Supporting Characteristic Analysis And Control Of Zero Stiffness Maglev System

Ultra-precision motion stage for IC manufacturing is faced the challenge of broadband,and micro-amplitude/ultra micro-amplitude vibration control.The zero-stiffness magnetic levitation uses the force between the permanent magnets to form a six-degree-of-freedom low-rigidity and gravity compensation.With the active control of the electromagnetic force,it becomes a new form of vibration-isolating support suitable for ultra-precision fine stage.However,characteristic change law and regulation method of supporting still further studied.Based on the research of domestic and foreign technologies,this thesis analyzes the principle of zero stiffness,the magnetic field modeling and the influence of structural parameters,and a improved zero-stiffness maglev supporting scheme is proposed.The supporting control system is designed and developed.The experimental verification is carried out.The dynamic characteristics,joint simulation modeling and vibration suppression control technology of the magnetic levitation fine stages based on the supporting are further studied.The main work completed in this thesis is:Firstly,the structure of zero-stiffness maglev supporting is introduced,and the law of the linear variation of the magnetic field radial component of the mover along the axis in the working area is obtained.Based on Biot-Savar law,elliptic integral method and Lorentz force equation,the mathematical model of electromagnetic field and electromagnetic force is established,the influence of the thickness of the mover permanent magnet array rings and the size of the stator permanent magnet ring is analyzed.The design scheme of unequal thickness mover permanent magnet array rings and stator offset is obtained,the structural parameters are calculated and the experimental prototype is developed.The experimental platform test shows that the axial force emains unchanged and the axial stiffness is reduced by about 4 times,reaching 10N/m.The vibration isolation performance and working range are improved.Aiming at the single-degree-of-freedom control of the maglev supporting,the current,speed and position loop servo control models are established.The PID control parameters of each loop are calculated,and the effectiveness of the controller is analyzed by simulation.Based on the NI system and the prototype of maglev supporting,the servo control experiment platform is built,and the control block diagram based on LabVIEW is completed.The servo control effect is verified by single-degree-of-freedom servo control of the maglev supporting.The structure and working principle of the magnetic levitation fine stages with zerostiffness maglev supporting are introduced.Aiming at the problem of flexible vibration suppression of the magnetic levitation fine stages,the finite element model of the the magnetic levitation fine stages is established.The structural modal analysis is carried out and the dynamics model with flexible characteristics are obtained.A vibration suppression scheme based on input shaping feedforward combined with modal force constraint decoupling with four maglev supporting is proposed.A joint simulation model of dynamics and control is established.The simulation analysis shows that the flexible vibration of the first mode and the motion residual vibration of the magnetic levitation fine stages is suppressed.