| A magnetic levitated electric spindle is a kind of high performance and speed motorized spindle supported by magnetic bearings.The magnetic bearing is based on controllable electromagnetic force to achieve stable suspension of the rotor,so that there is no friction contact between the rotor and the stator.Therefore,the magnetic levitated electric spindle overcomes the problems of friction heating and running noise of traditional motorized spindle supported by rolling bearings,which not only reduces the running power consumption,but also improves the machining efficiency and industrial application prospect.Six-pole magnetic bearing driven by inverter has been developed in the field of magnetic bearing,which overcomes the problems of large volume and high cost of traditional DC magnetic bearing and coupling of AC three-pole magnetic bearing,and further improves the bearing capacity.In this dissertation,the mathematical modeling of the suspension force and structural parameter design of the six-pole active magnetic bearing(AMB)supporting system for the mgnetic levitated electric spindle are studied.A soft-sensing method of the rotor radial displacement is proposed,and the simulation analysis and experimental research are carried out.The main contents and achievements of this dissertation are as follows:(1)Around the development process and research status of the mgnetic levitated electric spindle,the development of the mgnetic levitated electric spindle in time order and in blocks of domestic and foreign are summarized.Next,the magnetic bearing for support is taken as the object,whose basic composition and principle,characteristics and application as well as classification are summarized comprehensively.Finally,the research and development status of magnetic bearing displacement self detection technology is summarized,and the advantages and disadvantages of the current mainstream research methods are compared and summarized.(2)An overall structure of 5-DOF magnetic levitated electric spindle is designed.Next,the six-pole radial AMB and axial AMB in the supporting system are studied and analyzed respectively,and the mathematical model of suspension force is established.Then,the structural parameters are designed according to the bearing capacity requirements of magnetic bearings,and the relevant electromagnetic characteristics simulation analysis are carried out.(3)The knowledge background of continuous hidden Markov model(CHMM)is introduced and applied to the soft-sensing model of rotor displacement for magnetic bearing.Considering the problems of local extremum and slow convergence speed in traditional CHMM parameter training,genetic algorithm(GA)is used to optimize the traditional CHMM to improved CHMM(ICHMM)which can train the global optimal model parameters,thus the soft-sensing model for rotor displacements of six-pole radial AMB is established.Furthermore,the model evaluation and the simulation analysis of real-time prediction effect of the proposed soft-sensing model are carried out,and the superiority and reliability of the proposed ICHMM are verified by comparing with the traditional CHMM.(4)The control block diagram of the digital control system of 5-DOF magnetic levitated electric spindle is drawn.Next,the hardware modules are designed from the minimum system circuit,displacement interface circuit and power drive circuit of DSP.Then,the corresponding software design of the digital system including the main program and interrupt subroutine is completed.Finally,the experimental platform is built and the soft-sensing experiment of rotor displacement for six-pole radial AMB is carried out.Through the analysis,the performance of the digital control system and the practical feasibility of the soft-sensing method proposed in this dissertation are verified. |
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