Thrust stand for low-thrust liquid pulsed rocket engines

A thrust stand is developed for measuring the pulsed thrust generated by low-thrust liquid pulsed rocket engines. It mainly consists of a thrust dynamometer, a base frame, a connecting frame, and a data acquisition and processing system. The thrust dynamometer assembled with shear mode piezoelectric quartz sensors is developed as the core component of the thrust stand. It adopts integral shell structure. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. The thrust is transferred to the sensors by means of static friction forces of fitting surfaces. The sensors could produce an amount of charges which are proportional to the thrust to be measured. The thrust stand is calibrated both statically and dynamically. The in situ static calibration is performed using a standard force sensor. The dynamic calibration is carried out using pendulum-typed steel ball impact technique. Typical thrust pulse is simulated by a trapezoidal impulse force. The results show that the thrust stand has a sensitivity of 25.832 mV/N, a linearity error of 0.24% FSO, and a repeatability error of 0.23% FSO. The first natural frequency of the thrust stand is 1245 Hz. The thrust stand can accurately measure thrust waveform of each firing, which is used for fine control of on-orbit vehicles in the thrust range of 5-20 N with pulse frequency of 50 Hz.     

A pulse-compression-ring circuit for high-efficiency electric propulsion

A highly efficient, highly reliable pulsed-power system has been developed for use in high power, repetitively pulsed inductive plasma thrusters. The pulsed inductive thruster ejects plasma propellant at a high velocity using a Lorentz force developed through inductive coupling to the plasma. Having greatly increased propellant-utilization efficiency compared to chemical rockets, this type of electric propulsion system may one day propel spacecraft on long-duration deep-space missions. High system reliability and electrical efficiency are extremely important for these extended missions. In the prototype pulsed-power system described here, exceptional reliability is achieved using a pulse-compression circuit driven by both active solid-state switching and passive magnetic switching. High efficiency is achieved using a novel ring architecture that recovers unused energy in a pulse-compression system with minimal circuit loss after each impulse. As an added benefit, voltage reversal is eliminated in the ring topology, resulting in long lifetimes for energy-storage capacitors. System tests were performed using an adjustable inductive load at a voltage level of 3.3 kV, a peak current of 20 kA, and a current switching rate of 15 kA/micros.     

Power managements of a hybrid electric propulsion system for UAVs

Power managements of a UAV??s hybrid electric propulsion systems are described. Three electric propulsion systems with different power sources, i.e. solar cells, fuel cells, and batteries are considered. Each power source is modeled in Matlab/Simulink and integrated into the power system. For fuel cells and batteries, the simulation process is verified via comparison between the simulation results and available flight test results of UAVs. Two types of power control logics are investigated: passive and active. The passive power management simulation shows that the behavior of each power source and its integrated system is adequate for the overall flight envelope. In addition, the active power management simulation demonstrates that active power management yields more efficient power distribution and better system safety than passive power management does. Also, a power simulation of a hybrid electric power system allows for estimation of the output behavior of the power source. Therefore, it can be a valuable tool for development of a power control logic that ensures efficient power distribution.     

Non-contact thrust stand calibration method for repetitively pulsed electric thrusters

A thrust stand calibration technique for use in testing repetitively pulsed electric thrusters for in-space propulsion has been developed and tested using a modified hanging pendulum thrust stand. In the implementation of this technique, current pulses are applied to a solenoid to produce a pulsed magnetic field that acts against a permanent magnet mounted to the thrust stand pendulum arm. The force on the magnet is applied in this non-contact manner, with the entire pulsed force transferred to the pendulum arm through a piezoelectric force transducer to provide a time-accurate force measurement. Modeling of the pendulum arm dynamics reveals that after an initial transient in thrust stand motion the quasi-steady average deflection of the thrust stand arm away from the unforced or "zero" position can be related to the average applied force through a simple linear Hooke's law relationship. Modeling demonstrates that this technique is universally applicable except when the pulsing period is increased to the point where it approaches the period of natural thrust stand motion. Calibration data were obtained using a modified hanging pendulum thrust stand previously used for steady-state thrust measurements. Data were obtained for varying impulse bit at constant pulse frequency and for varying pulse frequency. The two data sets exhibit excellent quantitative agreement with each other. The overall error on the linear regression fit used to determine the calibration coefficient was roughly 1%.     

Experimental hover performance evaluation on a small-scale rotor using a rotor test stand

This paper presents the work being carried out in order to deduce hover performance of a small-scale single rotor blade as a preliminary study of a small coaxial rotor helicopter development. As an initial research, a test stand capable of measuring thrust and torque of a small-scale rotor blade in hover state was constructed and fabricated. The test stand consists of three parts; a rotating device, a load measuring sensor and a data acquisition system. Thrust and torque were measured with varying collective pitch angle at fixed RPM. Through this research, hover performance tests were conducted for a small-scale single rotor blade operating in low Reynolds numbers (Re ≈ 3 × 10⁵). The rotor blades investigated in this paper have maximum FM values varying from 0.59 to 0.65, which are low relative to modern full-scale helicopters. From these differences in FM between a small and a full-scale helicopter, the induced power factor is determined as varying from 1.35 to 1.42. Through this study, tests of hover performance were conducted for a single small-scale rotor blade, as well as verifying the test stand itself for the acquisition of hover performance.     

船舶电力推进实时监控系统的研究

本文以船舶电力推进系统为研究对象,运用CC-Link总线技术及RS-232通讯技术,实现船舶电力推进系统的实时数据传输,并针对该系统在Visual Basic 6.0集成开发环境下开发了应用程序,对船舶电力推进系统的重要参数进行监测.试验结果表明,系统数据传输正常,应用程序有效,实现了对船舶电力推进系统的实时检测与控制.     

基于Profibus-DP现场总线电力推进试验平台的设计

对电力推进试验平台的控制系统Profibus-DP网络结构进行简介.详细介绍Profibus-DP主站与变频器的通信协议、网络组态及其参数设置方法和通信程序设计方法.Profibus-DP控制系统布线简单、维修方便,运行可靠,达到了设计要求.     

交流变频调速技术在船舶电力推进系统中的应用

随着新型电力电子器件的发展,交流变频调速技术成为现代交流传动调速技术领域的主要标志之一,本文着重介绍了交流变频调速技术的原理,及其在船舶电力推进系统中的应用.     

Wear performance of unidirectionally oriented carbon-fibre-reinforced plastics

Wear between unidirectionally oriented carbon-fibre-reinforced plastics and steel has been investigated. The wear behaviour was greatly influenced by the sliding direction and the type of carbon fibres; the best wear resistance being obtained when sliding at right angles to high-modulus carbon fibres and the worst when sliding at right angles to high-strength carbon fibres. Transmission electron diffraction and ESCA studies showed that the surface-film formed on a worn high-modulus carbon-fibre-reinforced epoxy was a mixture of graphite and epoxy.     

面向刀具序列的模具型腔高效加工策略

为了实现模具型腔的高效加工,提出了一种面向刀具序列的模具型腔高效加工策略。在该策略中,刀具选用圆弧角铣刀和球头刀。按照优先选用圆弧角铣刀和大直径刀具的原则,根据建立的最大可行刀具数字化加工几何模型,确定了刀具序列中每把刀所对应的加工区域和实际加工中每把刀只切除所对应的加工区域。应用该策略可以避免加工特征的识别,同时克服了高速加工刀具刚性差的缺点。验证了加工策略,证明该加工策略对模具型腔的高效加工具有较高的实用价值。     

Manufacturing performance evaluation for IC products

As we known, the product diversity and complexity in the production line will gradually increase. When the multiple products were alternately produced at the same line, the manufacturing performance will be difficult to evaluate. In particular, traditional process capability analysis and related process capability indexes cannot be directly employed to the IC manufacturing process. As we know, the yield has a direct effect on the manufacturing cost. Hence, yield is frequently used by most IC manufacturers to evaluate manufacturing performance. The diversity of function will become another analytic consideration due to that the component density, wafer area and product complexity of an IC product rapidly increase. Hence, the diversity of function can be regarded as the evaluated factor. Additionally, the defects on a wafer will begin to cluster as the wafer area gradually increases. Therefore, only using the yield to represent manufacturing performance may not lead to an appropriate judgment. In particular, only using the yield to evaluate the process’s stability and the product’s maturity can not provide a meaningful resolution. The primary reason is that the inherent features in the processes or products are not included into analyzing. For instance, even though the defect count, defect size and defect distribution are the same, the yield loss of the complicate manufactured product will be less than that of the simple manufactured product. In this study, we propose a simple performance evaluation index to assess the manufacturing performance in the IC manufacturing industry. This evaluation index is constructed according to a modified Poisson yield model, and the related parameters regarding the process or product (e.g., the minimum linewidth, the area of a die, the number of manufactured process or layer, the degree of defect clustering, and so on.) are taken into consideration. In addition, an integrated evaluation procedure is also suggested to evaluate the performance of the manufacturing of multiple IC products. According to the result obtained from the illustrative example, the index and the procedure can overcome the drawback of separately using yield or defect count in the analysis. The rationality and the feasibility of the proposed evaluated index and the procedure can be verified by demonstrating the illustrative example.     

航空发动机推力销水平推力校准试验技术研究

为了得到航空发动机推力与推力销应变输出之间的线性关系,利用自行研制的载荷标定试验设备,对推力销的推力进行了校准试验.分别利用剪力应变桥和弯矩应变桥的改装测试方式,通过施加不同的水平推力对推力销的应变输出进行测量,得到推力销应变计输出与载荷的关系,即可得到载荷标定方程.通过数据处理与线性拟合的结果表明,两种应变测量方法均具有良好的线性度和重复性,均可用于航空发动机车台试验的推力测量.     

面向模型重构的设计理性知识粒度评价方法

为满足不同抽象层次设计理性模型重构的多样性量化需求,在设计理性建模的基础上研究了设计理性知识粒度评价方法。通过辨析知识体特性分析影响设计理性模型粒度的组成因素,建立了粒度度量方法,实现了统一的评价体系,为不同粒度设计理性模型的转换、比较和优化提供了客观、量化的依据和目标。以压弯模具部分设计过程为例,验证了设计理性知识粒度评价方法对模型重构度量及指导的可行性与有效性。     

面向改型设计的模块化产品评价方法

针对改型设计的模块化定制产品的评价问题,提出一种综合考虑产品定制度和用户满意度的评价方法。将定制成本细分为设计定制成本、制造定制成本和装配定制成本,求得零部件定制成本之和及其所占比重,得到定制度;考虑了多种用户满意因素,并将价格因素和其他因素分开计算,得到用户满意度。结合定制产品的实际情况,综合产品定制度和用户满意度,以此对多个模块化定制产品进行评价。通过实例,验证了相关方法的有效性。     

基于AHP-熵权-TOPSIS的电动汽车动力性经济性综合评价方法

动力性指标与经济性指标在纯电动汽车的设计和使用过程中既相互联系,又相互对立,因此应对其进行综合评价.通过文献统计,选择最高车速、加速能力、爬坡能力、续驶里程、百公里耗电量作为纯电动汽车动力性与经济性的综合评价指标,构建了应用于纯电动汽车动力性经济性综合评价的指标体系,采用层次分析法和熵值法综合确定各指标权重,以理想解法进行排序,建立了基于AHP-熵杈-TOPSIS的纯电动汽车动力性与经济性的综合评价模型,并以实例说明了模型的应用.     

Comparison of indices for stiffness performance evaluation

This paper addresses the problem of a numerical evaluation of the stiffness performance for multibody robotic systems. An overview is presented with basic formulation concerning indices that are proposed in literature. New indices are also outlined. Stiffness indices are computed and compared for a case study. Results are used for comparing the effectiveness of the stiffness indices. The main goal is to propose a performance index describing synthetically the elastostatic response of a multibody robotic system and also for design purposes.     

Comparison of indices for stiffness performance evaluation

This paper addresses the problem of a numerical evaluation of the stiffness performance for multibody robotic systems. An overview is presented with basic formulation concerning indices that are proposed in literature. New indices are also outlined. Stiffness indices are computed and compared for a case study. Results are used for comparing the effectiveness of the stiffness indices. The main goal is to propose a performance index describing synthetically the elastostatic response of a multibody robotic system and also for design purposes.     

面向服务的工作流性能评价及指标相关度分析

为说明服务的性能与工作流性能的关系,提出服务及面向服务的工作流的定义,并以一个示例说明面向服务环境下工作流的特点及运行机制.在此基础上,提出了面向服务的工作流性能评价模型,并将战略层、业务层、服务层与IT层的性能很好地加以结合.定义了各层的关键性能指标及形式化表达方式,提出相关度的概念.最后,通过改进层次分析法,对关键性能指标的相关度进行分析,并将其用于服务的选择.     

面向网络化制造的制造资源组合评价方法研究

在网络化制造环境中,针对分布在不同地域的制造资源评价和选择问题,在建立制造资源评价指标体系的基础上,提出了一种基于组合评价模型的网络化制造资源组合评价方法。实例分析中对采用熵值法和层析分析法为代表的主客观赋权法分别进行了评价,最后利用组合模型进行综合评价,对制造资源问题进行了系统分析。通过主客观赋权法的组合,充分利用了各种方法的有用信息,避免了单一评价方法的片面性,增强了评价的科学性和可靠性。