Page 240 - Flexible Robotics in Medicine

228 Chapter 9

Torque sensing can further be adapted by reading the armature current and converting it to
estimation for torque. However, this method is inaccurate due to disturbances or friction
that can further result in a change in the current.

9.4 Conclusions and future work

This chapter presented a new flexible robot system to assist for tracheostomy through
transoral access. The flexible robot consists of two bendable joints, hollow linkages, and a
flexible drill. The bendable joint is used to adjust the flexible robot to conform to the
tracheal channel, and a flexible shaft passing through the hollow linkage to connect to the
drill bit can drive the drill bit in arbitrary directions. The flexible robot was experimented
with gelatin to determine its stability. Considerations were especially taken when the motor
speed was MEDIUM or HIGH and the bending was at 160 degrees since the objective was
for the drill guide to work under such conditions.

The figures of deflections, Δx and Δy, from Table 9.1 and Fig. 9.8 suggest that the system
becomes increasingly unstable due to the increased speed and bending angle as the
system was under a no-load condition. Putting a load on the drill bit helps to stabilize the
system and support the drill as it drills through the elastic material as suggested by the
results of Fig. 9.9, with exit hole diameter, H x , generally being smaller than the entrance
hole diameter, H n . It thus can be concluded that the design for a support that is suggested
here can support a surgical drill.

The prototype built was on a larger scale due to printing limitations, thus future work
should involve using closer sizes and material in the construction of prototypes for testing.
It has not been tested against rigid materials with comparable properties to a bone, thus the
next possible step is to do so.

The design for the prototype can be further improved as the mechanical link structure has
areas that are sharp corners and may cause discomfort when inserted into the patient. By
using steel, it would be possible to reduce the size and thus design a circular encasement
for the links. This would be similar to the design for a surgical grasper, which is further
actuated via the tendon wire and links. Alternatively, a suitable plastic or rubber tube can
further be used to encase parts of the link, such that it does not interfere with the bending
while offering protection. Additional link unit may further be considered to be added to
allow easier entrance into a patient’s body.

Acknowledgment

This work was in part supported by the National Key Research and Development Program, The Ministry of
Science and Technology (MOST) of China (No. 2018YFB1307703).