Research On Micro Displacement Positioning Platform Driven By Magnetically Levitated Planar Motors

In integrated circuit manufacturing, precision machining industry and precision measurement industry,the needs and requirements are increasing for the Multi-DOF precision positioning platform. Higher requirements are put forward for positioning accuracy, DOF dimension, resolution and acceleration performance of precision positioning platform. This paper presents an improved Y-shaped magnetic levitation precision positioning platform to solve the problem of flotation-type positioning platform can not work in the vacuum environment, while ensuring a high motion performance.First of all, an improved Y-shaped magnetic levitation micro-displacement precision positioning platform was proposed considering the existing magnetic levitation positioning platform at home and abroad. Replacing the single magnet with Halbach permanent magnet array and fixing the coils which provide the levitation force and the driving force on the same plane to increase the stroke of positioning platform while increasing the difficulty of control. At the same time, the simulation was done for the mover of positioning platform. The simulation result show that the natural frequency of the mover is 446.77 Hz and the central maximum deformation is 59 nm after loading.Secondly, an electromagnetic force analytical model was established for the electrical coil of drive unit of positioning platform. Through modelling the one-dimensional to three-dimensional energized coil, we obtain force analytical model of the energized coil in the field of Halbach permanent magnet array space. According to the results of analytical models, and the coil array used in this study is a two-dimensional array coil, we got the current allocation results of each energized coil. And then location decoupling was taken for the positioning platform. Finally we got the correspondence relationship between the coil current and DOF displacement.Then, the system motion control card was designed. The major resource of control card include the master unit composed by the DSP and FPGA, 3-channel analog input interface, 6-channel analog output interface and 3-channel scale signal input interface. Motion control systems and interactive PC program were compiled. Quantitative analysis was made for the system errors in the course of moving of positioning platform and compensatory measures were given.Finally, the experiment platform was constructed and the overall test was done to the prototype of improved Y-shaped magnetic levitation precision positioning platform. The result indicated that closed-loop positioning noise of the positioning platform is ±0.5μm. The resolution of translational displacement on z axis is superior to 2μm of the mover of the positioning platform. The resolution of angular displacement on y axis is superior to 5″ of the mover of the positioning platform and so is superior to 7″ on x axis. The maximum acceleration is up to 9.734m/s2 of the mover of the positioning platform without loading. The maximum acceleration is 6.502m/s2 of the positioning platform when the load of the mover is 2kg.