Evaluation of Different Control Strategies for Trajectory Following of a Robotic Capsule Endoscope Under Rotating Magnetic Actuation

Current wireless capsule endoscopy (WCE) is limited in the long examination time and low flexibility since the capsule is passively moved by the natural peristalsis. Efforts have been made to facilitate active locomotion of WCE using magnetic actuation and localization technologies. In this work, we investigate the trajectory following problem of a robotic capsule under rotating magnetic actuation, in order to realize efficient and accurate navigation of the capsule in the narrow, complex intestinal environments. Specifically, four control strategies are developed based on the PD controller, adaptive controller (AC), model predictive controller (MPC) and robust multi-stage model predictive controller (RMMPC). In particular, the RMMPC method takes into account the uncertainty in the intestinal environment by modeling the intestinal peristalsis and friction in the controller design. We evaluate the proposed methods in simulation as well as in real-world experiments in several tubular environments, including plastic phantoms with complex shapes and an ex-vivo pig colon. The results have demonstrated the potential of the proposed control methods to realize accurate and efficient inspection of the intestine using active WCE. Our methods can be integrated with current WCE to improve the diagnostic accuracy and efficiency of the GI tract. Note to Practitioners-The motivation of this paper is to solve the trajectory following problem for active WCE in the human intestine to realize accurate, efficient and repeatable inspection of the gastrointestinal (GI) tract. We present four different control strategies for 5-DOF control of a robotic capsule endoscope actuated by a reciprocally rotating permanent magnet to make the capsule follow a predefined trajectory in a tubular environment. The accuracy and efficiency of the approach are validated in simulation and real-world experiments. The proposed trajectory following strategies can be integrated into existing WCE products to allow automatic and repeatable examination of the GI tract, and can also be extended to the locomotion of other tethered or untethered magnetic devices in the tubular environments for different medical and industrial applications. In the future, our proposed approach is expected to be combined with image-based automatic diagnosis of the GI tract to provide doctors with better tools for digestive examinations.