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Slender snake-like endoscopic robots in surgery 7

et al. [24] built a redundant four lead-module snake-like robot for abdominal radiosurgery.
Son et al. [25] developed a semiautomatic snake robot that has 11 motor-actuated modules
with rotating axis perpendicularly arrayed for transanal NOTES.

1.2.3 Novel design and platforms

Besides the conventional realization of snake-like robots such as tendon-driven and motor-
actuated module connection, researchers have further explored new mechanical designs and
actuation. As for the mechanism design, Conrad et al. [26] and Conrad and Zinn [27]
developed an interleaved continuum-rigid manipulator that combines the advantages of
precise actuation and safe contact. Lee et al. [28] used movable pulleys to drive
12 perpendicular joints of a snake-mechanism for NOTES. Dong et al. [29] proposed a twin
actuation mechanism with a compliant joint that can maintain the cable tension in any
configuration. Yoon et al. [30] developed a robotic system for maxillary sinus surgery using
a compliant spring backbone to enhance interaction safety.
In actuation, pneumatic driving, as well as new materials such as artificial muscles and
SMA, was used. Haraguchi et al. [31] developed a surgical manipulator driven by four
pneumatic cylinders to realize force sensing without sensor fixed on the tip of the tool.
Smoljkic et al. [32] proposed a hybrid rigid-continuum robotic system for MIS with the
continuum part comprising an outer backbone of Ni-Ti tube and four McKibben muscles
affording the bend motion. Lau et al. [33] built a robotic surgical system for endoscopic
submucosal dissection with the continuum part comprising of a sheath and four SMA wires.
Soft robotics plays an essential role in the realization of novel snake-like surgical robots.
Granular jamming and McKibben actuation were used by Jiang et al. [34] to build a soft
snake robot with variable stiffness and flexible motion capability. Kim et al. [35] proposed
a layer jamming tubular mechanism controlled by confining pressure for MIS. Abidi et al.
[36] used fluid chambers to provide robot modules with high dexterity and safe interactions
with human tissue. Wang et al. [37] built a soft surgical robot for cardiothoracic endoscopic
surgery with a silicone-made manipulator driven by cables.

1.3 Modeling of snake-like surgical robots

This section briefly introduces the kinematic and inverse kinematic modeling methods
based on the recent platforms that have been illustrated in the earlier sections. Moreover,
statics is summarized with emphasis on the relationship between actuation force and
deformation. Research on motion compensation, which is particularly essential for
describing and solving the common problems that exist in snake-like robots caused by
backlash, hysteresis, and friction force influences, will be concluded in 1.3.3.