A MECHANICAL JOINT STRUCTURE

Fifrld of the Invention

The present invention relates to a mechanical j oint to allow relative movement between two elements . The invention has been developed especially, but not exc lusively, to a mechanical j oint structure ' for use in a manipulator. In a further aspect , the invention relates to a manipulator element , or module , incorporating the mec hanical j oint and to a manipulator that incorporates a plurality of elements interconnected by the joint .

Background of the Invention

Joints are commonly employed to connect elements in a mechanical device together and to allow those elements to be moved relative to one another. The range of movement permitted may be defined by means of the degrees of freedom of the joint. For example, a joint may have one degree of freedom {e.g. a hinge on a door) that allows movement solely about one axis, or two or more degrees of freedom (e.g. a universal joint in a vehicle drive train has ¹ , two degrees of freedom) that allows movement about multiple axes.

Powered mechanical devices that provide articulation of individual elements are generally bulky and cumbersome. Furthermore, devices that permit movement of elements through multiple degrees of- freedom often use multiple joints (each allowing a single degree of freedom of movement) that are spaced apart (e.g. the universal joint in a vehicle drive train) . These arrangements are preferred over the use of a single joint that can provide

multiple degrees of freedom (such as a ball and socket tyP ^{e "} joint) as such joints are difficult to control precisely without the use of elaborate control mechanisms.

Sunmary of the Invention

In a first aspect, the invention provides a joint comprising at least two members attached in a manner to allow the joint structure to rotate through two rotational decfrees of freedom around a common point. •

In one form, the joint permits relative movement of the members along first and second arcuate paths to permit rotational movement about first and second axes that intersect one another. In this way the members are used to rotate relative to one another through the two ^• rotational degrees of freedom. . .

In a second aspect, the present invention provides a jo:..nt arranged to interconnect two elements to allow relative movement of those elements, the joint comprising a :!:irst member operative to be connected to one of the elements and a second member operative to be connected to the; other element, the second member being coupled to the first member so as to be movable relative to the first meiiber about a first axis, wherein the second member includes first and- second parts that are movable relative to each other about a second axis that intersects the first axis so as to allow the joint to rotate through two rotational degrees of freedom around a common point .

In one form, the first and second axes are orthogonal .

In one form, each of the first and second members includes attachment means enabling the joint to be connected to the elements. In another form, at least one

of the members is integrally formed with the element to wh.:.ch it is connected, thereby obviating the need for the attachment means.

In one form, the first and second members are movable along an arcuate path that constrains the relative movement of the first and second members to movement about thfi first axis.

In one form, the first and second parts of the second meπber are also movable along an arcuate path that constrains the relative movement of the first and second parts of the second member to movement about the second ax::,s .

In one form, the amount of rotation of the joint about at least one of the respective axes is restricted. In one form, the rotation about one of the axes is less than 180°.

In one form, the first member includes a mounting portion that has an inner surface that defines an aperture in which at ^' least a part of the second member is located. In one form, the arcuate bearing surfaces are formed by portions of the inner surface of the mounting portion and thf: outer surface of the second member.

In one form, the first part of the second member connects to the other element so that the second part is movable relative to the other element (about the second axis) and is movable relative to the one element (about tho first axis) .

In one form, the first part of the second member is potfitioned at the centre of rotation of the joint. In one form, the' mounting portion of the first member, and the second member, ^' are generally planar structures. In a particular form, the first part of the second member is positioned at the centre of rotation of

the. joint, with the second part being displaced radially outwardly from the first part in a first plane. The mounting portion of the first member, which is also displaced outwardly from the first part of the second meriber, lies in a second plane that is orthogonal to the first plane.

In one form, a first actuator is connected to the first member, to provide relative movement of the first and second members about the first axis. In one form, the second part. of the second member is connected to a second actuator that is operative to provide relative movement of the first and second parts of the second member about the second axis.

In a further aspect, the invention relates to a manipulator that incorporates first and second elements thcit are interconnected by a joint, the joint permitting relative movement of the elements along first and second arcuate paths to permit rotational movement about first and second axes which intersect one another to allow the elements to rotate through two rotational degrees of freedom around a common point .

In one form, the joint is in accordance with the second aspect described above, with the first member connected to one of the elements, and .the second member connected to the other element.

It is to be appreciated that the connection between . either or both of the joint members and the manipulator elements may be such that those parts are integrally formed together, or the parts may be formed separately and be subsequently interconnected.

In yet a further aspect, the invention relates to a manipulator module comprising a body having spaced apart first and second ends, a joint connected to the body at or

ad jacent the first end and incorporating attachment means al-owing connection of the module with the second end of another said module, wherein when so connected, the joint all.ows the connected modules to rotate relative to one another through two rotational degrees of- freedom.

In one form, the joint is in accordance with any form described above. in a particular embodiment, the second metiber of the joint is connected to the module body, and tin2 first member incorporates the attachment means that allows for connection of the module with another said module.

In one form, the attachment means is in the form of a plate that is spaced from the first end of the module body. In one form, the module includes an actuation system that is disposed within the module body and is operative to move the module relative to another module to which it is connected through the joint through the two degrees of freedom. In one form, the actuation system comprises first and second actuators operative to move the joint through respective ones of the first and second degrees of freedom.

In one form, the actuators are cable drives and the actuation system further comprises at least one drive mounted within the body and operative to impart translation to the cables to induce relative movement in the j oint .

Detailed Description of the Drawings

Features of the present invention will be presented in a description of an embodiment thereof, by way of

example, with reference to the accompanying drawings, in wh::.ch:

Figures Ia, Ib and Ic are a top view, a side view and a perspective view (respectively)* of a joint in accordance wil.h an embodiment of the present invention;

Figures 2a and 2b are _. a side view and a perspective view (respectively) of a manipulator module frame in accordance with an embodiment of the present invention;

Figures 3a and 3b are a side view and a perspective vitiw (respectively) of the joint structure of Figures Ia, Ib and Ic when located within the manipulator module frame of Figures 2a and 2b;

Figures 4a and 4b are a side view and a perspective view (respectively) of a portion of an actuation means in accordance with an embodiment of the present invention;

Figure 5 is a representative diagram depicting the interconnection between elements of the actuation means in accordance with an embodiment of the present invention;

Figures 6a, 6b and 6c are a top view, a side view and a perspective view (respectively) of a pulley which forms part of the actuation means in accordance with an embodiment of the present invention;

Figures 7a and 7b are a side view and a perspective viijw (respectively) of a manipulator module in accordance wi-::h an embodiment of the present invention; and

Figures 8a and 8b are a side view and a perspective vinw (respectively) of an assembled manipulator in accordance with an embodiment of the present invention.

Description of a Specific Embodiment

In the following description of an embodiment of the present invention, the same numeration has been utilised across all Figures, unless indicated otherwise.

Referring to Figures Ia, Ib and Ic in particular, thfsre is shown a joint structure 100 in accordance with an embodiment of the present invention. The joint structure 100 includes at least two members 102 and 104 which are arranged to permit relative movement of the members about first and second axes. This allows the two members to rotate relative to one another through two degrees of freedom. The joint structure is capable of interconnecting two elements (not shown in Figures Ia, Ib and Ic) , so that the two elements may move, relative to each other, about a common axis. The joint structure 100, and in particular members 102 and 104, to actuation means (not shown in Figures Ia, Ib and Ic) to provide controlled movement . In more detail, the joint structure 100 includes a first member 102 and a second member 104 which are coupled together so that first member 102 is moveable relative to second member 104. That is, the joint can move in the directions generally denoted by angles O ₁ and 0 ₂ - The axes of first member 102 and second member 104 intersect so that they provide a joint structure which has two degrees of freedom about a common point . As can be seen in Figures Ia, Ib and Ic, in a particular embodiment, the axtis are orthogonal . The first member 102 and the second member 104 are connected through a bearing 106, such that each member may move independently of the other.

The first member.102 includes attachment first part 1Of , being a substantially planar structure in the form of a plate. The first part 108 allows the joint to interconnect to a first element (not shown) , An attachment second part 110 is also provided to connect the second member 104 to a second element (not shown) . This alliows the joint to move the first element relative to the second element. The attachment second part 110 may also be substantially planar. It will be understood that the attachment parts may be integrally moulded with the element .

As may be seen from Figures Ia, Ib and Ic ₇ the first and second members 102 and 104 are each movable along an arcuate path that constrains the movement of first and second members 102 and 104 to movement about a first axis

The second member 104 includes a first part 109a and an arcuate second part 10?b which are constrained to movement in an arcuate path about a second axis 0 ₂ • In the embodiment shown, the first part 109a is located at the centre of rotation of the joint 100.

Furthermore, as is apparent from the embodiment disclosed herein, the amount of rotation of the joint about each axis is necessarily limited by interference with the elements. Generally, the. total rotation about each one of the axes will be less than 180°, and most likely around 90°.

The first member 102 includes a mounting portion 105, into which the second member 104 is located. The mounting portion has an inner surface 107 in which the bearing 106 resides. The inner surface 107 (in combination with the outer surface of the second member 104) defines the arcuate path through which the two members may.move.

A second attachment part 110 is provided on the first part 109a so that the joint 100 can be connected to the other element. This allows the second attachment part 110 to move relative to the second element about the axis θ ₂ anc. moveable to the first element about the axis θ ₂ . The second attachment part 110 is displaced radially outward frc-m the arcuate second part 109b in the direction of the ^• first axis 0χ. Conversely, the first attachment part 108 is displaced outwardly from the second attachment part 11C, and lies in a plane which is orthogonal to axis G ₁ -.

In the present embodiment, there is provided a further bearing 112 between the first part 109a and the second member 104.

Figures 2a and 2b depict a body 114 for a manipulator moc.ule. The body 114 is arranged to receive the joint structure 100 at an end 116, and is capable of interfacing with another body for a manipulator module {not shown) at another end 118.

Figures 3a and 3b depict the joint structure 100 located within the frame 114 to form a bare manipulator module 120. ^" The frame 114 is also arranged to receive the act.uation means 122, a portion of which is depicted at Figures 4a and 4b. A first actuator is connected to the first member 102, to provide relative movement of the first and second members 102 and 104 about the axis θ _t . Correspondingly, a second actuator is connected to the second member 104, to provide relative movement of the first arcuate part 109 and the attachment second part 110 about the axis θ ₂ . The actuation means 122 includes a motor 124 which dr:.ves a gear head 126. The gear head drives a belt drive or a screw drive (not shown in the Figures) which in turn dr.wes a linear actuator in the form of a ball screw 128

(shown in Figure 5) . The linear actuator 128 drives a tension drive 130, which in the present embodiment includes a cable 132. The cable 132 is connected at one end to the arc shaped portion of the joint 134, and at the other end to a pulley 136 {shown in detail in Figures 6a, 6b and 6c) , to allow for bidirectional control of the jo:.nt.

In other words, when the motor 124 is activated, the gear head 126 is driven, which in turn drives the linear actuator 128, causing the cable drive 130 to move, thereby moving the joint through an angle θ . It will be understood that a similar actuator means is utilised for both arc shaped portions, thereby providing motorised control for both degrees of freedom .of the joint structure.

An assembled manipulator module 138 is shown in Ficjures 7a and 7b.. As can be seen, the manipulator module is relatively compact in size, is completely self contained {i.e. all driving parts are contained within the manipulator module) , and the attachment plates allow the manipulator module to be easily connected to another module, as shown in Figures 8a and 8b. In another embodiment , the manipulator may be integrally formed, such that the joint is integrally formed with either one or bol'.h of the elements on each side of the joint.

The manipulator module may include communication means, which may take the form of an electronic interface (i e. an electronic bus) that interfaces the motors to a control means . The control means may use any type of conmuniσation technology, such as wireless, electrical wired or optical wired interfaces. The control means may be a control pad (such as a joystick) in the case of a manually controlled manipulator module, or it may be a

ccxπputlng means (such as a microcontroller or a computer) in the case of a programmable manipulator module. In other embodiments, the communication means and the microcontroller (or equivalent) may be wholly contained 5 within each module, such that each module may operate independently of other modules.

The control means may also be assisted by any one or more of a variety of external sensors or other input devices. The manipulator module may also incorporate

10 appropriate sensors which may be required to sense the surrounding environment, to avoid obstacles or to provide information on some external condition, such as teπperature, humidity, etc. In one particular embodiment, the sensor may be an optical encoder or a camera, which

15 may be used to measure the proximity of obstacles.

Another possible sensor could be a pressure sensor, which may be used to determine whether the manipulator module nan come into contact with an external obj ect .

' Whilst the joint structure described herein is shown ■ 20 located within a conventional manipulator module, it will be understood that the joint can find use in any suitable application where such a joint is required.

It will also be understood that whilst manipulator modules of a similar size are depicted in the Figures,

25. modules of different sizes may be coupled together, as required for particular applications. For example, a larger module may be used at the base of the manipulator, to improve stability. Such variations and modifications aro contemplated by embodiments of the present invention.