基于Buck-Boost变换方式的逆变器

提出了一种基于Buck-Boost变换方式的逆变器。它能实现输出电压高于输入侧直流电压,克服在传统桥式逆变器拓扑中输出电压低于输入侧直流电压而造成的直流电压利用率低的问题。通过改变一个周期内的占空比,以改变单个双向Buck-Boost变换器的输出电压。两个相位相差180°的双向Buck-Boost变换器的输出电压相减即可得到较为理想的单相正弦波;三个相位相互相差120°的双向Buck-Boost变换器可实现三相逆变。可采用SPWM控制功率管的关闭与导通,控制方式采用外环电压环内环电流环的双环控制。仿真结果验证了提出的正弦波逆变器的可行与有效。     

并联介质加载环天线的脉冲辐射特性研究

介绍一种由环天线和介质块并联组成的小型化方向性脉冲天线,分析环天线的辐射机理,应用时域有限差分(FDTD)方法和完全匹配层(PML)技术对天线的辐射特性进行了研究。研究结果表明,该天线具有良好的方向性,辐射脉冲保形性较好,选择合适加载的情况下,连接50Ω的馈线,电压驻波系数小于3时,天线的阻抗带宽达到2.8 GHz(从2.8 GHz到5.6 GHz),其相对带宽为66.7%。该天线具有轮廓低、扁平化的特点,并且容易集成到系统中,可用于无载波超宽带无线数据通信系统。     

通过单片机实现对可编程电机的调速控制

使用单片机实现对PG电机的闭环调速控制,可以使电机的转速实现平稳无级调节,并且能有效地降低噪音。本文通过分析其工作原理,结合具体电路,给出了控制实现方案。     

Characterizing,measuring, and managing transit service quality

Recent studies to evaluate the quality of transit service are generating a good amount of renewed interest in an old idea, the passenger's perspective; this new interest stems from recognizing that transit service quality should be characterised, measured, and managed by parameters capturing both passenger and transit operator perspectives. However, although the selected parameters are user‐oriented in their input, the output may not be as user‐oriented as considered, and the number or the percentage of passengers is often neglected. As a result, the findings are often misleading because the perspectives of transit operators dominate. Therefore, academics and practitioners must rethink their strategies of quality analysis of public transportation by stressing more on the role of passengers. These challenges are addressed in this paper with a practical, simple, and holistic framework, for Transit Quality (TRANSQUAL). This framework provides for the involvement of all stakeholders in the characterisation, measurement, and management of the stages of quality monitoring, which is jointly analyzed at different planning levels. In the characterization stage, the framework supports the selection of parameters to be monitored. The measurement stage sets and measures four quality areas in terms of percentage of passengers who expect a predefined level of service, for whom the service is designed, who receive the planned service, and who perceive the service as delivered. The management stage computes the differences between these percentages, points out criticalities, and recommends corrective actions. These stages are investigated in‐depth, integrated, and discussed in a real‐life case study. Copyright © 2016 John Wiley & Sons, Ltd.     

发动机图像数据提取

对获得的发动机万有特性图像编写程序实现数据提取,同时对已获得的图像数据,采用数学方法建立发动机模型．通过误差分析与图像对比．表明建模方法的正确。     

网络流的多重解问题研究

介绍了最大流问题的多解,并从此问题出发,研究了最小费用最大流的多重最优解问题,总结了判断多重最优解存在的准则。该准则为若已求出的最小费用最大流分配网络中存在其两个弧组费用相等的可调圈,此问题就有多重最优解。在符合条件的可调圈上进行流量调整,便可得到该最小费用流问题不同的最优解。     

深度模拟器的试验研究

针对深度模拟器中存在的一些问题,比如动态响应频率低,无法准确跟踪预定的输入信号,自适应能力差等,开发了一种新型的深度模拟器。并通过开发研制及实验测试。测试试验的结果进一步确定研制的深度模拟器的效果满足使用要求,同时为下一步深度模拟器的优化设计及推广提供依据。     

基于锁相环的永磁同步电机无位置传感器控制技术研究

本文针对低速永磁同步电机给出了基于高频旋转电压注入的永磁同步电机转子位置自检测方法,该系统采用锁相环作为转子位置观测器。最后本文在Matlab/Simulink软件下对无位置传感器控制系统进行了仿真,仿真结果验证了该方法的可行性。     

Design of rail pressure tracking controller for novel fuel injection system

This paper proposes a rail pressure tracking controller based on a novel common rail system. A mathematical model, based on physical equations, is developed and used for feed forward control design. Rail pressure peak sampling mechanism is designed to remove the disturbance of rail pressure due to fuel injection. An enhanced tracking differentiator is designed to get smooth tracking signal and exact differential signal from signal with noise. Double loop control strategy is designed to decouple the system and to improve dynamic performance of the system. Experimental results indicate that fluctuation of rail pressure is within ±1 MPa in steady condition, while within ±3 MPa in transient condition, which verifies the effectiveness of the proposed rail pressure control strategy.     

城市轨道交通环线客流特征分析及启示

轨道交通环线在轨道交通网络中具有特殊的地位和作用。首先,通过对比分析北京市、上海市轨道交通环线与非环线路的客流特征,总结出环线具有可达性较强、客运量高、断面客流量波动性较小、平均运距较短、换乘量较大等特征。其次,分析北京市第二条环线成环前后轨道交通线路客流特征变化、外环线路开通对内环线路的影响以及环线对于放射线路的分流作用,总结双环结构中内外环之间的关系及对放射线路的影响。最后,从轨道交通环线在线网中的功能、位置选择和建设时机等方面提出探索性建议。