Application of active magnetic bearings in flexible rotordynamic systems - A state-of-the-art review

Two-stage oil-free centrifugal air compressors can bring significant advantages and open new market opportunities for compressor manufacturers. One of the core technologies behind this compressor type is the high-speed electrical machine supported by active magnetic bearings. In this paper, the requirements set by the compressor on the electrical machine design are presented. The design solutions aimed to satisfy these requirements are discussed. Two case studies illustrate possible design approaches for the target application with examples of a 120-kW, 60 000-r/min induction machine with a solid rotor and a 225-kW, 50 000-r/min permanent-magnet synchronous machine (PMSM) with a full cylindrical magnet. The system design and simulation results are confirmed by measurements of a PMSM prototype.

Design Aspects of High-Speed Electrical Machines With Active Magnetic Bearings for Compressor Applications

Winding currents contain lots of harmonics if motors rotate at a high speed. This paper addresses two key challenges on the harmonic suppression: 1) using the multiple synchronous rotating frame transformations (MSRFTs) to get the primary signals, and 2) proposing the closed-loop detection system (CDS) to extract the harmonics accurately. First, the mathematical model containing the harmonics was built. Second, the MSRFTs were introduced and the high-precision detection method called the CDS was analyzed. The CDS has a higher harmonic detection accuracy than the open-loop method and can enhance the disturbance rejection capability of the system. Third, the parameter-independent compensation algorithm was proposed to enhance the robustness against the motor parameter variations, which was combined with the compensation calculated by the mathematical model to suppress the harmonics. The effectiveness of the proposed harmonic suppression strategy was verified by the experiments on the turbo molecular pump.

Selective Current Harmonic Suppression for High-Speed PMSM Based on High-Precision Harmonic Detection Method

High-speed (HS) electrical machines provide high system efficiency, compact design, and low material consumption. Active magnetic bearings (AMBs) bring additional benefits to the HS system, such as elimination of the friction losses, reduced wear and maintenance, and a built-in monitoring system. HS drivetrains are usually designed for specific applications and require a high level of integration. This paper describes a design method of the HS electrical machine supported by AMBs, considering their mutual influence on the system performance. The optimization procedure, which takes into account both the electrical machine and bearing designs, is developed. The optimization is based on a multiobjective genetic algorithm. The selected optimization parameters include the AMB and machine dimensions. The optimization objectives cover the electrical machine performance and the rotordynamics. The results of the proposed optimization algorithm are implemented in the constructed 350-kW, 15 000-r/min induction machine with a solid rotor supported by AMBs. The prototype tests verify the design and optimization results.

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High-Speed Electrical Machine with Active Magnetic Bearing System Optimization

Unbalance vibration suppression for AMBs system using adaptive notch filter

The vibration controllability is an important feature in the applications of active magnetic bearings (AMBs). This paper addresses the two key challenges on the active balancing control of AMB-rotor systems: presenting a parallel-mode scheme to enhance the notch performance at high speeds, and proposing a phase-shift notch filter to ensure stable operations over the entire speed ranges. First, both the frequency characteristics of the simplified notch filter in series and in parallel mode are discussed. The analysis shows that the closed-loop system with a parallel-mode notch filter has a deeper notch depth and faster convergence. The capacities of the synchronous current elimination are also improved at high speeds. Then, an improved phase-shift notch filter connected in parallel with the controller is modeled and analyzed. In order to understand the sensibility of the proposed solution to phase-shift variations, the stability analysis of the closed-loop system in the entire operational speed range is performed using the frequency response method. Experimental results on a high-speed centrifugal air blower test rig show the effectiveness of the proposed solution.

Active Balancing Control of AMB-Rotor Systems Using a Phase-Shift Notch Filter Connected in Parallel Mode

Suppression of imbalance vibration for AMBs controlled driveline system using double-loop structure

In order to suppress the influence of the synchronous vibration generated by the unbalance of magnetically suspended control moment gyro on the attitude control accuracy and stability of the satellite platform, this article first introduces the working principle of the magnetically suspended high-speed rotor system, and also establishes the dynamic model of the magnetically suspended rotor with unbalance mass. At the same time, the main sources of unbalance vibration are also analyzed. Finally, an improved adaptive notch filter based on double input is designed. The filter takes the rotor radial X, Y two-channel displacement sensor signals as inputs, and uses the characteristics orthogonal to each other to simultaneously enter the system. The rotor can be automatically balanced by adjusting the convergence factor and the compensation angle to adaptively suppress the synchronous current in a widely operating speed range. Simulation and experimental results show that the method can effectively eliminate the synchronous current in a widely operating speed range and improve the stability of the system. This research on the microvibration of the rotor is of great significance and application value.

Suppression of Synchronous Current Using Double Input Improved Adaptive Notch Filter Algorithm

The rotor system of magnetically suspended control moment gyro (MSCMG) inevitably has unbalanced amount due to errors in its materials and processing accuracy. The mass unbalance of the rotor will cause the system to generate synchronous vibration and then transmit it to the spacecraft platform through the base, which will seriously affect the imaging quality. The realization of synchronous vibration suppression depends seriously on the rotor speed signal. When the Hall speed sensor has a large measurement error or fails, it is necessary to adaptively estimate the rotor speed to suppress the unbalance vibration of the rotor system. This paper proposes an improved adaptive frequency estimation (IAFE) method. This algorithm uses the characteristics of the rotor radial displacement sensor signal to adaptively estimate the rotor speed, and then suppress the synchronous current generated by the control system. It maintains the stability of the system by changing the phase shift angle at different frequencies, and the residual displacement stiffness force is also compensated. The simulation results show that the proposed method is easy to be implemented, and it can achieve high-precision suppression of unbalanced vibration.

Qi Chen

Papers

Active Balancing Control of AMB-Rotor Systems Using a Phase-Shift Notch Filter Connected in Parallel Mode

Unbalance vibration suppression for AMBs system using adaptive notch filter

Suppression of imbalance vibration for AMBs controlled driveline system using double-loop structure

Suppression of Synchronous Current Using Double Input Improved Adaptive Notch Filter Algorithm

Synchronous Vibration Suppression of Magnetically Suspended Rotor System Using Improved Adaptive Frequency Estimation