IEEE Robotics & Automation Magazine - September 2023 - 102

FOLLOW-THE-LEADER ALGORITHM
A lightweight discrete algorithm has
been developed to enable follow-the-lead
deployment [17], as shown in Figure 6.
The robot's whole backbone length 0, can
be discretized into short discrete intervals
T , (e.g., 1 mm for the reported example).
While feeding the robot in the workspace,
the exposed length of the robot
, t^h
(a)
(b)
(acquired by the optical sensor on the feed
axis) increases, and the current actuation
of the active segment is recorded for each
T , of exposed length and stored in a discrete
array. By assuming that the passive
segment follows the active one because of
environmental constraints, the shape of
the whole robot can be indirectly acquired
by recording actuation variables during
deployment. When extracting the robot,
the stored values replicate the active
motion backward.
(c)
(d)
FIGURE 8. The aerospace demonstration. (a) The feed-and-twist mechanism installed
onto the outer case of an aeroengine. (b) The active segment entering the engine
from a borescope access port. (c) The EE of the robot performing a visual inspection.
(d) Navigation around the engine core.
USER INTERFACES
While teleoperation through TCP/IP or keyboard
commands is possible, COBRA is
equipped with a Thrustmaster T16000 controller
for manual operation with a userfriendly
mapping of the motion variables
(Figure 7) onto this dissimilar-kinematic
device [18]. The twist-and-feed mechanism
is controlled through the main stick [the
wrist of the driving hand, shown in Figure
7(c)], with forward and backward push
controlling the feed velocity ,o
motion mapped onto the twist { 0 (up to
(a)
(b)
(c)
±120° to prevent cable entanglement). A trigger
(the index finger of the driving hand) is
configured to enable these controls, ensuring
that letting go of the joystick results in a
complete stop of all motors. The smaller
joystick on top of the main stick [the thumb
of the driving hand, shown in Figure 7(b)] is
mapped onto the active section, imposing a
fixed bending velocity ijo
in the i{ direc(d)
(e)
FIGURE
9. The nuclear demonstration. (a) The inspection target (vertical layout).
(b) The feed-and-twist mechanism installation. (c) The pipeline navigation. (d) The
camera EE with the LED lights on. (e) Lifting the EE with the active segment to
perform ceiling inspection (horizontal layout).
10 IEEE ROBOTICS & AUTOMATION MAGAZINE SEPTEMBER 2023
2
tion the stick is pushed. The thumb joystick
controls only the tip when following the
leader; alternatively, each active section can
be independently selected with the base buttons
[the fingers of nondriving hand, shown
in Figure 7(a)], and the remaining controls
can be mapped to EE functions (e.g., the
camera LED intensity, image capture, and
tool operation).
The immediacy of this interface allows
even inexperienced users to quickly learn
how to operate the system and reduces the
and lateral
IEEE Robotics & Automation Magazine - September 2023

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