鼠笼电机程控混合模型仿真研究

磁链观测是矢量控制中的一个关键任务,电流模型在转速较低时比较精确,电压模型在转速较高时比较精确。结合两种模型使其依靠程序自动切换,在转速较低时使用电流模型,在转速较高时采用电压模型,可以对磁链进行准确的观测。以Matlab/Simulink为工具,采用程控自动切换混合模型对异步电机矢量控制算法进行了仿真。仿真结果验证了程控自动切换的可行性和矢量控制调速的动态响应快、硬特性强、稳态脉动小的良好性能。     

基于改进的电流模型磁链观测器的异步电机矢量控制

本文首先讲述了交流调速的现状,阐述了矢量控制原理,采用转子磁链定向搭建磁链电流模型,最后搭建了带转矩内环的转速、磁链闭环矢量控制系统仿真模型。使用MATLAB仿真软件进行了仿真,并在原来仿真基础上修改了相关仿真参数,结果验证了基于电流模型磁链观测器的矢量控制策略的优越性能。     

一种改进磁链计算模型分析

准确获取异步电动机转子磁链信号在高性能电机控制系统中具有十分重要的意义。介绍了常用转子磁链计算的电压和电流模型,针对各自存在的部分问题,提出了一种基于磁链计算方程进行组合的改进计算模型。在此基础上,根据矢量控制理论,采用Matlab／Simulink软件设计了异步电机矢量控制系统。仿真结果表明了该理论的正确性和可行性。     

基于MRAS无速度传感器矢量控制系统研究

根据异步电动机矢量控制基本原理,构建了基于转子磁链定向的模型参考自适应系统,并针对其基准模型易受积分初值和漂移问题的影响,提出了一种改进的速度辨识方法。该方法由改进的电压参考模型和电流可调模型构成。利用Matlab/Simulink对系统进行了仿真,仿真结果表明该系统能较好地估计电机的磁链及转速,收敛速度快,具有良好的...     

基于曲折型自耦变压器的节电器稳态模型

基于多绕组磁链耦合的原理,建立了一种基于曲折型自耦变压器的节电器稳态模型,重点分析该节电器零序等值电路的特性,说明其既可滤除负载的零序基波和谐波电流,又可避免因电源侧电压的零序分量产生较大的零序电流,仿真结果证明理论分析的正确性。     

异步电机全阶自适应磁链观测和速度辨识

针对传统的直接转矩控制系统采用纯积分的电压模型作为磁链观测器,存在着误差积累以及直流偏移,导致电流和转矩的波动问题,提出了一种基于定子磁链的自适应全阶观测器的直接转矩控制系统,并实现了速度辨识。仿真实验表明：采用自适应磁链观测器具有较高的观测精度和较好的鲁棒性。     

基于EKF的异步电机直接转矩控制系统仿真研究

为了提高直接转矩控制(DTC)系统定子磁链估计精度,降低电流、电压测量的随机误差,提出了一种基于扩展卡尔曼滤波(EKF)实现异步电机转子位置和速度估计的方法.扩展卡尔曼滤波器是建立在基于旋转坐标系下由定子电流、电压、转子转速和其它电机参量所构成的电机模型上,将定子电流、定子磁链、转速和转子角位置作为状态变量,定子电压为输入变量,定子电流为输出变量,通过对磁链和转速的闭环控制提高定子磁链的估计精度,实现了异步电机的无速度传感器直接转矩控制策略,仿真结果验证了该方法的可行性,提高了直接转矩的控制性能.     

基于定子电压、电流和转速的改进的子磁链观测器模型

介绍了一种基于U-I和I-ω的混合全速度转子磁链观测器模型，用改进积分器取代传统的积分器，并在模型中引入了磁链分量自身的反馈，从而保证磁链观测的准确性和地参数扰动的鲁棒性。文章最后给出了基于Matlab的仿真结果，以验证的怀能。     

内置式永磁同步电机直接转矩控制的仿真研究

在永磁同步电机直接转矩控制系统的基础上,分析了内置式永磁同步电机的最大转矩电流比动态磁链控制。设计了基于SVPWM的磁链给定的直接转矩控制系统,通过电压空间矢量连续调节,减小了直接转矩中转矩脉动。在MATLAB/SIMULINK仿真模型下,对该系统进行仿真,验证控制系统的有效性。     

基于MRAS的永磁同步电机直接转矩控制系统的研究

研究了一种基于模型参考自适应无速度传感器的永磁同步电机直接转矩控制系统:将永磁同步电机的磁链模型作为参考模型,估算的定子磁链模型作为可调模型,设计了自适应定律对电机的转速与定子电阻同时进行跟踪辨识,使用空间电压矢量调制技术组成了永磁同步电机无速度传感器直接转矩控制系统。仿真实验结果表明该系统获得了近似圆形的定子磁链,在转速与转矩变化时均能准确的估算出电机转速,具有良好的动、静态性能。     

一种确定弱非线性双端口网络模型参数的新方法

非线性传输函数模型和非线性电流源模型是利用Volterra级数对非线性动态电路建模的两种形式;本文提出一种确定一类弱非线性双端口网络非线性电流源模型参数的方法,它通过测量网络的端口特性来确定其模型参数;这种方法比测量Volterra核的方法简单方便。     

A new current model flux observer for wide speed range sensorless control of an induction machine

A new closed loop current model flux observer is designed to estimate the rotor flux, position and velocity of an induction machine. The current observer includes carefully designed sliding mode functions which are derivative of the fluxes along the /spl alpha/ and /spl beta/ axes. Therefore, when the estimated current converges to the measured one, the flux estimation is a mere integration of the sliding mode function. The rotor speed can then be derived from the sliding mode functions and the estimated flux. In the current and flux observers all of the terms that contain the rotor time constant and the rotor speed have been replaced by the sliding mode functions, thus making the proposed current and flux estimations completely insensitive to the rotor time constant variation and any error in the estimated speed. Simulations and experiments are performed under a variety of conditions to validate the effectiveness of the proposed algorithm.     

自然语言处理中的模型

本文简单介绍了自然语言处理发展的现状,讨论了自然语言处理模型,将其分为三大类:分析模型、统计模型及混合模型.具体介绍了分析模型原理及存在的问题,重点讨论了各种统计模型的特点及局限性,最后简单介绍了混合模型,并指出目前自然语言处理技术中存在的问题.     

Biomagnetic Fourier imaging [current density reconstruction

A technique for reconstructing a current density distribution from measurements of its magnetic field is described. The technique assumes that the current distribution is confined to a single plane. The data it requires are measurements of the magnetic flux on a plane. These can be provided by an integrated planar array of superconducting quantum interference device magnetometers. The approach is based on the magnetic lead field which is derived in a simple way based on energy concepts. Using the lead field and conservation of charge conditions provides two linear, spatially invariant imaging equations relating the current density and flux measurements. These equations are solved using Fourier techniques. The validity of the resulting reconstruction technique is shown both analytically and with a computer model. The effects of not satisfying the planar assumption are described for the case where the currents are parallel but not in the same plane.     

Flux trapping in a ring-shaped YBCO bulk by pulsed fieldmagnetization

A pulsed magnetic field can be applied using small coils to generate a strong magnetic field for the magnetization of the high-Tc superconductors (HTS) to be used as quasi-permanent magnets in flywheels and motors. The dynamic electromagnetic behavior of two melt-processed ring-shaped Y-Ba-Cu-O bulks using the pulsed field magnetization (PFM) process has been experimentally investigated and analyzed. The flux trapped in the bulk by PFM process was compared to the flux trapped by field cooling process. Both cases then have been analyzed with a numerical model based on the finite-element method (FEM). The power-law model was utilized to relate the electric field to the current density inside the superconductor. The dependence of the critical current density on the magnetic field density was taken into account. Measured and calculated results are compared and discussed     

Simultaneous State and Parameter Estimation in Induction Motors Using First- and Second-Order Sliding Modes

We address the problem of meeting the requirements of controllers for the control of speed of induction motors, but under the constraint of not using speed and flux sensors: the so-called “sensorless” control problem. We offer an observer-based solution and present the design of two observers which provide motor speed, flux, and rotor resistance estimates simultaneously. Both observers, based on the rotor flux model in the stationary reference frame, are designed with inputs that enforce first- (conventional) and second-order sliding modes, respectively, on appropriately chosen switching surfaces. We present experimental results of the estimation procedure to demonstrate that only current and input voltage measurements are needed for accurate speed and flux estimation even in the presence of unknown parameters.