GB2470830A

GB2470830A - Apparatus with wheel magnets and method for driving along metal post

Info

Publication number: GB2470830A
Application number: GB1009155A
Authority: GB
Inventors: Mehmet Ali Erbil; Siddharth Odedra; Stephen Dominic Prior
Original assignee: MIDDLESEX UNIVERSITY HIGHER ED
Current assignee: MIDDLESEX UNIVERSITY HIGHER ED
Priority date: 2009-06-01
Filing date: 2010-06-01
Publication date: 2010-12-08
Anticipated expiration: 2030-06-01
Also published as: GB201009155D0; GB0909358D0; GB2470830B

Abstract

An apparatus 30 for moving across a ferromagnetic surface and for holding a payload on or near said surface comprises a chassis 32 on which is mounted a drive unit 34, 36, a control unit and a mount for a payload. The drive unit 34, 36 comprises an outer surface for engagement with said ferromagnetic surface. Permanent magnets 52 are arranged on the outer surface. This may be the outer rim of a drive wheel 42. The apparatus 30 may be used for deploying a surveillance camera on a lamp-post.

Description

APPARATUS AND METHOD FOR MOVING ACROSS A

FERROMAGNETIC SURFACE

FIELD OF THE INVENTION

The present invention relates to an apparatus for moving across a ferromagnetic surface, to a kit comprising the apparatus and to a method of moving the apparatus across a ferromagnetic surface.

BACKGROUND TO THE INVENTION

Street furniture provides a readily-available means to temporarily mount portable surveillance equipment. One example of such portable surveillance equipment is the SHERPA surveillance system sold by Norton integrated Systems Ltd. The SHERPA system comprises a two-part deployment unit that must be connected together around a lamp post, and a two-part camera unit which must also be connected together around the lamp post. The deployment unit drives the camera unit to position, whereupon the camera unit attaches to the lamp post. The deployment unit is then driven down the lamp post for retrieval, leaving the camera unit in place. Disadvantages with the SHERPA system include: not being readily hand portable, multiple parts requiring two person assembly at point of use, high weight (total 35 kg), long installation time (typically 20 minutes) and high cost (18k -�25k). Furthermore, the SHERPA system can only climb and descend circular shaped lamp posts, and only those that are free of any obstacles such as signage.

Security forces and personnel may require deployment of such temporary surveillance equipment more rapidly, covertly and easily. Similarly, scene of crime officers may wish to use street furniture to take pictures/video as evidence of a crime scene or road traffic accident. The time and cost of conventional apparatus, such as the SHERPA system, may preclude its widespread use.

Other options are open to security forces and personnel (e.g. helicopter surveillance and purpose built vehicles with telescopic masts), but these are yet more expensive and slow to deploy. -2-

SUMMARY OF THE INVENTION

According to the present invention there is provided an apparatus for moving across a ferromagnetic surface and for holding a payload on or near said surface, which apparatus comprises a chassis on which is mounted a drive unit, a control unit and a mount for a payload, said drive unit comprising an outer surface for engagement with said ferromagnetic surface and on which is mounted, or which outer surface comprises, a plurality of permanent magnets. One advantage of this arrangement is that the weight of the apparatus can be held in a desired position by one permanent magnet per wheel (e.g. on a vertical/inclined surface, or when the apparatus is hanging from a surface), but that the drive unit can rotate the wheel over the surface using relatively liftie power, i.e. the permanent magnets don't become stuck' to the surface. We believe that this may be due to the way in which the wheel brings each permanent magnet gradually into a position of maximum attraction with the surface, and then gradually out of that position ready to hand over' to the next magnet on the rim.

In some aspects the apparatus is of relatively small size (e.g. 400mm by 100mm by 140mm) and weight (e.g. 2.5 kg). We have found that the arrangement of magnets on an apparatus of such a size and weight permits it to be emplaced on and removed from ferromagnetic surfaces by hand. This enables the apparatus to be carried, for example, by security or military personnel and deployed quickly and easily. In some cases, it is possible for a single operator to deploy the apparatus on a lamp post for example, in less than five minutes, and in certain aspects in about one minute.

We have also found that the arrangement of magnets works well on both flat surfaces and curved surfaces. Furthermore the apparatus can climb and descend street furniture that has signage attached with stainless steel banding.

Once at the correct position, the permanent magnet or magnets in contact with the surface is able to hold the apparatus in position without requiring any power source.

The apparatus can be used for a variety of purposes including: mounting on and/or inspection of any structure comprising a ferromagnetic surface, such as buildings, bridges, ships, masts, pipelines (external and internal) and oil rigs (above and below the water surface); mounting on and/or inspection of street furniture comprising ferromagnetic materials, including street furniture having various shapes and with or without a taper. The apparatus could also be used to carry and mount temporary wireless transmission equipment on remaining ferromagnetic structures following a natural disaster.

Preferably, said plurality of permanent magnets is arranged around said drive unit such that each permanent magnet has an outwardly oriented face and that, in use, each permanent magnet is driven through a position in which said outwardly oriented face is either parallel with or tangential to said ferromagnetic surface.

Advantageously, in use, rotation of said drive unit causes said outwardly oriented face to rotate relative to said ferromagnetic surface, so that each permanent magnet is brought gradually into maximum attraction in said position with said ferromagnetic surface and gradually out of said maximum attraction. This enables the drive unit (e.g. comprising a wheel) to be driven with relatively low power, whilst at the same time maintaining a weight bearing function so that the apparatus remains adhered to the ferromagnetic surface.

Preferably, said permanent magnet comprises a north and a south pole that is presented to (e.g. faces) said ferromagnetic surface during use.

Advantageously, each permanent magnet is mounted in a housing, which housing is mounted on said outer surface. One advantage of this it that magnets can be easily removed and replaced if needed.

Preferably, said plurality of magnets is arranged in a substantially continuous track around said outer surface. In certain aspects, the housings holding the magnets may be in abutment with one another around the outer surface.

Advantageously, the centre of gravity of said apparatus acts through or near a centre line defined by said substantially continuous track. Tn this way the chance of -4-the apparatus releasing from the ferromagnetic surface is reduced. n other aspects the centre of gravity is close to the ferromagnetic surface but with a clearance to enable obstacles to be traversed.

Preferably, said drive unit comprises a faceted ring, each facet being substantially flush with a respective permanent magnet. One advantage of this is that each permanent magnet can be brought very close to the ferromagnetic surface, maximising the attractive force therebetween.

Advantageously, the apparatus further comprises a high coefficient of friction material on said outer surface for facilitating traction between said wheel and said ferromagnetic surface. In certain aspects this material could be a thin rubber or silicone film on the aforementioned faceted ring. In other aspects separate tracks or areas of high friction material could be provided on the outer surface.

Preferably, said mount comprises an arm having a proximal end mounted on said apparatus and a distal end having an effector to which a camera, sensor or other device may be mounted. In other embodiments the apparatus may be provided with a permanent camera and/or sensor.

In some embodiments the apparatus is emplaceable on and removable from said ferromagnetic surface by hand. The apparatus may also be portable by hand between uses.

Advantageously said control unit comprises a wireless transceiver for receiving commands from a user-operable remote control unit.

In some embodiments, said drive unit comprises a wheel having a rim around which said plurality of permanent magnets is mounted.

According to another aspect of the present invention there is provided a kit comprising an apparatus as set out above and a remote control unit for controlling said apparatus. -5-

According to another aspect of the present invention there is provided a method of moving an apparatus across a ferromagnetic surface, which method comprises the steps of: (a) emplacing an apparatus as set out above on said surface; and (b) moving said apparatus across said surface by driving said drive unit.

In certain aspects the apparatus is a robotic platform which is able to climb up and down any verticallinclined ferromagnetis surfaces. Designed with the intention of mainly climbing up lamp post and other street furniture, the platform is able to achieve this with a wheel or wheels configured to hold magnets on the outer circumference of the wheel. Motors which drive the platform up the vertical axis are mounted within the wheels to maintain the slim profile of the platform. The apparatus is able to operate wirelessly via a ground control unit by a single operator. Both the ground control unit and the appartus are able to operate in harsh weather conditions varying from snow, sleet, rain, sand storms and gale force winds. The platform can be adapted to carry various payloads for various applications such as surveillance purposes or as an inspection tool. The platform also has safety features such as automatic descend if the power of the unit drops below operational levels and safety straps which will keep it from falling in any another direction but down if the magnetic wheels fail.

In certain aspects the apparatus can be deployed by a single operator in less than five minutes.

Tn other aspects it can climb up vertical metallic street furniture.

In some embodiments the apparatus uses permanent magnets to attach and drive the platform up the verticallinclined surfaces.

A wheel configuration of the apparatus may have multiple magnets on its outer circumference.

In some aspects the wheel has a multi faceted face that is flush with the face of the magnets. -6-

The apparatus has a slim profile and is able to climb up a single side of a lamp

post, for example.

The apparatus can be remotely operated and has wireless telemetry.

The apparatus may be used by the Metropolitan Police Force Forensic Department for example to capture elevated images at the scene of a crime. The climbing mechanism is a key aspect of the system design as it allows it to climb up on any ferromagnetic surface of any shape and size. The platform is able to navigate up a lamp post via a wireless link to the operator. Video or still images are then transmitted back down to the ground station operator where he/she can control all the functions of the camera and platform.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the present invention reference will now be made by way of example only to the accompanying drawings in which: Fig. 1 is a schematic side view of a typical lamp post found in the UK and elsewhere; Fig. 2 shows examples of the typical variation in size and shape of lamp posts found in the UK and elsewhere; Fig. 3 is a schematic perspective view of an apparatus according to the present invention; Fig. 4A is a schematic side view of the apparatus shown in Fig. 3; Fig. 4B is a schematic reverse perspective view of the apparatus shown in Fig. 3; Fig. 4C is a schematic top plan view of the apparatus shown in Fig. 3; Fig. 5 is a side view of one of the wheels of the apparatus shown in Fig. 3; Fig. 6 is a schematic plan view of one of the permanent magnets used in the wheel of Fig. 5; and Fig. 7 is a schematic block diagram of the internal components of the control box of the apparatus of Fig. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS -7-

Referring to Fig. 1 a typical lamp post 10, found in the UK and elsewhere, comprises a flanged base 12, a post 14 and a bracket 16 to which a luminaire (not shown) is mounted. Some lamp posts do not have the flanged base 12 and the post continues to the ground level. A typical lamp post in the UK has a height of between about 6 m and 10 m. Lamp posts are most frequently constructed from a ferromagnetic material, usually steel, the external surface being painted for protection. According to our research, 98% of lamp posts in the Greater London area are constructed from steel, and the remaining 2% are constructed from other materials such as wood and concrete.

The flanged base 12 houses electrical connections accessible via a service door 18. Typically the height of the flanged base 12 is less than about 2 m and so the bottom end of the post 14 is easily accessible by hand. Signage 20 is often, although not always, attached to the post 14 by means of stainless steel banding (not shown).

The signage is usually mounted at a height of between about 2.5 m to 5 m, and is out of unaided reach.

The post 14 can be a wide range of shapes and sizes. For example, referring to Fig. 2 the post 14 can range in diameter between about 60 mm and 220 mm.

Furthermore, the post 14 can be of difference shapes, for example circular, hexagonal, or octagonal. Posts can also vary in diameter between the flanged base 12 and the bracket 16. For example a 12 m high lamp post may have a diameter near the flanged base of 220 nm-i reducing to 60 mm or less near the bracket 16. According to our research, 34% of lamp posts in Greater London are tapered, and the remainder are of constant diameter with height.

Referring to Fig. 3 and 4A to 4C an apparatus generally identified by reference number 30 comprises an aluminium chassis 32 on which are mounted a first drive unit 34, a second drive unit 36 (each independently driven in forward and reverse) and a control unit 38. An articulated arm (not shown) is mounted at a position 40 on a surface of the control unit 38. The articulated arm is described in greater detail below. The overall dimensions of the apparatus 30 (excluding the articulated arm) are about 400 mm by 100 mm by 140 mm (L x W x H), and the weight is approximately 2.5 kg. As such the apparatus 30 may be hand-held and carried about the person. -8-

The first and second drive units 34 and 36 are identical, and therefore only one will be described in detail. Drive unit 34 comprises an aluminium (i.e. non-ferromagnetic material) wheel 42 of cylindrical shape having a blind bore 44 and a rim 46 of 10 mm thickness. The wheel 42 is of 50 mm radius and 60 mm width. The blind end of the wheel 42 comprises a series of openings 48 through which air may pass.

One end of the chassis 32 is positioned over the open end of the blind bore 44 and mounts a DC motor gearbox combination 48; the gearbox is of the planetary type. An output shaft 50 of the DC motor 48 is mounted to the wheel 42. The DC motor 48 is manufactured by Motonnen Servo Supplies and is presently available under order code 1308-12-200. The DC motor has the following properties: length 69 mm, gear ratio 200:1, nominal voltage 12 V DC, rated torque 80 Ncm, rated speed 10 rpm, and mass about 190 g. In use, the series of openings 48 permit air flow through the interior of the drive unit 34, helping to cool the DC motor 48.

Referring to Fig. 5 a series of fourteen permanent magnets 52 is mounted centrally around the circumference of the wheel 42 and are fixed relative to the rim 46. The series of magnets 52 provides a substantially continuous track' of magnets around the circumference of the wheel 42. The corresponding series of magnets on the second drive unit 36 are in rotational alignment with the magnets 52 of the first drive unit 32, as will be explained in greater detail below.

Each one of the series of fourteen permanent magnets 52 comprises a 4 mm threaded male stud 54 and a housing 56 of 20 mm diameter; the overall weight of each permanent magnet is 15 g. The particular magnets used are available from FR Magnetics ( ww.frmagneticscorn) under part number U-C2OB1. A NdFeB, Grade N3 8 pcrmanent magnet 58 with nickel coating is of 14 mm diameter and is friction fitted within the housing 56 with a annular nylon sleeve 60 of 1.5 mm thickness. The permanent magnet 58 has one of its external faces (which is substantially flat) exposed that has a central north pole surrounded by a south pole (see Fig. 6). It has a Brmax of 12,600 Gauss equating to a pull force of 13.05 kg. The permanent magnets 52 are relatively inexpensive. -9-

The housing 56 of each permanent magnet 58 is in abutment with each adjacent housing around the outer surface of the drive unit 34.

Referring to Figs. 3 and 5, the outer surface of the wheel 42 comprises two rings 62 and 64 for engagement with a ferromagnetic surface. Each ring comprises facets 66, each of which is in alignment with the exposed flat face of its respective permanent magnet.

Referring to Figs. 3 and 7 the control unit 38 comprises a waterproof plastic housing 70 having dimensions of 150 mm by 100 mm by 60 mm (L x W x D).

Mounted within the housing is a rechargeable lithium polymer battery 72; the particular battery in this embodiment is a KONG POWER 2200 mAh 14.8 V DC 30C weighing 0.235 kg. A voltage regulator 74 converts the battery voltage to 5 V DC to supply a control microprocessor 76 and a wireless transceiver 78. In this embodiment the control microprocessor 76 is a NCAXE-18X which is has low cost, small dimensions and light weight, and the wireless transceiver 78 is an XBee PICAXE BLUETOOTH (RTM) module. The control microprocessor 76 is programmed to control the wireless transceiver 78, the two DC motors 48, and servo motors 80 that control movement of the articulated arm.

The articulated arm (not shown) is mounted to the housing 70 and comprises a plurality of links (in this embodiment two links, although one is possible) controlled by the servo motors 80. An effector, such as a camera or sensor mount, is located at a distal end of the articulated arm, and permits alternative cameras or sensors to be mounted on the apparatus 30. The effector is also movable by the servo motors 80 to provide a tilt/pan function. In other embodiments, the articulated arm is provided with a non-removable camera or sensor. In this embodiment the overall length of the articulated arm is 400 mm, although other lengths are possible. The articulated arm enables the mount to be positioned so that almost any orientation of the camera or sensor is permitted. If the apparatus is used on a lamp post for example, the articulated arm permits a camera to have an almost unobstructed 360° field of view around the lamp post.

A hand-held ground control unit (not shown) comprises a housing in which is mounted a battery, and a wireless transceiver for operation with the wireless -10-transceiver 78. There is also mounted a PICAXE-18X microprocessor for controlling the wireless transceiver and other components including a joystick. The ground control unit has three user-selectable modes for controlling movement of the apparatus into and out of position; for controlling the articulated arm; and for controlling the camera or sensor. There is also provided a colour LCD screen for receiving a wireless input from a miniature remote camera situated at the distal end of the articulated arm.

In use, the apparatus 30 may be carried easily by hand, for example by a police officer, scene of crime officer, military personnel, etc. When needed, the apparatus may be deployed on any ferromagnetic surface. Typically the apparatus 30 will be used on street furniture and more particularly on lamp posts and the like.

However, the use of the apparatus is not limited to these applications and may be used on any structure which comprises a ferromagnetic surface such as bridges, buildings, pipelines, masts, ships, etc. Taking the example of use on a lamp post, the apparatus 30 is firstly switched on. The ground control unit is also switched on at this time. The apparatus 30 is positioned by hand at or near the bottom of the lamp post and preferably just above the flanged base (if present). Those permanent magnets of each drive unit 34, 36 that are closest to the surface of the lamp post provide a permanent weight-bearing function and hold the apparatus 30 in position thereon; typicaly just one per drive unit is in contact and holds the weight of the apparatus. The ground control unit is then used to direct the DC motors to drive the apparatus up the lamp post.

The arrangement of the permanent magnets around each wheel serves to maintain the weight-bearing functionality during climbing. Tn particular, there is a design balance between the force required to hold the apparatus to the lamp post and the torque required from the DC motors to break away each magnet from the surface of the lamp post. In other words, the attractive force between each magnet and the surface is not so strong that very high torque (and thereby battery power) is required to break away each magnet, but the attractive force is sufficient to hold the weight of the apparatus and to prevent it sliding down the lamp post. We believe that this is because in turning the wheel, the DC motor of each wheel breaks away each permanent magnet gradually from the lamp post surface, as opposed to pulling it -11 -away perpendicularly (the latter force being much greater).

As the apparatus is driven up or down the lamp post surface, each permanent magnet 58 is driven through a position in which the exposed external face is either parallel with (on a flat lamp post surface) or tangential to (on a curved lamp post surface) the surface of the lamp post. In that position the gripping force of the permanent magnet is a maximum. When stationary, the permanent magnets tend to rotate the wheels to this equilibrium position and thereby hold the apparatus to the lamp post with maximum grip. This self-aligning property is permitted by the use of a planetary gearbox in each DC motor.

When climbing or descending a flat or nearly flat surface, the faceted shape of the rings 62, 64 help to ensure that as each permanent magnet is able to move as close as possible to the ferromagnetic surface, to increase magnetic attraction and to hold the apparatus to the lamp post or other object.

Traction between the wheels may be improved by addition of a high coefficient of friction coating or surface, for example a thin film coating of rubber or silicone on the rings 62, 64.

Once in position near the top of the lamp post, the articulated arm may be extended and controlled by the ground control unit to move a camera or sensor to almost any view desired by the operator.

Tn some embodiments, the wheels of the apparatus may be steerable. Tn certain aspects each wheel may be rotatable through range of up to and including 90 degrees from the position shown in the Figures. This would enable the apparatus to move around the circumference of a lamp post for example, and perform other more complicated manoeuvres on other surfaces. -12-

Claims

CLAIMS1. An apparatus for moving across a ferromagnetic surface and for holding a payload on or near said surface, which apparatus comprises a chassis on which is mounted a drive unit, a control unit and a mount for a payload, said drive unit comprising an outer surface for engagement with said ferromagnetic surface and on which is mounted a plurality of permanent magnets.
2. An apparatus as claimed in claim 1, wherein said plurality of permanent magnets is arranged around said rim such that each permanent magnet has an outwardly oriented face and that, in use, each permanent magnet is driven through a position in which said outwardly oriented face is either parallel with or tangential to said ferromagnetic surface.
3. An apparatus as claimed in claim 2, wherein in use, rotation of said drive unit causes said outwardly oriented face to rotate relative to said ferromagnetic surface, so that each permanent magnet is brought gradually into maximum attraction in said position with said ferromagnetic surface and gradually out of said maximum attraction.
4. An apparatus as claimed in claim 1, 2 or 3, wherein said permanent magnet comprises a north and a south pole that is presented to said ferromagnetic surface during use.
5. An apparatus as claimed in any preceding claim, wherein each permanent magnet is mounted in a housing, which housing is mounted on said outer surface.
6. An apparatus as claimed in any preceding claim, wherein said plurality of magncts is arranged in a substantially continuous track around said outer surface.
7. An apparatus as claimed in claim 6, wherein the centre of gravity of said apparatus acts through or near a centre line defined by said substantially continuous track.

-13 -
8. An apparatus as claimed in any preceding claim, wherein said drive unit comprises a faceted ring, each facet being substantially flush with a respective permanent magnet.
9. An apparatus as claimed in any preceding claim, further comprising a high coefficient of friction material on said outer surface for facilitating traction between said drive unit and said ferromagnetic surface.
10. An apparatus as claimed in any preceding claim, wherein said mount comprises an arm having a proximal end mounted on said apparatus and a distal end having an effector to which a camera, sensor or other device may be mounted.
11. An apparatus as claimed in any preceding claim, the arrangement being such that, in use, the apparatus is emplaceable on and removable from said ferromagnetic surface by hand.
12. An apparatus as claimed in any preceding claim, wherein said control unit comprises a wireless transceiver for receiving commands from a user-operable remote control unit.
13. An apparatus as claimed in any preceding claim, wherein said drive unit comprises a wheel having a rim around which said plurality of permanent magnets is mounted.
14. A kit comprising an apparatus as claimed in any preceding claim and a remote control unit for controlling said apparatus.
15. An apparatus as herein before described with reference to and as shown in the accompanying drawings.
16. A method of moving an apparatus across a ferromagnetic surface, which method comprises the steps of: (a) emplacing an apparatus as claimed in any of claims 1 to 13 on said surface; and (b) moving said apparatus across said surface by driving said drive unit.