Design Analysis and Tracking Control of Extensible Soft Robot for Colonoscopy

Colonoscopy is considered an effective standard method, not only for screening the lower Gastrointestinal (GI), but also for detecting bowel cancer, and removal of tumors. Nevertheless, conventional robotic endoscopes lack maneuvering, leading to discomfort and pain to patients, due to their rigidity and interaction forces with colon’s membrane. Soft colonoscope plays a great role in tackling those problems, owing to their unique maneuverability in tight and curvilinear paths, and safe interaction with constrained environments. However, designing a control approach for such robots is still challenging due to their compliance behavior. This paper presents a compact design of soft cable-actuated robot for colonoscopy. It consists of three subsections, each is 1.5 cm diameter. The middle part acts as a soft spring to provide extensibility during motion, which is embedded within two identical structure subsections. Furthermore, two fabrication technique are explored using traditional 3D printer and laser molding printer to evaluate the durability and response of the design. Finally, Nonlinear Model Predictive Control based on kinematic model is simulated in terms of point stabilization and trajectory tracking while respecting the constraints of real workspace, cable lengths and control actions. The results show that NMPC exhibits superior behavior against avoiding static and dynamic obstacles, while concerning constraints.