Optimal policies for M/M/m queue with two different kinds of (N,T)‐policies

In this paper, two different kinds of (N, T)‐policies for an M/M/m queueing system are studied. The system operates only intermittently and is shut down when no customers are present any more. A fixed setup cost of K > 0 is incurred each time the system is reopened. Also, a holding cost of h > 0 per unit time is incurred for each customer present. The two (N, T)‐policies studied for this queueing system with cost structures are as follows: (1) The system is reactivated as soon as N customers are present or the waiting time of the leading customer reaches a predefined time T, and (2) the system is reactivated as soon as N customers are present or the time units after the end of the last busy period reaches a predefined time T. The equations satisfied by the optimal policy (N*, T*) for minimizing the long‐run average cost per unit time in both cases are obtained. Particularly, we obtain the explicit optimal joint policy (N*, T*) and optimal objective value for the case of a single server, the explicit optimal policy N* and optimal objective value for the case of multiple servers when only predefined customers number N is measured, and the explicit optimal policy T* and optimal objective value for the case of multiple servers when only predefined time units T is measured, respectively. These results partly extend (1) the classic N or T policy to a more practical (N, T)‐policy and (2) the conclusions obtained for single server system to a system consisting of m (m ≥ 1) servers. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 240–258, 2000     

离散变结构系统的组合控制策略研究

对离散变结构控制系统的趋近律方法进行研究,提出了4种组合控制策略,它们可以明显改善系统的动态性能,并给出应用例子加以验证．     

大型飞行器制导与姿态控制联合仿真建模研究

针对固体火箭发动机、机动发射的大型飞行器的特点 ,提出了建立大姿态情况下全量、全干扰、非线性、时变的制导与姿态控制联合仿真数学模型的一般方法。以某型号固体发动机、机动发射的飞行器为背景 ,在综合考虑了控制系统动态特性和飞行器质心运动、绕质心运动、变质量特性、弹性振动特性、风干扰等因素的情况下 ,建立了飞行器的联合仿真数学模型。进而在面向对象仿真环境下 ,建立了直观、形象、易理想、易扩充的面向对象的飞行器联合仿真模型。仿真结果表明所建联合仿真模型是正确和有效的     

大型柔性空间结构的多级分散化振动控制

文中直接以结构的动力学变量作为系统状态,从理论上推导出了反馈和状态变量的解析表达式。基于该表达式,对一空间站模型进行了仿真。结果表明,该方法具有计算量小、稳定性好的优点,便于在线控制。     

非线性干扰观测器的高超声速飞行器自适应反演控制

针对高超声速飞行器参数不确定弹性体模型,提出了一种基于非线性干扰观测器的自适应反演控制器设计方法。将曲线拟合模型表示为严格反馈形式,采用反演方法设计控制器。采用动态面方法获取虚拟控制量的导数,避免了传统反演控制"微分项膨胀"问题。为了增强控制器的鲁棒性,基于二阶跟踪-微分器设计了一种新型非线性干扰观测器,以此对模型不确定项进行自适应估计和补偿。仿真结果表明,控制器对模型不确定性和气动弹性影响具有强鲁棒性,且能实现对速度和高度参考指令的稳定跟踪。     

战术导弹连射试验测控软件关键技术

针对导弹的多发连射试验,在单发导弹飞行试验实时测控软件系统的基础上,研究了I/O缓冲设置、多发射信号的接收与识别、第n发导弹数据处理时机等关键技术.解决了研发用于战术导弹连射试验测控软件系统中的多项难题,使得靶场实时测控软件系统能够满足多发导弹连射试验的航区安全控制需要.     

Determining a threshold control policy for an imperfect production system with rework jobs

Consider a threshold control policy for an imperfect production system with only a work center handling both regular and rework jobs. An imperfect production system studied here, generates defect jobs by factors other than machine failures. A threshold control or (ω, s) policy sets the guideline for a work center to switch between regular and rework jobs. A production cycle begins with loading and processing of several batches of regular jobs with a lot size equal to s. The outcome of each completed regular job is an independent Bernoulli trial with three possibilities: good, rework, or scrap. Once the work center accumulates more than a threshold ω of rework jobs, it finishes the last batch of regular jobs and switches to rework jobs. The objective of this research is to find a threshold ω and a lot size s that maximize the average long‐term profit. The ultimate goal is to construct a simple algorithm to search for ω and s that can be implemented directly in production management systems, as a result of this work. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 273–301, 1999     

防空武器火控系统对空中目标参数估计方法仿真

针对防空武器火控系统的特点,提出了一种防空武器火控系统对空中目标参数估计的方法,可以在不知道目标距离的条件下得到目标的航向角与俯仰角,实现对目标的被动式跟踪,对估计误差的统计特性进行了分析,仿真结果表明了该方法比传统的估计方法更加可行.     

基于AHP和模糊评价法的舰艇编队编成优化方法

海军舰艇通常以编队的形式执行各种作战任务.由于武器装备科技含量的不断提高,使得海战对抗强度日益激烈.舰艇编队作为海战的战斗单元,其作战效能的高低直接影响着海战的胜负,不同的作战任务决定了不同的编队编成.以封锁任务为作战背景,运用层次分析法(AHP)确定舰艇编队作战效能评价体系中各指标的权重,使用模糊综合评价方法对各模糊指标进行评价,评价结果表明该方法能够比较科学合理地对舰艇作战编队的编成进行优化,从而为海军舰艇作战编队编成的科学性和合理性提供了一种论证方法.