Page 261 - Flexible Robotics in Medicine

250 Chapter 11

(or wire or cable) driven is basically the same. The term “tendon-driven manipulator” will be used
for the rest of the paper. Flexible manipulators are increasingly utilized in MIS because of its small
size and the fact that the motor is separated from the robotic arm structure [10].

In this chapter, several designs of the paired tendon-driven flexible manipulator are
proposed. Analysis of these designs will be made regarding the working space, the driving
force needed, and the normal stress and shearing stress on the manipulator. In
Section 11.2, the current market and related work will be analyzed. The challenges and
significance will be summarized. In Section 11.3, an overview of the tendon-driven
mechanism will be presented, and the designs of the manipulators will be introduced. In
Section 11.4, the simulation of the different designs using the finite element method
(FEM) will be presented. In Section 11.5, the analysis of the difference between different
designs in terms of different characteristics. In Section 11.6, the experimental result on
one of the designs will be shown. Lastly, the conclusion will be made in Section 11.7.

11.2 Related work

Currently, there are robots using in traditional MIS, such as da Vinci robot developed by
Intuitive Surgical Inc. [6,11]. The instruments such as the HiQ hand instruments provided
by Olympus have benefits such as separate jaw rotation, which is independent, and the
universal handle allows the user to use either left or right hand [12]. However, the
mechanism of these instruments did not fully utilize flexible continuum mechanisms, which
limits the dexterity of the robotic instrument. Most flexible manipulators are inspired by
biological examples, such as OctArm [13 16] with large workspaces and reduced sweeping
areas during the motions. This characteristic makes it more suitable for MIS since it can
avoid interfering with the surrounding organ and improve safety. However, the size of these
manipulators is usually too large to be operated in MIS. For OctArm IV, the outer diameter
is 45 mm which is too large for MIS [13,14]. The highly articulated robotic probe
comprises a two concentric cable-driven snack and each of them alternates between rigid or
limp mode [17]. Switching the mode of limp and stiff for both inner and outer concentric
tubes gives it a 3D working space, with predefined bending curvatures [3] (Table. 11.1).

The constrained tendon-driven serpentine manipulator systems are designed to fully utilize the
benefits of these snake-like a robot and minimize the limitation of the size and motion [7,10].
Using fewer actuators reduces the size of the backend electronic controller. The more
straightforward mechanical system design can reduce the size of the actuator and enable it to be
used in various applications. Three-tendon-driven designs are developed because it requires three
actuators only [18]. A paired tendon-driven robot is another one of the most common designs
because of its intuitive bending motion control [4,19]. Among these designs, the manipulator is
supported by a backbone that can bend and controlled by the wires using actuator. The wires are
being guided by holes throughout the length of the manipulator—the difference in current