Current harmonics can increase motor losses in high-speed magnetic levitation turbo molecular pumps (MLTMPs) and also impair both the motor’s control performance and the vacuum performance of MLTMPs. Therefore, this paper proposes a high-precision harmonic decoupling suppression method applicable to high-speed motors. First, an adaptive filter based on the Recursive-Total-Least-Squares algorithm is designed to precisely extract harmonic characteristics. This algorithm accounts for input noise induced by position estimation errors and exhibits stronger robustness under low signal-to-noise ratio conditions. Then, the voltage harmonics generated by the current controller are accurately modeled and analyzed, and compensation for digital control delays is implemented. Additionally, a current harmonic regulator based on PI control and harmonic decoupling is designed to suppress current harmonics. Finally, the effectiveness and superiority of the proposed method are verified on a high-speed MLTMP platform.

Multiple frequencies high-amplitude magnetic interference in the environment can adversely affect the detection of cardiac magnetic field signals inside magnetocardiography device. Adaptive multi-resonance control (AMR) is suitable for suppressing such interference, but the stability of active magnetic field compensation system (AMC) will be destroyed by the influence of the time delay of the sensor. To address this problem, this paper proposes a interference suppression method that combines an improved adaptive multi-resonance controller (IAMR) with proportional differential (PD) and linear extended state observer (LESO). Experimental results show that PD-LESO-IAMR can effectively suppress multiple frequencies magnetic interference under the premise of ensuring system stability. Compared with conventional PD-LESO, the average magnetic field interference in the MSC can be reduced from 3.73 pT to 1.80 pT, and the maximum anti-interference ability was increased by 50.25%.

The MINI-magnetically shielded cabin (MINI-MSC) offers a near-zero magnetic environment for optically pumped atomic magnetometers (OPMs) to measure the magnetocardiography (MCG) and magnetoencephalography (MEG). However, the MINI-MSC’s confined interior and restricted uniform area make it challenging to capture high-quality bodily signals. Once the external interference surpasses the passive magnetic shielding capacity of the MINI-MSC, the volume and the homogeneity of the uniform region are reduced significantly, leading to the poor quality of the signal collected by OPMs. Therefore, an uniform active magnetic compensation system (UAMCS) composed of bi-planar coils (BCs) is introduced to suppress interference for enlarging the uniform region. The performance of the UAMCS depends on the BCs, but under finite-size ferromagnetic boundaries, approximate magnetic field values that deviate from reality are usually provided by the image method with the inaccurate calculation. To overcome these limitations, an analytical expression of the absorption current is derived to accurately characterize the coupling effect, thereby maintaining the high uniformity performance effectively. A forward analytical model is proposed to characterize magnetic fields, and the equivalent current could be analytically determined, which are put into the target field method (TFM) to express the superimposed the magnetic field. The inhomogeneity errors of BCs using the forward analytical model are 0.39 times of the image method. After the magnetic compensation, the signal-to-noise ratio at 0.1 Hz, 1 Hz and 10 Hz were improved by 39.5 dB, 34.3 dB, and 6.7 dB, respectively, verifying the magnetic noise can be well compensated in the whole target region. Note to Practitioners—The challenge of ensuring high signal quality in MINI-MSC for OPMs is critical in biomedical imaging applications. An forward analytical method is introduced to character the absorbed magnetic field of shielding layers, and an advanced UAMCS utilizing BCs is used for the precise magnetic field compensation to significantly enhance the signal-to-noise ratio. This approach addresses the limitations of traditional image methods, offering improved accuracy in magnetic compensation and enhance the reliability of MEG and MCG tests.

The Magnetoencephalography (MEG) based on atomic magnetometer has high demand for the uniformity in the measurement area. Due to the door and holes of the magnetically shielding room (MSR), the distribution of residual magnetic field is non-linear, introducing much trouble into the magnetic field compensation. This study proposes a method for improving the uniformity of the residual magnetic field in the compact MSR by injecting different currents into the two coils in each pair of the outside compensation coils. The model and theoretical analysis method have been established, the feasibility has been verified both by the simulation and the experimental test. Results show that the maximum of the three components of the residual magnetic field in the direction of the three axes can be reduced by 18 times, 10.6 times and 8.1 times, respectively, when compared with the results without compensation, and 2.4 times, 2.3 times and 2.2 times, respectively, when compared with the results compensated with the same current. This study can provide certain help for achieving ultra-weak magnetic environment with high uniformity for the MEG measurementNote to Practitioners—In this article, we focus on the problem of compensating the residual magnetic field in the compact MSR with high efficiency and low cost, which remains the key factor that limits the promotion of the MEG. Method based on the compensation coils in series outside the MSR only deals with the linear or symmetric components, but has nothing to do with the non-linear and asymmetric one caused by the door. We propose a new method for compensating the residual magnetic field based on the coupling between the active and passive shielding, high compensation efficiency and uniformity can be achieved. In future work, we will aim at applying this method to create an ultra-weak magnetic field environment with high uniformity for the MEG measurement.

Current measurement error (CME) could lead to large torque ripple, increased losses, and reduced control performance. The long-term operation under heavy load of magnetic levitation turbo molecular pumps (MLTMPs) makes their core component–the permanent magnet synchronous motor (PMSM)–particularly susceptible to CME, thereby reducing ultrahigh vacuum performance. This article introduces a novel method for correcting CME in PMSMs by analyzing phase current harmonics, which addresses the issue of traditional methods ignoring phase current distortion. First, a control model under the CME conditions is proposed, utilizing a Proportional Integral Resonant controller to mitigate periodic disturbances. Second, the quantitative relationship between the CME and phase currents is derived through harmonic analysis based on the proposed control model. Then, an improved synchronous frequency extractor is employed for the extraction and compensation of the CME. This method features ease of application, independence from motor parameters, and good real-time performance. Finally, experiments on MLTMPs validate the effectiveness of the proposed approach.

The high-amplitude magnetic field interference in the environment causes serious distortion of the cardiac magnetic signal measured in the central area of the magnetic shielding cylinder. The integration of a linear extended state observer (LESO) and a proportional resonance (PR) controller can effectively suppress high-amplitude magnetic interference at specific frequencies. However, the frequency of high-amplitude magnetic interference in the environment is variable, bringing challenges to conventional PR method. To address this issue, this article proposes a novel approach (LESO-AFE-PR) for suppressing magnetic interference by integrating an adaptive frequency estimator (AFE), PR, and LESO. The LESO-AFE-PR method can improve the capability of the active magnetic compensation (AMC) system to attenuate high-amplitude magnetic interference with random frequency. Experimental results show that the LESO-AFE-PR can adaptively track the frequency of magnetic field interference, effectively suppress interference in the range of 1$\sim$40 Hz, and attenuate the amplitude of magnetic field interference from 32.9 to 3.6 pT. Compared to the uncompensated state, a remarkable attenuation of approximately 89$\%$in magnetic field interference is achieved.

Position sensorless control of brushless dc motor has been an effective measure for size reduction and reliability improvement. However, the commutation error remains a significant factor limiting the motor operating efficiency. Therefore, a phase synchronization-based commutation error correction method is proposed in this article. First, the primary commutation error sources are analyzed, and the conventional commutation error correction methods are compared. Then, a commutation error construction and correction method is investigated to overcome the problem that the commutation accuracy is affected by noise interference and motor inductance in the conventional methods. By implementing the developed closed-loop correction system, desired commutation error correction performance is achieved. Finally, experiments are carried out for the effectiveness validation of the proposed method.

Precise commutation is crucial to improve the sensorless brushless dc motor efficiency. In order to achieve the high-precision commutation, this article develops a commutation auto-correction method. Three challenges of the conventional correction method based on signal integral have been addressed. First, the line voltage difference of adjacent phases is integrated to construct the feedback quantity, which avoids the interference from the phase current variation. Second, the integration interval compression strategy is proposed, which avoids the impact of commutation freewheeling current. Third, a novel averaging circuit is designed, which realizes the high-precision acquisition of the integral. At last, by using the integral as the feedback quantity, a proportional integral controller is introduced to implement the commutation auto-correction. In contrast to the conventional method, the above three approaches ensure the accurate commutation in cases of the phase current variation and high motor speed. The effectiveness of the auto-correction method is verified by the experimental results on a magnetically suspended turbo molecular pump.

Accurate commutation is a key factor to ensure the ideal electrical torque performance and high motor efficiency for position sensorless brushless dc motor. In order to eliminate the commutation error, this article presents a closed-loop correction method using the hardware-based floating phase back electromotive force (EMF) integration. First, the relationship between the floating phase back-EMF integral and commutation error is analyzed. Then, based on the relationship, a closed-loop controller fed by the integral is introduced to generate the angle to correct the commutation point. But the inaccurate integral calculation resulted from insufficient sampled point at high motor speed will seriously reduce the correction accuracy. For this reason, a novel hardware configuration is designed to transform the back-EMF integral into a filtered analog voltage. In this way, the integral can be obtained precisely from sampling the analog voltage with low sampling rate. Thus, a precise commutation is achieved by the closed-loop control, especially in the high speed range. Finally, experimental results on a magnetically suspended turbo molecular pump show the effectiveness of the proposed method.

Due to the asymmetry of the actual back electromotive force (back EMF), the performance of the conventional commutation deviation correction method degrades in sensorless control of the brushless direct current (BLDC) motor. This article proposes a high-precision sensorless optimal commutation deviation correction strategy, which considers the asymmetry problems of the back EMF. First, this article discusses the optimal commutation issues and the internal power factor angle based commutation deviation correction method. Then, given the issue of the nonsinusoidal phase current integration and the asymmetric back EMF, a dual improved second-order generalized integrator with a positive sequence component extractor (DISOGI-PSCE) is proposed. The DISOGI-PSCE can effectively deal with the dc component and harmonics in flux-linkage and current integration, as well as the asymmetry of the back EMF. Finally, experimental tests are performed on a magnetically suspended control moment gyroscope BLDC motor, which verified the effectiveness of the proposed high-precision sensorless optimal commutation deviation correction method.

Inaccurate commutation in brushless dc motor (BLDCM) will induce current harmonic and increase motor loss, which reduce motor efficiency. Meanwhile, for the sensorless BLDCM, the motor commutation is seriously affected by detection errors and calculation errors, which are caused by the nonideal conditions and the parameters variation. In this paper, a novel commutation error correction method is proposed to determine optimal commutation instant for the sensorless high-speed BLDCM. First, the relationship between commutation error and motor phase current is analyzed. According to this relationship, an initial commutation error can be calculated and compensated in one conduction interval. Then, online commutation corrections are performed to compensate for the residual error in following conduction intervals. The correction accuracy of commutation instant is determined by the phase current integral difference. This method is insensitive to motor parameters and back electromotive force waveform. Therefore, the commutation error is effectively eliminated in the whole speed range. Finally, the feasibility and effectiveness of the proposed method are evaluated by experimental results.

When the magnetically suspended control moment gyro (MSCMG) rotor rotates at high speed, the output signal of the displacement sensor will introduce an interference signal multiplied by the rotor speed. The signal will be amplified by the controller and the power amplifier to generate harmonic vibration, which seriously affects the stable operation of spacecraft. In order to suppress the multi-harmonic vibration produced by the control system, the dynamic model of the magnetically suspended high-speed rotor system is firstly carried out in this paper, and the generation of vibration force is analyzed. A multi-harmonic adaptive notch filter based on double input is proposed. Since the radial X and Y two-channel displacement signals of the magnetic bearing system have the characteristics of equal amplitude and mutual orthogonality, the adaptive notch filter is improved in this paper. The harmonic suppression is realized by adaptive tracking compensation of the displacement signal. Finally, magnetically suspended control moment gyro system is simulated. The results show that the multi-harmonic adaptive notch filtering method based on double input is used to realize the tracking compensation of the doubling frequency disturbance signal, which greatly reduces the harmonic current. The suppression of the harmonic vibration force of magnetically suspended control moment gyro has important significance and application value.

In order to receive ground signals efficiently, doubly salient permanent magnet (DSPM) motor which is applied in communication satellites as a drive needs to be activated frequently to adjust the attitude of communication satellites. Then, the initial rotor position of the motor must be estimated accurately at standstill for producing a steady and sufficient starting torque. If the rotor rotates during the estimation process, the pointing accuracy of the satellite pointing mechanism will be affected. To solve this problem, this paper proposes a novel rotor initial position estimation scheme based on the principle that different initial rotor positions can cause the variations of stator winding inductances. The identification signals, which do not cause the rotor to rotate during the identification process, are injected into the motor windings to identify the stator inductances. Thus, the variations of the winding inductances can be detected, and the initial rotor position can be estimated accurately by these variations. The proposed method is verified through experimental platform. The experimental results show that the initial rotor position is accurately estimated, and the starting performance of the DSPM is improved.

This paper focuses on the start-up strategy of a high-speed 100-kW brushless dc motor with small inductance using a voltage comparator. This paper includes three key technique contributions: 1) determining zero-speed positioning, 2) removing high-frequency disturbances, and 3) optimizing the controller parameters. The sensorless low-current start-up strategy is based on an amplification circuit: a low-pass filter circuit and a signal modulate circuit. The amplification circuit is used to amplify the amplitude of back electromotive force for detecting the rotor position at low speed, the low-pass filter circuit is used to remove high-frequency disturbances, and the signal modulate circuit is used to obtain the rotor position signal. A hysteresis control strategy is proposed against the load disturbance in the start-up stage. Experimental results show that the proposed sensorless start-up strategy can realize a low-current start-up.