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

Abstract

The vibro-impact capsule system has been studied extensively in the past decade because of its research challenges as a piecewise-smooth dynamical system and broad applications in engineering and healthcare technologies. This paper reports our team’s first attempt to scale down the prototype of the vibro-impact capsule to millimetre size, which is 26 mm in length and 11 mm in diameter, aiming for small-bowel endoscopy. Firstly, an existing mathematical model of the prototype and its mathematical formulation as a piecewise-smooth dynamical system are reviewed in order to carry out numerical optimisation for the prototype by means of path-following techniques. Our numerical analysis shows that the prototype can achieve a high progression speed up to 14.4 mm/s while avoiding the collision between the inner mass and the capsule which could lead to less propulsive force on the capsule so causing less discomfort on the patient. Secondly, the experimental rig and procedure for testing the prototype are introduced, and some preliminary experimental results are presented. Finally, experimental results are compared with the numerical results to validate the optimisation as well as the feasibility of the vibro-impact technique for the potential of a controllable endoscopic procedure.

Design and experimental investigation of a vibro-impact self-propelled capsule robot with orientation control

“…To optimise the speed of the prototype, both the one-coil and four-coil driving methods were tested on the smooth surface under different combinations of frequencies and duty cycles. The range of the frequency was selected from [10,30] Hz since the capsule can move efficiently within this range according to the studies in [11], [12]. For each test, it was repeated fives times, and its averaged speed was plotted in Fig.…”

“…The photograph and internal views of the prototype are presented in Fig. 2, and its design parameters which were determined based on the previous work [12] and design requirements summarised above, are listed in Table I. The capsule body was fabricated using polylactic acid via 3D printing.…”

“…A proof-of-concept prototype of the "hammer" capsule in mesoscale was developed and demonstrated experimentally in [11]. A prototype of the "hammer" capsule with 26 mm in length and 11 mm in diameter, aiming for small-bowel endoscopy, was developed and validated in [12].…”

Evaluating the resistant force of an endoscopic capsule self-propelling in the small intestine

“…This force was calculated from a combination of the coil's supplying current and the distance between the coil and magnet. Such a force-distance relationship has been measured through experiment and validated by analytical calculation in [13].…”

“…Carta et al [12] employed an on-board vibratory motor with a wireless powering unit for active capsule endoscopy. Liu et al [13] developed a vibrational capsule with periodic impact motions that can achieve the progression speed up to 14.4 mm/s. More recently, Erin et al [14] proposed an MRI-powered untethered robot integrated with a camera and an on-board battery for wireless capsule endoscopy.…”