Orientation Control of an Electromagnetically Actuated Soft-Tethered Colonoscope Based on 2OR Pseudo-Rigid-Body Model

Colorectal cancer (CRC) incidence has been steadily rising worldwide. Robotic colonoscopes provide new approaches to conduct colon inspection and treatment. This paper presented a novel electromagnetically actuated softtethered colonoscope to achieve precise and stable orientation control. An inflated balloon was designed to eliminate the unpredictable disturbance of the floating tether. A 2OR Pseudo- Rigid-Body (PRB) model of the soft tether was constructed to analyze the relationship between the tether deflection and applied force and torque. A closed-loop control framework was detailed with visual position feedback. Experiments were first conducted to validate the assumption of the PRB model and the efficacy of the magnetic field model. Then, trajectory tracking tasks and disturbance rejection tests were performed to validate the feasibility of the closed-loop control and developed system. Results show that the designed colonoscope was able to stably and accurately orient to the desired orientation under disturbance. The distal tip could quickly re-stabilize to the desired orientation even a large disturbance exists.