Design And Verification Of Hall Sensor Measurement System For Maglev Platform

With the rapid development of China’s integrated circuit manufacturing industry,the shortcomings in the field of IC production and package inspection are becoming more and more obvious.In order to make up for this deficiency and break through the foreign technical blockade,it is urgent to develop lithography machines with independent intellectual property rights.The working environment of Extreme Ultraviolet Lithography(EUVL)vacuum and the working requirements of long stroke in changing films make the magnetic levitation platform become one of the most critical core components of EUV lithography.Making use of the magnetic field distribution characteristics of the magnetic grid structure of the Halbach array in the drive structure,the spatial position parameters of the actuator can be analyzed only by arranging the Hall sensor array at a specific position below the stator coil,and there is no need to add additional measurement structure to the original drive struc ture,which is of great research value.For this reason,this paper studies a group of orthogonal Hall sensor combination arc tangent method and the mover position solution method based on this measurement method,and puts forward an error correction algor ithm model to eliminate the coil magnetic field interference and Halbach magnet array harmonic distortion,and establish a servo control system to achieve a better six-degree-of-freedom maglev control effect.First of all,space magnetic field of maglev platform is analyzed.Through two-dimensional and three-dimensional finite element simulation of the magnetic field distribution of the driving unit of the maglev platform,it is determined that the structure of the magnetic steel array is the Halbach array,and the amplitude and harmonic distortion of the magnetic field under different heights of the Halbach array are analyzed,and the installation height of the Hall sensor and the working height of the air gap of the actuator are determined to be 16mm～19mm.It is concluded that the high-order harmonics of the magnetic field of the Halbach array are the fifth harmonics.The influence of the electromagnetic distribution of the coil on the tangent displacement of the Hall sensor is also analyzed,and the necessity of filtering the magnetic field interference of the coil is determined.According to the spatial magnetic field distribution under 17 mm height,the influence of non-sensing direction motion and attitude rotation angle of magnetic steel array on the displacement of Hall arc tangent sensing direction is analyzed,and the calculation method of mover position based on Hall sensor is deduced.Secondly,the experimental platform of Hall sensor measurement system is built,and an acquisition board is made,whi ch can collect four Hall sensors and grating differential signals at the same time.The linear motor is used as the actuator and the grating data is used as the standard quantity to verify the effectiveness of the error correction algorithm.The error is 0.4mm after filtering the coil electromagnetic interference and 4 μm after compensating the harmonic distortion of the Halbach array.In addition,the repeatability of the position measurement error of the actuator caused by the harmonic distortion of the Halbach array is tested,the max value is about 7μm.A single-degree-of-freedom Hall sensor servo system is built.taking the data of the laser sensor as feedback,the stroke of the servo system is 30 mm,and the following error is less than 4μm.and the resolution of displacement measurement by single-degree-of-freedom Hall sensor is 1μm.Then,the holl measurement system verification platform is built,the electromagnetic force of the driving unit and the coil current distribution mode are modeled,and the position of the moving platform is decoupled according to the output and installation position of the eddy current sensor,and then the stroke and resolution of the verification platform are tested.The translational stroke is3mm×3mm×3mm,the attitude angle stroke is 1.0°×0.6°×0.5°,and the translational resolution is 1μm.The resolution of attitude angle is 3′′,which establishes the measurement benchmark for the construction of Hall servo system.In addition,the performance of the driver is optimized so that the temperature drift of the driver itself is reduced from 32 m V to 6m V,thus the positioning noise of the verification platform is reduced from 1.5μm to 0.4μm.Finally,the Hall sensor position measurement system is tested,and the Hall sensor installation circuit board and coil cage are made,and the position of t he maglev platform is decoupled according to the installation position and output value of the Hall sensor.with the help of eddy current verification platform,the deviation of eddy current sensor position decoupling and Hall sensor position decoupling under all levels of error correction is tested.the displacement resolution of multi-degree-of-freedom Hall sensor is 5μm.The resolution of attitude angle is 10′′.On this basis,the feedback input of PID controller is switched to Hall sensor,and the stroke of Hall servo system is tested to be3mm×3mm×0.5°.