Closed-loop Electromagnetic Actuation System for Magnetic Capsule Robot In a Large Scale

Accurate positioning and efficient movement are essential for magnetic capsule endoscopy, which has attracted more and more attention in recent years. However, moving in the desired trajectory often conflicts with precise positioning, as magnetic localization is only feasible in a small area near the sensors. In this paper, we proposed a closed-loop magnetic capsule robot actuation system, which can accomplish localization and actuation simultaneously on a large scale in the fluid environment of the human body. To achieve large-scale detection, electromagnetic coil and sensor array are fixed together on a 3-axis screw mobile platform. The distribution of magnetic field is analyzed with magnetic dipole model and rectangular electromagnetic coil model. Levenberg-Marquardt algorithm has been employed to estimate the position of the capsule robot by subtracting the actuation magnetic field. PI closed-loop controller with localization of the robot as feedback is applied in the system. Although the response speed of the system with the PI controller is not fast, it could perform well in stability, which is expected when the capsule is moving inside the human body. Two specific path following experiments were carried out to verify the performance of simultaneous localization and movement on a large scale. Results showed that the proposed system and method could work well.