Page 85 - Flexible Robotics in Medicine

Cable-driven flexible endoscope utilizing diamond-shaped perforations: FlexDiamond 69

c. Entrance conduits that are more rigid than the conducting conduits but still flexible;
d. Control region that is capable of end-effector control via a cable transmission
system;
e. Mountable imaging system for the purpose of surveillance and assisting insertion.
f. Perforations that provide manipulation advantages to increase flexibility in bending and
translational extensions/contractions; The perforations adopt a diamond configuration
defined by four points and four straight lines that connect the points.

The new diamond-shaped perforations on the conduit allow the camera to zoom forward
and backward without affecting the epithelium of the nasal floor and turbinates. This
reduces discomfort and makes the prototype safe to use during the insertion. Further, the
zoom function does not require additional workspace, which is of limited anatomical
dimensions. As a soft robot, soft materials are used to improve compliance of the prototype
and reduce the risk of mechanical damage to the surrounding tissues.

The third advantage would be the inclusion of an additional DOF, which current
endoscopic techniques do not confer. As mentioned earlier, this allows us to perform a
localized zoom at the end effector without affecting the transmission region, which is
more comfortable and safer for the subject. Additionally, this third DOF allows the
prototype to mediate obstacles, if any. For a single point, there is more than one solution
to the inverse kinematics.
Cables that run parallel to the axis of the conduit control the bending portion such that
two cables will control the bending in one plane. This is mirrored to include two planes
for bending. When all four cables are taught, the conduit can compress. This conduit can
be made of elastic materials such as nitinol, shape memory polymer, or ceramics to
provide restoring forces to the conduits when the string tension is removed. In the current
2
prototype, we utilized a concentric spring (0.03 0.008 kg/s ) to provide this restorative
force. Tension applied to the string will cause it to transfer this force to the ends via
deformation. By reeling in the spring for the left portion and providing slack for the right
portion will allow the manipulator to bend left. This reeling can be done manually such as
with mechanical gears and knobs or with motors such as step motors. This specific degree
to reel to induce the desired bending can be varied depending on the intended function.
The larger the bending angle required, the more displacement of the string is required.
Thus more cable needs to be reeled in. This mode of action is analogous to the native
human kinematic actuation wherein. There are at least two muscle groups acting
antagonistically to develop the moment. The novelty is shown in Fig. 3.1, where there are
diamond cuts in the conduit to allow increased flexibility in three degrees of motion while
maintaining the mechanical integrity of the conduit. It includes channels for which the
cables can run through the shell in order to enable bending. The diamond-shaped
perforations are not uniform across the entire conduit and can be varied across the axis.