Technical Field

The present invention relates to a vehicle and particularly, but not exclusively, to a robotic vehicle capable of climbing obstacles such as stairs or the like. The present invention may find application as an autonomous robot, for example, a domestic autonomous robot.

Background

Human environments present unique challenges for robotic vehicles. These environments are designed for navigation by human beings; however, human beings are extremely complex biological entities that are difficult to replicate with robots. For example, it has long been a desire to provide robotic vehicles that can manoeuvre within an environment, such as a home, to help with certain tasks. However, certain environments have discontinuous surfaces like stairs and steps that require climbing, which can cause many robotic vehicles problems during navigation. This is often the case for even single floor homes, as small level changes between rooms are common.

Stair climbing robotic vehicles are known For example, TW201132328 describes a complex robotic vehicle having a large number of components to enable the vehicle to perform a stair climbing operation. For example, the vehicle described in TW201132328 requires five wheels and two supporting structures to support and balance the vehicle during the climbing operation. Having a large number of components directed to stair climbing renders the robotic vehicle more prone to failure, adds weight and increases cost.

Summary

According to a first aspect of the present invention there is provided a vehicle comprising a body and at least a first wheel and a second wheel to support motion of the body across a surface. The first wheel is operable as a leading wheel relative to the body during a climbing operation, and is coupled to the body via a first coupling arrangement that is actuable to move the first wheel between a first position, in which the first wheel is in contact with the surface to support motion of the body across the surface, and an elevated position, in which the wheel extends in front of the body above the surface. The second wheel is operable as a trailing wheel relative to the body and to the first wheel during the climbing operation, and is coupled to the body via a second coupling arrangement. The second coupling arrangement is actuable to: (i) move the second wheel between a first trailing position and a second trailing position, the first trailing position being behind the second trailing position relative to the body during the climbing operation, and wherein the first and second trailing positions are behind the first wheel, and (ii) drive the second wheel downwardly away from the body, thereby to lift the body relative to the surface. The vehicle further comprises a propulsion system to drive motion of the body across the surface and to actuate the first coupling arrangement and the second coupling arrangement.

The vehicle therefore has a body and a first wheel extending in front of the body, and a second wheel arranged behind the first wheel. As the vehicle moves towards a step or staircase that is in front of the vehicle, the first wheel can move between a first position in which the first wheel is in contact with a surface, such as the ground, and a raised or elevated position which is above the surface. The first coupling arrangement therefore allows the first wheel to be moved: (i) away from the surface in an upwards direction (i. e. “upwardly”), and (ii) towards the surface in a downwards direction (i. e. “downwardly”). In a particular example, the first coupling arrangement moves the first wheel substantially vertically, along a first axis.

The second wheel can move between a first trailing position and a second trailing position. The first trailing position is behind the second trailing position, so may be further away from the front of the vehicle (and/or the first wheel) in the first trailing position than in the second trailing position. The second coupling arrangement therefore allows the second wheel to moved: (i) towards the front of the body/vehicle (and/or the first wheel) in a forward direction, and (ii) towards the rear of the body/vehicle in a backward direction. This motion may be linear, along a second axis perpendicular to the first axis, or may be non-linear such as along an arc. As will become apparent, the movement between the first and second trailing positions allows the second wheel to move onto a step after body has been lifted onto the step. In addition, this allows the vehicle to have a smaller overall footprint, so that it can fit on a staircase without needing to reduce the size of the body to compensate for the area occupied by the first and second wheels.

The second wheel can also move away from the body to lift the body away from the surface. For example, the second coupling arrangement also allows the second wheel to be moved (i) away from the body in a downward direction, and (ii) towards the body in an upward direction. When the second wheel is in contact with the surface and the second coupling arrangement moves the second wheel downwardly away from the body, a downwards force is applied to the surface, which causes the vehicle to be pushed away from the surface in the upward direction, thereby lifting the vehicle relative to the surface. This allows the body to be raised, onto a step, for example.

The propulsion system causes the vehicle to move relative to the surface, as well as control at least the first and second coupling arrangements. The propulsion system may comprise one or more motors, and/or one or more gears to enable the actuation of the first and second coupling arrangements.

Accordingly, the example vehicle has relatively few components which provide a simple and less complex vehicle compared to existing robotic vehicles.

“A leading wheel” may mean that the wheel is arranged at or closer towards the front of the body when compared to other wheels. Thus, as the body moves across the surface towards a step or staircase, the leading wheel may approach the step or staircase first.

“A trailing wheel” may mean that the wheel is arranged further away from the front of the body than the leading wheel. Thus, as the body moves across the surface towards a step or staircase, the trailing wheel may be positioned further away from the step or staircase than the leading wheel. The trailing wheel may be arranged at or towards the rear of the body, in some examples.

“The front of the body” may be the most forward part of the body as the vehicle approaches a step or staircase.

“The rear of the body” may be the back part of the body as the vehicle approaches a step or staircase.

“Downwardly” means a direction towards the surface, such as the ground, and may be substantially parallel to the direction of the gravitational force acting on the body. Downwardly may also be known as a “downward direction”.

“Upwardly” means a direction away from the surface. Upwardly may also be known as a “upward direction”.

“A climbing operation” is a process in which the vehicle moves from a lower surface to a higher surface, where the two surfaces are separated in elevation. This may involve navigating or climbing one or more steps or stairs. In a particular example, the height of a step or stair is measured along the first axis, and the depth of a step or stair is measured along the second axis, perpendicular to the first axis. A staircase may extend along the first axis and the second axis. The climbing operation may be a stair climbing operation. “Supporting motion of the body across a surface” means that the wheel is capable of being in contact with a surface to help move the vehicle along the surface. Not all wheels may be in contact with a surface at the same time.

“Extending in front of the body” may mean that the first wheel extends outwards away from the body.

The first coupling arrangement couples/connects the first wheel to the body. Similarly, the second coupling arrangement couples/connects the second wheel to the body. The coupling may be direct or indirect. The same can be said of any coupling arrangement described herein.

In one example, the vehicle is a robotic vehicle. In another example, the vehicle is a stair climbing robot or a stair climbing vehicle. The vehicle may be a stair climbing robot for performing one or more tasks. The tasks may be domestic tasks, such as cleaning or vacuuming.

The propulsion system may drive at least one wheel such that the vehicle moves across the surface. In certain examples, the propulsion system is configured to control at least one of the first wheel and the second wheel to drive motion of the body across the surface. The propulsion system may comprise one or more motors and/or one or more gears to drive/control the wheel(s). The propulsion system may comprise a controller to control operation of the vehicle. The controller may comprise one or more processors, including one or more microprocessors, central processing units and/or graphical processing units, and a set of memory.

The second coupling arrangement may pivotably couple the second wheel to the body. Thus, as mentioned, the motion of the second wheel may be non-linear as it moves between the first and second trailing positions. In this case, the second wheel may be moveable at least partially around the body. The second wheel may therefore move in an azimuthal direction around the body. This pivoting motion can allow the vehicle to be more compact and lower in profile. For example, the second wheel may not need to be arranged underneath the body, and may instead be arranged away from the body. The pivoting motion can allow the second wheel to move towards the front of the body, without necessarily moving beneath the body.

In one arrangement, the first and second wheels may be holonomic wheels. Holonomic wheels allow the vehicle to travel more easily in two-dimensions across the surface. It may be particularly useful for the second wheel to be holonomic when the second coupling arrangement pivotably couples the second wheel to the body because the non-linear movement of the second wheel may be more easily achieved with a holonomic wheel. In a preferred arrangement, the vehicle may comprise a third wheel, the third wheel may be operable as a second trailing wheel relative to the body and to the first wheel during the climbing operation. The third wheel may be coupled to the body via a third coupling arrangement, that may be actuable to: (i) move the third wheel between a first trailing position and a second trailing position, the first trailing position being behind the second trailing position relative to the body during the climbing operation, and wherein the first and second trailing positions are behind the first wheel, and (ii) drive the third wheel downwardly away from the body, thereby to lift the body relative to the surface. The third wheel and the third coupling arrangement may therefore operate in the same way as the second wheel and second coupling arrangement. Accordingly, there may be two trailing/rear wheels. In one example, the first, second and third wheels are arranged in a triangular formation around the body. By having at least three wheels, the vehicle can be better stabilised.

The propulsion system may also be configured to actuate the third coupling arrangement. The propulsion system may be configured to control at least one of the first wheel, the second wheel and the third wheel to drive motion of the body across the surface. In one example, the third coupling arrangement pivotably couples the third wheel to the body. The third wheel may be a holonomic wheel.

During the climbing operation, the vehicle may be configured to climb to a second surface elevated above the surface, and the propulsion system is configured to: actuate the first coupling arrangement to move the first wheel from the first position to the elevated position, the elevated position being at a height above the second surface; drive motion of the body across the surface until the first wheel is above the second surface; actuate the second and third coupling arrangements to drive the second and third wheels downwardly away from the body, thereby to lift the body relative to the surface to a height above the second surface; drive motion of the body across the surface until the body is above the second surface; actuate the second and third coupling arrangements to move the second and third wheels upwardly towards the body; and actuate the second and third coupling arrangements to move the second and third wheels from the first trailing position to the second trailing position such that the second and third wheels are in contact with the second surface. The second surface therefore forms part of a first step or stair. The surface may be a first surface. There may be further steps or stairs, and therefore further surfaces elevated above the second surface.

“A height above the second surface” means that the part (such as the first wheel or body) is moved to a height that is equal to or greater than the height of the second surface. This allows the first wheel or body to be raised/lifted to a height that clears the second surface. Accordingly, when the vehicle moves across the surface towards the step, the first wheel or body is above the second surface. “Is above the second surface” means that the part (such as the first wheel or body) is either higher than the second surface or is in contact with the second surface.

Moving the second and third wheels downwardly away from the body causes the second and third wheels to extend away from the body. Similarly, moving the second and third wheels upwardly towards the body causes the second and third wheels to retract towards the body. Moving the second and third wheels upwardly towards the body moves the second and third wheels away from the surface, and may include moving the second a third wheels to a height above the second surface. The action of moving the second and third wheels upwardly may mean that the body is brought into contact with the second surface because the second and third wheels are no longer in contact with the surface, and no longer support the body.

Once retracted towards the body, the second and third wheels may overhang the first step (and not be in contact with either surface). Accordingly, actuating the second and third coupling arrangements to move the second and third wheels from the first trailing position to the second trailing position brings the second third wheels above the second surface.

When the propulsion system drives motion of the body across the surface to the point that the body is above the second surface, the second and third wheels are still in contact with the surface (and are still in the extended position).

The above therefore describes how the vehicle efficiently moves from one surface to an elevated surface.

In a particular configuration, as the propulsion system actuates the second and third coupling arrangements to drive the second and third wheels downwardly away from the body, the propulsion system may be further configured to actuate the first coupling arrangement to keep the first wheel in contact with the second surface. Thus, the first coupling arrangement is actuated to move the first wheel downwardly (relative to the body, as the body is lifted upwards) so that the first wheel remains in contact with the second surface as the body is lifted. This provides support for the vehicle, and stops the vehicle from tilting, as the body is lifted. The body may therefore remain substantially level (parallel to the surface).

In one example, after driving motion of the body across the surface until the body is above the second surface, the propulsion system may be further configured to actuate the first coupling arrangement to move the first wheel to the elevated position, the elevated position being at a height above a third surface elevated above the second surface. This is useful if there is a second step (comprising the third surface) to ensure that the first wheel does not cause an obstruction as the body is moved further onto the second surface. By moving the first wheel into this elevated position, the body may fit on the first step. This is particularly useful if the depth of the first step cannot accommodate the body and the first wheel when in the first position (i.e. when in the non elevated position).

In a particular example, after actuating the first coupling arrangement to move the first wheel to the height above the third surface, the propulsion system may be further configured to drive motion of the body across the second surface until the first wheel is above the third surface. This allows the body to move further onto the second surface. Accordingly, in this configuration, the vehicle spans three surfaces (the ground surface, the first step, and the second step). For example, in this configuration the second and third wheels are in contact with the first surface, the body is in contact with the second surface, and first wheel is above the third surface. Once in this position, the propulsion mechanism proceeds to actuate the second and third coupling arrangements to move the second and third wheels upwardly towards the body.

In one example, after actuating the second and third coupling arrangements to move the second and third wheels from the first trailing position to the second trailing position, the propulsion system may be further configured to actuate the second and third coupling arrangements to move the second and third wheels from the second trailing position to the first trailing position and drive motion of the body across the second surface. These steps may occur in any order, and may occur simultaneously. This means that the first and second wheels can be moved back to their original position so that the body can be adequately positioned on top of the third surface. In a particular example, moving the wheels back to the first trailing position occurs once the second and third wheels have been moved away from the body (i.e. the body has been lifted above the third surface). Alternatively, moving the wheels back to the first trailing position occurs as the second and third wheels are been moved away from the body. If the stair tread is particularly narrow, the vehicle may first lift the body above the third surface (to ensure clearance), then move across the second surface, and finally move the wheels back towards the first trailing position. This particular sequence allows the wheels to be accommodated by the second surface while in the first trailing position.

The first coupling arrangement may comprise an actuator, such as a linear actuator. A linear actuator, for example, is a simple and effective mechanism to move the first wheel along an axis. In another example, the first coupling arrangement may comprise an actuator and an arm, where the actuator is configured to cause the arm to pivot and thereby move the first wheel between the first position and the elevated position. In this example, the front wheel may not move linearly along an axis.

The second coupling arrangement may comprise: a first part pivotably coupled to the body so as to move the second wheel at least partially around the body, and a second part coupled to: (i) the first part, and (ii) the second wheel, where the second part is telescopic/retractable/extendable to move the second wheel away from and towards the body. This mechanism therefore allows the second coupling arrangement to move the wheel in two or more dimensions. Preferably, the third coupling arrangement operates in the same way as the second coupling arrangement. In one example, the first part is moveable around the body via a rotary actuator and the second part is moveable relative to the first part via a linear actuator.

As mentioned, in one example, the vehicle may comprise three wheels. For example, a first wheel operable as a leading wheel, and two further wheels operating as trailing wheels. In another example, the vehicle may comprise more than three wheels. For example, the vehicle may comprise four wheels; two wheels operable as a leading wheel, and two wheels operating as trailing wheels. The additional leading wheel may operate in substantially the same way as the above-described leading wheel.

According to a second aspect of the present invention, there is provided a method of controlling a vehicle during a climbing operation in which the vehicle is configured to climb from a first surface to a second surface elevated above the first surface. The vehicle comprises a body, a first wheel coupled to the body, and a second wheel coupled to the body. The method comprises: moving the first wheel from a first position in which the first wheel supports motion of the body across the first surface, to an elevated position in which the wheel extends in front of the body above the first surface; moving the body across the first surface until the first wheel is equal to or above the second surface; moving the second wheel away from the body so as to lift the body relative to the first surface to a height equal to or above the second surface; moving the body across the first surface until the body is equal to above the second surface; moving the second wheel towards the body; and moving the second wheel from a first trailing position to a second trailing position such that the second wheel is in contact with the second surface, wherein: the first trailing position is behind the second trailing position relative to the body during the climbing operation; and the first and second trailing positions are behind the first wheel.

“Moving the second wheel from a first trailing position to a second trailing position” may comprise “moving the second wheel at least partially around the body”.

In one example, the vehicle may further comprise a third wheel coupled to the body, and the method further comprises: moving the third wheel away from the body so as to lift the body relative to the first surface to a height above the second surface; moving the third wheel towards the body; and moving the third wheel from a first trailing position to a second trailing position such that the third wheel is in contact with the second surface.

These actions may occur substantially simultaneously as with the actions performed for the second wheel.

“Moving the second wheel from the first trailing position to the second trailing position” may comprise pivoting the second wheel at least partially around the body. Similarly, in examples comprising a third wheel, “moving the third wheel from the first trailing position to the second trailing position” may comprise pivoting the third wheel at least partially around the body.

In one example method, while moving the second wheel away from the body, the method further comprises keeping the first wheel in contact with the second surface. These actions may therefore occur substantially simultaneously, so that the vehicle remains balanced as it is lifted.

In one example, after moving the body across the first surface until the body is above the second surface, the method may further comprise moving the first wheel to the elevated position, the elevated position being at a height above a third surface elevated above the second surface. In one example, after moving the second and third wheels from the first trailing position to the second trailing position, the method may further comprise moving the second and third wheels from the second trailing position to the first trailing position; and moving the body across the second surface.

In one example, moving the body across the first surface until the body is on or above the second surface may cause the first wheel to be positioned equal to or above a third surface.

In some examples, the first wheel may be coupled to the body via a first coupling arrangement and the second wheel may be coupled to the body via a second coupling arrangement. In examples comprising a third wheel, the third wheel may be coupled to the body via a third coupling arrangement. Thus, moving the first, second or third wheels may comprise controlling the first, second or third coupling arrangements respectively.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 A is a perspective view of a robotic vehicle having a leading wheel and two trailing wheels according to an example;

Figure IB is a perspective side view of the robotic vehicle of Figure 1A with the two trailing wheels arranged in a first trailing position, and the leading wheel arranged in a first position;

Figure 1 C is a perspective side view of the robotic vehicle of Figure IB with the two trailing wheels arranged in a second trailing position, and the leading wheel arranged in the first position;

Figure 2A is a schematic diagram showing a side view of the vehicle of Figure IB before climbing one or more stairs;

Figure 2B is a schematic diagram showing a top-down view of the vehicle of Figure 2A, where the two trailing wheels are arranged in a first trailing position;

Figure 3 is a schematic diagram of the vehicle of Figure 2B where the leading wheel is arranged in a second, elevated position;

Figure 4 is a schematic diagram of the vehicle of Figure 3 after the vehicle has moved towards a first step; Figure 5 is a schematic diagram of the vehicle of Figure 4 after the two trailing wheels have moved away from the body and the vehicle has been lifted;

Figure 6 is a schematic diagram of the vehicle of Figure 5 after the vehicle has moved onto the first step;

Figure 7 is a schematic diagram of the vehicle of Figure 6 where the leading wheel is again arranged in the second, elevated position;

Figure 8 is a schematic diagram of the vehicle of Figure 7 after the vehicle has moved further onto the first step and the leading wheel has moved onto a second step;

Figure 9 is a schematic diagram of the vehicle of Figure 8 after the two trailing wheels have been retracted towards the body;

Figure 10A is a schematic diagram of the vehicle of Figure 9 after the trailing wheels have moved into the second trailing position;

Figure 10B is a schematic diagram showing a top-down view of the vehicle of Figure 10A;

Figure 11 is a schematic diagram of the vehicle of Figure 10A after the trailing wheels have moved away from the body and the vehicle has moved onto the second step;

Figure 12 is a schematic diagram of another example vehicle; and

Figure 13 is a flow diagram showing a method of controlling a vehicle during a climbing operation according to an example.

Examples of the invention relate to an autonomous domestic robot or robotic vehicle that is capable of climbing stairs. Such a robot may be configured to vacuum floors and the stair climbing may be to move between floors in a dwelling to facilitate cleaning of different floors that are separated by stairs. In other examples, the robot may be configured to vacuum or clean the stairs during a stair-climbing operation. Needless to say, the same configuration of vehicle may find application in many other areas, such as commercial or military robots designed to climb stairs or other obstacles. Indeed, the same climbing approach may find application in human-driven vehicles. In any event, a vehicle capable of climbing stairs or the like will now be described, by way of example.

Figure 1A is a perspective view of a vehicle 100. In this example, the vehicle 100 is a robotic stair climbing vehicle. The vehicle 100 has a body 102, a first wheel 104 operating as a leading wheel, a second wheel 106 operating as a first trailing wheel, and a third wheel 108 operating as a second trailing wheel. The central body 102 is generally cylindrical in this example, but may take any other shape or form. The body 102 may house one or more components, including a propulsion system to drive motion of the body across a surface.

The vehicle 100 further comprises a first coupling arrangement 110, which connects the first wheel 104 to the body 102. The propulsion system controls movement of the first wheel 104 by actuating the first coupling arrangement 110. In this example, the first wheel 104 can be moved vertically along a first axis 112 from the first position shown in Figure 1 A, to a second or elevated position (shown in Figure 3). In the first position, the first wheel 104 is in contact with a surface such as a floor and can operate as a wheel to help support motion of the vehicle 100 across the floor. The first coupling arrangement 110 can therefore lift the first wheel 104 off the floor, by moving the first wheel 104 in an upwards direction 114 along the first axis 112. Similarly, the first coupling arrangement 110 can return the first wheel 104 towards the floor (or another surface) by moving the first wheel 104 in a downwards direction 116 along the first axis 112.

The vehicle 100 further comprises a second coupling arrangement 118, which connects the second wheel 106 to the body 102. The propulsion system controls movement of the second wheel 106 by actuating the second coupling arrangement 118. In this example, the second coupling arrangement 118 pivotably couples the second wheel 106 to the body 102. This allows the second wheel 106 to move azimuthally around the body 102 from a first trailing position shown in Figures 1A and IB to a second trailing position shown in Figure 1C. In this example, the second wheel 106 pivots around a midpoint 120 of the central body, although it will be appreciated different pivoting or rotational mechanisms can be implemented.

In at least Figures 1A and IB, the second wheel 106 is in contact with the floor, so can operate as a wheel to help support motion of the vehicle 100 across a floor.

Figure fB shows a side view of the vehicle 100 and more clearly shows the third wheel 108 and a third coupling arrangement 122 which connects the third wheel 108 to the body 102. As with the second coupling arrangement 118, the propulsion system controls movement of the third wheel 108 by actuating the third coupling arrangement 122. In this example, the third coupling arrangement 122 pivotably couples the third wheel 108 to the body 102. This allows the third wheel 108 to move azimuthally around the body 102 from a first trailing position shown in Figure 1A and IB, to a second trailing position shown in Figure 1C. As with the second wheel 106, the third wheel 108 pivots around a midpoint 120 of the central body. Figure 1C depicts the second and third wheels 106, 108 arranged in the second trailing position. The position of the second and third wheels 106, 108 in the second trailing position is further forward (relative to the body 102 and first wheel 104) than in the first trailing position. This means that the position of the second and third wheels 106, 108 in the first trailing position is behind the second trailing position (relative to the body 102 and first wheel 104). The movement of the second and third wheels 106, 108 therefore moves the wheels closer to the front of the vehicle 100.

Figures 2A to 10B depict the vehicle 100 at various stages of a stair climbing operation. An example implementation of the vehicle 100 will now be described.

Figure 2A depicts the stair climbing vehicle 100 arranged on a first surface 124, for example the ground floor of a dwelling. In front of the vehicle 100 is a staircase, comprising at least a first step. The first step comprises a second surface 126, or stair tread 126, elevated above the floor 124 by a single stair height/di stance 130. As the vehicle 100 approaches the staircase, by moving in a forwards direction 132 along a second axis 134 (which is perpendicular to the first, vertical axis 112), the first wheel 104 is said to be a leading wheel, as it reaches the first step before the second and third wheels 106, 108. It should be noted that in Figure 2A the third wheel 108 is obscured from view by the second wheel 106 and that the motion of the third wheel 108 mirrors that of the second wheel 106. The second and third wheels 106, 108 are therefore trailing wheels because they are behind the first wheel during the stair climbing operation. In Figure 2A, the first wheel 104 is in contact with the floor 124, and is arranged in a lowered, or first position. All three wheels 104, 106, 106 are therefore in contact with the floor 124 and support motion of the body 102 across the floor 124.

In Figure 2A, the second and third wheels 106, 108 are arranged in a first trailing position. Figure 2B depicts a top-down view of the vehicle. The solid lines show the second and third wheels 106, 108 arranged in this first trailing position. The dashed lines show the position of the second and third wheels 106, 108 once they have moved forwards into the second trailing position. As can be seen, the first trailing position is behind the second trailing position relative to the body 102, and both the first and second trailing positions are behind the first wheel 104. In other words, the second and third wheels 106, 108 in the first trailing position are further away from the stair, the front of the vehicle and the first wheel 104 than in the second trailing position. The front of the vehicle is the most forward part of the body as the vehicle approaches the staircase. In this example, the propulsion system drives one or more of the wheels 104, 106, 108 to move the vehicle in the forward direction 132 towards the stairs. In other examples, one or more other wheels, or other driving components may instead drive motion of the body across the surface. The propulsion system also controls the first, second and third coupling arrangements 110, 118, 122 to move the wheels 104, 106, 108 relative to the body 102, as will now be described.

Figure 3 depicts the stair climbing vehicle 100 at a time later than that in Figure 2A. Here, the first wheel 104 is arranged in an elevated position. In this elevated position, the first wheel 104 is equal to or above the height 130 of the first step. In some examples, the propulsion system causes the first wheel 104 to move to a height based on a height 130 of the step determined by one or more sensors located on the vehicle 100.

As shown in the example in Figure 3, the second and third wheels 106, 108 remain in contact with the floor 124 and remain in the first trailing position.

Figure 4 depicts the stair climbing vehicle 100 at a time later than that in Figure 3. Here, the vehicle 100 has moved across the floor 124 such that the first wheel 104 is now equal to or above the stair tread 126. In some examples, the vehicle 100 to moves in the forwards direction 132 until the body 102 contacts the first step, or until the body 102 is positioned at a predetermined distance away from the first step. For example, the vehicle 100 may comprise one or more sensors used to determine the location of the vehicle 100 relative to the first step.

Figure 5 depicts the stair climbing vehicle 100 at a time later than that in Figure 4. Here, the body 102 has been lifted to equal to or above the height 130 of the first step by moving the second and third wheels 106, 108 in the downwards direction 116 relative to the body 102. In doing so, the second and third wheels 106, 108 are urged against the floor 124 and remain in contact with the floor 124 as the body is lifted in the upwards direction 114. Simultaneously, the first wheel 104 is controlled to keep the first wheel 104 in contact with the stair tread 126. This stops the vehicle 100 from becoming unbalanced.

As shown, the second coupling arrangement 118 comprises two main components: a first part 118a coupled to the body, and a second part 118b coupled to the first part 118a at one end and the second wheel 106 at the other end. The second part 118b is telescopic and can be extended to move the body 102 away from the second wheel 106. Similarly, the second part 118b can be retracted to move the second wheel 106 towards the body 102. In this particular example, the first part 118a pivotably couples the second wheel 106 to the body 102 to allow the second wheel 106 to move azimuthally around the body. For example, the first part 118a may be pivotably connected to the midpoint 120 (shown in Figure 1 A), and may slide around the body 102 along a guide track. Although not shown, the third coupling arrangement 118 may also comprise a first part and a second part and may operate in substantially the same way.

Figure 6 depicts the stair climbing vehicle 100 at a time later than that in Figure 5. Here, the vehicle 100 has moved to a position in which the body 102 is equal to or above the stair tread 126. The body 102 may or may not be in contact with the stair tread 126 at this point.

In some circumstances (particularly in this example where there are further steps, and the depth 136 of the current step is shorter than the overall length of the vehicle 100), the first wheel 104 needs to be moved to an elevated position to ensure that the vehicle 100 can be accommodated by the step. Accordingly, Figure 7 depicts an optional step in which the first wheel 104 is moved out of the way before the second and third wheels 106, 108 are retracted back towards the body.

Figure 7 therefore depicts the stair climbing vehicle 100 at a time later than that in Figure 6. Here, the first wheel 104 has been moved to an elevated position, while the second and third wheels 106, 108 remain in contact with the floor 124. In this elevated position, the first wheel 104 is at a height equal to or above a height 138 of the second step. The second step comprises a third surface 128, also referred to as a second stair tread 128.

Figure 8 depicts the stair climbing vehicle 100 at a time later than that in Figure 7. Here, the vehicle 100 has been moved to a position in which the first wheel 104 is equal to or above the second stair tread 128. In this position, the vehicle 100 spans three surfaces 124, 126, 128 and the vehicle 100 is arranged in a particularly stable configuration during its climbing operation.

Figure 9 depicts the stair climbing vehicle 100 at a time later than that in Figure 8. Here, the second and third wheels 106, 108 have been moved upwardly, towards the body 102 and away from the floor 124, to a height equal to or above the height 130 of the first step. To achieve this, the second part 118b of the second coupling arrangement 118 is retracted to move the second wheel 106 towards the body 102. Similarly, the second part of the third coupling arrangement 122 is retracted to move the third wheel 108 towards the body 102. At this point, both the second and third wheels 106, 108 overhang the first step, and are not yet in contact with the stair tread 126. They are also still positioned in the first trailing position. As will be appreciated, as long as the centre of gravity of the vehicle 100 is above the stair tread 126, the second and third wheels 106, 108 can be moved upwardly without the vehicle 100 falling backwards.

Figure 10A depicts the stair climbing vehicle 100 at a time later than that in Figure 9. Here, the second and third wheels 106, 108 have been moved from the first trailing position to the second trailing position such that the second and third wheels 106, 108 are in contact with the stair tread 126. To achieve this, the first part 118a of the second coupling arrangement 118 pivots with respect to the body 102 so as to move the second wheel 106 around the body 102. Similarly, the first part of the third coupling arrangement 122 pivots with respect to the body 102 so as to move the third wheel 108 around the body 102. In some examples, bringing the wheels 106, 108 into contact with the stair tread 126 also comprises moving the second and third wheels 106, 108 in the downwards direction 116 once in the second trailing position. Figure 10B depicts a top-down view of the vehicle 100 shown in Figure 10B. The solid lines show the second and third wheels 106, 108 arranged in this second trailing position.

The vehicle 100 has therefore successfully performed a climbing operation in which it has climbed a first step. From here, the vehicle 100 can continue to climb the second and further steps in the staircase, by substantially repeating the previously described actions. In Figure 10A, in contrast to Figures 4 and 5, the second and third wheels 106, 108 may be arranged in the second trailing position when the second and third coupling arrangements 118, 122 are actuated again to drive the second and third wheels 106, 108 downwardly to lift the body 102 due to the limited depth of the first step. Thus, in some examples, after the body 102 has been lifted upwards, and is driven forwards to a position partially above the second stair tread 128, the second and third wheels 106, 108 may move at least partially towards the first trailing position while in their extended state to ensure that the body 102 can be positioned adequately above the second stair tread 128. For example, Figure 11 depicts the second and third wheels having moved at least partially towards the first trailing position while extended. Figure 11 shows the vehicle 100 in motion as it moves along the stair tread 126.

As described, the vehicle 100 comprises second and third coupling arrangements that move the second and third wheels around the body of the vehicle. Figure 12 depicts an alternative vehicle 200 according to another example. The vehicle 200 differs from the example vehicle described in Figures 1A to 10B in that the second and third coupling arrangements move the second and third wheels linearly relative to the body. The vehicle 200 therefore comprises a body 202, a first wheel 204 operating as a leading wheel, a second wheel 206 operating as a first trailing wheel, and a third wheel 208 operating as a second trailing wheel. The central body 202 is generally rectangular in this example, but may take any other shape or form.

The vehicle 200 comprises a first coupling arrangement 210 which connects the first wheel 204 to the body 202. The propulsion system controls movement of the first wheel 204 by actuating the first coupling arrangement 210. The first coupling arrangement 210 may operate in substantially the same way as the first coupling arrangement 110 described in relation to Figures 1A to 10B.

The vehicle 200 further comprises a second coupling arrangement 218 which connects the second wheel 206 to the body 202. The propulsion system controls movement of the second wheel 206 by actuating the second coupling arrangement 218. In this example, the second coupling arrangement 218 couples the second wheel 206 to the body 202 and moves the second wheel 206 linearly with respect to the body 202 from a first trailing position (shown with solid lines), to a second trailing position (shown with dashed lines). In this example, the second coupling arrangement 218 moves the second wheel 206 underneath the body 202 in the forwards direction 232. This linear movement also allows the second and third wheels 106, 108 to come into contact with a surface of a step as the vehicle climbs a staircase.

Figure 12 is a flow diagram showing a method of controlling a vehicle during a climbing operation according to an example. The method may be a method for performing a stair climbing operation as described in Figures 1A to 10B, and may be performed by vehicles 100, 200. The method may be implemented by a propulsion system for example.

In block 902, the method comprises controlling the first coupling arrangement 110, 210 to move the first wheel 104, 204 from a first position in which the first wheel supports motion of the body 102, 202 across the floor 124, to an elevated position in which the first wheel extends in front of the body above the floor. At block 904, the method comprises moving the body across the floor until the first wheel is above the stair tread 126. At block 906, the method comprises controlling the second coupling arrangement 118, 218 to drive the second wheel 106, 206 away from the body so as to lift the body relative to the floor to a height above the stair tread. At block 908 the method comprises moving the body across the floor until the body is above the stair tread. At block 910, the method comprises controlling the second coupling arrangement to move the second wheel towards the body. At block 912, the method comprises controlling the second coupling arrangement to move the second wheel from a first trailing position to a second trailing position such that the second wheel is in contact with the stair tread. Block 906 may further comprise controlling the third coupling arrangement 122, 222 to drive the third wheel 108, 208 away from the body so as to lift the body relative to the floor to a height above the stair tread. Block 910 may further comprise controlling the third coupling arrangement to move the third wheel towards the body. Block 912 may further comprise controlling the third coupling arrangement to move the third wheel from a first trailing position to a second trailing position such that the third wheel is in contact with the stair tread.

The above examples are to be understood as illustrative. Further examples are envisaged. Any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.