The vibration suppression in the presence of gyroscopic effects is an important issue for safe operations in magnetic bearing levitated varying speed rotor system. This work proposes a synchronous vibration control method with a two-stage notch filter for the magnetically suspended rotor system with strong gyroscopic effects. First, the dynamics of the magnetically suspended rotor system with synchronous vibrations in the rotational motion is modeled. Then the proposed two-stage notch filter is designed and the solution of the two-stage switching point is derived to distinguish low speed and high speed. Stability analysis is also presented in the low-speed region and the high-speed region, respectively. Finally, simulation results demonstrate that the stability can be guaranteed by adjusting the phase shift angle of the notch filter over the entire speed range. Further experimental results confirm the effectiveness of the proposed suppression method.

Video cameras are capable to collect high-density spatial data as each pixel is a sensor. An issue is that the video data is difficult to convert into the motion information, such as displacement. This paper presents a novel camera-based vibration measurement methodology for the lightweight structure. First, the phase-based motion extraction method is improved by directly transforming the phase variations into the displacement without the computation of phase gradient. The displacement is then converted into acceleration information to describe the vibration. Moreover, the proposed vibration measurement is investigated for a lightweight structure without attached sensors to change the physical properties. The measurements of the acceleration signals from camera and accelerometer are compared for verification. The experimental results for the effect of mass-loading, different camera parameters and down-sampling on the measurement validate the effectiveness of the proposed method.

Magnetically suspended centrifugal compressor (MSCC) is a better energy-saving choice than ordinary centrifugal compressor in industrial applications. However, harmonic currents, which generate from rotor mass unbalance and sensor runout, cause harmonic vibrations which deteriorate the stability of the overall system and lead to higher power consumption. The conventional repetitive controller (CRC) has been used to eliminate harmonic vibrations in magnetic bearing systems, but the CRC method has the drawbacks of frequency shift and shallow notch depth that degrade its performance of harmonic currents suppression. In this paper, a zero-phase odd repetitive controller (ZORC) is proposed. Compared to the CRC, the ZORC has control action only at odd harmonic frequencies and it has no influence on the closed-loop system at even harmonic frequencies. Besides, the conventional first-order low pass filter is replaced with the zero-phase low pass filter and moved outside the internal loop, which dramatically improve its performance of suppressing harmonic currents. The validity and effectiveness of the proposed method are proved both by simulation and experimental results.

Back-EMF zero crossing-based sensorless motor driving method suffers from a starting problem since there is no back-EMF at standstill, while the V/f or I/f based method is parameter sensitive. Without position sensors, smoothly driving a non-salient BLDC motor from standstill is difficult. To solve this problem, the relationship between pre-position current, energizing time, and transient speed in startup process is analyzed. Based on this relationship, starting from standstill and directly switching to self-synchronization stage can be realized without external- synchronization process. In addition, to lower the back-EMF zero-crossing points (ZCPs) detection speed, the line voltages difference ZCPs detection circuit is designed, and a novel phase error correction method based on neuro-fuzzy controller (NFC) is presented to provide accurate commutation point in the high-speed range. The experimental results show that reliable startup and accurate commutation can be guaranteed by the proposed strategy.

Video-based measurement, as one of the most common noncontact measurement methods for industrial inspection, has been developed rapidly. Digital video cameras offer the benefit of low cost, high automation, and are capable to make the simultaneous full-field measurement. This article focuses on studying the microvibrational signal extraction for high-speed rotating machinery with digital cameras. An improved phase-based motion extraction and learning-based video magnification are proposed for measuring the microvibration with high frequency and small amplitude. The phase-based motion extraction is improved by directly transforming the phase variations into the displacement without the computation of phase gradient. Furthermore, the learning-based motion magnification is utilized to amplify and qualitatively measure the microvibration in specified frequency bands. The phase-based motion extraction is a quantitative measurement, while the learning-based video magnification is a qualitative measurement. Experimental results for microvibration measurement rising from a magnetically suspended motor system validate the effectiveness of the proposed method.

The synchronous vibration rising from the magnetically suspended flywheel (MSFW) will drastically reduce the pointing precision of the satellites. In this paper, the high precision suppression for the frequency-varying synchronous vibration forces in the permanent-magnet-biased hybrid MSFW is investigated. First, the synchronous vibration forces generated in the permanent-magnet-biased hybrid magnetic bearing are modeled and analyzed. Then, a practical and effective synchronous vibration suppression method is proposed to plug into the baseline magnetic suspension system. The proposed method ascertains the overall system stability over the entire speed range by an adjustable phase angle. Moreover, it eliminates the residual synchronous vibration forces in the negative displacement stiffness by considering phase-lag influence of the power amplifier. The direct testing for the synchronous vibration forces proves the feasibility of the proposed suppression method.