Basic Research On Synchronous Permanent Magnet Planar Motor With Concentric Winding

Synchronous permanent magnet planar motor(SPMPM) which can achieve planar motion by using electromagnetic energy directly, has many advantages such as high thrust density, low loss, high precision, simple structure, and has a broad application prospect in the modern precision and ultra precision machining equipment such as lithography, semiconductor processing and so on. Take the platform system of the lithography as the application background, a synchronous permanent magnet planar motor with concentric winding is proposed in this paper and the magnetic field of the Halbach permanent magnet array, the mathematical model, the design method and the cooling structure of the motor have been studied.Firstly, a synchronous permanent magnet planar motor with concentric winding is proposed to meet the requirements of the lithography for motors, and its topology structure and working principle are introduced, the advantages of the concentric winding is expounded. The analytical model of the Halbach permanent magnet array is established. According to the Fourier series method, the magnetic field of the Halbach array is analysed by using scalar magnetic potential, expressions of the air-gap flux density in the x, y, z directions are obtained according to the boundary conditions, and lay a theoretical foundation for further establish a mathematical model. The correctness of the analytic computation are verified by the comparative analysis of air-gap flux density distribution curve that obtained by analysis, simulation and experiment.Secondly, in order to facilitate the motor’s design, optimization and control, the mathematical model of synchronous permanent magnet planar motor with concentric winding is established. According to the structure of concentric winding, the equivalent short distance factor is analysed. On the basis of simplification of the magnetic field of the Halbach permanent magnet array and the concentric winding, the electromagnetic force, torque and related parameters of the motor are calculated by using the Lorentz force method, the mathematical model of the motor is established, which provides a theoretical basis to the control model of the SPMPM. The veracity of the analytical results is verified by simulation and experimental measurement of the static electromagnetic force, the back-EMF waveform and electromagnetic parameters such as resistance, inductance of the prototype.Thirdly, on the basis of mathematical models, the design method of the SPMPM that take lithography platform system as the application background is studied based on multi-field coupling. The design principles and indicators of SPMPM are analysed in the background of lithography system, and a design flow of the SPMPM based on field coupling is proposed in this paper. The main dimensions and calculation formula of the SPMPM with concentric winding are identified and derived. The influence of structure parameters of primary and secondary on the performance of the motor is analysed respectively, and get the motor performance curve along with the change of the structure parameters, which provides an important basis for the electromagnetic scheme optimization selection.Lastly, for lithography strict constraint on the motor’s heat, the temperature field and the cooling structure of the synchronous permanent magnet planar motor with concentric winding is studied. The loss and temperature rise characteristic of the SPMPM with concentric winding were analysed. A three-dimensional finite element thermal model of the motor is established, temperature field of the SPMPM with concentric winding is calculated, and the necessity is pointed out for cooling structure to ensure the normal operation of motor performance. An improved series cooling structure was proposed, through the finite element simulation analysis, proved that the structure has advantages in improving the motor surface temperature distribution uniformity. The finite element calculation results on temperature field and cooling structure of the motor are verified by the prototype temperature rise and cooling experiment study.