Thrust Active Magnetic Bearing Research Articles

Modeling of active magnetic bearing in rotating payload satellite considering shaft motion coupling

This paper establishes the refined dynamic model of the five degree-of-freedom active magnetic bearing used in the earth-oriented satellite system with an unbalanced rotating payload based on the more refined air gap change model for stator motion. The disturbance effects of the thrust active magnetic bearing and the coupling effects of shaft motion are analyzed by the equivalent stiffness and damping model, especially when the satellite system is in the fine pointing phase. Numerical simulation results are provided to verify the accuracy of the proposed simplified stiffness and damping model, the disturbance term effects on active magnetic bearing, and the significance of the refined magnetic bearing dynamic model for improving the payload working ability in the fine pointing phase.

Design, Modeling, Fabrication, Back-to-Back Test of a Magnetic Bearing System for High-Speed BLDCM Application

This paper describes in detail the design, construction, and testing of an active magnetic bearing (AMB) system for high-speed permanent magnet (PM) brushless DC motor (BLDCM) application. A back-to-back (BTB) test setup which consists of two BLDCMs connected by a high-speed flexible coupling is designed and built: the first one acts as the motor and the other one acts as the generator with resistive load. The dynamic model of the rigid rotor supported by AMBs, and its electromagnetic and feedback control design aspects are also provided. Mechanical design aspects are rotor assembly, radial AMB (RAMB), and thrust AMB (TAMB). Finally, full-loaded test results of the AMBs are given using the BTB experimental test setup that adopts two 100 kW electric machines supported by AMBs.

Experimental Evaluation of a Surge Controller for an AMB Supported Compressor in the Presence of Piping Acoustics

This brief studies the active control of compressor surge using the thrust active magnetic bearing (AMB) in centrifugal compressors and it presents experimental test data to demonstrate the effectiveness of the control solution in industrial size equipment. A detailed step-by-step description is provided from the derivation of the surge model, to the implementation and experimental testing of the surge controller. To accurately represent the configurations found in industrial systems, the proposed surge suppression method is implemented integrally using common off-the-shelf components. During the design of the surge controller, special attention is paid to a possible conflict between the surge controller and the AMB's internal rotor levitation controller. Observations from the experimental surge testing demonstrate that the presented method is able to stabilize the compression system when operating in the unstable surge region, extending the stable flow range by over 21%. In practice, this allows the compressor to operate at the peak pressure/efficiency point, while maintaining a healthy surge margin as commonly prescribed in industrial compressors.

Decentralized PID neural network control for five degree-of-freedom active magneticbearing

A decentralized proportional–integral–derivative neural network (PIDNN) control scheme is proposed to regulate and stabilize a fully suspended five degree-of-freedom (DOF) active magnetic bearing (AMB) system which is composed of two radial AMBs (RAMBs) and one thrust AMB (TAMB). First, the structure and operating principles of the five-DOF AMB system are introduced. Then, the adopted differential driving mode (DDM) for the drive system of the AMB is analyzed. Moreover, due to the exact dynamic model of the five-DOF AMB system is vague, a decentralized PIDNN controller is proposed to control the five-axes of the rotor simultaneously in order to confront the uncertainties including inherent nonlinearities and external disturbances effectively. Furthermore, the connective weights of the PIDNN are trained on-line and the convergence analysis of the regulating error is provided using a discrete-type Lyapunov function. Based on the decentralized concepts, the computational burden is reduced and the controller design is simplified. Finally, the experimental results show that the proposed control scheme provides good control performances and robustness for controlling the fully suspended five-DOF AMB system in different operating conditions.

Robust Nonsingular Terminal Sliding-Mode Control for Nonlinear Magnetic Bearing System

This study presents a robust nonsingular terminal sliding-mode control (RNTSMC) system to achieve finite time tracking control (FTTC) for the rotor position in the axial direction of a nonlinear thrust active magnetic bearing (TAMB) system. Compared with conventional sliding-mode control (SMC) with linear sliding surface, terminal sliding-mode control (TSMC) with nonlinear terminal sliding surface provides faster, finite time convergence, and higher control precision. In this study, first, the operating principles and dynamic model of the TAMB system using a linearized electromagnetic force model are introduced. Then, the TSMC system is designed for the TAMB to achieve FTTC. Moreover, in order to overcome the singularity problem of the TSMC, a nonsingular terminal sliding-mode control (NTSMC) system is proposed. Furthermore, since the control characteristics of the TAMB are highly nonlinear and time-varying, the RNTSMC system with a recurrent Hermite neural network (RHNN) uncertainty estimator is proposed to improve the control performance and increase the robustness of the TAMB control system. Using the proposed RNTSMC system, the bound of the lumped uncertainty of the TAMB is not required to be known in advance. Finally, some experimental results for the tracking of various reference trajectories demonstrate the validity of the proposed RNTSMC for practical TAMB applications.

Adaptive complementary sliding-mode control for thrust active magnetic bearing system

An adaptive complementary sliding-mode control (ACSMC) system with a multi-input-multi-output (MIMO) recurrent Hermite neural network (RHNN) estimator is proposed to control the position of the rotor in the axial direction of a thrust active magnetic bearing (TAMB) system for the tracking of various reference trajectories in this study. First, the operating principles and dynamic model of the TAMB system using a linearized electromagnetic force model is derived. Then, a conventional sliding-mode control (SMC) system is designed for the tracking of various reference trajectories. Moreover, a complementary sliding-mode control (CSMC) system is adopted to reduce the guaranteed ultimate bound of the tracking error by half while using the saturation function as compared with the SMC. Furthermore, since the system parameters and the external disturbance are highly nonlinear and time-varying, the ACSMC is proposed to further improve the control performance and increase the robustness of the TAMB system. In the ACSMC, the MIMO RHNN estimator with estimation laws is proposed to estimate two complicated dynamic functions of the system on-line. In addition, a robust compensator is proposed to confront the minimum approximated errors and achieve the robustness. Finally, some experimental results for the tracking of various reference trajectories show that the control performance of the ACSMC is significantly improved comparing with the SMC and CSMC.

Tracking control of thrust active magnetic bearing system via Hermite polynomial-based recurrent neural network

A Hermite polynomial-based recurrent neural network (HPBRNN) is proposed to control the rotor position on the axial direction of a thrust active magnetic bearing (TAMB) system for the tracking of various reference trajectories in this study. First, the operating principles and dynamic model of the TAMB system using the non-linear electromagnetic force model is derived. Then, the HPBRNN is developed for the TAMB system with enhanced control performance and robustness. In the proposed HPBRNN, each hidden neuron employs a different orthonormal Hermite polynomial basis function (OHPBF) as an activation function. Therefore the learning ability of the HPBRNN is effective with high convergence precision and fast convergence time. Moreover, the connective weights of the HPBRNN using the supervised gradient descent method are updated online and the convergence analysis of the tracking error using the discrete-type Lyapunov function is provided. Finally, some experimental results of various reference trajectories tracking show that the control performance of the HPBRNN is significantly improved compared to the conventional proportional-integral-derivative and recurrent neural network controllers and demonstrate the validity of the proposed HPBRNN for practical applications.

Design and analysis of thrust active magnetic bearing

This paper deals with the design and analysis of thrust active magnetic bearing (AMB). Using the analytical solutions for thrust, resistance, and inductance obtained from equivalent magnetic circuits method, we determine initial design parameters such as the size of magnetic circuit, coil diameter, and the number of turns by investigating the variation of thrust according to design parameters. Then, using nonlinear finite element analysis, a detailed design considering saturation is performed in order to meet required thrust under restricted conditions. Finally, by confirming that the design result is shown in good agreement with experimental results, the validity of design procedures for thrust AMB used in this paper is proved. In particular, the dynamic test results of the thrust AMB are also given to confirm the validity of the design.

Effect of Thrust Magnetic Bearing on Stability and Bifurcation of a Flexible Rotor Active Magnetic Bearing System

This paper is concerned with the effect of a thrust active magnetic bearing (TAMB) on the stability and bifurcation of an active magnetic bearing rotor system (AMBRS). The shaft is flexible and modeled by using the finite element method that can take the effects of inertia and shear into consideration. The model is reduced by a component mode synthesis method, which can conveniently account for nonlinear magnetic forces and moments of the bearing. Then the system equations are obtained by combining the equations of the reduced mechanical system and the equations of the decentralized PID controllers. This study focuses on the influence of nonlinearities on the stability and bifurcation of T periodic motion of the AMBRS subjected to the influences of both journal and thrust active magnetic bearings and mass eccentricity simultaneously. In the stability analysis, only periodic motion is investigated. The periodic motions and their stability margins are obtained by using shooting method and path-following technique. The local stability and bifurcation behaviors of periodic motions are obtained by using Floquet theory. The results indicate that the TAMB and mass eccentricity have great influence on nonlinear stability and bifurcation of the T periodic motion of system, cause the spillover of system nonlinear dynamics and degradation of stability and bifurcation of T periodic motion. Therefore, sufficient attention should be paid to these factors in the analysis and design of a flexible rotor system equipped with both journal and thrust magnetic bearings in order to ensure system reliability.

Stability and bifurcation of a rigid rotor-magnetic bearing system equipped with a thrust magnetic bearing

This paper is concerned with the stability and bifurcation of a rigid rotor support by journal and thrust active magnetic bearing (TAMB). The system is modelled as a five-axis controlled active magnetic bearing-rotor system (AMBRS), and the system equations are formulated by combining the equations of motion of the rotor and the equations of the decentralized proportional-integral-derivative controllers. For this AMBRS, the magnetic forces of the journal and TAMB are strongly non-linear with respect to control current and shaft displacement. This study focuses on the influence of non-linearities on the stability and bifurcation of T periodic motion of the AMBRS subjected to the influence of TAMB and mass eccentricity. In the stability analysis, only periodic motion is investigated. The periodic motions and their stability margin are obtained by shooting method and path-following technique. The local stability and bifurcation behaviours of periodic motions are obtained by the Floquet theory. The results indicate that TAMB and mass eccentricity have great influence on non-linear stability and bifurcation of the T periodic motion of the system and cause the spill-over of system non-linear dynamics and degradation of stability and bifurcation of T periodic motion. Therefore, sufficient attention should be paid to these factors in the analysis and design of rigid rotor systems equipped with TAMBs in order to ensure system reliability.

Rotor dynamic coefficients of a thrust active magnetic bearing considering runner tilt

This paper investigates the rotor dynamic coefficients of a thrust active magnetic bearing when runner tilt is taken into account. The influence of runner tilt upon the load capacity and the dynamic forces and moments of a thrust active magnetic bearing is analysed. A total of 24 rotor dynamic coefficients are defined to describe the dynamic behaviour of the thrust active magnetic bearing. A general method is presented to calculate these coefficients, which can be used conveniently for the coupled dynamic analysis when a rotor is supported by both radial and thrust magnetic bearings.