This paper proposes an intestine capsule robot with variable diameter. It is driven by external rotating magnetic field and has the function of automatic radial clearance compensation. An external magnetic field generating device and a capsule robot with variable diameter are developed. Radial dynamic balance equation and kinematics equation of the capsule robot traveling inside flexible elasto-wall environment are established, and dynamic characteristics of the capsule robot inside flexible elasto-wall pipe and rigid wall pipe environments are analyzed and compared. Simulations and experiment results show that its dynamic characteristics in both pipes are almost the same. Under the action of radial clearance compensation, fluid dynamic pressure around outer surface of the capsule robot and its propulsion, as well as its adaptability to diameter change range, are significantly improved. Its propulsion and moving speed are controlled by adjusting rotating angular speed of the rotating magnetic field. This innovative capsule robot with radial clearance compensation has a promising prospect for inside intricate gastrointestinal (GI) tract in non-invasive therapy applications.capsule robot with a variable diameter, clearance compensation, flexible elasto-wall Citation:Zhang Y S, Jiang S Y, Zhang X W, et al. Dynamic characteristics of an intestine capsule robot with variable diameter.
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.variable-diameter capsule robot, radial gap compensation, critical gap phenomenon, start-up rotation speed, multiple capsule robot control Citation:Zhang Y S, Wang D L, Ruan X Y, et al. Control strategy for multiple capsule robots in intestine.
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.variable diameter capsule robot, Radial offset distance; Magnetic torque, Equivalent magnetic charge method
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