Rotating Field Electrodynamic Levitation System Modeling And Control

Magnetic levitation could operate contactlessly, has the advantages of low noise, low maintenance and high reliability, it could be used in transportation, special motors, robot and metal working.A new configuration of maglev system--rotating field electrodynamic levitation system(RFELS) is proposed in this dissertation, the system uses electrodynamic levitation principle, rotating magnetic field (RMF) in its air-gap is generated by3-phase AC current in the primary windings, the interaction between RMF and secondary eddy current inducted by RMF produces lift force and horizontal force. This system's structural is stable, its control is simple, it can realize intrisic stable static levitation and guidance, has a widely application prospect. A series of analyzing tools was proposed to analyze the system's characteristics, structure design and levitation control system design method correctly.Firstly, providing evidences to system modeling and control, analyzed the electromagnetic relationship in RFELS using electromagnetic theory. RFELS's primary core is ring-shaped, sub-loop model was set to simplify the calculation and improve the calculation accuracy, analyzed each loop using average values of the loop.Unfold the ring-shaped sub-loop model into a rectangle sub-loop model to employ2-dimension electromagnetic analysis.Analyzed transverse end effect's influence to magnetic field distribution and energy storage based on2-dimension electromagnetic analysis, derived equivalent air-gap length expression and modified coefficients of main characteristics.Established RFELS's multi-layer model, solved electromagnetic distribution by Maxwell equations, simplified the expressions using surface impedance method, verified the results by time-stepping finite element calculation using Ansoft Maxwell.12, derived electromagnetic field energy storage expression by Poynting theorem. The results could be used in characteristic analysis and control parameters calculation.Secondly, the relationships between system parameters and key characteristics are investigated. According to the field distribution and energy storage, solved the lift force, torque, side force, recovery force and secondary force characteristics, relationships of the characteristics to current excitation and structure parameters. Set up test platform, performed force characteristics test an temperature rise test to testify the former characteristics. According to existing research results, investigated RFELS's main characteristics under various secondary structure, material, thickness, provided evidences to RFELS design.Proposed evaluation criterion for the system based on the fixed relationship between lift force and secondary loss, analyzed maximam lift force outputs under various working condition using the evaluation criterion.Analyzed the relationship between primary electromagnetic field travelling speed and lift force by electromagnetic field wave properties, generalize this conclusion to most electrodynamic levitation system by horizontal wave vector and palstance equivalent, explained how primary polar distance influent system'capacity of generating lift force.Thirdly, the control method of the system is investigated. Calculated RFELS equivalent circuit according to field energy storage, testified the equivalent circuit parameters by no-load test and short-circuit test. Regarded air-gap length as the key variable, derived air-gap state equations under2-phases synchronous rotating coordination system through synchronous rotating reference frame by the equivalent circuit parameters, and used in lift force decoupling control.According to the state equations, decoupled lift force and flux linkage based on secondary field orientation, took levitation height as key controlled object, added loss minimum optimization objective, designed secondary field orientation levitation height and flux linkage double closed-loop levitation vector control strategy, realized stable levitation control. Testified control strategy using Matlab/Simulink simulation software.Lastly, designed control system hardware based on DSP, performed operation test on levitation operation test platform, RFELS and its control system realized stable static levitation in the experiments.