新算法在划船和伪划船效应中的应用

划船效应补偿是高精度捷联惯导系统解算的重要环节。通过研究其误差特性,推导了新的通用划船效应补偿公式。同时提出了角振动环境中伪划船效应的存在,对伪划船效应的产生原因、表达方式以及对捷联惯导系统的影响进行了分析。对新的补偿算法在划船效应和伪划船效应下进行了仿真试验。     

基于改进遗传算法的平流层飞艇定点悬停控制(英文)

平流层飞艇定点悬停控制是飞艇应用领域的关键技术。该控制问题可以转化为非线性多目标优化问题来求解。遗传算法是解决现代非线性多目标优化问题的一种重要方法。但是基本遗传算法在解决定点悬停飞艇实际控制问题时,具有易陷入局部最优解、在遗传进化过程中随机性较强、搜索效率低下及耗时多等缺陷。通过借鉴并行遗传算法、模拟退火算法和向量评价遗传算法的基本思想,在基本遗传操作中添加切断算子和拼接算子,设计一种改进遗传算法来改善上述缺陷。仿真结果表明该方法是有效可行的。     

Exact algorithms for scheduling multiple families of jobs on parallel machines

In many practical manufacturing environments, jobs to be processed can be divided into different families such that a setup is required whenever there is a switch from processing a job of one family to another job of a different family. The time for setup could be sequence independent or sequence dependent. We consider two particular scheduling problems relevant to such situations. In both problems, we are given a set of jobs to be processed on a set of identical parallel machines. The objective of the first problem is to minimize total weighted completion time of jobs, and that of the second problem is to minimize weighted number of tardy jobs. We propose column generation based branch and bound exact solution algorithms for the problems. Computational experiments show that the algorithms are capable of solving both problems of medium size to optimality within reasonable computational time. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 823–840, 2003.     

大容量储能发电机并联运行励磁控制算法

大容量储能发电机作为脉冲电源，整流后通过逆变器向大功率脉冲负载供电。采用储能发电机直流侧并联方式工作，可以有效提高系统带载能力与可靠性。当并联运行的储能发电机转速不同时，根据转速合理分配电机释放功率可以有效提高系统工作效能，因此需要设计一种具有功率调节功能的励磁控制算法。在电压、电流双闭环控制的基础上，引入功率前馈控制，推导并求解了前馈功率与励磁电流关系以及控制参数，并根据电机初始转速设计了功率分配算法。仿真试验结果表明，功率前馈控制在励磁控制过程中起主导作用，有效分配储能电机释放功率大小，提高了励磁电流响应速度，抑制了负载功率扰动对励磁控制系统的影响。     

装备剩余寿命预测平行仿真中模型动态演化方法

装备平行仿真中的一个重要概念是实时数据驱动的模型动态演化,但是至今仍缺乏具体应用领域的实现方法。以带未知离散冲击的混合退化装备剩余寿命预测为背景,以多态Wiener状态空间模型为演化对象,提出一种装备平行仿真中模型动态演化方法,包括基于交互多模型强跟踪滤波的模型软切换和基于期望最大化算法的模型参数在线估计,并实现了基于平行仿真的装备剩余寿命实时预测。利用某轴承退化数据进行实例研究,结果表明该方法能有效提高仿真逼真度,剩余寿命预测的准确度较高、不确定性较小,具有较高工程应用价值。     

基于改进协同遗传算法的有效载荷系统功能序列规划方法

针对传统回溯算法在求解基于知识模型的有效载荷系统功能序列规划问题中搜索效率低的问题,提出一种基于"择劣变异"(Worst Individual Mutation,WIM)策略的协同遗传算法(Co-evolutionary Genetic Algorithm,CGA)的改进算法WIM-CGA。该算法在遗传过程中采用双路线进化方案,即"择优实施标准遗传过程,择劣实施变异操作",达到提高求解精确度及搜索效率的目的。仿真结果表明,同等测试条件下,当功能规模为50,约束密度为1.0时,WIM-CGA算法在限定时间内最优解的平均精确度比优化的回溯算法提高了54.15%,比CGA算法提高了6.18%,且当所得解的精确度大于90%时,WIM-CGA算法比CGA算法的迭代次数减少了65.79%,耗时降低了48.97%,显著提高了功能序列规划的效率。     

流域变换的串行与并行策略研究

流域变换是数字形态学中用于图像分割的一种经典方法,其并行化问题成为近年来研究的重点。首先给出了流域变换的数学模型,并归纳列举了几种离散情况下的形式化定义;其次分类总结了近年来流域变换串行算法研究的新进展,从而在此基础上重点讨论了相应的并行化策略。详细分析了设计并行流域算法需要考虑的几个问题;并比较评价了现有并行算法的性能特点,得出了一些结论;最后提出了有待进一步研究的问题。     

基于改进空战威胁评估模型的权重计算方法比较

针对多无人机(UAV)任务网协同空战态势威胁评估问题,在现有基本模型基础上增加考虑气象环境对威胁评估要素的影响和无人机的自主可靠性系数两个实际因素,提出一种改进的超视距空战威胁评估模型;同时,应用串联电阻分压法、改进AHP法和熵权法分别计算融合模型中各威胁指标的权重系数;进而,在考虑己方战机对敌方战机综合威胁与优势的基础上,介绍了战机协同空战目标分配的基本方案。最后,应用上述3种权重计算方法进行空战威胁仿真计算,计算结果表明改进空战威胁评估模型可有效改善空战决策性能。     

基于Fiducial推断的Bayes验前分布的表示

先验分布的确定与表示是Bayes统计推断的出发点和关键点。提出了一种基于信仰推断 (FiducialInfer ence)观点确定Bayes先验分布的设想 ,有助于解决无验前信息或验前历史信息较少时先验分布的确定问题 ,文中给出了一个实例说明了该方法的应用     

Estimating failure time distribution and its parameters based on intermediate data from a Wiener degradation model

Instead of measuring a Wiener degradation or performance process at predetermined time points to track degradation or performance of a product for estimating its lifetime, we propose to obtain the first‐passage times of the process over certain nonfailure thresholds. Based on only these intermediate data, we obtain the uniformly minimum variance unbiased estimator and uniformly most accurate confidence interval for the mean lifetime. For estimating the lifetime distribution function, we propose a modified maximum likelihood estimator and a new estimator and prove that, by increasing the sample size of the intermediate data, these estimators and the above‐mentioned estimator of the mean lifetime can achieve the same levels of accuracy as the estimators assuming one has failure times. Thus, our method of using only intermediate data is useful for highly reliable products when their failure times are difficult to obtain. Furthermore, we show that the proposed new estimator of the lifetime distribution function is more accurate than the standard and modified maximum likelihood estimators. We also obtain approximate confidence intervals for the lifetime distribution function and its percentiles. Finally, we use light‐emitting diodes as an example to illustrate our method and demonstrate how to validate the Wiener assumption during the testing. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008