Research On Design And Control Method Of Magnetic Drive System Based On Halbach Array

The development of semiconductor industry demands better manufacturing environment.Magnetic levitation transmission technology is not dependent on mechanical contact,so it is the best solution to realize dust-free transmission in the workshop.The magnetic levitation transmission system is mainly include the levitation part and the driving part.In order to complete a stable and precise transport,the magnetic levitation transmission system requires that the driving part has the advantages of small disturbance,large thrust and low mass.Aiming at the above needs,a magnetic drive system based on Halbach array is designed,and the control method of the drive system is studied.Firstly,the existing direct drive system was analyzed.Because the permanent magnet magnetic drive system has the advantages of high thrust density and small thrust fluctuation and was a non-contact drive system,the drive system was designed based on this principle.The coreless structure for primarily was selected,and the Halbach array for secondary was selected to reduce the thrust fluctuation.Then the structure of the drive system was researched,the primary of system includes structural and winding circuit design,the secondary of the system includes magnetic circuit and structural design.And the signal feedback and ancillary parts of the drive system were chosen,and the overall structure of the magnetic drive system was preliminarily determined.Secondly,for the designed magnetic drive system,the no-load magnetic field was analyzed by using the surface current method and the equivalent magnetization current method.The analytical expression of no-load back electromotive force was established.In order to analyze the influence of Halbach magnet array on the electromagnetic performance of the drive system,the electromagnetic performance of common radial magnetizing secondary,Halbach three-section and Halbach five-section secondary structures were analyzed quantitatively by simulation software.The electromagnetic performance of no-load air-gap magnetic field,electromagnetic force,no-load back electromotive force and self-inductance were analyzed.The analysis shows that the three-section Halbach array can effectively improve the electromagnetic force of the drive system and reduce the thrust fluctuation,so this structure was chosen as the secondary structure of the drive system.Furthermore,the relationship between the important dimension parameters of the drive system and the electromagnetic force was analyzed,and the optimal structure parameters of the drive system were obtained.Thirdly,The mathematical models of the magnetic drive system in different coordinate systems and their mutual conversion methods were established.The drive system was controlled based on the space vector pulse width modulation(SVPWM).A linear PI controller was designed for the current and speed loops of the drive system,and a P controller was designed for the displacement loop.And a nonlinear sliding mode controller was designed for the speed loop.The speed and displacement response performance of the drive system was analyzed when the load and no-load using simulation software.Finally,the control results of speed were analyzed,which shows that the sliding mode closed-loop control is used to upgrade the speed response property.Finally,a prototype of the drive system was assembled.The electrical specifications of phase resistance and inductance were measured.Measurement experiments of no-load back electromotive force and thrust constant were implemented to verify the better performance of the prototype.Then the control experiment of the system was carried out,include the thrust fluctuation of the drive system,and the performance of velocity and displacement response were analyzed when the no-load and load.The experimental results show that the output thrust fluctuation of the prototype is small,which is about 2.6%.The prototype has a fast speed response,small overshoot and stable operation.The displacement response performance of the prototype is excellent,the phase difference between the prototype and the commanded displacement is small during the variable motion,and the positioning accuracy of the prototype is 1 μm.