Research On Driving Method Of Micro Capsule Robot Based On Rotational Magnetic Field

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 of micro capsule robot with magnetic field. With the character of helmholtz coils in generating uniform magnetic field, two perpendicular helmholtz coils are used to generate uniform rotational magnetic field, the external magnetic field can drive a micro capsule robot to swim in small pipeline full of viscid liquid, the micro robot has a spiral structure on surface and a permanent magnetic inner driver of NdFeB embedded in it.In this paper, the driving and the swimming mechanism of the micro robot are introduced firstly. According to vector addition, two sets of perpendicular helmholtz coils drived by two current signals in quadrature can generate a rotational magnetic field in a fixed direction, which has improved the Controllability of wireless driving method with magnetic field by the way of adjusting the current. Then the magnetic intensity model of helmholtz coils is established to analyze how the magnetic intensity and power dissipation are affected by the size and configuration of coils, which provides the reference of coil optimum design.The principle and characteristics of Direct Digital frequency Synthesis (DDS) are introduced, a program of getting driving signals with MCU and DDS is proposed. Based on the AT89S52 and DDS chip AD9854, has expanded the design of the circuit to drive a rotational magnetic field in a fixed direction, and the system can produce two quadrature current signals to drive two sets of Helmholtz coils.At last, the method of generating rotational magnetic field in any directions with three axial perpendicular helmholtz coils is explored. It is found that when the current parameters of each coil satisfy certain conditions, the direction of rotational magnetic field can be adjusted according as required, and the relationship of currents in three helmholtz coils is deduced. A project with AD9959 at the core to drive three helmholtz coils and the method to control the output signals are mainly expended, which has laid the foundation of research on driving micro robot in complex and tortuous environment.