四旋翼无人机建模及其四元数控制律设计

对四旋翼无人机进行建模与控制.在建模时采用了物理机理建模方法,尤其是对电机和螺旋桨进行了详细的建模,然后应用四元数对所建的模型进行了姿态角的控制.首先将欧拉角转换为四元数,然后求出误差四元数,接着由误差四元数推导出所要转动的角度和所要绕的轴.在此基础上,又对各个方向上的速度进行了控制,并与PID控制结果进行了对比.仿真结果表明,基于四元数的控制律更能有效地控制四旋翼速度较大的情况.     

Strapdown inertial navigation using dual quaternion algebra: error analysis

In a strapdown inertial navigation system (INS), the general displacement of a rigid body is traditionally separately modeled and analyzed, i.e., direction cosine matrix or quaternion for rotation analysis and vector for translation analysis. As a subsequent work of a companion paper (Wu et al., 2005), this paper adopts dual quaternion algebra, a most concise and unified mathematical tool for representing the general displacement of a rigid body, to analyze error characteristics of the strapdown INS. Two new error models in terms of quaternion algebra are developed: the additive dual quaternion error (ADQE) model and multiplicative dual quaternion error (MDQE) model. Both are expected to facilitate the future inertial navigation-based integrated navigation filter.     

`And we were tired': fatigue and aircrew errors

It is argued, on the basis information obtained by the NASA Aviation Safety Reporting System (ASRS), that the majority of errors made by aircrew members are cognitive errors, not control errors, and that a major contributing factor is fatigue. The ASRS incident reports indicate some aircrews often receive less than six hours of sleep, experience desynchronosis, and lack proper nutrition. The ways in which all these factors affect both individual performance and group (crew) performance are discussed     

Isolating errors in models of complex systems

One of the steps in creating a mathematical model of a system is to test the model after it has been fully specified, to see whether it is performing adequately. Often, it is found that the model is not performing acceptably (e.g. the model is not giving accurate predictions of the performance of the actual system). The same lack of fidelity can also be observed in established models that had been performing well, indicating a change in the actual system. At this point, it is necessary to diagnose where the problem in the model lies; a process called error isolation. An error isolation technique for detecting the misspecified parameter (or set of parameters) is described. This technique is especially designed for use on state-space models of large-scale systems. The authors report on an example of an application of the methodology to localizing errors in the model of an inertial navigation system     

Motion compensation errors: effects on the accuracy of airborne SAR images

This work addresses the study of the effect of residual uncompensated motion errors due to positioning measurement instrument and digital elevation model inaccuracies on the accuracy of airborne synthetic aperture radar (SAR) images. It is shown that these not only introduce phase errors following pure geometric considerations, but they also cause additional aberrations related to their interaction with the SAR processing procedure. Extension to the repeat pass airborne interferometry is also included to show their impact on the resulting interferograms.     

Application of GPS to space vehicles: analysis of space environmentand errors

GPS based systems become extremely competitive for space applications because of their all-weather capabilities and continual information on position, velocity, precise time and even attitude to increase mission effectiveness, reduce mission cost, minimize requirements of on-board devices. In this paper, space application environment and error sources have been systematically analyzed, including geometric location of user with GPS satellites, dynamic state, physical environment and the effects on positioning accuracy. Several special differential GPS technologies to space use are proposed     

IEEE 1394: a growing computer connectivity standard for automatedtest

This paper describes the latest trends in the IEEE 1394 (“firewire^TM” or “iLink^TM”) standards and why it is becoming the connectivity standard of choice for automatic test applications. Why move to IEEE 1394, what are the possible risks with doing so, what are some of the myths associated with IEEE 1394 and a practical example of an automatic test application will all be presented with the prime emphasis on giving the latest information that will help you get IEEE 1394 integrated into your automatic test system     

MLS: a total system approach

A typical approach and landing operation is described. The microwave landing system (MLS) is then examined, its design characteristics and how it works are shown, and how the MLS design fulfils the user's operational requirements by protecting the guidance signal from reflected signal interference is highlighted. MLS angle system accuracy is discussed in great detail, and its reliability, integrity, and coverage volume are briefly considered. MLS availability at any runway to all aircraft types and their landing scenarios, which is accomplished using narrow scanning beam antennas, is examined     

基于C/S架构的ERP中物流系统研制

介绍的是ERP系统中的物流子系统的开发过程，本系统前端采用Microsoft Visual Basic．net开发，后端利用SQL Server2000开发。系统采用了一种基于局域网的C／S为主体架构模式，以．NET与SQL SERVER2000中的．基于．NET数据库开发的DATASET思想，在具体实现中运用OLEDB控件与DATAGRID控件及T_SQL语句，用DataRelation对象来描述数据集中表问的关系。利用Toolbar控件与imagelist控件来实现主界面的设计。该系统是以一个合资企业为模型设计开发的物流信息管理系统。     

Software implemented transient fault detection in space computer

Computer systems operating in space environment are subject to different radiation phenomena, whose effects are often called “Soft Error”. Generally, these systems employ hardware techniques to address soft-errors, however, software techniques can provide a lower-cost and more flexible alternative. This paper presents a novel, software-only, transient-fault-detection technique, which is based on a new control flow checking scheme combined with software redundancy. The distinctive advantage of our approach over other fault tolerance techniques is the lower performance overhead with the higher fault coverage. It is able to cope with transient faults affecting data and the program control flow. By applying the proposed technique on several benchmark applications, we evaluate the error detection capabilities by means of several fault injection campaigns. Experimental results show that the proposed approach can detect more than 98% of the injected bit-flip faults with a mean execution time increase of 153%.     

Fast intelligent battery charging: neural-fuzzy approach

This paper focuses on the design of a super fast battery charger based on National's proprietary neural network based NeuFuz technology. In this application, we have used a NiCd battery pack as the test vehicle. However, this technology can be extended to other chemistries such as Ni-MH, Li-ion, etc. This technology allows the designer to accurately model the charge controller using a neural network, based on battery charge characteristics provided by the manufacturer. This approach continuously monitors the battery status, and modifies the charge current accordingly. It also eliminates the need for standard charge termination methods used in today's conventional chargers. The result is super fast charging in 20 to 30 minutes, and increased battery life. A low cost embedded controller (COP8) performs all the fuel-gauging and charge control functions by processing data obtained from the battery circuitry     

Real-time total system error estimation:Modeling and application in required navigation performance

In required navigation performance（RNP）, total system error（TSE） is estimated to provide a timely warning in the presence of an excessive error. In this paper, by analyzing the underlying formation mechanism, the TSE estimation is modeled as the estimation fusion of a fixed bias and a Gaussian random variable. To address the challenge of high computational load induced by the accurate numerical method, two efficient methods are proposed for real-time application, which are called the circle tangent ellipse method（CTEM） and the line tangent ellipse method（LTEM）,respectively. Compared with the accurate numerical method and the traditional scalar quantity summation method（SQSM）, the computational load and accuracy of these four methods are extensively analyzed. The theoretical and experimental results both show that the computing time of the LTEM is approximately equal to that of the SQSM, while it is only about 1/30 and 1/6 of that of the numerical method and the CTEM. Moreover, the estimation result of the LTEM is parallel with that of the numerical method, but is more accurate than those of the SQSM and the CTEM. It is illustrated that the LTEM is quite appropriate for real-time TSE estimation in RNP application.     

Analysis of array errors and a short-time processor in airbornephased array radars

Array errors are inherent in a realistic phased array radar system. The influence of array errors on the clutter degrees of freedom and the clutter subspace in an airborne phased array radar is analyzed. Based on the presented theoretic results, a method of short-time processing followed by coherent integration is proposed for clutter suppression in airborne phased array radars. It can approximate the two-dimensional optimal processor well even in the presence of array errors, clutter fluctuations and aircraft drift, with a considerable saving in computations     

X-Ray Spectroscopy of Galaxy Clusters: Beyond the CIE Modeling

X-ray spectra of galaxy clusters are dominated by the thermal emission from the hot intracluster medium. In some cases, besides the thermal component, spectral models require additional components associated, e.g., with resonant scattering and charge exchange. The latter produces mostly underluminous fine spectral features. Detection of the extra components therefore requires high spectral resolution. The upcoming X-ray missions will provide such high resolution, and will allow spectroscopic diagnostics of clusters beyond the current simple thermal modeling. A representative science case is resonant scattering, which produces spectral distortions of the emission lines from the dominant thermal component. Accounting for the resonant scattering is essential for accurate abundance and gas motion measurements of the ICM. The high resolution spectroscopy might also reveal/corroborate a number of new spectral components, including the excitation by non-thermal electrons, the deviation from ionization equilibrium, and charge exchange from surface of cold gas clouds in clusters. Apart from detecting new features, future high resolution spectroscopy will also enable a much better measurement of the thermal component. Accurate atomic database and appropriate modeling of the thermal spectrum are therefore needed for interpreting the data.     

实现程控化焊接两圆形管件的几何建模及计算方法

将圆形管件焊接成三通、四通等是焊接行业经常遇到的工艺。采用传统的手工式切割与焊接不仅工艺粗糙,而且效率也低。现代的焊接设备以其高效、自动化、程控化逐步取代手工操作。将提供各种形状的管件以不同连接形式焊接与切割以实现自动化、程控化的计算方法。     

Crew station measurement methodology: a quantitative approach

An investigation of the difficulties associated with analyzing the geometric constraints placed upon the human operator in a work setting was conducted. Many workstations, such as a cockpit, have limited data available for creating the CAD models required for human performance analysis. To create a model, a time-consuming, labor-intensive process of collecting measurement data by hand must be performed, resulting in a CAD model of questionable accuracy. In order to conduct accurate repeatable analysis, CAD data for all workstations must be collected quickly and in a standardized format. A demonstration project assessed the feasibility of using Coordinate Measuring Machine (CMM) technology to collect workstation geometry and create a CAD Model. Baseline data for comparing hand collection methods was derived from previous aircraft cockpit CAD modeling projects. This method involved approximately two weeks for data collection alone and another week to create the CAD model. The CMM technology was determined to be a cost-effective method for creating CAD models of aircraft cockpits. This technology substantially reduced the time required to build a high fidelity CAD model while significantly improving the accuracy of the data     

镍基单晶高温合金孔洞缺陷数值模拟与控制方法研究进展

镍基单晶高温合金是高性能航空发动机涡轮叶片的主要材料,其孔洞缺陷是影响涡轮叶片服役可靠性与耐久性的关键因素。常规试验分析手段往往只能获得定性规律,而多尺度数值模拟技术和三维形态表征技术的快速发展,为研究镍基单晶高温合金孔洞形成和演化机理以及精确预测孔洞缺陷的几何特征、分布方式和含量提供了条件。总结了国内外铸态孔洞、固溶孔洞和服役中孔洞缺陷形成与演化的数值模拟研究进展,评述了目前孔洞缺陷预测模型的使用条件和局限性,指出了从铸造到服役全流程孔洞演化与预测精确化、定量化研究所存在的问题,并展望了镍基单晶高温合金孔洞缺陷多尺度数值模拟技术的发展方向。     

Issues in human/computer control of dexterous remote hands

Much research on dexterous robot hands has been aimed at the design and control problem associated with their autonomous operation, while relatively little research has addressed the problem of direct human control. While many of the issues in mixed computer/human control of dexterous hands parallel those found in supervisory control of traditional remote manipulators, the unique geometry and capabilities of dexterous hands pose many new problems. Among these are the control of redundant degrees of freedom, grasp stabilization and specification of nonanthromorphic behavior. An overview is presented of progress made at the MTI AI Laboratory in control of the Salisbury three-finger hand, including experiments in grasp planning and manipulation by controlled slip. The author also suggests how it might be possible to introduce human control into the process at a variety of functional levels     

仿真概念模型的需求获取

概念模型的需求获取关系到仿真模型的质量和仿真实现的成败。文章针对概念建模中需求获取方面的问题,分析了需求获取一般包含的内容,形成过程,表现的技术方法,并将其应用于一个简单的综合防空想定。