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Patent Searching and Data


Title:
VEHICLE
Document Type and Number:
WIPO Patent Application WO/2020/157465
Kind Code:
A1
Abstract:
An omnidirectional holonomic self-balancing vehicle comprises a chassis and three or more mecanum wheels, each coupled to the chassis. Each mecanum wheel has a main axis of rotation and each mecanum wheel is individually driveable about the main axis of rotation by a respective motor. The main axes are in a common plane including a ground contact line of each wheel. The vehicle also comprises a power source for the motors, and sensing means for sensing a lean angle of the vehicle and torque applied by the reaction wheel motor. The vehicle further comprises a reaction assembly mounted on the chassis, said assembly comprising a reaction motor arranged to move a reaction mass, either as a wheel about an axis of rotation parallel to the common plane, whereby the lean angle of the vehicle may be controlled by applying torque to the vehicle through drive of reaction wheel, or by changing the position of the mass and adjusting the position of the centre of gravity of the vehicle. A weight balancing arrangement may be provided for balancing weight distribution between a first mecanum wheel coupled to a chassis and a second mecanum wheel coupled to the chassis, the first and second mecanum wheels each having a respective motor. The weight balancing arrangement comprises a parallelogram arrangement.

Inventors:
WATSON MATTHEW THOMAS (GB)
Application Number:
GB2020/050141
Publication Date:
August 06, 2020
Filing Date:
January 22, 2020
Export Citation:
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Assignee:
UNIV SHEFFIELD (GB)
CONSEQUENTIAL ROBOTICS LTD (GB)
International Classes:
B62D37/04; B25J5/00; B60B19/12
Foreign References:
US9878587B12018-01-30
EP0560670A11993-09-15
JP5066746B22012-11-07
US20130299264A12013-11-14
EP1228951A12002-08-07
CN109263754A2019-01-25
EP3034323A12016-06-22
US8269447B22012-09-18
CN103303391A2013-09-18
CN207632434U2018-07-20
CN108454725A2018-08-28
CN202896207U2013-04-24
CN206243331U2017-06-13
US3789947A1974-02-05
US8738226B22014-05-27
US8540038B12013-09-24
JP2015081045A2015-04-27
JP5066746B22012-11-07
US9248876B22016-02-02
CN205113555U2016-03-30
US7980335B22011-07-19
Other References:
SAUL REYNOLDS-HAERTLEMIKE STILMAN: "Technical Report, GT-GOLEM-2011-005", 2011, GEORGIA INSTITUTE OF TECHNOLOGY, article "Design and Development of a Dynamically-Balancing Holonomic Robot"
CARLOS VIEGAS, OMNIDIRECTIONAL PERSONAL TRANSPORT, 2014, Retrieved from the Internet
Attorney, Agent or Firm:
HGF LIMITED (GB)
Download PDF:
Claims:
CLAIMS

1. An omnidirectional holonomic self-balancing vehicle comprising:

a chassis;

three or more mecanum wheels, each coupled to the chassis, wherein each mecanum wheel has a main axis of rotation in a common plane and each mecanum wheel is individually driveable about said main axis of rotation by a respective motor, each mecanum wheel comprising a ground-engaging periphery centred on its respective main axis, the periphery comprising a plurality of rollers, each roller being freely rotatable about a roller axis intersecting a circle centred on said main axis and being inclined at an offset angle with respect to a line parallel to said main axis and intersecting the roller axis and said circle, wherein, in use of the vehicle, said peripheries contact the ground along a groundline in said common plane;

a power source for the motors;

a controller for controlling each motor to drive each respective mecanum wheel; a reaction assembly mounted on the chassis, said assembly comprising a reaction motor arranged to move a reaction mass of the reaction assembly; and

sensing means to sense a lean angle of the vehicle, which angle comprises the angle between a COG plane, which COG plane includes the centre of gravity of the vehicle and the groundline, and a vertical plane including said groundline,

wherein:

the reaction assembly is configured to control the lean angle of the vehicle independently of, or complementary to, the action of the three or more mecanum wheels by moving the reaction mass with respect to the chassis to apply a counter- torque on the chassis or to alter the centre of gravity of the chassis; and

the controller is arranged to:

receive inputs from said sensing means and in response to said received inputs, generate a command signal to the reaction motor to move the reaction mass; and

drive one or more of the mecanum wheels about their respective main axes to achieve a desired movement of the vehicle and to maintain said lean angle of the vehicle with respect to the ground.

2. The omnidirectional holonomic self-balancing vehicle of claim 1 wherein the reaction mass is a reaction wheel mounted on the chassis, said assembly comprising a reaction wheel motor arranged to rotate the reaction wheel about an axis of rotation parallel to the main axis of the mecanum wheels;

the reaction wheel assembly is configured to control the lean angle of the vehicle by changing the rotational momentum of the reaction wheel, thereby imparting a counter-torque on the chassis; and

the controller is arranged to receive inputs from said sensing means and in response to said received inputs, generate a command signal to the reaction wheel motor to impart torque to the reaction wheel.

3. The omnidirectional holonomic self-balancing vehicle of claim 2, wherein the reaction wheel assembly is mounted along a bisecting plane perpendicular to the ground line and to the main axes of rotation of the mecanum wheels.

4. The omnidirectional holonomic self-balancing vehicle of claim 2 or 3, wherein the reaction wheel is configured to rotate bi-directionally.

5. The omnidirectional holonomic self-balancing vehicle of claim 1 , wherein the reaction mass is a movable weight, whereby the reaction motor moves the movable weight to change the position of the centre of gravity of the vehicle and thereby the lean angle.

6. The omnidirectional holonomic self-balancing vehicle of claim 5, wherein the movable weight is an eccentric wheel driven by the reaction motor to rotate the eccentric wheel in either direction of rotation from a central angular position in which the centre of gravity of the eccentric wheel is in the COG plane.

7. The omnidirectional holonomic self-balancing vehicle of claim 5, wherein the movable weight is a body slidably mounted on the vehicle and driven by said reaction motor to move the centre of gravity of the body across both sides of said COG plane.

8. The omnidirectional holonomic self-balancing vehicle of claim 5, 6 or 7, wherein the movable weight has a central position between its limits of movement which is biased to one side of the COG plane, preferably being on that side of the COG plane that is in a trailing direction of normal forwards movement of the vehicle whereby greater range of adjustment of the COG plane by movement of the movable weight is available in said forwards direction.

9. The omnidirectional holonomic self-balancing vehicle of any of claims 5 to 8, wherein the movable weight is located at a distance above the centre of gravity of the vehicle, whereby less movement of the movable mass is required in order to adjust the position of the COG plane.

10. The omnidirectional holonomic self-balancing vehicle of claims 1 to 9, further comprising four or more aligned mecanum wheels.

1 1. The omnidirectional holonomic vehicle of claim 10, wherein:

the vehicle has a bisecting plane perpendicular to a ground line that comprises a line joining the points of contact of the mecanum wheels with the ground when in normal use, wherein a first pair of said mecanum wheels is on one side of said bisecting plane and a second pair of said mecanum wheels is on the other side of said bisecting plane; and

each pair of said mecanum wheels has their rollers arranged so that the offset angle of each roller of each mecanum wheel of the pair, when in contact with the ground, is on the opposite side of said ground line.

12. The omnidirectional self-balancing vehicle of claim 1 1 , further comprising a first means for distributing a first weight between each mecanum wheel of the first pair of mecanum wheels and a second means for distributing a second weight between each mecanum wheel of the second pair of mecanum wheels, said first and second weights in combination comprising the weight of the vehicle.

13. The omnidirectional self-balancing vehicle of claim 12, wherein each of said first and second means for distributing a weight comprises a parallelogram arrangement comprising: a pair of plates, each plate fixed to the respective motor of the respective mecanum wheel of the pair of mecanum wheels;

a beam attached to the chassis; a first cross bar having a first end and a second end, the first cross bar pivotally coupled, intermediate its first and second ends, to the beam,

wherein the first end of the first cross bar is pivotally coupled to the respective plate of one of the motors of the pair of mecanum wheels and the second end of the first cross bar is pivotally coupled to the respective plate of the other motor of the pair of mecanum wheels, each coupled about axes that are parallel each other; and

a second cross bar having a first end and a second end, the second cross bar pivotally coupled, intermediate its first and second ends, to the beam, the second cross bar spaced apart from and parallel to the first cross bar,

wherein a first end of the second cross bar is pivotally coupled to the respective plate of one of the motors of the pair of mecanum wheels and a second end of the second cross bar is pivotally coupled to the respective plate of the other motor of the pair of mecanum wheels, each coupled about axes that are parallel each other; and

wherein the pair of plates are retained substantially parallel to each other when they pivot with respect to the first and second cross bars.

14. The omnidirectional self-balancing vehicle of claim 13, wherein each of said first and second means for distributing a weight further comprises a second parallelogram arrangement, wherein the first and second parallelogram arrangements are spaced about said pair of mecanum wheels and their respective motors to distribute the weight of the chassis on the respective plates.

15. The omnidirectional self-balancing vehicle of claim 14, wherein the first and second parallelogram arrangements are in a first plane and a second plane, respectively, the first and second planes being parallel to a common plane perpendicular to said bisecting plane and including said ground line.

16. The omnidirectional holonomic self-balancing vehicle of any of claims 1 to 15, wherein the three or more mecanum wheels are resiliently suspended from the chassis.

17. The omnidirectional holonomic self-balancing vehicle of any of claims 1 to 16, wherein a circumference of the ground engaging periphery of each of the three or more mecanum wheels is substantially the same.

18. The omnidirectional holonomic self-balancing vehicle of any of claims 1 to 17, wherein said sensing means comprises one or more orientation sensors to detect the orientation of the chassis in space and with respect to gravity, and to determine the torque applied by the reaction wheel motor.

19. The omnidirectional holonomic self-balancing vehicle of any of claims 1 to 18, comprising a substantially flat, load bearing platform attached to said chassis.

20. The omnidirectional holonomic self-balancing vehicle of claim 19, wherein said platform is a table.

21. The omnidirectional holonomic self-balancing vehicle of claim 19 or claim 20, wherein said platform comprises an upstanding mast.

22. The omnidirectional holonomic self-balancing vehicle of claim 21 , wherein the platform comprises a standing area for a human rider and the upstanding mast comprises a handle to be grasped by a rider.

23. The omnidirectional holonomic self-balancing vehicle of claim 22, wherein the standing area comprises sensing means for detecting a relative increase in weight or a change in centre of gravity caused by the rider.

24. The omnidirectional holonomic self-balancing vehicle of any of claims 1 to 21 , further comprising means for one or both of telepresence telephone conferencing and telepresence videoconferencing.

25. The omnidirectional holonomic self-balancing vehicle of claims 1 to 19 wherein the reaction wheel motor is actuated to produce vibration of the chassis to give haptic feedback to the user.

26. The omnidirectional holonomic self-balancing vehicle of claims 1 to 25 wherein one or more manipulators is attached to the vehicle.

27. The omnidirectional holonomic self-balancing vehicle of any of claims 1 to 26, further comprising a user input device comprising a touch screen, wherein the sensing means detects force applied against the touch screen and the controller is configured to actuate the reaction wheel motor to resist movement of the touch screen in response to said force.

28. The omnidirectional holonomic self-balancing vehicle of claim 27, wherein said sensing means includes means to detect approach of a user towards the touch screen, before the touch screen is touched and moved, whereby the controller is prepared to actuate the reaction wheel motor.

29. The omnidirectional holonomic self-balancing vehicle of claim 2, 3 or 4 or any of claims 10 to 28 when dependent on claim 2, wherein the reaction wheel is decelerated by regenerative braking, and the reaction wheel is used for recharging a battery or storing energy.

30. The omnidirectional holonomic self-balancing vehicle of any preceding claim in combination with a parking zone or area for the vehicle, wherein the parking zone comprises a backboard against which the mecanum wheels are abutted during parking, the vehicle being configured to lean towards and against the backboard prior to powering down of the vehicle into a standby mode in which the vehicle no longer maintains an active balance, means being provided to retain the vehicle in said parking zone when powered down.

31. The omnidirectional holonomic self-balancing vehicle and parking zone combination of claim 30, wherein the parking zone comprises a charging connector for charging of on-board batteries of the vehicle the vehicle docks with the parking zone.

32. The omnidirectional holonomic self-balancing vehicle and parking zone combination of claim 30 or 31 , wherein said means to retain comprise the mecanum wheels being configured to be locked when the vehicle is in standby mode.

33. The omnidirectional holonomic self-balancing vehicle and parking zone combination of claim 31 or 32, wherein said means to retain comprise a ridge of the parking zone provided at an entrance to the parking zone to prevent rolling of the vehicle out of the parking zone, once docked and powered down.

34. The omnidirectional holonomic self-balancing vehicle and parking zone combination of any of claims 30 to 33, wherein said means to retain comprise a clamp of the back board to clamp and retain the vehicle in position during parking.

35. A telepresence or other robotic device comprising the omnidirectional holonomic self balancing vehicle of any of claims 1 to 34.

36. An item of furniture comprising the omnidirectional holonomic self-balancing vehicle of any of claims 1 to 34.

37. A weight balancing arrangement for balancing weight distribution between a first mecanum wheel coupled to a chassis and a second mecanum wheel, coupled to the chassis, the first and second mecanum wheels each having a respective motor, the weight balancing arrangement comprising a parallelogram arrangement comprising:

a plate fixed to an end of the motor of the first mecanum wheel and a plate fixed to an end of the motor of the second mecanum wheel;

a beam attached to the chassis;

a first cross bar having a first end and a second end, the first cross bar pivotally coupled, intermediate its first and second ends, to the beam,

wherein the first end of the first cross bar is pivotally coupled to the respective plate of the motor of the first mecanum wheel and the second end of the first cross bar is pivotally coupled to the respective plate of the motor of the second mecanum wheel; and a second cross bar spaced apart from and parallel to the first crossbar, the second cross bar comprising a first end and a second end and pivotally coupled, intermediate its first and second ends, to the beam,

wherein the first end of the second cross bar is pivotally coupled to the respective plate of the motor of the first mecanum wheel and the second end of the second cross bar is pivotally coupled to the respective plate of the motor of the second mecanum wheel;

wherein first and second mecanum wheels each have a respective main axis of rotation, and the main axes of rotation of each of the mecanum wheels are parallel to each other and lie in a common plane, including during pivoting of the plates in their respective parallelogram arrangements.

38. The weight balancing arrangement of claim 37, wherein the plates of the respective motors are substantially parallel to each other.

39. A method of operating an omnidirectional holonomic self-balancing vehicle as claimed in any of claims 1 to 28, said method comprising:

the controller being initiated to commence movement of the vehicle in a reaction direction transverse to the main axis of the mecanum wheels;

the controller activating the reaction motor to move the reaction mass with respect to the chassis, either to apply a counter-torque on the chassis to urge the vehicle to lean in the reaction direction or to move the centre of gravity of the vehicle out of the vertical plane coincident with the ground line to initiate a lean of the vehicle under the influence of gravity in the reaction direction; and

activating the mecanum wheel motors to rotate and drive the vehicle in the reaction direction, whereby

the vehicle is operable to move in the reaction direction with an angle of lean from the unstable equilibrium of zero.

40. A method as claimed in claim 39, when not dependent on claim 4 or 5, wherein, during operation of the vehicle, the reaction wheel motor permanently drives the reaction wheel in one direction, whereby changes in the drive of the motor result in corresponding counter torques applied to the motor in different directions depending on whether the motor is accelerated or retarded.

Description:
VEHICLE

[0001] This invention relates to a mecanum-wheeled vehicle. Aspects of the invention relate to an omnidirectional holonomic self-balancing vehicle or autonomous robot, to a telepresence robot, to an item of furniture and to a weight balancing arrangement.

BACKGROUND

[0002] There is a need to provide a vehicle with the ability to travel in multiple directions, particularly in the fields of robotics, for example.

[0003] US3789947 discloses an omniwheel. An omniwheel typically comprises a ground engaging periphery centred about a main axis of rotation of the wheel. The ground engaging periphery comprises a series of rollers, each roller being freely rotatable about a respective roller axis of rotation. Each roller axis is at an angle of 90° to the main axis of rotation of the omniwheel. Omniwheels are such that the wheel can be driven around the main axis of rotation, but can also slide laterally with great ease, due to the rollers. Omniwheel vehicles are commonly provided with a polygonal wheel base, such as a square wheel base with an omniwheel in each corner of the square. The rollers may, in some cases, be driven. In other cases, the main axes of the omniwheels may be offset so that, depending on the rotation imparted to the wheels, lateral movement of the vehicle may be effected.

[0004] A mecanum wheel comprises a ground engaging periphery centred about a main axis of rotation of the wheel. The ground engaging periphery comprises a series of rollers, each roller being freely rotatable about a respective roller axis of rotation. Each roller axis intersects a circle centred on the main axis of the mecanum wheel and each roller is inclined at an offset angle with respect to a line, parallel to the main axis, which line intersects the roller axis and said circle. The offset angle is typically 45°, though any angle greater than - 90°, less than 90°, and not equal to 0° could be used. Mecanum wheels therefore allow a vehicle comprising mecanum wheels to move in any direction, including forwards, backwards, sideways, diagonally and purely rotationally. Mecanum wheels were invented in the 1970s and the principle of the mecanum wheel is well understood.

[0005] Mecanum wheeled vehicles commonly comprise a square or rectangular shape wheel base configuration, having a mecanum wheel in each corner of the square or rectangular base. Square and rectangular bases provide the vehicle with improved stability. US8738226 B2, US8540038 B1 and JP2015081045 A each relate to a mecanum wheeled vehicle having a rectangular wheel base.

[0006] Polygonal wheel bases, such as square or rectangular wheel bases occupy a large packing volume of space. The packing volume defines the minimum dimensions of the vehicle. Large packing volumes can limit the manoeuvrability of the vehicle. Consequently, there is a need to provide vehicles with reduced packing volumes.

[0007] Generally, mecanum wheels operate best when they are arranged to meet the ground perpendicular to the ground. It is often undesirable to have one or more wheels of a mecanum wheeled vehicle to contact a ground at other, non-perpendicular, angles. In practice, this requirement may restrict design freedom of a mecanum wheeled vehicle and reduces manoeuvrability of such vehicles, particularly over uneven ground.

[0008] JP5066746 B2 relates to an inverted pendulum type four-wheeled vehicle for riding outdoors by a standing user. The vehicle comprises a frame portion substantially parallel to a ground surface when the vehicle is at rest. The four wheels employed are omniwheels, as above described. Each of the four wheels are inclined in alternating directions relative to a longitudinal axis of a frame of the vehicle. In this way, the main axes of rotation (and indeed the respective planes) of any two adjacent wheels intersect each other. A problem with this arrangement is that due to the alternating directions of incline of the omniwheels relative to the frame, the wheels occupy a large packing volume of space, leading to a larger vehicle footprint. Furthermore, omniwheels inclined in this way on a vehicle are difficult to control. Viewing this configuration along its wheel rotation axes shows that the wheels form an ellipsoid profile. Control of a balancing platform using wheels with an ellipsoid profile is a difficult control task and, mathematically, is analogous to attempting to balance a spherical ball on top of a pointed end of a rugby ball.

[0009] Saul Reynolds-Haertle; Mike Stilman. (201 1). Design and Development of a Dynamically-Balancing Holonomic Robot. Georgia Institute of Technology, Technical Report, GT-GOLEM-201 1-005 (“Reynolds-Haerle”, available at

httpe://sm¾rtech qatech.edu/bitstream/handle/1853/41708/omnibaiancer. pdf) relates to a balancing robot comprising three mecanum wheels in an asymmetrical arrangement. Problems associated with this arrangement might include varying torque based on direction, unequal motor powers and asymmetrical control, for example.

[0010] Carlos Viegas (2014); Omnidirectional Personal Transport ; Available: http://contest.techbhefs.com/2014/enthes/automotlve-iranspor tatson/4019: (“Viegas” Last accessed 5 January 2017) relates to concept drawings of a mecanum Segway® type vehicle that incorporates mecanum wheels. The proposed vehicle comprises two mecanum wheels about a central omniwheel. The omniwheel comprises actuated rollers, which may be expensive and complex. The two mecanum wheels each have a main axis of rotation. The main axes of rotation of the two mecanum wheels are coincident. The central omniwheel comprises a main axis of rotation that is parallel to, but offset from, the main axes of rotation of the two mecanum wheels. This yields a statically stable holonomic system, the same as a conventional four Mecanum wheeled vehicle as in Viegas. However, the footprint of this vehicle is narrow in the forward/backwards direction, meaning it is easily tilted by acceleration or deceleration. If this occurs, at least one wheel will lift off the ground, resulting in loss of controllability. This problem might be solved by increasing the offset distance, however this would result in a wheel base occupying a larger packing volume.

[0011] Mecanum wheeled vehicles may be required to traverse over uneven terrain, which may cause tilting or wobbling of the vehicle. It is desirable to minimise any tilting or wobbling of the vehicle throughout vehicle operation.

[0012] US9248876 B2 relates to an omnidirectional vehicle comprising at least four mecanum wheels. Each of the at least four mecanum wheels is individually suspended from a body of the vehicle in a way that allows each respective mecanum wheel to be retracted into the vehicle body or to extend at least partially out of the vehicle body. Each individually suspended wheel arrangement comprises a height actuator that individually sets and maintains a height of its respective mecanum wheel, enabling the vehicle to traverse an uneven terrain. A problem with this arrangement is that it may be complicated and expensive to supply each individual mecanum wheel with its own height modulation means.

[0013] CN 2051 13555U relates to an inverted pendulum-like omnidirectional balancing vehicle comprising a four-wheel balance control system employing a motion compensation algorithm configured to detect movement by means of an internal gyroscope and an acceleration sensor. This arrangement results in a system with holonomic kinematics, meaning it is omnidirectional. However, from the stationary upright unstable equilibrium it is unable to generate constant forward acceleration without first accelerating the wheels backwards to initiate a forward tilt or lean motion, and vice versa. This is due to the dynamics of this system being nonholonomic. This is disadvantageous when the vehicle, is for example, parked next to a vertical obstacle, or when the vehicle is required to balance about the unstable equilibrium without movement of the wheel rotation axis.

[0014] Reaction wheels are known in the art. They are used mainly in the aerospace industry for three axis attitude control, but have recently been employed in robotics for the purpose of stabilising a robotic inverted pendulum-like vehicle by actuating the reaction wheel and thus creating a torque on the pendulum.

[0015] Sonal Karla; Dipesh Patel and Karl Stol; (2007) Available at: http://dteseerx.ist.psu.edU/vjewdoc/downjoad7doi~1Q.1.1 .124.5548&rep~rep1 &type~pdf

(“Karla”, last accessed 20 December 2018) relates to a two-wheeled inverted pendulum with an attached reaction wheel, wherein the centre of mass lies above the wheel/ground contact point. This arrangement allows independent control of the body lean angle and translational acceleration of the body at the wheel rotation axis, but is not omnidirectional due to the nonholonomic kinematic constraints imposed by the wheels.

[0016] Indeed, many vehicles are also nonholonomic, requiring some manipulation of the vehicle in order to achieve desired movements. That is, where a vehicle has several degrees of freedom, for example, movement according to one degree may necessitate movement according to one or more of the other degrees, which is wasteful and undesirable and limits manoeuvrability. For example, typical cars in use today have nonholonomic kinematic constraints in that they must perform a parallel-parking manoeuvre rather than sliding directly sideways into a parking space at a kerbside.

[0017] It is an object of embodiments of the invention to at least mitigate one or more of the problems associated with the prior art.

BRIEF SUMMARY OF THE DISCLOSURE

[0018] Aspects and embodiments of the invention provide a vehicle, a telepresence robot, an item of furniture and a weight balancing arrangement, as claimed in the appended claims.

[0019] According to an aspect of the invention, there is provided an omnidirectional self balancing vehicle comprising:

a chassis;

three or more mecanum wheels, each coupled to the chassis, wherein each mecanum wheel has a main axis of rotation in a common plane and each mecanum wheel is individually driveable about said main axis of rotation by a respective motor, each mecanum wheel comprising a ground-engaging periphery centred on its respective main axis, the periphery comprising a plurality of rollers, each roller being freely rotatable about a roller axis intersecting a circle centred on said main axis and being inclined at an offset angle with respect to a line parallel to said main axis and intersecting the roller axis and said circle, wherein, in use of the vehicle, said peripheries contact the ground along a groundline in said common plane;

a power source for the motors;

a controller for controlling each motor to drive each respective mecanum wheel; a reaction assembly mounted on the chassis, said assembly comprising a reaction motor arranged to move a reaction mass of the reaction assembly; and sensing means to sense a lean angle of the vehicle, which angle comprises the angle between a COG plane, which COG plane includes the centre of gravity of the vehicle and the groundline, and a vertical plane including said groundline,

wherein:

the reaction assembly is configured to control the lean angle of the vehicle independently of, or complementary to, the action of the three or more mecanum wheels by moving the reaction mass with respect to the chassis to apply a counter- torque on the chassis or to alter the centre of gravity of the chassis; and

the controller is arranged to:

receive inputs from said sensing means and in response to said received inputs, generate a command signal to the reaction motor to move the reaction mass; and

drive one or more of the mecanum wheels about their respective main axes to achieve a desired movement of the vehicle and to maintain a desired lean angle of the vehicle with respect to the ground.

[0020] In one embodiment, the reaction mass is a reaction wheel mounted on the chassis, said assembly comprising a reaction wheel motor arranged to rotate the reaction wheel about an axis of rotation parallel to the main axis of the mecanum wheels; and wherein the reaction wheel assembly is configured to control the lean angle of the vehicle independently of, or complementary to, the action of the three or more mecanum wheels by changing the rotational momentum of the reaction wheel and imparting a counter-torque on the chassis; and wherein the controller is arranged to receive inputs from said sensing means and in response to said received inputs, generate a command signal to the reaction wheel motor to impart torque to the reaction wheel.

[0021] Alternatively, however, the reaction mass may be a movable weight, whereby the reaction motor moves the movable weight to change the position of the centre of gravity with respect to the main axes of the mecanum wheels. By moving the weight and changing the position of the centre of gravity of the vehicle with respect to a ground line (being the line of contact of the mecanum wheels with the ground), tilt of the vehicle can be initiated under the influence of gravity, or, indeed, a reaction to tilting can effected.

[0022] The movable weight may be an eccentric wheel driven by the reaction motor to rotate the eccentric wheel in either direction of rotation from a central angular position in which the centre of gravity of the eccentric wheel is in the COG plane. [0023] Alternatively, the movable weight may be a body slidably mounted on the vehicle and driven by said reaction motor to move the centre of gravity of the body across both sides of said COG plane.

[0024] The movable weight may have a central position between its limits of movement which central position is arranged to one side of the COG plane, preferably being on that side of the COG plane that is in a trailing direction of normal forwards movement of the vehicle, whereby greater range of adjustment of the COG plane by movement of the movable weight is available in said forwards direction.

[0025] Typically, rotation of the wheel would be no more than 90 degrees in either direction, at least in the case where its rest position is with its centre of gravity coincident with the COG plane when the COG plane is coincident with the vertical plane passing through the groundline. However, this is not essential, as the rest position of the eccentric wheel could be arranged with the centre of gravity of the eccentric wheel to one side of the COG plane when the COG plane is coincident with the vertical plane passing through the groundline. Nevertheless, a total rotation of the eccentric wheel of more than 180 ceases to have any further extension of the adjustment of the centre of gravity of the vehicle.

[0026] The movable weight may be located at a distance above the centre of gravity of the vehicle, whereby less movement of the movable mass is required in order to adjust the position of the COG plane.

[0027] Optionally, the sensing means may also sense torque applied by the reaction wheel motor to the reaction wheel. Herein, the term“independently” means that the desired value of the lean angle is maintained without regard to the position and/or movement of the three or more mecanum wheels of the vehicle. The term“complementary” means that the value of the lean angle is controlled in addition by movement of the mecanum wheels. The term “track” means evaluating the lean angle of the vehicle and adjusting its value dynamically whilst performing varying operations. Thus, it may be desired to lean the vehicle in the direction of movement before accelerating in that direction and then subsequently allowing the lean angle to return to a desired position, for example, upright, when accelerations have ceased. Tracking the lean angle includes maintaining a specific lean angle or adjusting it dynamically.

[0028] Advantageously, this provides a vehicle that can be controlled in a manner as to fully actuate the lean angle, yaw angle, and two Cartesian position coordinates that uniquely define the vehicles’ position and orientation on a ground surface. That is, provided suitable control of the reaction wheel motor, the system dynamics in these states can be made to be holonomic. This also enables control of the lean angle of the vehicle independently of the action of the mecanum wheels. This advantageously allows the balancing of the vehicle by means of the reaction wheel assembly without actuation of the mecanum wheels, both when stationary and when moving. That is, the vehicle may be truly holonomic

[0029] A suitable control of the mecanum wheels and reaction wheel may be used to minimise actuation of the reaction wheel, for example to minimise reaction wheel motor torque or speed requirements.

[0030] In some embodiments, the control of the lean angle of the vehicle is performed using a PID (proportional-integral-derivative) controller. In this method the reaction wheel is actuated to preserve the desired lean angle of the chassis of the vehicle which should never substantially deviate from the upright unstable equilibrium. Any deviation from the set lean angle of zero is adjusted by means of the PID controller. The PID controller is used to minimise an error over time by adjusting a control variable, said error being the difference between a setpoint and a measured value of the lean angle of the chassis. Feedback signal (measured lean angle) is then compared with a reference signal and error signal, and the PID algorithm produces a controlled output for the process. This advantageously allows to control the lean angle by selecting the values of proportional, integral and derivative gains and, therefore, to drive the lean angle to zero by actuation of the reaction wheel. In some embodiments, the reaction wheel is decelerated using regenerative braking, this advantageously can provide additional power savings. In this case, the reaction wheel can recharge a battery or store energy.

[0031] Advantageously, the main axes of rotation of the mecanum wheels lie in a common plane, which common plane comprises the ground line that intersects the ground engaging periphery of each mecanum wheel when the vehicle rests on substantially flat ground with said ground line in contact with the ground. The vehicle thus has a wheel base of three or more wheels arranged in a common plane, thereby reducing the area occupied by the wheel base of the vehicle. This advantageously reduces packing volume of the wheel base and increases manoeuvrability of the vehicle. The arrangement also provides the vehicle with the ability to translate in a direction along the mecanum wheel rotation axes. This advantageously reduces a minimum navigable gap of the vehicle to a diameter of the largest wheel, compared to a standard Segway ® vehicle, for example, whose navigable gap is limited to the width of the platform measured along the wheel rotation axis, unless a parallel parking manoeuvre is performed. This minimum gap size might be, for example, 0.5 to 1 metre.

[0032] In some embodiments the reaction wheel assembly is mounted along a bisecting plane perpendicular to the ground line and to the main axes of rotation of the mecanum wheels. Optionally, the reaction wheel assembly may be mounted centrally and as low as possible. However, alternative mounting arrangements are also possible and any mounting location may be chosen. The nearer the reaction wheel can be mounted to the vehicle centre of mass, the smaller the overall vehicle inertia, reducing the torque requirements of the reaction wheel motor.

[0033] In some embodiments, the reaction wheel is configured to rotate bi-directionally. Advantageously, it allows to start movement of the vehicle in either forward or backward direction. Alternatively, the reaction wheel may be configured to rotate continuously during operation of the vehicle.

[0034] In this mode, the reaction wheel may be decelerated by regenerative braking, in which event the reaction wheel may be used for recharging a battery or storing energy when rotating.

[0035] The reaction wheel motor may be actuated to produce vibration of the chassis to give haptic feedback to the user, whether normally stationary or continuously rotating. Such feedback may be useful in notifying the user of commands received and acknowledged. Vibration of the reaction wheel, especially if the reaction wheel is positioned near the centre of gravity of the vehicle, should not interfere with balancing of the vehicle and will result in oscillation of the vehicle back and forth around the axis of rotation of the reaction wheel. Despite that a vibration effect could also be achieved via the mecanum wheel motors, the vibration of the mecanum wheel motors will always yield translation of the chassis, whereas oscillating the reaction wheel motor could produce vibration without translating the chassis. Furthermore, mecanum wheels have a large number of moving parts that would be noisy if the mecanum wheels were vibrated, whereas a reaction wheel can be nearly silent in operation.

[0036] Indeed, constant high velocity of rotation of the reaction wheel provides inertia which may be useful in preventing vibration (when not required and initiated for haptic response) or wobbling of the vehicle. By operating the reaction wheel at a high velocity, this could be used to resist side-to-side wobble, giving an additional purpose for the reaction wheel as a momentum wheel. This will resist rotation about the two axes perpendicular to the balance axis, whereas the use of the reaction wheel to generate vibration would act about the balance axis, meaning these two functions can operate simultaneously and independently.

[0037] One or more manipulators may be attached to the vehicle, for example to enable the vehicle to pick up and transport objects, or operate equipment remotely from a user.

[0038] A user input device may be provided, comprising a touch screen, wherein the sensing means detects force applied against the touch screen and the controller is configured to actuate the reaction wheel motor to resist movement of the touch screen in response to said force. [0039] The sensing means may include means to detect approach of a user towards the touch screen, before the touch screen is touched and moved, whereby the controller is prepared to actuate the reaction wheel motor.

[0040] In some embodiments of the present invention, the three or more mecanum wheels may have a diameter of 30 centimetres, although smaller or larger diameter wheels may be used, for example, having a diameter of between 20 and 40 centimetres.

[0041] In some embodiments, the orientation of the chassis may be maintained at the vertical unstable equilibrium.

[0042] In some embodiments, the sensing means comprises the controller being communicable with a remote sensor or a remote sensor system. The controller may be communicable with the remote sensor or remote sensing system by means of an input means for receiving a signal from the remote sensor or remote sensing system. Advantageously, this removes the need for at least some on-board sensors.

[0043] However, the controller controlling each motor to drive each respective mecanum wheel may be arranged to be responsive to some or all of:

• the torque applied to the reaction wheel by the reaction wheel motor;

• the lean angle of the vehicle;

• the angular position and velocity of the mecanum wheels; and

• commands received by the controller of the direction, speed and orientation that the vehicle is to adopt.

[0044] The controller may be configured to react to the angular position of the mecanum when trying to drive the platform to a particular location, meaning a location measurement is required, which can be derived from the angular position of the mecanum wheels. Other parameters may be detected to control the vehicle, as desired, and to control actuation of the reaction wheel.

[0045] In some embodiments, the torque applied to the reaction wheel by the reaction wheel motor is sensed by the sensing means comprising a torque sensor on the reaction wheel or between the reaction wheel and the reaction wheel motor. However, it may also or instead be inferred by the controller from an instruction to the reaction wheel motor, which may be generated by the controller in response to the orientation of the vehicle with respect to the common plane, herein also referred to as its lean angle, and commands received by the controller.

[0046] In some embodiments, said sensing means comprises one or more orientation sensors to detect the orientation of the chassis in space with respect to gravity, including its lean angle. This advantageously enables detection or monitoring of an orientation of the chassis of the vehicle. Optionally, the sensors include one or more of any of: an accelerometer, a gyroscope and a magnetometer.

[0047] Commands may be received by the controller of the position, direction, speed and orientation that the vehicle is to adopt. The commands may be given by an external control unit that may be remote from the vehicle and that may communicate with the controller wirelessly, or by direct input of commands to a user interface on or connected to the vehicle.

[0048] In some embodiments, the vehicle comprises a body fixed to the chassis.

[0049] In some embodiments, the three or more wheels may be substantially circular when viewed from a side. This improves controllability of the vehicle. In some embodiments, the three or more wheels may be perfectly circular when viewed from a side.

[0050] In some embodiments, the vehicle may comprise four or more mecanum wheels, preferably aligned with each other and having common axes.

[0051] In some embodiments, the vehicle has a bisecting plane perpendicular to said ground line, wherein a first pair of said mecanum wheels is on one side of said bisecting plane and a second pair of said mecanum wheels is on the other side of said bisecting plane; and each pair of said mecanum wheels has their rollers arranged so that the offset angle of each roller of each mecanum wheel of the pair, when in contact with the ground, is on the opposite side of said ground line.

[0052] Optionally, the vehicle further comprises a first means for distributing a first weight between each mecanum wheel of the first pair of mecanum wheels and a second means for distributing a second weight between each mecanum wheel of the second pair of mecanum wheels, said first and second weights in combination comprising the weight of the vehicle. Advantageously, the mecanum wheels of each pair are moveable relative to each other, and a weight of the chassis can therefore be distributed between the pairs of mecanum wheels. Because each pair comprises its own weight distribution means, more flexibility is provided in wheel movement in a direction perpendicular to the ground, allowing the vehicle to move over a bump or discontinuity on the ground. This advantageously means that ground contact with the wheels may be maintained even on uneven ground.

[0053] In some embodiments, each of said first and second means for distributing a weight comprises a parallelogram arrangement comprising:

a pair of plates, each plate fixed to the respective motor of the respective mecanum wheel of the pair of mecanum wheels;

a beam attached to the chassis; a first cross bar having a first end and a second end, the first cross bar pivotally coupled, intermediate its first and second ends, to the beam

wherein the first end of the first cross bar is pivotally coupled to the respective plate of one of the motors of the pair of mecanum wheels and the second end of the first cross bar is pivotally coupled to the respective plate of the other motor of the pair of mecanum wheels, each coupled about axes that are parallel each other;

a second cross bar having a first end and a second end, the second cross bar pivotally coupled, intermediate its first and second ends, to the beam, the second cross bar spaced apart from and parallel to the first cross bar,

wherein a first end of the second cross bar is pivotally coupled to the respective plate of one of the motors of the pair of mecanum wheels and a second end of the second cross bar is pivotally coupled to the respective plate of the other motor of the pair of mecanum wheels, each coupled about axes that are parallel each other; and

wherein the pair of plates are retained substantially parallel to each other when they pivot with respect to the first and second cross bars.

[0054] Advantageously, the parallelogram arrangement means that a pair of wheels can advantageously move with respect to each other. The movement may be in a direction substantially perpendicular to the ground. Because each pair comprises its own weight distribution means, more flexibility is provided in wheel movement in a direction perpendicular to the ground, allowing the vehicle to move over a bump or discontinuity on the ground. This advantageously means that ground contact with the wheels may be maintained even on uneven ground. The parallelogram arrangement also advantageously ensures, or at least improves the chances that, each of the mecanum wheels meets the ground substantially perpendicularly to the ground.

[0055] Optionally, the beam may be laterally positioned between the two mecanum wheels of the pair of mecanum wheels of the pair or wheels.

[0056] In some embodiments, each of said first and second means for distributing a weight further comprises a second parallelogram arrangement, wherein the first and second parallelogram arrangements are spaced about said pair of mecanum wheels and their respective motors to distribute the weight of the chassis on the respective plates. This advantageously improves balancing and stability of the vehicle. Optionally, the first and second parallelogram arrangements are in a first plane and a second plane, respectively, and the first and second planes are parallel to said common plane.

[0057] In some embodiments, the four or more mecanum wheels are resiliently suspended from the chassis. Advantageously, resilient suspension provides for shock absorption as the vehicle travels over discontinuities in the ground. Optionally, the four or more wheels may be resiliently suspended by means of a damper, such as a spring damper.

[0058] In some embodiments, a circumference of the ground engaging periphery of each of the four or more mecanum wheels is substantially the same. Advantageously, this enables a more compact wheel base. Optionally, the main axes of the four or more mecanum wheels may be coaxial when the vehicle is at rest on a substantially flat, horizontal ground. This also advantageously enables a more compact wheel base.

[0059] In some embodiments, the body comprises a load bearing platform. The platform may be fixed to the chassis or may be releasably attached to the chassis. The platform may be substantially flat. Advantageously, a load bearing platform enables the vehicle to carry a load placed on the platform, and can transport a load by carrying the load on the platform between different locations.

[0060] In some embodiments, the platform is a table. This means that the vehicle can function as a moveable table, which is advantageously easier to move than a conventional table comprising one or more stationary legs or feet, which conventional table would require a user to lift or push the table.

[0061] In some embodiments, the platform comprises an upstanding mast. The may be adjustable in length, such as telescopically and/or by means of hinged sections.

[0062] In some embodiments, the mast comprises means for connecting to a telepresence accessory, such as a videoconferencing device. Optionally, the videoconferencing device may be a tablet or a smart phone. Said means may comprise, for example, one or more of any of: a clip, a clamp and a recess. Alternatively, the vehicle may comprise means for videoconferencing, such as a display, a camera, a microphone, a speaker and wireless communication means. Advantageously, the vehicle may therefore be used as a mobile videoconferencing device. As used herein, a telepresence robot means a remotely controllable device that enables apparent participation by a user in an event occurring at a location other than where the user is physically. Such a device typically has wireless internet connectivity or another suitable wireless communication protocol. Typically, a telepresence robot uses a tablet to provide video and audio capabilities, although this is not essential. For example, an integrated display screen, camera, audio input and audio output may be provided.

[0063] In some embodiments, the platform may comprise a standing area for a human rider. Advantageously, this provides a relatively compact vehicle that is rideable by the user. The upstanding mast optionally comprises a handle to be grasped by a rider. Optionally, instructions as to how the vehicle should move may be passed to the controller by the rider through the standing area and/or the handle.

[0064] Optionally, the standing area comprises sensing means for detecting a relative increase in weight or a change in centre of gravity caused by the rider. Said sensing means may be communicable with the controller. This advantageously enables the rider to control the vehicle by means of shifting their centre of gravity, such as by leaning forwards, backwards, left or right, for example.

[0065] In some embodiments, the platform may include sensing means to enable autonomous navigation of the vehicle in an unknown or known environment. For example, position sensing means, object detecting means and map means may be included.

[0066] In some embodiments the platform may contain screens, speakers, microphones, or other interactive means to enable the vehicle to interact with and be operated by a user.

[0067] However, the need for a reaction wheel assembly in a vehicle operated by a human rider is nominal. The rider has little difficulty in accommodating lean of the vehicle. However, it may still be desirable in cases where the vehicle is summoned from a parking area or zone to a user.

[0068] In some embodiments, the vehicle is an indoor vehicle. Indoors in this sense means an environment including any type of terrain which might be found inside a building or dwelling, such as, for example, carpeted floor, laminate flooring, wood flooring, ceramic tiles, floorboards and synthetic flooring, such as linoleum flooring.

[0069] According to another aspect of the invention, there is provided a telepresence robot comprising the omnidirectional self-balancing vehicle substantially as above described.

[0070] According to another aspect of the invention, there is provided an item of furniture comprising the omnidirectional self-balancing vehicle substantially as described above.

[0071] According to another aspect of the invention, there is provided a weight balancing arrangement for balancing weight distribution between a first mecanum wheel coupled to a chassis and a second mecanum wheel coupled to the chassis, the first and second mecanum wheels each having a respective motor, the weight balancing arrangement comprising a parallelogram arrangement comprising:

a plate fixed to an end of the motor of the first mecanum wheel and a plate fixed to an end of the motor of the second mecanum wheel;

a beam attached to the chassis;

a first cross bar having a first end and a second end, the first cross bar pivotally coupled, intermediate its first and second ends, to the beam, wherein the first end of the first cross bar is pivotally coupled to the respective plate of the motor of the first mecanum wheel and the second end of the first cross bar is pivotally coupled to the respective plate of the motor of the second mecanum wheel; and a second cross bar spaced apart from and parallel to the first crossbar, the second cross bar comprising a first end and a second end and pivotally coupled, intermediate its first and second ends, to the beam,

wherein the first end of the second cross bar is pivotally coupled to the respective plate of the motor of the first mecanum wheel and the second end of the second cross bar is pivotally coupled to the respective plate of the motor of the second mecanum wheel;

wherein first and second mecanum wheels each have a respective main axis of rotation, and the main axes of rotation of each of the mecanum wheels are parallel to each other and lie in a common plane, including during pivoting of the plates in their respective parallelogram arrangements.

[0072] Advantageously, the mecanum wheels are moveable relative to each other. The movement may be in a direction substantially perpendicular to the ground. Advantageously, a weight of the chassis can therefore be distributed between the mecanum wheels. More flexibility is provided in wheel movement in a direction perpendicular to the ground, advantageously allowing the vehicle to move over a bump or discontinuity on the ground. This advantageously means that ground contact with the wheels may be maintained even on uneven ground.

[0073] Optionally, the beam may be laterally positioned between the two mecanum wheels of the pair of mecanum wheels of the pair or wheels.

[0074] In some embodiments, the plates of the respective motors are substantially parallel to each other.

[0075] According to another aspect of the invention, there is provided a method of operation of the vehicle, said method comprising:

the controller being initiated to commence movement of the vehicle in a reaction direction transverse to the main axis of the mecanum wheels;

the controller activating the reaction motor to move the reaction mass with respect to the chassis, either to apply a counter-torque on the chassis to urge the vehicle to lean in the reaction direction or to move the centre of gravity of the vehicle out of the vertical plane coincident with the ground line to initiate a lean of the vehicle under the influence of gravity in the reaction direction, and activating the mecanum wheel motors to rotate and drive the vehicle in the reaction direction, whereby

the vehicle is operable to move in the reaction direction with an angle of lean from the unstable equilibrium of zero lean angle.

[0076] Advantageously, this allows control of the vehicle lean angle independently of movement of the wheel rotation axis and may be such that the tendency of the vehicle to lean in the reaction direction, as urged by the counter-torque imposed, is itself countered by the acceleration imposed by the mecanum wheels driving the vehicle in the reaction direction, whereby there is no actual lean of the vehicle in the reaction direction or otherwise.

[0077] In the case of a movable mass that alters the position of the centre of gravity of the vehicle, the vehicle may have an apparent lean angle (that is, an over-balance position whereby there is an angle between the vertical plane parallel, including the ground line, and a plane passing through the centre of gravity of the vehicle and parallel and including the ground line) whilst still holding an upright position of the vehicle.

[0078] This is particularly advantageous in scenarios where the vehicle is unable to move its base in a particular direction, for example due to an obstacle. A typical balancing wheeled inverted pendulum in this scenario, in which the vehicle is already leaning toward the obstacle, would be unable to move into a position in which it is leaning away from the obstacle, as do to so would require the movement of the wheels into the space occupied by the obstacle. However, with a reaction assembly the lean angle of the platform can be independently controlled, allowing such a transition without movement of the mecanum wheel rotation axis. In other words, this vehicle can instantaneously achieve a steady state acceleration in any direction. Of course, this is within the constraints of maximum torque and speed of the reaction wheel, or adjustment of the centre of gravity of the vehicle.

[0079] This allows the vehicle to lean against solid objects in order to achieve a statically stable pose, for example to allow for shutdown or charging, whilst still being able to transition back into a dynamically balanced pose without any external actuation.

[0080] Moreover, a parking zone or area for the vehicle may comprise a backboard against which the mecanum wheels are abutted during parking, the vehicle leaning the chassis towards and against the backboard prior to powering down the vehicle to a standby mode in which the vehicle no longer maintains an active balance. Optionally, the vehicle docks with a charging connector for charging of on-board batteries of the vehicle. The mecanum wheels may be locked when the vehicle is in standby mode. Alternatively, a ridge may be provided at an entrance to the parking zone to prevent rolling of the vehicle out of the parking zone, once docked and powered down. Alternatively or additionally, the back board may include a clamp to retain the vehicle in position during parking.

[0081] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

[0082] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0083] One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an omnidirectional self-balancing vehicle;

Figure 2 is a side view of the vehicle of Figure 1 ;

Figure 3 is an end view of the vehicle of Figure 1 ;

Figure 4 is a side view of a mecanum wheel and motor for use in the vehicle of Figure 1 ; and

Figure 5 is a table comprising the vehicle of Figure 1 ;

Figure 6 is a telepresence robot comprising the vehicle of Figure 1 ;

Figure 7 is a user rideable vehicle comprising the vehicle of Figure 1 ; Figure 8 is a perspective view of a holonomic omnidirectional self-balancing vehicle in accordance with the present invention and having many of the features of the vehicle illustrated in Figures 1 to 8;

Figures 9a to e are respectively side views of a vehicle in accordance with two different embodiments of the present invention: (a) a first embodiment parked in a parking zone; (b) the same embodiment, in the process of leaving the parking zone; (c) the same embodiment leaning against a wall comprising a different parking zone; (d) a different embodiment, with a different reaction assembly, in the parking zone position shown in Figure 9a; and (e) another embodiment with another different reaction assembly; and

Figure 10 is a side view of a vehicle comprising a robotic manipulation arm.

DETAILED DESCRIPTION

[0084] With reference to Figures 1 to 3, an omnidirectional self-balancing vehicle 100 comprises a chassis 10 supported by four inline mecanum wheels 12a, 12b, 12c, 12d, each having a main axis of rotation 14a, 14b, 14c, 14d. The main axes 14a to 14d of each mecanum wheel 12a, 12b, 12c, 12d are substantially parallel to each other and lie in a common plane 15 (see Figure 3). Each mecanum wheel 12a, 12b, 12c, 12d is individually drivable about its main axis of rotation 14a to 14d by a respective motor 16a, 16b, 16c, 16d. The vehicle 100 includes a power source 18a, 18b, which, in some embodiments, may comprise a rechargeable battery, for energising the motors 16a to 16d. The motors 16a to 16d are therefore energiseable to drive the wheels 12a to 12d about their respective main axes. Depending on a drive direction of each wheel 12a to 12d, the chassis 10 can be arranged to move in a plane parallel the ground G in any direction, including pure rotation. Although two power sources 18a, 18b are shown in Figures 1 to 3, it is to be appreciated that the invention may nevertheless be put into effect with only one power source or indeed more than two power sources.

[0085] With reference to Figure 4, each mecanum wheel 12 comprises a ground engaging periphery 20 around the main axis 14 of the wheel 12. The ground engaging periphery 20 comprises a series of rollers 22, each roller being freely rotatable about a respective roller axis of rotation 24. Each roller axis 24 intersects a circle centred on the main axis 14 of the mecanum wheel 12 and is inclined at an offset angle A with respect to a line, parallel to the main axis 14, which line intersects the roller axis 24 and said circle. In some embodiments, the angle A is 45°. Each roller axis of rotation 24 may additionally or alternatively be offset 45° to a plane of the wheel. The plane of the wheel may be perpendicular to the main axes of rotation 14 of the wheels 12a to 12d. [0086] The common plane 15 of the main axes 14 comprises a ground line 23 that intersects the ground engaging periphery 20 of each mecanum wheel 12a, 12b, 12c, 12d. The vehicle 100 is arranged to rest on a substantially flat ground G, with said ground line 23 in contact with the ground G. When a roller engages the ground G, its roller axis 24 is parallel to the ground, as is a line 25 that intersects it and which line 25 is also parallel to the main axis 14.

[0087] Turning again to Figures 1 to 3, in some embodiments, the ground engaging periphery 20 of each mecanum wheel 12a to 12d is of substantially the same circumference. When the ground peripheries 20 of each mecanum wheel 12a to 12d are of substantially the same circumference, the main axes of the mecanum wheels 12a to 12d are coaxial when the vehicle 100 is at rest on the substantially flat ground G.

[0088] The vehicle 100 comprises a bisecting plane 1 1 perpendicular to the ground line and to the main axes of rotation 14a, 14b, 14c, 14d. The plane 1 1 is defined by two orthogonal axes 11 1 and 113, the axis 1 1 1 being parallel the ground G when the vehicle is positioned on flat, horizontal ground as shown in Figure 3, whilst the axis 113 is perpendicular to ground. The four mecanum wheels 12a, 12b, 12c, 12d can be grouped into two pairs 28, 30 of mecanum wheels. A first pair 28 comprises wheels 12a and 12b and is on one side of the bisecting plane 11 and a second pair, 30 comprises wheels 12c and 12d and is on the other side of the bisecting plane 11. In some embodiments, the pairs 28, 30 of mecanum wheels are equidistant from the bisecting plane 1 1.

[0089] Each mecanum wheel of a pair 28, 30 has their rollers 22 arranged so that the offset angle A of each roller of a pair, when in contact with the ground, are on opposite sides of the ground line. That is, each mecanum wheel of a pair has an opposite“handedness”. For example, within pair 28, if mecanum wheel 12a is right-handed, then mecanum 12b is left- handed. If mecanum wheel 12a is left-handed, then mecanum 12b is right-handed. Similarly, within pair 30, if mecanum wheel 12c is right-handed, then mecanum 12d is left-handed and if mecanum wheel 12c is left-handed, then mecanum 12d is right-handed. In this way, it will be appreciated that the pattern of handedness of the four mecanum wheels 12a, 12b, 12c, 12d, respectively, may be any one of:

• left, right, left, right;

• right, left, right, left;

• left, right, right, left; or

• right, left, left, right.

[0090] By alternating wheels with left and right-handed rollers in this way, the vehicle is stable and can be made to turn and to move in any direction by varying the speed and direction of rotation of each wheel. The meaning of“handedness” is well understood in the art. As noted in US7,980,335, “handedness” is most easily determined by imagining the wheel acting inside a close-fitting pipe. A right-handed mecanum wheel, when driven clockwise, would“screw” into the pipe and a left-handed mecanum wheel, when driven clockwise, would“screw” out of the pipe.

[0091] The vehicle 100 further comprises sensing means (not shown), for sensing an orientation of the chassis 10 with respect to the ground G, or at least with respect to gravity. In some embodiments, the sensing means comprises one or more orientation sensors, such as a gyroscope, an accelerometer, a magnetometer, to detect the orientation of the chassis in space and with respect to gravity.

[0092] Vehicle 100 comprises a controller 32 for controlling each motor 16a to 16d, to drive each respective mecanum wheel 12a to 12d. The controller 32 is arranged to receive an input from the sensing means (not shown) and in response thereto, the controller 32 is arranged to drive one or more of the mecanum wheels 12a to 12d about their respective main axes 14, to achieve a desired movement of the vehicle 100 and to maintain an orientation of the chassis 10 with respect to the ground G beneath the vehicle 100. The controller may comprise processing means, such as a processor, for determining an orientation of the chassis 10 based on the input from the sensing means. A memory means, such as a random access memory (RAM), may store one or more algorithms for use by the processing means to enable said determining. The memory means may also store information regarding a desirable orientation or orientations of the chassis 10 with respect to the ground G. The arrangement of the vehicle 100 is such that movement of the vehicle 100 in any direction over flat, horizontal ground results in equal power output by the first 28 and second 30 pairs of mecanum wheels 12a to 12d. Thus, the motors 16a to 16d driving the mecanum wheels 12a to 12d may all have the same power capacity, and hence be of the same size. Because the arrangement is balanced, there is no requirement for any one motor to be any more powerful than any other motor in order to achieve equal speed and manoeuvrability of the vehicle in any direction.

[0093] The vehicle 100 may comprise means, such as Bluetooth®, for a wireless communication between the vehicle 100 and a user. For example, a Bluetooth® connection could be established between the controller 32 of the vehicle 100 and a mobile device of the user, such as a smartphone or a tablet computer. Movement of the vehicle 100 may therefore be controlled by a user via a remote control device. Although Bluetooth® is described in the above example, it will be appreciated that indeed any wireless communication protocol may be used. [0094] The vehicle 100 may comprise means for distributing a weight of the chassis 10 between each mecanum wheel of a pair 28, 30 of mecanum wheels, whereby ground contact with the wheels may be maintained on uneven ground. In some embodiments, the means comprises one or more parallelogram arrangements. With reference to Figures 1 and 2, with particular reference to pair 28 of mecanum wheels 12a and 12b, a plate 34a, 34b, is fixed to each mecanum wheel 12a, 12b, such as to the respective motor 16a, 16b. The plates 34a, 34b of the respective motors 16a, 16b of a pair 28 of mecanum wheels 12a, 12b are substantially parallel to each other. A beam 36 is attached to the chassis, for example by fastening means such as screws. The beam 36 may be laterally located between the two mecanum wheels 12a, 12b of the pair 28, so that the two mecanum wheels 12a, 12b are equidistant from the beam 36. Beam 36 may be a vertical beam. The term vertical beam is meant in the sense that the beam is arranged to provide a beam function substantially perpendicularly to the ground G. In the embodiments illustrated in Figures 1 , 2 and 5, a triangular component is used as the beam, however it will be understood that other shapes may be used. A first cross bar 38 is pivotally coupled at its centre 38a to the beam 36, proximal to the chassis 10. A first end 38b of the first cross bar 38 is pivotally coupled to the respective plate 34a fixed to the motor 16a of mecanum wheel 12a. A second end 38c of the first cross bar 38 is pivotally coupled to the respective plate 34b fixed to the motor 16b of the mecanum wheel 12b. A second cross bar 40 is pivotally coupled at its centre 40a to the beam 36, distal to the chassis 10. The first and second cross bars 38, 40 are spaced apart from one another and are substantially parallel. A first end 40b of the second cross bar 40 is pivotally coupled to the respective plate 34a fixed to the motor 16a of mecanum wheel 12a. A second end 40c of the second cross bar 40 is pivotally coupled to the respective plate 34b fixed to the motor 16b of the mecanum wheel 12b. The first and second cross bars 38, 40 are substantially rigid and pivot about their respective ends 38b, 38c, 40b, 40c and centres 38a, 40a, respectively.

[0095] In this way, it will be appreciated that a parallelogram is formed between the parallel end plates 34a, 34b and the parallel cross bars 38, 40. The angles of the internal vertices of the parallelogram formed by the end plates 34a, 34b and the cross bars 38, 40 are variable by means of the cross bars pivoting about the above described pivot points. Due to the parallelogram arrangement and because the beam 36 is attached to the chassis 10 and is perpendicular to the ground G, the wheels 12a, 12b of pair 28 are each moveable relative to each other, in a direction substantially perpendicular to the ground G. This enables the vehicle 100 to move over discontinuities in the ground, such as bumps or obstacles. With reference again to Figures 1 and 2, a second parallelogram arrangement is provided for pair 30 of mecanum wheels 12c and 12d. That is, the second pair 30 of mecanum wheels is provided with a vertical cross bar 36, a pair of substantially parallel cross bars 38, 40 and a pair of substantially parallel plates 34c, 34d fixed to the respective motors 16c, 16d of the respective mecanum wheels 12c, 12d. In this way, the pairs 28, 30 of mecanum wheels are independently moveable in a direction substantially perpendicular the ground G and the wheels of each pair are moveable relative to each other in that same direction.

[0096] As can be seen in Figure 3, the means for distributing weight between each mecanum wheel of a pair of mecanum wheels may comprise a first parallelogram arrangement, X, as above described and a second parallelogram arrangement, Y, also as above described. The first and second parallelogram arrangements, X, Y, are spaced about said pair of mecanum wheels and their respective motors and the first and second parallelogram arrangements are in a first plane 15a and a second plane 15b, respectively. The first and second planes are parallel to said common plane 15.

[0097] In some embodiments, the vehicle 100 further comprises damping means (not shown) for damping oscillations of the four or more mecanum wheels 12a to 12d. The damping means may comprise the mecanum wheels 12a to 12d being resiliently suspended from the chassis 10. In some embodiments, the damping means may comprise a dashpot associated with each mecanum wheel.

[0098] The chassis 10 functions as a structural frame of the vehicle 100, to which the four or more mecanum wheels are coupled. It will therefore be appreciated that the vehicle 100 may be further adapted for use in a variety of applications, for example by mounting one or more body components to the chassis 10.

[0099] In some embodiments, the vehicle 100 may be adapted for use as an item of furniture, such as an item of smart furniture. With reference to Figure 5, the vehicle 100 functions as a table. The chassis 10 comprises a substantially flat, load bearing platform 70 for performing the function of a table. The platform 70 may be arranged to be in an orientation substantially parallel to a substantially flat, horizontal ground G on which the vehicle 100 is resting. In this way, vehicle 100 may function as a table, on which a user may place objects if desired. The table is therefore moveable in any direction, enabling it to move around a variety of environments, even one comprising numerous obstacles and tight spaces. In some embodiments, said sensing means is arranged to sense a signal indicative of at least one of a relative increase in weight, a tilt angle of the platform and a change in centre of gravity. Said controller is arranged to receive an input from said sensing means and in response thereto, take action to maintain the orientation of the chassis with respect to the ground, so that the platform is in a substantially horizontal plane. As described above, in some embodiments, the vehicle 100 may comprise means, such as Bluetooth®, for a wireless communication between the vehicle 100, or the controller 32 of the vehicle 100, and a remote control device. For example, a Bluetooth® connection could be established between the controller 32 and a mobile device of the user, such as a smartphone or a tablet. Movement of the vehicle 100 may therefore be controlled by a user operating a remote control device. In this way, a driveable, omnidirectional, self-balancing table is provided. Although a table is described and illustrated in Figure 5, it will be appreciated that the vehicle 100 could be used to provide a variety of other driveable omnidirectional self-balancing items of furniture, including smart furniture, such as a chair, a foot stool or a chest of drawers, for example.

[00100] In some embodiments, the vehicle 100 may be adapted for use as a telepresence robot. The vehicle 100 may comprise a display screen, a camera, a microphone, an audio output, such as a speaker, and means for connecting to a wireless network, such as Wi-Fi. In other embodiments, such as the example illustrated in Figure 6, the vehicle 100 comprises attachment means 50 for retaining a telepresence device 51 , such as a tablet computer or a smartphone. The telepresence device 51 provides means to enable remote communication, such as a display screen 56, a camera 58, a microphone 60 and an audio output (not shown), such as a speaker. The telepresence device may be provided separately, or a kit of parts comprising a telepresence device and the vehicle 100 having retaining means may be provided. In this way, the telepresence robot enables apparent participation by a user in an event occurring at a location other than where the user is physically located. Said attachment means 50 may comprise a mast 52 upstanding from the chassis and a clip 54. The mast may be extendable in length for example, telescopically. The clip 54 is coupled to the mast 52 and comprises a bracket including a pair of spaced apart retaining claws 54a, 54b. The spacing between the pair of retaining claws 54a, 54b may be adjustable, to enable easy insertion and removal of the telepresence device 51. The clip 54 may be rotatably coupled to the mast 52. The vehicle 100 may include sensing means for tracking a user. The controller 32 may be arranged to receive a signal indicative of a user’s location and in response thereto, output a signal to drive one or more of the mecanum wheels 12a to 12d to move the vehicle 100 towards the user.

[00101] In some embodiments, such as that illustrated in Figure 7, the vehicle 100 is adapted for use as a vehicle for riding by a user. The vehicle 100 may comprise a platform 70 comprising a standing area 84 for a human rider and an upstanding mast 80 having a handle 82 to be grasped by a rider. Instructions may be passed to the controller 32 by the rider through one or both of said standing area 84 and said handle 82. For example, the handle 82 may be provided with one or more buttons or throttle grips (not shown), wherein actuation of a button or throttle grip sends a signal to the controller 32. The standing area 84 may comprise sensing means (not shown) to detect a relative increase in weight and/or a relative tilt angle of the platform 70 caused by the rider. In response thereto, the controller 32 is arranged to drive one or more of the at least four wheels 12a to 12d.

[00102] The vehicle 100 my further comprise a user input device (not shown) further comprising a touch screen, wherein the sensing means detects force applied against the touch screen. For example, sensing means can comprise an integrated force/pressure sensor such as Force Sensitive Resistor (FSR). It is appreciated that any alternative pressure-sensing or tactile technology can be used to detect physical pressure and/or force applied to the touch screen. However, it may be detected through resultant lean of the vehicle. In any event, this feature would make the touch screen feel more 'solid' to a user. This could also be performed in a reactionary manner, i.e. as a correction due to the detection of a change in lean angle.

[00103] Alternatively, this feature could be implemented proactively, when the system detects that the user is about to push on the screen. This could be by three-dimensional tracking of the user, by the sensing of a finger near the touchscreen before a force is applied, or likely by other means. For example, the sensing means of the vehicle 100 may further comprise a motion detector that is activated when the user approaches the touch screen, such as a passive infrared (PIR) sensor, although it is appreciated that ultrasound, microwave radiation and the combination thereof can operate as said sensing means.

[00104] According to embodiments of the present disclosure, a vehicle may comprise a reaction assembly mounted on the chassis, said assembly comprising a reaction motor arranged to move a reaction mass of the reaction assembly. With reference to Figure 8, the vehicle 800 may have a reaction assembly in the form of a reaction wheel assembly 801. The reaction wheel assembly 801 has a reaction mass that is a reaction wheel 802 and a reaction wheel motor 803. The reaction wheel is mounted on a bearing (not shown), and its rotational velocity can be controlled by the reaction wheel motor 803. More in particular, the reaction wheel motor 803 can be coaxially located in a central region of the reaction wheel 802. The reaction wheel assembly 801 is coupled to the chassis 10, however alternative mounting positions are available.

[00105] In an exemplary embodiment, the reaction wheel can be rotated bi-directionally, thus advantageously allowing to lean the vehicle 800 in the vertical bisecting plane 1 1 in either forward direction 804 or in a backward direction 805.

[00106] In use, the torque created by the reaction wheel motor 803 is imparted on the reaction wheel. This torque then creates a counter-torque that is imposed on the vehicle in which the motor is mounted. Acceleration or deceleration of the reaction wheel can be used to balance the vehicle 800. [00107] According to an embodiment of the invention, and with reference to Figure 8, there is provided an omnidirectional holonomic self-balancing vehicle 800, comprising at least three mecanum wheels 12 (except that, in the embodiment illustrated, there are four wheels 12a-d), a chassis 10’, and a reaction wheel assembly 801 further comprising a reaction wheel 802 and a reaction wheel motor 803.

[00108] The vehicle 800 is similar in many respects to the vehicle described with reference to Figures 1 to 7 and where features are substantially the same, the same reference numerals are employed, sometimes with the use of an apostrophe Q to indicate that the feature in question is different in some respects. Absence of an apostrophe should not be taken as indicating identity however.

[00109] The reaction wheel motor 803 is fixed in the chassis 10 and drives the reaction wheel 802 about a reaction wheel rotation axis 810 that is in the common plane 15, comprising the ground line 23 and the main axes 14 of the mecanum wheels 12. The rotation axis 810 may however be displaced from the plane 15, but is preferably at least parallel the axes 23, 14.

[00110] As described above, sensing means (not shown) may be provided that indicate the orientation of the chassis with respect to the common plane 15. The controller 32’ may be configured to operate the mecanum wheel motors 16a-d in order to maintain the centre of gravity of the vehicle above the ground line 23 and maintain balance of the vehicle with respect to the common plane 15.

[00111] In some embodiments, such as that illustrated in Figure 10, the vehicle 1000 can comprise one or more multi-section robotic arm assemblies 1001 for manipulating and transporting objects. The robotic arm assembly may comprise a gripping means 1002 and an arm platform 1003 for coupling the robotic arm assembly to the chassis 10 of the vehicle 1000. However, it will be apparent to a skilled person that any alternative coupling (to a side, adjacent, underneath) is also suitable for mounting the arm with respect to the vehicle 1000.

[00112] Where the vehicle comprises a table or other surface on which components may selectively be disposed, this may result in a change in the position of the centre of gravity of the total vehicle plus any additional carried components. Accordingly, a stable position of the vehicle may not be at a precise (or unvarying) orientation of the chassis with respect to the common plane. Accordingly, rather than merely responding to a difference between a current orientation of the vehicle with respect to gravity to a single, specific, orientation of the vehicle (as a means of effecting a correcting movement of the vehicle by the mecanum wheels 12), the controller preferably reacts to changes in orientation of the chassis with respect to time. The controller may be arranged to“learn”, through an“anti- hunting” routine, to establish the balance position of the vehicle at any given time and state. The balance position is established when the orientation of the chassis does not change rapidly and oscillates with small changes in direction of drive of the mecanum wheels in order to maintain balance. Nevertheless, oscillation of the vehicle around the axis 14 is an inevitable and required condition to achieve balance.

[00113] Furthermore, to drive the vehicle in a reaction direction (that is, a direction perpendicular to the common plane 15) it is first necessary for the vehicle to lean in that direction so that a balancing correction movement of the mecanum wheels not only moves the vehicle in that direction but tends to return it towards the balance position. However, to maintain forward movement, the controller does not accelerate the mecanum wheels to such an extent that the balance position is reached, but instead accelerates only sufficient to maintain a lean angle of the vehicle that also maintains a requirement for forward (or rearward) movement to correct the lean angle. Indeed, the situation is such as to achieve a new balance position where the forward lean accounts for friction and air resistance experienced by the vehicle as a result of the movement of the vehicle. (That is, in the absence of any air resistance or friction, once acceleration in the vehicle could have a constant velocity whilst having the same orientation with respect to gravity that it has when stationery. However, air resistance and friction effects mean it must maintain a constant lean angle, different from the stationery position, when moving and this angle is greater as the velocity increases.)

[00114] Accordingly, in an embodiment of the present invention, the sensing means (not shown) may also be arranged to detect torque applied by the reaction wheel motor 803 to drive the reaction wheel 802 and, in response to detection of such torque, the controller may be configured to accelerate the mecanum wheels 12 to apply a balancing torque. Equally, rather than accelerating the mecanum wheels 12 to maintain balance of the vehicle, detection of changes in orientation of the vehicle by the controller may be employed to accelerate the reaction wheel motor 803 to apply a countertorque on the chassis of the vehicle to counteract any lean of the vehicle and to maintain balance of the vehicle. By this means, balance of the vehicle can be achieved without movement of the chassis. Furthermore, movement of the vehicle can be accommodated without lean provided constant torque is applied to the reaction wheel 802 by the reaction wheel motor 803, equal to the effects of air resistance and friction during such movement.

[00115] Indeed, the orientation detection means may be integrated in the torque sensing means, because changes in orientation of the vehicle will result in changes to the torque applied between the motor on the reaction wheel. This is best achieved by the reaction wheel being constantly driven with a constant velocity during normal operation of the vehicle. While this continuously absorbs power from on-board batteries, when frictional effects of that drive is minimised, the power absorbed can be minimised. However, with the reaction wheel being constantly driven, small changes in the torque applied are more easily detected. The velocity of constant rotation should not, however, be so high that further torque in the direction of rotation is significantly more difficult for the motor to apply than it is for the motor to apply torque in an opposite, braking, direction.

[00116] By this means, balance of the vehicle is achieved primarily through action of the reaction wheel assembly 801 and drive of the vehicle in any given direction is achieved by operation of the mecanum wheels 12 without reference to balance of the vehicle. As described above, movements in the common plane 15, or rotations about the vertical axis 1 13, do not impact the balance of the vehicle and therefore can be effected without reference to other degrees of freedom of the vehicle. In this way, therefore, movement of the vehicle in any of its degrees of freedom is independent of movements in other degrees of freedom and the vehicle is truly holonomic with three degrees of freedom. This means that it is feasible to maintain a zero lean angle whilst moving and accelerating within any of its three degrees of freedom.

[00117] A further benefit of the reaction wheel assembly 801 is provided when the vehicle 800 is parked, resting against a wall 900 as shown in Figure 9a. In this condition, it is probable that the vehicle 800 will be powered down, to preserve battery condition, or possibly be connected to a power source (not shown) for battery recharging. Indeed, the possibility exists for an automatic coupling to be effected with a charging station. Regarding positioning of the vehicle 800 during parking, two possibilities exist. A first is that the vehicle remains in a vertical or leaning outward position but is retained in the parking position by a clamp arrangement 901. The clamp arrangement 901 (along with a recharging coupling) could automatically be activated when a vehicle parks and the vehicle be held in an upright position by clamping means 901. An upright position means the centre of gravity of the vehicle to be substantially in line with a plane 903 perpendicular to the ground, which plane is coincident with the common plane 15. Clamping means 901 are capable of mechanically clamping the vehicle 900 and may be made of a pair of juxtaposed clamping jaws, however alternative arrangements are also possible.

[00118] An omnidirectional vehicle without the reaction wheel assembly, in order to move in the forward direction, would normally need to roll in the backward direction to start leaning forward. This movement would not be possible if the vehicle is held against the wall due to insufficient space to move in the backward direction. Advantageously, this can be overcome by employing a reaction assembly mounted on the vehicle.

[00119] When in use and according to Figure 9b, the clamp 901 is released and the vehicle 900 receives a command signal from the control means (not shown) to initiate movement in the forward direction 902. The reaction wheel motor 803 is activated to drive the reaction wheel in an anti-clockwise direction A, thus imparting a countertorque on the motor 803 in a clockwise direction C opposite to the rotation A of the reaction wheel. This, in turn, urges the vehicle 800 to lean forward, about the main axes 14 of the mecanum wheels 12 at an angle LA to the plane 903. The controller then activates the mecanum wheels 12 to rotate around their axes 14 in clockwise direction D in order to commence moving and to maintain the lean angle LA of the vehicle 900 with respect to the ground. As discussed above, because of the reaction wheel assembly 801 , the lean angle LA can in fact be minimised and reduced to substantially zero.

[00120] Indeed, in the simplest case, the vehicle is parked as shown in Figure 9c, in which a vehicle 800 is manoeuvred against a wall 900 and powering-off of the vehicle is achieved by first ensuring that it is separated from the wall by a small margin and then arranging for it to lean towards the wall immediately before disabling the balancing reaction, whereupon the vehicle will fall against the wall. At the same time, either the mecanum wheels 12 are locked against further free-rolling, or a wedge 907 is disposed on the ground G adjacent the wall to prevent the vehicle from rolling away from the wall. In leaning against the wall, the vehicle is stable, even when powered off.

[00121] On re-powering of the vehicle, when it is required again, the first action is to drive the reaction wheel 802 anti-clockwise, as in Figure 9b, to pivot the vehicle clockwise into an upright, balanced position. When that position is achieved drive of the mecanum wheels 12 is commenced to move the vehicle (over wedge 907 where present) away from the wall 900.

[00122] Turning to Figure 9d, a different embodiment of the invention, as generally illustrated and described above with reference to Figures 9a to 9c, is shown. Here, the reaction assembly 80T comprises a reaction mass in the form of an eccentric reaction wheel 802’. Now, rather than spinning a concentric reaction wheel to apply a counter-torque on the reaction motor 803, as previously described (and thus applying a tilting torque on the chassis mast 52), the reaction motor 803 is arranged to turn the eccentric wheel 802’ by up to 90 degrees from the position shown in Figure 9d.

[00123] In Figure 9d, with the vehicle in an upright, normal operating position, its centre of gravity COG would be arranged in the common plane 15 that is coincident with the main axes 14 and ground line 23. The position of the centre of gravity COG in the plane 15 is not material, but is generally desirable to be as low as possible. It depends however on the furniture disposed on the vehicle, as well as the vehicle itself. However, the reaction assembly 80T is arranged also in the common plane 15 and indeed its own mass adjusts the position of the centre of gravity COG. In the embodiment of Figure 9d, the axis 810 of the reaction wheel motor 803 is arranged also in the common plane, so that any rotation of the eccentric wheel 802’ moves the centre of gravity to one side or the other of the plane 15 by virtue of the mass of the wheel 802’. Rotation is limited to 90 degrees, because the centre of gravity of the mass of the wheel 802’ returns towards the plane after that rotation. It is however understood that the reaction assembly 801’ does not need to be aligned with the centre of mass and it can also be offset from the common plane 15. Furthermore, the reaction assembly 801’ can be positioned above the centre of gravity COG (not shown on Figure 9d), alternatively it can be placed below the wheel rotation axis 14. (This flexibility in positioning applies equally to the reaction wheel assembly 801 described above.) However, if the vehicle is parked substantially vertically as shown, even a minor rotation of the wheel 802’ will be sufficient to cause the vehicle to over balance and tilt or lean, whereupon the mecanum motors can be started to drive the vehicle. During normal drive, the reaction wheel can be kept at an angle that allows the mast to be vertical while under movement, whereas, when the vehicle is stopped, the wheel can be returned to a central position, as shown in Figure 9d. That is, despite there being zero actual lean angle LA of the vehicle, nevertheless, the apparent lean angle (as defined between the plane containing the centre of gravity COG, the COG plane, and including the ground line 23, and the vertical plane 903 is such that the vehicle must move, in the direction of apparent lean, in order to maintain that spatial position. It has to be noted that the rest position of the eccentric wheel 802’ tends towards the position in which its own centre of gravity is immediately below the rotation axis 810. However, it could be fixed in a rest position at some angle whereby greater adjustment is possible in one direction than the other. However, a total adjustment of only 180 degrees is possible for a rotatable eccentric weight.

[00124] In Figure 9e, a further embodiment of a vehicle 800” is shown, in which the reaction wheel 802’ described above is replaced by a weight 812 that is slidably mounted on a slide 814 under a table 816, which table is mounted on the mast 52. A reaction motor 803’ is fixedly mounted under the table and drives a screw-threaded shaft 818 that is threaded in a corresponding bore of the weight 812. Rotation of the motor thereby screws the shaft into and out of the weight 812 to translate the weight across the common plane 15 in the direction of the arrows X and so as to adjust the centre of gravity COG of the vehicle back and forth as desired across the plane 15. Mounting the weight at a distance from the centre of gravity has the effect that smaller movements of the slide weight 812 (which may be smaller in mass) result in more significant deviations of the centre of gravity from the balance position. The balanced position of the vehicle is, of course, where the centre of gravity is directly above the ground line when the vehicle is stationary, but it is where the vehicle is leaning at some angle to the vertical when the vehicle is moving. An alternative mounting for the slide assembly would be directly on the chassis platform 10”. [00125] During movement, balance of the vehicle can be maintained by continuous adjustment of the speed of rotation of the mecanum wheels 12 (as it also can when the vehicle is stationary). However, this results in continuous alteration of the attitude of the vehicle, that may manifest itself as unsteady movement and continuous accelerations back and forth. Steady movement can instead be achieved by adjustment of the reaction assembly without any apparent movement of the vehicle.

[00126] Throughout the description and claims of this specification, the words“comprise” and“contain” and variations of them mean“including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[00127] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[00128] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[00129] It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program. Still further, embodiments of the present invention may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

[00130] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[00131] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[00132] The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.