Page 229 - Flexible Robotics in Medicine

CHAPTER 9

Tendon-driven linkage for steerable guide

of flexible bending manipulation

Quanquan Liu, Ng Chiu Ping and Hongliang Ren
Department of Biomedical Engineering, National University of Singapore, Singapore

The objective of this chapter is to devise a steerable and bendable surgical drill-guide
system. Existing designs are drilling through bones from the external of the body and thus
requires limited dexterity in the sense of having straight, or a small maximum angle of
curvature or a large minimum radius of curvature, more than 10 mm. By exploring designs
of steerable surgical drill guides, it is possible to open up new surgical methods or
improvement in safety and efficiency to existing ones, such as tracheotomy.

In addition to the angle and radius of curvature, the stability of the drill guides is important
since excessive vibration could result in inaccurate drilling and impedes collection of force
data. The angle and radius of curvature could be determined through the design of the
support linkage. The instability and vibration during the drilling, however, are challenging
to be accurately modeled.
Deflection of the drill without load was measured at the tip of the drill in the x- and y-axes,
with the z-axis collinear to the drill shaft. Then, the drill was allowed to drill through a
piece of gelatin approximately 30 mm thick, and the diameter of the exit hole was
measured.

Through the experiments carried out at different speeds of drilling, it was found that the
deflection in x-axis varied between 1 and 4.2 mm, and the deflection in y-axis varied
between 1 and 2 mm given that the tendon wires are held. The exit hole generally
fluctuated between 2 and 4 mm.

While the experimental data prove that the proof-of-concept design is generally
stable during drilling, they only provide an estimation since the prototype was three-
dimensionally (3D) printed, different from the actual material of stainless steel intended for
surgical instruments. Therefore, for more accurate data, a prototype of the actual size and
material needs to be used in the future experiment.

Flexible Robotics in Medicine.
DOI: https://doi.org/10.1016/B978-0-12-817595-8.00009-2 217
© 2020 Elsevier Inc. All rights reserved.