离子推进系统电源研究

离子推进电源处理单元（PPU）是组成离子电推进系统的关键设备之一。本文以某离子电推进系统配置的电源处理单元为例,针对多路组合、输出功率大、电压高及时序控制等电源特点,采用不同的电源变换拓扑方案,来实现复杂电源功能。并通过实际电路验证和检测,研究结果满足了设计指标要求。     

电推进系统空心阴极研制试验技术

空心阴极是电推进系统可靠性和工作寿命文从空心阴极的试验分类、试验设备、试验技术等方面介绍了电推进系统应用空心阴极的研制试验技术.     

The impact of satellite altitude on the performance of LEOS based communication systems

Low earth orbit satellite (LEOS) systems promise to provide global communication, including voice and data services from Iridium and high capacity broadband services from Teledesic. In design of LEOS systems, the choice of satellite altitude is an important consideration, which has a significant impact on system performance. Among the factors affected by satellite altitude choice are system capacity, user‐to‐user delay, power system design and communication services that can be offered. This paper analyzes the effects of satellite altitude on quality of service, frequency reusability and power system sizing. It is found that a choice of low altitude has a positive impact on system capacity and power system requirements. As a consequence, satellite mass and launch cost can be reduced for satellites in lower orbits due to the lower power requirements. In terms of user‐to‐user delay, the results are in favor of medium altitudes, while very high altitudes are not a good choice relative to these measures. This revised version was published online in June 2006 with corrections to the Cover Date.     

Propulsion system design of electric and hybrid vehicles

There is a growing interest in electric and hybrid-electric vehicles due to environmental concerns. Efforts are directed toward developing an improved propulsion system for electric and hybrid-electric vehicles applications. This paper is aimed at developing the system design philosophies of electric and hybrid vehicle propulsion systems. The vehicles' dynamics are studied in an attempt to find an optimal torque-speed profile for the electric propulsion system. This study reveals that the vehicles' operational constraints, such as initial acceleration and grade, can be met with minimum power rating if the power train can be operated mostly in the constant power region. Several examples are presented to demonstrate the importance of the constant power operation. Operation of several candidate motors in the constant power region are also examined. Their behaviors are compared and conclusions are made     

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.     

发射台信息管理系统的设计探析

对发射台构成及功能进行简介,指出发射台信息管理系统所具有的功能,提出发射台信息管理系统的开发流程,并明确了开发过程中的要点。同时对信息系统如何正确管理、科学运行、监控和评估进行综合性阐述,为系统开发及管理人员提供参考。     

Livingstone用于航天器推进系统故障诊断

航天器通常造价昂贵且无法批量生产,对其进行故障检测和诊断研究实用且必要。由美国宇航局 NASA 开发的 Livingstone 软件系统,使用一组多层次的定性逻辑模型来描述系统的行为,通过比较模型预测数据和传感器实测数据来检测和诊断系统故障。本文旨在说明 Livingstone软件能够应用于航天器故障检测和诊断领域。通过对 Livingstone 工作原理和过程的详细阐述,并利用 Livingstone 对航天器推进系统简化模型做仿真实验,给出可能的故障原因及可能性大小,说明 Livingstone 是一种有效而可靠的故障检测和诊断工具,能够快速、准确地诊断出航天器系统故障所在。     

CMMB发射监控系统设计与建设

武汉市CMMB覆盖网存在大量的无人值守发射站,为了实时监控各发射站的运行情况,并为运维工作提供有力的支持,湖北中广建设了一套完善的监控系统。依靠该系统,工作人员可通过软件或网页实时监测各发射站的设备运行及开路信号情况,当出现异常时监控系统会发出警告并记录,技术人员也可通过该系统远程对发射站部分设备的配置和运行进行调整。从系统构成、系统功能及实施效果等多方面详细介绍了该监控系统的设计思路与建设方式。对今后进行类似系统的设计建设提供了宝贵的经验和参考依据。     

Propulsion systems for electric cars

Proper selection of the propulsion system to meet the requirements of an electric passenger vehicle is of prime importance. Choice may be made among alternating current, direct current, or combined systems. Each approach can be implemented by utilizing various control techniques and power elements. For instance, an ac system may use an adjustable voltage inverter (AVI) or a pulse-width-modulated inverter (PWMI) for the power processor, and an induction motor or a synchronous motor for the rotating element. Similar alternatives exist for a dc system. The choice of a suitable manner of implementation must be. based on information characterizing the various elements and tradeoffs matching them to the vehicle requirements. This paper describes various ac and dc techniques, characterizes AVI, PWM, and representative dc chopper power processors and examines their interface with a variety of motors such as series, shunt, induction, etc.     

Computer experiments on electron guns

Computer techniques for analyzing an axially symmetric or two-dimensional electrode system with an emitting surface can be used to obtain cathode current density distribution, beam minimum radius and its location, as well as possible electrode current interception. Here, comparison is made of available experimental data from two axially symmetric Pierce-type guns. The choice of the two axially symmetric Pierce-type guns was made for their different value of PV/T ratio, an invariant for transverse scaling. One of them has a low ratio of PV/T(approx 0.1 times 10^{-6}), which signifies considerable beam spread due to the effects of the Maxwellian velocity distribution of the thermal electrons leaving the cathode. The other gun has a high perveance of2 times 10^{-6}, and thus relatively high PV/T ratio where beam spreading is mainly due to space-charge forces alone. Good agreement with experimental data is shown. Computer techniques of this type can be a valuable tool for diagnostic purposes of any type of space-charge-flow devices (e.g., electron guns, ion guns for space propulsion, linear accelerators, etc.) and enable the engineer-designer to arrive quickly and cheaply at an optimum configuration.     

Underground tunnels for transport systems

In densely populated regions, tunnels hundreds of feet below the earth's surface may be attractive guideways for high-speed transportation systems. Advantages include stability, isolation from weather variations, ease of positive control of the system, absence of interference from other structures and transportation modes, and potential alternative uses of the tunnels for such functions as storage, fluid transport, and defense purposes. If the system terminals are located near the surface, propulsion and braking requirements of the vehicles can also be greatly simplified. The principal deterrent is construction costs. These are being reduced by mechanized tunnelling mechines now undergoing much development but hard, strong rock still requires slow, expensive drill and blast techniques. Research to rapidly weaken hard rock so mechanical moles can tunnel it economically is being done. Both thermal treatments and the use of water-borne surface active agents are effective weakeners. A 1000-watt continnous-duty CO2laser can reduce the strength of marble or granite by a factor of ten in 3 to 5 seconds exposure time.     

箭载中继用户终端自跟踪测向技术

箭载中继用户终端对中继卫星的捕获跟踪是建立箭星间数据链路首要前提。针对Ka波段波束窄、箭载设备小型化要求高等特点,提出一种利用火箭飞行、姿态等辅助信息的自动角跟踪技术,并利用仿真,验证该技术可实现高精度测向,可作为箭载中继用户终端自跟踪系统设计和工程研制的参考。     

运载火箭时序仿真测试系统设计

检测运载火箭地面测试设备的方法种类繁多,方法复杂,测试周期较长。设计一种运载火箭时序仿真测试系统,采用FPGA芯片的SOPC(可编程片上系统)技术,基于全双工USB 3.0控制芯片( CYUSB3014)完成上位机通信,单板模拟运载火箭飞行过程中64路时序系统发出的时序信号和时串信号,对不同测试需求的地面测试设备进行功能检测和故障诊断。具有方法简单,通用性好、精度等级高、通道数多的优点,能有效提高地面测试设备在测试任务中的测试效率。     

火箭弹载捷联惯导简易标定路径设计

捷联惯导误差标定中考虑的误差主要包括零偏误差、刻度系数误差、安装误差。标定的误差参数越多,难度越大,并且火箭炮在发射标定阶段无线运动,只能进行两自由度角运动,导致误差参数基本不可观测。如果能抓住影响导航精度的主要误差,将可简化标定算法,简化标定过程,提高标定效率。基于这样的思路,将旋转的弹丸类比为旋转惯导,从误差方程入手,采用提取误差直流分量的方法对飞行中的弹载惯导进行误差分析,得出影响导航精度的主要误差参数,然后提出了利用机动前后速度误差的变化的方法进行机动方式设计,该方法不需要求解微分方程,大大降低了计算量。仿真结果表明,所提出的简易标定方案解决了发射准备阶段激励不足,不能进行有效标定的问题。     

An experimental and theoretical study of the offset launchtechnique for the enhancement of the bandwidth of multimode fiber links

This paper reports an experimental and theoretical study of bandwidth enhancement in multimode fiber links achieved by using offset launch techniques. It is found, both from theory and experiment, that an up to four-fold bandwidth enhancement can be obtained compared to standard overfilled launch techniques despite exciting over 50% of the fiber modes, thus allowing good stability. The enhancement technique is found to be achieved for a range of fibers with different core diameters and core refractive index profiles. The level of bandwidth enhancement depends upon the inherent bandwidth of the fiber, being particularly effective in improving the performance of low bandwidth “worst case” fibers. The launch is found to be stable with respect to environmental variations, showing bandwidth enhancement for injection positions or connector offsets of up to 5 μm from optimum. In addition, unlike many restricted launch techniques, it is found to be tolerant to angular fiber misalignment for angles up to 6° from normal     

内河船舶电力推进系统的节能与环境效益评估

为了适应我国船舶排放控制的要求, 内河船必须采取节能减排措施。以两艘实船为基础, 分析柴油机直接 推进和电力推进系统的能耗和排放数据, 得出电力推进系统具有更好的节能优势和较大的环境效益。我国 正加大力度研究电力推进的核心技术和关键设备, 也必能促进电力推进产品的发展, 提高相应产品的质量 并且降低价格, 将来内河船有望逐步拓展采用电力推进系统。     

Wafer distribution system for a clean room using a novel magneticsuspension technique

A linear transport system, which is capable of reducing the weight of a moving carrier by separating power-supplying devices, is developed by using a new magnetic levitation technique. This system is designed to distribute a wafer between semiconductor fabrication process modules in clean rooms, because it can eliminate particles and oil contamination that normally exist in conventional transporter systems due to rubbing of mechanical components. The transport system consists of a wafer carrier, two levitation tracks, two stabilization tracks, and a propelling system. Levitation is achieved by using opposing forces produced between electromagnet tracks and permanent magnets. Stabilization is achieved by using a simple feedback control. The continuous propelling force is obtained by sending specific current patterns to the propulsion coils. The dynamic model of the transport system is presented, and it is verified by experiment. The system performance is experimentally investigated     

A methodology for optimizing a constant temperature polysilicondeposition process

A three-step approach to characterizing a low pressure chemical vapor deposition (LPCVD) constant temperature polysilicon process is discussed. This approach optimizes an LPCVD polysilicon process for both film uniformity and particles. The first step is to design and construct a constant deposition temperature polysilicon furnace to provide the best system performance possible in terms of particle generation and improved film uniformity. The second step is to characterize a process in this newly constructed furnace for both film uniformity and particles by using an experimental design that incorporated an L₁₈ orthogonal array. The hydrogen chloride preclean flow prior to deposition plays a key role in both defect generation and film uniformity. Both capacitance-voltage techniques and secondary ion mass spectrometry are used to understand this role. The third step is to verify the recommended setting from the experimental design by processing confirmation runs. Results from the confirmation runs in the optimally constructed polysilicon furnace show that particles can be reduced by up to 66% and film uniformity can be improved by 29% over the current production process     

Design and Control of a Linear Propulsion System for an Elevator Using Linear Switched Reluctance Motor Drives

Linear switched reluctance motors (LSRMs) for the primary propulsion of a ship elevator is proposed and investigated for the first time in this paper. To achieve the stated objective, a new type of LSRM is proposed with twin stators and a translator between them with no back iron in the translator. The proposed configuration of the LSRM is designed, simulated, analyzed, compared with traditional LSRMs, and verified by experimental measurements. The number of LSRM propulsion subsystems required is studied with a view to minimize their weights and an optimization study for that purpose is developed. Unique placement of the LSRM propulsion systems on the elevator is presented. The propulsion force is generated using one phase or multiphase excitation. To reduce propulsion force pulsations, a major requirement in elevators, controlled multiphase excitation using one of the known force distribution functions (FDF) is an acceptable solution. In this paper, it is proved that the currently available FDFs are able to reduce the force pulsations but are not able to meet the peak force command for the system. Consequently, the velocity and position control do not meet even the elementary performance requirements any more. A new FDF is proposed in this paper and presented to overcome the problem caused by a conventional FDF. The control system with the proposed FDF is derived and integrated into velocity and position controllers. Extensive dynamic simulation and experimental verification of the proposed LSRM with the novel FDF is proved to give superior performance in this paper. Such high performance capable of meeting vertical elevator applications is demonstrated.