The Study Of Bearingless And Brushless Dc Motor With Control System

With the advantages of high torque density, high efficiency and low noise, PM motors have been widely used in the industrial control and daily life. In order to solve the problems caused by the mechanical bearing abrasion, maintenance and replacement, the bearingless technology has been becoming the focus. In this paper, the follow issues are covered: the mathematical modeling of the ordinary PM bearingless brushless DC motor and finite element simulation, the improvement of suspend strategy to a consequent-pole bearingless motor and the realization of the digital system designed.First of all, in comparison with sine and square wave magnetic potential of two different rotor's suspension force features, we analyzed the impact of the rotor pole windings distribution on the levitation force ripple and confirmed the rotor pole-number and windings distribution structure. The mathematical model of radial suspension force was constructed, which was verified using ANSYS finite element simulation.Secondly, one method called zero-current orientation was proposed to fix the coaxial position of the stator and rotor, which had advantages to increase the precision and to avoid the impact during the measuring process. To the problem of the not equal each other in maximum suspension forces along different angle in the traditional control system, another improved strategy was proposed and the equal maximum suspension forces was realized. Moreover, a rotor angle measuring method was designed, as well as the measurement error was discussed in detail.Finally, the digital control system of the consequent-pole slice bearingless PM motor was designed, which was based on the TMS320F2812. The current closed-loop control theory realized by the SVPWM module within DSP was discussed, and the method of limitation to the results of SVPWM calculation output was also studied. A kit of control software in C language was realized. Through the system debugging, a consequent-pole slice bearingless PM motor was stability suspended in the rotation speed of 6000r/min.