Research On Magnetic Driving Characteristic Of A Capsule Micro Robot

Micro robot features small size, quick response, and low energy consumption. Wireless driving method is more potential for enhancing the reliability and feasibility of micro robot. Medical wireless micro robot can swim inside artificial tube cavity of human body for disease diagnosing, treating, surgical operation and etc.This paper proposes a wireless driving method to actuate the capsule micro robot swim inside human body using a NdFeB permanent magnet cylinder as the exterior driver magnetized in the radial direction, and the robot is driven by a external rotating magnetic field controlled by a motor with frequency conversion, a NdFeB inner actuator is embedded in the micro robot with spiral structure, the inner driver has the same magnetic pole structure as the exterior one.In this paper, the driving and the swimming principle of the micro robot are introduced firstly; the simulation analysis on the exterior driver's magnetic characteristics with the electromagnetic module of the finite element software ANSYS is conducted; the mathematics models of the magnetic driving torque and the axial magnetic force with equivalent magnetic charge method and magnetic Coulomb law under general eccentric status are established; and verification analysis on the exterior driver's structure parameters with MATLAB is made. And then, the paper makes a discussion on improvement scheme of magnetic pole's magnetization direction on the basis of the technology of permanent magnetic magic ring. In order to adapt the micro robot to various swimming environment and improve the driving efficiency of magnetic torque, this paper designs the micro robot prototype according to the centrifugal motion principle, which has the function of self-compensation for radial clearance.Experiments on magnetic force and swimming characteristics are studied at last. The result shows the model of the magnetic driving torque and the axial magnetic force established with equivalent magnetic charge method and magnetic Coulomb law has an effective function in describing the magnetic force characteristics. The magnetic testing result shows that the finite element method has high accuracy in magnetic field's simulation and analysis, and the obtained magnetic field distribution law plays a guiding role in optimization and improvement of magnetic pole structure. The swimming experiment shows the new micro robot prototype realizes effective radial clearance compensation at different rotating speed, and obviously improves the micro robot's driving ability under bigger clearance flexible elastic environment.