WO2018206983A1

WO2018206983A1 - Shunt device

Info

Publication number: WO2018206983A1
Application number: PCT/GB2018/051288
Authority: WO
Inventors: James Oliver HELLIWELL; Anthony Richard Glover; Anthony David LAW
Original assignee: Mclaren Applied Technologies Limited
Priority date: 2017-05-12
Filing date: 2018-05-11
Publication date: 2018-11-15
Also published as: GB201707691D0

Abstract

A shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising: a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a first rotation centre on the first rotation axis within the first support wheel; and a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located behind a first plane perpendicular to the shunt direction and that passes through the first rotation centreand between (i) a second plane generally parallel to the surface and coincident with the first rotation centre and (ii) the surface; wherein contact between the shuntdevice and the ground wheel is via the roller from behind the ground wheel in the shunt direction.

Description

SHUNT DEVICE

This invention relates to a shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle.

In the periods before take off and after landing but before an aircraft is docked at a gate at an airport, aircraft need to move around the airport. I.e. to move between a position near a gate where a tow truck can move the aircraft to/from the gate and a position where the aircraft can take off or has landed. It is usual for an aircraft to move between these positions under the aircraft's own power. This is generally by using the main engines of the aircraft for thrust to enable the aircraft to move around the airport on its ground wheels.

The main engines of a normal sized passenger aircraft are usually so powerful that the minimum power that they can run at above idle is much greater than the power needed to move the aircraft around the airport at an acceptable (e.g. generally low) speed. Therefore, the brakes on the ground wheels are usually applied to keep the speed of the aircraft at or below an acceptable level when taxiing around the airport. Such taxiing using the aircraft's engines is inefficient as it burns more fuel than is actually required to move the aircraft at the required speed and it also increases brake wear as the brakes are being applied to some degree almost constantly. This also has the side effect of increasing C02 emissions and reducing local air quality.

There are ways of moving the aircraft around on the ground without using the aircraft's engines. These usually involve a tug vehicle that latches on to at least one of the landing gear of the aircraft. The tug vehicle can then push and/or pull the aircraft to move it. The tug vehicle is usually used in the process of docking and/or undocking the aircraft from a gate at the airport. As discussed above, it is usual for the rest of the time for the aircraft to move under its own power. The disadvantage of such tug vehicles is that they are generally fitted with large weights so that their wheels have sufficient traction with the ground to enable them to provide force to the aircraft. This makes such tug vehicles bulky and heavy which reduces their suitability for moving the aircraft around the airport more generally. They tend to only be capable of moving the aircraft at very low speeds and not even up to the normal taxiing speed of an aircraft around an airport.

This same problem applies more generally to (potentially large) wheeled vehicles that may need to be moved around with an accuracy and speed that is not easily achievable by the wheeled vehicle on its own or when it is not desirable for the vehicle to move using its own power source.

It would therefore be desirable for there to be an improved shunt device that is capable of moving a vehicle, whilst it is on the ground, by applying force to that vehicle.

According to a first aspect of the present invention there is provided a shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising: a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a first rotation centre on the first rotation axis within the first support wheel; a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located behind a first plane perpendicular to the shunt direction and that passes through the first rotation centre.

According to a second aspect of the present invention there is provided a shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising: a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a first rotation centre on the first rotation axis within the first support wheel; and a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located behind a first plane perpendicular to the shunt direction and that passes through the first rotation centre and between (i) a second plane generally parallel to the surface and coincident with the first rotation centre and (ii) the surface; wherein contact between the shunt device and the ground wheel is via the roller from behind the ground wheel in the shunt direction. The first support wheel may be a drive wheel. The shunt device may comprise a second support wheel configured to rotate about a third rotation axis so that the second support wheel has a second rotation centre on the third rotation axis within the second support wheel. The second support wheel may be positioned so that the second rotation centre is on the first plane. The first rotation centre and second rotation centre may be on a straight line perpendicular to the shunt direction. The shunt device may comprise a device body configured to receive the ground wheel between the support wheels to permit the roller to contact the ground wheel. The support wheels may be spaced apart from each other so that the ground wheel can be positioned between them to permit the roller to contact the ground wheel. The first support wheel and second support wheel may be drive wheels.

The roller may be positioned relative to the support wheel(s) so that the second rotation axis within the roller is located between (i) a second plane generally parallel to the surface and coincident with the first rotation centre and (ii) the surface. The ground wheel may be configured to rotate about a fourth rotation axis, and the roller may be positioned relative to the support wheel(s) so that, when the roller contacts the ground wheel, a straight line that passes through the first and fourth rotation axes in a medial plane of a support wheel also passes through a projection of the roller on to the medial plane. The straight line may also pass through the second rotation axis.

The ground wheel may be configured to rotate about a fourth rotation axis, and the roller may be positioned relative to the support wheel(s) so that, when the roller contacts the ground wheel, a straight line passes through the first rotation centre, second rotation axis and fourth rotation axis at the points where the first rotation centre, second rotation axis and fourth rotation axis cut through a plane perpendicular to the first rotation centre. The ground wheel may be configured to rotate about a fourth rotation axis, and the roller may be positioned relative to the support wheel so that, when the roller contacts the ground wheel, the first rotation centre, second rotation axis and fourth rotation axis are substantially coplanar.

The roller may be positioned relative to the support wheel(s) so that the second rotation axis within the roller is located above a second plane generally parallel to the surface and coincident with the first rotation centre. The roller may be free to rotate about the second rotation axis. The shunt device may comprise a first drive source; and wherein the first support wheel may be coupled to the first drive source to cause the first support wheel to rotate about the first rotation axis to move the shunt device. The second support wheel may be coupled to the first drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device. The shunt device may comprise a second drive source; and wherein the second support wheel may be coupled to the second drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device. The roller may be coupled to the first drive source to cause the roller to rotate about the second rotation axis. The support wheel(s) and the roller may be coupled to the first drive source so that the support wheel(s) and the roller rotate at fixed relative angular speeds. The support wheel(s) and the roller may be coupled to the first drive source so that the support wheel(s) and the roller rotate at variable relative angular speeds.

The shunt device may comprise a third drive source; and wherein the roller may be coupled to the third drive source so that the third drive source can cause the roller to rotate about the second rotation axis. The shunt device may be configured to control the angular speeds of the first and third drive sources separately. The shunt device may be configured to control the torque of the first and third drive sources separately. The shunt device may comprise a power source for the drive source(s). The drive source(s) and/or the power source may be positioned on the shunt device behind the first rotation axis along the shunt direction. The drive source(s) may be electric motors. The shunt device may be configured to alter the position of the roller to move the second rotation axis in dependence on the size of the ground wheel. The shunt device may comprise one or more other support wheels configured to support the shunt device on a surface. The shunt device may be configured to control the position of the one or more other support wheels to cause the shunt device to rotate about a vertical rotation axis.

The shunt device may be configured to control the rotation of the drive wheel(s) about the first rotation axis to cause the shunt device to rotate about a vertical rotation axis. The drive wheel may support the shunt device on a surface; the shunt device may comprise a skirt configured to seal against the surface to define an area under the shunt device; and the shunt device is configured to reduce the air pressure in the area under the shunt device. The shunt device may comprise one or more sensors, the shunt device may be configured to control the operation of the support wheel(s) in response to inputs from the one or more sensors. The one or more sensors may detect the presence of objects in the motion path of the shunt device and the shunt device may be configured to avoid the objects in response to their detection. The shunt device may be configured to operate in a first drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device without drive control inputs external to the shunt device.

The shunt device may be configured to operate in a second drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device in response to commands received from a user. When the shunt device is operating in the second drive mode, the shunt device may control the operation of at least one drive wheel of the shunt device to drive the shunt device in response to commands received from a user and from sensing data received from one or more sensors. The wheeled vehicle may be an aeroplane, and the shunt device may be configured to move the aeroplane by applying force to the ground wheel of the aeroplane.

According to a third aspect of the present invention there is provided a shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising: a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a rotation centre on the first rotation axis within the first support wheel; a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located on a first line perpendicular to the shunt direction and that passes through the first rotation centre. According to a fourth aspect of the present invention there is provided a shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising: a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a rotation centre on the first rotation axis within the first support wheel; a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located on a first line perpendicular to the shunt direction and that passes through the first rotation centre; a first drive source, the first support wheel being coupled to the first drive source to cause the first support wheel to rotate about the first rotation axis to move the shunt device; and a third drive source, the roller being coupled to the third drive source so that the third drive source can cause the roller to rotate about the second rotation axis; wherein the shunt device is configured to control the angular speeds of the first and third drive sources separately.

The first support wheel may be a drive wheel. The shunt device may comprise a second support wheel configured to rotate about a third rotation axis so that the second support wheel has a second rotation centre on the third rotation axis within the second support wheel. The second support wheel may be positioned so that the second rotation centre is on the first line. The shunt device may comprise a device body configured to receive the ground wheel between the support wheels to permit the roller to contact the ground wheel. The support wheels may be spaced apart from each other so that the ground wheel can be positioned between them to permit the roller to contact the ground wheel. The first support wheel and second support wheel may be drive wheels.

The roller may be free to rotate about the second rotation axis. The shunt device may comprise a first drive source; and wherein the first support wheel may be coupled to the first drive source to cause the first support wheel to rotate about the first rotation axis to move the shunt device. The second support wheel may be coupled to the first drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device. The shunt device may comprise a second drive source; and wherein the second support wheel may be coupled to the second drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device.

The roller may be coupled to the first drive source to cause the roller to rotate about the second rotation axis. The support wheel(s) and the roller may be coupled to the first drive source so that the support wheel(s) and the roller rotate at fixed relative angular speeds. The support wheel(s) and the roller may be coupled to the first drive source so that the support wheel(s) and the roller rotate at variable relative angular speeds.

The shunt device may comprise a third drive source; and wherein the roller may be coupled to the third drive source so that the third drive source can cause the roller to rotate about the second rotation axis. The shunt device may be configured to control the angular speeds of the first and third drive sources separately. The shunt device may be configured to control the torque of the first and third drive sources separately. The shunt device may comprise a power source for the drive source(s). The drive source(s) and/or the power source may be positioned on the shunt device behind the first rotation axis along the shunt direction. The drive source(s) may be electric motors. The shunt device may be configured to alter the position of the roller to move the second rotation axis in dependence on the size of the ground wheel. The shunt device may comprise one or more other support wheels configured to support the shunt device on a surface. The shunt device may be configured to control the position of the one or more other support wheels to cause the shunt device to rotate about a vertical rotation axis. The shunt device may be configured to control the rotation of the drive wheel(s) about the first rotation axis to cause the shunt device to rotate about a vertical rotation axis. The drive wheel may support the shunt device on a surface; the shunt device may comprise a skirt configured to seal against the surface to define an area under the shunt device; and the shunt device may be configured to reduce the air pressure in the area under the shunt device.

The shunt device may comprise one or more sensors, the shunt device may be configured to control the operation of the support wheel(s) in response to inputs from the one or more sensors. The one or more sensors may detect the presence of objects in the motion path of the shunt device and the shunt device may be configured to avoid the objects in response to their detection. The shunt device may be configured to operate in a first drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device without drive control inputs external to the shunt device.

According to a third aspect of the present invention there is provided A method for a shunt device engaging with a ground wheel of a wheeled vehicle to push the ground wheel in a shunt direction, the method comprising: receiving location data comprising a docking location; navigating to the docking location; detecting the ground wheel at the docking location; and engaging with the ground wheel, based on the detection of the ground wheel, from behind the ground wheel in the shunt direction.

The method may comprise pushing the ground wheel in the shunt direction after engaging with the ground wheel. The method may comprise: receiving a push command from a user to push the shunt device in the shunt direction; and in response to the push command, pushing the ground wheel in the shunt direction after engaging with the ground wheel. The method may comprise: receiving a reverse push command from a user to push the shunt device in the opposite direction to the original shunt direction; in response to the reverse push command, disengaging with the ground wheel and engaging with the ground wheel from behind the ground wheel in the opposite direction to the original shunt direction. The docking location may specify a location area for the wheeled vehicle. The docking location may specify a location area for the ground wheel. The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

Figure 1 shows an illustration of a shunt device.

Figure 2 shows a schematic plan view of a shunt device.

Figure 3 shows a schematic side view of a shunt device illustrating the position of rotational axes.

Figure 4 shows a schematic side view of a shunt device comprising a continuous track drive system.

Figure 5 shows a schematic side view of a shunt device comprising a skirt.

Figure 6 shows a schematic plan view of an aircraft and two shunt devices.

Figure 7 shows a schematic plan view of a shunt device illustrating the position of rotational axes.

Figure 8 shows a flow chart of a method of a shunt device engaging with a ground wheel.

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. The present invention relates to a shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle. The shunt device comprises a first support wheel configured to support the shunt device on a surface. The first support wheel is configured to rotate about a first rotation axis so that the first support wheel has a first rotation centre on the first rotation axis within the first support wheel. The shunt device may also comprise a roller configured to rotate about a second rotation axis. The shunt device may comprise a single roller configured to rotate about a second rotation axis. The roller is configured to contact the ground wheel to push the wheeled vehicle in a shunt direction. The roller is positioned relative to the support wheel so that the second rotation axis within the roller is located behind a first plane perpendicular to the shunt direction and that passes through the first rotation centre. The shunt device may comprise more than one support wheel. I.e. it might comprise a second support wheel configured to rotate about a third rotation axis so that the second support wheel has a second rotation centre on the third rotation axis within the second support wheel. The second support wheel may be aligned with the first support wheel so that the first and second rotation centres are located on a straight line perpendicular to the shunt direction. The first and third rotation axis may be collinear. Those two support wheels may be spaced apart from one another to perm it the ground wheel to be positioned in between to contact the roller. The shunt device may be configured so that contact between the shunt device and the ground wheel is from behind the ground wheel in the shunt direction. The shunt device may only contact the ground wheel from behind the ground wheel in the shunt direction. The shunt device may be configured so that contact between the shunt device and the ground wheel is via the roller from behind the ground wheel in the shunt direction. The only contact between the shunt device and the ground wheel may be from behind the ground wheel in the shunt direction. The only contact between the shunt device and the ground wheel via roller(s) may be from behind the ground wheel in the shunt direction. Figure 1 shows an illustration of a shunt device 1 . The shunt device 1 comprises a first support wheel 2 and a second support wheel 3. The shunt device 1 comprises a device body 4 which can house components of the shunt device 1. The support wheels 2, 3 are shown as being exterior to the device body 4 however the support wheels may be generally housed within the device 4 with only a part of the support wheels protruding to make contact with a surface on which the shunt device 1 can move.

The shunt device 1 may comprise one or more sensors 5 which the shunt device 1 may use to gather information about the environment in which the shunt device 1 operates. The shunt device 1 may make use of the information gathered by the sensors 5 to assist in navigating over the surface. The shunt device 1 may comprise one or more transceivers 6 to send and receive data with other devices. The shunt device 1 may use the transceiver(s) 6 to communicate with a controller to assist in navigating over the surface. The shunt device 1 may receive commands which the shunt device 1 interprets to plot a course over the surface. The sensors 5 and transceiver 6 are shown as being on the outside of shunt device body 4, however it will be appreciated that one or more of these components may be mounted flush with the surface of the shunt device body 4 or may be comprised within the shunt device body 4. The shunt device 1 may be configured to control the operation of one or more of the support wheels in response to inputs received from the one or more sensors and/or one or more transceivers 6. The sensor(s) may be configured to detect the presence of objects in the motion path of the shunt device 1. The shunt device 1 may be configured to use the detection of objects in the motion path to avoid those objects. The shunt device 1 may be configured to use the detection of objects in the motion path to drive towards an object, for instance, if the object that is detected is a ground wheel of the vehicle that is to be shunted.

The shunt device 1 is configured to apply force to a ground wheel 7 of a vehicle 8 so that the vehicle can be moved by the shunt device 1. The shunt device 1 may be configured so that it can move the vehicle 8 without requiring a mechanical attachment to the vehicle. I.e. the shunt device 1 can push against the ground wheel 7 without needing to be physically attached to the wheel 7 or the vehicle 8. The shunt device 1 may be configured so that it can move the vehicle 8 without encircling the ground wheel 7. As shown in figure 1 , the ground wheel 7 is only in contact with the shunt device from one side of the ground wheel. As pictured in figure 1 , the vehicle 8 may comprise more than one ground wheel 7 to which the shunt device 1 applies force. The vehicle 8 may be an aeroplane and the ground wheel 7 may form part of the landing gear of the aeroplane. Thus, when the vehicle 8 is on the ground the vehicle 8 may be supported on the ground by ground wheel 7. When the vehicle 8 is not on the ground the ground wheel 7 may be stowed inside the vehicle 8. In the case of an aircraft, this may be done, for example, to improve the aerodynamics of the vehicle 8.

The shunt device 1 may also comprise a charging port 9 to which a fuel recharging supply can be attached. In the example case that the motive power of the shunt device 1 is provided by electric motors then the charging port 9 may be configured to connect to an electrical supply to receive electricity to recharge an on-board energy store such as a battery. In the example case that the motive power of the shunt device 1 is provided by at least one engine burning combustible fuel then the charging port 9 may be configured to connect to the fuel supply to recharge an on-board fuel tank. There may be some combination of the two or other types of power supply.

Figure 2 shows a schematic plan view of the shunt device 1. Figure 2 is used to show the relative positions of elements of the shunt device 1 when a ground wheel 7 of the vehicle is in a position relative to the shunt device 1 where the shunt device 1 can apply force to that wheel 7.

As shown in figure 2, the first and second support wheels 2, 3 are configured to rotate about a first rotation axis 19 so that each of the first and second support wheels have a first and second rotation centre 31 , 32 respectively on the first rotation axis within the respective support wheel 2, 3. The first and second support wheels 2, 3 may be configured to rotate about different rotation axes, for instance if the wheels 2, 3 have opposite camber and/or toe in. The first support wheel 2 may be configured to rotate about a first rotation axis so that the first support wheel 2 has a first rotation centre 31 on the first rotation axis within the first support wheel 2, and the second support wheel 3 may be configured to rotate about a third rotation axis so that the second support wheel 3 has a second rotation centre 32 on the third rotation axis within the second support wheel 3. The rotation centres may be the portion of the rotation axis that the respective support wheel rotates about that is located within the support wheel. The shunt device 1 may comprise only one support wheel 2 that is configured to rotate about the first rotation axis. In this configuration the shunt device 1 may only have one support wheel 2 at the end of the shunt device 1 where the shunt device 1 interfaces with the ground wheel 7. The support wheel(s) 2, 3 that rotate about the first rotation axis, and in some cases second rotation axis, may be drive wheels of the shunt device 1.

The shunt device 1 may comprise a roller 20. The shunt device 1 may comprise a single roller 20. The roller 20 is configured to rotate about a second rotation axis 21. The roller 20 may be attached to the shunt device body 4 by at least one arm 22. As shown in figure 2, the roller 20 may be attached to the shunt device body 4 by two arms: one located at each end of the roller 20. The roller 20 may be attached directly to shunt device body 4. The roller 20 may extend across the width of an aperture 23 in the shunt device body 4 that is configured to receive, at least partially, the ground wheel 7. The arms 22 or other attachment of the roller 20 to the shunt device body 4 may permit the translational movement of the roller 20 relative to the shunt device body 4. This movement permits the movement of the second rotational axis 21 relative to the rotational centres 31 , 32 of the support wheel(s) that rotate about respective rotational axes. Such motion may be advantageous to enable the shunt device 1 to apply force to many different sizes of ground wheel 7 to enable the advantageous configuration of axes and rotation centres as described herein. Whilst the roller 20 is pictured as being one solid element, it will be appreciated that the roller 20 could be formed of a plurality of elements. Those plurality of elements may be spaced apart from each other, at least some of the elements may be in contact with other elements, the elements may be in a line along the second rotation axis 21 and in contact with the elements to either side of a respective element.

As shown in figure 2, the body 4 is shaped so as to receive the ground wheel 7 between support wheels 2, 3.

The shunt device 1 may comprise at least one other support wheel 24 that are configured to rotate relative to the shunt device 1 . These support wheel(s) 24 may be configured to support the shunt device on a surface and permit motion of the shunt device 1 relative to the surface. At least one of the other support wheel(s) 24 may be attached to the shunt device body 4 by a steering mechanism that permits the support wheel(s) 24 to rotate about a vertical axis to cause the shunt device 1 , when in motion, to rotate about a vertical axis. The shunt device 1 may be configured to control the position of the support wheel(s) 24 to cause the rotation of the shunt device 1 about the vertical axis.

The shunt device 1 may comprise a power source 26. The power source 26 may be a fuel tank. The power source 26 may be a battery. The shunt device 1 may be equipped with more than one power source 26 depending on the types of power that are used to generate energy on the shunt device 1 . As shown in figure 2, the power source 26 may be positioned behind a first plane perpendicular to the direction in which the shunt device 1 shunts the ground wheel 7 and that passes through at least the first rotation centre 31 of the first support wheel 2. The first plane is shown generally at 19 and runs into and out of the page. Such a position is advantageous because it uses the power source 26 as a counter balance on the shunt device 1 to counteract any force exerted on the shunt device 1 by the ground wheel 7 during a shunting operation.

The first and/or second support wheels 2, 3 may be drive wheels. The shunt device 1 may comprise a first drive source 27. The first support wheel 2 may be coupled to the first drive source 27 so that the first drive source 27 can cause the first support wheel

2 to rotate about the first rotation axis 19. As the first support wheel 2 is supporting the shunt device 1 against a surface, the rotation of the first support wheel 2 causes the shunt device 1 to move relative to the surface. The second support wheel 3 may also be coupled to the first drive source 27 to cause the second support wheel 3 to rotate about the third rotation axis 19. The rotation of the second support wheel 3 will cause the shunt device 1 to move relative to the surface as the second support wheel

3 is also supporting the shunt device 1 against the surface. Thus, the first drive source 27 may cause the first support wheel 2 and the second support wheel 3 to rotate in unison.

As shown in figure 2, the shunt device 1 may comprise a second drive source 28. The second support wheel 3 may be coupled to the second drive source 28 so that the second drive source 28 can cause the second support wheel 3 to rotate about the third rotation axis 19. The shunt device 1 may be configured to independently control the rotation of the first drive source 27 and the second drive source 28 and thus independently control the rotation of the first support wheel 2 and the second support wheel 3. Thus, the shunt device 1 may be able to control the rotation of the first and second support wheels about their respective rotation axes to cause the shunt device 1 to rotate about a vertical rotation axis. In other words, the shunt device 1 can control the first and second drive sources to steer the shunt device 1 as it moves over the surface.

The shunt device 1 may comprise a third drive source 29. This third drive source 29 may be coupled to the roller 20 so that the third drive source 29 can cause the roller 20 to rotate about the second rotation axis 21. As the roller 20 contacts the ground wheel 7, the rotation of the roller 20 will impart a rotation on the ground wheel 7 that will cause the ground wheel 7 to move relative to the surface. Thus, in addition to the roller 20 contacting the ground wheel to push the ground wheel in a shunt direction 30 which causes it to rotate due to the forward force imparted on the ground wheel 7 causing it to roll over the surface the roller 20 can apply a rotational force on the ground wheel 7 to cause it to rotate.

The roller 20 may be free to rotate about rotational axis 21. For example, the roller 20 may not be coupled to a drive source and so free to rotate in contact with the ground wheel 7 so that the surface speed of the ground wheel 7 and the roller 20 is the same.

The roller 20 may be coupled to a drive source that is also coupled to one of the support wheels. For instance, roller 20 may be coupled to the first drive source 27 which is also coupled to, at least, the first support wheel 2. In this case, the first drive source 27 may cause both the roller 20 and, at least, the first support wheel 2 to rotate at the same time. There may be a gearing in the coupling between the first drive source 27 and the roller 20 and/or between the first drive source 27 and the first support wheel 2. This gearing may mean that the roller 20 and the first support wheel 2 can rotate at the same time or it can be selected whether both the roller 20 and first support wheel 2 rotate at the same time. The gearing may mean that the roller 20 and the first support wheel 2 can rotate at a fixed relative angular speed. I.e. there is a fixed difference in gear ratio between the first drive source 27 and the roller 20 and between the first drive source 27 and the first support wheel 2. The gearing may mean that the roller 20 and the first support wheel 2 can rotate at variable relative angular speeds. I.e. there is a variable difference in gear ratio between the first drive source 27 and the roller 20 and between the first drive source 27 and the first support wheel 2. The gearing may mean that different torques can be applied to the roller 20 and the first support wheel 2 so that the roller and wheel rotate at speeds proportional to the force being delivered by the roller and wheel. In this way, the gearing may be a differential that is configured to deliver a respective torque from the first drive source 27 to the first support wheel 2 and roller 20. Each of the drive sources that are coupled to support wheels and/or the roller are each capable of providing a rotational drive. For example, each of the drive sources may be an electric motor, an internal combustion engine, or another fuel burning engine.

The shunt device 1 may comprise a processor 33 and a non-volatile memory 34. The shunt device 1 may comprise more than one processor 33 and more than one memory 34. The memory 34 stores a set of program instructions that are executable by the processor, and reference data such as look-up tables that can be referenced by the processor in response to those instructions. The processor 33 may be configured to operate in accordance with a computer program stored in non-transitory form on a machine-readable storage medium. The computer program may store instructions for causing the processor to perform the operations of the shunt device 1 in the matter described herein.

Figure 3 shows a side schematic view of the shunt device 1. In figure 3, a number of components are not shown so as to illustrate the relative positions of the rotation axes of the wheels.

As shown in figures 2 and 3, the ground wheel 7 is configured to rotate about a fourth rotation axis 40. The first and second rotation axes 19 and 21 may be at least generally parallel to each other. The first and second rotation axes 19 and 21 may be parallel to each other. In either case, this aids in pushing the ground wheel in the shunt direction 30 because the straight line force of the shunt device 1 due to the driven motion of the first and second support wheels 2, 3 will correspond with the force transmitted by the roller 20 to the ground wheel 7. It is advantageous if the roller 20 is positioned, relative to the support wheel(s) 2, 3 that rotate about the first rotation axis 19, behind a first plane perpendicular to the shunt direction 30 and that passes through the first rotation centre 31. The shunt device 30 pushes the ground wheel 7 in the shunt direction 30 and thus the first rotation centre 31 is in front of the second rotation axis 21 along the shunt direction. This is advantageous because it means that the shunt device 1 is less likely to tip up or lose grip on the support wheels 2, 3 when pushing the ground wheel 7 relative to the roller being in front of the first rotation axis 19 in the shunt direction 30. This is because, when the roller 20 is behind the first rotation centre 31 , if the roller is below (i.e. closer to the surface) than the first rotation axis 19 the shunt device 1 is less likely to rotate about the first rotation axis 19 when applying force to the ground wheel 7. This is opposite to what would happen if the roller 20 was in front of the first rotation centre 31 whereby the force acting on the roller 20 would cause a lifting of the rear of the shunt device 1 unless the rear of the shunt device 1 was weighed down by a counterbalance. The same point applies if the roller 20 was behind but above the first rotation centre 31 .

It is even more advantageous if the roller 20 is positioned, relative to the support wheel(s) 2, 3 that rotate about the first rotation axis 19, (i) behind a first plane perpendicular to the shunt direction 30 and that passes through the first rotation centre 31 and (ii) so that the reaction force from the ground wheel 7 on roller 20, when pushing the ground wheel 7, causes a zero moment or an anticlockwise moment to be imparted on the shunt device body 4 about the rotational axes of support wheel(s) 2, 3. An anticlockwise moment is particularly advantageous because it causes any wheels located behind the rotational axes of the support wheel(s) 2, 3 to be pushed against surface 42 which can increase the grip of those wheels.

If the roller 20 is positioned so that the second rotation axis 21 is located below a second plane 41 generally parallel with the surface 42 on which the shunt device 1 rests and coincident with the first rotation axis 19, the contact with the ground wheel 7 is likely to push the front support wheels 2, 3 against the surface 42. This is likely to increase the grip of the front support wheels 2, 3 on the surface 42. If the shunt device 1 is resting on a generally horizontal surface, then the second plane is a generally horizontal plane that is coincident with the first rotation axis 19. The second rotation axis 21 will therefore be below that generally horizontal plane that is coincident with the first rotation axis 19. Therefore, the roller 20 may be positioned relative to the support wheel 3 so that the second rotation axis is located between (i) a second plane 41 generally parallel to the surface (within the periphery of the shunt device) and coincident with the first rotation axis 19 and (ii) the surface 42 (within the periphery of the shunt device).

As shown in figure 3, the roller 20 may be positioned relative to the support wheel 3 so that when the roller contacts the ground wheel 7, the first rotation centre, second rotation axis and fourth rotation axis are substantially coplanar. This is shown by line 43 which shows the plane running perpendicular to the page in which all three rotation axes are parallel to. This is an ideal advantageous configuration because the normal force (the force acting in a radial direction of the wheel 7) that acts on the roller from the ground wheel 7 passes along line 43 and thus through the first rotation axis 19. This means that the normal force can be resolved into two parts: one force that is opposite to the shunt direction which the shunt device 1 can push against, and another force that acts directly downwards through the second rotation axis 21 of the roller 20. This vertical force is reacted by the respective normal forces between the support wheels 2, 3 and the ground 42. Therefore, the grip of the support wheel 3 against the surface is increased. Thus, in this situation the pushing against the ground wheel 7 directly increases the grip of the support wheel 3.

The roller 20 may also be positioned relative to the support wheel(s) so that, when the roller contacts the ground wheel, the first rotation centre, second rotation axis and fourth rotation axis form, in a plane (parallel to the page in figure 3) that cuts through the first rotation centre, second rotation axis and fourth rotation axis in a region where the roller contacts the ground wheel, a straight line at the points where the first rotation centre, second rotation axis and fourth rotation axis cut through that plane. The roller 20 may be positioned relative to the support wheel(s) so that, when the roller contacts the ground wheel, a straight line passes through the first rotation centre, second rotation axis and fourth rotation axis form at the points where the first rotation centre, second rotation axis and fourth rotation axis cut through a plane perpendicular (parallel to the page in figure 3) to the first rotation centre. There can be some latitude in the positioning of the roller 21 relative to the first rotation axis 19 when the roller 21 is in contact with the ground wheel 7 to still gain the advantage outlined above if the normal force generally resolves in a vertical direction close to going through the first rotation axis 19. The support wheel 2 may define a medial plane 44. This is the plane 44 that is generally perpendicular to the first rotation axis 19 and passes through the support wheel 2. The medial plane 44 may pass through the middle of the support wheel 2 in the direction defined by the first rotation axis 19. The roller 20 can be positioned so that, when the roller 20 contacts the ground wheel 7, a straight line 43 that passes through the first and fourth rotation axes in the medial plane of the support wheel also passes through a projection of the roller 20 on to the medial plane 44. The roller 20 may generally be offset from the support wheel 2 and hence it is the projection of the roller's position on to the medial plane 44 that the straight line 43 passes through. As can be seen in figure 3 by lines 45 and 46 this gives some latitude in the positioning of the roller 21 because the straight line of the first and fourth axes, in the example shown in figure 3, could be placed anywhere on or between lines 45 and 46.

The roller 20 may be positioned relative to the support wheel(s) 2, 3 configured to rotate about the first rotation axis 19 (and potentially third rotation axis) so that the roller 20 is forward of the rotation axis of the rear most support wheel 24, or support wheels, in the shunt direction. This is so that the shunt device 1 does not tip backwards when pushing the ground wheel 7. As discussed above, the shunt device 1 may be configured to permit the movement of roller 20 relative to the shunt device body 4 so that the second rotational axis 21 of roller 20 may be repositioned depending on the size of the ground wheel 7 and thus the position of the fourth rotational axis 40 when the roller 20 is in contact with the ground wheel 7.

As shown in figure 3, as described herein, various components 35 of the shunt device 1 may be positioned behind the first rotation axis in the shunt direction 30. The shunt device 1 may be configured so that the shunt device 1 only contacts the ground wheel 7 from one direction. This direction is shown as being from behind the ground wheel 7 in the shunt direction 30. The shunt device 1 contacts the ground wheel via roller 21 from behind the ground wheel 7 in the shunt direction 30. The shunt device is configured so that there is no contact with the ground wheel from in front of the ground wheel 7 in the shunt direction 30. I.e. there are no rollers located and in contact with the ground wheel from in front of the ground wheel 7 in the shunt direction 30. Contact between the shunt device and the ground wheel may be solely via the roller from behind the ground wheel in the shunt direction. This is advantageous because it means that the shunt device 1 can quickly engage with the ground wheel as the only primary contact for force transmission to the ground wheel is from behind the ground wheel in the shunt direction. The shunt device does not grip the ground wheel but just pushes the ground wheel. Figure 4 shows a second shunt device 36 as generally configured as described herein and in accordance with the present invention. In this case, the support wheel 37 that rotates about a first rotation axis 51 is part of a continuous track drive system 38. The support wheel 37 may be a driven wheel and so drive the track 39 of the continuous track drive system 38. Alternatively or as well as, at least one other wheel 53, 54, 55, 56 of the continuous track drive system 38 may be a driven wheel. Some wheels of the continuous track drive system 38 may not be support wheels as shown by 55 and 56. These wheels may be used to guide the track between the front and rear support wheels 37, 54 of the continuous track drive system 38. At least one of these non- support wheels of the continuous track drive system 38 may be a drive wheel of the continuous track drive system 38. The shunt device 36 may comprise more than one continuous track drive system 38, for instance the shunt device 36 may comprise a continuous track drive system 38 on each side of the shunt device body 48. These may be spaced apart from each other, as per the support wheels 2, 3 as described herein, to permit the shunt device 36 to receive a ground wheel there between. The continuous track drive system(s) 38 may improve the grip that the shunt device 1 has on the surface over using conventional wheels.

The second shunt device 36 may comprise other support wheels 49. These may not be part of a continuous track drive system. As shown by cross 50 in figure 4, the second rotation axis 50 within the roller 52 is located behind the first rotation centre 51 and can be situated in the locations as described herein with reference to shunt device 1 to give the same advantages.

As shown in figure 5, the shunt device 1 may comprise a skirt 57 that is configured to seal against the surface 42 that the support wheels 2, 24 are supporting the shunt device 1 against. The skirt 57 can seal against the surface 42 to define an area under the shunt device 1. The shunt device 1 may be configured to reduce the air pressure, relative to the air pressure outside of the skirt. The reduction in air pressure, in effect, presses the shunt device 1 on to the surface thus increasing the grip of the support wheels 2, 24 against the surface. The shunt device 1 may comprise an air pump 58, fan 58 and/or turbine 58 to remove air from under the skirt 57 to reduce the air pressure within the skirt 57.

The shunt devices described herein may be capable of operating in a number of different modes:

- In a first drive mode, the shunt device may be configured to control the operation of the drive wheels without drive control inputs external to the shunt device. In this mode, the shunt device may rely on sensors to navigate to a particular point on the surface. The sensors may assist the shunt device in avoiding objects in the motion path of the shunt device. The shunt device may have received a command from an external source to move to a particular location, but generates the drive commands locally to achieve the movement to the particular location.

- In a second drive mode, the shunt device may be configured to control the operation of the drive wheels in response to commands received from a user. The shunt device may communicate with the user, or rather a device controlled by the user, using transceiver 6. The shunt device may be completely responsive to those commands to control the operation of the drive wheels when in the second drive mode. Alternatively, the shunt device may receive general commands concerning the direction that the user wants the shunt device to drive in but also use sensing data received from one or more sensors to achieve that command. For instance, the user may command the shunt device to push the ground wheel forwards but may use sensing data received from the one or more sensors to ensure that correct contact between the roller and the ground wheel is maintained. In either case, the shunt device may be controlled by a user whilst the shunt device is pushing a ground wheel of a vehicle to cause the vehicle to move. Thus, the user can move the vehicle using the shunt device.

As shown in figure 6, more than one shunt device may be used at a time to move a vehicle. Figure 6 shows a schematic plan view of a vehicle, in this case an aircraft 60. The aircraft comprises three landing gears 61 , 62, 63. Each landing gear comprises at least one ground wheel. One of the landing gears is a front landing gear 61 positioned near the nose of the aircraft. Two of the landing gears are rear landing gears 62, 63 positioned on the wings 64 near where they join to the fuselage 65. Pictured in figure 6 are two shunt devices 66, 67 each positioned near the ground wheels of a respective one of the rear landing gears. The shunt devices 66, 67 can each push against their respective ground wheel(s) to move the aircraft 60. Steering of the aircraft 60 can be achieved by causing the shunt devices 66, 67 to push their respective ground wheels with a different amount of force thus applying a turning moment to the aircraft 60. It will be appreciated that a single shunt device could be used near the ground wheel(s) of the front landing gear. Alternatively, a shunt device could be used per landing gear. Whilst this description has referred to the vehicle being an aircraft other vehicles could be moved using the shunt device(s).

Figure 7 shows a third shunt device 70 as generally configured as described herein and in accordance with the present invention. In this case, roller 20 is positioned relative to the support wheel so that the second rotation axis within the roller is located on a first line 71 perpendicular to the shunt direction. The first line 71 passes through the first rotation centre 19 of the support wheel 3. The first line 71 is shown by cross 71 and runs through the page of figure 7. In this case, the second rotation axis of the roller 20 is generally collinear with the first line 71. The second rotation axis may not be collinear with the first rotation axis 19 in the case that the support wheel 3 has a non-zero camber and/or a toe in on its rotation axis 19. The support wheel(s) and roller may be generally configured as described herein. In particular, they may be connected to drive source(s) as described herein. The support wheel(s) 3 may be connected to roller 20 and to a drive source so that the drive source can drive the support wheel(s) 3 and the roller 20. The connection may mean that different torques can be applied to the roller relative to the support wheel(s). This may mean that the roller and wheel(s) rotate at speeds proportional to the force being delivered by the roller and wheel. The shunt device 70 may comprise a brake to limit the rotation of the roller 20 during periods when the shunt device 70 is not pushing a ground wheel 7 of a vehicle.

The shunt device 70 may otherwise be configured as herein described.

Figure 8 is a flow chart showing the steps of a method for a shunt device engaging with a ground wheel of a wheeled vehicle to push the ground wheel in a shunt direction. This method may be implemented by a shunt device 1 to push the ground wheel in a shunt direction. As described herein, the shunt device 1 may receive commands from a user that are interpreted by the shunt device 1 to cause the shunt device 1 to move. The shunt device 1 may also receive commands from other entities such as a shunt device controller that are interpreted by the shunt device to cause the shunt device 1 to move. The shunt device 1 may also use sensors that are part of the shunt device 1 to gather data about the shunt device's surroundings and move based on the data gathered about the shunt device's surroundings.

As shown in step 80, location data is received by the shunt device 1. This location data comprises a docking location for the shunt device 1. This docking location may specify a location area in which a ground wheel may be found for the shunt device 1 to engage with. The docking location may specify a location area that specifies an area in which the wheeled vehicle can be found. The docking location may specify a location area that specifies an area in which the ground wheel to be engaged with can be found. The location data may be sent to the shunt device 1 by a user. The location data may be sent to the shunt device 1 from the shunt device controller.

As shown in step 81 , based on the received location data, the shunt device 1 navigates to the docking location. The shunt device 1 may navigate to the docking location using positioning information received from at least one global positioning system. The shunt device may navigate to the docking location using positioning information received from a positioning system local to the area in which the shunt device navigates. This local positioning system may use an array of beacons to enable the shunt device to determine its position relative to those beacons. The shunt device may navigate based on a map of the area in which it navigates. It may use sensing data received from sensors to determine a path from its current location to the docking location. As shown in step 82, once the shunt device 1 has navigated to the docking location, the shunt device 1 detects a ground wheel at the docking location. The shunt device 1 may detect the ground wheel using sensors that are part of the shunt device 1. For example, these sensors may include proximity detectors, cameras, and physical contact sensors.

As shown in step 83, in response to detecting the position of the ground wheel, the shunt device engages with the ground wheel from behind the ground wheel in the shunt direction. This engagement may occur by the shunt device 1 moving from its initial position where the ground wheel was detected to a position where the roller of the shunt device 1 is in contact with the ground wheel.

As shown in step 84, once the shunt device 1 has engaged with the ground wheel, the sent device may push the ground wheel in the shunt direction. The pushing of the ground wheel may be in response to a push command received from the user. The push command may direct the shunt device 1 to push the ground wheel in a particular direction.

As shown in step 85, there may be a requirement to push the ground wheel in a direction opposite to the original shunt direction. In this case, the shunt device 1 needs to move to the opposite side of the ground wheel so that it can push the ground wheel in the opposite direction. The shunt device 1 may receive a reverse push command from the user and responsive to that reverse push command disengage with ground wheel and then engage with the ground wheel from behind the ground wheel in the opposite direction to the original shunt direction. The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. A shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising:

a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a first rotation centre on the first rotation axis within the first support wheel; and

a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located behind a first plane perpendicular to the shunt direction and that passes through the first rotation centre and between (i) a second plane generally parallel to the surface and coincident with the first rotation centre and (ii) the surface; wherein contact between the shunt device and the ground wheel is via the roller from behind the ground wheel in the shunt direction.

2. The shunt device according to claim 1 , wherein the first support wheel is a drive wheel.

3. The shunt device according to claim 1 or 2, the shunt device comprising a second support wheel configured to rotate about a third rotation axis so that the second support wheel has a second rotation centre on the third rotation axis within the second support wheel.

4. The shunt device according to claim 3, wherein the second support wheel is positioned so that the second rotation centre is on the first plane.

5. The shunt device according to claim 3 or 4, wherein the first rotation centre and second rotation centre are on a straight line perpendicular to the shunt direction.

6. The shunt device according to any of claims 3 to 5, the shunt device comprising a device body configured to receive the ground wheel between the support wheels to permit the roller to contact the ground wheel.

7. The shunt device according to any of claims 3 to 6, wherein the support wheels are spaced apart from each other so that the ground wheel can be positioned between them to permit the roller to contact the ground wheel.

8. The shunt device according to any of claims 3 to 7, wherein the first support wheel and second support wheel are drive wheels.

9. The shunt device according to any preceding claim, wherein the shunt device is configured so that contact between the shunt device and the ground wheel is only from behind the ground wheel in the shunt direction.

10. The shunt device according to any preceding claim, wherein the ground wheel is configured to rotate about a fourth rotation axis, and the roller is positioned relative to the support wheel(s) so that, when the roller contacts the ground wheel, a straight line that passes through the first and fourth rotation axes in a medial plane of a support wheel also passes through a projection of the roller on to the medial plane.

1 1. The shunt device according to claim 10, wherein the straight line also passes through the second rotation axis.

12. The shunt device according to any preceding claim, wherein the ground wheel is configured to rotate about a fourth rotation axis, and the roller is positioned relative to the support wheel(s) so that, when the roller contacts the ground wheel, a straight line passes through the first rotation centre, second rotation axis and fourth rotation axis at the points where the first rotation centre, second rotation axis and fourth rotation axis cut through a plane perpendicular to the first rotation centre.

13. The shunt device according to any preceding claim, wherein the ground wheel is configured to rotate about a fourth rotation axis, and the roller is positioned relative to the support wheel so that, when the roller contacts the ground wheel, the first rotation centre, second rotation axis and fourth rotation axis are substantially coplanar.

14. The shunt device according to any of claims 1 to 8, wherein the roller is positioned relative to the support wheel(s) so that the second rotation axis within the roller is located above a second plane generally parallel to the surface and coincident with the first rotation centre.

15. The shunt device according to any preceding claim, wherein the roller is free to rotate about the second rotation axis.

16. The shunt device according to any preceding claim, the shunt device comprising a first drive source; and wherein the first support wheel is coupled to the first drive source to cause the first support wheel to rotate about the first rotation axis to move the shunt device.

17. The shunt device according to claim 16 as dependent on claim 3, wherein the second support wheel is coupled to the first drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device.

18. The shunt device according to claim 16 as dependent on claim 3, the shunt device comprising a second drive source; and wherein the second support wheel is coupled to the second drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device.

19. The shunt device according to any of claims 16 to 18, wherein the roller is coupled to the first drive source to cause the roller to rotate about the second rotation axis.

20. The shunt device according to claim 19, wherein the support wheel(s) and the roller are coupled to the first drive source so that the support wheel(s) and the roller rotate at fixed relative angular speeds.

21. The shunt device according to claim 19, wherein the support wheel(s) and the roller are coupled to the first drive source so that the support wheel(s) and the roller rotate at variable relative angular speeds.

22. The shunt device according to any of claims 1 to 18, the shunt device comprising a third drive source; and wherein the roller is coupled to the third drive source so that the third drive source can cause the roller to rotate about the second rotation axis.

23. The shunt device according to claim 22 as dependent on claim 16, wherein the shunt device is configured to control the angular speeds of the first and third drive sources separately.

24. The shunt device according to claim 22 or 23 as dependent on claim 16, wherein the shunt device is configured to control the torque of the first and third drive sources separately.

25. The shunt device according to any of claims 16 to 24, the shunt device comprising a power source for the drive source(s).

26. The shunt device according to any of claims 16 to 25, wherein the drive source(s) and/or the power source are positioned on the shunt device behind the first rotation axis along the shunt direction.

27. The shunt device according to any of claims 16 to 26, wherein the drive source(s) are electric motors.

28. The shunt device according to any preceding claim, wherein the shunt device is configured to alter the position of the roller to move the second rotation axis in dependence on the size of the ground wheel.

29. The shunt device according to any preceding claim, the shunt device comprising one or more other support wheels configured to support the shunt device on a surface.

30. The shunt device according to claim 29, wherein the shunt device is configured to control the position of the one or more other support wheels to cause the shunt device to rotate about a vertical rotation axis.

31. The shunt device according to any preceding claim, wherein the shunt device is configured to control the rotation of the drive wheel(s) about the first rotation axis to cause the shunt device to rotate about a vertical rotation axis.

32. The shunt device according to any preceding claim, wherein the drive wheel supports the shunt device on a surface; the shunt device comprises a skirt configured to seal against the surface to define an area under the shunt device; and the shunt device is configured to reduce the air pressure in the area under the shunt device.

33. The shunt device according to any preceding claim, the shunt device comprising one or more sensors, the shunt device being configured to control the operation of the support wheel(s) in response to inputs from the one or more sensors.

34. The shunt device according to claim 33, wherein the one or more sensors detect the presence of objects in the motion path of the shunt device and the shunt device is configured to avoid the objects in response to their detection.

35. The shunt device according to any preceding claim, the shunt device being configured to operate in a first drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device without drive control inputs external to the shunt device.

36. The shunt device according to any preceding claim, the shunt device being configured to operate in a second drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device in response to commands received from a user.

37. The shunt device according to claim 36, wherein, when the shunt device is operating in the second drive mode, the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device in response to commands received from a user and from sensing data received from one or more sensors.

38. The shunt device according to any preceding claim, wherein the wheeled vehicle is an aeroplane, and the shunt device is configured to move the aeroplane by applying force to the ground wheel of the aeroplane.

39. A shunt device for moving a wheeled vehicle by applying force to a ground wheel of the vehicle, the shunt device comprising:

a first support wheel configured to support the shunt device on a surface and rotate about a first rotation axis so that the first support wheel has a rotation centre on the first rotation axis within the first support wheel;

a roller configured to rotate about a second rotation axis and contact the ground wheel to push the wheeled vehicle in a shunt direction, the roller being positioned relative to the support wheel so that the second rotation axis within the roller is located on a first line perpendicular to the shunt direction and that passes through the first rotation centre;

a first drive source, the first support wheel being coupled to the first drive source to cause the first support wheel to rotate about the first rotation axis to move the shunt device; and

a third drive source, the roller being coupled to the third drive source so that the third drive source can cause the roller to rotate about the second rotation axis;

wherein the shunt device is configured to control the angular speeds of the first and third drive sources separately.

40. The shunt device according to claim 39, wherein the first support wheel is a drive wheel.

41. The shunt device according to claim 39 or 40, the shunt device comprising a second support wheel configured to rotate about a third rotation axis so that the second support wheel has a second rotation centre on the third rotation axis within the second support wheel.

42. The shunt device according to claim 41 , wherein the second support wheel is positioned so that the second rotation centre is on the first line.

43. The shunt device according to claims 41 or 42, the shunt device comprising a device body configured to receive the ground wheel between the support wheels to permit the roller to contact the ground wheel.

44. The shunt device according to any of claims 41 to 43, wherein the support wheels are spaced apart from each other so that the ground wheel can be positioned between them to permit the roller to contact the ground wheel.

45. The shunt device according to any of claims 41 to 44, wherein the first support wheel and second support wheel are drive wheels.

46. The shunt device according to any of claims 39 to 45, wherein the roller is free to rotate about the second rotation axis.

47. The shunt device according to any of claims 39 to 46 as dependent on claim 41 , wherein the second support wheel is coupled to the first drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device.

48. The shunt device according to any of claims 39 to 46 as dependent on claim 41 , the shunt device comprising a second drive source; and wherein the second support wheel is coupled to the second drive source to cause the second support wheel to rotate about the third rotation axis to move the shunt device.

49. The shunt device according to any of claims 39 to 48, wherein the roller is coupled to the first drive source to cause the roller to rotate about the second rotation axis.

50. The shunt device according to claim 49, wherein the support wheel(s) and the roller are coupled to the first drive source so that the support wheel(s) and the roller rotate at variable relative angular speeds.

51. The shunt device according to any of claims 39 to 50, wherein the shunt device is configured to control the torque of the first and third drive sources separately.

52. The shunt device according to any of claims 39 to 51 , the shunt device comprising a power source for the drive source(s).

53. The shunt device according to any of claims 39 to 52, wherein the drive source(s) and/or the power source are positioned on the shunt device behind the first rotation axis along the shunt direction.

54. The shunt device according to any of claims 39 to 53, wherein the drive source(s) are electric motors.

55. The shunt device according to any of claims 39 to 54, wherein the shunt device is configured to alter the position of the roller to move the second rotation axis in dependence on the size of the ground wheel.

56. The shunt device according to any of claims 39 to 55, the shunt device comprising one or more other support wheels configured to support the shunt device on a surface.

57. The shunt device according to any of claims 39 to 56, wherein the shunt device is configured to control the position of the one or more other support wheels to cause the shunt device to rotate about a vertical rotation axis.

58. The shunt device according to any of claim 39 to 57, wherein the shunt device is configured to control the rotation of the drive wheel(s) about the first rotation axis to cause the shunt device to rotate about a vertical rotation axis.

59. The shunt device according to any of claims 39 to 58, wherein the drive wheel supports the shunt device on a surface; the shunt device comprises a skirt configured to seal against the surface to define an area under the shunt device; and the shunt device is configured to reduce the air pressure in the area under the shunt device.

60. The shunt device according to any of claims 39 to 59, the shunt device comprising one or more sensors, the shunt device being configured to control the operation of the support wheel(s) in response to inputs from the one or more sensors.

61. The shunt device according to claim 60, wherein the one or more sensors detect the presence of objects in the motion path of the shunt device and the shunt device is configured to avoid the objects in response to their detection.

62. The shunt device according to any of claims 39 to 61 , the shunt device being configured to operate in a first drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device without drive control inputs external to the shunt device.

63. The shunt device according to any of claims 39 to 62, the shunt device being configured to operate in a second drive mode where the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device in response to commands received from a user.

64. The shunt device according to claim 63, wherein, when the shunt device is operating in the second drive mode, the shunt device controls the operation of at least one drive wheel of the shunt device to drive the shunt device in response to commands received from a user and from sensing data received from one or more sensors.

65. The shunt device according to any of claims 39 to 64, wherein the wheeled vehicle is an aeroplane, and the shunt device is configured to move the aeroplane by applying force to the ground wheel of the aeroplane.

66. A method for a shunt device engaging with a ground wheel of a wheeled vehicle to push the ground wheel in a shunt direction, the method comprising:

receiving location data comprising a docking location;

navigating to the docking location;

detecting the ground wheel at the docking location; and

engaging with the ground wheel, based on the detection of the ground wheel, from behind the ground wheel in the shunt direction.

67. A method as claimed in claim 66, the method comprising pushing the ground wheel in the shunt direction after engaging with the ground wheel.

68. A method as claimed in claim 66 or 67, the method comprising: receiving a push command from a user to push the shunt device in the shunt direction; and

in response to the push command, pushing the ground wheel in the shunt direction after engaging with the ground wheel.

69. A method as claimed in any of claims 66 to 68, the method comprising:

receiving a reverse push command from a user to push the shunt device in the opposite direction to the original shunt direction;

in response to the reverse push command, disengaging with the ground wheel and engaging with the ground wheel from behind the ground wheel in the opposite direction to the original shunt direction.

70. A method as claimed in any of claims 66 to 69, wherein the docking location specifies a location area for the wheeled vehicle.

71. A method as claimed in any of claims 66 to 70, wherein the docking location specifies a location area for the ground wheel.