直摆头与斜摆头五坐标机床数控加工程序互换求解算法

 针对复杂结构零件五坐标加工设备变更带来的程序处理问题,分析讨论了直摆头-转台式和斜摆头-转台式两种五坐标机床之间的数控加工程序互换求解算法。根据不同的机床结构,建立了机床坐标系之间的对应关系;基于机床自动跟踪模式下的数控加工程序后置处理和逆后置处理方法,提出了机床之间数控加工程序的互换算法;采用单步距走刀时间不变的控制方式,给出了加工进给速度的互换算法,实现了程序转换对工艺参数的继承。实际应用验证表明,该算法可有效解决直摆头与斜摆头五坐标机床数控加工程序之间的互换问题。     

Working towards the ideal laminar flow structure

Airlines and aircraft manufacturers are forecasting significant incerases in passenger traffic over the next 20 years (1), (2) but it is becoming increasingly apparent that, given a future scenario of increasing fuel costs and environmental controls, this is unlikely to be sustainable unless aircraft become more efficient and environmentally friendly than those in service today.Hybrid Laminar Flow (HLF) offers a significant contribution towards any overall efficiency improvement but requires relatively complex structures and systems leading to increases in weight, cost and maintenance. Since HLF has never been applied on a production basis, no mature manufacturing solution has evolved for the associated structure or systems. This paper reviews the requirements for HLF strutures and the progress made towards production solutions. It also recognises that the optimum structure may be influenced by the relative importance of fuel saving (or emissions reduction) compared with operating cost reductions.     

Analysis of APIAN high speed isolated test results - acoustics and aerodynamics

The APIAN programme (Advanced Propulsion Integration Aerodynamics and Noise) launched in 1996 under the coordination of AM Airbus follows GEMINI (1990–1993), and GEMINI II and SNAAP (1993–1996) and the huge advances achieved in 10 years show the large effort allowed by the European scientific community since the end of the 80s to understand propeller physics. This paper details the important experimental achievements of the isolated propeller test in the ONERA S1MA transonic facility; preliminary results of the installed S1MA test in ONERA S1MA are also shortly discussed.     

On the competition between Airbus and Boeing

The recent launch of the A380 is the culmination of the competition with Boeing, as Airbus completes its family of aircraft, in all classes from 100 seats up. This is a good occasion to review the preceding stages of the competition, up to the current A380, before presenting some short conclusions. It will be apparent in this exposition that Airbus has increased its market share at each stage because it has outperformed Boeing in incorporating technology advances in superior designs.     

Measurements of water vapour in the mesosphere with the spectral absorption line imager (SALI)

Water vapour concentration is one of the most important, yet one of the least known quantities of the mesosphere. Knowledge of water vapour concentration is the key to understanding many mesospheric processes, including the one that is primary focus of our investigation, Polar Mesospheric Clouds (PMC). The processes of formation and occurrence parameters of PMC constitute an interesting problem in their own right, but recent evidence had been provided which suggests that PMC are a critical indicator of climate change. In this context the feasibility of a low cost method of water vapour measurements using an instrument carried aloft by a sounding rocket has been examined and some of the results discussed. It is proposed to measure the strength of the 936nm water absorption line in a solar occultation configuration employing a CCD detector. This leads to the design of a small, low cost and low-mass instrument, which can be flown on a small rocket, of the type of the Orbital Sciences Corporation Viper 5. Alternatively the instrument can be flown as a “passenger” on larger rocket carrying other experiments. In either case flight costs are relatively low. Some performance simulations are presented showing that the instrument we have designed will be sufficiently sensitive to measure water vapor in concentrations that are expected at the summer mesopause, about 85 km height. Sufficient payload design work was carried out showing that the structural, thermal and electrical requirements for a flight on the Viper 5 rocket can be met and thus making the experiment feasible for a flight.     

Efficient and environmentally friendly aero-engine (EEFAE) targeted research action

Environmental issues, such as noise and exhaust gas emissions, will have a major impact upon the design and development of future-generation aircraft propulsion systems. The key objective of the European aero-engine industry is to strengthen competitiveness whilst ensuring that sustainable market growth is achieved with due consideration to environmental and safety issues. For this aim to be achieved, future aircraft gas turbine engines must provide increasing cycle performance at reduced weight (i.e. increased thrust-to-weight ratio) in order to minimise fuel consumption and consequently reduce emissions of greenhouse gasses. It is therefore vitally important that the European aero-engine industry is able to optimise its research and technology resources through an integrated approach.     

小卫星星务系统的遥测技术研究

阐述了小卫星采用的“可控式遥测”和“统一遥测”两种实现技术,即通过遥控、程控和自主控制实施对遥测的状态设置,控制遥测处理流向,改变遥测内容,构成智能化遥测,以增强遥测能力和灵活性。首次提出“二维帧”概念,将卫星的两种遥测标准：PCM遥测和分包遥测统一,实现两者的兼容和平滑过渡,有可能形成新的统一遥测系统标准。在设备级上,统一遥测与PCM遥测一致。在功能层面上,它与分包遥测一致。文章还提出“软件遥测”概念,企望于提升遥测性能。     

Integrated modular avionics

Over the past 20 years or so avionics have been designed using common standards and this has improved the quality and to some extent the interoperability of equipment. Yet aircraft systems are still a patchwork of one-off designs and the current thrust in Integrated Modular Avionics (IMA) is to address this issue.     

Development of the heat flow measurement system by the LUNAR-A penetrators

Lunar heat flow experiment is planned by using two LUNAR-A penetrators which will be deployed on the near-side and far-side of the lunar surface in 2000. Each penetrator has seven absolute and eleven relative temperature sensors. Impact experiments for real-size penetrator models onto a lunar-regolith analogue target confirmed that the sensors and electronics used in the Lunar-A Heat Flow Experiment can survive the shock loading expected during penetration of the penetrator in a lunar regolith. The calibration experiment demonstrates that the temperature sensors have a resolution of 0.01 degrees and that the thermal conductivity device have 10 % accuracy. In order to determine the heat flow value, we need a good thermal model and numerical simulation for the penetrator and the regolith which in turn requires accurate measurements of thermal properties of the penetrator's components. The current numerical models indicate that we will be able to obtain the lunar heat flow values within 20 to 30 percents in precision with this method.     

The Aurora project: A new sail layout

Aurora spacecraft is a scientific probe propelled by a “fast” solar sail whose first goal is to perform a technology assessment mission. The main characteristic of the sail is its low mass, which implies the absence of a plastic backing of the aluminum film and the lightness of the whole structure. In previous structural studies the limiting factor has been shown to be the elastic stability of a number of structural members subject to compressive loads. An alternative structural layout is here suggested: an inflatable beam, which is kept pressurized also after the deployment, relieves all compressive stresses, allowing a very simple configuration and a straightforward deployment procedure. However, as the mission profile requires a trajectory passing close to the Sun, a configuration different from the ‘parachute’ sail proposed in another paper, must be used.