| According to the urgent demand of the precision positioning equipment in the field of domestic micro-electronic manufacturing, a multi-DOF magnetic levitation precision positioning platform is developed in this paper. On the basis of the structure design, the study of the system modeling and control strategies is developed emphatically.In this paper, a new precision magnetic levitation positioning platform based on TU structure is put forward. Aim at the platform, the analysis and design on the mechanical structure and magnetic circuit are also given. Furthermore, Maxwell3D is used in finite element analysis of magnetic field and levitation force. In the modal analysis, Patran/Nastran is intruduced. This proposed platform can be divided into levitation system and horizontal displacement system.The dynamic model of levitation system is established in this paper. In view of the levitation system with multi-variable, nonlinear, strong coupling characteristics, the article puts forward an improved auto-disturbances-rejection control(ADRC) strategy to realize decoupling and disturbance rejection.Through this control strategy, the internal and external disturbance of the system can be observed and compensated. Then, the decoupling control can be realized. In addition, this improved ADRC overcome the non-smooth character of nonlinear function in nonlinear state error feedback(NLSEF) of conventional ADRC and improve the system control quality. Comparative analysis of the simulation and test results show that when the proposed improved auto-disturbances-rejection control strategy is applied to levitation system control, the system has smooth system response, small disturbance fluctuation range, short recovery time while disturbance is in use, and the influence caused by the mover’s horizontal position changes on the levitation system has been effectively restrained.The dynamic model of horizontal displacement system is established. Then, the study based on state feedback decoupling control is carried on. The study indicates that state feedback decoupling control performance is greatly influenced by the position change of the mover. Therefore, another kind of improved ADRC used in horizontal displacement decoupling control is proposed and the parameter setting rules is discussed in this paper. Theoretical and simulation comparison analysis show that the improved auto-disturbances-rejection control can make the horizontal displacement system have the characteristics of higher positioning precision, fast response and good robustness etc.Based on the related theoretical research, the experimental prototype is produced, and its performance is testified. The positioning accuracy is1μm, this can meet the submicron degree positioning requirements in microelectronics manufacturing industry. |
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