FIELD OF THE INVENTION

The present invention relates to an omniwheel and method.

BACKGROUND

Omniwheels are known and are able to roll freely in two directions. The omniwheel is able to roll in a main direction of travel along its major circumference about a main rolling axis provided typically by an axle located in a central hub , like a conventional wheel. Along that major circumference is provided a plurality of discs or rollers which define rolling surfaces extending around that major circumference. These rollers provide the contact patch between the omniwheel and the surface over which it travels. However, the rolling axis of the rollers themselves are orientated to be non-parallel, and typically perpendicular, to the main rolling axis the omniwheel. This enables the omniwheel to also move in another direction of travel, which is perpendicular to the main direction of travel, through rotation of the rollers about their axis.

Although such omniwheels provide for significant manoeuvrability and other advantages, they each have their own shortcomings. Accordingly, it is desired to provide an improved omniwheel.

SUMMARY

According to a first aspect, there is provided an omniwheel, comprising: a central hub rotatable about a central axis; a plurality of supports coupled with the central hub; and at least one roller coupled with each support to define a rolling surface during rotation of the central hub about the central axis, each roller being rotatable about a roller axis orientated to be non-parallel with the central axis, the at least one roller being deflectable at its leading edge.

The first aspect recognises that a problem with existing omniwheels is that they can be noisy, suffer from vibrations and/ or be unsuited to travel over anything over anything other than extremely level surfaces. Accordingly, an omniwheel is provided. The omniwheel may comprise a centrally-located hub. This centrally-located hub may be rotatable around a central axle which may be received within the central hub. The central axle may define a central axis. The omniwheel may comprise more than one support. The supports may be coupled with the central hub. The omniwheel may comprise one or more rollers, each coupled with a support. The rollers may together define a rolling surface of the omniwheel when the central hub is rotated around the central axle. Each roller may be rotatable around a roller axle. Each roller axle may be received by the roller. The roller axle may define a roller axis. The roller axis may be orientated or positioned to be other than parallel with the central axis. That is to say, the central axis and the roller axis may be non-parallel or divergent with the central axis. The roller may be deflectable, moveable or translatable at its leading edge. In this way, the rolling surface defined by the rollers is accommodating due to the leading edge of the rollers being deflectable. Such deflection helps to ameliorate the effects of so- called“stepping” which can occur due to the miss-positioning of the rollers as the central hub rotates. Such miss-positioning can lead to a discontinuity in the rolling surface provided by the rollers which can lead to excessive noise and vibration as the roller impacts the surface over which the omniwheel is travelling. Through the deflection at the leading edge, the rollers exhibit reduced noise and levels of vibrations. Also, the operation of the omniwheel is improved when travelling over irregular surfaces since the deflection can reduce the effects of raised features on that surface.

In one embodiment, the at least one roller is deflectable at its leading edge in response to contact with a body encountered during rotation of the central hub about the central axis. Accordingly, the roller is deflectable or translatable due to contact or interaction with a body or surface encountered during the rotation of the central hub.

In one embodiment, the leading edge is that contact patch of the at least one roller which first contacts the body over which the omniwheel travels during rotation about the central axis. Accordingly, the leading edge may be that contact patch or portion of the roller which initially contacts or interacts with the body or surface over which the omniwheel travels or rolls during rotation around the central axis. It will be appreciated that the leading edge may typically be located at or towards one axial end of each roller.

In one embodiment, the leading edge is deformable to accommodate deflection at its leading edge. Accordingly, the leading edge may be deflectable by deforming or distorting in order to accommodate the deflection at the leading edge.

In one embodiment, the at least one roller defines at least one aperture to facilitate deformation. Accordingly, the roller may define or be provided with one or more apertures which facilitate the deformation of the leading edge. Providing an aperture gives a space into which material of the roller can move to assist in its deformation. In one embodiment, the at least one aperture comprises at least one of a hole, a slit and a void.

In one embodiment, the at least one aperture comprises at least one recess on a leading face of the roller proximate the leading edge. Accordingly, the roller may be provided with a recess, groove or annular chamber provided on the leading face which is proximate to, adjacent or abutting the leading edge.

In one embodiment, the at least one recess comprises a circumferential recess extending around the leading face. The recess may extend at least partially or intermittently around the leading face.

In one embodiment, the at least one aperture extends within the roller proximate the leading edge. Accordingly, the aperture may be provided within the roller in the vicinity of the leading edge.

In one embodiment, the at least one aperture extends through the roller. Accordingly, the aperture may extend throughout the roller.

In one embodiment, the omniwheel comprises a plurality of apertures. Providing more than one aperture may improve the deformation.

In one embodiment, the plurality of apertures are distributed circumferentially around the roller. Distributing the apertures helps to ensure reliable deformation, irrespective of the rotation position of the roller.

In one embodiment, the at least one roller comprises at least one of a compressible and a non-compressible material. Accordingly, the roller may be formed of a compressible material and/ or a non-compressible material. It will be appreciated that with a compressible material, the need for such apertures to facilitate deformation may be reduced, whereas with a non-compressible material the deformation may be facilitated by the apertures.

In one embodiment, the at least one roller comprises a composite having a

compressible inner portion and a non-compressible outer portion. Typically, non- compressible materials are better-wearing than compressible materials, so providing a non-compressible outer portion improves the life of the roller.

In one embodiment, the omniwheel comprises a biasing mechanism which is compressible to accommodate translation of the at least one roller due to deflection at its leading edge. Accordingly, a biasing mechanism or member may be provided. The biasing mechanism may be compressible or deformable in response to movement of the roller when deflection occurs at its leading edge.

In one embodiment, the biasing member is operable to resiliently compress to accommodate movement of the least one roller from a resting position to a translated position. Accordingly, the biasing member may resiliently compress in response to movement of the roller. That is to say, the biasing member may elastically deform in response to movement of the roller. Accordingly, the roller may move between a resting position in which no compression occurs and a translated position in which compression occurs.

In one embodiment, the biasing mechanism is compressible to accommodate at least one of a radial translation of the at least one roller towards the central hub, an axial translation of the at least one roller along its roller axle and a pivoting translation of the at least one roller about its support. Accordingly, the biasing mechanism may accommodate a radial translation or movement of the roller towards the central hub. That is to say, a movement with at least a radial component may be accommodated by the biasing mechanism. The biasing mechanism may accommodate an axial translation or movement of the roller along the roller axle. That is to say, movement of the roller with at least a component in the direction of the roller axis may be accommodated by the biasing mechanism. The biasing mechanism may accommodate a pivoting movement of the roller around its support. That is to say, a movement with at least a pivoting or turning movement of the roller on its support may be accommodated by the biasing mechanism.

In one embodiment, the biasing member couples the central hub with the plurality of supports. Accordingly, the biasing member may couple or connect the central hub with each of the supports. In one embodiment, the biasing member extends radially between the central hub and the plurality of supports. Accordingly, the biasing member may extend with at least a radial component between the central hub and the supports.

In one embodiment, the biasing member comprises at least one spring extending between the central hub and the plurality of supports. Accordingly, the biasing member may comprise one or more spring members which extend between the central hub and the supports.

In one embodiment, the biasing member is operable to resiliently compress to accommodate movement of the at least one roller from a resting axial position along its roller axle to a translated axial position along its roller axle. Accordingly, the biasing member may elastically deform in response to movement of the roller between a resting axial position and a translated axial position along the roller axis.

In one embodiment, the biasing member comprises at least one spring positioned to urge the at least one roller towards the resting axial position. Accordingly, the spring may cause the roller to move towards the resting position.

In one embodiment, the biasing member comprises a pair of springs which receive the at least one roller therebetween to urge the at least one roller towards the resting axial position. The presence of the pair of springs helps to maintain the location of the roller at a selected axial position.

In one embodiment, the omniwheel comprises a debris removal member located between adjacent rollers and shaped to remove debris accumulated between adjacent rollers.

In one embodiment, the debris removal member has a tapered cross-section.

In one embodiment, the debris removal member is rotationally immobile between adjacent rollers.

In one embodiment, the debris removal member is rotationally fixed on the roller axle.

According to a second aspect, there is provided a method, comprising: rotating a central hub about a central axis; coupling a plurality of supports with the central hub ; and deflecting at least one roller at its leading edge, the at least one roller bring coupled with each support which defines a rolling surface during rotation of the central hub about the central axle, each roller being rotatable about a roller axis orientated to be non-parallel with the central axis.

In one embodiment, the method comprises deflecting the at least one roller at its leading edge in response to contact with a body encountered during rotation of the central hub about the central axis.

In one embodiment, the leading edge is that contact patch of the at least one roller which first contacts the body over which the omniwheel travels during rotation about the central axis.

In one embodiment, the leading edge is deformable.

In one embodiment, the method comprises defining the at least one roller with at least one aperture to facilitate deformation.

In one embodiment, the method comprises providing at least one of a hole, a slit and a void as the at least one aperture.

In one embodiment, the method comprises providing at least one recess on a leading face of the roller proximate the leading edge as the at least one aperture.

In one embodiment, the method comprises providing a circumferential recess extending around the leading face as the at least one recess.

In one embodiment, the method comprises extending the at least one aperture within the roller proximate the leading edge.

In one embodiment, the method comprises extending the at least one aperture through the roller.

In one embodiment, the method comprises providing a plurality of apertures.

In one embodiment, the method comprises distributing the plurality of apertures circumferentially around the roller. In one embodiment, the at least one roller comprises at least one of a compressible and a non-compressible material.

In one embodiment, the at least one roller comprises a composite having a

compressible inner portion and a non-compressible outer portion.

In one embodiment, the method comprises compressing a biasing mechanism to accommodate translation of the at least one roller due to deflection at its leading edge.

In one embodiment, the method comprises resiliently compressing the biasing member to accommodate movement of the least one roller from a resting position to a translated position.

In one embodiment, the method comprises compressing the biasing mechanism to accommodate at least one of a radial translation of the at least one roller towards the central hub, an axial translation of the at least one roller along its roller axle and a pivoting translation of the at least one roller about its support.

In one embodiment, the method comprises coupling the central hub with the plurality of supports using the biasing member.

In one embodiment, the method comprises extending the biasing member radially between the central hub and the plurality of supports.

In one embodiment, the method comprises providing at least one spring extending between the central hub and the plurality of supports as the biasing member comprises.

In one embodiment, the method comprises resiliently compressing the biasing member to accommodate movement of the at least one roller from a resting axial position along its roller axle to a translated axial position along its roller axle.

In one embodiment, the method comprises providing at least one spring positioned to urge the at least one roller towards the resting axial position as the biasing member. In one embodiment, the method comprises providing a pair of springs which receive the at least one roller therebetween to urge the at least one roller towards the resting axial position as the biasing member. In one embodiment, the method comprises locating a debris removal member between adjacent rollers and shaped to remove debris accumulated between adjacent rollers.

In one embodiment, the debris removal member has a tapered cross-section. In one embodiment, the debris removal member is rotationally immobile between adjacent rollers.

In one embodiment, the debris removal member is rotationally fixed on the roller axle. Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims. Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which :

Figures 1A and 1B show a portion of an omniwheel when travelling over a surface; Figure 2 illustrates a personal mobility vehicle incorporating an omniwheel according to one embodiment;

Figure 3 illustrates the omniwheel in more detail;

Figure 4 illustrates the central hub 160 of the omniwheel of Figure 3 ;

Figure 5 is a cross-sectional view through the omniwheel of Figure 3 ;

Figure 6 is a close-up sectional view of the pair of rollers mounted on the support of the omniwheel of Figure 3 ; and

Figures 7A to 7C illustrate a debris removal device of one embodiment. DESCRIPTION OF THE EMBODIMENTS

Before discussing embodiments in any more detail, first an overview will be provided. Embodiments provide an omniwheel which provides for improved ride quality through the provision of rollers which are deflectable. In particular, that portion of each roller which contacts first with the surface over which the omniwheel is travelling is able to deflect in order to reduce noise and shock that would otherwise be experienced in operation. As can be seen in Figures lA and 1B which shows schematically (not to scale) a portion of an omniwheel, rollers 20 are positioned to align with a

circumference C, which defines a main rolling surface of the omniwheel when rotating about its main, central axle 10. However, manufacturing tolerances and/ or wear in the components which position each roller 20 can lead to the rollers 20 failing to align to the circumference C.

As a result, as can be seen in Figure 1A, when the omniwheel rotates in the direction RF, which results in movement over the underlying surface 30 in the direction D, a roller 20 which is unaligned with the circumference C will impact the surface 30. The deviation Di of the roller 20 from the circumference C will cause the roller 20 to impact the surface 30 , resulting in noise and vibration, with the axle 10 being lifted by up to the deviation Di. Likewise, as shown in Figure 1B, should the underlying surface 30 be other than flat then, again, the roller 20 will impact the underlying surface 30 causing sound and vibration, with the axle being lifted by up to D ₂ . Embodiments seek to ameliorate these effects by having at least the leading edges of the rollers arranged to be deflectable in order to reduce the effects of such misalignment.

Personal Mobility Device

Figure 2 illustrates a personal mobility vehicle 100 , such as a wheelchair, according to one embodiment. The wheelchair has a seat 110 coupled with a chassis 120. Also coupled with the chassis 120 is a pair of front wheels 130 and a pair of omniwheels 140. Motors (not shown) provide power to at least the front wheels 130 and preferably to the omniwheels 140 to move the personal mobility vehicle 100 under the control of the occupant 150.

Omniwheel

Figure 3 illustrates the omniwheel 140 in more detail. The omniwheel 140 has a central hub 160 which receives a central axle 170. The central axle 170 connects the omniwheel 140 with the chassis 120. If driven, then a drive mechanism (not shown) is used to rotate the omniwheel 140 in either the direction R _F or the direction R _R . Connected with the central hub 160 is a plurality of supports 180. In this embodiment, each support 180 upstands radially from the radially outer surface of the central hub 160. Each of the supports 180 or stanchions is equi-spaced circumferentially around the radially outer surface of the central hub 160 arranged in a single bank. In this embodiment, each support 180 is bolted onto a radially upstanding shoulder 165 of the central hub 160. Each support 180 supports a pair of rollers 190 by means of a roller axle 195 which extends through the support 180 in a direction which is perpendicular to the axis of the central axle 170. Each roller axle 195 is orientated tangentially to the

circumference C as it passes through the support 180. The pair of rollers 190 sit on either side of each support 180. Each roller 190 has an elastomer surface which reduces wear and provides grip. This arrangement of the rollers 190 makes them accessible and helps to prevent the build-up of debris since the space around the rollers 190 is open. Also, having identical supports 180 with identical pairs of rollers 190 repeated around the central hub 160 provides a modular system with common parts.

Figure 4 illustrates the central hub 160 in more detail (with the supports 180 and rollers 190 removed to improve clarity) and show the shoulder 165 having threaded apertures 163 which receive bolts that connect the support 180 to the central hub 160.

Figure 5 is a cross-sectional view through the omniwheel 140. The roller axle 195 can be seen more clearly extending through the support 180 and retaining a pair of rollers 190 on either side of the support 180. Each roller 190 is generally cylindrical or annular in shape. Each roller 190 has a circular major face 200 and an opposing circular minor face 210. A wall 220 extending between the major face 200 and the minor face 210 provides a rolling surface for the roller 190. The wall 220 may extend between the major face 200 and the minor face 210 linearly, effectively defining a tangent of the circumference C. However, the wall 220 may also be non-linear, defining an arc of the circumference C.

As can be seen in Figure 5, the pair of rollers 190 is arranged symmetrically about the support 180 , with the major faces 200 positioned proximate the support 180 and the minor faces 210 positioned distal from the support 180.

It will also be appreciated that irrespective of the direction of rotation of the omniwheel 140 , the curved shoulder 230 defined by the intersection of the minor face 210 with the wall 220 is the region of the roller 190 which will first contact with the surface 30. As can best be seen in Figure 5, the rolling length Li of each roller 190 is the same as the rolling length L ₂ between rollers 190 of adjacent pairs and is equal to the rolling distance L ₃ between rollers 190 of the same pair. This provides for reduced disturbance in ride experience compared with arrangements where these distances are unequal.

Figure 6 is a close-up sectional view of the pair of rollers 190 mounted on the support 180. As can be seen, the support 180 is retained on to the shoulder (not shown) by means of bolts 167 which are received within the threaded apertures (not shown) provided on the outwardly-facing surface of the shoulders (not shown). A through -bore 235 extends through each support 180 and receives the roller axle 195. Bearings 240 are located on the outer surface of the roller axle 195 which in turn receive a roller 190.

Roller Deformation

Each roller 190 has a plurality of roller apertures 250 extending from the minor face 210 through the roller 190 to the major face 200. The provision of the roller apertures 250 facilitates deformation of the roller 190 when non-tangential contact occurs between the roller 190 and the surface 30. In particular, deformation of the roller 190 in the vicinity of the curved shoulder 230 is facilitated by the roller apertures 250 to improve ride quality by reducing noise and shock. In embodiments, the deformation may also be achieved through deformable structures on the surface of the rollers 190 (such as bumps or castellations) and/ or having a deformable inner portion (such as a foam inner).

Axial Displacement

In one embodiment, springs (such as Belleville or wavy washers not shown) are provided which are located between the support 180 and the major face 200 of each roller 190. The spring urges each roller 190 along the roller axle 195, along its axis in the direction Di, D2, respectively, away from the support 180. As the roller 190 contacts with the surface 30 , the roller can deflect along the roller axle towards the support 180 , thereby also reducing any noise and shock. It will be appreciated that a second spring (not shown) may be added between the minor face 210 and a retaining clip 260 to retain the roller 190 at a desired axial position on the roller axle 195 in order to further reduce noise and vibration. Allowing axial displacement also helps alleviate the following problem: if there is wear to one set of omniwheel rollers, then the effective rolling diameter may differ from the opposing omniwheel (that would be seen to share a common major axis of rotation, or be on the same axle). This would cause the drive ratio to differ between one side and the other. Alternatively, for a four-wheel drive system, the front and back wheel drivetrain ratios could differ from the rolling diameter ratios. Under or over-inflation of the front pneumatic tyre could cause this. The axial displacement and spring (such as belleville washer) arrangement serves to provide allowance for ratio mismatch, as the axial displacement of an individual roller would prevent potential slippage of the roller on the ground due to major axis rotation of the omniwheel. When contact with the ground moves onto the next roller, then the previous one can return to its neutral position or mid-point. Also, the movement in the axial direction helps to displace built up debris.

Radial Displacement

In one embodiment, the support 180 is coupled with the central hub 160 using a deformable coupling such as a compressible pad and/ or using springs (such as leaf springs). Such a coupling then allows the rollers 190 themselves to deflect radially inwards towards the central axle 170 and/ or to pivot about shoulder 165 in order to reduce noise and shock. Also, the movement in the radial direction and/ or pivoting helps to displace built up debris.

It will be appreciated that each of those mechanisms are not mutually exclusive and may be combined to provide the required amount of deflection and/ or deformation to reduce impact due to the deviation between the rollers 190 and the underlying surface.

Although in this embodiment each roller 190 is made from an incompressible material, such as an elastomer, it will be appreciated that this need not be the case and that the roller 190 may instead be made from a compressible material or made of a combination of compressible and incompressible materials. For example, the roller 190 may be formed from an inner core of compressible foam which is surrounded by an

incompressible elastomer. Having an incompressible outer coating helps to improve the lifetime of the roller 190.

Debris Removal

Figures 7A to 7C illustrate a debris removal device 300 of one embodiment. As can be seen in the perspective view of Figure 7A, the debris removal device 300 is located in the converging void between minor faces 210 of adjacent rollers 190. The debris removal device 300 is located on the end of the axle 195 of at least one of the rollers 190 and typically fixed to prevent rotation. The debris removal device 300 is dim en sioned to fit between the adjacent rollers 190 without jamming during deflection of those rollers 190. The debris removal device has a pair of chisel members 310 extending from a fixing 320 which receives the axle 195 and into the converging void between the adjacent roller 190. The chisel members 310 extend from the fixing radially outward to the curved shoulder 230. The parts of the debris removal device 300 bearing against the minor faces 210 are generally flat. The exposed faces of the debris removal device 300 are generally sloped. In this example, the exposed faces are generally curved.

As seen in Figure 7B, in operation, debris 330 may become attached to the minor faces 210 or otherwise gather in the converging void between adjacent rollers 190.

As seen in Figure 7C, as the rollers 190 rotate about the axle 195, the debris 300 contacts the chisel member 310 and is gathered by that chisel member 310. Continued rotation of the rollers 190 causes the debris 300 to be moved along the chisel member 310 and ejected from its tip 340 , clear of the rollers 190.

Hence, it can be seen that the debris removal device 300 provides a hard projection / edge (which doesn't need to be sharp) that can effectively 'carve' off any accumulated debris as the rollers rotate during use. The projection/ edge will typically be fixed and non-rotating. The rotation of the rollers rotates the debris into the path of the projection/ edge.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.