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In order to suppress the synchronous unbalance vibration of the active magnetic bearings (AMBs) rigid rotor system in the full rotational speed range, the polarity switching control (PSC) can effectively suppress the synchronous unbalance vibration of the AMBs-rigid rotor system before and after the rigid cylindrical mode frequency, and the impact of the switching polarity on the system was reduced by using a disturbance observer. However, considering the rigid conical mode, the PSC could not guarantee the synchronous unbalance vibration suppression of the AMBs-rigid rotor system in the full rotational speed range including the rigid cylindrical mode frequency and the rigid conical mode frequency, and the system stability also changes accordingly. This article proposes a synchronous unbalance vibration suppression method based on the four-factor PSC (4-FPSC), which adjusts four polarity factors to suppress the synchronous unbalance vibration before and after two rigid mode frequencies. Besides, the disturbance observer is also avoided. Finally, simulation and experiment results verify the 4-FPSC can effectively suppress the synchronous unbalance vibration of the AMBs-rigid rotor system in the full rotational speed range including the rigid cylindrical and conical mode frequencies. [ABSTRACT FROM AUTHOR]

In active magnetic bearings (AMBs) supported rigid rotor systems, the unbalance compensation strategy based on a notch filter was often used to suppress the synchronous unbalance vibration when the rotor operates in the steady-state rotational speed. Whereas the rotor operates in a rotational-speed range including the critical rotational speeds, conventional notch filters should be improved to suppress the unbalance vibration. In most cases, improving the structure of the notch filter, such as a cross-feedback notch filter, phase-shift notch filter, adding the polarity switch or two-stage switch, was considered to make the notch filter work in the rotational-speed range. However, the improved notch filter may affect the stability of the AMBs rotor systems and result in large vibrations when the polarity switch or two-stage switch shifts. To avoid the shortcomings of these methods, a method using a variable angle compensation algorithm was proposed to suppress the synchronous unbalance vibration in finite iterative seeking processes, directly realizing unbalance compensation according to real-time rotor position. Finally, the effectiveness of the method proposed is verified by simulation and experiment results. [ABSTRACT FROM AUTHOR]

For the unbalance vibration of the rigid rotor system on active magnetic bearings (AMBs) supported high-speed motors in the full rotational speed range, a method based on the polarity switching tracking filter (PSTF) and the disturbance observer (DO) is proposed to achieve vibration suppression. To identify the synchronous unbalance vibration, a positive polarity tracking filter and a negative one are adopted before and after the rigid critical rotational speed range, respectively. The rigid critical rotational speed is in this range whose lower/upper limit is the negative/positive polarity switching frequency. Although the PSTF can effectively reduce the rotor vibration when it rotates at subcritical rotational speed range and supercritical range, the vibration increases evidently and even destabilize the system within the rigid critical rotational speed range. It means that the PSTF cannot suppress the rotor unbalance vibration in the full rotational speed range. However, this vibration during the rigid critical rotational speed range can be considered as a kind of disturbance and the DO is adopted to observe it, then the vibration identified is compensated in the control current to reduce the rotor unbalance vibration in the rigid critical rotational speed range. Therefore, the method based on the PSTF and the DO can suppress the unbalance vibration in the full rotational speed range. Finally, simulation and experiment results demonstrate that the method proposed can effectively suppresses the synchronous unbalance vibration of the AMBs-rigid rotor system in the full rotational speed range. [ABSTRACT FROM AUTHOR]

Nowadays, high-frequency switching power amplifiers (SPA) have been studied widely; bulk of the researches were focused on audio power amplifiers. In active magnetic bearing (AMB) systems, high-frequency electromagnetic excitation caused by rotor imbalance can affect the performance of the SPA, so the traditional SPA cannot meet the requirements of the AMB systems. Therefore, on the premise of ensuring larger power, the frequency of the SPA should be improved to ensure the normal operation of the AMB system. Two-level pulsewidth modulation (PWM) current-mode SPAs are widely used in AMB systems. In order to broaden the bandwidth and to reduce the average steady-state error current, SiC power devices based SPA with a high bus voltage and a high switching frequency was designed. The basic principle and the linearized control model of SPAs are introduced. Then, the duty ratio stability and average steady-state error current of the SPAs are analyzed based on the output ripple current. When the PWM modulator is designed by either the discrete devices or the integrated chips, the critical gains to ensure the duty ratio stability are, respectively, analyzed based on the slope matching and the nonideal characteristic of operational amplifiers. Hence, two methods to reduce the average steady-state error current are proposed, respectively. One is to adjust the offset voltage of triangular carrier for the P controller, the other is to use a proportional integral (PI) controller. The offset adjusting method allows the SPA to achieve better dynamic performance and wider bandwidth. The proportional integral (PI) controller can reduce the average steady-state error current but narrows the bandwidth. Finally, the experiment results are in good agreement with the theoretical analyses. [ABSTRACT FROM AUTHOR]

The self-sensing active magnetic bearing (SAMB) rotor systems own the benefits of reduced cost and better system integration, from the substitution of rotor displacement estimation for external sensors. However, the self-sensing errors between the real and estimated rotor displacement, together with the unbalance force and sensor runout, will act as disturbances that affect the SAMB rotor system, inducing current fluctuations and rotor vibrations. This paper presents a disturbance suppression method for the modulation-type SAMB rotor systems, in which both the amplitude and phase of disturbances are identified and real-time updated. A lumped multifrequency disturbances model is established. And a disturbances identification algorithm with object function value-based step vectors is proposed. The system stability and method convergence conditions are analyzed. The convergence rate, overshoot and antinoise capacity of the method are verified through simulations. In the end, the effectiveness and performance of the suppression method are validated through steady state and varying rotational speed experiments on a 4-DOF radial SAMB rigid rotor platform. [ABSTRACT FROM PUBLISHER]