Control of Magnetic Continuum Robots for Endoscopy

The present thesis discusses the problem of magnetic actuation and control applied to
millimetre-scale robots for endoluminal procedures. Magnetic actuation, given its remote
manipulation capabilities, has the potential to overcome several limitations of current endoluminal
procedures, such as the relatively large size, high sti�ness and limited dexterity
of existing tools. The application of functional forces remotely facilitates the development
of softer and more dexterous endoscopes, which can navigate with reduced discomfort for
the patient. However, the solutions presented in literature are not always able to guarantee
smooth navigation in complex and convoluted anatomical structures. This thesis
aims at improving the navigational capabilities of magnetic endoluminal robots, towards
achieving full autonomy. This is realized by introducing novel design, sensing and control
approaches for magnetically actuated soft endoscopes and catheters.

First, the application of accurate closed-loop control to a 1 Internal Permanent Magnet
(IPM) endoscope was analysed. The proposed approach can guarantee better navigation
capabilities, thanks to the manipulation of every mechanical Degree of Freedom (DOF)
- 5 DOFs. Speci�cally, it was demonstrated that gravity can be balanced with su�cient
accuracy to guarantee tip levitation. In this way contact is minimized and obstacle
avoidance improved. Consequently, the overall navigation capabilities of the endoscope
were enhanced for given application.

To improve exploration of convoluted anatomical pathways, the design of magnetic endoscopes
with multiple magnetic elements along their length was introduced. This approach
to endoluminal device design can ideally allow manipulation along the full length; facilitating
full shape manipulation, as compared to tip-only control. To facilitate the control
of multiple magneto-mechanical DOFs along the catheters' length, a magnetic actuation
method was developed based on the collaborative robotic manipulation of 2 External
Permanent Magnets (EPMs). This method, compared to the state-of-the-art, facilitates
large workspace and applied �eld, while guaranteeing dexterous actuation. Using this approach,
it was demonstrated that it is possible to actuate up to 8 independent magnetic
DOFs.

In the present thesis, two di�erent applications are discussed and evaluated, namely:
colonoscopy and navigational bronchoscopy. In the former, a single-IPM endoscopic approach
is utilized. In this case, the anatomy is large enough to permit equipping the endoscope
with a camera; allowing navigation by direct vision. Navigational bronchoscopy,
on-the-other-hand, is performed in very narrow peripheral lumina, and navigation is informed
via pre-operative imaging. The presented work demonstrates how the design of
the magnetic catheters, informed by a pre-operative Computed Tomography (CT) scan,
can mitigate the need for intra-operative imaging and, consequently, reduce radiation
exposure for patients and healthcare workers. Speci�cally, an optimization routine to
design the catheters is presented, with the aim of achieving follow-the-leader navigation
without supervision.
In both scenarios, analysis of how magnetic endoluminal devices can improve the current
practice and revolutionize the future of medical diagnostics and treatment is presented
and discussed.