement the adhesion mechanism remains adhered to but slides on the surface. A passive adhesion wall climbing robot is described in our international patent application publication WO2013/048263, the entire content of which is incorporated herein by reference.

Alternatively a robot used in the detection system of the invention may comprise an non- passive adhesion mechanism for attaching the robot to a surface, being an adhesion system comprising a remote vacuum pump - vacuum from which is coupled to a vacuum based adhesion system of the robot by a vacuum line. The robot typically also comprises a drive system, and the robot may not be intended to attach to and move on an inclined or inverted surface, but may be arranged to simply move on a horizontal or approximately horizontal surface for example, or on the exterior or interior surface of a cylindrical or approximately cylindrical element such as an aircraft fuselage, or an any complex curved surface such as an aircraft wing, or on a non-curved complex surface. Figures 1 to 4 depict an embodiment of a climbing robot. By 'climbing robot' is meant a robot which may move on a non-horizontal surface such as a vertical but alternatively an inclined surface for example, and/or on the exterior or interior surface of a cylindrical or approximately cylindrical element as referred to above. The platform has a chassis 1 which carries a pair of driven tracks 2. Each track is each driven by an electric motor or motors. In an alternative embodiment the chassis 1 carries wheels or rollers.

In the embodiment shown, multiple suction mechanisms comprise multiple suction pads or cups 3 carried by the chassis 1 and including deformable concave surfaces exposed on the underside of the robot which adhere the robot to the surface on which the robot moves, while the drive system moves the robot on the surface, during which movement the cups 3 remain adhered to but slide on the surface, holding the robot on the surface as it moves. An associated control system enables the robot to be driven and steered on the surface, under control of an operator, or according to a pre-programmed test regime for example. In the embodiment shown suction cups 3 are mounted to the chassis 1 via individual actuators (not shown) arranged to initially move the cups 3 towards the surface to expel air from between the cup and the surface, and then away from the surface without breaking the cup from the surface to create a relative vacuum between the cup and the surface effective to hold or assist holding the robot on the surface. One form of actuator has actuation rods and springs and cams driven by servo motors for example. Specifically, actuators move the suction pads toward the surface of the aircraft body by exerting a first force upon the suction pads 3 to deform the suction pads 3 such that the air is substantially or at least partially evacuated from beneath the suction pads. The actuators then move the suction pads sealed against the surface of the aircraft body, away from the surface, by exerting a second opposite force on the suction pads to pull the suction pads away from the surface of the aircraft body such that an adhesion relative vacuum or suction is created between the pads and the surface which adheres the robot to the surface. The magnitude of the second force applied to the suction pads controls the magnitude of the relative vacuum and therefore the adhesion force between the suction pads and the surface of the aircraft body. A controller may measure the level of the vacuum force generated by any of the suction pad(s) and/or the deformation of the suction pad and alter the second force to an optimum characteristic.

As stated in alternative embodiments a vacuum line may couple vacuum from a remote vacuum pump to the cups 3. In a further alternative embodiment the robot may carry a vacuum pump which may be powered by a line to a remote power source, or by a power source on board the robot.

Electronics on board the robot may include a controller to control the motors, actuators, interface with on-board sensors and communicate with a remote controller, for example wirelessly. In a passive vacuum system as described the controller may be configured to receive or determine information relating to the level of relative vacuum within the suction pad, and/or the estimated time remaining before vacuum is lost within the pad, for example. For example, the controller may be configured to receive a signal from a sensor that is adapted to measure the vacuum force under each attached suction pad. The controller uses the measured vacuum force to control actuators to re-prime the suction pads when the vacuum drops below a level that may cause the suction pad to detach from the surface. As stated the suction pads 3 slide against the surface of the aircraft body while maintaining a vacuum to keep the robot attached to the surface. Preferably the pads are made from a material which slides against the surface of the aircraft body material with minimal friction. The friction force of the suction pads is overcome by the drive system comprising driven tracks 2.

The embodiment shown in the figures comprises four suction mechanisms 3 supported by the chassis 1. Alternatively one, two, three, or more than four suction pads and associated actuators may be provided . Figure 5 depicts the preferred locations 5a-d where one or more pieces of non-destructive inspection equipment carried by the robot may be positioned when attached to the robot chassis 1 i.e. 'payload' areas of the robot, to enable the inspection and identification of defects on and in the material as the robot passes over its surface. The non-destructive inspection equipment can be for example, thermal sources and infrared cameras, used in thermography; ultrasonic transducers, transmitters and/or receivers, used in ultrasonic applications, or eddy current testing probes and/or arrays. These will be discussed in more specific detail below. Defect identification

During routine maintenance performed on an aircraft, it is intended that the robot be used to inspect composite, partly composite or metal such as aluminium or aluminium alloy parts of the aircraft body, for defects using non-destructive inspection equipment. These parts can include, but are not limited to, the rudder, elevators, spoilers, slats, aileron, flaps, wings and fuselage of an aircraft. The robot may be particularly useful for testing the integrity of carbon composite and part composite structures, carbon composite being a material which is now favoured in the construction of large airliners, but may be used for testing non-composite parts or structures also. These composite parts in aircraft are relatively new and therefore are mostly yet to undergo maintenance checks, however composites are becoming more common in the aviation industry so a reliable and effective solution which can perform highly repeatable, quantitative measurements is required to inspect these parts for defects. Typically, as seen in Figures 13 and 14, the robot 10 moves along a structure surface of an aircraft body, such as the rudder 19 or other part of the vertical stabiliser 18, elevators 17 or other part of the horizontal stabilisers 16, spoilers, slats, aileron, flaps 15, wings 14 and fuselage 12. As the robot 10 moves, non-destructive inspection equipment 20 which is carried by the robot scans the region it passes over for defects, and is able to reliably detect surface or under surface defects with a profile that may indicate a structural defect. For example structural damage or defects can include cracks, dis-bonding, delamination, water ingress, holes, dents, and corrosion. These defects can form for a number of reasons, including for example constant temperature changes, pressurization and depressurization, vibration, and high wind loads. Other factors such as condensation and water ingress can also cause cracks. In a preferred embodiment the non-destructive inspection equipment is integrated or permanently mounted to the chassis 1 or a housing of the chassis 1 of the robot 10. Alternatively the non-destructive inspection equipment may be releasably mounted to the chassis via a mounting system. The passive vacuum system used to attach the robot to the surface as previously described enables the robot to have a small size and also allows it to be light weight. This small form factor and the passive adhesion system allows the robot to traverse all areas of an aircraft body, giving it efficiency and versatility and enabling inspection of large areas of the exterior of the aircraft body, potentially in a single session using the robot. Furthermore, the small form factor and suction system allow the robot to inspect areas which traditionally have been very difficult to inspect, for example the vertical rudders which are difficult for a larger robot to scale. The robot also allows for delicate composite parts which are not able to support heavy downward loads to be inspected without causing damage. Currently, in order to perform inspection on the elevators of an aircraft as a part of routine maintenance, they must be removed from the aircraft and inspected in a hangar. This is time consuming. They also cannot support much downward force and so traditional methods of inspection, such as having a person standing on the elevators can cause potential structural damage. This may not necessarily be surface level damage, but could occur below the surface and be unnoticeable to the human eye. A robot of the invention will typically enable the elevators of an aircraft to be inspected in-situ without having to be removed . The small size and light weight of the robot facilitates this, without damage to the elevators.

In the preferred embodiment, the robot performs the inspection process while in constant motion. It performs continuous scanning of the surface as the robot moves across it. The non-destructive inspection equipment is set up in such a way to enable this to occur. For example, in thermographic imaging, the thermal source is mounted ahead of the infrared (IR) camera a predetermined distance, such that the robot will heat the surface as it passes over it, and will drive at such a speed such that when the IR camera passes over the heated area, the image received will be of ideal quality for defect identification to occur.

Alternatively, the thermal source may be mounted or directed to target an area at least of that on which the IR camera is focused, so that the area heated is able to be inspected constantly. The robot may be operator-controlled during inspection procedures, but may instead be arranged to carry out inspection procedures autonomously, without the need for a person to assess the data. Preferably, the robot is able to record information relating to the inspection, and specifically to the defects it finds. This information may be any one or more of the size, type, location, depth etc. of defect(s), as well as an image or images from a camera for later review. This is so the robot does not have to stop during the inspection process and can complete the inspection process faster. Alternatively, the robot may be set to stop when a defect is detected, so that the specific location of the defect can be noted and tracked. In some embodiments the robot also provides data indicative of the location, size and/or orientation of the cracks/defects from robot position data . The robot may also carry one or more sensors which enable it to determine the location of the robot with regard to its environment. For example the robot may comprise wheel encoders to determine location relative to a starting location by way of dead reckoning. The robot may alternatively use a visual or radar based localisation system and algorithms to gather information about its position within its environment. Alternatively, the robot may use mapping algorithms to determine its location. The system may combine location data with the data concerning the location of defects that have been detected in order to indicate the location of defects in the overall environment and to give higher resolution information regarding defects while the robot is in constant motion.

Visual Testing

In one embodiment, the robot is provided with equipment enabling it to perform visual inspection of a surface of an aircraft body. Performing a simple visual inspection is vital to ensure that aircraft are safe to fly. A visual inspection relies less on technology and equipment and more on the eyesight and experience of the person performing the inspection. The robot is equipped with camera systems that enable visual inspections to be carried out faster and with more accuracy than if performed manually. Robotic visual inspection using camera systems is more reliable at displaying faults, with the camera able to be set at a constant viewing distance and speed, lighting able to be kept consistent throughout testing, and issues relating to the individual or individuals performing the inspection for example poor vision and eyesight of manual visual inspectors not being a concern. Also, visual inspection using the robot equipped with a camera system 22 can be faster than inspection by a person, as the robot is able to manoeuvre around the different parts of the aircraft body more easily than a manual inspector. Visual inspection with a robot further allows for remote visual inspection (RVI) whereby the robot can inspect the aircraft body and feed visual images in real time to a trained person who is situated away from the robot and is able to view the visual images via a display and determine whether defects are present.

Figures 6 and 7 show embodiments of a robot equipped with a camera system. In Figure 6, the camera system 22 is attached to a mount 23 positioned to the side of the robot. In Figure 7, the camera system 22 is attached to a mount 23 positioned at the front of the robot. Thermography

In a further embodiment, the robot is provided with equipment enabling it to perform thermographic imaging of a surface of an aircraft body. The robot applies heat to the surface of an area of a material being tested and then acquires a thermal image of the sample surface as the heat dissipates into the material. Flaws in the material, including those not easily visible to the human eye can be detected . Defects such as for example cracks, dents, water ingress, delamination and corrosion will result in a different rate of heat dissipation compared to that displayed in a defect free structure.

Preferably the robot carries thermography equipment enabling it to determine the presence, type, location, size, and strength of defects in the structure over which it passes. Figure 8 shows a robot traversing an aircraft body with a thermal source 34 positioned at the front of a robot, used to change the temperature of the structure relative to the ambient

temperature in such a way as to produce detectable infrared intensity changes in a region of testing 38 that indicate a defect, and an infrared camera 36 positioned to the rear of the robot to detect the changes in infrared intensity in a region of scanning 39. Alternatively, the infrared camera can be placed anywhere on the robot so long as it is able to inspect or view the area of the surface of the aircraft body that has been heated by the thermal source.

Preferably in order for the robot to be able to use thermographic imaging to detect defects on the surface along which it is travelling it will position an infrared camera 36 at a known distance from the aircraft body, position a thermal source 34 over an area of the aircraft body 30, apply power to the thermal source so that said area of aircraft body 30 changes in temperature relative to the ambient temperature, and collect a data set of infrared images using the infrared camera 36 from the area of the surface of said aircraft body heated by the thermal source 34. The infrared camera 36 can preferably be placed anywhere on the robot so long as it is able to inspect or view the area of the surface of the aircraft body that has been heated by the thermal source. Combined with the robot, thermographic imaging inspection is a relatively fast because large areas can be inspected within a relatively short time. Typically the robot will only need to pass over a section of the robot once.

In another embodiment the type of thermographic imaging used by the robot may not require a thermal source, and may instead rely on thermal radiance naturally emitted from the object's surface - known as passive thermography. This can be used to look for specific types of faults which have a different thermal characteristic relative to the surrounding material at ambient temperature. Thermographic imaging provides a visual picture for comparison, so an area of potential interest can be easily compared with a previous inspection of the same part or the same part on a different aircraft. Similarly, it can detect more than defects but also deteriorating parts prior to failure which are not yet defective but may soon become. It is also a clean inspection, so couplants or penetrants are not needed .

Figure 9 shows an embodiment of a robot equipped with a thermographic imaging system comprising an infrared camera 36 and a thermal source 34 positioned at the front of the robot. In this embodiment, the infrared camera 36 is positioned above the thermal source 34.

Ultrasonic Testing

In a further embodiment, the robot is provided with equipment enabling it to perform ultrasonic testing of an aircraft body. Ultrasonic testing involves timing the propagation of ultrasonic waves directed through a material. The robot is provided with an ultrasonic transducer(s) or transmitter(s) and receiver(s). A transmitter can produce waves in a material which are detected by a receiver or alternatively a transducer performs both the transmitting and receiving when the wave is intended to be reflected.

There are many different forms of ultrasonic testing methods including ultrasonic thickness testing, time of flight diffraction (TOFD) and phased array testing that may be incorporated with the climbing robot in order to inspect for defects in aircraft bodies and parts. The robot may be arranged to perform ultrasonic thickness testing or ultrasonic thickness

measurement. In ultrasonic thickness measurement, an ultrasonic wave is emitted into a material directly normal to the surface. The wave will reflect off the back face of the material and travel back to the transducer or receiver, and the time of flight and thus the thickness of the material can be determined. Any variations in the thickness reading can indicate defects or variations which may need attention.

An embodiment is shown in Figure 10 of an ultrasonic transducer 31 mounted to the robot 10. The scanning region 33 at the front of the robot is indicative of the region an ultrasonic transducer or transducers or transmitters and receivers can inspect as the robot 10 is moving in a direction 32 along the aircraft body 30. Figure 11 shows an embodiment of a robot equipped with an ultrasonic transducer 31 positioned at the front of the robot. Eddy Current Testing

In a further embodiment, the robot carries eddy current testing equipment enabling it to perform eddy current testing (ECT) of an aircraft body. ECT involves the excitation of an electric current in a conductive material to be tested. ECT is sensitive and can detect small and tight cracks in a material. Variation in the electrical conductivity characteristics indicates the presence of abnormalities within the material. Eddy current testing, along with the other non-destructive inspection methods, enable testing the integrity of carbon composite structures.

The robot when provided with ECT equipment includes a probe or an array of probes that allow eddy currents to be induced in the aircraft body. The presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the probe(s). Using an array of ECT probes allows coverage of larger areas in a single pass while maintaining high resolution. In some cases, eddy current and ultrasonic testing are used together as complementary techniques, with eddy current having an advantage for quick surface testing and ultrasonics having better depth penetration. Figure 10 could similarly be applied to use with eddy current testing, with the non-destructive inspection equipment 20 may be being an eddy current probe 21 or eddy current array, and the scanning region being broadly identified by 33 as the robot 10 moves in a direction 32 along the aircraft body 30. Figure 12 shows an embodiment of a robot equipped with an eddy current probe 21 positioned at the front of the robot.

Carriage

The non-destructive testing equipment may be positioned anywhere on the robot.

Alternatively an articulating carriage which attaches to the robot may be used to position the non-destructive testing equipment on the robot. The carriage can help to keep nondestructive inspection equipment precisely positioned on or at a constant position from the aircraft body. A number of factors for example, movement of the robot as suction cups re- prime, rivets or bolts on the surface of the aircraft, or bumps and joints which the robot passes over can affect the positioning of non-destructive inspection equipment in relation to the aircraft body. Figure 15 shows an example embodiment of an articulating carriage which may attach to a robot in order to carry one or more of the non-destructive inspection equipment generally as described, at a constant distance or in constant contact with the surface of a material. The articulating carriage ensures that each piece of non-destructive testing equipment is always held at a constant position relative to the surface of the aircraft body which is being inspected, which may be a curved surface for example a surface with surface irregularities such as at a junction between two sheets of a material such as a weld seam, as the robot moves over the surface. The carriage 40 preferably comprises a bracket 41 which attaches to the robot chassis. An arm 42 can pivot and is spring biased by springs 45 towards the surface of the material to apply light force against the surface. The pivot and spring bias of the carriage allow it to maintain a constant position relative to the surface of the aircraft body. Outer end 42a of the arm 42 shows a potential mounting location for the non-destructive inspection equipment 20. The carriage preferably has a sub-assembly 47 comprising a subframe 48 pivotally mounted to the outer end of arm 42. Left and right parts 48I and 48r of subframe 48 each carry one of spring loaded wheels 44a, 44b via a small swing arm 49 pivotally carried by sub frame. This enables the non-destructive inspection equipment to remain consistent in relation to the surface of the aircraft body when the robot is moving. In an alternative embodiment the outer end 42a may also carry transducer wheels 43 that allow for ultrasonic inspection to be run through the wheel. Alternatively, the arm or arms may carry one or more than two transducer wheel(s), or transducer tracks. The spring loaded pivot also allows for limited torsional flexibility. In this way the system will naturally rock the carriage to ensure the spring loaded wheels 44a, 44b preferably have an equal amount of pressure distributed between them which ensures the non-destructive inspection equipment remain consistent in relation to the aircraft body.

Other

In some embodiments the robot may be equipped with more than one form of nondestructive inspection equipment. For example the robot may have both an eddy current testing probe(s) positioned with an ultrasonic transducer(s) or transmitter(s) and receiver(s), alternatively, the robot may have thermographic imaging equipment and ultrasonic transducer(s) or transmitter(s) and receiver(s). In some embodiments movement of the robot may be controlled manually by an operator via a remote control for example. The robot may communicate data to a remote processor such as a mobile computer e.g . laptop, which displays scan information graphically for interpretation by the operator.

Alternatively, the robot may be equipped with an on board processor and be able to perform real time defect identification. The robot may also carry a camera and for example video may be displayed to the operator separately from or combined with other graphical display of defect information. In other embodiments a control system on board the robot or remote from the robot may cause the robot to move over the surface in a predetermined search path or pattern, for example in a grid search around and up and down the body or selected regions of an aircraft, such as the rudder or other part of the vertical stabiliser, elevators or other part of the horizontal stabilisers, spoilers, slats, aileron, flaps, wings and fuselage. The control system may be arranged to cause the robot after making an initial search over the surface to then return to one or more areas of the surface such as area(s) in which defects have been identified or are likely, to more closely/finely survey these areas. The system may also be arranged to carry out some data analysis or image analysis of the robot- provided data or image stream, for defects or potential defects, and to provide an indication to an operator or to record information on defects and/or defect type and/or defect location.

The foregoing describes the invention including preferred forms thereof and alterations and modifications as will be obvious to one skilled in the art are intended to be incorporated in the scope hereof as defined in the accompanying claims.