IEEE Robotics & Automation Magazine - September 2023 - 104

installing the feed-and-twist mechanism directly onto the
access port [Figure 8(a)].
NUCLEAR
The second demonstration of COBRA, shown in Figure 9,
relates to pipeline inspection in nuclear power generation installations.
After attaching the twist-and-feed mechanism onto an
opening [Figure 9(a)], the continuum robot
was driven through the pipes [Figure 9(b)],
inspecting difficult-to-reach regions [e.g.,
due to corners, as in Figure 9(c)] and the
pipe ceiling [Figure 9(d)]. The latter highlights
the advantages of the active segment:
a full tip bend around a corner
while suspended, as in Figure 9(c), cannot
be achieved by a conventional borescope,
limiting the number of reachable pipe lines;
furthermore, a conventional borescope
would not be able to lift its EE as in Figure
9(d), thus either not achieving full
inspection or only giving a distant visual
feedback with limited information (i.e., a
low-quality image or being out of range for depth measurement
or intervention). At the same time, a fully actuated continuum
robot might be hindered by the need to achieve follow-the-leader
motion over a long reach within this target environment, thus
leading to hybrid designs like COBRA as the only solution for
such operations.
"
„
THROAT SURGERY
In this application, illustrated in Figure 10, we show how the
modularity of COBRA enables medical applications with a
novel EE, designed for minimally invasive throat surgery.
Existing robotic surgical systems, such as the da Vinci [19], are
usually constrained to a specific application or do not have
enough flexibility or DoF for this specific application. Endoscopes
are instead limited to 2 DoF and one single task at a
time. As such, our design has been tailored not only to provide
EE multitasking and multiple DoF but also to enable precise
positioning and control over a small region inside the throat to
assist in throat cancer surgeries.
The EE holds an inspection camera and forks into two miniature
active sections (MASs), which are scaled-down (6-mm)
five-vertebra active segments that provide independent 2-DoF
mobility for two tools: a surgical diathermy cutter and a tweezer
(Figure 10). This design enables the use of the main COBRA
body for coarse EE positioning, whereas the MASs can be finely
tuned to a specific region of interest within the throat with
their own tendon mechanisms, guided through the onboard
camera feedback.
The diathermy cutter is activated by an insulated cable that
passes through the center of the MASs and is connected to
an external diathermy unit for surgery. The tweezers work via
a symmetric tendon-driven four-linkage mechanism, springloaded
to its open configuration [see Figure 10(a)]. The linkage
is optimized for the tweezer tendon to compress the spring
10 IEEE ROBOTICS & AUTOMATION MAGAZINE SEPTEMBER 2023
4
AIRCRAFT ENGINES
REPRESENT ONE OF THE
MOST CHALLENGING
BORESCOPE INSPECTION
SCENARIOS.
with a minimum load and achieve the grasping force required
to remove the tissue cut with the diathermy cutter without
compromising the configuration of the EE or the active section
of COBRA. The advantage of having 2 DoF on each MAS
is that the diathermy cutter and the tweezers can perform
actions simultaneously in the center or separately by moving
the MASs away from each other [see Figure 10(a) and (b)].
Both MASs and the camera have an initial
tilt angle for the optimal camera field of
view and for maximizing the workspace
intersection of the two MASs. With this
design, the robot is able to perform the
surgical procedures that are daily encountered
when dealing with throat cancer subjects,
such as cauterizing or cutting tissue
(e.g., tumors or injured tissue) and removing
it from the body.
Using a soft polymeric head and neck
replica, this robot was proven to successfully
access the throat through the proper
manipulation of the main COBRA body
[Figure 10(d)], and MAS operation was validated
on organic tissue. Consequently, this application shows
the versatility of COBRA, making it a suitable design for difficult-to-access
environments where either single or multiple
tasks are performed in situ.
CONCLUSION
In this work, we introduced COBRA, a novel continuum
robot design for intervention in hard-to-reach areas. By combining
design solutions from both borescope and continuum
robot technologies, the proposed design overcomes many of
the intrinsic limitations of those systems:
■ A 6-DoF active segment, whose shape is fully controlled,
enables navigation through complex environments.
■ A passive segment with high compliance is used to
achieve a long reach, overcoming the backbone length
constraints of fully actuated designs. As such, the proposed
design achieves a length-to-diameter ratio that is
significantly higher than that of conventional continuum
robots (i.e., 625 and up to 125-150 in active slender
robots).
■ A modular actuation with a motor pack for the tendondriven
segment and a separate mechanism to drive the
passive parts ensures enough DoF to deliver the EE to
the target workspace while enabling an intuitive mapping
to a joystick controller for a user-friendly interface
that significantly reduces the task complexity for
operators.
Appendix
Supplementary videos can be found online at
* https://www.youtube.com/watch?v=BlhULsPVgLU
* https://www.youtube.com/watch?v=GJoAQ1KxaVw&t=1s.
https://www.youtube.com/watch?v=BlhULsPVgLU https://www.youtube.com/watch?v=GJoAQ1KxaVw&t=1s
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