高超声速滑翔式飞行器再入轨迹多目标多约束优化

轨迹优化是高超声速滑翔式飞行器关键技术之一.为避免间接法求解轨迹优化问题时对初值敏感以及伪谱法求解轨迹优化问题中难以处理航路点和禁飞区等问题,提出采用基于Akima插值多项式的直接法求解高超声速滑翔式飞行器再入轨迹优化问题.以驻点热流密度最小和到达目标点时间最小为优化目标,考虑了终端约束、航路点约束、禁飞区约束、动压约束、过载约束等约束条件.仿真结果表明:采用的插值方法可以减少插值过程中的控制变量越界问题;得到的Pareto前沿具有良好的分布性,在初步设计时能够给设计者较大的选择余地;和文献中的单目标优化结果相比,本文所采用的算法也具有较好的寻优能力.     

An eikonal equation based path planning method using polygon decomposition and curve evolution

Path planning is a key technique of autonomous navigation for robots, and the velocity field is an important part. Constructing velocity field in a complex workspace is still challenging. In this paper, an inner normal guided segmentation algorithm in a complex polygon is proposed to decompose the complex workspace in this paper. The artificial potential field model based on probability theory is then used to calculate the potential field of the decomposed workspace, and the velocity field is obtained by utilizing the potential field of this workspace. Path optimization is implemented by curve evolution, during which the internal force generated in the smoothing process of the initial path by a mean filter and the external force is obtained from the gradient of the workspace potential field. The parameter selection principle is deduced by analyzing the influence of several parameters on the path length and smoothness. Simulation results show that the designed polygon decomposition algorithm can effectively segment complex workspace and that the path optimization algorithm can shorten and smoothen paths.     

Optimal source placement for point coverage in active multistatic sonar networks

The allocation of underwater sensors for tracking, localization, and surveillance purposes is a fundamental problem in anti-submarine warfare. Inexpensive passive receivers have been heavily utilized in recent years; however, modern submarines are increasingly quiet and difficult to detect with receivers alone. Recently, the idea of deploying noncollocated sources and receivers has emerged as a promising alternative to purely passive sensor fields and to traditional sonar fields composed of collocated sources and receivers. Such a multistatic sonar network carries a number of advantages, but it also brings increased system complexity resulting from its unusual coverage patterns. In this work, we study the problem of optimally positioning active multistatic sonar sources for a point coverage application where all receivers and points of interest are fixed and stationary. Using a definite range sensor model, we formulate exact methods and approximation algorithms for this problem and compare these algorithms via computational experiments. We also examine the performance of these algorithms on a discrete approximation of a continuous area coverage problem and find that they offer a significant improvement over two types of random sensor deployment.     

基于混沌量子粒子群的舰炮身管多目标优化研究

舰炮的炮口扰动是影响舰炮射击精度的重要因素。为了减少舰炮的炮口扰动,优化身管结构,建立了柔性身管的有限元模型并将该模型的模态计算结果与模态试验测试值进行对比,证明建立的柔性身管有限元模型是有效的。提出了混沌量子粒子群算法与动力学联合优化的方法,进行身管和炮口的多目标优化,优化结果表明：优化后的炮口中心的线速度、角速度和角位移与优化前相比显著减小,身管质量有所降低,结构更加合理,该优化方法有效可行,为下一步全炮总体优化设计提供了一定的借鉴。     

Maintaining systems with heterogeneous spare parts

We consider the problem of optimally maintaining a stochastically degrading, single‐unit system using heterogeneous spares of varying quality. The system's failures are unannounced; therefore, it is inspected periodically to determine its status (functioning or failed). The system continues in operation until it is either preventively or correctively maintained. The available maintenance options include perfect repair, which restores the system to an as‐good‐as‐new condition, and replacement with a randomly selected unit from the supply of heterogeneous spares. The objective is to minimize the total expected discounted maintenance costs over an infinite time horizon. We formulate the problem using a mixed observability Markov decision process (MOMDP) model in which the system's age is observable but its quality must be inferred. We show, under suitable conditions, the monotonicity of the optimal value function in the belief about the system quality and establish conditions under which finite preventive maintenance thresholds exist. A detailed computational study reveals that the optimal policy encourages exploration when the system's quality is uncertain; the policy is more exploitive when the quality is highly certain. The study also demonstrates that substantial cost savings are achieved by utilizing our MOMDP‐based method as compared to more naïve methods of accounting for heterogeneous spares.     

基于不确定性的末制导初始参数优化设计方法

为量化无动力滑翔飞行器末制导初始参数不确定性的综合影响,提升飞行器落点精度,提出基于不确定性的末制导初始参数优化设计方法。面向飞行器末端高动态打击需求,采用落角约束下的滑模变结构导引律进行实时弹道成型,进而考虑末制导初始参数的不确定性。以落点有效毁伤半径概率和落点圆概率偏差为多优化目标,建立基于不确定性的末制导初始参数及制导律参数优化模型。针对这一不确定性优化模型,研究利用高效全局优化和蒙特卡洛方法,给出末制导初始参数及制导律参数的最优设计方案。仿真结果表明:该方法能显著提升落点精度,为方案设计阶段飞行器末制导交接点的选取提供决策支持。     

再入快速抵达轨迹优化设计方法

针对再入初始速度大、飞行时间约束苛刻的轨迹设计问题,提出一种基于遗传算法和攻角+倾侧角联合优化的再入快速抵达轨迹优化设计方法。该方法在再入初段利用较大攻角迅速减小弹道倾角和拉平弹道,在再入后段/滑翔段联合设计和优化攻角+倾侧角变化规律以显著降低终端飞行速度,同时满足终端高度、终端航向角、最大动压、最大热流等约束条件。该方法能够提升传统升力体飞行器再入快速到达能力并拓展其应用范围。仿真结果表明,在典型飞行器参数和较大初始再入速度条件下,全程飞行时间小于12 min,终端速度能够小于7Ma,横向机动距离超过800 km。     

干扰及机动条件下的比例导引智能调控策略

由于红外诱饵干扰样式复杂、目标机动形式多变导致传统比例导引律极易被干扰。为提高采用比例导引方法的导弹性能,提出一种利用径向基函数网络调控比例系数及导弹发射时机的智能导引律。以飞行时间及脱靶量为参考,通过构建加权型指标函数将求解最优比例系数及发射时机问题转化为单目标优化问题;引入量子粒子群算法求解最优决策参量,并以其作为网络输出,干扰样式作为网络输入,离线训练径向基函数网络;为提高训练效率,结合K-means及K最近邻算法初始化径向基函数网络。仿真结果表明,当存在红外诱饵干扰时,智能导引律性能优于扩展比例导引律及自适应滑模导引律。     

Optimizing the US Navy's combat logistics force

We study how changes to the composition and employment of the US Navy combat logistic force (CLF) influence our ability to supply our navy worldwide. The CLF consists of about 30 special transport ships that carry ship and aircraft fuel, ordnance, dry stores, and food, and deliver these to client combatant ships underway, making it possible for our naval forces to operate at sea for extended periods. We have modeled CLF operations to evaluate a number of transforming initiatives that simplify its operation while supporting an even larger number of client ships for a greater variety of missions. Our input is an employment schedule for navy battle groups of ships operating worldwide, extending over a planning horizon of 90–180 days. We show how we use optimization to advise how to sustain these ships. We have used this model to evaluate new CLF ship designs, advise what number of ships in a new ship class would be needed, test concepts for forward at‐sea logistics bases in lieu of conventional ports, demonstrate the effects of changes to operating policy, and generally try to show whether and how the CLF can support planned naval operations. Published 2008 Wiley Periodicals, Inc. Naval Research Logistics 2008     

Competitive location and capacity decisions for firms serving time‐sensitive customers

In this article we explore how two competing firms locate and set capacities to serve time‐sensitive customers. Because customers are time‐sensitive, they may decline to place an order from either competitor if their expected waiting time is large. We develop a two‐stage game where firms set capacities and then locations, and show that three types of subgame perfect equilibria are possible: local monopoly (in which each customer is served by a single firm, but some customers may be left unserved), constrained local monopoly (in which firms serve the entire interval of customers but do not compete with each other), and constrained competition (in which firms also serve the entire interval of customers, but now compete for some customers). We perform a comparative statics analysis to illustrate differences in the equilibrium behavior of a duopolist and a coordinated monopolist. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008