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Dynamic Characteristics Analysis of A Magnetically Driven Dual Hemisphere Capsule Robot by Eccentric Gravity Center

Capsule robots have broad application prospects for interventional diagnosis and treatment in the gastrointestinal tract. This paper proposes a dual hemisphere capsule robot driven by a pure magnetic moment. Its structure features that the upper and lower hemisphere, which can relatively rotate freely, constitutes a coaxial body, thus the dual hemisphere capsule robot can realize panoramic observation during the suspended posture adjustment in passive mode and rolling locomotion in active mode. The dynamic equation for attitude control is established based on the analysis of the magnetic moment, damping moment and gravity moment models of the dual hemisphere capsule robot, thus the influence on the dynamic characteristics by the center of gravity offset is studied particularly. The research results show that when the center of gravity of the dual hemisphere capsule robot moves along its axis, the orientation of the dual hemisphere capsule robot axis can still be controlled by changing the normal vector of the rotating magnetic field, and the dual hemisphere capsule robot axis will make regular precession in the stable state. This research has laid a solid foundation for the reliable application of the dual hemisphere capsule robot.