Bifurcation analysis of a vibro-impacting capsule robot in contact with a circular fold

Abstract

The lining of the small intestine consists of a series of circular folds, which is the main source of intestinal resistance for capsule endoscopy. This paper presents an in-depth bifurcation analysis for a vibro-impacting self-propelled capsule robot encountering a circular fold. Using the GPU parallel computing and path-following techniques, one- and two-parameter bifurcation analyses are performed to reveal the capsule–fold dynamics of a newly proposed model. It is found that the excitation parameters of the capsule and the fold’s mechanical properties can significantly influence bifurcation scenarios. Then basin stability analysis is further conducted to uncover the capsule–fold dynamics from a probability perspective. Numerical results indicate that the period-one motion of the capsule–fold interaction and the crossing motion can dominate the global dynamics of the system in the small and large excitation amplitude regions, respectively. Once the mechanical properties of the circular fold are varied, a significant change in multistability is also observed and demonstrated via the basins of attraction. The results presented in this work are intended to provide a solid basis for the locomotion control of the capsule robot in the small intestine when encountering different types of circular folds.