IEEE Robotics & Automation Magazine - September 2023 - 96

the robot around its backbone axis and pulling it into or
out of the inspection environment.
■ Control hardware: This includes a programmable logic
controller for low-level control and a
laptop for high-level control and visual
feedback.
■ Joystick interface: This drives the
robot with a user-friendly mapping
that can be taught in a few minutes,
opening these technologies to unskilled
operators.
In this section, the design of COBRA is
discussed, with a focus on the mechanical
solutions for the continuum robot, actuation
pack, and twist-and-feed mechanism.
the system along the desired path. However, complex geometries
and sharp turns can easily prevent a borescope from
moving forward.
The continuum robot of the COBRA sys "
INSPECTION,
CONTINUUM
ROBOT
The active shape control of continuum
robots has clear advantages when operating
in fully suspended configurations (e.g.,
from the ceiling to the ground) and allows
for navigation through complex paths.
However, actuation technologies often limit
the length and number of independently
drivable segments. Conversely, passive borescopes are manually
guided by pushing them into cluttered environments,
combining axial translation and rotation to overcome obstacles.
Despite the lack of control over a borescope's shape,
navigation is made possible by narrow passages that " force "
MAINTENANCE, AND
REPAIR ARE CRITICAL
TO ACHIEVE SAFETY
AND RELIABILITY IN
CAPITAL-INTENSIVE
INFRASTRUCTURES,
SUCH AS AIRCRAFT,
POWER PLANTS, AND
TELECOMMUNICATION
NETWORKS.
„
Twist-and-Feed Mechanism
Actuation Pack
Passive Segment
(b)
tem aims at taking the best of both: with its
long passive segments, it can benefit from
the environmentally guided navigation
strategy of borescopes without the stricter
length constraints of conventional continuum
robots; at the same time, the plurality
of active tendon-driven segments provides
the additional mobility that borescopes lack.
The designs of both passive and active segments
are illustrated in Figure 2.
The passive segment could be as long
as required, although friction losses
limit its length in practice. Its main structural
component is a thin rubber-coated
braided monocoil tube at the outer surface
[Figure 2(a)], braided to minimize
deformation under torque. Internally, coil
springs serve as Bowden outer cables for
the tendons and help to minimize friction
when actuating the active segments. The
remaining space can be used to deliver power, signals, fluid
pressure, etc. to the EE.
The active segment is a tendon-driven, multibackbone continuum
robot with pivot disk vertebrae that roll onto each other
[Figure 2(e)]. At the terminal vertebra of each independent
(c)
Control Laptop
EE
EE Camera View
Joystick
(a)
Active Segment
(d)
FIGURE 1. An overview of the COBRA system. (a) The setup with a control laptop, a joystick controller, a 5-m continuum robot with active
(light gray) and passive (dark gray) segments, an actuation pack for the tendon-driven active segment, and a twist-and-feed mechanism
for the passive segment. (b) Pulleys for tendon driving and routing in the actuation pack. (c) The 6-DoF active segment with a camera
EE. (d) The linear and rotary stages of the twist-and-feed mechanism.
96 IEEE ROBOTICS & AUTOMATION MAGAZINE SEPTEMBER 2023

IEEE Robotics & Automation Magazine - September 2023

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - September 2023