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Front. Inform. Technol. Electron. Eng.  2013, Vol. 14 Issue (8): 600-611    DOI: 10.1631/jzus.C1300023
    
Self-sensing active magnetic bearing using real-time duty cycle
Ming Tang, Chang-sheng Zhu, Jie Yu
State Grid Sichuan Electric Power Research Institute, Chengdu 610072, China; College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China
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Abstract  In a self-sensing active magnetic bearing (AMB) system driven by pulse width modulation (PWM) switching power amplifiers, the rotor position information can be extracted from coil current and voltage signals by a specific signal demodulation process. In this study, to reduce the complexity of hardware, the coil voltage signal was not filtered but measured in the form of a duty cycle by the eCAP port of DSP (TMS320F28335). A mathematical model was established to provide the relationship between rotor position, current ripple, and duty cycle. Theoretical analysis of the amplitude-frequency characteristic of the coil current at the switching frequency was presented using Fourier series, Jacobi-Anger identity, and Bessel function. Experimental results showed that the time-varying duty cycle causes infinite side frequencies around the switching frequency. The side frequency interval depends on the varying frequency of the duty cycle. Rotor position can be calculated by measuring the duty cycle and demodulating the coil current ripple. With this self-sensing strategy, the rotor system supported by AMBs can steadily rotate at a speed of 3000 r/min.

Key wordsSelf-sensing      Active magnetic bearing (AMB)      Frequency spectrum characteristic     
Received: 20 January 2013      Published: 02 August 2013
CLC:  TP23  
Cite this article:

Ming Tang, Chang-sheng Zhu, Jie Yu. Self-sensing active magnetic bearing using real-time duty cycle. Front. Inform. Technol. Electron. Eng., 2013, 14(8): 600-611.

URL:

http://www.zjujournals.com/xueshu/fitee/10.1631/jzus.C1300023     OR     http://www.zjujournals.com/xueshu/fitee/Y2013/V14/I8/600


Self-sensing active magnetic bearing using real-time duty cycle

In a self-sensing active magnetic bearing (AMB) system driven by pulse width modulation (PWM) switching power amplifiers, the rotor position information can be extracted from coil current and voltage signals by a specific signal demodulation process. In this study, to reduce the complexity of hardware, the coil voltage signal was not filtered but measured in the form of a duty cycle by the eCAP port of DSP (TMS320F28335). A mathematical model was established to provide the relationship between rotor position, current ripple, and duty cycle. Theoretical analysis of the amplitude-frequency characteristic of the coil current at the switching frequency was presented using Fourier series, Jacobi-Anger identity, and Bessel function. Experimental results showed that the time-varying duty cycle causes infinite side frequencies around the switching frequency. The side frequency interval depends on the varying frequency of the duty cycle. Rotor position can be calculated by measuring the duty cycle and demodulating the coil current ripple. With this self-sensing strategy, the rotor system supported by AMBs can steadily rotate at a speed of 3000 r/min.

关键词: Self-sensing,  Active magnetic bearing (AMB),  Frequency spectrum characteristic 
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