Study On The Analysis And Control Technology Of Inductive Magnetic Levitation Spherical Motor

With the development of industrial technology,multi-degree of freedom system is widely used in industry and the way to build it up by the use of multiple single degree of freedom motor through a transmission device is the commonly used method in modern industrial,the method not only makes the accuracy and efficiency of the system has greatly reduced,but make the the volume of the system becomes large and bulky.These problems are solved because multi-degree of freedom motor is designed,the spherical rotor has the possibility to realize multi-degree of freedom movement because of its special shape,An induction type spherical motor is designed based on the development of the most mature induction motor theory.The spherical motor based on mechanical bearing will cause friction during rotation,thereby causing damage to the surface of the rotor and the loss of energy,magnetic levitation technology has no friction,no lubrication and sealing characteristics,self suspension can be achieved from the rotor when the magnetic levitation technology is applied to spherical motor,therefore,the rotor surface friction damage of the rotor surface between rotor and mechanical bearing can be avoided,and reduce the loss of energy.Firstly,this paper introduces the overall structure of inductive magnetic suspension spherical motor,and the structure and function of parts composed of the spherical motor are introduced.In order to verify the performance of the spherical motor and characteristic optimization of spherical motor,a spherical motor model is established by use of finite element analysis software,and analyzes the torque characteristics and loss characteristics and speed characteristic of the spherical rotor when copper plating thickness is 0.2mm,0.3mm and 0.4mm respectively and under the condition of no-load and 15 mN.m load,and it is verified that optimal thickness is determined when the copper plating thickness is0.2mm;the mathematical model of the magnetic levitation force is established,and linearization of the magnetic levitation force is did through the Taylor expansion,and combined with the voltage equation,three order relation between input voltage and rotor displacement is obtained,and parameters of double PD controller for magnetic levitation system based on the pole placement method is obtained,simulations result show that the controller can quickly make the system reach a steady state by the MATLAB/Simulink;And we design the electromagnetic coil of magnetic levitation system,and using Maxwell to verify the the electromagnetic coil can still achieve stable levitation in power constrained conditions,and also obtain the peak current of the magnetic levitation system,which provides a reference for the design of hardware circuit.According to the principle of asynchronous induction motor,The mathematical model of the spherical motor in the static coordinate is established,and the mathematical model is simplified by Clark transform and Park transform.The rotation of the spherical motor is controlled by the rotor field oriented vector control method.In this paper,induction magnetic suspension spherical motor platform for magnetic levitation control system and rotation control system is builed,the static calibration of eddy current displacement sensor used by the magnetic levitation system is carried out,and obtain the linear fitting of linear between displacement and output voltage;By acquiring the three axis eddy current displacement sensor output voltage curve when power on transient,it is verified that the spherical motor can realize stable suspension in motor space,and it is verified that the spherical rotor can be suspended in the central motor by comparing the static calibration of linear and spherical rotor displacement experiments,the error is only 1.8%;the current curve is acquired,and obtains the stable current and peak current in stable suspension stage,and it agree well with the simulation results.The three-phase current curve of the spherical motor is obtained in suspension state,the results show that the induction magnetic suspension spherical motor can work normally.