Research On System Of Magnetic Sphere Driven And Controlled By External Magnetic Field In Miniature Curved Tube

With the development of electrical and electronic technology and control technology,the control accuracy and anti-interference ability of magnetic levitation systems have been greatly improved.And experts and scholars at home and abroad have applied magnetic levitation technology in various fields,such as magnetic levitation bearings,magnetic levitation trains,magnetic levitation motors,magnetic levitation balance and so on.This article is supported by the National Natural Science Foundation of China.The magnetic levitation technology is used to realize the one-dimensional suspension motion control of the controlled levitated object on the axis of the electromagnetic actuator.In view of the shortcomings and deficiencies of the existing external magnetic field tube drive technology,magnetic sphere driven and controlled by external magnetic field in miniature curved tube is investigated in order to meet the requirements of the internal quality inspection of the miniature curved tube in industry and the diagnosis and treatment of diseases in the human body cavity channel in the medical field.Furthermore,a spherical permanent magnet with a diameter of 12.7 mm was used in the experimant under the control of the magnetic field of the electromagnetic actuator.The research contents and conclusions of this paper are as follows.According to the theory of material electric structure,the variation law of magnetic induction intensity on the magnetization center axis of spherical permanent magnet is analyzed.Besides,the electromagnetic force model of the magnetic levitation ball system consisting of air-core solenoid and spherical permanent magnet is established based on electrodynamics.Then,the electromagnetic force equation of the system is derived.ANSYS Maxwell finite element software is used to establish the physical model of the controlled levitated object and the electromagnetic actuator.Therefore,the accuracy and reliability of the theoretical calculation results were verified by finite element analysis.Theoretical analysis and ANSYS Maxwell finite element simulation results show that the electromagnetic force of the magnetic levitation ball system composed of a air-core solenoid and a spherical permanent magnet is proportional to the excitation current,and the electromagnetic force has a strong nonlinear relationship with the suspension gap.As the gap increases,the electromagnetic force decreases.In order to facilitate further research,the electromagnetic force equation is simplified by empirical expression.The test system made up of a hardware and software platform is built.Moreover,a novel magnetic levitation ball system based on double linear hall sensors structure is designed and implemented,which effectively increases the operating range of the system.Based on the simplified electromagnetic force equation,the mathematical model of magnetic sphere suspension system was built.Furthermore,a digital PID controller and single neuron adaptive PID controller were designed according to the characteristics of the system model.Then,the model of magnetic sphere suspension control system was built in MATLAB/Simulink environment,and reasonable controller parameters were determined by parameter setting and simulation.The dynamic and static characteristics of magnetic sphere one-dimensional suspension control system were studied.The experimental data show that the position accuracy of the magnetic levitation ball system based on the double linear hall sensors using PID controller reaches ±0.02 mm.And the step-by-step control method effectively realizes the one-dimensional motion control over a long distance of the controlled levitated object.Moreover,it helps to reduce the overshoot of the step response of controlled object.The experimental data show that the smaller the step length,the smaller the overshoot of the step response.In other words,the step-by-step control improves the stability of the controlled object.The interpolation algorithm was used to plan the suspension motion trajectory of the controlled magnetic sphere in the miniature curved tube.And the interpolation step was set as 0.2 mm.During the experiment,the driving motor speed of the linear sliding table was set as 0.2 r/s,that is,the horizontal motion speed of the electromagnetic actuator was 1.0 mm/s.Besides,the one-dimensional suspension motion step of the magnetic ball was 0.2 mm.The magnetic sphere was controlled to move along the interpolation planning motion path.The experimental results show that the controlled levitated object was driven and controlled by external magnetic field in miniature curved tube,and the magnetic sphere was able to move along the predetermined trajectory.