浅谈桥.门式起重机主梁拱度检测的简易方法：磁铁悬尺法

介绍了起重机主梁拱度的传统检测方法———拉钢丝法 ,及其在实际运用中的不足。剖析了现行吊钩悬尺法检测起重机主梁拱度时潜在的问题。笔者切合实际工作 ,提出了一种测量范围广 ,实用性强 ,无危险 ,简捷、省时、省力的新方法———磁铁悬尺法。文中运用几何学理论推导出磁铁悬尺法测量桥·门式起重机主梁拱度的数学计算公式 :h =h0 - 1 / 2 (hA+hB)。阐述了“磁铁悬尺法”的主要特点和实际应用价值     

一种低压低速多支路永磁同步电动机设计

提出了一种低压低速多支路永磁同步电动机的设计方案.给出了确定电机定、转子尺寸、绕组安排和转子磁路结构的方法.通过计算机辅助设计,得出电机的设计方案,应用Ansoft软件对电机进行二维建模仿真分析,结果表明了其结构设计的合理性.     

基于LMI的磁悬浮永磁直线电动机H∞鲁棒控制器的设计

针对磁悬浮永磁直线电动机中的不确定性扰动,提出基于线性矩阵不等式( LMI)方法设计进给系统的H∞鲁棒控制器.首先,采用矢量控制方法中的id=0控制策略,把非线性系统解耦成独立的线性电流子系统和速度子系统.其次,根据H∞性能指标与线性矩阵不等式的等价性,将设计问题转化为对LMI的求解,进而得到磁悬浮永磁直线电动机系统的状态反馈H∞控制器.最后,为了验证设计的有效性,在MATLAB环境下应用Simulink建立系统的仿真模型,对控制系统进行仿真研究,结果表明所设计的H∞控制器满足对不确定性扰动抑制的要求.     

封星技术在永磁同步曳引机中的应用

通过对永磁同步曳引机封星技术的论述及对封星电磁制动时电梯溜车速度的分析,发现在永磁同步曳引机中利用封星电磁制动可补充或替代某种工况下电梯机械制动的缺失,提高电梯在制动方面的安全性和可靠性。     

The online parameter identification of chaotic behaviour in permanent magnet synchronous motor by Self-Adaptive Learning Bat-inspired algorithm

One of the main issues in engineering is the identification of nonlinear systems. Because of the complicated as well as unexpected behaviours of these chaotic systems, it is introduced as special nonlinear systems. A minute change in the primary conditions of such systems would lead to significant variations in their behaviours. On the other hand, due to simple structure of Permanent Magnet Synchronous Motors (PMSM) and its high applications in industry, the use of this machine is dramatically increasing these days. The reflection of a chaotic behaviour as the Permanent Magnet Synchronous Motor is positioned in a particular area. In the model of PMSM, the exact parameters of the system are required to properly control and spot the error. In this paper, Self-Adaptive Learning Bat-inspired Optimization algorithm is used for solving both offline and online parameter estimation problems for this chaotic system. In addition, noise is considered as one of influential factors in control of PMSM. According to simulation results, it can be claimed that the proposed algorithm is a very powerful algorithm for online parameter identification for PMSM.     

基于自抗扰控制器的永磁同步电机直接转矩控制

针对传统永磁同步电机直接转矩控制(DTC)中转矩和磁链脉动较大以及转速超调的缺点,文中提出了一种基于自抗扰控制器的直接转矩控制策略。对于传统的PI控制策略中的磁链环、转矩环以及转速环不能满足控制系统非线性的需求,所提出的控制策略中非线性的自抗扰控制器满足了系统的非线性需求,提高了控制系统的动态响应能力。该策略中使用自抗扰控制器取代了传统PI控制结构,设计磁链、转矩和转速自抗扰控制器。通过搭建半实物仿真平台,进行实验验证文中控制策略的有效性。实验结果表明所提出的控制策略与传统的直接转矩控制相比较,文中提到的控制策略可以有效降低转矩和磁链的波动并提高系统的稳定性,降低了转速超调,改善了系统的动态性能。     

Permanent magnet magnetic refrigerator design and experimental characterization

Magnetic refrigeration (MR) using permanent magnets is being investigated for near-room temperature applications. An MR prototype is described and results using gadolinium as refrigerant are presented. Important design features are simple sealing, compactness, high operating frequencies, and ease of use. Using a total of 110 g of refrigerant, the device produces a maximum temperature span under no thermal load of 29 °C, and 10 °C under 50 W. The overall COP determined by using the power to the drive motor is between 0.3 and 0.8 under most operating conditions and temperature spans. The maximum COP measured is 1.6 with a span of 2.5 °C when operating at 1.4 Hz and utilization of 1.28. If the inefficiency of the motor is removed the maximum COP is 2.2, and, when the magnet drive losses are excluded, the maximum COP becomes 10. The peak specific exergetic cooling power is 0.085 W T⁻¹ cm⁻³.     

Design of a new magnetic refrigeration field source running with rotating bar-shaped magnets

Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) is a prime candidate for the next generation of cooling systems. The essential components of magnetic refrigeration are the magnetic field generator and the magnetocaloric material. Although, several permanent magnet systems (magnetic field sources) for MR have been developed, recent development in magnetic refrigeration technology has encouraged researchers all over the world to think about new and original systems. This paper aims to describe a new and original magnetic refrigeration system based on a simple principle of magnetism called the Halbach effect. The proposed system is running with rotating bar-shaped magnets. This structure provides the desired varying magnetic field to the magnetocaloric material. Several configurations for the proposed systems have been investigated and presented in this paper. The design and modeling have been accomplished by using the finite elements method.     

Monitoring and correcting spatio-temporal variations of the MR scanner’s static magnetic field

The homogeneity and stability of the static magnetic field are of paramount importance to the accuracy of MR procedures that are sensitive to phase errors and magnetic field inhomogeneity. It is shown that intense gradient utilization in clinical horizontal-bore superconducting MR scanners of three different vendors results in main magnetic fields that vary on a long time scale both spatially and temporally by amounts of order 0.8–2.5 ppm. The observed spatial changes have linear and quadratic variations that are strongest along the z direction. It is shown that the effect of such variations is of sufficient magnitude to completely obfuscate thermal phase shifts measured by proton-resonance frequency-shift MR thermometry and certainly affect accuracy. In addition, field variations cause signal loss and line-broadening in MR spectroscopy, as exemplified by a fourfold line-broadening of metabolites over the course of a 45 min human brain study. The field variations are consistent with resistive heating of the magnet structures. It is concluded that correction strategies are required to compensate for these spatial and temporal field drifts for phase-sensitive MR protocols. It is demonstrated that serial field mapping and phased difference imaging correction protocols can substantially compensate for the drift effects observed in the MR thermometry and spectroscopy experiments.     

基于模糊PID控制的永磁无刷直流电动机调速系统研究

针对传统PID控制的一些缺点,提出了一种永磁无刷直流电动机调速系统模糊PID控制方法,介绍了模糊PID控制器的设计方法,并利用MATLAB软件中的模糊控制工具箱进行了系统的辅助设计与仿真实验。仿真结果表明,该方法可使电机调速系统性能得到提高。