Comparison of combined versus separate lift/propulsion systems

The notion of using the magnetic attractive force of a single-sided linear induction motor (SLIM) for suspension of a vehicle has recently received some attention. There is, therefore, some interest in determining how such a combined suspension/propulsion system would compare to separate lift and propulsion. Weight requirements of transverse flux dc lift magnets are calculated as a function of vehicle weight and magnet length. A three-phase longitudinal flux linear motor/suspension system is designed which has the same values of maximum flux and current density as the dc magnet. The effect of pole pitch on the weight of this motor is shown. Comparisons are made between this combined system and a system using the dc magnets plus a separate linear motor.     

槽楔材料对PMLSM电磁特性的影响

为提高PMLSM的电磁性能并降低齿槽力和推力波动,文中提出一种在直线电机槽口安装槽楔的解决方案。槽楔材料对电机性能影响较大,为了使电磁性能最佳,文中以分数槽永磁直线同步电机为研究对象,分析了槽楔材料为硬磁、软磁和非磁时对电机气隙系数的影响。利用有限元法对比分析了3种槽楔材料下电机的气隙磁场、反电动势、齿槽力和推力波动等电磁性能,并对不同负载下削弱推力波动的程度进行对比。分析结果表明,硬磁性材料可以有效降低齿槽力和推力波动。最后研究了不同相对磁导率下硬磁性材料对电机性能的影响,并得到电机性能最佳时的相对磁导率值,为进一步提高电机性能提供了理论基础。     

Baseline specifications for a magnetically suspended high-speed vehicle

Baseline specifications for a magnetically suspended vehicle capable of 300 mi/h (483 km/h) operation are given. The magnetic forces (lift, drag, and lateral) on a superconducting coil moving over an aluminum guideway are shown. The basic features of the associated cryogenics are presented along with a discussion of the cryogenic refrigeration requirements. Vehicle dynamics and the resultant ride quality over roadbeds of various roughnesses are analyzed. Thrust requirements for the propulsion system are specified, and both the linear induction motor and the linear synchronous motor are considered. Several guideway configurations are suggested and the significant properties of each are noted.     

基于微分几何的永磁直线同步电机非线性控制方法研究

为了实现永磁直线同步电机在垂直升降系统运行过程中的良好控制性能,从电机学原理出发,分析了永磁直线同步电机的数学模型,提出了一种微分几何非线性最优控制的方法。通过状态反馈精确线性化把直线电动机的非线性系统转换为线性系统,并在此基础上应用非线性最优控制理论设计控制器。最后,通过MATLAB对控制系统进行仿真,仿真结果验证了此控制方法提高了系统的运动性能,增强了系统对参数摄动和外在扰动的鲁棒性。     

Design and analysis of a novel wound rotor for a bearingless induction motor

The traditional squirrel-type bearingless induction motor (BIM) suspension winding generates induced current in its squirrel-cage rotor and affects the phase and amplitude of the suspension force. Based on the analysis of the spatial distribution of torque winding magnetic field and suspension winding magnetic field, a new type of wound rotor BIM is designed. Different from the squirrel-cage rotor, the wound rotor uses a special method of embedding a set of coils at any symmetrical four rotor slot positions, so as to only induce the torque winding magnetic field. The induced current, air-gap magnetic density, magnetic field line distribution, suspension force as well as electromagnetic torque of the traditional squirrel-cage motor and the new wound motor are analysed by Maxwell finite element calculation. The results show that the designed new wound BIM can not only effectively suppress the induced current of suspension winding, eliminating its influence on the suspension force, but also has a better starting performance.     

Design principles for magnetic levitation

General relations and limitations pertinent to the design of an inductive magnetic suspension system are derived. It is shown that in order to reduce magnetic drag we must increase the vehicle field and decrease the guideway currents. But this then produces a stiff suspension unless we are willing to increase guideway cost. Reasonable and consistent design objectives are shown to be: vehicle natural frequency for heave≃1 Hz without secondary suspension; suspension power lossessime;10 kW/ton (L/D=120 at 270 mi/h); aluminum requirements≃80 kg/m for a dual guideway. It was shown to be theoretically possible to operate at arbitrarily low speeds by using either a superconducting guideway or a feedback control system for short distances near terminals. Between terminals the guideway might resemble a parallel-wire transmission line with a thin conducting sheet between the wires. The design of an active-guideway linear synchronous motor is discussed and shown to be capable of supplying 5 MW of power at efficiencies of about 85 percent and a power factor of 0.5. For a dual guideway the armature windings require about 40 kg/m of aluminum, but no steel. The total cost of the maglev portion of a 120 m/s (268 mi/h) high-speed ground transportation system is estimated to be about 1 million dollars/km, with at least half of this related to propulsion and power distribution and control. If speed is reduced to 90 m/s (202 mi/h), substantial economies are possible.     

基于有限元分析的直流电机控制策略

无轴承无刷直流电机集成了直流和交流电机的优点,具有重要的实际应用价值,针对传统悬浮力控制方法存在工作复杂、逆变器通断频繁等缺陷,为了提高磁悬浮力的控制效果,提出了基于有限元分析的无轴承无刷直流电机悬浮力控制策略。首先对无轴承无刷直流电机的结构以及悬浮力产生的原理进行了分析,然后采用有限元分析法对电机转矩和悬浮力进行计算,从而实现无轴承无刷直流电机控制,最后采用Matlab/Simulink工具对其性能进行测试与验证。结果表明,本文策略可以提高转子悬浮的稳定性,能够保证无轴承无刷直流电机的正常运行。     

Modeling of a permanent magnet linear synchronous motor using magnetic equivalent circuits

This paper presents a modeling framework for permanent magnet linear synchronous motors based on magnetic equivalent circuits. In comparison to the commonly used dq0 model, the proposed modeling approach is able to systematically include magnetic saturation effects and has no restriction to harmonic motor quantities. In contrast to existing work, a differential magnetic equivalent circuit network is used to describe the stator quantities and the complete model is derived using a graph-theoretic approach. Furthermore, the resulting model is calibrated with measurements on a test bench and validated with additional measurement scenarios.     

Development of a totally active magnetically suspended gyro

A magnetically suspended gyro (MSG) is developed and its performances is estimated. In the MSG, a disk-type rotor is connected to a synchronous motor through a fluid bearing and the motor is fixed to the frame of the floator. The floator is suspended by magnetic force without any mechanical contact so that highly accurate measurement is possible. In accordance with this concept, a three-degrees-of-freedom (DOF) active MSG was developed. However, because of poor damping in the passive suspension and the low resolution of the displacement sensors, the measurement accuracy was relatively low. To solve these problems, a six-DOF (totally) active MSG is designed and fabricated. The frame of this gyro is an octagonal. The motion of the frame is controlled by eight electromagnets. The performance of the gyro is evaluated through measurement of the double-axis angular velocity. The advantages of totally active suspension are investigated. Sufficient damping rapidly reduces the influence of disturbances. Then, the influence of sensor noise is examined. The results of this examination show that the accuracy of the angular velocity measurement is improved by using highly sensitive displacement sensors. Next, the dynamic range is measured. This experiment shows that the MSG can provide precise angular velocity measurement in a low-frequency region.     

图解分析法讲解无轴承电机磁悬浮控制原理

在回顾电机中的洛伦兹力和麦克斯韦力基础上,本文通过理论解析介绍了无轴承电机产生稳定径向悬浮力的基本条件。笔者以二极悬浮控制四极无轴承电机为例,针对几个典型时刻产生出的径向磁悬浮力,对无轴承电机磁悬浮控制原理进行了图解分析。教学实践表明,采用本文解析推导和图解分析相结合的讲解方法,便于快速且深入地理解掌握无轴承电机这种新型电机的基本工作原理。     

Torque-ripple reduction in PM synchronous motor drives using repetitive current control

The paper deals with the torque-ripple reduction in a permanent magnet synchronous motor (PMSM) drive with distorted back electromotive force. A smooth torque is obtained by tracking a modified current reference which is periodic over one-sixth of the electrical time period in the synchronous reference frame. An accurate tracking involves, however, very high current loop bandwidth, which is usually not achievable with conventional linear controllers. In order to improve current tracking in the presence of periodic reference signals and disturbances, the paper proposes the application of repetitive techniques to the current control in a field-oriented PMSM drive, where the q-axis current reference has been modified to achieve constant torque. The paper investigates the advantages and pitfalls of the method, through a mathematical analysis and an experimental validation obtained on a laboratory prototype. Particular emphasis is placed on the adjustments that have been specifically studied to enhance the overall system performance.     

Smooth section crossing of controlled-repulsive PM LSM vehicle by DTC method based on new concept of fictitious section

This paper presents propulsion control for the permanent-magnet linear synchronous motor vehicle Marine-Express 03 (ME03) to pass through the two sections in the mass-reduced mode by a new direct torque control (DTC) method. A fictitious section is introduced for pass-through-section control. It has been done by introducing a fictitious section defined by "one section including section boundary." The lift and thrust forces for the pass-through section are obtained by the DTC method based on voltage equations per one fictitious section. The vehicle ME03 has been controlled successfully to pass through the two sections in the mass-reduced mode by experiment.     

A magnetically levitated, automated, contact analytical probe tool

With the challenge of the shrinking dimensions in the fabrication process, demands are growing for higher precision and more powerful analytical probing stations to be used for characterization and failure analysis of integrated circuits. A magnetic levitation-based approach to analytical probing stations is proposed and investigated in this paper. This approach permits the process to be automated while maintaining better resolution and easier operation than is currently available. Further, force control can be implemented to ensure that the probe contact does not scratch the device under testing. Feedback controllers are designed and used in both the suspension and the XY positioning. The suspension motion controller is implemented in analog circuitry while the XY motion controller is implemented in a digital controller. An air gap sensor and optical position sensors are used for the position feedback. A simple open loop control method is derived for the force control. A positioning repeatability of 0.2 μm and a force repeatability of 80 mgf are observed from the experimental results     

Design of a linear bulk superconductor magnet synchronous motor for electromagnetic aircraft launch systems

High-temperature superconducting (HTS) material in bulk form is used to design a linear synchronous motor for an electromagnetic aircraft launch system. The motor is designed without an iron core. Stator coils are placed in the air while the permanent magnets used in conventional design of linear permanent magnet synchronous motors are replaced by the HTS bulk magnets. The physical, operational, and equivalent circuit parameters of the linear motor with HTS bulk magnets are compared with those of a linear permanent magnet synchronous motor and linear induction motor designed for the same application. Results show that utilizing superconducting magnets is only superior at temperatures below 40 K.     

A Novel MagPipe Pipeline Transportation System Using Linear Motor Drives

A novel capsule pipeline transportation system using linear motor drives, called Magplane MagPipe, is under development with the intention to replace trucks and railways for hauling materials from the mine to the rail head, power plant, or processing plant with reduced operating cost and energy consumption. The initial demonstration of a MagPipe line in Inner Mongolia will be a 500-m-long double-pipe coal transport system with the design transportation capacity of 3 Mega-Mg per year. The pipeline consists of 6-m-long plastic pipe modules with an I-beam suspension system inside the pipe to carry sets of five coupled capsules. The pipe will also contain noncontinuous motor winding modules spaced at 50-m intervals. A set of Halbach-arrayed permanent magnets on the bottom of the capsules interact with the linear motor windings to provide propulsion. The motor is driven by variable frequency drives outside the pipe to control the speed. This paper briefly describes the overall MagPipe pipeline transportation system, including the preliminary conclusions of the linear synchronous motor analysis.      

Lorentz force-type integrated motor-bearing system in dual rotor disk configuration

An integrated motor-bearing system combines the functions of an active magnetic bearing and an electric motor into a single unit. This paper proposes a generalized principle for the generation of torque and radial force in integrated motor-bearing systems using Lorentz force. The derived constraints lead to various feasible combinations of design parameters. Dual rotor disk configuration with a coreless stator is also proposed. It induces no negative stiffness, which is useful for the system stability and robustness to the tilting motion of the rotor. The test rigs are developed for five and six windings with an eight-pole rotor and operated successfully employing a simple PD-like controller.     

A Permanent Magnet Linear Synchronous Motor Drive for HTS Maglev Transportation Systems

A permanent magnet linear synchronous motor （PMLSM） for a high temperature superconducting （HTS） maglev system has been studied, including the motor structure, control strategy, and analysis techniques. Finite element analysis （FEA） of magnetic field is conducted to accurately calculate major motor parameters. Equivalent electrical circuit is used to predict the drive＇s steady-state characteristics, and a phase variable model is applied to predict the dynamic performance. Preliminary experiment with a prototype has been made to verify the theoretical analysis and the HTS-PM synchronous driving technology.     

Brushless DC Motor Propulsion Using Synchronous Motors for Transit Systems

In this paper, a brushless dc motor propulsion system using synchronous motors is described which is suitable for transit applications. The propulsion system consists of two-quadrant transistorized front-end chopper and a three-phase transistorized inverter (forming the electronic commutator for the synchronous machine phase currents) to provide both controlled propulsion and regenerative braking. The control scheme makes the system operate stably at all speeds and avoids loss of synchronization. Performance characteristics of the drive are derived and compared with those of a dc motor propulsion drive. Improved low-speed performance and reduced torque pulsation are achieved by proper switching of the electronic commutators. A prototype model using a 5-hp synchronous motor is built and tested.     

Microprocessor-based controller design and simulation for apermanent magnet synchronous motor drive

The speed control of a permanent magnet (PM) synchronous motor drive that is fed by a current hysteresis-controlled voltage-source inverter is investigated. The objective is to study the feasibility of implementing a microprocessor-based controller that may achieve complete software control of motor speed. A mathematical model and a digital control principle for controlling the PM synchronous motor are described. The sampling period and the controller parameters are determined analytically according to a linearized model. A systematic simulation procedure is proposed for verifying the feasibility of theoretical modeling and controller design. An experimental prototype system is constructed for correlating with the theoretical results. The experimental results closely follow theoretical predictions, thus validating the proposed control method     

基于DSP和光电编码器的永磁同步电机速度检测系统

为获取永磁同步电机转子速度,设计了一种基于DSP控制器正交编码电路和光电编码盘的检测系统。DSP识别光电编码盘上光敏管所产生的两路正交编码脉冲,对捕获的脉冲信号进行加减计数,通过对DSP编写的用户程序读取当前计数值,计算电机转子转速。阐述了TMS320F243芯片正交编码和增量式光电编码盘的工作原理,建立了由永磁同步电机、DSP板、逆变功放板和PC机组成的实验测量装置。实验结果表明,在给定的转速设定值下,能够实现快速和较高精度的速度检测,能够满足一般工程系统对交流调速和伺服控制的性能要求。