Geometric error analysis of an over-constrained parallel tracking mechanism using the screw theory

This paper deals with geometric error modeling and sensitivity analysis of an overconstrained parallel tracking mechanism. The main contribution is the consideration of overconstrained features that are usually ignored in previous research. The reciprocal property between a motion and a force is applied to tackle this problem in the framework of the screw theory. First of all, a nominal kinematic model of the parallel tracking mechanism is formulated. On this basis, the actual twist of the moving platform is computed through the superposition of the joint twist and geometric errors. The actuation and constrained wrenches of each limb are applied to exclude the joint displacement. After eliminating repeated errors brought by the multiplication of wrenches, a geometric error model of the parallel tracking mechanism is built. Furthermore,two sensitivity indices are defined to select essential geometric errors for future kinematic calibration. Finally, the geometric error model with minimum geometric errors is verified by simulation with SolidWorks software. Two typical poses of the parallel tracking mechanism are selected, and the differences between simulation and calculation results are very small. The results confirm the correctness and accuracy of the geometric error modeling method for over-constrained parallel mechanisms.     

A formal approach using SysML for capturing functional requirements in avionics domain

In this work, a Model-Based Systems Engineering approach based on SysML is proposed. This approach is used for the capture and the definition of functional requirements in avionics domain. The motivation of this work is triple: guide the capture of functional requirements, validate these functional requirements through functional simulation, and verify efficiently the consistency of these functional requirements. The proposed approach is decomposed into several steps that are detailed to go from conceptual model of avionics domain to a formal functional model that can be simulated in its operating context. To achieve this work, a subset of SysML has been used as an intermediate modelling language to ensure progressive transformation that can be understood and agreed by system stakeholders. Formal concepts are introduced to ensure theoretical consistency of the approach. In addition, transformation rules are defined and the mappings between concepts of ARP4754A civil aircraft guidelines and SysML are formalized through meta-model. The resulting formalization enables engineers to perform functional simulation of the top-level functional architecture extracted from operational scenarios. Finally, the approach has been tested on an industrial avionics system called the Onboard Maintenance System.     

EWIS 数字化设计技术分析

针对EWIS数字化设计技术的需求,利用CHS软件建立模型库,通过CATIA三维建模和ANSYS数字仿真等方法,提高EWIS研制效率和保证产品的准确性,降低成本,缩短研制周期。对EWIS数字化设计技术的应用提供了指导意见。     

适用于飞机结冰适航取证加速的分析验证/取证思路

飞机结冰问题研究目前主要有3大手段:数值模拟、风洞试验和飞行试验。这3大手段有着各自的局限性,其中,又以飞行试验最为耗费时间和资金。文中总结了机结冰相关研究方法现状,分析了各种方法的优势与局限性,介绍了模拟分析方法(Certification/Qualification by Analysis,CQbA)方法,给出了可用于CQbA相关工作的软件和设备简介。CQbA方法主要以数值模拟和风洞试验相结合的形式进行研究,强调各方法自身优点的协同关系,进行飞机结冰问题的研究和适航相关结果的认证,以实现高效、经济的研究过程。     

自由飞模型仿真建模与缩比控制律设计技术

从试验相似准则出发,全面分析了自由飞模型与全尺寸飞机基本参数、模态特性、飞行动力学特性,以及飞行控制律的相似关系,并以某型飞机为研究对象,利用 MATLAB/Simulink 平台建立了全尺寸飞机与自由飞模型的非线性仿真模型,根据典型控制框架设计了缩比控制律。通过仿真试验验证了两者动力学特性相似关系,最后通过无动力模型自由飞投放试验进行试飞验证。仿真和试飞结果表明,自由飞模型仿真建模和缩比控制律设计方法正确可行,利用自由飞模型试验技术开展控制律演示验证优势明显。     

飞机冲压空气涡轮系统的动态特性分析

冲压空气涡轮是飞机能源失效时使用的关键应急系统。首先依据冲击空气涡轮（RAT）工作原理确定其物理架构;然后对涡轮部件、能源转换装置、展开装置和展开随动机构等4个主要部件进行力学分析,建立各部件的力学方程组。依据该力学方程组,建立涉及力学、液压、刚体动力学的多学科冲压空气涡轮系统模型。使用该模型仿真了某真实系统在不同工况和设计参数下的动态特性,研究了关键设计参数对系统性能的影响,为冲压空气涡轮系统正向设计提供依据。最终,某型冲压空气涡轮系统风洞试验数据验证了所提系统模型的准确性。     

航空电子产品电磁环境效应模块化设计方法

对高强度辐射场（HIRF）环境特点与干扰类型进行分析,采用理论计算、计算机仿真技术（CST）的仿真分析及实测等方法分别对某型飞机航空电子系统综合显示单元的外部强电磁辐射场孔缝耦合、场线耦合及芯片前端电路影响关键芯片的相关规律进行了研究,给出了相关设计建议。结果表明,可通过分析孔缝、场线耦合获得进入关键芯片前端电路的电磁干扰能量,再结合关键芯片前端电路网络对干扰的插入损耗分析,获得关键芯片在外部强场激励下的感应电压。     

风洞试验数据资源集成平台设计

风洞试验过程中,产生的海量试验数据是宝贵的资源。为高效管理试验数据、建立健全数据架构、提高试验数据安全性和规范性,设计了风洞试验数据资源集成平台。该平台功能完备,利用风洞试验数据资源和成熟的数据库技术对试验数据进行关联、组织、存储及展示,为风洞试验数据辅助分析、绘图等专业性分析及应用提供数据支持。本文介绍的风洞试验数据资源集成平台整体设计方案及关键技术研究,对系统设计与应用进行了详细描述。     

飞机热管理系统动态仿真

为解决飞机热源散热需求大、可用热沉不足的矛盾,提出了一种热管理系统仿真方法.从飞行全过程的角度开展热管理系统方案研究,同时采用C++与AMESim软件,开发了燃油和环控分系统仿真模型,构建了热管理系统动态仿真平台,完成系统仿真.有效地分析了给定飞行剖面条件下,各子系统耦合后的动态变化特性,实时预测设备、散热器、各油箱的...     

Solar sailing in realistic mode,based on a locally-optimal control laws

Ballistic design of solar sailing missions in the solar system is composed of defining the design parameters, the control programs, and the trajectories that provide performance goals of a flight. The use of a solar sail spacecraft imposes specific restrictions on mission parameters that include the degradation limit on the flight duration, the maximum temperature of solar sail's surface, the minimum distance from the Sun, the maximum angular velocity of the spacecraft's rotation and others.Many authors considered the impact of these restrictions on the design of the mission separately, but they used a sophisticated method of finding the exact optimal motion control or applied the most straightforward laws of motion control. This paper uses local-optimal control laws at the complete mathematical models of motion and functioning of solar sail spacecraft to describe a technique of designing interplanetary missions. The described method avoids the need to obtain an accurate optimal solution to the control problem and does not cause significant computational difficulties.