To achieve the high-accuracy and high-bandwidth attitude-rate measurement and control integration of spacecraft, a novel method based on a magnetically suspended control and sensitive gyroscope (MSCSG) configuration is proposed in this paper. MSCSGs are employed as both actuators and attitude-rate sensors. First, the structure and principle of a MSCSG is given and its modeling is established. Second, the attitude-rate measurement method based on a four-cross configuration is proposed. The corresponding attitude decoupling control law of spacecraft and the steering law of the MSCSGs have been further designed. Compared with the traditional attitude-rate measurement methods, the proposed one entirely preserves the inertial coupling moment items and cross-coupling moment items in the resolution of attitude rate by making full use of the dynamic information of the configuration. Thus, the measurement precision can be greatly improved, and the traditional tension between the accuracy and bandwidth can be well alleviated. The proposed method also enlarges greatly the attitude control bandwidth by the microgimbal moment, providing a new method for high-frequency vibration suppression. Semiphysical simulation results demonstrate the correctness and superiority of the proposed method.

Attitude-Rate Measurement and Control Integration Using Magnetically Suspended Control and Sensitive Gyroscopes

Radial magnetic bearings (RMBs) are one of the most commonly used magnetic bearings. They are used widely in the field of ultra-high speed and ultra-precise numerical control machine tools, bearingless motors, high speed flywheels, artificial heart pumps, and molecular pumps, and they are being strengthened and extended in various important areas. In this paper, a comprehensive overview is given of different bearing topologies of RMBs with different stator poles that differ in their construction, the driving mode of electromagnets, power consumption, cost, magnetic circuits, and symmetry. RMBs with different poles and couplings between the two bearing axes in the radial direction responsible for cross-coupling generation are compared. In addition, different shaped rotors are compared, as the performances of magnetic bearing-rotor systems are of great concern to rotor constructions. Furthermore, the parameter design methods, the mathematical models and control strategies of the RMBs are described in detail. From the comparison of topologies, models and control methods for RMBs, the advantages, disadvantages and utilizable perspectives are also analyzed. Moreover, several possible development trends of the RMBs are discussed.

Radial magnetic bearings: An overview

For space application, weight and power consumption are the key parameters of an actuator for attitude control of spacecraft. In this paper, weight-reduction design based on a novel combined radial-axial magnetic bearing (CRAMB) in a large-scale magnetically suspended control moment gyro (MSCMG) for space station application is proposed. The CRAMB consists of a radial magnetic bearing (RMB) unit and an axial magnetic bearing (AMB) unit. Two CRAMBs can control the 5-degrees of freedom of the high-speed magnetically suspended rotor. According to the requirement of a large MSCMG for a space station, the CRAMB with permanent magnet bias is modeled (based on an equivalent magnetic circuit method), designed, and tested. Compared with the original magnetic bearings in MSCMG fabricated, the number of magnetic pole is reduced from eight to four for RMB unit based on the CRAMB, the weight of magnetic bearings can be reduced from 35.4 to 30.8 kg (reduced by 4.6 kg), and the volume is reduced from $\text{0.00456}$ to $\text{0.00394}\; \text{m}^{3}$ (reduced by 16.3%), when the MSCMG outputs the same angular momentum of 1200 N · m · s and the same torque of 209 N·m. The maximum power consumption of the proposed CRAMB system is decreased by 15.6%.

Weight-Reduction Design Based on Integrated Radial-Axial Magnetic Bearing of a Large-Scale MSCMG for Space Station Application

Disturbance rejection based on iterative learning control with extended state observer for a four-degree-of-freedom hybrid magnetic bearing system

Research and applications of active bearings: A state-of-the-art review

The 3-degrees of freedom magnetic bearing (3-DOF MB) with permanent-magnet (PM) biased has been applied to high-speed motor progressively for their advantages of small thrust disk, low wind friction loss, and small volume. To predict performance and guide design of the 3-DOF MB, an accurate analytical model including eddy-current effects and leakage effects is proposed. Both the solid and the laminated cores are applied in the 3-DOF MB, and therefore the eddy-current effects in different core materials are modeled separately. The frequency response characteristics of axial and radial stiffnesses are calculated according to the proposed model. The analytical results show that the eddy currents induced due to the changing currents will result in considerable magnitude decrease and phase lag of stiffnesses. The influences of leakage effects on the static and dynamic stiffnesses are also discussed. Furthermore, the leakage coefficients are influenced by the eddy-current effects will further decrease the dynamic stiffnesses. The stiffnesses are also investigated by the static and transient finite-element methods (FEMs). Finally, a prototype is designed and fabricated. The FEM results and experimental results demonstrate the validity of the analysis.

Modeling and Design of 3-DOF Magnetic Bearing for High-Speed Motor Including Eddy-Current Effects and Leakage Effects

In this paper, a novel structure of four degrees of freedom (4-DOF) hybrid magnetic bearing is proposed for double gimbal magnetically suspended control momentum gyro (DGMSCMG). It includes two active parts and one passive part, and every active part has eight stator magnetic poles around the circumference in X and Y directions, which are divided into upper and lower layers. The passive part has two whole magnetic rings, which is located in the middle of this 4-DOF hybrid magnetic bearing. The radial active force is analyzed by equivalent magnetic circuit method (EMCM) and the axial resilience force is analyzed by the infinitesimal method based on the end magnetic flux. Meanwhile, three-dimensional finite-element model of the 4-DOF hybrid magnetic bearing is established with ANSYS software, and the radial displacement versus radial force, the current versus radial force, and the axial displacement versus axial resilience force characteristics are analyzed compared with the EMCM. Furthermore, the 10 Nms DGMSCMG prototype with the proposed 4-DOF hybrid magnetic bearing is manufactured, and the experiments of the radial active force test and the axial resilience force test are carried out. Experimental results show that the presented 4-DOF hybrid magnetic bearing has good force performance and verify the correctness of the theoretical analysis.

A Novel 4-DOF Hybrid Magnetic Bearing for DGMSCMG

This article presents a hybrid optimal design of biplanar coils, which produce uniform fields and field gradients. It treats the coil design issue as a nonlinear programming problem, and seeks the best performance via the optimal algorithm. The target field method is first utilized to obtain the initial coefficients and ranges of searching areas in stream functions. Then, the magnetic field relative error is defined as the fitness function for minimization, and the particle swarm optimization algorithm is adopted to optimize the aforementioned coefficients. It not only overcomes the dependence on the position distribution of target field points, but also reduces the required computational dimensions without affecting the pursuit of the ultimate performance. Comparing this work with the traditional target field method, the field inhomogeneity error in the region of interest is reduced from 6.55% to 0.95% ( $B_x$ coil), 12.02% to 0.35% ( $B_z$ coil), 16.54% to 0.57% ( $\mathrm{d}B_x/\mathrm{d}z$ coil), and 11.8% to 0.28% ( $\mathrm{d}B_z/\mathrm{d}z$ coil). Numerical simulation and experimental results show the validity and significance of the proposed method. It has great improvements in both uniform fields and field gradients, which is beneficial to the perfect realization of nulling undesired magnetic fields.

Hybrid Optimal Design of Biplanar Coils With Uniform Magnetic Field or Field Gradient

In this study, a combined radial–axial hybrid magnetic bearing (CRAHMB) with four poles is designed for high-speed brushless DC motor. Owing to the small distance of radial and axial unit of CRAHMB, the magnetic flux leakage (MFL) in both radial and axial directions is complex and serious. This study focuses on effective analytical model and optimisation of CRAHMB including flux leakage of permanent magnet circuit and control electromagnetic circuit. MFL analytical model was built based on equivalent magnetic circuit method. Under the condition of satisfying the maximum bearing capacity, the MFL coefficients were optimised with sequence quadratic programming method. A set of optimum parameters were suggested. MFL before and after optimisation are compared by finite element method. Finally, current stiffness calculated with optimised analytical model was verified on a DC motor experiment. The result shows the accuracies of both the axial and radial current stiffness are enhanced.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-epa.2016.0259

Yun Le

Papers

Modeling and Design of 3-DOF Magnetic Bearing for High-Speed Motor Including Eddy-Current Effects and Leakage Effects

A Novel 4-DOF Hybrid Magnetic Bearing for DGMSCMG

Hybrid Optimal Design of Biplanar Coils With Uniform Magnetic Field or Field Gradient

Magnetic flux leakage modelling and optimisation of a CRAHMB for DC motor

Loss optimization and thermal analysis of a heteropolar magnetic bearing for a vacuum turbo-molecular pump