Modelling of capsule–intestine contact for a self-propelled capsule robot via experimental and numerical investigation

Abstract

This paper studies the modelling of capsule-intestine contact through experimental and numerical investigation for designing a self-propelled capsule robot moving inside the small intestine for endoscopic diagnosis. Due to the natural peristalsis of the intestinal tract, capsule-intestine contact is multimodal causing intermittent high transit speed for the capsule, which leads to incomplete visualisation of the intestinal surface. Three typical conditions, partial and full contacts, between the small intestine and the capsule, are considered in this work. Extensive experimental testing and finite element analysis are conducted to compare the contact pressure on the capsule. Our analytical, experimental and numerical results show a good agreement. The investigation using a synthetic small intestine shows that the contact pressure could vary from 0.5 to 16 kPa according to different contact conditions, i.e. expanding or contracting due to the peristalsis of the small intestine. Therefore, a proper control method or a robust stabilising mechanism, which can

Experimental and numerical studies of intestinal frictions for propulsive force optimisation of a vibro-impact capsule system

“…6 was built by using ANSYS WORKBENCH for which material parameter configuration, geometry, contact settings, meshing, constraints, and loads were considered. In the model, the supporting plate, the capsule, and the small intestine were set as the structural steel, the polyethylene, and the viscoelastic material measured in our previous experiments [34], respectively. The dimensions of the capsule and the intestine were set the same as our experiments, and the contact between the intestine and its supporting base was bonded.…”

“…4d, as the capsule's external radius R c is larger than the inner diameter of the synthetic small intestine R i , the capsule is surrounded by the intestine, and viscoelastic deformation of the intestinal wall induces hoop pressure on the capsule. It should be noted that the hoop pressure of the intestine has been studied in authors' previous paper [34], and the following derivation of the total friction force has referred from the previous work. Under this condition, the friction force acting on the capsule can be written as…”

“…In the present work, the Maxwell model [34] was used to describe the viscoelastic property of the synthetic small intestine as illustrated in Fig. 7c for which E 1 , E 2 , and η 1 represent the Young's moduli of the springs and the damping coefficient, respectively.…”

“…For the semi-sphere tail section (x c +L < x ≤ 2x c + L), hoop-induced friction is similar to the counterpart of the head section, including (i) the hoop resistance on c Three-element Maxwell model to depict the stress-strain relationship of the small intestine with two springs and one damper. These diagrams were adopted from [34] the tail f tr and (ii) the hoop stress-induced Coulomb friction on the tail f t f , which can be written as…”

The vibro-impact capsule system in millimetre scale: numerical optimisation and experimental verification

“…The merit of such a capsule is its simplicity in mechanical design and control which does not require any external driving accessories, while allowing independent movements in a complex environment. The study of this method was initiated from mathematical modelling [7,8,26,27], early proof-of-concept investigation [28], multistable dynamics control [15,29], to our recent capsule-intestine contact modelling [30], intestinal friction study [31] and mesoscale demonstration [32,33]. Since the mathematical model of the system belongs to the class of piecewise-smooth dynamical systems, for this type of systems, the state space can be divided into disjoint subregions [34].…”