Research On Micro In-pipe Robot Driven By Moving Rotational Magnetic Field

Micro in-pipe robot is developed for pipeline detection and maintenance. Because of the limitation of space, the mechanical structure of robot must be simple and reliable and the robot should have high efficiency of driving energy conversion.the micro robot driven by magnetic field just develop to meet the needs mentioned above.The main moving motions of the micro robot driven by magnetic field are wandering, procession, and peristalsis.Because of the limitation in body shape and energy supply, the micro robot driven by magnetic field has some shortcomings such as no way to realize bidirectional move, the damage to the pipe wall made by the robot body, low velocity and so on .In this paper, a capsule micro in-pipe robot whose surface without screw line driven by outside magnetic field is developed. The robot realizes the revolving by means of the inner NdFeB revolving which is driven by outside magnetic field .On the basis of the theory that Helmholtz coils can generate uniform magnetic field and magnetic field vector addition, the driving coil group which is made by two axes perpendicular Helmholtz coil group and solenoid coil is designed. The coning rotational magnetic field is created by the way of loading alternating current with fixed amplitude and frequency to Helmholtz coils and direct current to solenoid coil. The robot is driven by the coning rotational magnetic field.The robot whose structure is simple is driven by wireless way and the velocity is quick. It can realize bidirectional movement and can avoid the body contacting with the pipe wall when it is moving , so it has no harm to the pipe wall.This paper analyzes the principles of robot body design and driving magnet formation, and the flux density calculate model is established to analyze the quality of magnetic field (flux density, uniformity and power loss) ,which provides the reference of coil optimum design. It also simulates the Helmholtz coil with ANSYS software and design the driving coil group according to the analyze result.At last, the motion performances are verified through a series of experiments. The experimental results show the micro robot features with good movement performance. Therefore a new control method without cable on micro in-pipe robot whose surface without screw line driven by coning rotational magnetic field is realized.