Page 232 - Flexible Robotics in Medicine

220 Chapter 9

9.2 Mechanical design of the flexible robot

In order to accomplish tracheostomy through transoral practice, the following restrictions
and limitations are taken into consideration in the design of the proposed robotic system.
• Drill shaft must be flexible to bend around corners while stiff enough to transmit power
with little or no plastic deformation to maximize power transmission.
• Drill bit and shaft, and its support, is small enough to enter the trachea and bend to
contact the wall of the trachea.
• Shaft support is stiff enough to minimize vibration.
• The system should be cheap and easily mass manufactured or can be sterilized
for reuse.

Corresponding to the irregular path through transoral access, a tendon-driven linkage-based
flexible robot was designed. As shown in Fig. 9.2, the flexible robot consists of hollow
linkages, bendable joints, and drill. The bendable joint is used to adjust the hollow linkages
to conform to the tracheal channel, while the flexible shaft passes through the hollow
linkage to drive the drill to make a hole. In order to successfully drill through the tracheal
wall, the drill bit should be vertical to the tracheal wall during drill practice, therefore the
bending angle of the bendable joint must be at least 90 degrees for dexterous manipulation.
In this study, the bending angle of the joint depends on the length of the linkage. Three sets

Figure 9.2
Mechanical components of the flexible robot.

Table 9.1: Parameter value of the bendable joint.
No. S1 (mm) S2 (mm)
1 8 12
2 8 17
3 8 22