Continuum Robotics in Endoscope Design

I developed an endoscopic design based upon Intuitive Surgical's Single Port robot that decouples the camera’s field of view from the working tool’s motion by employing Concentric Push-Pull Robots (CPPRs) in a dual-module configuration. The design utilizes two separate but complementary CPPR architectures: one dedicated to the camera module, termed the S-shaped CPPR (SCPPR), and another for the working tool, referred to as the Notched CPPR (NCPPR). The SCPPR is engineered with non-uniform notches, where increased cut depths on distal sections produce an S-shaped curvature. This curvature effectively offsets the camera from the tool, thereby preventing occlusion of the field of view during procedures—a significant limitation in traditional endoscopic systems.

Equations governing the bending mechanics illustrate how the displacement of the inner tube, in combination with the notch geometry, leads to a specific curvature. Notably, the SCPPR achieves an in-plane bending range from –27° to 89.4° relative to its unactuated axis. This range of motion is sufficient to reposition the camera independently, ensuring that the tool does not obstruct the view even in complex anatomical pathways.

In parallel, the NCPPR module replicates the functionality of conventional notched-tube wrists but is adapted to work in tandem with the SCPPR. It is actuated by both rotation and translation using an assembly comprising NEMA 8 stepper motors, gears, and Actuonix L-12 linear actuators. These components facilitate the spatial positioning of the working tool while maintaining a decoupled motion from the camera.

Experimental validation shows that while the SCPPR successfully provides an unobstructed view of the working field, the design is sensitive to manufacturing and material limitations. The prototypes were 3D-printed using Bambu Labs’ PLA-CF filament. The material’s anisotropic properties and the trade-offs between notch depth and tube buckling were carefully analyzed. Adjustments in notch design, such as reducing the notch height for the lower section to allow for more aggressive cuts on the upper side, enabled the desired S-shaped profile without compromising structural integrity.

I outlined future work involving the integration of a PC-Arduino interface for precise motor control and the use of super-elastic Nitinol components to enable further miniaturization. This decoupled design has the potential to significantly improve endoscopic instrument operability in minimally invasive surgeries.