Review of Field Weakening Control Strategies of Permanent Magnet Synchronous Motors

Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the speed range under finite DC-bus voltage,extensive research on field weakening(FW)control strategies has been conducted.This paper summarizes the major FW control strategies of PMSMs,which are categorized into calculation-based methods,voltage closed-loop control methods,and model predictive control related methods.The existing strategies are analyzed and compared according to performance,robustness,and execution difficulty,which can facilitate the implementation of FW control.

DISTRIBUTION OF THE MAGNETIC FIELD AND ITS CONTROLEFFECT ON THE MOLTEN METAL FLOW IN FLOW CONTROLMOLD

A thermo-simulation experimental continuous caster was established to study the effect of two static magnetic fields imposed the whole width of the mold on the molten metal flow. Low melting point Bi-Pb-Sn alloy and silicon oil were adopted to simulate the molten metal and mold powder respectively. The results show that the control effect of electromagnetic fields on the molten metal flow in the different zones of mold is different. Therefore it is important to study and design new types of magnetic fields to satisfy the request of controlling the molten metal flow in the mold.

Influence of Alternating and Static Magnetic Fields on Drug Release from Hybrid Hydrogels Containing Magnetic Nanoparticles

Hybrid hydrogels of carboxymethylcellulose (CMC), containing two different amounts of CoFe2O4 magnetic nanoparticles (50% and 70% in relation to the quantity of the polymer) as crosslinkers, were prepared. The hybrid hydrogels were chemically and morphologically characterized and their viscoelastic properties and swelling degrees were analyzed. The hydrogels were tested as controlled drug delivery systems by applying one static and two different alternating magnetic fields. The application of the two alternating magnetic fields (AMF) to the hybrid hydrogels induced a higher release of methylene blue (MB), used as a model drug, than without the application of any magnetic field, especially at low frequency (4 Hz) and high magnetic intensity (0.5 T). In contrast, when the hybrid hydrogels were exposed to a static magnetic field (SMF) the release of MB was slowed down. Furthermore the two different amounts of magnetic nanoparticles induce different responses to the magnetic field. The greater number of nanoparticles in the CMC-NP-70 hydrogel leads to the formation of some NPs clusters limiting the drug release;conversely, the CMC-NP-50 hydrogel, containing a lower amount of nanoparticles, shows a higher release of MB vs. time. In conclusion, we were able to get a potential system for modulation of the drug delivery: the release behaviour of hybrid hydrogels can be modulated by applying alternating and static magnetic fields cyclically. A possible explanation for the release mechanism is about the structural modification of the polymeric chains that occurs when the hybrid hydrogels are exposed to the magnetic fields.

A novel fuzzy logic direct torque controller for a permanent magnet synchronous motor with a field programmable gate array

A high-performance digital servo system built on the platform of a field programmable gate array (FPGA),a fully digitized hardware design scheme of a direct torque control (DTC) and a low speed permanent magnet synchronous motor (PMSM) is proposed. The DTC strategy of PMSM is described with Verilog hardware description language and is employed on-chip FPGA in accordance with the electronic design automation design methodology. Due to large torque ripples in low speed PMSM,the hysteresis controller in a conventional PMSM DTC was replaced by a fuzzy controller. This FPGA scheme integrates the direct torque controller strategy,the time speed measurement algorithm,the fuzzy regulating technique and the space vector pulse width modulation principle. Experimental results indicate the fuzzy controller can provide a controllable speed at 20 r min-1 and torque at 330 N m with satisfactory dynamic and static performance. Furthermore,the results show that this new control strategy decreases the torque ripple drastically and enhances control performance.

Amorphous magnetic semiconductors with Curie temperatures above room temperature

Recently, amorphous magnetic semiconductors as a new family of magnetic semiconductors have been developed by oxidizing ferromagnetic amorphous metals/alloys. Intriguingly, tuning the relative atomic ratios of Co and Fe in a Co-Fe-Ta-B-O system leads to the formation of an intrinsic magnetic semiconductor. Starting from high Curie-temperature amorphous ferromagnets, these amorphous magnetic semiconductors show Curie temperatures well above room temperature. Among them, one typical example is a p-type Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor, which has an optical bandgap of ~2.4 eV, roomtemperature saturation magnetization of ~433 emu/cm3, and the Curie temperature above 600 K. The amorphous Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor can be integrated with n-type Si to form p-n heterojunctions with a threshold voltage of ~1.6 V, validating its p-type semiconducting character. Furthermore, the demonstration of electric field control of its room-temperature ferromagnetism reflects the interplay between the electricity and ferromagnetism in this material. It is suggested that the carrier density, ferromagnetism and conduction type of an intrinsic magnetic semiconductor are controllable by means of an electric field effect. These findings may pave a new way to realize magnetic semiconductor-based spintronic devices that work at room temperature.

Numerical Study of Axial Magnetic Effects on a Turbulent Thermal Plasma Jet for Nanopowder Production Using 3D Time-Dependent Simulation

3D time-dependent simulations are performed using a computational method suitable for thermal plasma flows to capture a turbulent field induced by a thermal plasma jet and steep gradients in nanopowder distributions. A mathematical model with a simple form is developed to describe effectively simultaneous processes of growth and transport of nanopowder in/around a thermal plasma flow. This growth-transport model obtains the spatial distributions of the number density and mean diameter of nanopowder with a lower computational cost. The results show that an argon thermal plasma jet induces multi-scale vortices even far from itself. A double-layer structure of high-temperature thicker vortex rings surrounded by low-temperature thinner vortex rings is generated in the upstream region. As the vortex rings flow downstream, the high-temperature thicker vortex rings deform largely whereas the low-temperature thinner vortex rings break up?into smaller vortices. Nanopowder is generated at the fringe of plasma and transported widely outside the plasma region. The nanopowder grows up collectively by coagulation decreasing particle number as well as homogeneous nucleation and heterogeneous condensation. When a uniform magnetic field is applied in the axial direction, a longer and straighter thermal plasma jet is obtained because of Lorentz force and Joule heating. Larger nanopowder is produced around the plasma because turbulent diffusions of silicon vapor and nanoparticles by vortices are suppressed as well.

Characteristics of Controlled Bridge Circuit and Its Application in Magnetic Field Induction Measurement

The article designs a new type of bridge circuit with a controlled source—when the resistance on the bridge arm of the controlled source bridge circuit meets the bridge balance condition, and the bridge branch contains only one Current-Controlled Current Source (CCCS), a Voltage-Controlled Current Source (VCCS), a Current-Controlled Voltage Source (CCVS), or a Voltage-Controlled Voltage Source (VCVS), the circuit is called a controlled bridge circuit, which has the characteristics of bridge balance. Due to the relationship between the controlled source and the bridge arm, the sensitivity of the components on the bridge is higher mathematically and logically. When applied to measurement, engineering, automatic control, and other fields, the controlled bridge circuit has higher control ac-curacy. Mathematical derivation and simulation results prove the correctness of the bridge balance conclusion and the special properties of this bridge when applied to the measurement field.

Dynamics of A Rotor Supported on Magnet-Rheological Fluid Squeeze Film Damper

Using special characteristics of magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its viscosity by an external magnetic field, a novel controllable magneto-rheological fluid squeeze film damper is presented in this paper. After analyzing the effects of the MR fluid, the externally applied magnetic flux density and the radial clearance of the damper on the behavior of a flexible rotor supported on the MR fluid squeeze film damper in the non-rotating state, an experimental study is carried out on the controllability and effectiveness of the MR fluid squeeze film damper on the rotor vibration in the rotating state. The existing problems in the MR fluid squeeze film damper, such as unbalanced magnetic pull force, and MR fluid sediment, which may result in the failure of the MR fluid squeeze film damper application, are also discussed. It is shown that not only can the dynamical characteristics of the MR fluid squeeze film damper be controlled by a simple external magnetic field, but also the applied voltage required to dramatically change the dynamic characteristics of the MR fluid squeeze film damper is much lower. The MR fluid squeeze film damper is a very effective way to control the vibration of a rotor system.

Genetic algorithm tuned PI controller on PMSM simplified vector control

A simple control structure in servo system is occasionally needed for simple industrial application which precise and high control performance is not exessively important so that the cost production can be reduced efficiently. Simplified vector control, which has simple control structure, is utilized as the permanent magnet synchronous motor control algorithm and genetic algorithm is used to tune three PI controllers used in simplified vector control. The control performance is obtained from simulation and investigated to verify the feasibility of the algorithm to be applied in the real application. Simulation results show that the speed and torque responses of the system in both continuous time and discrete time can achieve good performances. Furthermore, simplified vector control combined with genetic algorithm has a similar perfofmance with conventional field oriented control algorithm and possible to be realized into the real simple application in the future.

Eddy current effects in a high field dipole

Eddy currents produced by a time-varying magnetic field will introduce time delay and thus affect field quality. This effect leads to drifting of the beam position over time, especially for a compact synchrotron.Simulations and measurements of different dipoles have been performed, to investigate the time delay and field quality. The simulations are conducted using OPERA software. The measurements are conducted using a long coil and Hall sensor. All results show that the magnetic field deviation is up to 0.4% for the dipole with stainless steel endplates. The simulations show that the main sources of eddy current are the field saturation effect and the field component Bz, introduced by the bedstead-type coil. Field correction using a power supply is adopted to reduce the deviation to less than 0.02%.

Torque-based Optimal Acceleration Control for Electric Vehicle

The existing research of the acceleration control mainly focuses on an optimization of the velocity trajectory with respect to a criterion formulation that weights acceleration time and fuel consumption. The minimum-fuel acceleration problem in conventional vehicle has been solved by Pontryagin＇s maximum principle and dynamic programming algorithm, respectively. The acceleration control with minimum energy consumption for battery electric vehicle（EV） has not been reported. In this paper, the permanent magnet synchronous motor（PMSM） is controlled by the field oriented control（FOC） method and the electric drive system for the EV（including the PMSM, the inverter and the battery） is modeled to favor over a detailed consumption map. The analytical algorithm is proposed to analyze the optimal acceleration control and the optimal torque versus speed curve in the acceleration process is obtained. Considering the acceleration time, a penalty function is introduced to realize a fast vehicle speed tracking. The optimal acceleration control is also addressed with dynamic programming（DP）. This method can solve the optimal acceleration problem with precise time constraint, but it consumes a large amount of computation time. The EV used in simulation and experiment is a four-wheel hub motor drive electric vehicle. The simulation and experimental results show that the required battery energy has little difference between the acceleration control solved by analytical algorithm and that solved by DP, and is greatly reduced comparing with the constant pedal opening acceleration. The proposed analytical and DP algorithms can minimize the energy consumption in EV＇s acceleration process and the analytical algorithm is easy to be implemented in real-time control.

Electric field control of deterministic current-induced magnetization switching in a hybrid ferromagnetic/ferroelectric structure

Subject Code:F04 With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.Wang Kaiyou(王开友)from the Institute of Semiconductors,Chinese Academy of Sciences demonstrates all-electric and programmable manipulations of ferromagnetic bits without external

Effect of axial static magnetic field on cleanliness and microstructure in magnetically controlled electroslag remelted bearing steel

The effect of the axial static magnetic field(ASMF)on cleanliness and microstructure in magnetically controlled electroslag remelted GCr15 bearing steel ingots was investigated experimentally.The results show that a magnetically controlled spin-vibration induced by the interaction of the ASMFs and the remelting current exists at the consumable electrode tip,resulting in thinner liquid melt film and smaller droplets.With the increase in magnetic flux density,the optimization effect of ASMFs on electroslag remelting process increases and reaches the peak with a 40 mT ASMF,then decreases.The cleanliness of the ingots was improved,and the count of inclusions larger than 5μm was reduced.The microstructure of the ingots processed with a 40 mT ASMF was significantly refined.The depth of the metallic molten pool was reduced from 45.2 to 17.5 mm with the application of 40 mT ASMF.The tensile strength,impact toughness,and Rockwell hardness of the ingots obtained under the 40 mT ASMF were significantly improved.The mechanisms of the spin-vibration occurring at the electrode tip end were interpreted in detail to elucidate the effect of ASMFs.

Starting Control of Free Piston Stirling Linear Generator System Based on FOC

Aiming at the problem of poor system dynamic performance caused by low parameter matching in the coordinated control of Stirling engine and linear generator in the starting stage control of free piston Stirling linear generator system,a joint control method of free piston Stirling permanent magnet synchronous linear generator system based on field orientation control is proposed,based on the theoretical derivation of the mathematical model of the system and the principle of controller parameters setting,the simulation experiments of the system starting stage under several Stirling engine working conditions are carried out under simulation.The experimental results show that the stability and rapidity of the system are improved,and the dynamic response speed of generator parameters under different working conditions is accelerated,what fully verifies the correctness and effectiveness of the method.It provides an effective way to improve the control performance of the system and stabilize the power generation operation.

Theory of Electromagnetism and Gravity —Modeling Earth as a Rotating Solenoid Coil

Presented in this manuscript are conventional electrical engineering tools to model the earth as a rotating electrical machine. Calculations using known parameters of the earth and measured field data has resulted in new understanding of the earth’s electrical system and gyroscopic rotation. The material makeup of the inner earth is better understood based on derived permeability and permittivity constants. The planet has been modeled as simple coils and then as a parallel impedance circuit which has led to fundamental insight into planetary speed control and RLC combination for Schumann Resonance of 7.83 Hz. Torque and Voltage Constants and the inverse Speed Constant are calculated using three methods and all compare favorably with Newton’s Gravitational Constant. A helical resonator is referenced and Schumann’s Resonant ideal frequency is calculated and compared with others idealism. A new theory of gravity based on particle velocity selector at the poles is postulated. Two equations are presented as the needed links between Faraday’s electromagnetism and Newtonian physics. Acceleration and Deceleration of earth is explained as a centripetal governor. A new equation for planetary attraction and the attraction of atomic matter is theorized. Rotation of the earth’s electrical coil is explained in terms of the Richardson effect. Electric power transfer from the sun to the planets is proposed via Flux Transfer Events. The impact of this evolving science of electromagnetic modeling of planets will be magnified as the theory is proven, and found to be useful for future generations of engineers and scientists who seek to discover our world and other planets.

基于自抗扰的永磁同步电机附加谐波损耗抑制方法

针对永磁同步电机在变频器供电时,由时间电流谐波所引起的附加谐波损耗过大及难以在电机初始设计时被考虑到的问题,采用场路耦合联合仿真模型来计算电机的附加谐波损耗,并以4台现有的表贴式永磁同步电机为例,通过实验验证了场路耦合联合仿真模型的有效性,为电机设计之初附加谐波损耗的选取,以及后续温升的计算提供了前期计算的方法。同时提出一种基于自抗扰技术的附加谐波损耗抑制方法,设计一种适用于永磁同步电机矢量控制的自抗扰控制器,并从理论上验证了自抗扰控制器对于时间电流谐波的抑制作用,以及针对自抗扰控制器参数众多调参困难的问题,给出一种参数整定方案。最后通过引入所设计的自抗扰控制器,对电机的时间电流谐波进行计算和分析,使电机的附加谐波损耗降低了68.1%,为同类型电机的附加谐波损耗抑制提供了一种有效的方法。

基于扰动观测器的五相永磁同步电机开路和短路容错矢量控制

针对反电动势含有3次谐波的五相永磁同步电机(PMSM)开路和短路故障导致转矩脉动大的问题,该文提出一种基于扰动观测器的矢量控制(DOB-FOC)策略。该策略基于降阶正交变换矩阵在同步旋转坐标系上建立PMSM开路故障情况下的基波模型,将3次谐波反电动势、短路电流等作为扰动信号。在此基础上,设计扰动观测器,观测出以上扰动导致的转矩脉动,将其转化为q轴补偿电流前馈到q轴电流指令中,有效地抑制了故障导致的转矩脉动,并且实现了PMSM在开路和短路故障情况下的平稳无扰运行。仿真和实验结果验证了所提容错策略的有效性。

千特斯拉级内爆磁压缩装置初始磁场电源系统研制

初始磁场电源系统用于激励千特斯拉级内爆磁压缩装置的初级线圈产生初始磁场,是内爆磁压缩装置的关键设备。在分析千特斯拉级内爆磁压缩装置初始磁场电源需求和技术难点的基础上,系统设计了核心部件选择方案和主脉冲电路及控制系统结构,研制成功一套输出电压1~40 kV可调、主放电电流脉冲上升沿约60μs、总峰值电流达3.2 MA的初始磁场电源系统,已应用于千特斯拉级内爆磁压缩装置动态试验。

多变运行工况下混合励磁轴向磁场永磁电机自适应模型预测电流控制

针对多变运行工况下混合励磁轴向磁场永磁(hybrid excited axial field permanent magnet,HE-AFPM)电机中电励磁磁场与电枢磁场之间矢量耦合、端部漏磁等导致的电机参数非线性变化问题,该文提出一种混合励磁轴向磁场永磁电机自适应模型预测电流控制方法。详细分析HE-AFPM电机拓扑结构及参数变化特性;引入多矢量模型预测电流控制,理论推导分析HE-AFPM电机参数对控制系统的敏感性。在此基础上,将多矢量预测模型作为自适应控制的可调模型,降低了控制算法的复杂度和控制系统的计算负荷,提高了控制系统响应速度;依据波波夫(Popov)超稳定理论,引入3个不等式稳定判据设计各参数的自适应律,可实现多变运行工况下的HE-AFPM电机磁链、自感、互感等参数的有效识别,提高了控制模型的准确性和电流跟踪性能。最后,通过实验验证所提出的自适应模型预测电流控制的有效性。