| High-precision positioning stage is the key component in precision manufacturing field.This thesis studies the conceptual design and levitation control of a high-precision magnetically levitated stage with large planar motion capability.The translational motions are produced by the three planar levitation motors while the vertical motions are provided by three suspension magnets.The thesis mainly researches on five aspects,shown as follows:Firstly,the conceptual design of compact high-precision multidimensional positioner is presented.According to the feasible schemes,the three groups of suspension magnets are introduced to produce suspension force which can realize multidimensional motions.The three Halbach planar levitation motors based on the Lorentz-force law are used to produce drive force.And at last positioning precision and working principles of positioning stage are analyzed.Secondly,the 3-DOF rigid body dynamic model for the magnetic suspension is established by the way of Cardau Angle.And then decoupling control for system in the vertical direction is designed to manipulate the platen rotate along the x and y axis or levitate in the z direction independently.The process of controller design applied sliding mode control algorithm and ESO to eliminate the influence of parameter uncertainty and external disturbance is proposed.Thirdly,due to the importance of suspension stability in the z direction,the precision control for suspension control is introduced.The model of single point of suspension is established and the relevant features of system are analyzed.For precision control,the sliding mode control based on tracking differentiator is presented.Considering tracking differentiator plays a key role in filtering and choosing of control rate,the approximated linear discrete tracking differentiator based on Han is proposed.And simulation results show the usefulness of the control method.Fourthly,the realization and experiment of suspension controller for magnetic levitation stage is performered.The controller for 3-point suspension system and software algorithms for suspension control is designed.The experiment results show the usefulness and robust anti-disturbance ability of sliding mode control based on tracking differentiator. |
