Page 22 - Flexible Robotics in Medicine

4 Chapter 1

design of the inner tube and outer tube structure, which are wire-driven alternatively,
forming the “follow-the-leader” motion control in the operation area. The inner and outer
tube structure is shown in Fig. 1.1B.

1.2.2 Typical mechanical design

Flexible snake-like surgical robots can be realized by the tendon-driven (or can be called
cable-driven, wire-driven) structures.

1.2.2.1 Tendon-driven mechanisms for surgical robots

MIS or NOTES require a continuum manipulator with a small diameter but lumen for the
observation and end-effector instruments. Except for the compact design of the shape, it
should be convenient to be sterilized. Furthermore, except for the electrosurgical unit, the
inside manipulator should not release heat due to motor drive. Considering all the above
factors, the tendon-driven mechanism fits the tasks mostly.

Table 1.2 summarized the typical tendon-driven snake-like surgical robots since 2011. The
mechanism designs can be classified into four groups, namely the one primary backbone,
four primary backbones, no primary backbone, and concentric tubes. For the one primary
backbone, the first subgroup used disks as tendon holders, which has been shown in
Figs. 1.1A and 1.2B. Following are examples: Bajo et al. [12] separately built the tendon-
driven continuum robot using concentric disks connected in series with one primary
backbone; Sen et al. [13] and Ouyang et al. [18] introduced the three-segment continuum
cable-driven robot for a larger workspace. The second subgroup made various evolutions to

(A) (B)

Figure 1.1
Typical mechanical structure of snake-like surgical robots. (A) Cable-driven mechanism with
primary backbone and two cables. (B) Front and side view of the cross inner and outer tube
snake surgical robot.