Thermodynamic Characteristic Study of a High-temperature Flow-rate Control Valve for Fuel Supply of Scramjet Engines

Thermodynamic characteristics are of great importance for the performance of a high-temperature flow-rate control valve,as high-temperature environment may bring problems,such as blocking of spool and increasing of leakage,to the valve.In this paper,a high-temperature flow-rate control valve,pilot-controlled by a pneumatic servo system is developed to control the fuel supply for scramjet engines.After introducing the construction and working principle,the thermodynamic mathematical models of the valve are built based on the heat transfer methods inside the valve.By using different boundary conditions,different methods of simulations are carried out and compared.The steady-state and transient temperature field distribution inside the valve body are predicted and temperatures at five interested points are measured.By comparing the simulation and experimental results,a reasonable 3D finite element analysis method is suggested to predict the thermodynamic characteristics of the high-temperature flow-rate control valve.     

An improved multiple model GM-PHD filter for maneuvering target tracking

In this paper, an improved implementation of multiple model Gaussian mixture probability hypothesis density (MM-GM-PHD) filter is proposed. For maneuvering target tracking, based on joint distribution, the existing MM-GM-PHD filter is relatively complex. To simplify the filter, model conditioned distribution and model probability are used in the improved MM-GM-PHD filter. In the algorithm, every Gaussian components describing existing, birth and spawned targets are estimated by multiple model method. The final results of the Gaussian components are the fusion of multiple model estimations. The algorithm does not need to compute the joint PHD distribution and has a simpler computation procedure. Compared with single model GM-PHD, the algorithm gives more accurate estimation on the number and state of the targets. Compared with the existing MM-GM-PHD algorithm, it saves computation time by more than 30%. Moreover, it also outperforms the interacting multiple model joint probabilistic data association (IMMJPDA) filter in a relatively dense clutter environment.     

Partition method for improvement of piecewise linear model with full envelope covered

Since ambient conditions vary in a wide range within the full flight envelope, the existing piecewise linear model (PLM), which is based on sea-level static condition with use of corrected parameters for other points in the flight envelope, cannot meet the accuracy for replacing the nonlinear model. To obtain more accurate linear models, a method of partitioning the flight envelope over a grid of Mach number and altitude boxes was suggested. Then, a set of linear models for a given operating condition was selected by picking the nearest (Mach number, altitude) box in the flight envelope. Through the selected set of linear models, interpolating for power level based on a weighted sum of corrected rotor speeds can obtain a linear model with acceptable accuracy. Simulation results of different points within the full flight envelope showed that the maximum error between nonlinear model and the existing PLM was more than 50%, while the maximum error between nonlinear model and the improved PLM was within 8%. It is concluded that the improved PLM performs accurately, especially under the non-standard conditions. In addition, the improved PLM can satisfy the real-time requirement better than the existing PLM.      

Fuzzy adaptive robust control for space robot considering the effect of the gravity

Space robot is assembled and tested in gravity environment, and completes on-orbit service（OOS） in microgravity environment. The kinematic and dynamic characteristic of the robot will change with the variations of gravity in different working condition. Fully considering the change of kinematic and dynamic models caused by the change of gravity environment, a fuzzy adaptive robust control（FARC） strategy which is adaptive to these model variations is put forward for trajectory tracking control of space robot. A fuzzy algorithm is employed to approximate the nonlinear uncertainties in the model, adaptive laws of the parameters are constructed, and the approximation error is compensated by using a robust control algorithm. The stability of the control system is guaranteed based on the Lyapunov theory and the trajectory tracking control simulation is performed. The simulation results are compared with the proportional plus derivative（PD） controller, and the effectiveness to achieve better trajectory tracking performance under different gravity environment without changing the control parameters and the advantage of the proposed controller are verified.     

基于多Agent的舰载机弹射起飞仿真层次模型(英文)

With the aid of multi-agent based modeling approach to complex systems, the hierarchy simulation models of carrier-based aircraft catapult launch are developed. Ocean, carrier, aircraft, and atmosphere are treated as aggregation agents, the detailed components like catapult, landing gears, and disturbances are considered as meta-agents, which belong to their aggregation agent. Thus, the model with two layers is formed i.e. the aggregation agent layer and the meta-agent layer. The information communication among all agents is described. The meta-agents within one aggregation agent communicate with each other directly by information sharing, but the meta-agents, which belong to different aggregation agents exchange their information through the aggregation layer first, and then perceive it from the sharing environment, that is the aggregation agent. Thus, not only the hierarchy model is built, but also the environment perceived by each agent is specified. Meanwhile, the problem of balancing the independency of agent and the resource consumption brought by real-time communication within multi-agent system （MAS） is resolved. Each agent involved in carrier-based aircraft catapult launch is depicted, with considering the interaction within disturbed atmospheric environment and multiple motion bodies including carrier, aircraft, and landing gears. The models of reactive agents among them are derived based on tensors, and the perceived messages and inner frameworks of each agent are characterized. Finally, some results of a simulation instance are given. The simulation and modeling of dynamic system based on multi-agent system is of benefit to express physical concepts and logical hierarchy clearly and precisely. The system model can easily draw in kinds of other agents to achieve a precise simulation of more complex system. This modeling technique makes the complex integral dynamic equations of multibodies decompose into parallel operations of single agent, and it is convenient to expand, maintain, and reuse the pro     

A Fault Sample Simulation Approach for Virtual Testability Demonstration Test

Virtual testability demonstration test has many advantages,such as low cost,high efficiency,low risk and few restrictions.It brings new requirements to the fault sample generation.A fault sample simulation approach for virtual testability demonstration test based on stochastic process theory is proposed.First,the similarities and differences of fault sample generation between physical testability demonstration test and virtual testability demonstration test are discussed.Second,it is pointed out that the fault occurrence process subject to perfect repair is renewal process.Third,the interarrival time distribution function of the next fault event is given.Steps and flowcharts of fault sample generation are introduced.The number of faults and their occurrence time are obtained by statistical simulation.Finally,experiments are carried out on a stable tracking platform.Because a variety of types of life distributions and maintenance modes are considered and some assumptions are removed,the sample size and structure of fault sample simulation results are more similar to the actual results and more reasonable.The proposed method can effectively guide the fault injection in virtual testability demonstration test.     

非线性非高斯模型的高斯和PHD滤波算法(英文)

A new multi-target filtering algorithm, termed as the Gaussian sum probability hypothesis density （GSPHD） filter, is proposed for nonlinear non-Gaussian tracking models. Provided that the initial prior intensity of the states is Gaussian or can be identified as a Gaussian sum, the analytical results of the algorithm show that the posterior intensity at any subsequent time step remains a Gaussian sum under the assumption that the state noise, the measurement noise, target spawn intensity, new target birth intensity, target survival probability, and detection probability are all Gaussian sums. The analysis also shows that the existing Gaussian mixture probability hypothesis density （GMPHD） filter, which is unsuitable for handling the non-Gaussian noise cases, is no more than a special case of the proposed algorithm, which fills the shortage of incapability of treating non-Gaussian noise. The multi-target tracking simulation results verify the effectiveness of the proposed GSPHD.     

Changing law of launching pitching angular velocity of rotating missile

In order to provide accurate launching pitching angular velocity（LPAV） for the exterior trajectory optimization design, multi-flexible body dynamics（MFBD） technology is presented to study the changing law of LPAV of the rotating missile based on spiral guideway. An MFBD virtual prototype model of the rotating missile launching system is built using multi-body dynamics modeling technology based on the built flexible body models of key components and the special force model.The built model is verified with the frequency spectrum analysis. With the flexible body contact theory and nonlinear theory of MFBD technology, the research is conducted on the influence of a series of factors on LPAV, such as launching angle change, clearance between launching canister and missile,thrust change, thrust eccentricity and mass eccentricity, etc. Through this research, some useful values of the key design parameters which are difficult to be measured in physical tests are obtained. Finally,a simplified mathematical model of the changing law of LPAV is presented through fitting virtual test results using the linear regression method and verified by physical flight tests. The research results have important significance for the exterior trajectory optimization design.     

A compositional method to model dependent failure behavior based on PoF models

In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a deterministic model, rather than a probabilistic one, can be established. Three steps comprise the developed method. First, physics-of-failure(PoF) models are utilized to model each failure mechanism. Then, interactions among failure mechanisms are modeled as a combination of three basic relations, competition, superposition and coupling. This is the reason why the method is referred to as ‘‘compositional method". Finally, the PoF models and the interaction model are combined to develop a deterministic model of the dependent failure behavior. As a demonstration, the method is applied on an actual spool and the developed failure behavior model is validated by a wear test. The result demonstrates that the compositional method is an effective way to model dependent failure behavior.     

液压放大式超磁致伸缩直驱式伺服阀的设计与实验

研制了一种基于液压式微位移放大机构的超磁致伸缩直驱式电液伺服阀,在保证较大体积流量的前提下,提高了直驱式电液伺服阀的频响.采用弹性力学理论、有限元和计算流体力学(CFD)方法对直驱式电液伺服阀进行了结构设计和分析,并制作了超磁致伸缩直驱阀样机,在AMESim下建立其磁-机-液耦合模型.仿真和试验表明:所设计的超磁致伸缩直驱阀的频响超过100Hz和系统油压21MPa下的负载体积流量达到30L/min.      

考虑气穴影响的2D压力伺服阀稳定性

为研究双自由度（2D）压力伺服阀工作时的气穴现象对阀芯稳定性的影响，利用AMESim中的基本库和HCD库建立2D压力伺服阀各组件仿真模型。理论分析得出气穴现象会降低阀体中含气油液的有效体积弹性模量，得出考虑气穴影响的阀芯稳定性条件。仿真结果表明气穴现象会导致主阀芯到达稳定位置后出现振荡现象，影响主阀芯的穿越频率从21 Hz降低至6 Hz，限制主阀芯的频宽，适当增加主阀芯阻尼比能提高主阀芯工作稳定性。提出一种新型阻尼活塞结构，建立模型分析得出其能在不影响伺服阀频响、阀芯位移和抗污染能力情况下提高主阀芯阻尼比以提高阀芯工作稳定性，并且设计实验进行验证。实验结果表明，应用阻尼活塞将2D压力伺服阀压力输出波动从9%降低至2%，能够提高飞行器制动时刹车阀工作稳定性。     

加力燃油计量装置的AMESim 仿真研究

为获得加力燃油系统数字化仿真与性能验证平台,采用功能划分的方法分析了典型计量装置的功能模块,确定了伺服阀-随动活塞、计量活门-等压差活门是决定计量装置动态特性的主要组成部分,对其进行了数学建模。鉴于获得的数学模型描述系统特性时缺乏相关元件特性参数的设计依据,建立了由计量活门、等压差活门、电液伺服单元等组成计量装置的AMESim模型,计算主要结构参数后仿真分析了其稳态和动态特性。结果表明:基于控制系统构成的加力燃油计量装置功能划分与数学建模可为仿真研究与参数设计提供指导,AMESim可用于动态过程仿真与性能预测。     

航空发动机电液伺服系统机载模型监控设计

为了监控航空发动机电液伺服系统中不易通过机内测试电路诊断的异常或故障,提出一种机载模型监控方法,采用AMESim工具进行系统的建模,之后对模型进行校准、实时化和线性化处理。在对监控算法进行了设计与仿真之后,用C代码编程实现了模型监控算法,并运行于发动机电子控制器中。对某发动机燃油计量装置的试验表明:机载模型监控可以有效监测系统中因元部件性能衰减、卡滞、零偏漂移等引起的异常或故障,并能补偿电液伺服阀的零偏漂移和容错运行,避免控制功能失效或过快降级。可为航空发动机及相关领域的电液伺服系统机载模型监控设计提供参考。     

弱可压缩流体与可压缩流体模型的管路水击研究

为提升液体推进系统模型对可压缩流体的仿真能力,针对供应管路的瞬变流动,采用一维有限体积法,使用Modelica语言基于MWorks平台分别开发了适用于补燃循环发动机仿真模型库的弱可压缩流体与可压缩流体的管路模型,不同于控制方程中显含声速的弱可压缩流体模型,可压缩流体模型通过将守恒方程与真实流体的SRK型状态方程耦合求解来计算压力波的传播。在管路供应系统中,分别以液氢、液氧及液甲烷为工质进行关阀水击的仿真研究,结果表明:使用SRK状态方程避免了可压缩流体模型对内能拟合公式的依赖,减轻了建模难度;可压缩流体模型对液氧及液甲烷的仿真结果较为准确,最大误差不超过2%,对液氢的最大计算误差约9%;相对于可压缩流体模型,弱可压缩流体模型计算得到的水击压力在振幅及频率上均偏大;可压缩流体模型计算得到的流体密度波动不超过3%,因此工程实践中处理水击问题时将液体假设为弱可压具有一定的合理性。     

步进电机驱动的燃油计量装置建模与仿真

为了开发数控燃油计量装置独立仿真平台,利用AMESet建立了基于C代码的步进电机部件模型;对建立的步进电机模型进行仿真,获得了其转角随输入脉冲的关系。建立了由计量活门、等压差活门、增压活门等组成的燃油计量装置机械液压组件AMESim模型,将开发的步进电机模型与计量装置各液压组件模型联结,实现了步进电机驱动的数控燃油计量装置面向对象的建模。仿真结果表明：在正常工作范围内,仿真结果与设计参考偏差在5%以内,所开发的AMESim模型能满足该数控计量装置的稳态和动态特性的研究要求。     

射流管式伺服阀冲蚀磨损特性

射流管式伺服阀是一种典型的两级流量控制电液伺服阀,其喷嘴至接收器部位的流场最复杂,会因液压介质的污染而产生冲蚀磨损。以射流管式伺服阀为研究对象,将计算流体力学(CFD)理论与冲蚀磨损理论相结合,应用雷诺平均Navier-Stokes方程、标准k-ε两方程模型(液相)、离散相模型(DPM)(固相)和塑性材料冲蚀磨损模型,通过流体动力学软件FLUENT建立射流管式伺服阀喷嘴至接收器部位的可视化仿真模型,并进行了冲蚀磨损率的数值模拟和理论寿命的计算。研究结果表明:液压介质中的固体颗粒对射流管式伺服阀的冲蚀磨损主要集中于左右接收孔所夹中间内壁区域,磨损率最大值随喷嘴偏移量的增加而减小且此趋势左右对称。研究方法和结果对于射流管式伺服阀故障的定性分析、预测和理论寿命的定量计算具有重要参考价值。     

磁悬浮斜翼节静动态特性

作为直动式电-机械转换器和二维阀本体之间的连接桥梁，反馈放大机构起着位置反馈、运动转换和推力放大的重要作用。但现有二维伺服比例阀的机械式反馈放大机构都存在摩擦磨损等非线性环节，对阀的静态特性影响明显。基于永磁悬浮技术提出一种新型的无接触式磁悬浮斜翼节，其依靠磁斥力将斜翼动子和阀芯悬浮在中位，同时实现位置反馈和运动转换功能，以彻底去除传统机械式反馈放大机构由于接触带来的摩擦磨损等因素对阀控制特性的不利影响。首先基于电磁场理论建立了磁悬浮斜翼节的数学解析模型，讨论了关键结构参数对磁力矩的影响；随后在Maxwell和Adams平台上分别对其静动态特性进行了基于有限元模拟和多体运动学分析的参数优化，在此基础上制作了实验样机，搭建实验台架研究了斜翼节的静动态特性，从而验证了其工程实用性。仿真和实验结果基本相符，3种验证的斜翼节样机中，当外接比例电磁铁推动外动子移动3 mm时，最大磁力矩可达到0.252 N·m，阶跃响应时间约120 ms。参数化设计表明减小工作气隙和增加斜翼节倾角均能提升斜翼节的磁力矩和动态响应，而在气隙中添加磁流体可提升磁力矩，但同时影响阶跃响应。研究工作对于后续磁悬浮斜翼节在二维伺服比例阀上的实际应用具有重要的参考价值。     

AMESim仿真技术在高速电磁阀中的应用

以某型航空发动机电子控制系统中的高速电磁阀为研究对象,针对建模仿真问题进行了研究.分析了高速电磁阀工作原理,运用AMESim建模仿真平台,建立了高速电磁阀较为精确的数学模型,并对所建模型的占空比-流量特性进行仿真分析,与该型电磁阀试验数据进行比较,分析所建数学模型的精度及准确性.仿真结果表明:所建高速电磁阀数学模型的占空比-流量特性误差保持在8%以内,能够满足产品所规定的精度要求.      

一种电液伺服系统非线性补偿方法

分析了一类电液伺服阀的中立位非线性特征及其对电液伺服系统的影响,提出了一种非线性补偿方法。根据电液伺服阀的非线性特性,推导出补偿方法的函数并且进行计算,结合传统的PID控制获得具有非线性特征的补偿控制器。以某型电液伺服阀和液压缸组成的电液伺服系统为例,进行仿真与分析。仿真结果表明提出的方法具有较好的补偿作用,能够减少电液伺服阀非线性对电液伺服系统的影响。