无速度传感器永磁同步电机低脉动直接转矩控制

传统永磁同步电机直接转矩控制系统的定子磁链、电磁转矩脉动较大,这些脉动在影响系统性能的同时,也影响电机参数的辨识精度。为实现永磁同步电机的低脉动无速度传感器直接转矩控制,采用EKF(扩展卡尔曼滤波器)构建电机转速、定子磁链观测器,以实现电机转速等参数的实时在线观测;构建转矩、磁链SMC(滑模控制器)取代传统DTC(直接转矩控制)中的滞环比较器和开关表以降低脉动。结果表明,无速度传感器永磁同步电机低脉动直接转矩控制能有效地降低电机转矩、磁链脉动,改善系统控制性能,同时,能实现永磁同步电机变量的快速、精确观测。     

高频PWM波反射对电机端过电压的影响

本文采用波理论分析变频驱动系统中高频PWM波反射,采用MATLAB仿真软件搭建软件模型,分析变频器输出电压波形的上升下降时间、供电电缆的长度、供电电缆分布参数及系统负载大小对电机前端过电压产生的影响,总结出高频PWM波反射对电机端过电压的影响。     

混合动力船舶能量管理控制策略设计与仿真

为了提高船舶的能源利用效率,降低排放,采用柴油发电机和燃料电池组成的混合动力为船舶提供电能,其中发动机为船舶提供基础载荷,当船舶功率负荷需求大于基础载荷时则由燃料电池组提供剩余的功率。针对这样的混合动力系统,设计船舶的能量管理系统的逻辑门限值控制策略和PID控制器。仿真结果表明,采用这种混合动力结构的船舶,可以提高柴油机的运行效率,所设计的PID控制器能很好地满足船舶的功率需求,提高系统的稳定性。     

CCS助推绿色航运

不久前,柴静的纪录片《穹顶之下》发布,引发了社会强烈反响。人们在将视线投向那些空气污染大户的同时,船舶排放污染也受到了越来越多关注。我国作为航运大国,民用船舶规模巨大,全力推动船舶技术进步,打造绿色航运,任重而道远。作为中国航运业和造船业重要技术支持力量,中国船级社(CCS)积极发挥独特优势,不断突破,为航运节能减排提供了强有力的技术支撑。     

A non-geometrically similar model for predicting the wake field of full-scale ships

The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non- geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering (KRISO)’s container ship (KCS) was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully.     

Numerical calculation of supercavitating flows over the disk cavitator of a subsonic underwater projectile

To deal with the effect of compressible fluids on the supercavitating flow over the subsonic disk cavitator of a projectile, a finite volume method is formulated based on the ideal compressible potential theory. By using the continuity equation and Tait state equation as well as Riabouchinsky closure model, an “inverse problem” solution is presented for the supercavitating flow. According to the impenetrable condition on the surface of supercavity, a new iterative method for the supercavity shape is designed to deal with the effect of compressibility on the supercavity shape, pressure drag coefficient and density field. By this method, the very low cavitation number can be computed. The calculated results agree well with the experimental data and empirical formula. At the subsonic condition, the fluid compressibility will make supercavity length and radius increase. The supercavity expands, but remains spheroid. The effect on the first 1/3 part of supercavity is not obvious. The drag coefficient of projectile increases as the cavitation number or Mach number increases. With Mach number increasing, the compressibility is more and more significant. The compressibility must be considered as far as the accurate calculation of supercavitating flow is concerned.     

含开口板结构振动能量流可视化研究

通过结构声强法研究了含开口复杂结构中振动能量传递特性。首先介绍了结构振动声强分量的相关理论以及振动能量流的计算公式;基于Matlab与APDL语言编写了集成可视化计算程序。在数值计算中,先验证了可视化程序的有效性;以含开口耦合结构为例,实现振动能量传递和分布的可视化,证明了计算程序的实用性和创新性;同时讨论了不同激励频率以及开口存在对能量传递及分布的影响,得到一些有益的结论。     

车轮踏面缺陷引起的轮轨动态响应综述

从滚动接触理论、试验与数值模拟三方面概述了轮轨关系研究现状,强调了轮轨滚动接触行为中轮轨材料动态力学性能的影响;总结了轮轨材料静动态力学性能与本构关系的相关成果;介绍了由车轮扁疤、踏面剥离/剥落、车轮多边形等典型踏面缺陷引起的轮轨动态响应研究,分析了车轮踏面缺陷对轮轨滚动接触行为和列车系统动力学性能的影响,以及车轮踏面...     

现代汽车电子技术及其在仪表中的应用

主要讨论汽车电子技术发展的简要历程,现代汽车电子技术的一些应用领域及已有成效,在此基础上介绍汽车智能仪表的开发流程及其应用关键。     

高压共轨电控喷射柴油机

简述高压共轨柴油发动机组成、原理及特点,并介绍其发展趋势,对推广使用高压共轨柴油发动机具有指导意义。