Performance evaluation of multi-sensor data-fusion systems in launch vehicles

In this paper, the utilization of multi-sensors of different types, their characteristics, and their data-fusion in launch vehicles to achieve the goal of injecting the satellite into a precise orbit is explained. Performance requirements of sensors and their redundancy management in a typical launch vehicle are also included. The role of an integrated system level-test bed for evaluating multi-sensors and mission performance in a typical launch vehicle mission is described. Some of the typical simulation results to evaluate the effect of the sensors on the overall system are highlighted     

道路交叉口不同控制方式交通噪声预测

以不同行驶状态的机动车噪声排放模型为基础，对三种典型控制方式下的交叉口噪声进行预测研究。采用实验的方法分别对大、中、小型单辆车在怠速、匀速、加速、减速等各种行驶状态下的噪声值进行测定，通过回归分析得到不同行驶状态下的机动车噪声排放模型，并以某信号控制交叉口的实测数据为例，用计算机仿真的方法证明该模型对于交叉口噪声模拟的较高适用性。进而将该排放模型应用于信号控制、无信号控制以及环形等控制方式的交叉口进行噪声预测，通过不同交通流量时交叉口的平均噪声级以及噪声的分布情况等对比，得到各种控制方式下交叉口噪声的若干特点和区别。     

Development of navigation guidance and control technology for Indian launch vehicles

The orbital injection accuracy of any payload depends on the calibre of the inertial guidance system used on board the launch vehicle. This paper outlines the mission definition and the rationale for the selection of a proper guidance system to meet final mission objectives. The functions and the architecture of the navigation, guidance and control are discussed. The developmental aspects of the sophisticated inertial sensors, inertial systems, associated complex electronics, on-board computers, control actuators and systems are reported. The complexity of the on-board control and guidance software and the test and evaluation procedures used for their validation are included. The general scheme of the inertial guidance systems and the critical role played by them in the realization of Indian satellite launch vehicles SLV-3, ASLV and PSLV are presented in brief.     

有限元仿真方法评价护栏安全性能的可行性

建立多种车辆和护栏有限元仿真模型,运用多次碰撞试验数据对仿真模型计算结果进行比对,对采用有限元仿真方法评价护栏安全性能的可行性进行分析。研究结果表明,仿真计算可以得到车辆行驶轨迹、结构防护导向、乘员风险和动态变形等护栏安全评价的各项指标,仿真结果与试验结果一致,误差在10%以内,验证了建模方法的正确性,运用有限元仿真方法评价护栏安全性能具有较高可行性。强调运用评价护栏安全性能的仿真模型须通过碰撞试验校核,同时建议通过法规和准则对从事护栏评价CAE工程师进行职业管理。     

Phased mission modelling of systems with maintenance-free operating periods using simulated Petri nets

A common scenario in engineering is that of a system which operates throughout several sequential and distinct periods of time, during which the modes and consequences of failure differ from one another. This type of operation is known as a phased mission, and for the mission to be a success the system must successfully operate throughout all of the phases. Examples include a rocket launch and an aeroplane flight. Component or sub-system failures may occur at any time during the mission, yet not affect the system performance until the phase in which their condition is critical. This may mean that the transition from one phase to the next is a critical event that leads to phase and mission failure, with the root cause being a component failure in a previous phase. A series of phased missions with no maintenance may be considered as a maintenance-free operating period (MFOP). This paper describes the use of a Petri net (PN) to model the reliability of the MFOP and phased missions scenario. The model uses Monte-Carlo simulation to obtain its results, and due to the modelling power of PNs, can consider complexities such as component failure rate interdependencies and mission abandonment. The model operates three different types of PN which interact to provide the overall system reliability modelling. The model is demonstrated and validated by considering two simple examples that can be solved analytically.     

Simulation analysis of dispatching rules for an automated interbay material handling system in wafer fab

Here, the performance evaluation of a double-loop interbay automated material handling system (AMHS) in wafer fab was analysed by considering the effects of the dispatching rules. Discrete event simulation models based on SIMPLE++ were developed to implement the heuristic dispatching rules in such an AMHS system with a zone control scheme to avoid vehicle collision. The layout of an interbay system is a combination configuration in which the hallway contains double loops and the vehicles have double capacity. The results show that the dispatching rule has a significant impact on average transport time, waiting time, throughput and vehicle utilization. The combination of the shortest distance with nearest vehicle and the first encounter first served rule outperformed the other rules. Furthermore, the relationship between vehicle number and material flow rate by experimenting with a simulation model was investigated. The optimum combination of these two factors can be obtained by response surface methodology.     

基于预瞄技术的汽车磁流变半主动悬架控制方法

在综合利用磁流变减振器控制电流与输出阻尼力的关系、以及轴距预瞄控制技术的基础上,提出汽车磁流变半主动悬架预瞄控制方法,通过理论分析和计算机仿真,研究在不同行驶速度下汽车磁流变半主动悬架动态性能,实验表明,该法具有提高悬架系统的控制性能,使悬架承受的冲击响应小、振动强度低和汽车行驶平顺性好等特点.     

Multidisciplinary design and optimization of an air launched satellite launch vehicle using a hybrid heuristic search algorithm

A multidisciplinary design and optimization strategy for a multistage air launched satellite launch vehicle comprising of a solid propulsion system to low earth orbit with the implementation of a hybrid heuristic search algorithm is proposed in this article. The proposed approach integrated the search properties of a genetic algorithm and simulated annealing, thus achieving an optimal solution while satisfying the design objectives and performance constraints. The genetic algorithm identified the feasible region of solutions and simulated annealing exploited the identified feasible region in search of optimality. The proposed methodology coupled with design space reduction allows the designer to explore promising regions of optimality. Modules for mass properties, propulsion characteristics, aerodynamics, and flight dynamics are integrated to produce a high-fidelity model of the vehicle. The objective of this article is to develop a design strategy that more efficiently and effectively facilitates multidisciplinary design analysis and optimization for an air launched satellite launch vehicle.     

AUV水下对接系统设计与接驳控制方案研究

为了实现自主水下机器人（autonomous underwater vehicle,AUV）稳定、准确、高效地完成水下对接,提出一种导向罩开合式水下对接装置。针对该装置对接结构的特征所决定的AUV入坞运动的控制要求,考虑到在入坞阶段前向运动起主导作用,分别建立了在静对接、悬浮对接和拖曳动对接三种应用场景下AUV对接系统的动力学仿真模型,重点分析了AUV对接系统在对接时受到的水动力和碰撞力。基于ADAMS （automatic dynamic analysis of mechanical system,机械系统动力学自动分析）和控制仿真软件MATLAB/Simulink联合搭建的水下对接仿真系统,进行在不同接驳控制方案下静对接、悬浮对接和拖曳动对接效果的仿真分析与对比。分析结果表明：在位置-速度闭环控制下,对接能耗、碰撞次数和最大碰撞力均为最小,对接耗时比传统的位置闭环控制减少约50%;在拖曳动对接场景下,在位置-速度闭环控制下对接系统实现了良好的变速跟踪,有利于AUV快速对接。该AUV水下对接系统适用于不同的对接场景,方便无人艇搭载并对AUV进行布放与回收,有利于革新海洋无人系统跨域协同作业模式。     

航箭发控系统虚拟检测仪研制

针对现有的航箭发控系统检测仪可靠性低、灵活性差等缺点,设计新型航箭发控系统虚拟检测仪,给出检测仪的硬件组成和软件设计。该仪器以IPC-610型工业控制计算机为核心,采用VC++编程,综合运用标准接口及总线技术、故障检测技术、FIFO技术等,能够有效地提高仪器的可靠性和灵活性。     

Performance evaluation of an auction-based manufacturing system using coloured Petri nets

The next generation of manufacturing systems is assumed to be intelligent enough to make decisions and automatically adjust to variations in production demand, shop-floor breakdowns etc. Auction-based manufacturing is a control strategy in which various intelligent entities in the manufacturing system bid themselves, accept bids and make selections among the bids available based on a heuristic. This paper deals with the simulation modelling and performance evaluation of a push-type auction (negotiation) based manufacturing system embedded in a pulltype production system using coloured Petri nets. Three different models of an auction-based manufacturing system have been discussed. This methodology helps in developing systems for real-time control, anticipation of deadlocks, and evaluation of various performance metrics like machine utilization, automated guided vehicle (AGV) utilization, waiting times, work in process (WIP) etc. Various decision-making rules were identified for the real-time control of auction-based manufacturing systems.     

一个计算机病毒传播数学模型的建立与研究

基于流行病数学模型的建模方法,建立了一个对等网中的关于计算机病毒传播的时滞微分方程模型,模型中考虑了计算机病毒的潜伏期与反病毒技术出现时间。利用微分动力系统理论研究了单种计算机病毒的传播规律,得到了病毒是否消除的阈值。最后对论文结果进行了讨论与数值模拟。论文的研究成果为计算机病毒控制提供理论基础。     

某多管火箭炮车炮刚柔耦合极限路况行驶动力学研究

采用刚柔耦合的方法,对某新型车载防空多管火箭炮进行了通过垂直凸台、水平壕沟、陡坡等极限路况的行驶动力学仿真研究.建立了越野车与防空多管火箭炮的刚柔耦合动力学模型,并考虑轮胎的作用,计算了越野车前后轮通过垂直凸台的极限高度和水平壕沟的极限宽度,建立各种极限路况的计算模型,对车载防空多管火箭炮进行了行驶动力学仿真,得到全系...     

Genetic algorithms and Monte Carlo simulation for optimal plant design

We present an approach to the optimal plant design (choice of system layout and components) under conflicting safety and economic constraints, based upon the coupling of a Monte Carlo evaluation of plant operation with a Genetic Algorithms-maximization procedure. The Monte Carlo simulation model provides a flexible tool, which enables one to describe relevant aspects of plant design and operation, such as standby modes and deteriorating repairs, not easily captured by analytical models. The effects of deteriorating repairs are described by means of a modified Brown–Proschan model of imperfect repair which accounts for the possibility of an increased proneness to failure of a component after a repair. The transitions of a component from standby to active, and vice versa, are simulated using a multiplicative correlation model. The genetic algorithms procedure is demanded to optimize a profit function which accounts for the plant safety and economic performance and which is evaluated, for each possible design, by the above Monte Carlo simulation.In order to avoid an overwhelming use of computer time, for each potential solution proposed by the genetic algorithm, we perform only few hundreds Monte Carlo histories and, then, exploit the fact that during the genetic algorithm population evolution, the fit chromosomes appear repeatedly many times, so that the results for the solutions of interest (i.e. the best ones) attain statistical significance.     

Multidisciplinary approach to materials selection for bipropellant thrusters using ablative and radiative cooling

Reduction of costs is a main consideration in every space mission, and propulsion system is an important subsystem of those missions where orbital maneuvers are considered. Lighter propulsions with higher performance are necessary to reduce the mission costs. Bipropellant propulsions have been widely used in launch vehicles and upper-stages as well as deorbit modules because of better performances in comparison with other propulsion systems. Unfortunately heat transfer and thermal control limit bipropellant propulsion performance and maximum performance cannot be achieved. Well-known cooling methods such as regenerative and film cooling increase the cost using extra equipment and high temperature materials. In this paper, a new approach for cooling is presented based on combined ablative and radiative cooling. Governing equations are derived for two or three layers of thermal protection system (TPS) to optimize the TPS mass. The first layer is used as an ablative layer to control the temperature where the second and third layers are used as an insulator to control the heat fluxes. Proposed cooling method has been applied for two real bipropellant thrusters. According to the results, the presented algorithm can suitably predict the heat fluxes and satisfy the wall temperature constraint. Then, the algorithm has been used to minimize the wall temperatures as low as possible and replace high temperature materials (platinum alloy) with common materials (composite or steel). It is shown that selection of TPS materials affects the TPS mass and Isp simultaneously, but conversely. Best solution should be derived by trading off between structure temperature (cost), Isp (performance), and TPS thicknesses (geometry). Multidisciplinary approach to TPS and structure material selection of a bipropellant thruster is presented for a case study. It has been shown that mass and performance penalties of using TPS are acceptable, considering the advantages of using steel alloy instead of platinum alloy.     

Performance evaluation of a multi-product system under CONWIP control

Analytical models of multi-product manufacturing systems operating under CONWIP control are composed of closed queuing networks with synchronization stations. Under general assumptions, these queuing networks are hard to analyze exactly and therefore approximation methods must be used for performance evaluation. This research proposes a new approach based on parametric decomposition. Two-moment approximations are used to estimate the performance measures at individual stations. Subsequently, the traffic process parameters at the different stations are linked using stochastic transformation equations. The resulting set of non-linear equations is solved using an iterative algorithm to obtain estimates of key performance measures such as throughput, and mean queue lengths. Numerical studies indicate that the proposed method is computationally efficient and yields fairly accurate results when compared to simulation.     

基于AHP的车辆主动悬架LQG控制器设计

基于层次分析法（AHP）设计了一种能够降低车身加速度（BA）、悬架动行程（SWS）和轮胎动位移（DTD）的车辆主动悬架线性最优（LQG）控制器。首先建立了2自由度1/4车辆主被动悬架动力学模型;然后采用AHP确定了悬架各性能评价指标的加权系数并利用最优控制理论设计了车辆主动悬架控制器;最后在Matlab/Simulink环境下进行了仿真分析。对仿真结果进行对比后表明：在特定工况下通过对加权系数的合理选取,BA、SWS和DTD比被动悬架分别减小了18.73%、22.22%和4.76%,且主动控制力的均方根值为535.3994N。     

虚拟仪器在导弹测试发控系统中的应用

设计的基于PC/104嵌入式计算机系统的虚拟仪器,具有测量各种电学信号和时频信号功能;同时具有输出各种模拟信号、不同频率和幅值的脉冲信号及各种波形信号的信号源功能.其测量精度高,输出信号精度高,可用于导弹测试发控系统对其进行各种测试和控制.     

Virtual vehicle in the connecting transport automated material-handling system (AMHS)

In the connecting transport system, the time spent waiting for an empty vehicle is eliminated effectively and the work-in-process level can be reduced. Four different fixed vehicle types were used to carry out the wafers moving task. Thus, the automated material-handling system for a 300-mm wafer fab can be one of the three methods above or any mixture of these three connecting transport methods. However, no one method outperformed the others in all operational scenarios. A new concept of the virtual vehicle in the connecting transport automated material-handling system is proposed that can improve the task of moving wafers between bays and within each bay by a single system with interconnected lines. In this virtual vehicle environment, when the moving request is initiated, the wafers are assigned to the appropriate vehicle that can be changed to the vehicle type. Discrete-event simulation models are developed in eM-Plant? and compared with the virtual vehicle through the fixed vehicle in the connecting transport automated material-handling system. Using the virtual vehicle, the simulation results show that the performance measures such as throughput, transport time, 95% transport time and waiting time can be improved for different flow rates of the environment.