WO2010139936A1

WO2010139936A1 - Ambulatory aid with a power unit

Info

Publication number: WO2010139936A1
Application number: PCT/GB2010/001048
Authority: WO
Inventors: James Richard Usherwood
Original assignee: The Royal Veterinary College
Priority date: 2009-06-01
Filing date: 2010-05-28
Publication date: 2010-12-09
Also published as: GB0909368D0

Abstract

A device comprising an ambulatory aid, the device comprising a distal end, a load, a first portion positioned at, or close to the distal end and adapted to allow the device to move along a surface, a second portion spaced apart from the first portion and the distal end and adapted to allow a user to be attached to, or hold the device, and a power unit operably connected to the first portion, the device having a deployed position in which the device is moveable, and is supported by the user, movement of the device being powered by the power unit.

Description

AMBULATORY AID WITH A POWER UNIT

This invention relates to a device comprising an ambulatory aid, a method for assisting humans or animals to walk, and a method of walking.

There are many circumstances under which a person may require assistance in walking. One such situation is after a person has had one or both legs amputated resulting in the loss of ankle and/or knee function in the amputated leg.

A second circumstance where it may be desirable to assist a person to walk is after that person has had, for example, a stroke or other illness, and needs to undergo a rehabilitation process before being able to walk properly again.

There is also a need to assist some frail people to walk.

A wheelchair may be used to allow such people to move around, but generally a wheelchair can lead a user of the wheelchair to feel socially isolated, since the person is usually positioned at a lower level than other people. Walking frames may also be used but tend to support a person in a generally upright position rather than assist in the walking process. In other words, a walking frame will steady and support a person whilst that person is walking, but will not help a person maintain natural body dynamics.

According to a first aspect of the present invention there is provided a device comprising an ambulatory aid, the device comprising a distal end, a load, a first portion positioned at, or close to the distal end and adapted to allow the device to move along a surface, a second portion spaced apart from the first portion and the distal end adapted to allow a user to be attached to, or hold the device, and a power unit operably connected to the first portion, the device having a deployed position in which the device is moveable, and is supported by the user, movement of the device being powered by the power unit.

According to a second aspect of the present invention there is provided a method for assisting a human or animal to walk comprising the steps of: applying a load to the human or animal thereby affecting the inertia of the human or animal.

The method may comprise the further step of applying a load to the human or animal thereby affecting the effective weight of the human or animal. In embodiments of the invention where both the inertia and the effective weight of the human or animal are affected, the inertia and the effective weight may be affected independently of one another.

According to a third aspect of the present invention there is provided a method of walking using the device according to the first aspect of the invention comprising the steps of: supporting the device in its deployed position and walking whilst supporting the device.

The present invention has been developed through an understanding of the mechanical process involved when a biped, such as a human, walks.

There are various models used to try to understand. walking motion in bipeds. One such model is known as the compass-gait model which is the most reductionist mechanical model for bipedal walking.

According to this model, bipedal walking may be viewed as a vaulting gait in which the centre of mass (CoM) of the walker passes over a stiff stance leg acting as an inverted pendulum, while the other leg of the walker acts as a swing leg, and swings forward as a pendulum. Using this model, it can be predicted that any biped, including a human, has a maximum walking speed which is constrained by simple mechanics. If the walker walks too fast, or with too high a step length, gravity will fail to keep the stance foot attached to the floor, and the walker will have to break into a run.

Whilst the compass-gait model can be used with great accuracy on, for example ducks, which walk as inverted pendulums with near passive swing legs up to relative velocities of around 0.5 (relative to the top speed theoretically possible with stiff legs and infinitely short steps), top walking speeds in humans cannot be achieved with passive swing legs. Humans, while still constrained by compass-gait mechanics, are able to extend their envelope of walking speeds by using relatively high step frequencies. This means that the capacity to drive the swing leg forward by walking humans allows near passive vaulting of the CoM at walking speeds 4/3 greater than those possible with a passive swing leg.

Humans are able to increase their maximum walking speeds by driving their swing limbs at above natural pendular frequencies. From the combination of the limitations imposed by compass-gait mechanics, and the energy cost of driving swing limbs, predictions concerning maximum walking speeds can be made. Anything restricting the driving of the swing limb, for instance massive boots or massive lower limb prosthetics can be predicted to reduce the maximum walking speed.

Conversely, anything enhancing the driving of the swing limb, for example spring-like torques about the hip or low mass prosthetics, should permit higher walking speeds.

By means of the invention a load that is spaced apart from a user may be applied to the body of the user. This is geometrically very different from that associated with adding a mass to a body. If a mass is added to the body of the user, the user's body and added mass would arc over the stance leg with each step. Thus, when a mass is added to the body of a user, the geometry of the centre of mass path remains unchanged, and so the compass-gait top walking speed is unchanged.

By means of the invention, a load which is spaced apart from the centre of mass of the user may be applied to the user thereby changing the inertia of the user.

When the user is supporting the device, forces are applied to the user via the load, in addition to gravitational forces. This means that the inertia of the user is changed.

The device according to the first aspect of the present invention allows a manipulation of top walking speeds due to two mechanisms: i) an alteration in the effective weight of the user; and ii) a reduction in fluctuations of body speed of the user.

Because a device according to the invention must be supported by the user in its deployed position in which it is moveable, the device may be able to alter the effective weight of the user. If the effect of the device is to increase the effective weight of the user, then higher top walking speeds may be achieved by the user than would be the case if the user were not using the device, but at the expense of higher loads applied to the user's legs. If the effect of the device is, on the other hand, to reduce the effective weight of the user, the user will have to withstand lower loads on his legs than would be the case if he were not using the device, but at the expense of achieving lower top walking speeds. An alteration in the effective weight of the user may be achieved because the load of the device remains relatively level and therefore imposes a relatively constant vertical force on the user thus increasing or decreasing the effective weight of the user.

The reduction in fluctuations of body speed of the user may be achieved because the inertial resistance supplied by the device resists changes in the horizontal speed of the user thus reducing fluctuations in the body speed of a user.

The device according to the present invention differs from, for example, known walking frames because, inter alia when the device is in the deployed position, the device must be supported by the user. Known walking frames are designed to support the user rather than requiring the user to support the walking frame. Because the device according to the present invention must be supported by the user, a load may be applied to the body of the user as described above. It is this load that changes the effective weight of the user and enables higher walking speeds to be achieved by the user or lower leg loads to be applied to the user than would be the case if the user were not using the device, depending on the position of the load.

The device may be regarded as a load that can be applied to a user in order to assist the user to walk. The position of the load, in one embodiment, is between the first portion and the second portion. When the load is in this position, the effective weight of a user is increased while the user is using the device. This embodiment of the invention may be useful in providing an ambulatory aid for, for example, an amputee, who is able to withstand higher legs loads in order to achieve a higher walking speed.

In another embodiment, the distance between the second portion and the load is greater than the distance between the first portion and the second portion. If the second portion is positioned at, or close to a proximal end of the device, the distance between the proximal end of the device and the load will be greater than the distance between the proximal end and the first portion. This may be achieved, for example, by positioning the load between the first portion and the, or a, distal end of the device. In this position, the device will have the effect of reducing the effective weight of a user. This embodiment of the invention may serve as an ambulatory aid for assisting a person who has had, for example, a stroke or other illness and needs to undergo a rehabilitation process to walk again. Such a person may not be able to withstand leg loads that would normally be experienced by the person if trying to walk unaided. In embodiments of the invention the load may be positioned, in use, directly above or below the first portion. In such embodiments there will be no, or substantially no, net vertical load component applied to a user when supporting the device. In such an embodiment, the effective weight of the user may be substantially unchanged. The inertia of the load may reduce fluctuations in the walking speed of a user. In use, if the user is pushing the device so that the device is in front of the user, then the device may produce a pulling force when the user slows down, and a pushing force when the user begins to accelerate.

The load will have the effect of reducing fluctuations in the walking speed regardless of whether it applies a positive, negative or substantially zero net vertical force to the user.

The effect of the load on the user will therefore vary depending on its position. If the load is positioned near to the second portion of the device, then the effect will be to alter the effective weight of a user. However if the load is positioned near to the first portion of the device, there will be little change in effective weight of a user using the device, but there will be a change in inertia.

The device as a whole, when in its deployed position, will of course contribute to the load applied to the user. However, properties of the device and/or the positioning of any additional components defined herein as "the load" determine the location of the acting point of the overall load. Thus the load as defined herein may comprise one or more components that are separate to the overall device. Alternatively the load may be viewed as forming part of the device.

Any reference herein to the position of load should be taken to mean the position of the acting point of the overall load of the device, whether or not a main component of the load is the device itself, or one or more components formed separately from the device.

The device may comprise an adjuster for adjusting the position of the load.

The adjuster may be in the form of a slider, for example, although other means for adjusting the positioning of the load may be used.

Because the device is powered by the power unit the user has to expend little or no energy in moving the device along a surface. The user can however control the direction of travel of the device. Some embodiments of the invention may comprise a speed control and/or an on/off switch. In such embodiments, the user is able to control the speed at which the device travels, and switch the device on and off.

Preferably the power unit comprises a motor which is adapted to drive the device, although other power units could be used.

The motor may be powered by any convenient means, and may for example be battery operated.

The motor may comprise a brushless DC (electronic-commutated) hub motor powered by a lead acid battery. In other embodiments different types of motor and/or battery may be used.

The motor may be positioned within the first portion of the device.

By positioning the motor within the first portion of the device, it is protected from the environment by the first portion. The motor may be formed separately to, or integrally with the first portion of the device.

The load may comprise the power unit. In particular, the load may comprise a battery forming part of the load.

The load may comprise more than one component. In embodiments where the load comprises the power unit, the load may further comprise a component in addition to the power unit. This may be useful in situations where a high load is required which is greater than that which can be contributed by the power unit.

In some embodiments of the invention the device further comprises a tuner adapted to adjust the mass of the load and/or its position. In other words the magnitude of the load and/or the positon of the acting point of the load may be altered as necessary by the tuner. This enables the walking speed of the user, the loading of the legs and the stability of the device to be controlled since both the effective weight of the user and the inertia resisting horizontal velocity fluctuations can be altered to suit the requirements of a user.

In embodiments of the invention comprising an adjuster, the adjuster may serve as the tuner, or may form part of the tuner. Although the device as a whole, when in its deployed position in which it is supported by a user, will contribute to the load applied to the user, the positioning of the power unit, and in particular the battery, in an embodiment of the invention comprising a battery, will determine the acting point of the load applied to the user.

Thus, in embodiments of the device comprising a battery, the position of the acting point load may be taken to be the position of the battery. However it is to be understood, that the entire device will contribute to the load applied to the user when the device is in the deployed position and is being supported by the user.

The second portion may comprise a handle. This allows a user to grasp or otherwise hold the handle in order to support the device in its deployed position, and operate the device in order to be assisted in walking.

Alternatively, however, the second portion may comprise a strap adapted to fit around a part of the user's body such as the user's waist. In such an embodiment, a user would not have to actively hold the device, but could be attached to the device by the strap and thus be assisted in walking. In other embodiments, the strap could be adapted to fit around another part of the user's body, for example a wrist or arm.

In other embodiments the device may comprise a strap adapted to extend over a shoulder of the user or a parachute/climbing style between the leg harness.

A user of the device may position the device in front of him in which case the device will pull the user during use of the device (or the user will push the device), or may position the device behind him in which case the device will push the user during use of the device (or the user will pull the device).

The device may be adapted to move along any desirable surface or ground such as a floor, a pavement, or rough terrain, for example.

The first portion may comprise a wheel rotatably connected to the device.

In an alternative embodiment, the first portion comprises two wheels connected to one another by an axle. The axle may extend substantially at right angles to the longitudinal axis of the device. Such an arrangement may be more desirable in certain conditions such as where the device may be required to move along an uneven surface such as bumpy terrain, or to provide lateral stability for rehabilitation (e.g. after stroke or amputation) training.

In another embodiment, the first component may comprise two pairs of wheels each pair of wheels connected to one another by an axle, the axles being spaced apart from one another. In such an embodiment, each axle may extend substantially at right angles to the axis of the device. Such an arrangement provides further stability to the device and may be particularly useful when there is a need to provide lateral stability for rehabilitation training.

In such an embodiment, the device comprises two distal ends spaced apart from one another, each pair of wheels being positioned at or close to a respective distal end of the device. In such an embodiment, the user will be positioned between the two distal ends of the device when the device is in the deployed positioned, and will hold, or be attached to a middle portion of the device.

In embodiments of the invention where the first portion comprises a component other than a wheel, for example, a roller, castor, or tank track, the first portion may comprise two or more of such components.

The device may comprise any number of first portions as appropriate for the conditions under which the device will be used. For example, in an embodiment where the first portion comprises a wheel, the device may comprise three wheels. Such an embodiment may help to provide stability and manoeuvrability to the device.

The device may be adapted to pivot at or close to the first portion. In embodiments of the invention where the first portion comprises one or more wheels, the device may be adapted to rotate, or pivot, about an axis of rotation of the one or more wheels. In such an embodiment, the load will also rotate about the axis of rotation of the one or more wheels.

Alternatively, or in addition, the device may comprise a hinge positioned between the first portion and the second portion. In such an embodiment, the device may pivot or rotate about the hinge, thus allowing the load to rotate about an axis that is different to the axis of rotation of the one or more wheels forming the first portion. Embodiments of the invention will now be further described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic representation of a device according to an embodiment of the present invention for assisting a human or other animal to walk;

Figure 2 is a schematic plan view of the device of Figure 1 ;

Figure 3 is a schematic representation of the device of Figures 1 and 2 showing the device being pulled by a user (or the user being pushed by the device);

Figure 4 is a schematic representation of the second embodiment of the invention including a speed controller;

Figure 5 is a schematic representation of a third embodiment of the invention in which the load is positioned at a distal end of the device;

Figure 6 is schematic plan view of a fourth embodiment of the invention in which the device comprises a pair of wheels connected by an axle;

Figure 7 is a schematic representation of a fifth embodiment of the invention comprising two loads each positioned between a wheel and a proximal end of the device; and

Figure 8 is a schematic plan view of a sixth embodiment of the invention comprising two pairs of wheels and two loads, each load being positioned at a distal end of the device;

Figure 9 is a schematic view of a seventh embodiment of the invention comprising two loads and two tuners;

Figure 10 is a schematic view of an eighth embodiment of the invention comprising a hinge.

Referring to Figure 1 and 2, an embodiment of a device according to the present invention is designated generally by the reference numeral 20. The device comprises a distal end 50, and a proximal end 52. The device further comprises a first portion in the form of a wheel 22 adapted to allow the device to move along a surface, and a second portion in the form of a handle 24 adapted to allow a user, such as a human, 26 to attach to, or to hold the device. The device has a deployed position as shown in Figure 2 in which the device is moveable and is supported by the user 26.

The device 20 further comprises a power unit 28 which in this embodiment comprises a motor 30 powered by a battery 32. The power unit 28 is operably connected to the wheel 22. In this embodiment the battery 32 may be regarded as the load 34. The device further comprises a load 34 which may be separate to the battery 32 or may partly consist of the battery. Because the user 26 has to support the device 20 in its deployed position a downward force 40 is applied to the user 26 which increases the effective weight of the user. In addition, the inertia created by the device 20 reduces fluctuations of body speed of the user 26. The user is thus able to walk more quickly than he would unaided, whilst expending less energy.

In the illustrated embodiment, the load of the device 20 has a fixed position between the handle 24 and the wheel 22 of the device 20. However, in other embodiments, the position of the load may vary. Because the load 34 is positioned between the handle 24 and the wheel 22, the effect of the device 20 on a user when the device is in the deployed position and is supported by the user is to increase the effective weight of the user. This enables a user to walk more quickly than he would do unaided, but results in higher loads being applied to the legs of the user.

In this embodiment the motor is incorporated into the wheel 22 although the motor could be positioned elsewhere on the device.

In this embodiment, the handle 24 is positioned at, or close to the proximal end 52 of the device, and the wheel is positioned at, or close to the distal end of the device.

In this embodiment, the wheel 22 is mounted on an axle 36 about which the wheel is rotatable. In addition, the device 100 is adapted also to pivot or rotate about the axle 36. However, in other embodiments, the device may comprise a hinge which allows the device and hence the load to pivot/rotate about an axis that is different to the axis of rotation of the wheel or wheels. Such an embodiment is shown schematically in Figure 10.

Figures 1 and 2 show the device 20 being held by a user such that the device is positioned in front of the user and the user is pulled by the device in order to walk. However, as shown in Figure 3, the device could also be held behind the user such that the user will be pushed by the device in order to walk.

Turning now to Figure 4, a second embodiment of the device according to the invention is designated generally by the reference numeral 100. Parts of the device 100 which correspond to parts of the device 20 have been given corresponding reference numerals for ease of reference.

The device 100 comprises a support belt 110 attached to the device 100 at or close to the proximal end 52 of the device. The support belt 110 replaces the handle 24 of the device 20. Because the device comprises a support belt, the device may be attached to a user 26 without the user having to actively hold the device. This can be useful when the user is weak, for example perhaps because the user is recovering from a severe illness or to leave the hands free for other activity.

The device 100 further comprises a speed controller 20 which may be operated by the user 26 in order to control the speed of the device.

Turning now to Figure 5, a third embodiment of the invention is designated generally by the reference numeral 200. Parts of the device 200 that correspond to parts of the devices 20, 100 have been given corresponding reference numerals for ease of reference.

In this embodiment, the load 34, in the form of a battery 32, is positioned between the wheel 22 and a distal end 50 of the device. In other words rather than the load 34 being positioned between the proximal end 52 and the wheel 22 and thus being closer to the proximal end 52 of the device than the wheel 22, the load 34 is positioned closer to a distal end 50 of the device 200 such that the wheel 22 is closer to the proximal end 52 of the device than is the load 34. In this embodiment, the positioning of the load 34 means that the effective weight of the user 26 is reduced. This means that the user will experience lower legs loads when using the device, but as a consequence will not be able to achieve as high walking speeds as would be the case if the user were not using the device 200.

When releaming to walk, for instance after a stroke or amputation, weight and lateral support during slow walking are often applied by the provision of parallel bars, or by a vertically lifting harness in conjunction with a treadmill. Such apparatus must typically be used in doors, usually at a hospital or clinic. However by means of the present invention and particularly the embodiments described above with reference to Figures 5, 6 and 8, a person learning to walk may exercise outside, or at any desirable location. In addition the speed, dynamics (passive vaulting with correct matching between vault and swing leg), manoeuvrability (turning) and stability requirements (lateral stability) of walking can be reintroduced incrementally.

Figure 6 is a schematic plan view of a fourth embodiment of the invention designated generally by the reference numeral 300. Parts of the device 300 that correspond to parts of the devices 20, 120 and 200 have been given corresponding reference numerals for ease of reference.

In the embodiment, the device comprises two wheels 22 connected to one another by axle 36. The axle 36 extends substantially perpendicularly to the longitudinal axis of the device. Such an embodiment may be useful when it is required to provide lateral stability for example for rehabilitation training or for the frail.

Turning now to Figure 7, a fifth embodiment of the invention is illustrated schematically, and designated generally by the reference numeral 400. Parts of the device 400 that correspond to any of the other devices 20, 120, 200, 300 have been given corresponding reference numerals for ease of reference.

In this embodiment, the device 400 comprises two wheels 22.

In this embodiment, the device 400 comprises two loads 34. Each load 34 is positioned between the proximal end of the device 400 and a respective wheel 22.

Turning to Figure 8, a sixth embodiment of the invention is illustrated schematically and designated generally by the reference numeral 500. Parts of the device 500 that correspond to any of the other devices 20, 120, 200, 300, 400 have been given corresponding reference numerals for ease of reference. In this embodiment the device 500 comprises two pairs of wheels 22. Each wheel 22 in a pair 38 is joined to the other wheel forming that pair by an axle 36. The axles 36 are substantially parallel to one another, and are substantially perpendicular to the longitudinal axis of the device. In this embodiment, the user 26 holds, or is attached to the device 500 at a middle portion of the device 500. The device thus has two distal ends 50. Proximal end 52 is formed between the two distal ends 50. In this embodiment, the device 500 comprises two loads 34. Each load is positioned between the proximal end of the device 500 and a respective pair of wheels 22.

Referring to Figure 9, a seventh embodiment of the invention is illustrated schematically and designated generally by the reference numeral 600. Parts of the device 600 that correspond to any of the other devices 20, 120, 200, 300, 400, 500 have been given corresponding reference numerals for ease of reference.

In this embodiment the device 600 comprises two wheels 22, although in alternative embodiments the device may comprise two pairs of wheels 22. The device further comprises two loads 34. Associated with each load 34 is a tuner 60 adapted to adjust the position and/or mass of a respective load 34. In this embodiment each tuner 60 comprises a sliding rail 62 along which a respective load 34 may be moved. By means of the tuners 62, therefore, the distance between each load 34 and the proximal end 52 of the device 600 may be varied. In particular, each load 34 may be moved between a first position in which the distance between the load 34 and the proximal end 52 is greater than the distance between a respective wheel 22 and the proximal end 52, and a second position in which the distance between the load 34 and the proximal end 52 is less than the distance between the respective wheel 22 and the proximal end 52. Each load 34 may be moved to any desired location along a respective sliding rail 62.

This means that the device as illustrated in Figure 9 can be adjusted to reduce the effective weight of the user when each load is the first position, increase the effective weight of the user when each load is in the second position or maintain the effective weight of the user substantially unchanged when each load is positioned substantially directly over the wheels 22.

Regardless of the position of the load, the inertia of the user will be changed through use of the device 600.

In addition to being able to adjust the position of each load 34, each tuner 62 also enables the mass of each load to be adjusted by either allowing additional mass to be added to the load 34, or allowing mass to be removed from the load 34.

Referring to Figure 10, an eighth embodiment of the invention is illustrated schematically and designated generally by the reference numeral 700. Parts of the device 700 that correspond to any of the other devices shown in Figures 1 to 8 have been given corresponding reference numerals for ease of reference.

The device 700 comprises a hinge 710 at, or near to the distal end 50 of the device. The hinge enables the device 700 to pivot about the hinge 710 and thus enables the load 34 to pivot about an axis that is different to the axis of rotation of the wheel or wheels 22.

A device according to embodiments of the present invention may thus be used to increase the top walking speeds of users who are relatively strong and are therefore able to withstand higher leg loads.

A device according to embodiments of the present invention may be used to act as a rehabilitation aid to ease patients back into walking who have suffered a stroke for example. By altering the position of the load 34 the device is able to exert a range of forces on the user thus enabling the user to walk at varying walking speeds and to experience varying leg forces.

A device according to the present invention may also be helpful in enabling frail people to walk stably by reducing loads experienced on the legs of the person and adding stability. Unlike known walking frames, the device according to the present invention would allow near normal walking mechanics to be experienced by such a frail person.

Claims

1. A device comprising an ambulatory aid, the device comprising a distal end, a load, a first portion positioned at, or close to the distal end and adapted to allow the device to move along a surface, a second portion spaced apart from the first portion and the distal end and adapted to allow a user to be attached to, or hold the device, and a power unit operably connected to the first portion, the device having a deployed position in which the device is moveable, and is supported by the user, movement of the device being powered by the power unit.

2. A device according to Claim 1 wherein the load is positioned between the first portion and the second portion.

3. A device according to Claim 1 or Claim 2 wherein the distance between the second portion and the load is greater than the distance between the first portion and the second portion.

4. A device according to any one of the preceding claims wherein the load is positioned, in use directly above, or below the first portion.

5. A device according to any one of the preceding claims comprising an adjuster for adjusting the position of the load.

6. A device according to any one of the preceding claims wherein the power unit comprises a motor.

7. A device according to any one of the preceding claims wherein the power unit comprises a battery for powering the motor.

8. A device according to Claim 7 wherein the load comprises the battery.

9. A device according to any one of the preceding claims further comprising a tuner adapted to adjust the mass of the load and/or its position.

10. A device according to any one of the preceding claims wherein the second portion comprises a handle.

11. A device according to any one of the preceding claims wherein the first portion comprises a wheel rotatably connected to the device.

12. A device according to any one of the preceding claims wherein the first portion comprises two wheels connected to one another by an axle which axle extends substantially at right angles to the axis of the device.

13. A device according to any one of the preceding claims comprising two pairs of wheels, each pair of wheels being connected to one another by an axle, which axles are spaced apart from one another, each of which axles extends substantially at right angles to the longitudinal axis of the device.

14. A method for assisting a human or animal to walk comprising the steps of: applying a load to the human or animal thereby altering inertia of the human or animal.

15. A method of walking using a device comprising an ambulatory aid, the device comprising a distal end, a load, a first portion positioned at, or close to the distal end and adapted to allow the device to move along a surface, a second portion spaced apart from the first portion and the distal end and adapted to allow a user to be attached to, or hold the device, and a power unit operably connected to the first portion, the device having a deployed position in which the device is moveable, and is supported by the user, movement of the device being powered by the power unit, the method comprising the step of: supporting the device in its deployed position; and walking while supporting the device.