| The requirements of feeding speed and positioning accuracy in CNC machine tools are highly increasing for the modern manufacturing technology. The friction force of traditional CNC machine tools is one of the important factors that restrict the machine’s performance. Compared with the traditional feeding system of CNC machine tools, the maglev feeding system with high speed, high positioning accuracy, long life, no friction, no lubrication, no pollution, provides necessary conditions for the realization of ultra-high speed and ultra-high precision in CNC machine tools.The working principle of magnetic levitation technology was introduced and a new type of hybrid excitation maglev feeding platform was designed on the basis of the structural forms of the existing feeding platform at home and abroad. The main research contents are as follows:(1) The defects of the existing maglev feeding platform at home and abroad were analyzed. A new type of hybrid excitation maglev feeding platform was designed on the basis of the existing maglev feeding platform. The mathematical model of the hybrid excitation linear synchronous motor(HELSM) was established and the electromagnetic force characteristics of the HELSM were studied by numerical analysis and finite element analysis. The fluctuations of the electromagnetic force were improved.(2) The phenomenon of magnetic coupling was analyzed and decoupling control of the system was researched. The electromagnetic thrust and the normal electromagnetic force were completely decoupled after decoupling control. The levitation stability of the feeding platform was analyzed, and the results showed that feeding platform is stable and controllable in the balance position.(3) The finite element model of the maglev feeding platform was established, and the levitation system can be equivalent to a support system with spring and damping. The stiffness and damping ratio can be adjusted by the parameters such as structure, controller. The relationship between the static deformation, each modal and the levitation stiffness was analyzed. The structure of the feeding platform was improved and the optimal parameters were obtained.(4) The simulation experiment to determine its positioning motion was done by using the joint control simulation technology in ADAMS and MATLAB. The model of PID position feedback to the feeding platform was established. The simulation test for a number of parameters were done to get multiple output curves of displacement. The results showed that rational selection of the control parameters can lead an ideal position output curve of the feeding platform. The affects to the positioning accuracy of the feeding platform were analyzed and the results showed that the positioning accuracy of the feeding platform was mainly determined by the measurement accuracy of real-time measurement system. |
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