| The traditional mechanical thrust bearing has following defects, such as friction, wear, temperature rise and so on, which affect the rotation speed and precision of rotating machinery. In order to overcome the shortcomings mentioned above and satisfy high-speed requirement of modern rotating machinery, the digital control system of Magnetic Thrust Bearing(MTB)is designed here, basing on magnetic suspension technology.The principle of MTB and its basic composition are introduced briefly in the thesis. Basing on the analysis of motion equation of MTB, the transfer function of MTB is derived, which lay the theoretical foundation for the control system design of MTB.A switching power amplifier is designed according to the features of requirements of MTB, and the basic characteristic, efficiency and ripple are analyzed. Besides, a type of two-level PWM switching power amplifier is designed. On the basis of that, three-level PWM switching power amplifier is designed. Theoretical analysis shows that three-level PWM switching power amplifier can reduce the current ripple effectively and improve the current response speed.A TMS320LF2407A DSP (Digital Signal Processing)is adopted as the main controller, which is easy to achieve high speed and precision. The basic circuit of DSP is designed, which includes A/D conversion circuit, D/A conversion circuit, power circuit, clock circuit, displacement detecting circuit and so on.The accurate mathematic model of MTB cannot be obtained, because of the nonlinearity and parameters uncertainty. Ideal controlling effect usually cannot be obtained using traditional PID controller. Therefore, the application of fuzzy self-adaptive PID in MTB is studied, and the traditional PID control algorithm and fuzzy self-adaptive PID control algorithm based on DSP are established. Besides, the control system is simulated using MATLAB. Simulation results indicate that fuzzy self-adaptive PID is more suitable for the stable suspension of MTB. |
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