U.S. patent application number 16/521500 was filed with the patent office on 2021-01-28 for hydraulic instrument drive system for minimally invasive surgery.
This patent application is currently assigned to TransEnterix Surgical, Inc.. The applicant listed for this patent is TransEnterix Surgical, Inc.. Invention is credited to Sevan Abashian, Anthony Fernando, Kevin Andrew Hufford, Alexander John Maret, Matthew Robert Penny, Paul Wilhelm Schnur, Dustin Vaughan.
Application Number | 20210022718 16/521500 |
Document ID | / |
Family ID | 1000005180550 |
Filed Date | 2021-01-28 |
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United States Patent
Application |
20210022718 |
Kind Code |
A1 |
Maret; Alexander John ; et
al. |
January 28, 2021 |
Hydraulic Instrument Drive System for Minimally Invasive
Surgery
Abstract
A robotic surgical system includes a hydraulic drive system and
a surgical instrument removably positioned in operative engagement
with the hydraulic drive system.
Inventors: |
Maret; Alexander John;
(Apex, NC) ; Fernando; Anthony; (Chapel Hill,
NC) ; Penny; Matthew Robert; (Holly Springs, NC)
; Hufford; Kevin Andrew; (Cary, NC) ; Schnur; Paul
Wilhelm; (Pipersville, PA) ; Abashian; Sevan;
(Raleigh, NC) ; Vaughan; Dustin; (Raleigh,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TransEnterix Surgical, Inc. |
Morrisville |
NC |
US |
|
|
Assignee: |
TransEnterix Surgical, Inc.
Morrisville
NC
|
Family ID: |
1000005180550 |
Appl. No.: |
16/521500 |
Filed: |
July 24, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US18/16324 |
Jan 31, 2018 |
|
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16521500 |
|
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62452953 |
Jan 31, 2017 |
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62452950 |
Jan 31, 2017 |
|
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62585655 |
Nov 14, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/00 20130101;
A61B 46/10 20160201; B25J 9/14 20130101; A61B 34/30 20160201; A61B
2017/00539 20130101 |
International
Class: |
A61B 17/00 20060101
A61B017/00; A61B 34/30 20060101 A61B034/30; A61B 46/10 20060101
A61B046/10; B25J 9/14 20060101 B25J009/14 |
Claims
1-23. (canceled)
24. A surgical system comprising: an arm; a drive module on the
arm, the drive module comprising a plurality of hydraulically
driven first pistons; a surgical instrument including a plurality
of second pistons, each second piston linearly aligned with a
corresponding one of the first pistons, such that
hydraulically-driven translation of a first piston results in
translation of the corresponding second piston to effect motion of
a portion of the surgical instrument.
24. The system of claim 24, wherein the motion is selected from the
group consisting of roll, articulation, bending, jaw actuation, or
linear translation.
25. The system of claim 24, further including a drape disposed
between the first pistons and the second pistons.
26. The system of claim 25, wherein neither the drive pistons nor
the driven pistons extend through the drape.
27. A surgical system comprising: an arm; a drive module on the
arm, the drive module comprising a plurality of hydraulically
driven rotational elements; a surgical instrument including a
plurality of rotational elements, each second rotational element
operatively associated with a corresponding one of the first
rotational elements, such that hydraulically-driven rotation of a
first rotational element results in translation of the
corresponding second rotational element to effect motion of a
portion of the surgical instrument.
28. The system of claim 28, wherein the motion is selected from the
group consisting of roll, articulation, bending, jaw actuation, or
linear translation.
29-33. (canceled)
34. A hydraulically driven surgical instrument including: a housing
having a fluid pathway with fluid therein, a first piston in one
end of the fluid pathway and a second piston in a second end of the
fluid pathway, a rotatable element positioned in the fluid pathway,
the rotatable splined element coupled to an actuator of a surgical
instrument such that advancing the first piston drives the
rotatable element in a first direction causing motion of the
actuator in a first direction, and advancing the second piston
drives the rotatable element in a second direction causing motion
of the actuator in a second direction, wherein diameters of the
piston and the volume of fluid captured between the fins of the
splined element are selected to achieve a desired ratio of input
piston travel to rotational output of the splined element.
Description
[0001] This application is a continuation of PCT/US18/16324, filed
Jan. 31, 2018, which claims the benefit of the following US
Provisional Applications: U.S. 62/452,953, filed Jan. 31, 2017;
U.S. 62/452,950, filed Jan. 31, 2017; and U.S. 62/585,655, filed
Nov. 14, 2017.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
surgical instruments and systems. In particular, this invention
relates to fluid actuation and/or movement of surgical instruments
or their end effectors.
BACKGROUND
[0003] Surgical systems used for robotically-assisted surgery or
robotic surgery employ electromechanical drivers to drive movement
of surgical devices within a body cavity, typically in response to
signals generated when a user moves a user input device. The
surgical devices may be surgical instruments having end effectors
and/or they may be steerable lumen devices adapted to receive such
surgical instruments.
[0004] One of the benefits of robotic assistance for minimally
invasive surgery is that it enables the surgeon to control more
complex and highly dexterous instruments with minimal mental and
physical effort. In robotic surgery, the surgeon manipulates a
master input device at a surgeon console to remotely operate
instruments inside the patient. The signals from the input device
are interpreted by the robot control system and used to drive
mechanisms which move the instruments.
[0005] The gross motion of the instrument is typically achieved by
a robotic manipulator arm which moves the entire instrument
assembly in space. To supplement this gross motion, fine motion of
the instrument tips is delivered through mechanisms which are built
into the instruments themselves. In such systems, it is desirable
to avoid the need to sterilize components housing motors and
electronics. Instead, prior art surgical systems provide the driver
(which houses the motors and some electronics) as a component on
the manipulator arm that may be covered with a sterile drape in the
surgical procedure room. The surgical instrument that is to be
driven by the driver is a separate, sterile, component removably
mounted over the sterile drape in a manner that allows the sterile
drape to maintain a sterile barrier between the driver and the
surgical device. Features are provided for transferring the
mechanical output of the motors in the driver to the actuation
elements in the surgical device, so that actuation of the motors
causes the desired movement of the surgical device within the
patient's body cavity.
[0006] Some prior art systems use rotary couplers for this purpose,
to transmit motion from the robotic engine on the manipulator arm,
through a sterile drape covering the arm, and into receiving
couplers on the surgical instrument. In these systems, mechanisms
inside the instrument convert this rotary motion into movements of
the instrument end effector (jaw open close, articulation, etc.),
typically using features such as wristed joints, articulating
vertebrae, etc. In highly dexterous instruments such as high degree
of freedom wristed instruments and fully articulating instruments
for single-port surgery, an even more significant portion of the
motion of the end effector is transmitted through the instrument
via couplers.
[0007] In some cases, motors are built into the instruments
themselves to control the instrument articulation, and driven using
power received via an electrical contact in the drape.
[0008] Commonly owned, WO 2016/057989 (the '989 application), which
is incorporated by reference, describes a surgical system that
overcomes challenges of the prior art systems by eliminating the
need for rotary coupling through the drape. That application
describes a system that includes a drive unit on a support. The
drive unit includes motors or other actuators and a plurality of
output elements arranged such that operation of each drive unit
linearly translates a corresponding one of the output elements. A
surgical device has actuation elements extending through an
elongate shaft to a distal articulation section, and an input
subsystem carried at the proximal end of the shaft. Linear
translatable input elements or pistons of the input subsystem are
each associated with a corresponding one of the actuation elements.
The input and output elements are positioned such that operation of
an actuator linearly translates an output element, causing linear
translation of a corresponding input element and engagement of an
actuation element. A sterile drape is positionable between the
input elements and the output elements. The described system thus
allows use of a sterile drape without the requirement of special
adapters or rotary couplers for transferring motion. Input devices
operable by the surgeon allow a surgeon to provide input to the
system for the purpose of driving the motors to move the surgical
devices.
[0009] Some detail of the system described in the '989 will now be
given, because that type of system may be configured to drive
surgical instruments using the hydraulic system of the type
described in this application. FIG. 14 shows a surgical instrument
of the type discussed in the '989 application. The surgical
instrument 12 is designed to be inserted through an incision
(either directly or through a trocar or overtube) and positioned
within a patient's body for use in performing surgery. The surgical
instrument may be one having an end effector 23a that can be
steered, articulated, and/or actuated (e.g. jaw opening and
closing) having an end effector 23a, although it may be replaced
with a steerable lumen device adapted to removably receive such
surgical instruments. The surgical instrument includes actuation
elements that, when pushed and/or pulled, cause active bending
and/or articulation at the distal portion of the surgical device
within the patient's body. The actuation elements extend through
the shaft and are positioned to cause active bending/straightening
of corresponding actively bendable sections, or articulation at
joints or pivots, as the tension on the actuation elements is
varied. The actuation elements are elongate elements (e.g. wires,
rods, cables, threads, filaments etc.) having distal portions
anchored to the shaft and proximal portions coupled to actuation
mechanisms that vary the forces (tension or compression) on the
actuation elements or the positions of the actuation elements. The
actuation elements generally extend between proximal and distal
directions.
[0010] The surgical instrument depicted in FIG. 14 includes an
elongate shaft 16 having a rigid proximal portion. Towards its
distal end there are one or more actively bendable or "steerable"
sections 18a, 18b that bend in response to movement of the
actuation elements. For example, steerable section 18a might be
steerable in two degrees of freedom using steering actuation
elements (e.g. three or four such elements) terminating at the
distal end of the steerable section, and steerable section 18b
steerable in at least one degree of freedom to move the distal end
of the shaft laterally outward or inward in one degree of freedom
using actuation elements, and which may be additionally moveable in
a second degree of freedom. The numbers and combinations of
actively bendable and jointed articulating sections, degrees of
freedom, and actuation elements can be varied from what is
shown.
[0011] FIG. 15 shows the instrument 12 spaced apart from a motor
drive 14. Motor drive 14 houses the motors whose output is used to
drive the actuation elements for the steerable and/or articulating
sections, and/or for the opening/closing of instrument jaws, as
applicable. The motor drive 14 is preferably supported on a support
arm, robotic manipulator arm, or alternate support (not shown).
[0012] The motor drive 14 includes motors (not shown) and output
elements 26, which in the drawing take the form of pins or posts.
When the motor drive 14 and surgical device 12 are assembled, each
such output element 26 is in contact with, coupled to, or engaged
with a corresponding input element 28 of the surgical device 12, or
otherwise positioned to cause each input element 28 to move in
accordance with its corresponding output element 26. In preferred
configurations, the input and output elements are on opposite sides
of a sterile drape covering the motor drive 14 and the robotic arm,
with the instrument 12 being removably positioned on the motor
drive. This allows the instrument 12 to be exchanged with other
sterile instruments during a surgical procedure while maintaining
sterility of the surgical field.
[0013] The system may be set up so that the output elements 26 push
the input elements 28 in response to motor activation, and/or so
that the output elements pull the input elements 28. Each of the
input elements corresponds to a degree of freedom of motion, or to
end effector actuation, of the surgical instrument. The robotic
system controllers activate motors of the motor drive 14 in
response to surgeon input at the input device to cause movement of
the output elements 26 so as to produce the desired movement,
articulation or jaw actuation of the instrument.
[0014] Commonly-owned application WO/2017/181153 describes ways in
which the linear drive can be used to effect an axial roll of the
instrument.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 schematically illustrates subsystems of a hydraulic
surgical end effector drive system.
[0016] FIG. 2 is a block diagram schematically illustrating
components of a robotic surgical system employing the hydraulic
surgical end effector drive system of FIG. 1.
[0017] FIG. 3 schematically illustrates elements of the input
pressure system of FIG. 1.
[0018] FIGS. 4-6 give examples of pump configurations that may be
used for the input pressure system of the system of FIG. 1.
[0019] FIG. 7 illustrates one configuration of a hydraulic surgical
end effector drive system incorporated into a surgical robotic
system.
[0020] FIGS. 8-12 illustrate configurations for transferring force
and motion through a surgical drape using hydraulics.
[0021] FIG. 13 shows a configuration for transferring force and
motion using hydraulics to effect instrument roll.
[0022] FIG. 14 illustrates a prior art surgical instrument for a
robotic-assisted surgical system.
[0023] FIG. 15 illustrates the instrument of FIG. 14 in exploded
view with a motor drive for actuating movement of the surgical
instrument.
DETAILED DESCRIPTION
[0024] This application describes a robotic-assisted surgical
system incorporating a hydraulic surgical end effector drive system
10 (HSEEDS), a system in which fluid is used to transfer motion and
force to instrument end effector. In general, this concept uses
pressurized fluid (either gas or liquid) to impart motion and force
on the instrument end effector. It is understood that this concept
applies both to single-site surgical robotics as well as multi-port
applications. This application discusses a system in which the
fluid subsystem is a part of the surgical instrument, and also a
concept in which the fluid subsystem is a part of the drive system
used to provide input forces and motions to the surgical
instrument. As both subsystems are covered in this disclosure, the
HSEEDS invention consists of a complete drive system in which one
or both subsystems are achieved using fluid to transfer forces.
[0025] The embodiments discussed in this disclosure focus on
mechanisms to transmit linear motion, such as is described in the
'989 application, but it is understood that this invention would
also apply to similar mechanisms which utilize rotary motion which
are also driven by fluid pressure (for example using rotary
hydraulic actuators). The drive system may control the motions of
the mechanism by controlling the fluid pressure directly, by
controlling the position of an input drive mechanism (such as an
input piston) directly, or by monitoring and controlling both
position and pressure. To simplify the discussion, this application
refers to this system as a "hydraulic" instrument drive system,
with the understanding that the fluid being used in the system may
be either a liquid or gas. There are some differences in system
design and analytical complications between a liquid system and a
gas system, which are discussed briefly at the end of this
application.
[0026] The HSEEDS 10 consists of three subsystems, the input
pressure system (IPS) 12, the mechanical transfer system (MTS) 14,
and the instrument end effector output system 16 (IEEOS) as
schematically depicted in FIG. 1. In the system 10, the IPS 12
and/or the IEEOS 16 are driven using a fluid system. One may be
mechanical or electromechanical, but at least one is driven
hydraulically. In the case of a fluid IPS, the IPS delivers and
regulates the fluid pressure delivered to each input mechanism of
the MTS. The MTS then transfers this fluid pressure and motion to
the input side of the IEEOS, and the IEEOS converts these input
forces and motions into motions and forces of the instrument end
effector tips. The IPS referred to in this disclosure could be
designed and built in a number of different ways, but two potential
embodiments are discussed below.
[0027] The system may be incorporated into a robotic surgical
system as schematically depicted in FIG. 2. A surgeon provides
input to the system via a user input console. A robot control
system generates instructions based on the user input in order to
control the robotic manipulator arm for certain types of instrument
movement, such as gross motion of the instrument, and to control
the HSEEDS system which effects finer motion of the instrument,
such as shaft articulation or bending, wristed motion of the end
effector, jaw actuation, etc.
[0028] The Input Pressure System (IPS) A first embodiment of an IPS
includes individual electrically powered and controlled dynamic
pumps (such as centrifugal pumps or axial-flow pumps or equivalent)
to provide pressure to each degree of freedom of the MTS. For
example, each pump could be dedicated to manipulating one input of
the MTS of a linear push-push instrument drive mechanism such as
that described in WO 2016/057989. If enough pushing and pulling
force is required, two pumps may be needed for each degree of
freedom of the MTS so that a double acting piston can be used to
both push and pull. This could also be achieved with a single pump
if a mechanism such as a valve is used to direct the pressurized
flow to either side of the double acting piston. Also, in the
push-push system described in this disclosure, pull forces are not
needed and therefore a single acting piston would suffice. Double
acting pistons would be part of the MTS and are discussed in the
MTS section below. The IPS subsystem may consist of a main fluid
reservoir or tank, a hydraulic accumulator, one or more filter
assemblies, electrohydraulic servo valves or proportional valves,
pumps, pressure relief valves, flowmeters, temperature sensors,
heat exchangers, etc. In one embodiment, each pump may draw fluid
from a main input reservoir and supply pressurized output fluid to
the MTS input. The pressure, flow rate, and position of the flow to
the MTS may be controlled by the robot control system using a servo
valve, proportional valve, or similar. Alternatively, these flow
conditions provided to the MTS from the IPS could be controlled and
monitored using flow control valves, pressure relief valves,
flowmeters, temperature sensors, pressure transducers etc. The
fluid may be transferred from the IPS to the MTS through flexible
or rigid tubing, piping, or internal passages.
[0029] An alternative concept for a hydraulic IPS uses
electromechanical actuators and motors (or equivalent) to drive
positive displacement pumps (such as a piston or plunger) to
control the position and pressure of each degree of freedom of the
MTS. This would share many of the benefits of the first embodiment,
but could be realized with fewer hydraulic components, a more
familiar electromechanical input system to the hydraulic drive, and
potentially less noise and power consumption depending on the type
of dynamic pump used in the first concept described. This IPS with
positive displacement pumps driven by electromechanical actuators
may still use pressure transducers, temperature sensors, etc. for
input into the control system. Also, it is likely that a pressure
relief valve will be integrated as a failsafe into the output side
of the pump to avoid excessive pressure if there is a failure in a
sensor or the control system. For this type of system, the input
position of the piston (or positive displacement pump) can be
commanded directly to control the position of the inputs of the
MTS. Because this is not a dynamic pump and the hydraulic portion
of the system is likely "closed" (without the reservoir of the
first system), effective sealing must exist to prevent leaks and/or
a reservoir must exist with a mechanism to maintain or refill fluid
in the line either during use or between uses.
[0030] Using a hydraulic IPS can provide some advantage over prior
art systems. First, flexible tubing can enable improved form factor
design by positioning the IPS in a more favorable location in the
robotic surgical system without the need for a drive system built
directly adjacent to the MTS. For example, in previous push-push
system designs, the motor packs, gearing, and linear actuators are
all mounted in series along the pin axis. This results in
significant weight and volume of mechanisms out near the
instruments at the end of the robotic manipulator arm. Using a
hydraulic IPS as part of this HSEEDS invention enables the IPS to
potentially be positioned in the base of the robotic manipulator
cart rather than mounted to the manipulator itself. Hydraulic
flexible tubing can be routed through the center of the robotic
arm. This would enable smaller, lighter, manipulator arms which
occupy less space around the surgical site. Additionally, moving
the pumps or drive engines into the base of the arm makes heat
removal much simpler, and also enables the use of larger motors at
more optimal operating points. This should reduce overall heat
generation, simplify cooling, and use less power.
[0031] Another advantage to using a hydraulic IPS is the ability to
obtain haptic information, which can be used to provide feedback to
the surgeon, without integrating separate and expensive load cells.
Using a pressure transducer in the tubing on the output side of the
IPS, the control system can monitor the pressure, and therefore
force or torque being applied to the instrument mechanism. The
pressure on each degree of freedom of the IPS will tell the control
system the forces on each input mechanism to the MTS. Assuming an
MTS design that is relatively low friction and back drivable, these
measured forces will be proportional to the forces being applied to
the instrument degrees of freedom. As such, the pressures measured
at the IPS can be used to calculate surgical forces such as jaw
open-close, forces in X, Y, Z, and moments about X, Y, Z, depending
on the degrees of freedom of the instrument in use.
[0032] The Mechanical Transfer System (MTS)
[0033] Accepting the output of the IPS is the MTS for which a
number of different mechanisms could be used. In this disclosure,
the MTS is described as the mechanical system used to transfer the
hydraulic input forces and motions from the IPS, to the instrument
input mechanism in a useful way. Essentially, the MTS converts the
pressure and motion of the fluid to motion that can be accepted by
the instrument. As previously discussed, this disclosure focuses on
axial motion for a push-push instrument mechanism, but rotary
motion or other motion is also feasible with a hydraulic
system.
[0034] A first concept uses a piston, actuated along an axis by the
fluid pressure, and utilizes a sliding sealing interface to
maintain fluid pressure as the piston moves. In this design, the
relationship between speed and force of the MTS vs the speed and
force generated by the pump in the IPS can be controlled by the
pressure area of the pistons in the MTS. This is very analogous to
gear ratios in a purely mechanical system. Consider the second IPS
concept. If the area of the MTS piston is 2.times. larger than the
area of the plunger in the IPS, the force exerted on the MTS will
be 2.times. the force applied to the plunger of the IPS. Also, if
the IPS plunger moves a certain distance (at constant pressure),
the MTS piston will move 1/2 the distance. These ratios can be
controlled in the mechanical design to optimize the relationship
between input forces and speeds to output forces and speeds. A more
complex mechanism could also be designed which could dynamically
change the pressure area one or more of the pistons enabling the
control system to modify the input/output relationship based on the
type of instrument being used or the demands of the surgeon,
application, or conditions. This type of transmission system could
be designed with discrete steps or nearly continuous ratios.
Another consideration for this piston system is that it may be
necessary to use double acting pistons to achieve the required push
and pull forces demanded to manipulate the instrument end effector
under load. With these double acting pistons, it may be useful to
have two pumps for each degree of freedom of the MTS, one to apply
pressure on one side of the mechanism and one to apply pressure on
the other. Alternatively, a spring can be used in the piston to
provide pull force when the IPS relieves pressure. This would
enable a single pump in the IPS per degree of freedom in the MTS.
Also, with a push-push system pull forces are not needed as each
pin is only used to push.
[0035] A second concept uses a flexible membrane, such as a
bellows, to extend along an axis under pressure, which would be
completely closed and therefore would not require any sliding seals
in the MTS. In this design, pressure from the IPS pressurizes the
inside of the bellows which then expands axially to move and exert
force on the input mechanism of the instruments. Similar to the
double acting piston concept, the bellows concept could be applied
to exert higher push and pull forces by using a dual bellows
concept for the MTS with 2 input pumps in the IPS for each degree
of freedom of the MTS. One bellows is pressurized for push, and one
for pull. Alternatively, a single bellows may be feasible by
designing a nominal spring force into the bellows system to exert
pull force when pressure is reduced at the IPS.
[0036] The Instrument End Effector Output System (IEEOS)
[0037] The IEEOS transfers motion from the MTS to the instrument
end effectors. In prior art, this is typically achieved with cables
or rods which are actuated by rotary or axial motion imparted to
the instrument from the motorized robotic engine at the end of a
robotic manipulator arm. The HSEEDS invention may be realized with
either a prior art mechanical instrument system or with a hydraulic
IEEOS. In this hydraulic IEEOS, input motion from the MTS is
transmitted to the end effector by hydraulic lines inside the
instrument. The fluid used for the hydraulic actuation is contained
inside the instrument tubing and is fully sealed.
[0038] This concept does not need much explanation beyond that
provided in previous sections. For a hydraulic IEEOS, the force and
displacement of the MTS provides the input to the hydraulic lines
inside the instrument which in turn pass this energy to the
instrument end effector. On the input side of the IEEOS, pistons or
a bellows can be used to engage with the MTS and transfer the
motion and force of the MTS to the motion and pressure of the
hydraulic lines. On the output side at the instrument end effector,
a mechanism is used to again convert this pressure and motion of
each hydraulic line into mechanical motion of the degrees of
freedom of the instrument end effector (such as a wrist, jaw
open-close, etc.). Depending on the desired motion of the end
effector, a number of mechanisms could be used to transform the
hydraulic input to mechanical output such as a piston, bellows,
rotary hydraulic actuator, etc. These mechanisms may then either
directly connect to the instrument end effector or connect to
cables or rods which ultimately impart the motion to the instrument
tips. Similar to the description of the hydraulic IPS, the
hydraulic IEEOS offers advantages to prior art such as the ability
to further separate the input and output mechanisms of the
instrument (i.e. so it does not have to be physically in-line), and
use input and output pressure area ratios as a method of scaling
the relationship between input and output forces and displacements.
Perhaps even more importantly, a hydraulic IEEOS could be capable
of significantly higher forces than prior art systems, as
compression of fluid can withstand greater loads than tension in
thin wire cables. This could be useful for more complex instruments
such as staplers, or in applications requiring strong jaw forces
such as suturing. Again, pressure transducers could be used to
measure pressure in each line of the IEEOS to give force
information to be used for haptic feedback, as described in
previous sections in more detail. Lastly, a hydraulic IEEOS can
include fail safe measures which reduce the chances of catastrophic
failure. By including pressure relief valves, excessive forces can
be limited by ensuring that at a certain maximum level, fluid is
released from the line and the pressure is released. To prevent
contamination, this could easily be released by the valve into an
internal reservoir to prevent leakage outside of the instrument
box. This could be useful to prevent irreversible failure during
use and also for emergency situations that could require the user
to overpower the instrument to move it into another pose. Also, if
the overloading failure is a loss of fluid pressure, instrument
maintenance may be possible enabling longer life and more uses per
instrument. Rather than cables yielding and needing to be replaced
(which causes instruments to be disposed of in lap instruments
today), the released fluid can simply be replaced to refill the
hydraulic lines and regain performance as when the instrument was
new. This could reduce per procedure costs by enhancing reliability
and reuse counts.
[0039] Gas Vs. Liquid
[0040] As mentioned previously, this concept could be realized with
either gas lines (for example air), or liquid lines (such as water,
mineral oil, hydraulic fluid, etc.). Prior discussion in this
disclosure focuses mostly on liquid systems but the same principles
apply in the case of gas. Air may seem to be an appealing choice
for these applications because of the abundance of availability in
the OR. A main reservoir may not be needed if filtering is either
not required or done at the inlet of the system, and system leaks
are less likely to cause damage to other components in the system
or create new hazards in the OR. However, other risks, analytical
challenges, and mechanical design difficulties counteract these
initially perceived benefits.
[0041] The biggest issue with a gas system is compressibility. Gas
is much more compressible than liquid, and therefore when pushing a
piston, the system will need to travel significantly further to
exert the same pressure in a gas system compared to a liquid
system. This causes additional challenges for the mechanical design
as more travel must be accommodated by the system and
inefficiencies in a pneumatic system require higher input forces to
achieve comparable output forces. For pneumatic systems, pumps
typically must run constantly to hold pressure and position where
hydraulic systems do not. As a result, pneumatics lead to less
efficient operations causing more difficult mechanical design
constraints such as higher forces, greater heat generation, larger
pumps, and larger mechanisms than comparable hydraulic systems. To
further complicate the mechanical system, air has a higher bulk
modulus which can be dangerous if there is a failure at high
pressure. Because of this modulus and compressibility, high
pressure failures have significant potential energy that can result
in explosive failures in improperly designed systems. Therefore,
additional measures must be taken to ensure safe design and
operation in certain types of pneumatic systems.
[0042] Compressibility and inefficiencies also complicate the
control system of the robot. Because of these system losses, the
relationship between input forces/motions and output forces/motions
becomes non-linear. This makes the design of a predictable and
precise control system much more difficult and likely would also
lead to more sophisticated sensing requirements for the mechanical
system. For example, at relatively low pressures, a hydraulic
system can be assumed to be approximately incompressible. This
simplification enables separation between pressures and positions.
However, in pneumatics with compressible gases, the pressure must
be known by the system to determine the position of the end
effector since the density of the gas is variable. These
complications make it more difficult to transmit motions and forces
through long pneumatic lines than hydraulic lines and reduce some
of the benefit of this invention over prior art.
[0043] As a result, the focus of this disclosure is on a truly
hydraulic surgical end effector drive system (HSEEDS) due to the
apparent advantages. However, it is understood that pneumatics are
also feasible.
[0044] Non-limiting examples of subsystems suitable for use with
the system described above will next be described.
[0045] FIG. 4 shows a gear pump which may be used as an IPS of the
disclosed system. The gear pump uses meshing spur gears G1, G2 to
pull fluid from a reservoir into the pressurized volume via inlet
I. Gear G1 is driven by a motor, while gear G2 is moved by the
teeth of gear G1. A low-pressure area L pulls fluid in from a
reservoir and a high-pressure area H pressurizes a fluid volume to
perform some desired task. The pressure in both areas can be
monitored to provide force feedback information if desired.
[0046] In this application, the pressurized volume is connected via
outlet O and a hydraulic line to the MTS, which may be a drive
piston that will transmit linear motion at the drape where it can
be received by a corresponding driven piston on the opposite side
of the drape. As the motor pushes fluid into the pressurized
volume, the drive piston responds to the higher pressure by
extending towards the MTS. When the piston encounters force, the
pressure in the pressurized volume will increase. This increased
pressure may be detected by pressure sensors and communicated to
the user to indicate, for example, forces encountered by the
surgical instrument as it moves through the motion resulting from
the piston motion (e.g. instrument contact with tissue during
movement, jaw closing forces). Representations of the force
feedback may include visual or auditory feedback, or delivered as
force feedback on control handles used by the surgeon to cause
movement of the surgical instrument.
[0047] It should be noted that in this embodiment, a hydraulic
fluid is selected to have sufficiently high viscosity so that it
does not seep around or escape the meshing gear teeth.
Additionally, the motor may be designed to allow pressure above a
certain level to back-drive the position of the motor, and as a
result the linear translating pin/piston.
[0048] A second example of an IPS utilizes a swashplate
configuration as shown in FIG. 5. As the motor turns the swashplate
(depicted by arrow A), the swashplate pushes and pulls on the
pistons within their cylinders. Pulling on a piston creates a
vacuum that is filled by fluid in the low-pressure reservoir and
pushing on the piston sends that fluid to the high-pressure area to
exert force towards the instrument. This force may be used by the
MTS, for example, to drive a drive piston of the type described in
the '098 Application.
[0049] A third embodiment shown in FIG. 6 includes a pump that uses
an enclosed fluid volume in a chamber 100 defined by a flexible or
rigid fluidic channel. The rotation of the motor (not shown) is
converted to linear motion, for example with a ball screw of a
linear actuator 102. A pin 104, sealed within the chamber 100 by an
o-ring seal 106, reciprocates within the chamber, pushing and
pulling an enclosed volume of fluid back and forth, which displaces
a second pin 104b that serves as an output pin (MTS) at the drape
interface.
[0050] Pump Positioning
[0051] In preferred embodiments, the system is configured so that
the output from the MTS is located at the distal end of the robotic
arm. The distal end of the arm is then covered by a sterile drape,
and a removable surgical instrument is mounted to the arm so that
its input elements for articulation, actuation etc. of the
instrument may be driven through the drape by operative elements of
the MTS.
[0052] Systems incorporated the hydraulic system may position the
pump at a variety of locations relative to the site where motion is
transferred between the drive components at the drape and the
driven components of the instrument. One option is shown in FIG. 7,
which shows a base 110 supporting an arm 112 such as a robotically
and/or manually moveable support arm for a surgical instrument. The
base may be a cart positioned on the floor, or it may be mounted to
the surgical bed, the ceiling of the operating room, etc. In a more
conventional surgical system, motors would be carried by the arm,
such as in the housing or region 114 (also referred to in this
application as the "engine"), adding significant weight to the
arm.
[0053] In this embodiment, the hydraulic lines 116 extend from a
series of pumps in the base 110 or cart to the housing or region
114 in which the MTS, such as pistons 115a (or rotary elements)
driven by the pumps transfer motion through the drape (not shown)
to the associated driven components 115b on the other side of the
drape. These components 115b extend from a proximal housing 118 of
the surgical instrument 120.
[0054] In other embodiments, the hydraulic pumps are disposed
distally on the arm, such as inside the housing 114, allowing
shorter hydraulic lines to be used than described in the previous
embodiment. For example, shorter flexible hydraulic lines may
connect the pump to the linear drive pin. Alternatively, hydraulic
lines may be molded or machined paths in a manifold. A preferred
manifold is configured to enable optimal placement of the motors
relative to the linear translation pistons disposed at the drape
such that the overall size and mass of the engine is minimized.
[0055] The pressure inside the contained volume of fluid can be
monitored via pressure sensors and that information fed back to the
user interface to inform the surgeon of the forces applied to the
tissue. The lengths, diameters and shapes of the hydraulic lines
are preferably equivalent such that fluid flow through one line is
equivalent to fluid flow in all the others.
[0056] Hydraulic Drape Manifolds
[0057] Referring to FIG. 8, in some embodiments some MTS features
for force and motion transfer may be built into the drape that is
positioned between the instrument and the engine. This would enable
the motor motion to occur in a location that is remote to the
instrument actuator. The drape would include a manifold of
hydraulic lines 122, each hydraulic line having a proximal 124 and
distal 126 end. The proximal and distal ends are compressible and
extendable such that compression of the proximal end 124 resulting
from output from a piston 115a driven by the system's driver 131
(i.e. whether that driver be an IPS as described above or a more
conventional motor system as discussed in the '989 application)
creates extension of the distal end 126. Extension of the distal
end 126 drives a piston 115b operatively coupled to an actuator of
the instrument 118. In this manner, the engine can apply
compression to the drape in one location and have the motion
carried by fluid to another location in the drape to drive a
mechanism in the instrument. The compressibility/extendability of
these motion-coupling features 124, 126 of the hydraulic lines may
come from elastic properties of the material and/or expandable
mechanical features such as bellows.
[0058] FIG. 9 shows a modified version of the previous embodiment,
in which the drape manifolds include a third compressible location
where an action during loading an instrument onto the robotic
system would create a physical engagement between the
motion-coupling features 124, 126 of the drape manifold and the
corresponding engine drive pin/pistons and driven instrument
pistons at the ends of the hydraulic line. For example, the
motion-coupling features may be shaped to capture the corresponding
pins and to securely retain the pins once they have been expanded.
In the illustrated example, the driver pin and instrument pin each
have recesses built into their external surface as shown, so that
during instrument insertion the engine and instrument pins can nest
with the compressible/extensible portions of the drape manifold.
When the manifold is compressed in a third location (such as by the
post 134 in FIG. 9), fluid is driven to the compressible extensible
portions of the manifold 124, 126, inflating them and thus causing
them to engage with the instrument and engine pins. This could be
particularly useful in push/pull applications, i.e. where the
driven pin is actively driven in both inward and outward directions
for instrument operation, so that one drive pin/piston could both
push and pull on the driven piston of the instrument (input pin)
pin to create desired action. An advantage for this particular
method of engaging push and pull is the zero-backlash nature of the
engagement due to the conformity of the hydraulics to the pin
shape. This could eliminate backlash due to part tolerancing, for
example.
[0059] A similar embodiment is represented in FIG. 10, except that
in this embodiment the hydraulic drape manifold enables rotary
motion at the drape interface--where rotary motion from the driver
(e.g. rotary output from a motor) is transferred to rotary motion
at the motion input for the surgical instrument. In the example,
the hydraulic drape manifold is an annular fluid-filled element 136
(or "donut") in the drape. The annular element 134 has a radial
opening 136 that seats around an engine output mechanism or
actuator in the form of a wiper 115a. The instrument attaches to
the drive assembly (above the drape) in such a way as to align a
second wiper 115b with the donut, the instrument wiper being
rotationally offset relative to the engine wiper actuator. This
instrument attachment could constrain the shape of the fluid-filled
drape donut in such a way as to not allow any expansion of the
donut size. As such, if the drape donut cannot expand, movement of
the driver wiper 115a rotationally around the drape donut would
cause movement of the wiper 115b of the instrument attachment due
to the volume of constrained fluid between the two blades. Motion
can be transferred in either clockwise or counterclockwise
directions due to the constrained fluid volume between blades in
either direction.
[0060] Referring to FIGS. 11 and 12, a similar embodiment to the
donut may consist of a fluid filled annular channel formed of an
inelastic material. The channel is fluidly coupled with an inlet
and outlet loop for the hydraulic fluid. In this embodiment, there
is not a driver wiper actuator, instead the hydraulic pump is
fluidly coupled with the loop of the inlet and outlet but is
positioned in a physically remote location (which may be one of the
locations discussed with regard to FIG. 6. An instrument wiper 115b
is positioned in the radial opening 136. Fluid pumped into one side
of the channel would displace the instrument wiper 115b, causing it
to move with rotary motion in a first direction. Fluid pumped into
the opposite side of the channel would move the wiper in the
opposite direction.
[0061] In alternative embodiments, hydraulic manifolds and
constructed into the drape and fluidly coupled to hydraulic pumps
positioned remote from the drape. Such manifolds might include
motion coupling features such as fluidly driven pistons, or
compressible/expandable drape features of the type described above,
that are engaged with or coupled to input pins or other input
features of the surgical instrument.
[0062] As discussed above, a hydraulic system may be used as an
actuator within the instrument itself. In one embodiment, a
hydraulic line extends down the instrument shaft to the end
effector (e.g. a jaw). Pushing or pulling on the column of water
within the hydraulic line could cause the jaw to open or close.
[0063] In another embodiment, a hydraulic drive may also be
implemented for axially rotating (or "rolling") the instrument. In
this embodiment, the surgical instrument is fixed to a gear or
splined shaft 140 that is tightly constrained, much like the rotary
pump described in the FIG. 4 embodiment. See FIG. 13. In this
embodiment, pushing fluid at one side of the splined shaft would
cause rotation of the spline in the direction of applied pressure.
For example, fluid pushed on the arrow A1 in FIG. 13 would cause
clockwise rotation of the spline and corresponding rotation of the
instrument shaft in a first direction. Pushing fluid on the
opposite side (A2) would cause the opposite rotation of the spline
and instrument shaft. This may be particularly useful if there is
not space for a belt or gear at the instrument shaft to transfer
the rotary motion from the instrument actuation interface.
Hydraulics could take up less space in that volume, but still be
capable of applying the same torque to the roll shaft.
Additionally, hydraulics could be a mechanism for scaling the
rotation relative to the linear translational input. For example,
the diameter of the piston can be sized, relative to the volume of
fluid captured between the fins or gear teeth on the driven pinion,
such that 10 mm of stroke on the piston created greater than 360
degrees of rotation on the pinion. Alternatively, 10 mm of stroke
could be 180 degrees rotation, or 720 degrees. The relationship
between the diameter of the piston and the diameter and captured
volume of the pinion are used to determine the force and
displacement characteristics of this system.
[0064] It should be appreciated that although the various
embodiments are described in the context of robotic surgical
instruments, it should be understood that the described concepts
for effecting motion of a surgical instruments might also be used
for instruments such as hand instruments that are not part of a
robotic surgical system.
[0065] All prior patents and applications referred to herein,
including for purposes of priority, are incorporated herein by
reference.
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