Instrument positioning device

Abstract

A device for positioning an instrument, comprising a base, a platform for supporting the instrument, and three spherical arms each connecting the platform to the base. Each spherical arm includes a first spherical link and a second spherical link. Each first spherical link is connected to the base by a primary joint, all primary joints being coaxial with each other. Each first spherical link is connected to a respective second spherical link by a first revolute joint. Each second spherical link is connected to the platform by a second revolute joint. The axes of the primary joint, the first revolute joint, and the second revolute joint intersect at a remote center of motion remote from the platform. The device further comprises a rotational input arranged on the base to receive a rotational drive for rotating each first spherical link about a respective primary joint so as to move the platform over a portion of the surface of a virtual sphere and rotate the platform about an instrument axis normal to the surface of the platform. In particular, the platform can rotate infinitely about the instrument axis in any orientation achievable.

Description

[Technical field]

[0001] The present invention relates to a device for positioning an instrument. In particular, but not exclusively, the instrument may be a surgical instrument and the device may be used to manipulate the instrument in surgery. [Background technology]

[0002] Minimally invasive surgery (MIS) typically uses long, thin surgical instruments to complete all surgical steps. MIS procedures use small incisions at the surgical site, resulting in smaller scars, less bleeding, and faster patient recovery. These advantages have made MIS a common procedure that is widely applied in many surgeries, including, but not limited to, laparoscopic surgery, cardiac surgery, endovascular surgery, cancer surgery, and eye surgery.

[0003] However, to perform manual MIS, surgeons must face problems such as limited field of view, unexpected hand tremor, existing leverage effects, lack of force feedback, limited degrees of freedom, and the risk of tearing or other damage to the surrounding skin and soft tissue. Specially designed robotic assistance can effectively improve precision, ensure safety, and avoid hand tremor, alleviating these limitations with capabilities beyond the capabilities of experienced surgeons. Motion during MIS surgery typically requires four degrees of freedom of motion, including three rotations (3R) around the incision point and one translation (1T) through the incision point. The conventional way to achieve this type of motion is to mount two additional actuators on the end effector (i.e., the platform that supports the surgical instrument) and apply a two-degree-of-freedom remote centre-of-motion (RCM) mechanism. The two-degree-of-freedom RCM mechanism allows the end effector to be oriented in two rotational degrees of freedom of motion around a fixed virtual point, the “remote centre-of-motion” (RCM) point. Two additional actuators attached to the end effector provide one translational degree of freedom and one rotational degree of freedom, i.e., rotational motion.

[0004] However, the disadvantage of such a configuration is that the total inertia of the system is large due to the presence of two actuators attached to the end effector, and the accuracy of the system is affected by the large inertia of the structure. In addition, the actuators attached to the end effector increase the bulk and complexity of the system due to additional transmission devices and cables for control and power.

[0005] An example of such a device is described in US Pat. No. 5,399,633, which describes a method and apparatus for a spherical parallel mechanism. The device has a platform and at least three kinematic chains. Each kinematic chain includes a link having one end pivotally coupled to the platform about a first axis and a second end pivotally coupled to an arm about a second axis. All of the arms of the kinematic chain share a common third axis. The first, second and third axes for all of the kinematic chains all pass through a stationary point in space. Movement of the arms to selected angular positions about the common third axis adjusts the orientation and position of the platform about the sphere about the stationary point. An instrument rotation actuator is provided on the platform to provide rotational movement of the instrument mounted on the platform. In the arrangement of the US Pat. No. 5,399,633, two degrees of freedom are provided by the instrument rotation actuator and the linear actuator mounted on the platform, and two additional degrees of freedom are provided by the kinematic chain. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2004 / 0024387

[0007] It is an object of certain embodiments of the present invention to overcome or mitigate certain disadvantages associated with the prior art. Summary of the Invention

[0008] According to one aspect of the present invention there is provided an apparatus for positioning an instrument, the apparatus comprising: A base and a platform for supporting the instrument; three spherical arms each connecting the platform to the base, each spherical arm including a first spherical link and a second spherical link; (i) each first spherical link is connected to the base by a main joint, and all the main joints are coaxial with each other; (ii) each first spherical link is connected to a respective second spherical link by a first revolute joint; (iii) each second spherical link is connected to the platform by a second revolute joint; (iv) axes of the main joint, the first revolute joint, and the second revolute joint intersect at a remote center of motion away from the platform; Three spherical arms and a rotational input arranged on the base to receive a rotational drive for rotating each first spherical link about a respective one of the primary joints so as to move the platform over a portion of a surface of a virtual sphere and rotate the platform about an instrument axis perpendicular to a surface of the platform; Equipped with.

[0009] In one embodiment, the three spherical arms may be configured such that all extreme allowable positions of the instrument axis relative to the primary joint axis are outside a conical working space that is symmetrically disposed about the primary joint axis.

[0010] For the four extreme positions 1, 2, 3, 4 of the instrument axis, the cone angle of the working space is equal to twice the smallest angle among θ1, θ2, θ3, and θ4 and is defined by the following formula:

number

[0011] The three spherical arms may be configured such that α=β=γ and θ1=θ2=θ3.

[0012] In some embodiments, the apparatus may further include an instrument supported by the platform, hi some embodiments, the instrument may be a surgical instrument.

[0013] In an embodiment, the apparatus further includes one or more cables extending from the base to the platform, the one or more cables may each be actuated to move an instrument supported on the platform to provide additional degrees of freedom for the instrument. The one or more cables may be unattached to any of the three spherical arms or may be guided by pulleys attached to one or more of the spherical arms to extend from the base to the platform.

[0014] The additional degrees of freedom of the instrument may include one or more of a translation of the instrument along the instrument axis, a gripping motion of the instrument, or a clamping motion of the instrument. In other embodiments, the additional degrees of freedom of the instrument may include other movements of the instrument.

[0015] In one embodiment, the additional degree of freedom includes translation of the instrument along the instrument axis, and the apparatus further includes a lead screw and a nut threadedly engaged with the lead screw, the nut supporting the instrument relative to the platform and may be translatable along the lead screw to move the instrument along the instrument axis in response to the lead screw being driven by one of the one or more cables.

[0016] In an embodiment, one or more of the three spherical arms may include a recess for accommodating one or more cables.

[0017] In an embodiment, one or more of the main joint, the first revolute joint and the second revolute joint may be hollow to allow passage of one or more cables.

[0018] The apparatus may include one or more auxiliary actuators disposed at the base, each configured to drive one of the one or more cables.

[0019] The apparatus may include one or more primary actuators disposed on the base, each configured to provide rotational drive to one of the rotational inputs.

[0020] In some embodiments, the platform is capable of infinite rotational movement about the instrument axis in any achievable orientation.

[0021] The apparatus may further include a plurality of bevel gears and a plurality of belts each drivingly coupled to at least one of the bevel gears, the plurality of bevel gears and the belts extending from the base to the platform, the plurality of bevel gears and the belts being drivable to move an instrument supported on the platform to provide additional degrees of freedom for the instrument. The bevel gears and the belts may be attached to none of the three spherical arms or may be attached to one or more of them.

[0022] The apparatus may further include one or more Bowden cables extending from the base to the platform, each of the one or more Bowden cables being actuatable to move an instrument supported on the platform to provide additional degrees of freedom for the instrument.

[0023] A further degree of freedom includes translation of the instrument along the instrument axis, and the apparatus further includes a nut arranged to support the instrument relative to the platform, the nut may be connected to and movable by one or more Bowden cables to move the instrument along the instrument axis.

[0024] According to another aspect of the present invention there is provided an apparatus for positioning an instrument, the apparatus comprising: A base and an articulated mount for supporting the instrument; two spherical arms each connecting the articulation mount to the base, each spherical arm including a first spherical link and a second spherical link; (i) each first spherical link is connected to a base by a main joint; (ii) each first spherical link is connected to a respective second spherical link by a first revolute joint; (iii) each second spherical link is connected to the joint mount by a second revolute joint, both second revolute joints being coaxial with each other; (iv) the axes of the main joint, the first revolute joint, and the second revolute joint intersect at a remote center of motion away from the joint mount; Two spherical arms and a rotational input disposed on the base to receive a rotational drive for rotating each first spherical link about a respective primary joint so as to move the joint mount over a portion of a surface of a virtual sphere; Includes.

[0025] The apparatus may include an instrument supported by the articulation mount. The instrument may be a surgical instrument.

[0026] The device may further include one or more cables extending from the base to the joint mount, the one or more cables being each drivable to move an instrument supported on the joint mount to provide additional degrees of freedom for the instrument.

[0027] One or more cables may extend from the base to the articulation mount over one or more pulleys attached to one or both of the two spherical arms.

[0028] The apparatus further includes a plurality of bevel gears and a plurality of belts each drivingly coupled to at least one of the bevel gears, the plurality of bevel gears and belts extending from the base to the articulation mount, the plurality of bevel gears and belts being drivable to move an instrument supported on the articulation mount to provide additional degrees of freedom for the instrument.

[0029] The multiple bevel gears and belts may be attached to none of the two spherical arms or to one or both.

[0030] The apparatus further includes one or more Bowden cables extending from the base to the articulation mount, each of the one or more Bowden cables being activatable to move an instrument supported on the platform to provide additional degrees of freedom for the instrument.

[0031] The further degree of freedom may include translation of the instrument along the instrument axis, the apparatus further including a nut arranged to support the instrument relative to the joint mount, the nut connected to and movable by one or more Bowden cables to move the instrument along the instrument axis.

[0032] Further degrees of freedom of the instrument may include one or more of translation of the instrument along the instrument axis, a grasping motion of the instrument, or a clamping motion of the instrument.

[0033] Further degrees of freedom may include translation of the instrument along the instrument axis and rotation of the instrument about the instrument axis, the apparatus further including a ball screw and spline combination supporting the instrument relative to the joint mount, the ball screw and spline combination drivable to translate the instrument along the instrument axis and rotate the instrument about the instrument axis.

[0034] In an embodiment, the ball screw and spline combination may be drivable by one or more cables.

[0035] In some embodiments, the ball screw and spline combination may be drivable by a number of bevel gears and belts.

[0036] Further degrees of freedom may include translation of the instrument along the instrument axis and rotation of the instrument about the instrument axis, and the apparatus may include a shaft for supporting the instrument, a ball spline and a sliding block fixed relative to the shaft, the ball spline drivable by one or more Bowden cables to rotate the shaft and instrument about the instrument axis, and the sliding block and shaft drivable by one or more Bowden cables to translate the instrument axially along the instrument axis.

[0037] The apparatus may include one or more auxiliary actuators disposed in the base and configured to drive the one or more cables.

[0038] The apparatus may include one or more auxiliary actuators disposed in the base and configured to drive the plurality of bevel gears and belts.

[0039] The apparatus may include one or more auxiliary actuators disposed at the base and configured to drive the one or more Bowden cables.

[0040] The apparatus may include one or more primary actuators disposed on the base, each configured to provide rotational drive to one of the rotational inputs.

[0041] According to another aspect of the invention there is provided a system including an apparatus as described above and an XYZ Cartesian stage supporting the apparatus.

[0042] According to another aspect of the invention there is provided a system including an apparatus as described above and an articulating arm supporting the apparatus.

[0043] Embodiments of the invention are further described below with reference to the accompanying drawings. [Brief description of the drawings]

[0044] [Figure 1] 1 is a perspective view of an apparatus for positioning an instrument according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a side view of the apparatus of FIG. 1, showing the workspace of the apparatus. [Diagram 3] FIG. 3 is a perspective view corresponding to FIG. 2. [Figure 4] FIG. 2 is a side view of a portion of the device of FIG. 1. [Diagram 5] 2 shows the four extreme positions of the device of FIG. 1. [Figure 6] 1 illustrates a portion of an apparatus according to an embodiment of the present invention configured to maximize workspace. [Figure 7] 1 is a perspective view of an apparatus according to an alternative embodiment of the present invention; [Figure 8] FIG. 2 is a perspective view of an apparatus according to another embodiment of the present invention. [Figure 9] FIG. 2 is a perspective view of an apparatus according to another embodiment of the present invention. [Figure 10] FIG. 2 is a perspective view of an apparatus according to another embodiment of the present invention. [Figure 11] FIG. 2 is a perspective view of an apparatus according to another embodiment of the present invention. [Figure 12] FIG. 2 is a perspective view of an apparatus according to another embodiment of the present invention. [Figure 13] FIG. 2 is a perspective view of an apparatus according to another embodiment of the present invention. [Figure 14] FIG. 2 is a front view of an apparatus according to another embodiment of the present invention. [Figure 15] FIG. 15 is a rear view of the device of FIG. 14. [Figure 16] FIG. 13 is a perspective view of an apparatus according to another embodiment of the present invention mounted on an XYZ Cartesian stage. [Figure 17] FIG. 17 is a front view of the device of FIG. 16. [Figure 18] FIG. 18 is a rear view of the device of FIGS. 16 and 17. [Figure 19] FIG. 13 is a perspective view of a device according to another embodiment of the present invention mounted on an articulating arm. [Figure 20] FIG. 20 is an alternative view of the device of FIG. 19. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] 1 illustrates an apparatus 10 according to one embodiment of the present invention. The apparatus 10 is a parallel mechanism and may be used to position an instrument 30. In some embodiments, the instrument 30 may be a surgical instrument and the apparatus 10 may be used to manipulate the instrument 30 as part of a surgical procedure. As described below, some embodiments of the present invention are particularly suited for use in minimally invasive surgical procedures. Other embodiments may be utilized in other surgical and non-surgical applications requiring instrument positioning and manipulation.

[0046] The device 10 includes a base 12, a platform 14 supporting an instrument 30, and three spherical arms 16a, 16b, 16c connecting the platform 14 to the base 12. In an embodiment, the device 10 includes exactly three spherical arms 16a, 16b, 16c. Each of the spherical arms 16a, 16b, 16c includes a first spherical link 18a, 18b, 18c and a second spherical link 20a, 20b, 20c connected to each other by a first revolute joint 24a, 24b, 24c.

[0047] Each of the first spherical links 18a, 18b, 18c is connected to the base 12 by a main joint 22a, 22b, 22c. All of the main joints 22a, 22b, 22c are coaxial with each other. The main joints 22a, 22b, 22c are also revolute joints.

[0048] Each of the second spherical links 20a, 20b, 20c is connected to the platform by a second revolute joint 26a, 26b, 26c. The primary joints 22a, 22b, 22c, the first revolute joints 24a, 24b, 24c, and the second revolute joints 26a, 26b, 26c all allow 360° relative rotation about their respective axes.

[0049] The axes (of rotation) of the primary joints 22a, 22b, 22c, the first revolute joints 24a, 24b, 24c and the second revolute joints 26a, 26b, 26c all intersect with each other at a so-called remote centre of motion 34. The remote centre of motion 34 is spaced from the platform 14 a distance away so as not to coincide with any part of the platform 14. The remote centre of motion 34 coincides with the instrument 30 being centrally supported by the platform 14 when the instrument 30 extends along an instrument axis 32 that extends perpendicularly from the surface of the platform 14.

[0050] Indeed, the term "spherical link" refers to an arm that extends between and is connected to two revolute joints, whose axes intersect at a point that is the remote center of motion 34. When two or more spherical links are connected to each other, the axes of all the revolute joints intersect at this common point, i.e., the remote center of motion 34. The form of the spherical link is not limited to any particular shape, including, but not limited to, arcuate and polygonal shapes. In certain embodiments, it is preferred that the spherical link has a form that facilitates easy manufacture and / or avoids collisions with other spherical links connected to it when moving relative to each other. In the non-limiting embodiments shown in Figures 1 to 7 and 10 to 11, each spherical link follows an arc of a virtual circle (or, in fact, a path on the surface of a virtual sphere). In some embodiments of the present invention, each of the first spherical links 18a, 18b, 18c and the second spherical links 20a, 20b, 20c may have a different radius of curvature with respect to the others for each spherical arm 16a, 16b, 16c. This can ensure that each of the first spherical links 18a, 18b, 18c and the second spherical links 20a, 20b, 20c avoids collision with the others. In some embodiments, the radii of curvature of the first spherical links 18a, 18b, 18c and the second spherical links 20a, 20b, 20c may be sorted from maximum to minimum with reference to the respective spherical links 18a, 18b, 18c, 20c, 20b, 20a.

[0051] The rotational inputs 28a, 28b, 28c are provided on the base 12 and are arranged to receive a rotational drive (e.g., from any suitable actuator) for moving the spherical arms 16a, 16b, 16c and thus the platform 14 and any instrument 30 supported thereon. In particular, the rotational input 28a may receive a rotational drive to rotate the first spherical link 18a about the axis of the primary joint 22a. Similarly, the rotational input 28b may receive a rotational drive to rotate the first spherical link 18b about the axis of the primary joint 22b, and the rotational input 28c may receive a rotational drive to rotate the first spherical link 18c about the axis of the primary joint 22c. By rotating the three first spherical links 18a, 18b, 18c about the primary joints 22a, 22b, 22c, the second spherical links 20a, 20b, 20c are moved by rotating them about the first revolute joints 24a, 24b, 24c relative to the first spherical links 18a, 18b, 18c. As a result, the platform 14 is moved, and such movement includes a tangential movement along a portion of the surface of a virtual sphere centered on the remote center of motion 34 due to the interaction of the spherical arms 16a, 16b, 16c, their fixation to both the base 12 and the platform 14, the presence and orientation of the first revolute joints 24a, 24b, 24c, and the presence and orientation of the second revolute joints 26a, 26b, 26c. The portion of the virtual sphere along whose surface the platform 14 moves is called the workspace of the device 10. As shown in the side view of Fig. 2, the workspace has a cone angle centered on the axes of the primary joints 22a, 22b, 22c, so that the workspace is conical and symmetrical about such axes (which are coaxial with each other). A plane 36 is defined perpendicular to the axes of the primary joints 22a, 22b, 22c, such plane 36 containing the remote center of motion 34. Fig. 3 shows a perspective view of the device 10 in the configuration of Fig. 2.

[0052] The axes of rotation of the main joints 22a, 22b, 22c are coaxial with each other and aligned with the radius of the imaginary circle through which the first spherical links 18a, 18b, 18c extend. Similarly, the axes of rotation of the first revolute joints 24a, 24b, 24c are aligned with the (different) radii of the imaginary circle through which the first spherical links 18a, 18b, 18c extend and with the radii of the imaginary circle through which the second spherical links 20a, 20b, 20c extend. The axes of rotation of the second revolute joints 26a, 26b, 26c are aligned with the (different) radii of the imaginary circle through which the second spherical links 20a, 20b, 20c extend.

[0053] As shown in Figure 4, for spherical arm 16a, the length and radius of curvature of the first spherical link 18a define a first angle α between the axis of the primary joint 22a and the axis of the first revolute joint 24a. The length and radius of curvature of the second spherical link 20a define a second angle β between the axis of the first revolute joint 24a and the axis of the second revolute joint 26a. A third angle γ is defined between the axis of the second revolute joint 26a and the instrument axis 32. Equivalent angles are defined for spherical arms 16b and 16c.

[0054] A fourth angle θ may be defined between the axis of the primary joint 22a and the instrument axis 32. Given that the first spherical link 18a, the second spherical link 20a and the platform 14 (and thus the instrument axis 32) are movable relative to one another by the primary joint 22a, the first revolute joint 24a and the second revolute joint 26a, respectively, four extreme positions 1, 2, 3, 4 of the instrument 30 and the instrument axis 32 relative to the axis of the primary joint 22a are defined by the relative placement of the first angle α, the second angle β and the third angle γ. These four extreme positions 1, 2, 3, 4 are shown superimposed on one another in FIG. 5 and are defined with reference to the fourth angle θ below.

[0055]

number

[0056] A "singularity" exists when any two of the first spherical links 18a, 18b, 18c and the corresponding second spherical links 20a, 20b, 20c are coplanar with each other. Singularities are desirable to avoid because in singular configurations one or more degrees of freedom are gained or lost such that motion cannot be precisely controlled. To ensure that the workspace is singularity-free, the four extreme positions 1, 2, 3, 4 of the instrument 30 should be outside the workspace.

[0057] In addition to allowing the platform 14 (and thus the instrument 30) to move with two degrees of freedom about the surface of the workspace, the above-described apparatus 10 allows the platform 14 (and thus the instrument 30) to rotate about the instrument axis 32, thus providing three degrees of freedom. In particular, by aligning the central axis of the workspace with the axes of the primary joints 22a, 22b, 22c and the coaxial rotational inputs 28a, 28b, 28c, infinite rolling is possible in either direction (i.e., both clockwise and counterclockwise) about the instrument axis 32 at any position within the workspace. That is, the instrument 30 may be rotated infinitely in either direction by the apparatus 10 when within the workspace.

[0058] It should be noted that the three degrees of freedom are provided without the need for any actuators on the platform 14 or instrument 30 or other parts to move relative to the base 12. In fact, as described above, any and all actuators may be provided on the base 12 to drive the rotational inputs 28a, 28b, 28c. As a result, embodiments of the present invention advantageously allow for low inertia, small footprint, high stiffness, and compact designs. By reducing the overall inertia, precision of control over the manipulation of the instrument 30 is improved.

[0059] The above cone angle of the workspace is defined as twice the smallest angle among θ1, θ2, θ3 and θ4. Since it is necessary that θ4 is always the largest among them, the definition of the cone angle may be reduced to: Cone angle = 2 × min(θ1, θ2, θ3)

[0060] According to one embodiment of the present invention, the largest possible workspace is obtained by configuring the dimensions and configuration of the spherical arms 16a, 16b, 16c such that α = β = γ. In such an embodiment, the following holds:

number

[0061] 6 shows an apparatus 10 according to one embodiment of the invention with maximum allowable cone angles (and therefore maximum allowable workspace) where α=β=γ and θ1=θ2=θ3. According to other embodiments of the invention, these relationships may not be so defined, resulting in non-maximum workspaces.

[0062] In some embodiments, in addition to the three degrees of freedom described above, a fourth degree of freedom may be provided that allows further manipulation of the instrument 32. In such embodiments, the fourth degree of freedom may be a translational movement of the instrument 30 along the instrument axis 32. However, the fourth degree of freedom is not so limited. For example, in other embodiments, the fourth degree of freedom may be a clamping or gripping movement of the instrument 30. In a preferred embodiment, the fourth degree of freedom is provided without the use of an actuator on the platform 14. In some embodiments, an actuator is provided on the base 12 that moves the instrument through the fourth degree of freedom, an example of which is described in more detail below. In some embodiments, additional degrees of freedom beyond the fourth degree of freedom may be provided. Such additional degrees of freedom may be provided without the use of an actuator on the platform 14, or, optionally, by the use of one or more actuators provided on the base 12. Any additional degrees of freedom beyond the three described above may include any suitable motion, including, but not limited to, translation of the instrument 30 along the instrument axis 32, clamping motion of the instrument 30, and grasping motion of the instrument 30 (the latter two motions requiring the instrument to have two or more articulatable parts that are moveable relative to one another).

[0063] By way of example, FIG. 7 shows an apparatus 10 having four degrees of freedom according to an embodiment of the present invention. The apparatus 10 is largely the same as the apparatus having three degrees of freedom described above with reference to FIGS. 1-6, with the exception that the apparatus of FIG. 7 is capable of translating the instrument 30 along the instrument axis 32 without relying on actuators on or about the platform 14. Instead, the apparatus 10 is provided with a cable 44 for moving the instrument through a fourth degree of freedom. The cable 44 extends from the base 12 to the platform 14 via a series of pulleys 46a, 46b, 46c, 46d, 46e. In particular, in the non-limiting embodiment shown in FIG. 7, the series of pulleys 46a, 46b, 46c, 46d, 46e are arranged such that the cable 44 extends from the base 12 along the first spherical link 18c and the second spherical link 20c to the platform 14. In other embodiments, the cable 44 may extend along the other first spherical link 18a, 18b and second spherical link 20a, 20b. Upon reaching (near) the platform 14, the cable 44 couples to the lead screw 48. A nut 50 that threads onto the lead screw 48 holds the instrument 30 relative to the platform 14. The cable 44 may be driven by an auxiliary actuator 42 attached to the base 12 to rotate the lead screw 48. In the non-limiting embodiment shown in FIG. 7, the cable 44 is an "open loop" cable at the point where it terminates at its end (rather than forming a continuous "closed loop"). Rotation of the lead screw 48 causes the nut 50 and the instrument 30 held by the nut 50 to translate in a direction parallel to the instrument axis 32 (the instrument 30 translates directly along the instrument axis 32), thereby providing a fourth degree of freedom. To facilitate the passage of the cables 44 from the base 12 to the platform 14, any one or more of the main joints 22a, 22b, 22c, the first rotary joints 24a, 24b, 24c, and the second rotary joints 26a, 26b, 26c may be hollow joints and / or any one or more of the first spherical links 18a, 18b, 18c and the second spherical links 20a, 20b, 20c may have recesses, slots, or other formations to accommodate the presence or passage of the cables 44.Alternatively, the cable 44 may extend from the base 12 to the platform 14 directly by one or more pulleys, rather than passing along the first spherical links 18a, 18b, 18c and the second spherical links 20a, 20b, 20c.

[0064] As mentioned above, in other embodiments, the fourth degree of freedom may correspond to a movement or action of the instrument 30 other than translation along the instrument axis 32. Such embodiments may still rely on a cable being driven across a series of pulleys, where the cable is driven by an actuator attached to the base 12. The platform 14 may include other components that translate the movement of the cable into a particular instrument 30 motion.

[0065] In some embodiments, multiple pulleys may be provided to transfer drive from actuators mounted on the base 12 to the instrument 30. In such embodiments, the three degrees of movement described above are still provided to allow movement of the instrument 30 to various positions within the workspace and rotation of the instrument 30 about the instrument axis 32. In the non-limiting embodiment shown in FIG. 7, three main actuators 40a, 40b, 40c are provided on the base 12 to drive the rotational inputs 28a, 28b, 28c via belts to provide the three degrees of freedom. In alternative embodiments, other actuators may be provided to provide drive to the rotational inputs 28a, 28b, 28c.

[0066] A further alternative embodiment of the present invention is shown in Figure 8. The embodiment of Figure 8 is similar to the embodiment of Figure 7, but instead of the open loop cable 44 of Figure 7, the embodiment of Figure 8 has a closed loop cable 144 driven by the auxiliary actuator 42. The open loop cable 144 is routed from the base 12 along a series of pulleys 146a, 146b, 146c, 146d, 146e, 146f, 146g to (or near) the instrument 30. In the non-limiting embodiment shown in Figure 8, each of the series of pulleys 146a, 146b, 146c, 146d, 146e, 146f, 146g is effectively a double pulley in that it allows movement of both portions of the closed loop cable 144 in opposite directions. In contrast to the embodiment of FIG. 7, the series of pulleys 146a, 146b, 146c, 146d, 146e, 146f, 146g in the embodiment of FIG. 8 does not require any recesses, slots, or other formations to accommodate the presence or passage of the cable 144 by directing the cable 144 along the upper surface of the spherical arms 16a, 16b, 16c. Likewise, a hollow revolute joint may not be required. The cable 144 may also be directed along the upper surface of one of the spherical arms 16a. The driven cable 144 rotates the lead screw 48, which translates the nut 50 and the instrument 30 held by the nut 50 in a direction parallel to the instrument axis 32 (the instrument 30 translates directly along the instrument axis 32), thereby providing a fourth degree of freedom.

[0067] A further alternative embodiment of the invention is shown in Figure 9. The embodiment of Figure 9 is identical to that of Figure 8, but the closed loop cable 144 is replaced by an open loop cable 44 (as described above with reference to Figure 7) and the lead screw is replaced by an arrangement in which the cable 44 is connected directly to the nut 50 and a biasing means in the form of a tension spring 148 is provided (other biasing means may be provided in other embodiments). The driven cable 44 may retract the nut 50 and the instrument 30 connected thereto from a first position to a second position along the instrument axis 32. In doing so, the tension spring 148 may be compressed and act to return the nut 50 and the instrument 30 to the first position (by acting between the nut 50 and another reaction surface). As a result, the instrument 30 may be moved back and forth (between a first position and a second position) along the instrument axis 32 by the cable 44, thereby providing a fourth degree of freedom.

[0068] A further alternative embodiment of the present invention is shown in Fig. 10. The embodiment of Fig. 10 is identical to the embodiment of Fig. 9, except that the cable 44 is routed directly from the base 12 to the nut 50 without passing over a series of pulleys on any of the spherical arms 16a, 16b, 16c. Instead, the cable 44 passes directly from the base 12 to the nut 50. A pair of cable guides 246a, 246b are provided. In particular, a first cable guide 246a is proximate the base 12 and a second cable guide 246b is proximate the nut 50 to guide the cable 44. The cable 44 is actuated as in the embodiment of Fig. 9 to translate the instrument 30 along the instrument axis 32, thereby providing a fourth degree of freedom.

[0069] A further alternative embodiment of the invention is shown in Fig. 11. The embodiment of Fig. 11 is identical to the embodiment of Fig. 10, but the second cable 246b is replaced by a scissor mechanism 248 that may extend relative to a frame 348 on the platform 14 by retracting the cable 44 from the first position to the second position. A tension spring 148 is provided and arranged to extend as the scissor mechanism 248 moves from the first position to the second position. Upon extension, the tension spring 148 acts to bias the scissor mechanism back to the first position. A nut 50 is attached to the scissor mechanism 248 and the instrument 30 is attached to the nut 50 such that movement of the scissor mechanism 248 moves the instrument 30 along the instrument axis 32, thereby providing a fourth degree of freedom. In the alternative embodiment, a second cable guide may additionally be provided. In some embodiments, other extension means may be provided in place of the scissor mechanism and / or other biasing means may be provided in place of the tension spring 148 .

[0070] An alternative device 10 according to an embodiment of the present invention is shown in FIG. 12. The device 10 of FIG. 12 is identical to the device of FIG. 9, but the cable 44 is replaced with a Bowden cable 82 that extends from the base 12 to the nut 50. In the illustrated embodiment, the Bowden cable 82 does not pass over any pulleys on the spherical arms 16a, 16b, 16c. The Bowden cable 82 includes an inner cable 82a that extends through and over an outer sleeve 82b. One end of the outer sleeve 82b is adjacent to the base 12, while the other end of the outer sleeve is adjacent to the nut 50, thereby directing the inner cable 82a from a position driven by the auxiliary actuator 42 toward the nut 50. As described above with respect to the embodiment of FIG. 9, when the inner cable 82a is driven by the auxiliary actuator 42, the nut 50 and the instrument 32 are moved such that the instrument 32 is moved along the instrument axis 132, thereby providing a fourth degree of freedom.

[0071] An alternative apparatus 10 according to one embodiment of the present invention is shown in Figure 13. The apparatus 10 of Figure 13 is identical to the apparatus of Figure 8, except that the closed loop cable 144 is replaced by a series of bevel gears 72 and belts 62, 74, 64. The bevel gears 72 and belts 62, 74, 64 deliver drive from the auxiliary actuator 42 to move the nut 50, which in turn moves the instrument 30 axially along the instrument axis 32.

[0072] An alternative apparatus 410 according to one embodiment of the present invention is shown in Figures 14 and 15. Apparatus 410 shares many similarities with the embodiment of apparatus 10 described above. As a result, features of apparatus 410 that are identical or functionally equivalent to features of apparatus 10 described above are identified by reference numerals that have been scaled to 400 relative to the reference numerals used in relation to apparatus 10.

[0073] The device 410 includes a platform or articulated mount 414 for supporting an instrument 430 and two spherical arms 416a, 416b. In the illustrated embodiment, the device 410 includes exactly two spherical arms 416a, 416b. Each of the spherical arms 416a, 416b includes a first spherical link 418a, 418b and a second spherical link 420a, 420b connected to each other by a first revolute joint 424a, 424b.

[0074] Each of the first spherical links 418a, 418b terminates at one end in a primary joint 422a, 422b, where the primary joints 422a, 422b are also revolute joints. The primary joints 422a, 422b can be attached to the base 412 either directly or indirectly such that each first spherical link 418a, 418b can rotate about its respective primary joint 422a, 422b relative to the base 412. The primary joints 422a, 422b can be attached to the base 412 such that the positions of the primary joints 422a, 422b are fixed relative to each other (but allow rotation).

[0075] Each of the second spherical links 420a, 420b is connected to the joint mount 414 by a second revolute joint 426a, 426b. The two second revolute joints 426a, 426b are coaxial with each other. The main joints 422a, 422b, the first revolute joints 424a, 424b, and the second revolute joints 426a, 426b all allow 360° relative rotation about their respective axes.

[0076] The axes (of rotation) of the primary joints 422a, 422b, the first revolute joints 424a, 424b and the second revolute joints 426a, 426b all intersect with each other at a so-called remote centre of motion 434. The remote centre of motion 434 is spaced from the joint mount 414 by a distance such that it does not coincide with any part of the joint mount 414. The remote centre of motion 434 coincides with the instrument 430 centrally supported by the joint mount 414 as the instrument 430 extends along an instrument axis 432 extending from the joint mount 414.

[0077] As discussed above with respect to the device 10, the term "spherical link" refers to an arm that extends between and is connected to two revolute joints, whose axes intersect at a point that is the remote center of motion 434. When two or more spherical links are connected to each other, the axes of all the revolute joints intersect at this common point, i.e., the remote center of motion 434. The form of the spherical link is not limited to any particular shape, including, but not limited to, arcuate and polygonal shapes. In certain embodiments, it is preferred that the spherical link has a form that facilitates easy manufacture and / or avoids collisions with other spherical links connected to it when moving relative to each other. In the non-limiting embodiment shown in Figures 14-20, each spherical link follows an arc of a virtual circle (or, in fact, a path on the surface of a virtual sphere). In certain embodiments of the present invention, each of the first spherical link 418a, 418b and the second spherical link 420a, 420b may have a different radius of curvature relative to the other for each spherical arm 416a, 416b. This can ensure that each of the first spherical link 418a, 418b and the second spherical link 420a, 420b avoids colliding with the other. In one embodiment, the radii of curvature of the first spherical link 418a, 418b and the second spherical link 420a, 420b may be sorted from maximum to minimum with reference to the respective spherical link 420a, 420b, 418a, 418b.

[0078] Rotational inputs 428a, 428b are provided and arranged to receive rotational drive (e.g., from any suitable actuator) for moving the spherical arms 416a, 416b and thus the articulation mount 414 and any instrument 430 supported thereon. In particular, the rotational input 428a may receive rotational drive from a primary actuator 440a to rotate the first spherical link 418a about the axis of the primary joint 422a. Similarly, the rotational input 428b may receive rotational drive from a primary actuator 440b to rotate the first spherical link 418b about the axis of the primary joint 422b. By rotating the two first spherical links 418a, 418b about the primary joints 422a, 422b, the second spherical links 420a, 420b are moved by rotating them about the first revolute joints 424a, 424b relative to the first spherical links 418a, 418b, which results in the joint mount 414 being moved, which includes a tangential movement along a portion of the surface of a virtual sphere centered on the remote center of motion 434, due to the interaction of the spherical arms 416a, 416b, their fixation to both the base 412 and the joint mount 414, the presence and orientation of the first revolute joints 424a, 424b, and the presence and orientation of the second revolute joints 426a, 426b.

[0079] The apparatus further includes auxiliary rotational inputs 460a, 460b on the base 412 that are arranged to receive rotational drive (e.g., from any suitable actuator) to drive the closed-loop cable 444 along a series of pulleys 446 on the two spherical arms 416a, 416b. Notably, the auxiliary rotational inputs 460a, 460b may each receive rotational drive from an auxiliary actuator 442a, 442b. In the illustrated embodiment, the rotational drive is transmitted from the auxiliary rotational inputs 460a, 460b to the closed-loop cable 444 via a first belt 462. The rotational drive is transmitted from the closed-loop cable 444 to each of the ball screw 466 and ball spline 468, where the ball screw 466 and ball spline 468 form a ball screw spline combination. In the illustrated embodiment, the rotational drive is transmitted from the closed-loop cable 444 to each of the ball screw 466 and ball spline 468 via a second belt 464. The ball screw 466 has a ball screw nut that may be driven when a rotational drive is transmitted to the ball screw 466. Similarly, the ball spline 468 has a ball spline nut that may be driven when a rotational drive is transmitted to the ball spline 468. The ball screw spline combination has a shaft 470 to which the instrument 430 is mounted (either directly or indirectly). When the ball screw nut and the ball spline nut are driven (i.e., rotated) in the same direction (and at the same speed), the shaft 470 and the instrument 430 are rotated about the instrument axis 432. When the ball screw nut is driven while the ball spline nut is stationary, the shaft 470 and the instrument 430 are moved axially along the instrument axis 432. When the ball spline nut is driven while the ball screw nut is stationary, the shaft 470 and the instrument 430 may be moved in a helical motion (i.e., rotate about the instrument axis 432 while simultaneously translating along the instrument axis 432). As a result, a ball screw spline combination may be provided to provide the instrument 430 with a third and fourth degree of freedom in addition to the two degrees of freedom provided by the two spherical arms 416a, 416b.

[0080] A further alternative apparatus 410' according to an embodiment of the invention is shown in Figures 16 to 18. Figure 16 shows a base 412 of the apparatus 410' mounted to an XYZ Cartesian stage 476 that is configured to translate the entire apparatus 410' in each of two orthogonal directions. Apparatus according to any embodiment of the invention may be mounted to such an XYZ Cartesian stage (or indeed any other automated or manual movement system) to move the entire apparatus.

[0081] The device 410' of Figures 16 to 18 is identical to the device 410 described above with reference to Figures 14 and 15, but the closed-loop cable 444 is replaced by bevel gears 472 and intermediate belts 474 to transmit the rotational drive from the auxiliary actuators 442a, 442b to the ball screw spline combination. The bevel gears 472 are arranged in pairs, with each pair of gears having its rotation axis aligned with one of the rotation axes of the main joints 422a, 422b and the first rotational joints 424a, 424b. An intermediate belt 474 is provided to transmit the rotational drive between two consecutive pairs of bevel gears 472. The first belt 462, bevel gear 472, intermediate belt 474 and second belt 464 transfer rotational drive from the auxiliary actuators 442a, 442b to the ball screw spline combination so that the third and fourth degrees of freedom are provided as described above with respect to the device 410.

[0082] A further alternative apparatus 410'' according to an embodiment of the invention is shown in Figures 19 and 20. The apparatus 410'' of Figures 19 and 20 is identical to the apparatus 410' described above with reference to Figures 14 and 15, except that the closed loop cable 444 is replaced by an open loop Bowden cable 482 and a closed loop Bowden cable 480. In a further difference, the apparatus 410'' includes a ball spline 484 but does not include a ball screw. In the illustration of Figures 19 and 20, the apparatus 410'' is attached to an articulating arm 478 for manual or automated movement of the entire apparatus 410''. In an embodiment, the articulating arm 478 may be a robotic arm. An apparatus according to any embodiment of the invention may be attached to such an articulating arm (or indeed any other automated or manual movement system) for moving the entire apparatus.

[0083] The Bowden cables 482, 480 each deliver force from an auxiliary actuator (not shown) which may be attached to a remote support (not shown). The open loop Bowden cable 482 includes a cable 482 that extends through and past a sleeve 482b. The cable 482a that extends past the sleeve 482b passes over the pulley 446 and connects to a connector 486 (e.g., a hook) attached to a sliding block 484, which is in turn attached to the shaft 470 of the ball spline 468.

[0084] Similarly, closed-loop Bowden cable 480 includes a cable 480a that passes through a sleeve 480b, with a portion of cable 480a exposed outside of sleeve 480b. The exposed portion of cable 480a passes over pulley 446 and is wound around hoist 490.

[0085] The sleeves 480b, 482b of the Bowden cables 480, 482 are advantageous in that they are able to support compressive stresses as opposed to tensile forces within the cables 480a, 482a while remaining flexible.

[0086] The open loop Bowden cable 482 may act to pull the sliding block 484 and the shaft 470. A biasing means 488 (e.g., a compression spring as shown) acts against the sliding block 484 to bias the sliding block 484 and the shaft 470, as the Bowden cable 482 must act against the biasing force of the biasing means to slide the sliding block 484 and the shaft 470. The biasing means 488 also maintains tension in the cable 482a. The instrument 430 is attached (either directly or indirectly) to the shaft 470 such that axial movement of the shaft caused by the Bowden cable 482 moves the instrument 430 axially forward along the instrument axis 432. When the force acting on the open loop Bowden cable 482 is released, the biasing means 488 acts to return the sliding block 484, the shaft 470 and the instrument 430 to their original rest positions by moving them axially rearward.

[0087] The closed-loop Bowden cable 480 may be actuated to rotate a hoist 490. The rotary hoist 490 rotatably drives a belt 464, which in turn rotatably drives a spline nut of the ball spline 468. Rotation of the spline nut rotates the shaft 470, which in turn rotates the instrument 430 about the instrument axis 432. The instrument is thus provided with two additional degrees of freedom beyond the two degrees of freedom provided by the two spherical arms 416a, 416b.

[0088] In some embodiments, the entire device 10 may itself be movable to move the instrument 30 beyond the range of movement permitted by the device 10. For example, the device 10 may be mounted on an articulating arm.

[0089] Due to the nature of the movements permitted by devices according to embodiments of the present invention, such devices may be referred to as coaxial spherical parallel mechanisms.

[0090] As mentioned above, certain embodiments of the present invention are particularly suitable for use in minimally invasive surgical procedures. In particular, embodiments of the present invention are particularly suitable for positioning and manipulating surgical instruments during surgical procedures. Examples of applicable minimally invasive surgical procedures include, but are not limited to, laparoscopic surgery, cardiac surgery, endovascular surgery, cancer surgery, and eye surgery. Use of embodiments of the present invention can overcome or reduce certain disadvantages associated with prior art surgical methods, including limited visibility of the surgical site, hand tremors, existing leverage effects, lack of force feedback, limited degrees of freedom, and risk of damage to surrounding tissue.

[0091] Throughout the description and claims of this specification, the words "comprise" and "include" and variations thereof mean "including but not limited to" and are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context dictates otherwise. In particular, when the indefinite article is used, the specification should be understood to contemplate the plural as well as the singular, unless the context dictates otherwise.

[0092] It should be understood that features, integers, properties, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are applicable to any other aspect, embodiment or example described herein, unless incompatible therewith. All of the features disclosed in this specification (including the accompanying claims, abstract and drawings), and / or all of the steps of the method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel, or any novel combination of features disclosed in this specification (including the accompanying claims, abstract and drawings), or any novel, or any novel combination of steps of any method or process so disclosed.

[0093] The reader's attention is directed to all documents related to this application that have been filed contemporaneously or prior to this specification and that are open to public inspection together with this specification, the contents of all such documents being incorporated herein by reference.

Claims

1. 1. An apparatus for positioning an instrument, comprising: A base and a platform for supporting the instrument; three spherical arms each connecting the platform to the base, each spherical arm including a first spherical link and a second spherical link; (i) each first spherical link is connected to the base by a main joint, and all the main joints are coaxial with each other; (ii) each first spherical link is connected to a respective second spherical link by a first revolute joint; (iii) each second spherical link is connected to the platform by a second revolute joint; (iv) the primary joint axis, the first revolute joint axis, and the second revolute joint axis intersect at a remote center of motion away from the platform; Three spherical arms; a rotational input arranged on the base to receive a rotational drive for rotating each first spherical link about a respective primary joint so as to move the platform over a portion of a surface of a virtual sphere and rotate the platform about an instrument axis perpendicular to a surface of the platform; An apparatus comprising:

2. 2. The apparatus of claim 1, wherein the three spherical arms are configured such that all extreme allowable positions of the instrument axis relative to the axis of the primary joint are outside a conical working space symmetrically disposed about the axis of the primary joint.

3. For the four extreme positions 1, 2, 3, 4 of the instrument axis, the cone angle of the working space is θ １ , θ ２ , θ ３ and θ ４ is equal to twice the smallest angle in [0010] 3. The apparatus of claim 2, wherein α is an angle between the primary joint and a respective first revolute joint, β is an angle between the first revolute joint and a respective second revolute joint, and γ is an angle between the second revolute joint and the instrument axis.

4. The three spherical arms are α=β=γ and θ １ = θ ２ = θ ３ The apparatus of claim 3 , configured such that

5. An apparatus according to any preceding claim, comprising an instrument supported by the platform.

6. The apparatus of claim 5 , wherein the instrument is a surgical instrument.

7. 7. The apparatus of any one of claims 1 to 6, further comprising one or more cables extending from the base to the platform, the one or more cables being each drivable to move the instrument supported on the platform to provide further degrees of freedom for the instrument.

8. 8. The apparatus of claim 7, wherein the one or more cables extend from the base to the platform over pulleys that are not attached to any of the three spherical arms or that are attached to one or more of the three spherical arms.

9. 9. Apparatus according to claim 7 or 8, wherein the further degrees of freedom of the instrument include one or more of a translation of the instrument along the instrument axis, a grasping motion of the instrument or a clamping motion of the instrument.

10. 10. The apparatus of claim 9, wherein the additional degree of freedom includes translation of the instrument along the instrument axis, the apparatus further comprising a lead screw and a nut threadedly engaged with the lead screw, the nut supporting the instrument relative to the platform and translatable along the lead screw to move the instrument along the instrument axis in response to the lead screw being driven by one of the one or more cables.

11. An apparatus according to any one of claims 7 to 10, wherein one or more of the three spherical arms include a recess for accommodating the one or more cables.

12. 12. The device according to any one of claims 7 to 11, wherein one or more of the main joint, the first revolute joint and the second revolute joint are hollow to allow passage of the one or more cables.

13. 13. The apparatus of claim 7, comprising one or more auxiliary actuators disposed in the base, each configured to drive one of the one or more cables.

14. 14. Apparatus according to any one of the preceding claims, comprising one or more primary actuators disposed on the base, each configured to provide rotational drive to one of the rotational inputs.

15. 6. The apparatus of claim 1, further comprising a plurality of bevel gears and a plurality of belts each drivingly coupled to at least one of the bevel gears, the plurality of bevel gears and the plurality of belts extending from the base to the platform and drivable to move the instrument supported on the platform to provide an additional degree of freedom for the instrument.

16. 16. The apparatus of claim 15, wherein the plurality of bevel gears and the plurality of belts are attached to none, one or more of the three spherical arms.

17. 6. The apparatus of claim 1, further comprising one or more Bowden cables extending from the base to the platform, each of the one or more Bowden cables being activatable to move the instrument supported on the platform to provide further degrees of freedom for the instrument.

18. 18. The apparatus of claim 17, wherein the additional degree of freedom includes translation of the instrument along the instrument axis, the apparatus further comprising a nut disposed to support the instrument relative to the platform, the nut connected to and movable by the one or more Bowden cables to move the instrument along the instrument axis.

19. 1. An apparatus for positioning an instrument, comprising: A base and an articulated mount for supporting the instrument; two spherical arms each connecting the articulation mount to the base, each spherical arm including a first spherical link and a second spherical link; (i) each first spherical link is connected to the base by a main joint; (ii) each first spherical link is connected to a respective second spherical link by a first revolute joint; (iii) each second spherical link is connected to the joint mount by a second revolute joint, the second revolute joints being coaxial with each other; (iv) the primary joint axis, the first revolute joint axis, and the second revolute joint axis intersect at a remote center of motion away from the joint mount; Two spherical arms; a rotational input disposed on the base to receive a rotational drive for rotating each first spherical link about a respective primary joint so as to move the joint mount over a portion of a surface of a virtual sphere; An apparatus comprising:

20. 20. The apparatus of claim 19, comprising an instrument supported by the articulation mount.

21. 21. The apparatus of claim 20, wherein the instrument is a surgical instrument.

22. 22. The apparatus of any one of claims 19 to 21, further comprising one or more cables extending from the base to the articulation mount, the one or more cables being each drivable to move the instrument supported on the articulation mount to provide further degrees of freedom for the instrument.

23. 23. The device of claim 22, wherein the one or more cables extend from the base to the articulation mount over one or more pulleys attached to one or both of the two spherical arms.

24. 22. The apparatus of any one of claims 19 to 21, further comprising a plurality of bevel gears and a plurality of belts each drivingly coupled to at least one of the bevel gears, the plurality of bevel gears and the plurality of belts extending from the base to the articulation mount and drivable to move the instrument supported on the articulation mount to provide an additional degree of freedom for the instrument.

25. 25. The apparatus of claim 24, wherein the plurality of bevel gears and the plurality of belts are attached to none, one or both of the two spherical arms.

26. 22. The apparatus of any one of claims 19 to 21, further comprising one or more Bowden cables extending from the base to the articulation mount, each of the one or more Bowden cables being actuatable to move the instrument supported on the articulation mount to provide a further degree of freedom for the instrument.

27. 27. The apparatus of claim 26, wherein the additional degree of freedom includes translation of the instrument along the instrument axis, the apparatus further comprising a nut positioned to support the instrument relative to the platform, the nut connected to and movable by the one or more Bowden cables to move the instrument along the instrument axis.

28. 27. Apparatus according to any one of claims 22 to 26, wherein the further degrees of freedom of the instrument include one or more of translation of the instrument along the instrument axis, a grasping motion of the instrument or a clamping motion of the instrument.

29. 26. The apparatus of any one of claims 22 to 25, wherein the further degrees of freedom include translation of the instrument along the instrument axis and rotation of the instrument about the instrument axis, the apparatus further comprising a ball screw and spline combination supporting the instrument relative to the joint mount, the ball screw and spline combination being drivable to translate the instrument along the instrument axis and rotate the instrument about the instrument axis.

30. 30. Apparatus according to claim 29 when dependent on claim 22 or 23, wherein the ball screw and spline combination is drivable by the one or more cables.

31. 30. Apparatus according to claim 29 when dependent on claim 24 or 25, wherein the ball screw and spline combination is drivable by the plurality of bevel gears and the plurality of belts.

32. 28. The apparatus of claim 26 or 27, wherein the further degree of freedom includes translation of the instrument along the instrument axis and rotation of the instrument about the instrument axis, the apparatus further comprising a shaft for supporting the instrument, a ball spline and a sliding block fixed relative to the shaft, the ball spline being drivable by the one or more Bowden cables to rotate the shaft and the instrument about the instrument axis, and the sliding block and the shaft being drivable by the one or more Bowden cables to translate the instrument axially along the instrument axis.

33. 24. The apparatus of claim 22 or 23, comprising one or more auxiliary actuators disposed in the base and configured to drive the one or more cables.

34. 26. The apparatus of claim 24 or 25, comprising one or more auxiliary actuators disposed on the base and configured to drive the plurality of bevel gears and the plurality of belts.

35. 28. The apparatus of claim 26 or 27, comprising one or more auxiliary actuators disposed in the base and configured to drive the one or more Bowden cables.

36. 36. Apparatus according to any one of claims 19 to 35, comprising one or more primary actuators disposed on the base, each configured to provide rotational drive to one of the rotational inputs.

37. A system comprising an apparatus according to any preceding claim and an XYZ Cartesian stage supporting said apparatus.

38. A system comprising a device according to any one of claims 1 to 37 and an articulated arm supporting said device.

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