Drive mechanisms for robot arms

Abstract

Robot arm comprising a joint mechanism for articulating one limb of the arm relative to another limb of the arm about two non-parallel axes of rotation, wherein the mechanism comprises: an intermediate support which is attached to a first of the links by a first pivot joint with a first axis of rotation and to a second of the links by a second pivot joint with a second axis of rotation; a first drive gear arranged on the first axis of rotation, wherein the first drive gear is rigidly connected to the carrier; a second drive gear arranged around the second axis of rotation, wherein the second drive gear is rigidly connected to the second of the links; a first drive shaft for driving the first drive gear to rotate about the first axis of rotation, wherein the first drive shaft extends along the first of the links and has a first shaft gear on it, wherein the first shaft gear is arranged to engage with the first drive gear; a second drive shaft for driving the second drive gear to rotate about the second axis of rotation, the second drive shaft extending along the first of the links on a first side of a plane containing the second axis of rotation, and extending through that plane to the second side of that plane; and an intermediate linkage that engages with the second drive shaft on the second side of the plane and couples the second shaft gear with the second drive gear.

Description

BACKGROUND

[0001] This invention relates to drive arrangements for robot joints, with particular relevance to robot wrists.

[0002] Robots required to manipulate objects, such as industrial or surgical robots, often have an arm consisting of rigid elements connected in series by a number of flexible joints. The joints can be of any type but are usually rotary joints or a combination of rotary and sliding joints. The arm extends from a base, the position of which can be fixed or movable, and terminates in a tool or an attachment for a tool. The tool could, for example, be a grasping, cutting, lighting, irradiation, or imaging tool. The last joint in the arm may be called a wrist. The wrist may allow movement around a single axis, or it may be a complex or compound articulation allowing rotation around multiple axes.As disclosed in our co-pending patent application PCT / GB2014 / 053523, the wrist joint may provide two roll joints whose axes are generally longitudinal to the arm and separated by two pitch / yaw joints whose axes are generally transverse to the arm.

[0003] In a surgical robot, there are several important criteria that influence the design of the distal joint(s) of the arm. 1. It is desirable for the arm, especially its distal portion where the wrist is located, to be small. This allows several such robotic arms to operate in close proximity and enables a wider range of surgical procedures that the arm can perform. 2. It is desirable that the outer profile of the distal section of the arm be circularly symmetrical along the length of the arm. This allows the distal section to rotate longitudinally without repositioning when in proximity to another robot, other equipment, or the patient. 3. It is desirable that the joints can transmit high torque so that they can carry heavier tools and deliver high acceleration to the tool tip. 4. It is desirable for the joints to be rigid, with little or no backlash or elasticity, so that the position of a tool tip is fixed once it has been positioned. A conventional approach to minimizing backlash is to designate one or more gear elements as sacrificial elements, but this requires high maintenance and can result in the release of worn gear particles into the arm. 5. It is desirable that all articulations have position and force / torque sensors so that the control mechanism can collect data from these sensors. 6. It is desirable that the distal section of the robot arm be as light as possible to reduce the force that must be applied by the more proximal joints of the robot arm. 7. A typical robot arm carries cables that supply power to its drive motors and possibly to a tool, and return signals from sensors such as position, torque, and image sensors. It is desirable for the arm to include a path for such cables running inside the arm. 8. It is desirable to have a method for cooling the motors that drive the distal joints of the robot arm and the payload or tool.

[0004] The number of important criteria makes it difficult to design an arm that optimally meets all requirements.

[0005] A particular challenge is fitting the motors and gears into the wrist of a robot arm. The assembly should be compact, yet also allow for high rigidity and torque transmission. Many existing designs compromise one of these criteria.

[0006] There is a need for an improved drive assembly for a joint of a robot arm. SUMMARY

[0007] According to the present invention, there is provided a robot arm comprising a joint mechanism for articulating one link of the arm relative to another link of the arm about two non-parallel axes of rotation, the mechanism comprising: an intermediate support attached to a first of the links by a first pivot having a first axis of rotation and to a second of the links by a second pivot having a second axis of rotation; a first drive gear arranged about the first axis of rotation, the first drive gear being fixedly connected to the support; a second drive gear arranged about the second axis of rotation, the second drive gear being fixedly connected to the second of the links;a first drive shaft for driving the first drive gear for rotation about the first axis of rotation, the first drive shaft extending along the first of the links and having a first shaft gear thereon, the first shaft gear arranged to engage the first drive gear; a second drive shaft for driving the second drive gear for rotation about the second axis of rotation, the second drive shaft extending along the first of the links and having a second shaft gear thereon; and an intermediate gear train carried by the carrier and coupling the second shaft gear to the second drive gear.

[0008] The intermediate gear transmission may include a first intermediate gear arranged about the first rotational axis, wherein the first intermediate gear is arranged for engagement with the second shaft gear. The first intermediate gear may be rotatable about the first rotational axis.

[0009] The robot arm may further comprise a control unit arranged to respond to command signals that command movement of the robot arm by driving the first and second drive shafts to rotate. The control unit may be configured such that, when the robot arm is commanded to articulate about the first axis without articulate about the second axis, the first shaft is driven to rotate to effect articulate about the first axis and the second shaft is also driven to rotate to prevent parasitic articulate about the second axis. The control unit may be configured to perform this action automatically.

[0010] The intermediate gear transmission may comprise a plurality of interconnected gears arranged to rotate about axes parallel to the first axis of rotation.

[0011] The intermediate gear transmission may include an intermediate shaft arranged for rotation about an axis parallel to the first axis of rotation. The intermediate shaft may have a third shaft gear thereon, wherein the third shaft gear is arranged for engagement with the second drive gear.

[0012] The interconnected gears lie on one side of a plane perpendicular to the first axis and include the teeth of the first drive gear, and at least a portion of the third shaft gear lies on the other side of that plane.

[0013] The third shaft gear may be a worm gear: that is, a gear whose tooth(s) follow a spiral path. One or both of the first and second shaft gears may be worm gears.

[0014] One or both of the first drive gears may be bevel gears: that is, gears whose rolling surface is a straight or curved cone and / or whose teeth are arranged on such a cone. The tooth lines may be straight or curved. One or both of the first drive gears may be bent-axis gears.

[0015] The first drive gear may be a partially circular gear. At least a portion of the second drive gear may intersect a circle around the first axis that is congruent with the radially outermost portion of the first drive gear. At least a portion of the intermediate shaft may intersect a circle around the first axis that is congruent with the radially outermost portion of the first drive gear.

[0016] According to a second aspect of the present invention, there is provided a robot arm comprising a joint mechanism for articulating one link of the arm relative to another link of the arm about two non-parallel axes of rotation, the mechanism comprising: an intermediate support attached to a first of the links by a first pivot having a first axis of rotation and to a second of the links by a second pivot having a second axis of rotation; a first drive gear arranged about the first axis of rotation, the first drive gear being fixedly connected to the support; a second drive gear arranged about the second axis of rotation, the second drive gear being fixedly connected to the second of the links;a first drive shaft for driving the first drive gear for rotation about the first axis of rotation, the first drive shaft extending along the first of the links and having a first shaft gear thereon, the first shaft gear arranged to engage the first drive gear; a second drive shaft for driving the second drive gear for rotation about the second axis of rotation, the second drive shaft extending along the first of the links on a first side of a plane containing the second axis of rotation and extending through that plane to the second side of that plane; and an intermediate linkage meshing with the second drive shaft on the second side of the plane and coupling the second shaft gear to the second drive gear.

[0017] The second shaft may comprise a flexible element. The flexible element is arranged on the first axis of rotation. The flexible element may be a universal joint.

[0018] The second shaft is coupled to the carrier by a pivot joint on the second side of this plane.

[0019] The second drive shaft may have a second shaft gear on the second side of this plane. The intermediate linkage may comprise an intermediate shaft with a first intermediate gear meshing with the second shaft gear and a second intermediate gear meshing with the second drive gear.

[0020] The second drive shaft may be arranged to rotate about an axis perpendicular to the second axis of rotation.

[0021] The second intermediate gear may be a worm gear. The first shaft gear may be a worm gear.

[0022] One or both of the first drive gears may be bevel gears. One or both of the first drive gears may be bent-axis gears.

[0023] The first drive gear may be a partially circular gear. At least a portion of the second drive gear may intersect a circle around the first axis that is congruent with the radially outermost portion of the first drive gear.

[0024] According to a third aspect of the present invention, there is provided a robot arm comprising a joint mechanism for articulating one link of the arm relative to another link of the arm about two non-parallel axes of rotation, the mechanism comprising: an intermediate support attached to a first of the links by a first pivot having a first axis of rotation and to a second of the links by a second pivot having a second axis of rotation; a first drive gear arranged about the first axis of rotation, the first drive gear being fixedly connected to the support; a second drive gear arranged about the second axis of rotation, the second drive gear being fixedly connected to the second of the links;a first drive shaft for driving the first drive gear for rotation about the first axis of rotation, the first drive shaft extending along the first of the links and having a first shaft gear thereon, the first shaft gear arranged for engagement with the first drive gear; a second drive shaft for driving the second drive gear for rotation about the second axis of rotation, the second drive shaft extending along the first of the links and having a second shaft gear thereon, the second shaft gear arranged for engagement with the second drive gear; the second drive shaft comprising a sliding joint whereby the length of the shaft can vary in response to movement of the carrier about the first axis;

[0025] The sliding joint can be a sliding gear coupling.

[0026] The second drive shaft may include a first flexible joint on one side of the sliding joint and a second flexible joint on the other side of the sliding joint.

[0027] The second drive shaft may be connected by a pivot joint to the support on the side of the second flexible joint opposite the sliding joint.

[0028] One or both of the first and second shaft gears may be worm gears.

[0029] One or both of the first drive gears may be bevel gears. One or both of the first drive gears may be bent-axis gears. The first drive gear may be a pitch-circular gear.

[0030] At least a part of the second drive gear can intersect a circle around the first axis that is congruent with the radially outermost part of the first drive gear.

[0031] The first and second axes can be orthogonal. The first and second axes can intersect each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will now be described by way of example with reference to the accompanying drawings.

[0033] In the drawings: Fig. Figure 1 is a general illustration of a surgical robotic arm. Fig. 2 represents the axes of rotation on the wrist of the arm Fig. 1 in more detail. Fig. 3 represents a part of a first wrist mechanism from distal and one side. Fig. 4 represents part of the first wrist mechanism from distal and the other side. Fig. Figure 5 shows part of a second wrist mechanism from proximal and one side. Fig. 6 represents part of the second wrist mechanism from distal and one side. Fig. 7 represents a third wrist mechanism from distal and one side. Fig. 8 represents the third wrist mechanism from distal and the other side. Fig. Figure 9 shows the third wrist mechanism in section on a longitudinal median plane viewed from one side. Fig. Figure 10 shows the third wrist mechanism in section on a longitudinal median plane viewed from the other side. Fig. 11 illustrates communication paths in a robot arm. Fig. 12 shows a connection module for a robot arm in longitudinal cross-section. DETAILED DESCRIPTION

[0034] The wrist mechanisms described below have been shown to provide compact and mechanically advantageous arrangements for at least some of the joints of a robot wrist or for other applications.

[0035] Fig. Figure 1 depicts a surgical robot with an arm 1 extending from a base 2. The arm comprises a number of rigid links 3. The links are coupled via rotary joints 4. The most proximal link 3a is coupled to the base via joint 4a. This and the other link are coupled in series by further joints 4. A wrist 5 consists of four individual rotary joints. The wrist 5 couples a link (3b) to the most distal link (3c) of the arm. The most distal link 3c carries an attachment 8 for a surgical instrument or tool 9. Each joint 4 of the arm has one or more motors 6 operable to cause a rotary movement at the respective joint, as well as one or more position and / or torque sensors 7 providing information regarding the current configuration and / or loading at that joint. For the sake of clarity, Fig. 1 only some of the motors and sensors are shown. The arm may be generally as described in our co-pending patent application PCT / GB2014 / 053523. The attachment point 8 for a tool may suitably comprise one or more of the following: (i) a formation enabling mechanical attachment of a tool to the arm, (ii) an interface for transmitting electrical and / or optical power and / or data to and / or from the tool, and (iii) a mechanical drive for driving the movement of part of a tool. In general, it is preferred that the motors be located proximal to the joints whose movement they drive to improve weight distribution. As explained below, the controls for the motors, torque sensors, and encoders are distributed with the arm. The controllers are connected to the control unit 10 via a communications bus.

[0036] The control unit 10 comprises a processor 11 and a memory 12. Non-volatilely stored in the memory 12 is software executable by the processor to control the operation of the motors 6 to effect operation of the arm 1 in the manner described herein. In particular, the software may control the processor 11 to cause the motors (e.g., via distributed controllers) to drive in response to inputs from the sensors 7 and from a surgeon command interface 13. The control unit 10 is coupled to the motors 6 to control them in accordance with the outputs generated by the execution of the software. The control unit 10 is coupled to the sensors 7 for receiving sensed inputs from the sensors and to the command interface 13 for receiving inputs therefrom.The respective couplings can, for example, each be electrical or optical cables or be provided by a wireless connection. The command interface 13 includes one or more input devices with which a user can request movement of the arm in a desired manner. The input devices can, for example, be manually operable mechanical input devices such as control handles or joysticks, or contactless input devices such as optical gesture sensors. The software stored in the memory 12 is configured to respond to these inputs and to cause corresponding movement of the joints of the arm according to a predetermined control strategy. The control strategy can include safety features that mitigate the movement of the arm in response to command inputs.In summary, a surgeon can thus control the robotic arm 1 at the command interface 13 to move it in a manner to perform a desired surgical procedure. The control unit 10 and / or the command interface 13 can be remote from the arm 1.

[0037] Fig. Figure 2 illustrates the wrist 5 of the robot in more detail. The wrist comprises four pivot joints 300, 301, 302, 303. The joints are arranged in series, with a rigid portion of the arm extending from each joint to the next. The most proximal joint 300 of the wrist connects the arm portion 4b to the arm portion 310. The joint 300 has a "roll" pivot axis 304 aligned generally along the extension of the arm limb 4b located immediately proximal to the wrist articulations. The next most distal joint 301 of the wrist connects the arm portion 310 to the arm portion 311. The joint 301 has a "pitch" pivot axis 305, which is perpendicular to the axis 304 in all configurations of the joints 300 and 301. The next most distal joint 302 of the wrist connects the arm part 310 to the arm part 311.The joint 302 has a "yaw" rotation axis 306, which runs perpendicular to the axis 305 in all embodiments of the joints 301 and 302. In some embodiments of the wrist, the axis 306 also runs perpendicular to the axis 304. The next distal-most joint of the wrist 303 connects the arm part 311 to the arm part 4c. The joint 303 has a "roll" rotation axis 307, which runs perpendicular to the axis 306 in all embodiments of the joints 302 and 303. In some embodiments of the wrist, the axis 307 is also perpendicular to the axis 305 and parallel (and preferably collinear) to the axis 304. It is preferred that the axes 305 and 306 intersect, as this results in a particularly compact design. The joints 300 and 303 may be positioned such that the axes 304 and 307 may pass through the intersection of the axes 305 and 306 in some embodiments of the wrist.

[0038] This design of the wrist has the advantage of allowing a large range of motion of a tool attached to the attachment point 8 at the distal end of the arm part 4c, but the wrist can be mounted in a relatively compact form and without singularities occurring at certain parts of the range of motion that could require excessively high movement speeds at individual joints.

[0039] The Fig. 3 and Fig. 4 represent an example of a mechanism suitable for moving a part of the wrist 5 of the arm 1 from Fig. 1. The Fig. 3 and Fig. 4 concentrate (like the Fig. 5 to 10) on the one with the Fig. 2 designated joints 301 and 302 connected mechanism.

[0040] In the area of ​​the wrist 5, the rigid arm parts 310, 311 have hollow outer shells or housings 310', 310", 311'. The shells form the largest part of the outer surface of the arm and contain a cavity that is partially or completely surrounded by the outer wall of the respective shell and in which the motors, sensors, cables, and other components of the arm can be accommodated. The shells can be made of a metal, for example an aluminum alloy or steel, or of a composite material, for example a fiber-reinforced resin composite material such as carbon fiber-reinforced resin. The shells form part of the rigid structure of the arm parts, which is attached between the respective joints. The shells can contain a structural framework, as will be described later with regard to the embodiment of the Fig. 7 shown.

[0041] In the Fig. 3 and Fig. In Figure 4, the shell of arm portion 310 is shown in two parts for clarity: 310' and 310", both drawn in outline and exploded. The shells of arm portions 4b and 4c, as well as the mechanism connected to joints 300 and 303, are omitted. The shell of arm portion 311 is partially shown, with the largest part extending from spur 311'.

[0042] The shell of the arm part 310 (consisting of the shell parts 310' and 310") and the shell of the arm part 311 (extending from the spur 311') are movable relative to each other about two axes of rotation shown at 20 and 21. These correspond to the axes 305, 306 of Fig. 2. Axes 20 and 21 are orthogonal. Axes 20 and 21 intersect. A center coupling 28 is mounted on arm portion 310 via bearings 29, 30. The coupling extends between bearings 29, 30. Bearings 29, 30 hold the coupling fixed to portion 310 of the arm, but allow relative rotation of the coupling and this arm portion about axis 20, thus defining a pivot joint that corresponds to joint 301 of the Fig. 2. Another bearing 31 fastens the distal shell connector spur 311' to the coupling 28. The bearing 31 holds the distal shell connector spur 311' with the coupling 28, but allows a relative movement of the spur and the coupling about the axis 21 and thus defines a pivot joint which corresponds to the joint 302 of the Fig. 2 corresponds.

[0043] As a result, the coupling 28 is firmly connected to the arm part 310 about the axis 21. The coupling 28 is also firmly connected to the arm part 311 about the axis 20. That is, the mechanism is arranged such that the coupling 28 and the arm part 310 cannot experience any relative rotation or movement about the axis 21; and the coupling 28 and the arm part 311 cannot experience any relative rotation or movement about the axis 20.

[0044] In the arm part 310 there are two electric motors 24, 25 (see Fig. 4). The motors drive respective drive shafts 26, 27, which extend into the center of the wrist mechanism. Shaft 26 drives rotation about axis 20. Shaft 27 drives rotation about axis 21. Drive shaft 26 terminates at its distal end in a worm gear 32. Worm gear 32 meshes with a bevel gear 33, which is fixedly connected to clutch 28. Drive shaft 27 terminates at its distal end in a worm gear 34. Worm gear 34 meshes with a gear train, generally shown at 35, which terminates in another worm gear 36. Worm pinion gear 36 meshes with a hypoid bevel gear 37, which is fixedly connected to distal shell connector 311'.

[0045] In this example, gear 33 is directly attached to clutch 28. That is, clutch 28 abuts gear 33. Gear 33 is therefore mounted on clutch 28. Distal shell connector spur 311' is also directly connected to gear 37. Thus, gear 37 can abut connector spur 311'.

[0046] Shafts 26 and 27 run parallel. They both extend along arm portion 310. In particular, shafts 26 and 27 extend in a direction substantially parallel to the longitudinal direction of arm portion 310. The shafts may run parallel to the longitudinal direction of arm portion 310, or they may be mounted at an angle to the general longitudinal direction of arm portion 310. For example, arm portion 310 may taper from the proximal end to the distal end, and shafts 26 and 27 may extend in a direction parallel to the taper angle of the arm portion.

[0047] The worm gears 32 and 34 are attached to the drive shafts 26 and 27, respectively, and can therefore be referred to as shaft gears. The rotation of gear 33 drives the rotation of the arm portion 311 relative to the arm portion 310 about the axis 20, so the gear 33 can also be referred to as a drive gear. Similarly, the rotation of gear 37 drives the rotation of the arm portion 311 relative to the arm portion 310 about the axis 21, so the gear 37 can also be referred to as a drive gear.

[0048] The gear 33 is designed as a sector gear: ie its operating arc (in the example of Fig. 3 and Fig. 4 defined by the arc of its teeth) is less than 360°.

[0049] The gear transmission 35 is supported by the clutch 28. The gear transmission has an input gear 38 that engages the worm 34. The input gear 38 is arranged with its axis of rotation relative to the clutch 28 coincident with the axis 20. This means that the input gear can continue to engage the worm 34 around the axis 20, regardless of the design of the clutch 28 relative to the arm part 310. A series of further gears, whose axes run parallel to the axis 20, transmits the drive from the input gear 38 to an output gear 39 on a shaft 40, whose axis of rotation relative to the carrier 28 runs parallel to, but offset from, the axis 20. The shaft 40 ends in the worm 36. The shaft 40 extends parallel to the axis 20. The gears of the gear transmission 35 are supported by the clutch 28 together with the shaft 40.

[0050] The operation of the wrist mechanism is described below. For movement about axis 20, motor 24 is operated to drive shaft 26 and rotate it relative to arm portion 310. This drives bevel gear 33 and thus coupling 28 and distal cup spur 311' to rotate about axis 20 relative to arm portion 310. For movement about axis 21, motor 25 is operated to drive shaft 27 and rotate it relative to arm portion 310. This drives bevel gear 37 and thus distal cup connector 311' to rotate about axis 21 relative to arm portion 310. It will be observed that upon rotation of the drive shaft 26, which drives the clutch 28 to rotate while the drive shaft 27 remains stationary, the gear 38 also rotates relative to the clutch 28, resulting in parasitic movement of the distal shell connector spur 311' about the axis 21.To prevent this, the arm control system 10 is designed such that, when necessary, a compensating movement of the drive shaft 27 occurs in conjunction with the movement of the drive shaft 26 to separate the movement about the axis 21 from the movement about the axis 20. For example, if relative movement of the shells 310, 311 only about the axis 20 is required, the motor 24 is operated to effect this movement, while the motor 25 is simultaneously operated in a manner that prevents the input gear 38 from rotating relative to the carrier 28.

[0051] Various aspects of the Fig. 3 and Fig. 4 are advantageous because they help to make the mechanism particularly compact. 1. Conveniently, the bevel gear 33 is designed to be part-circular: ie its teeth do not enclose a full circle. For example, the gear 33 may enclose an angle of less than 270°, or less than 180°, or less than 90°. This allows at least a part of the other bevel gear 37 to be arranged in such a way that it intersects a circle around the axis of the gear 33 which is congruent with the gear 33 and has the same radius as the outermost part of the gear 33. While this feature may be helpful in reducing the size of a series of compound joints, in a wrist of the type described in Fig. 2, which comprises a pair of roll joints with a pair of pitch / yaw joints therebetween, is of particular importance since, with a joint of this type, there is a certain redundancy between the pitch / yaw joints and, therefore, a wide range of positions of the distal end of the arm can be achieved, even if the movement about the axis 20 is restricted. 2. It is advantageous if the partial gear 33 serves for rotation about the axis 20, by which the carrier 28 is pivoted to the nearest proximal arm part 310, as opposed to rotation about the axis 21, since the partial gear can also be cut away to accommodate a shaft 40 that intersects this circle. This saves space, since the worm 36 can be arranged on the side of the bevel gear 33 opposite the gear train 35. In other embodiments, however, the partial gear could serve for rotation about the axis 21, so that the gear 37 could have a part-circular shape. 3. It is advantageous if the screws 32, 34 are arranged on the side of the axis 20 opposite the bevel gear 37: that is, there is a plane containing the axis 20, on one side of which the screws 32, 34 are located and on the other side of which the bevel gear 37 is located. This contributes to providing a compact packaging arrangement. Thus, both screws 32 and 34 are arranged on a single side of a plane containing the axis 20, which runs parallel to the longitudinal direction of the arm part 310. 4. It is advantageous if the worm 34 is arranged on the side of the worm 36 opposite the bevel gear 33 and / or the gear train 35 is arranged exclusively on the side of the worm 36 opposite the bevel gear 33. This also contributes to providing a compact packaging arrangement. That is, the gear train 35 (including all interconnected gears, for example, gears 38 and 39) can be arranged on one side of the gear 33. In other words, the gear train 35 (including its interconnected gears) and the gear 33 are arranged on opposite sides of a plane that runs parallel to both the axis 21 and the longitudinal direction of the arm part 310. This plane can contain the axis 21. 5. The gears 33 and / or 37 are expediently provided as bevel gears, since they can thus be driven by worms arranged within the plane of their respective outer radii. However, they could also be externally toothed gears that mesh with the worms 32, 34 on their outer surfaces, or radially toothed gears. 6. The bevel gear 33 is conveniently arranged between the worm gears 32 and 34. This supports the packaging of the motors 24, 25. 7. The bevel gears and their associated worm gears may conveniently have a hypoid or beveled axis configuration, e.g., Spiroid®. These gears allow for a relatively high torque capacity in a relatively compact form.

[0052] The Fig. 5 and Fig. 6 represent a second form of wrist mechanism suitable for connecting the joints 301, 302 in a wrist of the type shown in Fig. 2 described manner.

[0053] As in Fig. 5, the wrist comprises a pair of rigid outer shells 310', 311', which form the outer surfaces of the arm parts 310 and 311, respectively, of the Fig. 2. 310' is the more proximal of the shells. The arm parts formed from the shells 310', 311' can pivot relative to each other about the axes 62, 63, which correspond respectively to the axes 305, 306 of the Fig. 2. The axes 62, 63 are orthogonal. The axes 62, 63 intersect. The shells 310', 311' define the outside of the arm in the wrist region and are hollow to accommodate a rotating mechanism and a space for passing cables, etc., as described in more detail below. The shells can be made of a metal, such as an aluminum alloy or steel, or of a composite material, such as a fiber-reinforced resin composite such as carbon fiber. The shells form the primarily rigid structure of the arm parts, which is attached between the respective joints.

[0054] Fig. Figure 6 shows the same mechanism from distal and one side, with the shell 311' removed for better clarity.

[0055] The shell 310' is connected to the shell 311' by a cross coupling 64. The coupling has a central tube 65 defining a channel through its center that runs generally along the length of the arm. Extending from the tube are first arms 66, 67 and second arms 68, 69. Each of the shells 310', 311' is attached to the coupling 64 via a pivot: that is, in such a way that it can move relative to the coupling only by rotation about a single axis. The first arms 66, 67 are attached to the shell 310' by bearings 70, 71 that allow rotation between these first arms and the shell 310' about the axis 62. The second arms 68, 69 are attached to the shell 311' by bearings 72, 73 that allow rotation between these second arms and the shell 311' about the axis 63. A first bevel gear 74 is arranged concentrically to the first arms 66, 67.The first bevel gear is fixedly connected to the coupling 64 and freely rotatable relative to the proximal one of the two shells 310'. A second bevel gear 75 is arranged concentrically with the second arms 68, 69. The second bevel gear is fixedly connected to the distal one of the two shells 311' and freely rotatable relative to the coupling 64.

[0056] The pair of arms 66, 67 of the coupling are perpendicular to the pair of arms 68, 69. Arms 66 and 67 lie on the rotation axis 62, while arms 68 and 69 lie on the rotation axis 63. The coupling 64 is directly attached to the gear 74. The coupling 64 thus bears against the gear 74. The coupling 64 (and thus the gear 74) can rotate relative to the arm part 310 about the axis 62. However, the coupling 64 and the gear 74 are fixedly connected to the arm part 310 about the axis 63, so that no relative movement or rotation can occur between the coupling 64 and the arm part 310 about the axis 63.

[0057] The bevel gear 75 can be mounted directly on the arm part 311. The bevel gear 75 can rotate about the axis 63 relative to the clutch 64 (and thus the arm part 310). However, the gear 75 is fixedly connected to the clutch 64 about the axis 62. This means that no relative rotation or movement can occur between the clutch 64 and the gear 75 about the axis 62.

[0058] Two shafts 76, 77 drive the movement of the compound joint. The shafts extend from within the proximal one of the shells 310' into the central region of the joint. Each shaft is connected at its proximal end to the shaft of a corresponding electric motor (not shown), with the housings of the motors mounted inside the proximal shell 310'. In this way, the shafts 76, 77 can be driven by the motors to rotate relative to the proximal shell 310'.

[0059] Shaft 76 and the associated motor drive the movement about axis 62. Shaft 76 terminates at its distal end in a worm gear 78, which meshes with bevel gear 74. Rotation of shaft 76 causes rotation of bevel gear 74 relative to shell 310' about axis 62. Bevel gear 74 is fixedly connected to coupling 64, which in turn supports distal shell 311'. Thus, rotation of shaft 76 causes relative rotation of shells 310', 311' about axis 62.

[0060] Shaft 77 and the associated motor drive the movement around axis 63. To do this, it must ultimately drive bevel gear 75 via a worm gear 79 carried by coupling 64. The rotation of this worm gear can cause relative rotation of the coupling and distal shell 311'. To this end, the drive is transmitted from shaft 77 via a pair of gears 80, 81 carried by carrier 64 to a shaft carrying worm gear 79. Shaft 77 approaches carrier 64 from the proximal side. Gears 80, 81 are arranged on the distal side of the coupling. Gears 80, 81, and 79 are thus rigidly connected to coupling 64 around axes 62 and 63. Shaft 77 extends through the channel defined by tube 65 in the center of the coupling. To enable movement of the coupling 64 relative to the first shell 310', the shaft 77 has a universal joint or cardan joint 82 along its length.The universal joint 82 lies on the axis 62. Instead of a cardan joint, the shaft could have another form of flexible coupling, for example a flexible coupling (which could be integral with the shaft) or a form of constant velocity joint.

[0061] The worm 78 is attached to the drive shaft 76 and can therefore be referred to as a shaft gear. The rotation of the gear 74 drives the rotation of the arm portion 311 relative to the arm portion 310 about the axis 62, so the gear 74 can be referred to as a drive gear. Similarly, the rotation of the gear 75 drives the rotation of the arm portion 311 relative to the arm portion 310 about the axis 63, so the gear 75 can also be referred to as a drive gear.

[0062] The shaft 77 traverses a plane containing the rotation axis 63. The plane additionally contains the rotation axis 62. Thus, the shaft 77 comprises a proximal portion located proximal to this plane and a distal portion located distal to this plane. The proximal portion of the shaft 77 is connected or otherwise coupled to the motor. The distal portion of the shaft is attached to the gear 80. The gear 80 is thus arranged on the distal side of this plane. The gear 80 may also be referred to as a shaft gear. The proximal and distal portions of the shaft 77 may be separated by the universal joint 82. The universal joint allows the proximal and distal portions of the shaft 77 to rotate together, so that the rotation of the proximal portion is coupled to the distal portion.Since the distal portion of the shaft 77 is fixed to the gear 80, it follows that the gear 80 is rotationally fixed with the shaft 77.

[0063] Gear 80 meshes or intermeshes with gear 81. In this example, gears 80 and 81 are spur gears. Gears 80 and 81 have parallel but offset axes of rotation. The axis of rotation of gear 80 is collinear with the axis of rotation of the distal portion of shaft 77. Worm 79 is arranged to rotate in response to rotation of gear 81. Worm 79 may be rotationally fixed to gear 81 such that rotation of gear 81 causes a corresponding rotation of worm 79. Worm 79 may have an axis of rotation that is collinear with the axis of rotation of gear 81. Thus, gears 80 and 81 couple the rotation of shaft 77 to the rotation of gear 79 about a rotation axis parallel to the axis of rotation of the distal portion of shaft 77.

[0064] The rotational axis of worm 79 is not parallel to the rotational axis of gear 75 (axis 63) and does not intersect it. Gear 75 is therefore a bent-axis gear. Accordingly, the rotational axes of worm 78 and gear 74 are not parallel and do not intersect. Thus, gear 74 is also a bent-axis gear.

[0065] It is observed that the rotation of shaft 76, which causes the coupling 64 to rotate about axis 62, can cause the gears 80 and 81 (and thus the worm gear 79) to rotate when the shaft 77 is stationary, resulting in parasitic movement of the distal shell 311' relative to the shell 310' about the rotation axis 63. This is because the rotation of the coupling 64 about axis 62 driven by the rotation of the shaft 77 must be accommodated by the universal joint 82, and the rotation of the coupling 64 can cause parasitic rotation of the universal joint about the longitudinal axis of the shaft 77. Such parasitic rotation of the universal joint can cause a resulting rotation of the gears 80 and 81 and thus a rotation of the bevel gear 75.Such parasitic movements can occur if the hinge axes of the universal joint are not perpendicular to each other and / or if one of the hinge axes is not parallel and congruent with the rotation axis 62.

[0066] To prevent this parasitic movement, the control system 10 may be configured to drive a compensating movement of the shaft 77 in tandem with the movement of the shaft 76 to separate the movement about the axis 62 from the movement about the axis 63. Thus, the control system 10 may be arranged to drive the motor to drive the rotation of the shaft 76 to cause the arm portion 311' to rotate relative to the arm portion 310' about the axis 63 while simultaneously driving the motor to drive the shaft 77 to rotate in such a manner as to prevent parasitic rotation about the axis 63. The control system 10 may be configured to operate in this manner when the robot arm is commanded to articulate about the axis 62 without articulate about the axis 63.

[0067] The control system 10 may also be configured to drive the rotation of the shaft 76 and / or 77 in a manner that reduces irregularities in the rotation of the universal joint 82 (i.e., increases smoothness). The universal joint may exhibit irregularities in its rotation when it is off-axis, i.e., when the arm portion 311' is tilted relative to the arm portion 310' about the axis 62. Therefore, when the arm portion 311' is commanded to articulate relative to the arm portion 310' about the axis 63 when the arm portion 311' is tilted relative to the arm portion 310' about the axis 62, the control system may operate to drive the rotation of the shaft 77 in a manner that maintains a smooth or consistent rotational speed of the universal joint 82. This may help provide smooth and / or consistent rotation about the axis 63.

[0068] This mechanism has been found to provide a particularly compact, lightweight, and rigid drive arrangement for rotation about axes 62 and 63 without the mechanism components unduly restricting the movement of the shells. It allows both motors to be housed in the proximal shell, reducing distal weight.

[0069] Various aspects of the Fig. 5 and Fig. 6 are advantageous because they help to make the mechanism particularly compact. 1. Conveniently, the bevel gear 74 is of part-circular design: ie its teeth do not enclose a full circle. The gear 74 may, for example, enclose an angle of less than 270°, or less than 180°, or less than 90°. This allows at least a part of the other bevel gear 75 to be arranged in such a way that it intersects a circle around the axis of the gear 74 which is congruent with the gear 74 and has the same radius as the outermost part of the gear 74. While this feature may be helpful in reducing the size of a series of compound joints, in a wrist of the type described in Fig. 2, which comprises a pair of roll joints with a pair of pitch / yaw joints in between, is of particular importance because, with a joint of this type, there is a certain redundancy between the pitch / yaw joints and therefore a wide range of positions of the distal end of the arm can be achieved, even if the movement about the axis 62 is restricted. As in Fig. As shown in Figure 6, the bevel gear 74 has a reduced radius in the area not enclosed by its teeth. Partially circular bevel gears of the other embodiments may be shaped in the same way. 2. The gears 74 and / or 75 are expediently provided as bevel gears, since they can thus be driven by worms arranged within the plane of their respective outer radii. However, they could also be externally toothed gears that mesh with the worms 76, 79 on their outer surfaces, or radially toothed gears. 4. The bevel gears and the worm gears connected to them can advantageously have a beveled axis shape, e.g., Spiroid®. These allow for a relatively high torque capacity in a relatively compact form.

[0070] The Fig. Figures 7 to 10 illustrate another form of the wrist mechanism. In these figures, the shells of the arm parts 310, 311 are omitted, revealing the structure within the arm parts. The proximal arm part 310 has a structural framework 100, which is shown in outline in some of the figures. The distal arm part 311 has a structural framework 101. The arm parts 310 and 311 are rotatable relative to each other about axes 102, 103, which correspond to axes 305 and 306, respectively, of the Fig. 2. A support 104 couples the arm parts 310, 311 together. The support 104 is attached to the arm part 310 via bearings 105, 190. These bearings define a pivot about the axis 102 between the arm part 310 and the support 104. The support 104 is attached to the arm part 311 via a bearing 106. These bearings define a pivot about the axis 103 between the arm part 311 and the support 104. A first bevel gear 107 about axis 102 is fixedly connected to the support 104. A second bevel gear 108 about the axis 103 is fixedly connected to the arm part 311.

[0071] The carrier 104 can therefore rotate relative to the arm part 310 about the axis 102. The carrier 104 is otherwise fixedly connected to the arm part 310 and in particular fixedly connected about the axis 103. Therefore, the carrier 104 is not permitted any relative rotation with respect to the arm part 310 about the axis 103. The second bevel gear 108 can rotate relative to the carrier 104 about the axis 103. The second bevel gear 108 (and thus the arm part 311) can be fixedly connected to the carrier about the axis 102. Thus, the bevel gear 108 is permitted to experience relative rotation with respect to the carrier 104 about the axis 103, but not relative rotation with respect to the carrier about the axis 102.

[0072] Axes 102 and 103 are perpendicular to each other in this example, but are generally two non-parallel axes. They may be substantially orthogonal to each other. In at least one embodiment of joints 301 and 302, the axes extend substantially transversely to the longitudinal direction of arm portion 310. In the arrangement shown, such an embodiment is when arm portion 311 is not articulated with respect to arm portion 310. In a Cartesian coordinate system, axis 102 may be considered the "pitch" rotation axis and axis 103 the "yaw" rotation axis.

[0073] As with the other mechanisms described herein, the carrier 104 is disposed within the links 310, 311.

[0074] Two motors 109, 110 are attached to the frame 100 of the arm portion 310. The motor 109 drives a shaft 111. The shaft 111 is rigid and terminates in a worm 118 that meshes with the bevel gear 107. When the motor 109 is operated, the shaft 111 rotates relative to the proximal arm portion 310 and drives the bevel gear 107 and thus the coupling 104 and the arm portion 311 to rotate about the axis 102 relative to the arm portion 310. The motor 110 drives a shaft 112. The shaft 112 has a worm 113 near its distal end that meshes with the bevel gear 108. To accommodate the movement of the bevel gear 108 relative to the motor 110 as the coupling 104 moves about the axis 102, the shaft 112 includes a pair of universal joints 114, 115 and a splined coupling 116 that accommodates the axial extension and retraction of the shaft 112. The final portion of the shaft 112 is mounted to the coupling 104 by the bearing 117.

[0075] The wedge coupling 116 is an example of a sliding joint.

[0076] The distal part of the shaft 112, which is mounted on the carrier 104 by the bearing 117, is fixedly connected to the worm 113 (most clearly in Fig. 10). The bearing 117 defines a pivot joint located on the opposite side of the universal joint 115 from the coupling 116. This pivot joint allows the distal portion of the shaft 112 to rotate relative to the carrier 104. The distal portion of the shaft 112 extends in a direction perpendicular to the axis 102 in all rotational positions of the carrier and is rotatable with respect to the carrier 104 about an axis perpendicular to the axis 102. With reference to Fig. 7, it can be seen that the shaft 112 passes through a plane containing the axis 102, which is transverse to the longitudinal direction of the arm portion 310. In this example, the distal portion of the shaft 112 is directly attached to the worm 113 and thus extends between the worm and the carrier 104. The distal portion of the shaft 112 is mounted on the carrier 104 such that the worm 113 securely engages the bevel gear 108 when the carrier 104 is articulated about the axis 102.

[0077] The universal joints 114 and 115 of the shaft 112 are arranged on opposite sides of the coupling 116. Both universal joints are arranged proximal to the rotation axes 102 and 103. The universal joints 114, 115 and the coupling 116 are arranged to allow the support 104 to rotate relative to the arm portion 310 about the axis 102.

[0078] The bevel gear 107 is arranged around the axis 102. This means that the gear 107 has the axis 102 as its axis of rotation. The rotation of the gear 107 around the axis 102 drives the rotation of the arm part 311 relative to the arm part 310. The gear 107 can therefore be referred to as a drive gear.

[0079] The bevel gear 108 is arranged around the axis 103. Thus, the bevel gear 108 has the axis 103 as its axis of rotation. The rotation of the gear 108 around the axis 103 drives the rotation of the arm part 311 relative to the arm part 310 around the axis 310. The gear 108 can therefore also be referred to as a drive gear.

[0080] The shaft 111 extends along the longitudinal direction of the arm part 310. The longitudinal axis of the shaft 111 can be perpendicular to the axis 102 in all rotational positions of the carrier 104 about the axes 102 and 103. The shaft 111 (and the worm 118 attached to it) rotate about the longitudinal axis of the shaft 111. This axis of rotation is not parallel to the axis of rotation 102 of the gear 107 and does not intersect it. The gear 107 is therefore a bent-axis gear.

[0081] Both screws 113 and 118 can be arranged on a single side of a plane containing the axis 103, which runs transversely to the longitudinal direction of the arm part 311 when this arm part is aligned with the arm part 310 about the axis 103, in other words, when the arm part 311 is not yawing relative to the arm part 310. In particular, both screws can be arranged on the proximal side of this plane. However, the screws 113 and 118 can be arranged on opposite sides of a plane containing the axis 102, which runs parallel to the longitudinal direction of the arm part 311.

[0082] Through the operation of the universal joints 114 and 115 and the coupling 116, the worm gears 113 and 118 rotate relative to each other about the axis 102 when the carrier 104 is articulated about the axis 102. When the arm portion 310 is aligned with the arm portion 311 about the axis 102 (i.e., when the arm portion 311 is not tilted relative to the arm portion 310), the worm gear 113 and the distal portion of the shaft 112 are parallel to the shaft gear 118 and to the shaft 111. In all other configurations of the arm portions about the axis 102, the worm gear 113 and the distal portion of the shaft 112 are not parallel to the shaft gear 118 and to the shaft 111.

[0083] The worms 113 and 118 are attached to the respective drive shafts 112 and 111 and can therefore also be referred to as shaft gears.

[0084] The following describes how the joint mechanism works.

[0085] To drive the articulations about axis 102, motor 109 is operated to rotate drive shaft 111 about its longitudinal axis. Since shaft gear 118 is attached to shaft 111, rotation of shaft 111 also causes gear 118 to rotate about the longitudinal axis of shaft 111. Shaft gear 118 meshes with drive gear 107 and causes it to rotate about axis 102 relative to arm portion 310. Carrier 104 is fixedly connected to drive gear 107, and thus rotation of drive gear 107 causes carrier 104 to rotate about axis 102 relative to arm portion 310. Rotation of the support 104 about the axis 102 causes the arm portion 311 to articulate relative to the arm portion 310 about the axis 102. Rotation of the support 104 about the axis 102 causes the universal joints 114 and 115 and the sliding joint 116 to articulate to accommodate the rotation of the shaft gear 113 relative to the shaft gear 118 about the axis 102.

[0086] To drive articulations about axis 103, motor 110 is driven to rotate drive shaft 112. The rotation of the proximal end of drive shaft 112 is coupled to the rotation of shaft gear 113 via universal joints 114 and 115 (and coupling 116). Shaft gear 113 meshes with bevel gear 108. Thus, the rotation of shaft gear 113 drives the rotation of gear 108 about axis 103 relative to support 104. Bevel gear 108 is fixedly connected to arm portion 311, and thus, the rotation of gear 108 causes articulation of arm portion 311 with respect to arm portion 310 about axis 103.

[0087] Rotation of the drive shaft 111 while the shaft 112 is stationary can cause parasitic movement of the arm portion 311 about the axis 103. This is because rotation of the carrier 104 about the axis 102 can cause rotation of the universal joints 114 and 115, which drives the rotation of the worm 113 and thus the cone 108. To prevent this parasitic movement, the control system 10 can be arranged to drive the motor 109 to drive the rotation of the shaft 111 to cause the rotation of the arm portion 311 relative to the arm portion 310 about the axis 102 while simultaneously driving the motor 110 to drive the rotation of the shaft 112 in a manner that prevents parasitic rotation about the axis 103. The control system 10 may be designed to operate in this manner when the robot arm is commanded to articulate about axis 102 without articulate about axis 103.

[0088] The control system 10 may also be configured to drive the rotation of the shaft 112 in a manner to reduce irregularities in the rotation of the universal joints 114 and 115. The universal joints may experience irregular or inconsistent rotation when off-axis, that is, when the arm portion 311 is tilted relative to the arm portion 310. Therefore, if the arm portion 311 is commanded to articulate relative to the arm portion 310 about the axis 103 when the arm portion 311 is tilted relative to the arm portion 310, the control system 10 may operate to drive the rotation of the shaft 112 in a manner that maintains a smooth or constant rotational speed of the universal joints 114 and 115. This may help provide smooth and / or consistent rotation about the axis 103.

[0089] Various aspects of the Fig. The mechanism shown in Figures 7 to 10 is advantageous because it helps to make the mechanism particularly compact. For example: Conveniently, the bevel gear 107 is designed to be part-circular: ie, its teeth do not enclose a full circle. The gear 107 may, for example, enclose an angle of less than 270°, or less than 180°, or less than 90°. This allows at least a part of the other bevel gear 108 to be arranged in such a way that it intersects a circle around the axis of the gear 107 which is congruent with the gear 107 and has the same radius as the outermost part of the gear 107. While this feature may be helpful in reducing the size of a series of compound joints, in a wrist of the type described in Fig. 2, which comprises a pair of roll joints with a pair of pitch / yaw joints therebetween, is of particular importance since, with a joint of this type, there is a certain redundancy between the pitch / yaw joints and, therefore, a wide range of positions of the distal end of the arm can be achieved even if the movement about the axis 102 is restricted.

[0090] Conveniently, the worms 118 and 113 are arranged on opposite sides of the bevel gear 107. In other words, the bevel gear 107 can be inserted between the worms 113 and 118. This can help provide a compact packaging arrangement. The gears 107 and / or 108 are conveniently provided as bevel gears, as they can thus be driven by worms arranged within the plane of their respective outer radii. However, they could also be externally toothed gears that mesh on their outer surfaces with the worms attached to the shafts 111, 112, or externally toothed gears.

[0091] The bevel gears and the associated worm gears can advantageously have a beveled axis shape, e.g., Spiroid®. These allow for a relatively high torque capacity in a relatively compact form.

[0092] Various changes may be made to the mechanisms described above. For example, and without limitation: - The axes corresponding to axes 305 and 306 do not need to intersect and do not need to be orthogonal. In general, the axes corresponding to axes 305 and 306 are two non-parallel axes of rotation. They can be substantially perpendicular to each other in all configurations of joints 301 and 302. In at least one configuration of joints 301 and 302, each axis can be substantially transverse to the longitudinal direction of arm portion 310. One such configuration is when arm portion 311 is neither in pitch nor in yaw relative to arm portion 310. - The axes corresponding to axes 305 and 306 are not parallel, but need not be orthogonal to each other. Axis 305 is not parallel to axis 304, but need not be orthogonal to it. Axis 306 is not parallel to axis 307, but need not be orthogonal to it. - The axes corresponding to axes 304 and 307 need not be parallel and collinear; they could be parallel but not collinear. For example, arm portion 3b could be curved relative to arm portion 3c. - The bevel gears or their external gear equivalents don't have to be driven by worms. They could be driven by other gears. They could be driven by pinions, for example. - Thus, the drive gears can be bevel gears or other types of internal gears, such as externally toothed gears, i.e., gears with teeth extending in a radial direction. The shaft gears could be worm gears or other types of gears such as pinions, e.g., bevel gears. - One or both bevel gears could be partial gears. Generally, one or both drive gears could be partial gears. - In the above examples, the mechanisms form part of a robot arm's wrist. The mechanisms could also be used for other applications, such as other parts of robot arms, robotic tools, and non-robotic applications such as control heads for cameras.

[0093] As mentioned above with reference to Fig. As explained in Figure 1, each joint is equipped with a torque sensor that detects the torque applied around the axis of the respective joint. The data from the torque sensors is provided to the control unit 10 to control the arm operation.

[0094] The Fig. 9 and Fig. 10 illustrates one of the torque sensors and its mounting arrangement in cross-section. The torque sensor 150 measures the torque applied about the axis 103: i.e., from the carrier 104 to the distal arm frame 101. As described above, the bevel gear 108 is fixedly connected to the frame 101 and rotatable about the axis 103 with respect to the carrier 104. The bevel gear 108 includes a radially extending gear portion 151, from which its teeth 152 extend in an axial direction, and an axially extending neck 153. The neck, the radially extending gear portion, and the teeth are integrally formed. The inner and outer walls of the neck 153 have a circular-cylindrical profile. A pair of roller or ball bearing races 106, 154 fit snugly against the outside of the neck.The bearings are seated in cups in the carrier 104 and hold the neck 153 in position relative to the carrier while allowing rotation of the bevel gear 108 relative to the carrier about the axis 103.

[0095] The torque sensor 150 includes a radially extending upper flange 155, an axial torque tube 156 extending from the upper flange, and an internally threaded base 157 at the end of the torque tube opposite the flange. The upper flange 155 abuts the gear portion 151 of the bevel gear 108. The upper flange is held to the gear portion by bolts 158. The torque tube 156 extends within the neck 153 of the bevel gear 108. The outer wall of the torque tube has a circular cylindrical profile. The outer surface of the base 157 is formed with a wedge structure that positively engages a corresponding structure in the frame 101 to hold both in a fixed relationship about the axis 103. A bolt 159 extends through the frame 101 and into the base 157 to clamp them together.Thus, it is the torque sensor 150 that attaches the bevel gear 108 to the arm frame 101, and the torque applied about the axis 103 is applied via the torque sensor. The torque tube has a hollow interior and a relatively thin wall to its torque tube 150. Upon applying torque via the torque sensor, a slight torsional deformation of the torque tube occurs. The deflection of the torque tube is measured with strain gauges 160 attached to the inner wall of the torque tube. The strain gauges generate an electrical output indicative of the torsion, which provides a representation of the torque about the axis 103. The strain gauges could take another form: for example, optical interference strain gauges that provide an optical output.

[0096] To obtain the most accurate output from the torque sensor, torque transmission from the bevel gear 108 to the frame 101 bypassing the torque tube 156 should be avoided. For this reason, it is preferable to reduce friction between the neck 153 of the bevel gear 108 and the base 157 of the torque sensor. One possibility is to provide a gap between the neck of the bevel gear and the base of the torque sensor, as well as the torque tube. However, this could result in shear forces being applied to the torque tube in a direction transverse to the axis 103, which in turn would reduce the accuracy of the torque sensor by exposing the strain gauges 160 to forces other than torsional forces. Another possibility is to insert a bearing ring between the inside of the neck of the bevel gear 108 and the outside of the base 157 of the torque sensor.However, this would significantly increase the volume occupied by the mechanism. Instead, it has been shown that the volume in . Fig. 8 leads to good results. A sleeve or bushing 161 is provided around the torque tube 156 and within the neck 153 of the bevel gear 108. The sleeve is sized to make continuous contact with the inner wall of the neck 153 and with the outer wall of the torque tube 156, which also has a circular cylindrical profile. The entire inner surface of the sleeve contacts the outer surface of the torque tube 156. The entire outer surface of the sleeve contacts the inner surface of the neck 153. The sleeve is constructed to create relatively little friction between the neck and the torque tube: for example, the sleeve may be made of or coated with a low-friction or self-lubricating material. The sleeve is made of a substantially incompressible material so that it can prevent deformation of the torque sensor under shear forces transverse to the axis 103.For example, the sleeve may be made of or coated with a plastic material such as nylon, polytetrafluoroethylene (PTFE), polyethylene (PE) or acetal (e.g. Delrin®), or graphite or a lubricant-impregnated metal.

[0097] To facilitate assembly of the mechanism and to retain the sleeve 161, the inner wall of the neck 153 of the bevel gear 108 is stepped inwardly at 162 near the end remote from the radially extending portion of the gear 151. When the sleeve 161 is disposed between the neck 153 and the torque tube 156, and the torque sensor head 155 is threadedly secured to the gear portion 151, the sleeve is retained both radially (between the torque tube and the neck) and axially (between the torque sensor head 155 and the step 162 of the inner surface of the bevel gear neck 153). Preferably, the inner radius of the neck 153 in the region 163 beyond the step 162 is such that the inner surface of the neck is spaced from the torque sensor 150 in this region, thereby preventing frictional torque transfer between the two.

[0098] Similar arrangements can be made for the torque sensor about the other axis 102 of the embodiment of the Fig. 7 to 10 and for the torque sensors of the embodiments of the other figures.

[0099] Hall-effect sensors are used to detect the rotational position of the joints. Each position sensor comprises a ring of material arranged around one of the rotational axes. The ring has a series of regularly spaced, alternating magnetic north and south poles. Adjacent to the ring is a sensor chip with a sensor array comprising multiple Hall-effect devices that can detect the magnetic field and measure the position of the magnetic poles on the ring relative to the sensor array to provide a multi-bit output indicating this relative position. The rings of magnetic poles are arranged such that each position of the respective joint within a 360° range is associated with a unique set of outputs from the magnetic sensor pair. This can be achieved by providing a different number of poles on each ring, with the number of poles of the rings being coprime.Hall-effect position sensors that use this general principle are known for use in robotics and other applications.

[0100] More specifically, each joint is assigned a pair of alternately magnetized rings and corresponding sensors. Each ring is arranged concentrically around the axis of its respective joint. The rings are rigidly connected to an element on one side of the joint and the sensors to an element on the other side of the joint, so that when the robot arm rotates around the respective joint, there is a relative rotational movement of each ring and its respective sensor. Each individual sensor measures where, between a pair of poles, its corresponding ring is positioned relative to the sensor. From the output of an individual sensor, it is not possible to determine which of the pole pairs on the ring is above the sensor. Therefore, the individual sensors can only be used in a relative manner and would require calibration upon power up to determine the absolute position of the joint.However, by using a pair of rings designed such that the number of pole pairs in each ring has no common factors, it is possible to combine the inter-pole pair measurements from both sensors and determine the absolute position of the joint without calibration.

[0101] The magnetic rings and sensors are in the Fig. 7 to 10. For the joint that provides rotation about axis 102, the position is detected by means of magnetic rings 200 and 201 and sensors 202 and 203. For the joint that provides rotation about axis 103, the position is detected by means of magnetic rings 210, 211, sensor 212, and another sensor, not shown. Magnetic ring 200 is rigidly connected to carrier 104 and mounted on one side of the carrier. Magnetic ring 201 is rigidly connected to carrier 104 and mounted on the other side of the carrier to magnetic ring 200. Magnetic rings 200, 201 are planar and arranged perpendicular to and centered on axis 102. Sensors 202 and 203 are rigidly connected to frame 100 of arm portion 310. Sensor 202 is mounted adjacent to one side of ring 200. Sensor 203 is mounted adjacent to one side of ring 201. The signals from sensors 202 and 203 are transmitted via cables 204 and 205.The magnetic ring 210 is rigidly connected to the support 104 and mounted on one side of a flange 220 of the support. The magnetic ring 211 is rigidly connected to the support 104 and mounted on the other side of the flange 220 to the magnetic ring 200. The magnetic rings 210, 211 are arranged planar and perpendicular to the axis 103 and centered thereon. The sensor 212 and the other sensor for rotation about the axis 103 are rigidly connected to the frame 101 of the arm part 311. The sensor 212 is mounted adjacent to one side of the ring 210. The other sensor is mounted adjacent to one side of the ring 211.

[0102] Thus, in the arrangement of the Fig. 7 to 10, the rotation about each of the axes 102, 103 is detected by means of two multi-pole magnetic rings, each of which is assigned a sensor. Each sensor generates a multi-bit signal that represents the relative position of the nearest poles on the respective ring to the sensor. By arranging the number of poles on the two rings as mutually proportional, the outputs of the sensors in combination are indicative of the design of the joint within a 360° range. This allows the rotational position of the joint to be determined within this range. In addition, the arrangement of the Fig. 7 to 10, the two rings associated with each joint (i.e., rings 200, 201 on one side and rings 210, 211 on the other side) are arranged such that they are substantially offset from each other along the axis of the respective joint. Ring 200 is arranged near bearing 190 on one side of the body of support 104, while ring 201 is arranged near bearing 105 on the opposite side of support 104. Ring 210 is arranged on one side of flange 220, while ring 211 is arranged on the other side of flange 220. Each ring consists of a plate of material that is flat in a plane perpendicular to the axis around which the ring is arranged. The magnetic rings of each pair (i.e.,The rings (i.e., rings 200, 201 on one side and rings 210, 211 on the other side) are spaced apart from each other in the direction along their respective axes by a distance greater than 5 times, and preferably greater than 10 times or greater than 20 times, the thickness of the rings of the pair. Conveniently, the rings of a pair may be located on opposite sides of the respective joint, as with rings 200, 201. Conveniently, the support 104, to which the two rings of a pair are attached, extends radially outwardly so that it lies at a radial location which, viewed in a plane with the respective axis of rotation, is between the rings. For example, the flange 220 lies radially between the rings 210 and 211.Conveniently, the respective joint may be supported or defined by two bearings, one on each side of the joint along the respective axis and at extreme points of the joint, and the or each ring for that joint may overlap a respective one of the bearings in a plane perpendicular to the axis. Conveniently, the sensors for the rings may be mounted on an arm portion articulated by the joint. The sensors may be mounted on opposite sides of the arm portion.

[0103] By spacing the rings, the packaging of the joint and / or the arm section in which the associated sensors are mounted can be significantly improved. The spacing between the rings offers more options for placing the rings in a convenient location and allows the sensors to be spaced apart, which in turn can provide packaging advantages. Preferably, the joint is sufficiently stiff compared to the number of magnetic poles on the rings that torsion of the joint under load does not adversely affect the measurement. For example, it is preferred that the joint be sufficiently stiff so that the elements of the joint cannot twist so much under their maximum operating load that this could change the order of the magnetic transitions on the sensors, even when spaced apart. This makes it possible to detect not only the movement but also the direction for all load conditions.

[0104] The arm part 311 is distal from the arm part 310. The arm part 310 is proximal to the joint around the Fig. 7 to 10 shown axes 102 and 103. As with reference to Fig. As explained in Figure 1, the data from the torque sensors and the position sensors is returned to the control unit 10. It is desirable that this data be transmitted via wired connections running through the arm itself.

[0105] Each arm section contains a circuit board. Fig. 7 to 10 illustrate a circuit board 250 carried by an arm portion 311. Each circuit board includes a data encoder / decoder (e.g., integrated circuit 251). The encoder / decoder converts signals between the formats used locally in the respective arm portion and a format used for data transmission along the arm. For example: (a) Local to the arm portion, the position sensors may return position measurements as they are passed by the magnetic pole transitions, the torque sensor may return an analog or digital signal indicating the currently sensed torque, and the drive motors may require a pulse-width modulated drive signal; whereas (b) for data transmission along the arm, a general data transmission protocol, which may be a packet data protocol such as Ethernet, may be used.In this way, the encoders / decoders can receive data packets transmitted from the control unit 10 along the arm and interpret their data to form control signals for any local motor. They can also receive locally acquired data and convert it into a packetized form for transmission to the control unit. The circuit boards along the arm can be chained together by communication cables, so that communication occurs from a relatively distal board through the more proximal boards.

[0106] In general, it is desirable not to route data from one component of the arm to a more distal component of the arm. This would require cables to run unnecessarily distally in the arm, increasing the distally distributed weight; and because the circuit boards are daisy-chained, once data has been sent to a relatively distal board, the nearest board will process the data to forward it anyway.

[0107] The composite joint about axes 102, 103 includes rotational position sensors 202, 203 (for rotation about axis 102) and 212 (for rotation about axis 103). Sensors 202, 203 are mounted on frame 100 of arm portion 310, which is proximal to the joint whose movement is measured by the sensor. Data from position sensors 202, 203 is transmitted via cables 204, 205 that run along arm portion 310 proximal to the sensors. Sensor 202 is mounted on frame 101 of arm portion 311. Data from position sensor 202 is transmitted via a cable to circuit board 250 on the same arm portion. In any case, the data is not transmitted to a more distal element of the arm than the one at which the data was acquired.

[0108] The composite joint around axes 102, 103 has torque sensors 150 (for rotation around axis 103) and 191 (for rotation around axis 102). The data acquired by the torque sensors 150, 191 is transmitted in native form via flexible cables to the circuit board 250. On the circuit board 250, the encoder / decoder 251 encodes the acquired data, e.g., into Ethernet packets, and transmits it to the control unit 10. Therefore, the data from the torque sensors is not forwarded to the circuit board of the more proximal arm section 310 for encoding, but rather to the circuit board of the more distal arm section for encoding. From this circuit board, the data is then transmitted via cables in the distal direction along the arm.

[0109] This arrangement is in Fig. 11. The arm portion 310 includes a circuit board 195 that receives data from the position sensor 202 and provides command data to the motors 109, 110. The arm portion 311 includes a circuit board 250 that receives data from the position sensor 212 and the torque sensors 150, 191. The circuit board 250 encodes this acquired data and forwards it via a data bus 196 to the circuit board 195, which forwards it via a connection 197 to the control unit 10. The position sensor 202 is connected directly to the circuit board 195 via a cable. The position sensor 212 and the torque sensors 150, 191 are connected directly to the circuit board 195 via cables.

[0110] As in Fig. 2, the arm part 4c is supported by the arm part 311 and can be rotated relative to the arm part 4c about the axis 307. Fig. Figure 12 shows a cross-section through a module that includes the arm part 4c. The module has a base 400 and a side wall 440 that is fixedly connected to the base. The base 400 is attached to the end surface 401 of the distal end of the arm part 311. (See Fig. 7). The arm part 4c is generally designated 403. The arm part 4c is rotatable relative to the base about an axis 402, which corresponds to the axis 307 of the Fig. 2. For this purpose, the arm part 4c is mounted on the side wall 440 via bearings 430, 431, which define a pivot joint between the side wall 440 and the arm part 4c about the axis 402.

[0111] The arm portion 4c has a housing 404 in which its internal components are housed. These components include a circuit board 405 and motors 406, 407. The motors 406, 407 are rigidly connected to the housing 404 so that they cannot rotate relative thereto. The housing 404 is freely rotatable relative to the base 400 by means of bearings 430, 431. A channel 408 extends through the interior of the module to accommodate a communication cable (not shown) that runs from the circuit board 250 to the circuit board 405. The communication cable transmits signals which, when decoded by an encoder / decoder of the circuit board 405, cause the circuit board 405 to output control signals to control the operation of the motors 406, 407.

[0112] The motor 406 drives the rotation of the arm portion 4c relative to the arm portion 311. Thus, the motor 406 drives the rotation of the housing 404 relative to the base 400. The base 400 has a central projection 410. A torque sensor is attached to the projection 410, which is generally the same as that shown in the Fig. 9 and Fig. 10. The torque sensor comprises an integrated element comprising a base 411, a torque tube 412 and a radially extending head 413. The base 411 of the torque sensor is fixedly connected to the projection 410 of the base 400. As with the torque sensor of Fig. 9 and Fig. 10, a sleeve 421 extends around the torque tube of the torque sensor to protect it from shear forces and reduce friction between it and the surrounding component, i.e., the base 400.

[0113] An internally toothed gear 420 is fixedly connected to the head 413 of the torque sensor. The motor 406 drives a shaft 414 carrying a pinion gear 415. The pinion gear 415 meshes with the internal gear 420. Thus, during operation, the motor 406 drives the pinion gear 415 to rotate, causing the arm portion 4c, of which the motor 406 is a part, to rotate about the axis 402. The resulting torque about the axis 402 is transmitted through the torque sensor's torque tube 412 to the base 400, so that this torque can be measured by strain gauges attached to the torque tube.

[0114] The interface 8 for attachment to an instrument is in Fig. 12. The shaft 440 of the motor 407 is exposed at the interface to provide a drive for an instrument.

[0115] The torque data from the torque sensors 411, 412, 413 are forwarded to the circuit board 250 on the arm part 311 for coding. The rotational position of the arm part 4c can be detected by a sensor 445 carried by the arm part 4c, which detects the transitions between the magnetic poles on the rings 446, 447 mounted inside the housing 404. The data from the sensor 445 is forwarded to the circuit board 405 of the arm part 4c for coding.

[0116] The motors that drive rotation about joints 102 and 103 are mounted proximal to these joints in arm portion 310. As explained above, this improves weight distribution by avoiding shifting the weight closer to the distal end of the arm. In contrast, the motor that drives rotation of arm portion 4c is mounted in arm portion 4c and not in arm portion 311. Although this might be considered disadvantageous because it requires motor 406 to be mounted more distally, it has been found to make arm portion 311 particularly compact. Motor 406 can be packaged in arm portion 4c parallel to the motor(s) (e.g., 407) that provide drive to the instrument: i.e., such that the motors intersect in a common plane perpendicular to axis 402. This means that the installation of the motor 406 in the arm part 4c does not have to significantly lengthen the arm part 4c.

[0117] Instead of toothed gears, the joints could be driven by friction.

[0118] The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, insofar as such features or combinations can be carried out by those skilled in the art based on the present description as a whole in light of the common knowledge of those skilled in the art, regardless of whether such features or combinations of features solve the problems disclosed herein, and without limiting the scope of the claims. The applicant points out that aspects of the present invention may consist of any of these individual features or a combination of features. In view of the foregoing description, it will be obvious to one skilled in the art that various modifications can be made within the scope of the invention. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] GB 2014 / 053523 [0002, 0035]

Claims

[1] A robot arm comprising a joint mechanism for articulating one member of the arm relative to another member of the arm about two non-parallel axes of rotation, the mechanism comprising: an intermediate support attached to a first of the links by a first pivot having a first axis of rotation and to a second of the links by a second pivot having a second axis of rotation; a first drive gear arranged on the first rotation axis, the first drive gear being fixedly connected to the carrier; a second drive gear disposed about the second axis of rotation, the second drive gear being fixedly connected to the second of the links; a first drive shaft for driving the first drive gear to rotate about the first axis of rotation, the first drive shaft extending along the first of the links and having a first shaft gear thereon, the first shaft gear being arranged to engage the first drive gear; a second drive shaft for driving the second drive gear to rotate about the second axis of rotation, the second drive shaft extending along the first of the links on a first side of a plane containing the second axis of rotation and extending through that plane to the second side of that plane; and an intermediate linkage engaging the second drive shaft on the second side of the plane and coupling the second shaft gear to the second drive gear. [2] The robot arm of claim 1, wherein the second shaft comprises a flexible member. [3] Robot arm according to claim 2, wherein the flexible element is arranged on the first axis of rotation. [4] Robot arm according to claim 2 or 3, wherein the flexible element is a universal joint. [5] Robot arm according to one of the preceding claims, wherein the second shaft is coupled to the support via a pivot joint on the second side of said plane. [6] A robot arm according to any one of the preceding claims, wherein the second drive shaft has a second shaft gear on the second side of said plane and the intermediate linkage comprises an intermediate shaft having a first intermediate gear meshing with the second shaft gear and a second intermediate gear meshing with the second drive gear. [7] A robot arm comprising a joint mechanism for articulating one member of the arm relative to another member of the arm about two non-parallel axes of rotation, the mechanism comprising: an intermediate support attached to a first of the links by a first pivot having a first axis of rotation and to a second of the links by a second pivot having a second axis of rotation; a first drive gear arranged on the first rotation axis, the first drive gear being fixedly connected to the carrier; a second drive gear disposed about the second axis of rotation, the second drive gear being fixedly connected to the second of the links; a first drive shaft for driving the first drive gear to rotate about the first axis of rotation, the first drive shaft extending along the first of the links and having a first shaft gear thereon, the first shaft gear being arranged to engage the first drive gear; a second drive shaft for driving the second drive gear to rotate about the second axis of rotation, the second drive shaft extending along the first of the links and having a second shaft gear thereon, the second shaft gear arranged to engage the second drive gear; wherein the second drive shaft comprises a sliding joint whereby the length of the shaft can vary in response to movement of the carrier about the first axis. [8] Robot arm according to claim 7, wherein the sliding joint is a sliding gear coupling. [9] A robot arm according to claim 7 or claim 8, wherein the second drive shaft comprises a first flexible joint on one side of the sliding joint and a second flexible joint on the other side of the sliding joint. [10] Robot arm according to claim 9, wherein the second drive shaft is connected by a rotary joint to the support on the side of the second flexible joint opposite the sliding joint. [11] Robot arm according to one of the preceding claims, wherein one or both of the first drive gears are bevel gears. [12] A robot arm according to any one of the preceding claims, wherein one or both of the first drive gears are bent axis gears. [13] Robot arm according to one of the preceding claims, wherein the first drive gear is a part-circular gear and wherein at least a part of the second drive gear intersects a circle around the first axis which coincides with the radially outermost part of the first drive gear. [14] Robot arm according to one of the preceding claims, wherein the first and second axes are orthogonal. [15] Robot arm according to one of the preceding claims, wherein the first and second axes intersect each other.

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