WO2006037951A1

WO2006037951A1 - Artificial humanoid hand/arm assemblies

Info

Publication number: WO2006037951A1
Application number: PCT/GB2005/003701
Authority: WO
Inventors: Richard Martin Greenhill; Graeme Richard Walker; Matthew Paul Godden; John Hugo Elias
Original assignee: The Shadow Robot Company Limited
Priority date: 2004-10-01
Filing date: 2005-09-23
Publication date: 2006-04-13
Also published as: GB0517865D0; GB2418659B; GB0421820D0; GB2418659A

Abstract

An artificial humanoid hand/arm assembly which incorporates in the forearm a multiplicity of fluidic muscles (4), has muscle control means including a multiplicity of electrically controlled inlet and exhaust valves (8a, 8b), said means being supported with respect to the skeletal means of said forearm portion.

Description

ARTIFICIAL HUMANOID HAND/ARM ASSEMBLIES

Field of the Invention

This invention relates to artificial humanoid hand/arm assemblies to be employed in advanced industrial robots, humanoid robots, or prostheses. More particularly, the invention relates to an artificial hand/arm assembly in which a multiplicity of fluidic muscles are supported with respect to skeletal means of the arm portion of said arrangement; and an arrangement of electrically controlled inlet and exhaust valves serve to input and exhaust fluid into and from said muscles.

Background to the Invention

A robotic hand may be actuated by air muscles (also known as McKibben actuator or fluidic muscles) incorporated in a forearm portion. Air muscles are extremely light. However, for their operation, they form part of a system comprising, in addition to air muscles valves and a source of fluid under pressure, airlines and controlling electronics, also, the components associated with the air muscles serving to control the passage of air under pressure in the selective and concurrent, as required charging and deflation of muscles. A prototype hand, designed and built by the present inventors required to be connected to a large and heavy 'cat's cradle' of valves, which was located in the plinth on which the hand and the arm it was appended to, were set up. In order to obtain the many movements necessary to emulate the manipulative. ability of the human hand, a large number, forty, of air muscles were employed. In order to fill and empty the 40 air muscles, eighty on-off, or push-fit, (also known as '2/2') valves are normally required.

A large number of airlines (e.g. 40) were needed to bring the compressed air to the air muscles (which were located in the 'arm' much as a human's muscles are). These airlines added stiffness to the robot arm, the airlines were sometimes in the way in the course of actuation of the muscles, and, worst of all, a time delay was introduced by the length of the airlines. This was because it took an appreciable time for the air meted out or released by the valves to pass to and from the air muscles. Summary of the Invention

In accordance with the invention, humanoid artificial hand/arm assembly comprises: a multiplicity of pneumatic actuators; and, supported by a skeletal part of the arm portion of the hand/arm assembly, an actuator control assembly constituted of a multiplicity of electrically actuated inlet and exhaust fluid flow valves switchable each between an open and a closed state, and, between said valves and said pneumatic actuators, an interface arrangement, arranged, constructed, and adapted such as to enable fluid under pressure to pass by way of said fluid flow-line means selectively to and from the several said pneumatic actuator inlet valves as determined by the current states of the several inlet and exhaust fluid flow valves.

In the hereinafter described embodiment of the invention, the pneumatic actuators comprise air muscles.

Hand/arm assemblies, as stated in the next preceding paragraph, avoid the previously mentioned problems by locating the valves in a manifold array into which the air muscles are directly fitted. This has the advantage of eliminating completely the multiplicity of airlines which were needed to supply and vent the air muscles, thus reducing the delay in actuation, giving excellent control properties. It also enables the proximal attachment of the air muscles, this giving the added advantage of 'snap-on' or 'snap-off attachment, allowing rapid interchange of muscles. The simplification of flow-line tubing reduces the opportunity for leaks or the development of faults.

In addition, the hand/arm assemblies in accordance with the present invention incorporate may air-pressure transducers, integrated into the manifold close to the air muscles, so that delays in response are minimised. A single four-way cable connects the whole arrangement to the controlling computer, thus hugely reducing the cabling (and chance of faults). A single airline connects the whole arrangement to the compressed air (or fluid) system. In-line air filters have been introduced between the air valves and the air muscles. In the prior art, the supply of air from a compressor or other source is filtered to remove particles which might cause valves to jam (or cause some other problem). However, it has been found that, even with such filtration, valves quite often jam. So in the present invention we have introduced a separate inline air filter between every air muscle and its related valve.

It was thought that the filters may be necessary, to prevent material such as rubber dust, which may emanate from within the air muscles from reaching the valves. The whole arrangement, including the air muscles, connection of the air muscles, the manifold, pressure sensing, and electronics, all fit into the space not much greater than the arm of a well-built man. It is modular, self-contained, easier to install, easier to maintain, finer to control and comes closer to the weight and form factor of a human being.

Description of Embodiments of the Invention

With reference to the drawings :-

Fig. 1 shows a side view of a robotic arm and hand;

Fig. 2 is an exploded view of a valve-array plate

Fig. 2a is a similar view to Fig. 2 but shows, in addition, a board with pressure-sensors;

Fig. 3 shows a general view of an arrangement with structural support for a multiplicity of air muscles that are attached to it;

Fig. 4a is an exploded view of part of the valve manifold, including the channel-plate, gasket, valve-array, pressure sensor board and interface to computer;

Fig. 4b shows the holes and channels in the channel-plate;

Fig. 5 shows a similar view to Fig. 4a, but from a different viewpoint, and with three valve-array plates additionally shown;

Fig. 6 shows, diagrammatically, the arrangement of one of the valve-array plates in cross-section, and the two valves and one air muscle attached to it;

Fig. 7 shows the arrangement of Fig. 5, and its manner of connection to the air muscles;

Figs. 8a and 8b are diagrammatic representations of push-fit connectors employed in the arrangement of Fig. 7.

A robotic arm has an arm portion 1 and a hand portion 2 (Fig 1). The various moving parts (not shown) of the hand 2 are connected by means of tendons 3 to an array of air muscles 4 serving to activate the hand 1, being distributed around a longitudinally extending rigid support member, 10 analogous to the human radius bone. The assembly consists basically of three main parts, (which we shall call the muscle anchorage plate 6, the channel-plate 12 and the valve-array plates 7) which are mounted onto the longitudinally supporting structural member 10, adjacent to the elbow joint of the arm. The rrxuscle-plate 6:

This is a disc onto which the muscles 4 are attached by push-fit (also called one-touch) connectors 5. These connectors 5 are commercially available as pneumatics components. They allow airlines to be easily plugged and unplugged from a variety of pneumatic components. The push-fit connectors 5 (see Figs 8a and 8b) are screwed into the muscle anchorage plate 6. The holes for the push-fit connectors 5 are drilled at various angles from the normal to accommodate the different angles, generally in the range 0° to 20° from the normal, at which the air muscles pull. If this angle does not match the angle at which the air muscles pull, the muscles may fail sooner. Part of an air muscle 4 is indicated; the air muscle has a spigot, or nozzle 5 screwed into its end. This spigot has a neck 18 which latches into a push-fit connector 37, so that it cannot be pulled out again until a collar 18a on the push-fit connector 37 is pushed in. This last action releases the spigot 5. It should be noted that the push-fit connectors 37 cited here are, in distinction from the present usage, more usually used to connect airline tubes to a variety of pneumatic components. The channel-plate 12

This is a disc which is bolted onto the muscle anchorage plate 6 and contains channels 42 serving to route air from the valve-array outlets 13' to the muscle- inlets 41 (Fig 4b). The channels 42 which are milled into the channel-plate 12 form a network connecting the various muscles 4, which are positioned according to the requirements of their action, to the lined-up positions of the valve-array plates 7. The channel-plate 12 and the muscle anchorage plate 6 are bolted together with a gasket 32 therebetween, having a form as hereinafter described.

The valve-array plates 7 contain (in the preferred embodiment), either twenty or sixteen valves 8a and 8b. The valve-array plates 7 are drilled and milled so as to route the air from inlet valves 8a mounted on one side of the plates 7 to respective air muscles 4, then back to the respective exhaust valves 8b located on the other sides of the plates 7, as well as branching off 40 (Fig 6) to feed the air-pressure sensors 53 (Fig 2a) which are also mounted onto these plates 7.

A particular feature of the proposed design is the incorporation of air-filter elements 13 into the drilled-oiit air-routes 16. (Figs. 2 and 2a). These filter elements ensure that particles of dust or minute fragments of rubber from the inside of the air muscles cannot reach the valves. 'O' rings 34 ensure air-tightness when the valve-array plate is bolted down onto the Channel-plate 12. The channel-plate 12 and muscle anchorage plate 6 not only control air to the muscles 4, they also form an important part of the physical arrangement of the robotic hand 1 and arm 2, in that they provide the anchorage for all of the air muscles.

The air muscles 4 are each connected to muscle anchorage plate 6, by means of the 'push-fit' connectors 5. The connectors 5 are, accordingly, dual-purpose. On the one hand they connect the air muscles 4 to the muscle anchorage plate 6 pneumatically; air may be introduced under pressure to the air muscles, or exhausted from them, such that the muscles contract when compressed air is introduced into them. On the other hand they connect the air muscles 4 to the muscle anchorage plate 6 physically, that is to say, they anchor the air muscle at the proximal end to the arm 1, so that the force which an air muscle 4 generates may be transmitted to an associated tendon 3 and thereby to the various moving parts of the hand 2 and of the hand itself about the wrist. The push-fit connectors 5, 37 additionally allow the rapid removal and exchange of the muscles.

Four (in this example) valve-array plates 7 are bolted to the Channel-plate 12. The Channel- plate 12 is secuxed firmly by a number of posts 14 to a base-plate 9, and is also supported by the 'radius bone' structural member 10. Each valve-array plate 7 is shown (Fig 2) with the eight exhaust valves 8b thereof attached to the plate, and the corresponding eight air-filter elements 13 ('exploded') out of their respective passages 16 in the plate 7. A channel 11 ' extends under the exhaust valves 8b to allow air to escape when a valve operates (Fig 2). The exhaust valves 8b are in two groups, and an air inlet hole in the system is just visible between the two groups. An air inlet hole 15 is just visible between the two groups of exhaust valves; this supplies air to the system. A printed circuit board 50 on which are mounted pressure transducers 53 is fixedly attached to the valve-array plate 7 in such a way that each pressure transducer 53 is in register respectively with one of eight small holes 43 communicating with corresponding passages 16 in the valve-array plate. As previously intimated passages in the valve-array plate 7 are in register with passages 13' through the Channel-plate 12 and the latter passages communicate with corresponding passages through the Muscle-plate 6.

A Computer 31 acts by way of an interface 30 to open and close valves 8a and 8b to admit and exhaust air to the several muscles 4 by way of the passages 13' through the Channel-plate 12 and the Muscle-plate 6.

Fig 4b shows the channel-plate 12 with connecting channels 42. The channels each comprise respective ones of a circumferential distribution of blind bores 41, respective ones of four linear distributions of through-passages 13' and milled away recesses 42 extending between the blind bores 41 and the through-passages 13'.

Fig 5 shows the same detail as Fig 4a but with three further valve-array plates 7 added.

Fig 6 shows a diagrammatic representation of a cross-section taken through one of the plates 7, with an inlet ^"valve 8a and an exhaust valve 8b attached to it. A supply of pressurised air is available at 23. This comes through a channel 23 which is common to all the inlet valves 8a on the valve-array 7. The air is routed by a channel 24 to an inlet valve 8a. As long as the inlet valve in question is closed (its default state), the air is blocked at 22. When this valve is opened, air flows down through the channel 25. A tee-junction 40 allows air pressure to reach an air- pressure sensor 53 (Fig 2a), but the main flow of air is through the filter element 13, and thence (via the channel -plate 12, muscle anchorage plate 6 and push-fit connectors not shown in this figure but represented by the connecting tube 17) to an air muscle 4. Once the air muscle is sufficiently inflated, the valve mechanism 22 of inlet valve 8a is closed, blocking off the supply of air. To empty the air muscle, the exhaust valve 8b is used. The valve mechanism 21 is opened; air may now flow from the muscle, back through the air filter element 13, through and out of the exhaust valve at 11', from whence it is able to escape to atmosphere.

Fig 7 shows the same elements as Fig 5, but viewed from a different viewpoint. The connection of the air muscles 4 to the muscle anchorage plate 6 by means of push-fit connectors 5, 37 is shown. The push-fit connectors 5, 37 are screwed into holes 41 drilled and tapped into the muscle anchorage plate 6.

Claims

1. A humaαoid artificial hand/arm assembly which is characterized by: a multiplicity of pneumatic actuators (4); and, supported by a skeletal part (10) of the arm portion of the hand/arm assembly, an actuator control assembly constituted of a multiplicity of electrically actuated inlet and exhaust fluid flow valves (8a, 8b) switchable each between an open and a closed state, and, between said valves (8a, 8b ) and said pneumatic actuators (4) , an interface arrangement, arranged, constructed, and adapted such as to enable fluid under pressure, from a fluid source as aforesaid, to pass selectively to the several said pneumatic actuators and selectively from the said pneumatic actuators as determined by the prevailing switched states of the several said inlet and exhaust fluid flow valves (8a, 8b).

2. A hand/arm assembly as claimed in claim 1 in which said skeletally supported interface arrangement is characterized by: a first, or actuator anchorage, part (6) formed through with a multiplicity of passages (41) ; a corresponding multiplicity of push-fit connectors (5, 37), said connectors (5, 37) communicating, respectively, between said multiplicity of passages (41) and the several said pneumatic actuators (4), respectively; a second or channel part (12) formed through a multiplicity of passages (13') equal in number to twice the multiplicity of passages (41) through said actuator anchorage part (6) said channel part passages (13') being selectively linked, in pairs, by means of grooves (42) formed in and extending across a surface of said actuator anchorage part (6) at angles and with lengths appropriate to achieve such linkage, one of the passages of each said pair being in registration with an individual push-fit connector (5, 37); and in which: said multiplicity of electrically switchable fluid flow valves (8a, 8b), being, in number, equal to the multiplicity of passages (41) through said actuator anchorage part (6) are in register, respectively, with the other (13') of said passages through said channel part (12).

3. A hand/arm assembly as claimed in claim 2 characterized in that: said actuator and channel parts (6, 12) are each substantially of flat plate-form, and, subsets of said multiplicity of valves are respectively supported on respective ones of a multiplicity of third generally plate-form parts (7), said valve-supporting plate-form parts (7) being supported side-by-side outstanding from said channel plate-form part (12) from one of the edge surfaces of each of said valve plate-form parts (7).

4. A hand/arm assembly as claimed in claim 2 or 3, and which is characterized by: a multiplicity of pressure sensing means (53) operative to sense pressure at respective one of the several said push-fit connectors (5, 37).

5. A hand/arm assembly as claimed in claims 3 and 4 characterized in that said multiplicity of pressure sensing means are respectively located on said valve-supporting plate-form parts (7) at or adjacent to the positions of several said valves (8a, 8b).

6. A hand/arm assembly as claimed in any of claims 2 to 5, and which is characterized by : a multiplicity of filter elements ( 13) respectively incorporated in the fluid flow passages leading to and from said valves (8a, 8b).

7. A hand/arm assembly as claimed in claim 6 characterized in that said filter elements (13) are between the push-fit connectors (5, 37) and said channel part (12).

8. A hand/arm assembly as claimed in claim 7 characterized in that: said filter elements (13) are respectively contained within said passages in said valve supporting plate-form parts

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9. A hand/arm assembly as claimed in any preceding claim characterized in that said multiplicity of pneumatic actuators (4) comprise respective ones of a multiplicity of fluidic muscles.