Design, Modeling and Control of Tip Actuated Soft Continuum Manipulators for Applications in Endoscopy

Abstract

Affordable diagnostic endoscopy is a growing need worldwide. Gastric cancer (GC) is the third most deadly cancer; it accounts for over 10% of cancers and more than 70% of these cases are concentrated in low- and middle-income countries. Screening programs have been shown to be effective in reducing the mortality rate through early detection; however, many factors hinder the widespread implementation of these programs in low resource settings due to their high capital cost, limited portability of the equipment, and reprocessing/contamination concerns. Tip actuated soft continuum manipulators (SCM) represent a potential alternative to conventional flexible endoscopes that can meet the need for a cheap, disposable inspection device. A waterjet actuated SCM called the HydroJet was proposed to meet this need. The first part of this dissertation describes the design improvements of both the HydroJet endoscope and platform in order to achieve controllable tip deflection under waterjet actuation. The second and third part of this work address modeling and control strategies of tip actuated SCM with application in the HydroJet System. In particular, a method is presented to improve kinematic modeling for CM based on the online estimation of a disturbance parameter and is applied to two of the most common types of kinematic models for continuum manipulators, a Cosserat rod model and a Pseudo-Rigid-Body model. Thirdly, a closed-loop control scheme for SCM based on the Cosserat rod framework is presented using both actuator and pose feedback. It is validated and compared with the open-loop control case. The fourth part of this work presents the telerobotic operation of the HydroJet System and introduces a method for detecting contact with the environment. Both methods are crucial to enable the use of the system as an endoscopic device. A final validation of the system as a whole is presented within an anatomical stomach model. The final portion of this dissertation presents a novel tip actuated SCM for the management of pancreatic necrosis called the WAterjet Nectrosectomy Device (WAND). System design, characterization and experimental validation with an in-vivo study is presented to conclude this work.