Design And Optimization Of Electromagnetic Structure Of Magnetically Levitated Planar Motor With Moving Coils

Magnetically levitated planar actuators, which are planar motion structures, are composed of a stator and a translator. The translator of these planar actuators is suspended above the stator with no support other than magnetic fields, and can realize large range planar motion. Because of the active magnetic bearing the translator can move in six degrees-of-freedom. Compared with the traditional xy-drives with stacked linear motors, this type of planar motors with simple structure, high speed and high precision can be used in ultra violet and extreme ultra violet semiconductor lithography systems as one lynchpin of them.Electromagnetic structure is the basis of magnetically levitated planar actuators. Therefore, designing an electromagnetic structure with higher efficiency, lower harmonic interference, and better manufacturability is one lynchpin of improving the performance of a magnetically levitated planar motor.This thesis researches on a novel magnetically levitated planar actuator with moving coils. A new2-D Halbach permanent magnet array with higher flux density and lower harmonic components is presented. The flux density distribution of the new array is modeled and analyzed, and the simple analytical model of which for real-time control is built. A more accurate real-time control model for planar motors is solved. The synthesis design method for this motor is established, and the characters of the electromagnetic structure of the motor are analyzed and estimated by simulation. The main research contents and achievements are as follows,Firstly, by improving the current Halbach permanent magnet arrays, a new2-D Halbach magnet array with trapezoidal magnets is invented and adopted in the design of the planar motor. The trapezoidal magnets, which have a45°magnetization direction, can reduce the high-order harmonics and increase the intensity of the magnetic field in the air-gap.Secondly, the harmonic model of the flux density distribution of the new array is solved by using the Fourier Series Method and the scalar magnetic potential equation.Thirdly, a more accurate real-time control model of the magnetically levitated ironless planar motor is solved by deriving the numerical model of the corner segments of the coil with the theory of the composite numerical integral rule and the Newton-Leibniz formula.Fourthly, a special optimization method for the electromagnetic structure of this new planar motor is built. The new array has higher magnetic field intensity with low high-order harmonics in the air-gap by minimizing the high-order harmonics in z-component of the flux density distribution between those two models. The coil requires the highest force produced by per unit mass with the sequential quadratic programming optimization method.Then, the design method of the new planar motor is built by synthesis considering the controllability of the motor, end effects of the magnet array, and coil arrangement. Subsequently, four planar actuator configurations are designed and compared. The design proposal with the lowest power dissipation is selected.Finally, the characters of the electromagnetic structure of the motor such as the work point of the magnet array, the eddy-current damping, the copper loss, and the electromotive force are analyzed and estimated by simulation. By analyzing the work point of the magnet array, the material of the array is selected. By analyzing the eddy-current damping, the method of reducing the damping force is built. By analyzing the thermal distribution of the coil array under different conditions, the design foundation of the cooling system for the motor is established. By analyzing the self-inductance, the mutual inductance, and reverse electromotive force, the calculation method of the port voltage of the coil is derived. And by estimating the flux intensity of the magnet array, the thrust force and the force ripples of the motor, the characters of the electromagnetic structure of the motor is obtained.In this thesis, the correctness of the harmonic model and the analytical model of the magnetic flux density of the motor is verified by using the finite-element method, and the accuracy the new real-time control model is checked by the full harmonic model of the planar motor used by Jansen. Based on the electromagnetic structure, the model, the design and the optimization method of the new motor, this thesis presents a fundamental theory of designing and optimizing the electromagnetic structure of the novel magnetically levitated planar actuator.