In order to improve the performance of the high-speed brushless direct current motor drives, a novel high-precision sensorless drive has been developed. It is well known that the inevitable voltage pulses, which are generated during the commutation periods, will impact the rotor position detecting accuracy, and further impact the performance of the overall sensorless drive, especially in the higher speed range or under the heavier load conditions. For this reason, the active compensation method based on the virtual third harmonic back electromotive force incorporating the SFF-SOGI-PLL (synchronic-frequency filter incorporating the second-order generalized integrator based phase-locked loop) is proposed to precise detect the commutation points for sensorless drive. An experimental driveline system used for testing the electrical performance of the developed magnetically suspended motor is built. The mathematical analysis and the comparable experimental results have been shown to validate the effectiveness of the proposed sensorless drive algorithm.

In order to improve the performance of surface permanent magnet synchronous motor (PMSM) drives, a novel sensorless drive scheme is proposed in this paper, which is based on the virtual third-harmonic back-EMF incorporating a fraction-N phase-locked loop (FN-PLL) and a synchronous frequency-extract filter (SFF). A simple low-pass filter based circuit is used to obtain the commutation points through the virtual third-harmonic back-EMF. After that, an FN-PLL is applied to catch continuous rotor position angles. On this basis, the SFF-based compensation is proposed to compensate the detecting error adaptively. Meanwhile, the field vector control loop for surface PM motor is proposed, which is based on the proposed rotor position detection link and compensation link. An experimental high-speed magnetically suspended blower platform is built. The effectiveness and the feasibility of the proposed method are validated with experimental results.

Surge is one of the main factors affecting the stability of the centrifugal compressor. This article investigates surge disturbance suppression of active magnetic bearing (AMB)-rotor systems in magnetically suspension centrifugal compressors. An active disturbance control method is adopted to make the rotor stably levitate under surge disturbance. First, the dynamic model of the magnetic bearing rotor is established and simplified into a single-channel model. Second, a third-order linear extended state observer (LESO) and a linear active disturbance rejection controller are designed. The performance analysis of the controller shows that the estimation error accumulation of the observer is bounded and the estimation errors decrease with the increase of the observer bandwidth. Furthermore, the variable differential parameter added in the differential link of the controller can flexibly adjust the system damping. A method of tuning parameters for linear active disturbance rejection control (LADRC) is proposed to suppress surge disturbance while satisfying the stability of the system. Finally, the results of the experiment demonstrate that the proposed scheme is effective in suppressing the large-scale vibration effect of the surge disturbance on the rotor, and the magnetically suspended centrifugal compressor (MSCC) can run stably with low amplitude under the modified surge and mild surge.

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.

The MINI-magnetically shielded room (MINI-MSR) offers a near-zero magnetic environment for the high performance of optically pumped atomic magnetometers (OPMs) in magnetoencephalography (MEG) tests. It has the advantages, such as being small-sized, portable, lightweight, offering efficient space utilization, and being cost-effective. However, owing to its small size and narrow internal space, the MINI-MSR can only provide a limited uniform region with larger gradients and irregular magnetic noise distributions. Moreover, it is affected by large external background fluctuations. Once the external interference exceeds the magnetic shielding capacity of the MINI-MSR, the precision of OPMs is compromised. Therefore, an active magnetic compensation system (AMCS) composed of biplanar coils (BCs) is introduced to enlarge the uniform region, maintaining the inhomogeneity errors below 1% to meet the measurement accuracy. However, conventional algorithms for designing BCs struggle with searching for the regularization coefficient ω that determines the coil’s shape. The process lacks ergodicity and efficiency, posing challenges in obtaining maximum volume and uniformity within the target region. In this study, a new hybrid method (NHM) composed of the target field method (TFM), image method (IM), and novel artificial fish swarm algorithm (novel ASFA) is proposed to design BCs for the AMCS. The aim is to suppress background field fluctuations, enhancing the signal-to-noise ratio while addressing coupled errors to reduce larger gradients and magnetic noise levels. Experimental results show that the maximum inhomogeneity error of BCs is less than 1.23%, which is consistent with simulation results. The sensitivity of the AMCS at 0.01 Hz ranges from 180 to 0.16 pT/Hz ^1/2 , realizing the noise suppression ratio of 30.51 dB. Based on the closed-loop AMCS, the signal-to-noise ratio in the alpha rhythm generation task is effectively improved.