| As a high-tech product of mechatronics,the main characteristic of the magnetic bearing is that there is no mechanical contact between the stator with the supported rotor,but the electromagnetic forces are produced by the permanent magnets or coil currents,the rotor can be suspended and work stably.Therefore,the magnetic bearing has the advantages which traditional mechanical bearings don't have,such as no friction and wear,long service life,no lubrication,low energy consumption and so on,and it has a wide application prospect in modern industry and machinery manufacturing industry.Aiming at the shortage of high energy consumption and complex control system for the four-pole and eight-pole magnetic bearings,the three-pole hybrid magnetic bearing(HMB)which is driven by an inverter is studied.Then,in order to reduce the couplings of magnetic bearings and improve the space utilization rate of the three-pole HMB,a five-degree-of-freedom(5-DOF)magnetic levitated electric spindle is used to be the research object to study the six-pole HMB in this dissertation.The two ends of the magnetic levitated electric spindle are supported by a 2-DOF six-pole radial HMB and a 3-DOF six-pole radial-axial HMB respectively.The mathematical model and parameter design of the magnetic bearings,the state equation of the magnetic levitated electric spindle and the compensation of the rotor unbalanced vibration are analyzed theoretically and experimentally.The main work and achievements of the dissertation are as follows:(1)The research background of the magnetic bearing is explained and the research status at home and abroad is expounded.The structure,working principle and application of the magnetic bearings are introduced,and the magnetic bearing is classified according to the characteristics.Finally,the research status of unbalanced vibration compensation method of the magnetic bearing rotor is briefly reviewed.(2)The overall structure of the 5-DOF magnetic levitated electric spindle is designed,and the working principle of the six-pole HMB at both ends are introduced,and their mathematical models are deduced.According to the design requirements,the structure parameters of the magnetic bearings are designed and the finite element analysis is carried out.Finally,according to the mathematical models of the magnetic bearings suspension force obtained previously,the state equation of the 5-DOF magnetic levitated electric spindle is deduced.(3)In order to solve the unbalanced vibration of the rotor caused by rotor mass eccentricity,a vibration compensation method based on the fuzzy LMS adaptive filter is proposed.The2-DOF six-pole radial HMB at one end of the magnetic levitated electric spindle is taken as the research object.Aiming at the problem that convergence speed and steady-state maladjustment cannot be taken into account in the traditional fixed step size Least-Mean-Square(LMS)algorithm at the same time,the fuzzy control theory is introduced.The LMS algorithm is improved by Takagi-Sugeno(T-S)fuzzy inference machine,and the simulation model is established in MATLAB/Simulink to verify the feasibility of the method.(4)The driving circuit,displacement conditioning circuit and DSP minimum system of the hardware part of the digital control system of the 5-DOF magnetic levitated electric spindle are designed,and the design of the software part including the main program and interrupt service subroutine is completed.Based on the hardware and software,an experimental platform of the5-DOF magnetic levitated electric spindle is built,and the rotor lifting and floating,the rotor stable suspension and anti-interference experiments are carried out.The experiment results show that the designed digital control system of the 5-DOF magnetic levitated electric spindle has good dynamic and static performance. |
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