Stability Analysis And Control Of Magnetic Levitation Guide With Over-constrain

Active magnetic levitation guide system is a new planar multi-point supporting system, where the workbench is levitated steadily by electromagnetic force. Compared with ordinary guide, active magnetic levitation guide has some advantages, such as non-frictional-resistance, non-wear, non-lubrication, high precision and long life.Because of no contact between the slide box and the guide plate of the active magnetic levitation in relative motion, the moving resistance is greatly reduced and the motion response of the guide is improved. Active magnetic levitation guide can provide technology support for the improving feed speed of numerical control machine, it also can avoid the falling of machining accuracy and the shortening of service life that result from mechanical friction and direct contact. Therefore, the reliability of the active magnetic levitation guide is higher than traditional guide. Compared with hydrostatic guide, active magnetic levitation guide can reduce environmental pollution and ultra clean dust prevention conditions owing to the oil auxiliary equipment. Therefore, the bearing technology in active magnetic levitation guide will be developed rapidly.Considering the bearing characteristics of guide, the working plane of the active magnetic levitation guide must be supported by multi-point. However, this multi-point support has active over-constraint. With the further research of active magnetic levitation technology, it can be found that the chatter is caused by active over-constraint of active magnetic levitation guide with multi-point support. It will be made difficult that advanced control strategies can be applied to active magnetic levitation guide system,bearing capacity and control precision of the active magnetic levitation guide couldn't be further improved and even the research is hindered by the chatter. Firstly, the flutter in active magnetic levitation guide system with multi-point support is mainly studied and a new method which is called as magnetic damping control method is proposed to solve flutter. Then, a characteristic-oriented control strategy is studied based on PID control,model reference adaptive control and sliding mode variable structure control. The performance of active magnetic levitation guide system is further enhanced by this characteristic-oriented control strategy and nonlinear compensation method. Finally,experimental platform of the active magnetic levitation guide is built, and its relevant simulation and experimental research is carried out. It can eliminate the influence of flutter and make the system run steadily and improve the performance. In this paper, the main work is described as follows.1. The structure of the active magnetic levitation guide is designed and its working mechanism is analyzed. The mathematical model is further established and the stiffness and damping characteristics is analyzed and calculated.2. Considering the active over-constrain of active magnetic levitation system with multi-point support, a new method of magnetic damping control is presented by analyzing the mechanism of flutter caused by the active over-constrain. This new magnetic damping control method is used to solve the flutter of active magnetic levitation system with multi-point support. The normal magnetic damping model of active magnetic levitation guide is established and its reluctance force is calculated,which provides a necessary theoretical basis for solving the flutter of the active magnetic levitation guide system with planar multi-point support.3. After solving flutter, a characteristics-oriented control strategy is proposed.According to three states of the active magnetic levitation guide system, that is steady state, transition process state and impact state, the relevant control system is established by using PID dominant control strategy, model reference adaptive dominant control strategy and sliding mode variable structure dominant control strategy respectively. This control system and its simulation are operated to further improve the performance of the active magnetic levitation guide and it plays an important role in the technical difficulty of realizing multi-point support system.4. Nonlinear power amplifier, which is previous research results, is applied in active magnetic levitation guide system to reduce the nonlinear influence and make the control object convert into an equivalent linear system. Similarly, some advanced algorithms can be utilized to further expand the stable region of this system.5. The hardware and experimental platform of the active magnetic levitation guide system is built and it can provide a condition for verifying the conclusion. The experiment platform of active magnetic levitation guide based on DSP TMS320F28335 is built. Based on this experiment platform, related experiments of hardware and software debugging are carried out, especially the main control chip and displacement sensor.Relevant parameters are analyzed and the main hardware circuit is designed. The magnetic damping control and the characteristics-oriented control strategy of the active magnetic levitation guide system are verified by the developed experimental platform.Finally, research work is summarized and the further research work is put forward.