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The suppression of harmonic vibration of active magnetic bearing (AMB) rotor system depends on the speed signal. Aiming at the problem of harmonic vibration suppression when the speed measurement sensor fails, a dynamic model of the AMB-rotor system including mass unbalance and sensor runout is established. This paper analyzes the main sources of harmonic vibration force, and proposes a double-input filter based on adaptive frequency estimation. The characteristic that the displacement output signals of the radial X- channel and Y- channel of the rotor are orthogonal to each other can be used to quickly and accurately estimate the actual speed of the rotor adaptively. At the same time, the harmonic components of the control current are also compensated. Finally, the effectiveness of the proposed harmonic vibration suppression method with adaptive frequency estimator is verified by the simulation and experiments.

Magnetically suspended control moment gyro (MSCMG) is used in high-performance satellite platforms such as ultraquiet and ultrastable satellite. However, due to the unbalanced mass and sensor runout, the harmonic vibrations of synchronous and multifrequency will be generated, which will affect satellite performance. Aiming at the problem of harmonic vibration suppression of MSCMG, this article proposes a control algorithm based on multisynchronous rotating frame transformation. The electromagnetic force of the active magnetic bearing in MSCMG is directly used as the input signal of the control algorithm to achieve zero magnetic force control. This algorithm uses the orthogonal characteristics of the output signals of the X -direction and Y -direction displacement sensors. The vibration force in both directions can be suppressed by one controller simultaneously, saving the computing resources and having a faster response speed. The stability of the proposed method and the robustness to frequency fluctuations are analyzed. By changing the phase compensation angle in different frequency ranges, the stability of the system in the whole frequency band is ensured. Finally, experimental results are given to verify that the proposed method can achieve high precision and fast response suppression of harmonic vibration.

Imbalanced vibration generated during the operation of a high-speed rotor inside a gyro is transmitted to the magnetically suspended control moment gyro (MSCMG) through a magnetic bearing stator, resulting in micro-jitter. This greatly affects the control accuracy of the spacecraft attitude. In order to effectively suppress micro-jitter, the dynamic model of the magnetically suspended rotor with imbalanced mass is established in this paper, and the imbalanced characteristics of the high-speed rotor are analyzed. Finally, a double-channel adaptive least mean square (LMS) error algorithm is proposed. By utilizing that the radial X- and Y- displacement signals from the rotor displacement sensor are orthogonal to each other, a feedforward correction is applied to adaptively compensate the residual displacement stiffness of the magnetically suspended rotor system due to mass imbalance. While eliminating this synchronous current, the proposed algorithm also offsets the adverse effects of the low-pass characteristics of the power amplifier. Simulation and experimental results show that the method compensates the synchronous displacement stiffness force generated by the system with high precision, and realizes the micro-jitter control of the magnetically suspended control moment gyro.

The active magnetic bearing rotor in magnetically suspended control moment gyro (MSCMG) will produce unbalance vibration due to the mass unbalance, and the frequency equal to the rotation speed. In order to suppress the unbalance vibration of MSCMG, the working principle of the active magnetic bearing (AMB) is introduced and the unbalance vibration model is established. And then, a high-precision closed-loop detection method of the synchronous signal based on synchronous rotating frame transformation (SRFT) is proposed. This method can detected synchronous signals in two directions at the same time, with less calculations. The synchronous current is suppressed by detecting and compensating the synchronous component in the output signal of the displacement sensor, which can reduce most of unbalance vibration. The phase modulation angle is introduced to make the algorithm have a wider stable range. In order to simplify the analysis method, the orthogonal characteristic of the output signal of the displacement sensor is used to equalize the dual output system to a complex-coefficients single-input system, and the dual frequency Bode diagram is used to analyze and evaluate the stability of the system. Finally, experimental results are given to verify that this method can effectively suppress synchronous current.

The active magnetic bearing system exhibits mass imbalance and sensor runout which cause the system to generate harmonic vibration force and moment. Repetitive control is an effective method to eliminate such harmonic vibration. Traditional repetitive control will eliminate all of the harmonic frequency components. However, in a practical system, the odd harmonic components usually dominate. Meanwhile, the existing method only suppresses the vibration force in the magnetic bearing system, and there is little research on the suppression of moment. Aiming at these problems, the harmonic vibration moment of the active magnetic bearing system is taken as the control object. This study investigates a hybrid control method that combines a second-order odd harmonic repetitive control with finite-dimensional repetitive control. And the virtual variable sampling is applied to construct any virtual sampling period in the proposed method, which effectively solves the problem of non-integer delay of digital repetitive control. The stability of the active magnetic bearing system is analyzed. The experimental results show that this method has faster response speed and better robustness when the frequency fluctuates.

Traditional open-switch fault diagnosis methods suffer from poor rapidity or robustness. To solve this issue, a new differential current observer-based fault diagnosis method is proposed in this article. With the designed differential observer, fault symptoms (residuals) can be generated and adopted for fault diagnosis easily. Considering that the residuals are sensitive to motor operating condition in the conventional model-based method due to model error, an adaptive fault detection threshold is designed. As a result, the false detection and missed detection caused by the change of working condition can be avoided, and stronger robustness against speed, load, and parameter variations can be achieved with superior rapidity compared with existing methods. Finally, the rapidity and robustness of the proposed fault diagnosis method are verified sufficiently through experimental results.

Permanent magnet synchronous motor always suffers from air gap field distortion and inverter nonlinearity, which lead to the harmonic components in motor currents. A resonant controller is a remarkable control method to eliminate periodic disturbance, whereas the conventional resonant controller is limited by narrow bandwidth and phase lag. This article presents a novel resonant controller with a precise phase compensation method for a permanent magnet synchronous motor to suppress the current harmonics. Based on the analysis of the current harmonic characteristics, the proposed resonant controller for rejecting a set of selected current harmonic components is plugged in the current loop, and it is parallel to the traditional proportional–integral controller. Furthermore, the stability analysis of the proposed resonant controller is investigated, and the parameters are tuned to get a satisfactory performance. Compared with the conventional resonant controller, the proposed resonant controller can achieve good steady-state performance, dynamic performance, and frequency adaptivity performance, simultaneously. Finally, the experimental results demonstrate the effectiveness of the proposed suppression scheme.

Harmonic currents in magnetically suspended rotor systems are usually caused by mass unbalance and displacement sensor errors, which will produce harmonic vibrations. Repetitive control (RC) is used to eliminate harmonic currents in the control system, but for the magnetic bearing control system, the odd harmonics often dominates, and the characteristics of the even harmonic frequency are not expected to change greatly. At the same time, the ratio of the sampling frequency to the rotor frequency is required to be an integer in the conventional repetitive controller (CRC), which greatly limits its range of application. Therefore, a 3/2-order dual-mode fractional-order repetitive control scheme with a three-parallel structure is proposed. The three branches in the scheme can not only eliminate odd and even harmonics independently, but also improve the robustness of frequency fluctuations. In addition, this method converts the fraction into an integer polynomial by Lagrange interpolation, which can accurately suppress the harmonic current at any frequency. The system delay is reduced to $0.5{N}$ sampling periods, and the system dynamic response rate is accelerated. Simulation results show that the proposed algorithm can effectively achieve harmonic vibration suppression at any frequency.

Repetitive controllers are widely used in rotor systems of magnetically suspended control moment gyro, which are responsible for suppressing harmonic current because of sensor runout and mass imbalance of the rotor. However, the rotation frequency of the rotor is not constant in industrial applications, and it is likely to fluctuate around the rotation frequency, which greatly affects the suppression effect of the repetitive controller on harmonic current. This article proposes a new repetitive control method with strong frequency robustness, which still has high suppression accuracy when the rotation frequency is fluctuant. This method is simulated and verified on the magnetically suspended rotor system, which has achieved better results than previous research.

In magnetically suspended rotor (MSR) systems, harmonic current mainly originates from rotor mass imbalance and sensor runout, which can generate multifrequency vibration. Repetitive control (RC) is an effective method to eliminate periodic disturbance from a control system. Conventional RC (CRC) method requires the exact knowledge of the period of the periodic signal. However, in some applications, the period may fluctuate or may not be available with sufficient accuracy, in which case the performance of the CRC severely decays. Besides, the transient response of the CRC is relatively slow. In response to these issues, a second-order RC that incorporates dual mode structure scheme is presented in this paper. By introducing Lagrange-interpolation-based fractional delay filters, the current suppression accuracy gets enhanced in fractional cases. The stability criterion with rigorous proof for the proposed scheme is addressed. The sensitivity to period-time of the proposed scheme is analyzed as well, from the aspect of sensitivity transfer function. Simulation and experimental validations are performed on an MSR to show the effectiveness of the proposed approach.

In magnetically suspended rotor (MSR) system supported by active magnetic bearings, the mass imbalance of the rotor and the sensor runout lead to multi-frequency vibration of the rotor system, which seriously affects the operation accuracy. In order to suppress the harmonic vibration in the MSR system, an improved second-order repetitive control (SORC) method based on parameter optimization is proposed. Firstly, the dynamic model of MSR system is established. The necessity of restraining the current stiffness force can be confirmed through the division and further analysis of the bearing force. Then, an improved SORC structure diagram is constructed, and the coupling relationship between control gain and weight factor is determined by system stability criterion. Next, for the rapidity, stability and steady-state accuracy in the convergence process, parameters are optimized separately. Then, stage integration can achieve a better balance of performance impacted by parameters. Finally, the simulation results show that the proposed scheme can effectively suppress the multi-frequency vibration of the MSR system.

In order to reduce the torque ripple and running loss caused by the commutation error in the brushless DC motor (BLDCM) of the magnetically suspended control moment gyroscope (MSCMG), this study proposes a novel method dealing with commutation error in sensorless controlled BLDCM by rapid phase extraction and compensation technique. First, a traditional virtual neutral point circuit consisted of three-phase resistance network and low-pass filter are used to obtain the zero-crossing points of the non-conducting phase back electromotive force without noise interference. Then, an improved phase extraction method is built after analysing the DC-link current. Commutation error is extracted from DC-link current with the improved phase extractor rapidly. Furthermore, the effect of speed offset caused by fluctuation during phase extraction is also analysed and an adaptive commutation error compensation method based on the DC-link current phase extraction is proposed. Finally, simulation and experimental results performed on the high-speed motor of MSCMG verify its effectiveness and rapidity. The main novelties of this study are the direct phase extraction algorithm with natural parameter insensitivity and robustness and the rapid iterative commutation error compensation method based on the extraction algorithm.

In magnetically suspended rotor (MSR) system, harmonic vibration appears inevitably produced by mass imbalance of the rotor and sensor runout. Least mean square (LMS) is one method to reject the harmonic frequency component of the disturbance in a control system. Nevertheless, the performance of the conventional LMS is not optimal and the transient response is relatively slow. In this paper, the rotor dynamic model including mass imbalance and sensor runout is built, and the mechanism of vibration is analyzed. A harmonic vibration force suppression method based on frequency-domain adaptive LMS is proposed. Compared to the existing adaptive LMS methods, this article introduces a new convergence factor in frequency domain, which improves the updating strategy of the step size and the convergence rate of the algorithm. Simulation results demonstrate that the proposed method can effectively restrain the harmonic vibration force of magnetically suspended rotor system.

Odd-harmonic current induced by mass unbalance and sensor runout in magnetic bearing coil current of magnetically suspended rotor (MSR) system will cause harmonic vibration. In this paper, a hybrid odd repetitive controller (HORC) is proposed to suppress harmonic current in MSR system. On one hand, frequency robustness of the proposed algorithm is better than that of conventional repetitive controller when the fundamental frequency of harmonic current is fluctuant around the nominal value of rotation frequency. On the other hand, the dynamic response is also accelerated. Meanwhile, a stability criterion is presented to prove the stability of MSR system. The proposed algorithm has good potentials for MSR system. Simulation results verify the effectiveness of the proposed method.

In a magnetically suspended rotor (MSR) system, harmonic current mainly caused by mass imbalance and sensor runout would produce harmonic vibration. Repetitive control (RC) is one remarkable approach for eliminating such harmonics. Conventional RC (CRC) attempts to compensate for all frequency components simultaneously. However, in the practical MSR system, it is usual that the current comprises only odd-harmonic components. This paper investigates a modified odd-harmonic RC (MORC) scheme to respond to this issue. The signal generator of arbitrary-order discrete-time periodic signal is established, by which the general forms of CRC and ORC can be obtained. Besides, it is proved that ORC with halved data memory possesses a faster convergence rate, higher repetitive gain, wider frequency bandwidth at the targeted frequency and greater robustness to frequency fluctuation than CRC. The stability criterion for the MORC-controlled MSR system is proved as well. Simulation and experimental results have highlighted the effectiveness of the proposed approach.