Critical Coupling Magnetic Moment of a Petal-Shaped Capsule Robot

Actuated by spatial universal rotating magnetic vector through digital control, the steering navigation of the spiral-type capsule robot in the gastrointestinal (GI) tract becomes possible. However, as a potential risk, the fluid resistance torsion moment generated by the rotating spiral-type capsule robot would distort the GI tract with insufficient fluid. It is difficult to investigate the fluid distorting effect on the GI tract, because online measurement of the fluid resistance torsion moment still remains unsolved. In this paper, an innovative method employing critical coupling magnetic moment for indirectly detecting the fluid resistance torsion moment is proposed. To reduce fluid distorting effect, a petal-shaped capsule robot, whose surface is composed of four petal-shaped tiles, is proposed, and fluid resistance torsion moment-weaken effect of the petal-shaped capsule robot is discovered and investigated, which happens to the fluid when it travels through a convergent wedge-like gap between the surface of each of the four petal-shaped tiles and the inner pipe wall. Simulations and experiments have demonstrated that the twist impact on the GI tract by the petal-shaped capsule robot is reduced, while the non-contact driving performance in the GI tract is improved greatly isolated by fluid membrane with high dynamic pressure.