Huangqiu Zhu

Structure and control of AC-DC three-degree-of-freedom hybrid magnetic bearing

A novel AC-DC-3-degree-of-freedom hybrid magnetic bearing (AC-DC-3DOF-HMB) is proposed, which is controlled by DC in axial direction and 3-phase power converter in radial directions respectively, and the axial and radial bias magnetic fluxes are provided at the same time with one radial polarized permanent magnet ring. The structure and principle producing magnetic suspension forces are introduced. The flux path is calculated by using equivalent magnetic circuit, the mathematical models of the magnetic suspension forces are deduced, and the control method is proposed. The experimental device of the novel bearing is also presented. Lastly, a practical prototypes parameters are used in simulation and the magnetic path is analyzed by finite element analysis software ANSYS 8.1. The theory analysis and simulation results have shown that this magnetic bearing-incorporates the merits of three-phase AC drive, permanent magnet flux biased and axial-radial combined control. It reduces overall system size and has bigger magnetic suspension force, higher efficiency and lower cost. This novel magnetic bearing has a wide application in super-speed and super-precision numerical control machine tool, bearingless motor, high-speed flywheel, artificial satellite, and so on.

Design and simulation of control system for bearingless synchronous reluctance motor

In this paper, the principle of bearingless synchronous reluctance motors is explained and a mathematic model of control system is deduced. The main problem in the control system is the coupling between the radial force and electromagnetic torque, and between the two radial forces in x- and y-direction. A decoupling method based on the feed-forward compensator is designed to decouple those variables. Proposed control system has been simulated in Matlab/Simulink environment. Simulation results have validated that stable suspension operation and the decoupling can be realized successfully with this method.

Magnetic field analysis of bearingless switched reluctance motor using finite element method

In this paper, the principle of bearingless switched reluctance motor (BSRM) is introduced. Flux distributions and radial force of BSRM are analyzed based on finite element method (FEM). The relation curves about the radial force and the rotor position, the radial force and the current are received. It is shown that these relationships are influenced by the magnetic saturation. And the effective area of radial force is also discussed. The analyzed results are applied to derive more precise radial force model

Design and realization of a digital control system for a 4 kW bearingless permanent magnet slice motor

Bearingless permanent magnet slice motors have a wide range of applications in the area of special electric drives. In this paper, a 3-phase permanent magnet slice motor with the power around 4 kW is set up, and a system of bearingless permanent magnet slice motor is introduced. Theoretical formulas of driving system and radial suspension forces are given, and then the control system for the 3-phase bearingless permanent magnet slice motor is designed and presented. An experimental platform of digital control system with TMS320F240 DSP controller is designed to meet the need, and experiments including speed regulation and suspension force control are performed. The waveforms of the displacements are presented under unload and load. It has shown that the vibration amplitude in x and y direction is less than 500 mum under unload and load, while rotor speed are changed from 0 r/min to 7700 r/min

Bearingless motor's radial suspension force control based on virtual winding current analysis

Decoupling control of torque and suspension force is the key technology to achieve stable operation for bearingless motors. In this paper, after a general introduction of the principle of radial suspension forces for the bearingless permanent magnet synchronous motor (BPMSM), a new analysis method based on virtual winding current is presented. Based on the proposed analysis method, the corresponding theoretical analysis of suspension operation is presented. Meanwhile, the control strategy of stable operation is put forward for the BPMSM. In order to testify the validity of the proposed analysis method, the relevant experiments are designed and conducted. It can be concluded that the experiment results are very close to theoretical analyses based on the proposed method. Moreover, the validity of control strategy can be confirmed, which establishes foundations for further research.

Modeling and digital control system for bearingless permanent magnet synchronous motor based on magnetic energy equation

A bearingless permanent magnet synchronous motor (BPMSM) is a kind of high performance bearingless motor, which has the advantages of both PMSM and magnetic bearings. By analysing the flux linkage intersection between the two sets of stator windings, a new concept of mechanical/electrical coordinate transformation is put forward. According to this method, flux linkage equations of the two sets of stator windings are derived. Then the magnetic energy equation can be gained. After analysing the mathematical formula of various sort radial forces in the BPMSM, a complete mathematics model of radial suspension forces for the BPMSM is obtained. The electromagnetic torque equation of the BPMSM is derived based on the analysis of the role of Lorentz force in the BPMSM. Finally, a control algorithm of the experimental system is given and some test results are discussed. This mathematics model provides a theoretical foundation for modeling of BPMSM, experiment waveform analysis and structure design.

Research of digital control system for single freedom hybrid magnetic bearing in the axial direction

In the paper, a novel axial hybrid magnetic bearing (HMB) has been proposed. Based on configuration and working principle of the hybrid magnetic bearing in axial direction, the principle of producing suspension forces is elaborated; the flux path is calculated by using equivalent magnetic circuit. Adopting a fixed-point digital control processor TMS320LF2407, the hardware of digital control system including A/D and D/A converters is designed. The control program is developed with TMS320LF2407 assembly language. The single freedom axial hybrid magnetic bearing can suspend steadily based on TDS2407EA and the software. The research results have shown that the digital control system based on TMS320LF2407 can meet the requirements of a high-speed magnetic bearing system, and it is very convenient to use other advanced control strategies, too

State feedback decoupling control of AC 5 degrees of freedom hybrid magnetic bearings

The AC 5 degrees of freedom (DOF) hybrid magnetic bearings (HMB) system is a multivariable, nonlinear and strong coupled system, which requires decoupling control to achieve stable operation at a high speed. In this paper, a dynamic decoupling control approach based on state feedback method is developed for the AC-5DOF-HMB system. Firstly, the configuration of the system and the mathematical models of radial and axial suspension forces are introduced and deduced, respectively. Secondly, based on the setting of the state equations of the system, the control law of state feedback is educed by introducing the theory of state feedback decoupling control. Finally, the control system is designed and simulated. The simulation results show that this kind of control strategy can realize dynamic decoupling control among the 5 displacement subsystems for the AC-5DOF-HMB system, and the whole system has good dynamic and static performance.

Optimization Design of Bearingless Permanent-Magnet Slice Motor

The parameter and distribution of air-gap flux density determined by structures and methods of permanent-magnet rotor magnetization have effects on the performance of suspension forces and torque in a bearingless permanent-magnet slice motor (BPMSM) directly. In this paper, different rotor structures and magnetization methods are analyzed for the BPMSM. Based on the finite-element analysis, the optimum length ratio of rotor magnetic yoke dr and lr is calculated in different magnetizations to get the maximum flux density. Then the radial suspension forces with maximum air-gap flux density in different structures and rotor magnetizations are compared for the BPMSM. The simulation and experiment results show that the amplitude and sinusoidal characteristic of air-gap flux density are improved with parallel magnetized ring-shaped rotor. Furthermore, the BPMSM with parallel magnetized ring-shaped rotor is easily controlled and has a good suspension and speed regulation performance.

Design and Optimization of Bearingless Permanent Magnetic Synchronous Motors

The bearingless permanent magnetic synchronous motor (BPMSM) is a new type of special motor that has been receiving extensive attention in recent years. In this paper, a design method based on electromagnetic calculation for BPMSMs is proposed. Main dimensions including the effective length, diameter, and parameters of the permanent magnet and windings can be obtained. Then, to inhibit higher harmonics, two measures are taken. One measure is using short-pitch windings instead of conventional full-pitch windings, and the other measure is adopting a new type of cosine shape of permanent magnets. Finally, the structure and unbalanced flux density distributions of the designed prototype are studied by finite-element analysis, which verify the correctness of the design method, and better optimization results are obtained.