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To achieve high-precision position control for the active magnetic bearing high-speed flywheel rotor system (AMB-HFRS), a novel control strategy based on inverse system method and extended two-degree-of-freedom (2-DOF) proportional–integral–derivative (PID) controller is proposed in this study. First, the inverse system method is employed to decouple the AMB flywheel rotor system with strong non-linear and coupling, into four independent subsystems. Subsequently, extended 2-DOF PID controllers are used to regulate the decoupled subsystems, to obtain good performances of disturbance rejection and tracking simultaneously. In the extended 2-DOF PID controller, a differential signal is produced by a velocity observer to improve the ability of against noise. Finally, the characteristics of stability, tracking, disturbance rejection and robustness of the control strategy proposed are analysed in theory, and its ability and effectiveness to control the radial position of the AMB-HFRS are further studied by simulations and experiments. It is shown that the control strategy proposed can keep the AMB-HFRS suspending stably from static state to the speed of 24,000 rpm, has the advantages of good tracking, high disturbance rejection, strong robustness and good ability of against noise.

To eliminate the influence of gyroscopic effect on system stability and to improve the control performances for the active magnetic bearing (AMB) high-speed flywheel rotor system, a novel control strategy based on the modal separation and inverse system method is proposed. The translational motions and rotational motions of the AMB flywheel rotor system are firstly decoupled by the modal separation, then the rotational motions are decoupled by the inverse system method, so that the AMB flywheel rotor system, which is a multivariable and strong coupled system, is decoupled into four subsystems. Finally, the subsystems are regulated by four two-degrees-of-freedom (2-DOF) internal model controllers, respectively. Furthermore, the stability, tracking and robustness of the novel control strategy are analysed theoretically, and its effectiveness on vibration control of the AMB high-speed flywheel rotor system is further investigated by simulations and experiments. The results show that the novel control strategy can achieve stable suspension and effectively suppress the vibration of the AMB high-speed flywheel rotor system from static state to 24,000 rpm, with the advantages of high stability, strong robustness, and good performances of tracking and disturbance rejection simultaneously.

This paper presents a twelve-pole heteropolar radial hybrid magnetic bearing (HRHMB) structure. Firstly, the structure and equivalent magnetic circuit (EMC) are designed. And the radial electromagnetic force characteristics are calculated by the EMC model. At the same time, the rationality of EMC model is verified by the finite-element method (FEM) of Magnet software. Then, the 2-D model of the twelve-pole HRHMB is established in Magnet software. The flux density variations of twelve-pole HRHMB and eight-pole HRHMB under different currents are compared by using the FEM. Finally, a method of Magnet-Simulink cosimulation is proposed to analyze the suspension characteristics of the twelve-pole HRHMB and compared with the eight-pole HRHMB. Thus, the effective combination of theoretical analysis, FEM analysis, and Magnet-Simulink cosimulation analysis is realized in the design of HRHMB. The results of Magnet-Simulink cosimulation show that the twelve-pole HRHMB has the advantages of low power consumption, small coupling, large construction dynamic stiffness, and better suspension characteristics than the eight-pole HRHMB.

This study is concerned with the unified analytical solution of rotor strength for the segmented permanent magnet (PM) rotor retained by the carbon-fibre sleeve and non-magnetic alloy sleeve in high-speed surface-mounted permanent magnet synchronous machine. Considering the influence of different densities and coefficients of thermal expansion of PMs and pole fillers on rotor stress, the analytical solution for rotor strength was proposed based on displacement method and stress potential method in polar coordinate. The proposed analytical solution was validated by the finite-element method (FEM) and experiment, respectively, and the influences of rotational speed, retaining sleeve thickness and interference fit between the retaining sleeve and PMs on rotor strength were further investigated based on the analytical solution proposed. It is shown that the results calculated by the proposed analytical solution and the FEM are in good agreement with each other, and the analytical solution can accurately predict the stress distributions of the segmented PM rotor retained by the carbon-fibre sleeve and non-magnetic alloy sleeve. The difference in density and coefficient of thermal expansion between PM and pole filler, rotational speed and operating temperature have great effects on rotor strength.

How to improve the reliability has been a challenging task for transient protection, which has been affected seriously by the fault initial angle (FIA) and transient resistance (TR). Based on support vector machine (SVM), a novel smart transient protection method is presented in this study, which protects a bus and two transmission lines connected to the bus. The method is based on the measurements from the two close-in ends of the two lines. Hilbert–Huang transform is used to extracting instantaneous amplitude from the measured currents. The fault area is determined from the two instantaneous amplitude-integral (IA) of the transient fault currents, the difference of the two IAs, FIA, and the TR. SVM is utilised to determine the fault area. Two IAIs, difference of IAs, FIA and TR are treated as the input to SVMs. Faults with different FIA and TR are treated as a different class of fault, respectively. Correspondingly, a different criterion of discrimination is automatically employed by SVMs for a different fault class. The influence of FIA and TR is eliminated significantly, and the reliability of protection is enhanced substantially. The performance of the method is tested using ATP/EMTP with satisfactory results.

In this paper proposes a new digital monitoring method, which is aimed at the problems of low accuracy and poor stability of current arc welding inverter power parameters. The sensor based on the principle of zero flux modulation can effectively overcome the measurement error and realize the electrical isolation between the main output and the control circuit, which improves the collecting and measuring accuracy of the electrical signal. Meanwhile, the Ethernet communication technology is applied to the data transmission with high transmission rate and reliability, which is the core of the monitoring system of the arc welding inverter power. The applied results show that the monitoring system can digitally collect and display the electrical parameters during the experiment of the dual-pulse metal inert-gas welding(MIG). Moreover, the measurement accuracy is high and has good stability performance.

Because of the nonlinear, uncertainty, open-loop instability and other characteristics of the magnetic control system, the magnetic levitation ball system is taken as the research object, and the mathematical model of the magnetic levitation ball system is established in this paper as well. Phase lead correction controller is designed based on Matlab/Simulink. The simulation model was carried out and a levitation experiment was carried out on GML2001 magnetic levitation ball test bench. The simulation and experimental results show that the designed controller can make the dynamic performance index of the system reach the expected setting. The parameters are easy to determine and the control system is simple to implement.