Based on the critical gap phenomenon of the intestinal capsule robot,a variable-diameter capsule robot with radial gap self-compensation is developed in this paper.With the functional variation principle,a fluid dynamic pressure model satisfying the boundary conditions of the outer surface of capsule robot with screw blades is derived.The critical gap phenomenon is studied theoretically and experimentally based on the end effect and the dynamic balance characteristics of the fluid on the surface of capsule robot.The concept of start-up rotation speed is defined,the relationship between the start-up rotation speed and the spiral parameters of capsule robot is investigated.The strategy for implementing drive and control on several capsule robots under the same rotational magnetic field is proposed,and by defining the start-up curves of several capsule robots with the similar motion regulation as the objective functions,genetic algorithm is employed to optimize the spiral parameters of several capsule robots.Experiments have shown that the proposed drive and control strategy for several capsule robots can be implemented effectively.It has a good prospect of application inside intestine to realize the drive and control on several capsule robots for different medical purposes.
ZHANG YongShunWANG DianLongRUAN XiaoYanJIANG ShenYuanLU Jie
A drive and control method is put forward for a variable diameter capsule micro robot to screw forward in intestine using magnetic coupling between an inner actuator inside the robot and the rotational magnetic field generated by a rotating outer actuator. The structures of the outer and inner actuators are magnet cylinders with multiple magnetic poles in tegular shape alternating with dissimilar radial magnetization. An universal mathematical model of magnetic torque at eccentric state is established based on the equivalent magnetic charge method, and the characteristics of magnetic torque with respect to structural parameters of actuators are theoretically studied. Experiments show that the driving method features advantages such as powerful magnetic torque, high safety, reliability, etc. The driving ability of the variable diameter capsule micro robot is greatly improved by its automatic radial clearance compensation. The magnetic drive system has a promising prospect of medical applications in intestine.
For realizing non-contact steering swimming of a capsule robot in curved environment filled with viscous liquid, based on spa- tial orthogonal superposition theorem of alternating magnetic vectors, an innovative physical method is proposed, which em- ploys three-axis orthogonal square Helmholtz coils fed with three phase sine currents to create a universal uniform magnetic spin vector as energy source. According to the antiphase sine current superposition theorem generalized in this paper, an effec- tive control method for successively adjusting the orientation and the rotating direction of the universal magnetic spin vector is proposed. For validating its feasibility and controllability, three-axis Helmholtz coils, power source and an innovative capsule robot prototype were manufactured, experiments were conducted in both spiral pipe and animal intestine. It was demonstrated that the orientation and the rotational direction of the universal uniform-magnetic spin vector can be adjusted successively through digital control and steering swimming of the capsule robot in spiral intestine can be achieved successfully. The breakthrough of the universal rotating uniform-magnetic vector will push forward the development of modern physics and biomedical engineering
ZHANG YongShunWANG NaDU ChunYuSUN YingWANG DianLong
