BACKGROUND
It is known to use robots for assisting and performing surgery. Figures 1 and 2 show a typical
surgical robot 100 which comprises a base 101, an arm 102 and an instrument 103. The base
supports the robot, and is itself attached rigidly to, for example, the operating theatre floor,
the operating theatre ceiling or a trolley. The arm 102 extends between the base and the
10 instrument. The arm is articulated by means of multiple flexible joints 104 along its length,
which are used to position the surgical instrument 103 in a desired location relative to the
patient. The surgical instrument is attached to the distal end of the robot arm. The surgical
instrument penetrates the body of a patient at a port so as to access the surgical site.
15 A typical surgical instrument 103 shown in Figure 3 comprises an instrument interface 301
by means of which the surgical instrument connects to the robot arm 102. A shaft 302
extends between the instrument interface 301 and an articulation 303. The articulation
terminates in an end effector 304 and permits the end effector to move relative to the shaft
302.
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It is desirable to develop a surgical robot able to control an attachable surgical instrument
such that the end effector of the surgical instrument can be positioned in the desired
location relative to a patient and be actuated so as to perform the desired surgical
procedure.
SUMMARY OF THE INVENTION
According to the first embodiment of the invention, there is provided a robotic surgical
instrument as set out in the accompanying claims.
BRIEF DESCRIPTION OF THE FIGURES
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Figure 1 shows a surgical robot and a patient.
Figure 2 shows a surgical robot and associated control system.
Figure 3 shows an instrument.
PCT/GB2021/051786
Figure 4 shows an attachment of a robot arm for interfacing with an instrument.
5 Figures Sa and Sb show a more detailed view of an instrument.
Figure 6 shows an interface of an instrument.
Figure 7 shows a driving mechanism of an instrument.
Figure 8 shows two views of a driving mechanism of an instrument, the driving mechanism
comprising a gearing mechanism. The gearing mechanism comprises two pulleys and two
10 driving elements.
Figure 9 shows a gearing mechanism comprising a toothed belt and a toothed gear.
Figure 10 shows a gearing mechanism comprising a toothed rack and a toothed gear.
Figure 11 shows a gearing mechanism comprising at three straight rods, a toothed rack and
a toothed gear.
15 Figure 12 shows a gearing mechanism comprising one straight rod and one hook shaped
rod, a toothed rack and a toothed gear
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Figure 13 shows a gearing mechanism comprising a push rod.
Figure 14 shows a gearing mechanism comprising more than two pulleys.
Figure 1S shows a gearing mechanism comprising two truncated cones.
DETAILED DESCRIPTION
The following describes a robot comprising a robot arm and an instrument. The arm is
generally of the form seen in Figure 2. The instrument is generally of the form seen in Figure
25 3.
The arm 102 of the robot seen in Figure 2 terminates in an attachment 401 for interfacing
with the instrument, which is seen in Figure 4. The attachment comprises a drive assembly
402 for driving articulation of the instrument 103. The drive assembly interface 402
30 interfaces with the instrument interface 301 seen in Figures 3, Sa and Sb. Moveable
interface elements 403, 404, 40S of the drive assembly interface engage corresponding
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moveable interface elements of the instrument interface in order to transfer drive from the
robot arm 102 to the instrument 103.
The instrument 103 is shown in more detail in Figures Sa and Sb and comprises an end
5 effector 304 for performing an operation. The end effector may be smooth jaws, serrated
jaws, a gripper, a pair of shears, needle graspers, biopsy needles or needles for injecting
drugs. The instrument comprises an articulation 303 between the instrument shaft 302 and
the end effector 304. The articulation comprises several joints which permit the end effector
to move relative to the shaft of the instrument. The joints in the articulation are actuated by
10 driving elements 505, such as cables.
At the distal end of the instrument shaft 302, the driving elements 505 are connected to the
end effector 304 and are used to actuate the joints in the articulation. At the proximal end
of the shaft, the driving elements are secured to interface elements of the instrument
15 interface 301. Figure 6 illustrates an instrument interface 301 comprising instrument
interface elements 602, 603, 60. In this instrument interface, each instrument interface
element is secured to a driving element e.g. instrument interface element 604 is secured to
driving element 605.
20 Figure 7 is a schematic ofthe driving mechanism of an instrument interface of an
instrument. The driving mechanism is preferably located at the proximal end of the
instrument shaft, but may be located at any point between the proximal end of the
instrument shaft and the end effector. A drive assembly interface element 403 (of a robot
arm) engages with the instrument interface element 601 of an instrument. In Figure 7, the
25 driving element 505 is secured at one end to the instrument interface element, and at the
other end to the end effector 304 via a joint 702. The joint forms part of the articulation
303. The drive assembly interface element 403 engages with the instrument interface
element 601 such that motion of the drive assembly interface element is transferred to
motion of the instrument interface element. The instrument interface element is secured to
30 the driving element such that motion of the instrument interface element 403 is transferred
to motion of the driving element 505. Since the driving element is also secured to the end
effector 304, motion of the instrument interface element is directly transferred to motion of
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the end effector. Thus, motion of the drive assembly interface element results in motion of
the end effector. The robot arm 102 transfers drive to the end effector 304 of the
instrument 103 as follows: movement of a drive assembly interface element 403 moves an
instrument interface element 601 which moves a driving element 505 which moves a joint
5 702 of the articulation 303 which moves the end effector 304. In such a driving mechanism,
movement of the drive interface element is transferred to movement of the end effector as
a function of a fixed set of parameters (the length of the driving element, the friction of the
joint etc.) In this way, the ratio of motion of the drive interface element to motion of the
end effector is fixed. i.e. for an instrument with this driving mechanism, the ratio of motion
10 of the drive interface element to motion of the end effector is always the same. In some
cases, this ratio is 1:1. In many examples, the displacement of the driving element is equal
to the displacement of the end effector. In other examples the force exerted by the drive
assembly interface element on the instrument interface element is equal to the force
exerted by the end effector.
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Figure 8 illustrates a first example of a driving mechanism of an instrument. The driving
mechanism comprises a gearing mechanism located between an instrument interface
element and an end effector. In this example, the gearing mechanism comprises a first
pulley 803 and a second pulley 805, two pulleys being disposed about a single axis 809.
The driving mechanism comprises at least one instrument interface element 801. The
instrument interface element is secured to a proximal driving element 802. The proximal
driving element 802 seen in Figure 8 is a single length of cable. Each end of the proximal
driving element is secured to an end ofthe instrument interface element. The proximal
25 driving element is looped around a first pulley 803. The first pulley 803 rotates about an axis
809. A second pulley 805 rotates about the axis 809 of the first pulley 803. Figure 8 shows
that first pulley 803 has a diameter that is larger than the diameter of second pulley 805.
The first and second pulleys 803 and 805 form part ofthe gearing mechanism located
between the instrument interface element 801 and the end effector 807. A distal driving
30 element 806 is looped around the second pulley 805 and is formed of a single loop of cable.
The proximal driving element 802 extends away from the axis 809 in a first direction. The
distal driving element extends away from the axis 809 in a second direction. In the example
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seen in Figure 8, the proximal driving element 802 and the distal driving element 806 extend
away from the axis 809 in opposing directions. In this way, the axis of the first and second
pulleys 809 is located generally in between the proximal driving element and the distal
driving element. The first and second pulleys may be disposed about a common axle 804,
5 coincident with axis 809. The distal driving element 806 is secured to a joint 808. The joint
808 is fixedly attached to an end effector 807. The first and second pulleys 803 and 805
form part of the gearing mechanism, which may be positioned anywhere between the
instrument interface element and the joint.
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CLAIMS
1. A robotic surgical instrument comprising:
a shaft;
an articulation attached to a distal end of the shaft, the articulation
configured to articulate an end effector, the articulation driveable by a distal driving
element;
a driving mechanism comprising:
an instrument interface element secured to an end of a proximal driving
element and configured to engage a drive interface element of a drive assembly,
wherein motion of the drive interface element results in a first displacement of the
end of the proximal driving element; and
a gearing mechanism engaging the proximal driving element and the distal
driving element and being configured to transfer the first displacement of the
end of the proximal driving element to a different second displacement of an
end of the distal driving element.
2. The instrument of claim 1, wherein the gearing mechanism comprises a first pulley
about which the proximal driving element is constrained to move, the first pulley
being configured to rotate about an axis, and a second pulley about which the distal
driving element is constrained to move, the second pulley being configured to rotate
about the same axis, and the ratio of the first and second displacements is a function
of the ratio of the radius of the first pulley to the radius of the second pulley,
wherein the radius of the first pulley is different to the radius of the second pulley.
25 3. The instrument of claim 2, wherein the second pulley is one of a plurality of pulleys
and each pulley in the plurality of pulleys is configured to rotate about the axis of the
second pulley and has a different radius to the first pulley and all other pulleys in the
plurality of pulleys.
30 4. The instrument of claim 3, wherein the distal driving element is constrained to move
about one of the plurality of pulleys and the ratio of the first and second
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displacements is a function of the ratio of the radius of the first pulley to the radius
of the pulley about which the distal driving element is constrained to move.
5. The instrument of claim 4, wherein the ratio of the first and second displacements is
selected from a discrete number of ratios.
6. The instrument of claim 5, wherein the discrete number of ratios is equal to the
discrete number of pulleys in the plurality of pulleys.
10 7. The instrument of any preceding claim, wherein the gearing mechanism comprises a
toothed rack, the first pulley comprises a toothed gear and is configured to engage
the toothed rack such that motion of the toothed rack results in rotation of the
toothed gear.
15 8. The instrument of claim 7, wherein the distal driving element is constrained to move
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about a pulley and the ratio of the first and second displacements is a function of the
dimensions of the toothed rack and toothed gear, and the radius of the pulley.
9. The instrument of claims 7 or 8, wherein the proximal driving element further
comprises:
a first rod secured to the instrument interface element; and
a second rod secured to the toothed rack and configured to moveably engage
with the first rod such that displacement of the first rod results in displacement of
the toothed rack, wherein the ratio of the first and second displacements is a
function of the dimensions of the toothed rack, the toothed gear, the first rod and
the second rod.
10. The instrument of claim 9, wherein the first rod comprises an aperture and the
second is configured to be threaded through the aperture in the first rod.
11. The instrument of claim 2, wherein the first pulley is a first truncated cone and the
second pulley is a second truncated cone.
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12. The instrument of claim 1, wherein the gearing mechanism comprises:
a first truncated cone about which the proximal driving element is
constrained to move;
a second truncated cone about which the distal driving element is
constrained to move; and
an engagement element configured to moveably engage with the first
truncated cone and the second truncated cone so as to transfer rotation of the first
truncated cone to rotation of the second truncated cone.
13. The instrument of claim 12, wherein the ratio of the first and second displacements
is a function of the radius of the first truncated cone at the point at which the
proximal driving element is constrained, to the radius of the second truncated cone
at the point at which the distal driving element is constrained.
14. The instrument of claims 12 or 13, wherein the ratio of the first and second
displacements is a function of the radius of the first truncated cone at the point at
which the engagement element engages the first truncated cone, to the radius of
the second truncated cone at the point at which the engagement element engages
the second truncated cone.
15. The instrument of any of claims 1 or claims 7 to 14, wherein the ratio of the first and
second displacements can take any value from a continuous range of values.
25 16. The instrument of any preceding claim, the instrument comprising a memory and
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being configured to store in memory the ratio of the first and second displacements.
17. The instrument of claim 16, the instrument being configured to transmit to the
control unit, the ratio of the first and second displacements.
18. A system comprising:
a robot arm;
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the instrument of any preceding claim; and
a control unit being configured to determine the ratio of the first and second
displacements.
5 19. The system of claim 18, wherein the control unit is configured to determine the ratio
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of the first and second displacements using information transmitted from the
instrument to the control unit.
20. The system of claims 18 or 19, wherein the control unit is configured to determine
the second displacement by measuring the tension in the distal driving element
and/or by measuring motion ofthe end effector of the instrument.
21. The system of any of claims 18 to 20, the robot arm comprising a drive assembly
having a drive assembly interface element, the drive assembly interface element
being configured to engage with the instrument interface element such that motion
of the drive interface element results in motion of the instrument interface
element; and the robot arm being configured to apply a force to the drive assembly
interface element, wherein the control unit is configured to derive the first
displacement from a sensed displacement of the drive assembly interface element.
22. The system of any of claims 18 to 21, the system comprising the instrument of any of
claims 2 to 5, wherein each pulley in the plurality of pulleys of the instrument
comprises a sensor configured to detect whether the distal driving element is
constrained to move about that pulley, and the instrument is configured to
communicate to the control unit, about which pulley of the plurality of pulleys the
distal driving element is constrained to move.
23. The system of claim 22, wherein the instrument is configured to communicate to the
control unit, the diameter of the pulley about which the distal driving element is
constrained to move.
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24. The system of claim 23, wherein the control unit is configured to determine the ratio
of the first and second displacements using the diameter of the first pulley and the
diameter of the pulley about which the distal driving element is constrained to
move.