【作者】 赵瑞学；

【导师】 钱林方；

【作者基本信息】 南京理工大学 ， 机械工程， 2011， 博士

【摘要】 自动机技术是战车炮系统的关键技术之一。某新型战车炮系统采用了新型特种弹药及转膛技术,在提高射速、增大威力的同时,也带来了相应的技术问题,诸如自动机总体匹配问题及弹药的定位问题等。本文以“十一五”研究课题为背景,应用自动武器动力学、多体系统动力学、优化设计、概率分布、机械可靠性等理论对某战车炮自动机及其关键技术进行了深入的研究,为工程实际提供理论依据和决策参考。主要研究内容如下：(1)分析了新型战车炮自动机总体结构和工作原理,对供弹机构动作、击发动作等进行了运动学匹配分析,提出了新型自动机总体的关键技术为新型特种弹药的输弹定位技术。(2)通过分析卡弹定位机构中各构件的受力状况,利用自动武器动力学理论建立了卡弹定位机构在强制输弹阶段的全系统运动微分方程式,并以此为基础进行了数值模拟。方程式中各项具有清晰的意义,这为分析理解系统的动力学响应打下了理论基础。(3)利用多体系统动力学理论,在现代多体动力学软件平台上建立了基于第-类拉格朗日方程的输弹定位系统的导轨链式输弹机和卡弹定位机构虚拟动力学仿真模型。通过对这两个动力学仿真模型进行合并获得了输弹定位系统的动力学模型,并对模型进行了仿真分析。最后,通过对卡弹定位机构中关键构件的柔性化获得了刚柔耦合动力学模型,并就其仿真结果和多刚体动力学模型进行了比较,结果显示两者是基本一致的。动力学模型中的链节等效弹簧刚度和各构件之间的接触碰撞刚度通过有限元法获得,使得虚拟样机和真实的物理样机更加一致。(4)本文基于多学科集成优化平台,以缓冲簧、卡弹簧、挡弹簧的弹簧刚度和预变形量为设计变量,以正确卡弹定位为约束条件,对卡弹定位机构进行了以动力学匹配为目的的试验设计。通过匹配试验设计,获取了可行的设计变量向量,并获知弹药位移的概率密度图呈现3个“岛屿”状态。这种方法克服了以往传统手段无法对弹性元件多、接触碰撞复杂的机械系统进行动力学匹配设计。(5)为了降低卡弹爪、挡块与弹药之间的接触力,延长构件的使用寿命,以缓冲簧、卡弹簧、挡弹簧的弹簧作用力最小为目标函数,以3个弹簧的弹簧刚度和预变形量为设计变量,以正确卡弹定位为约束条件进行了多目标动力学匹配优化设计,获得了相应的弹簧刚度和预变形量值。在此基础上,考虑弹簧的设计问题,用分层优化的策略对卡弹定位机构弹簧设计参数进行了基于动力学匹配的多目标优化设计。第一层为全局层面上的,考虑正确卡弹定位的优化设计问题。第二层为局部层面上的,考虑弹簧的优化设计问题。这种分层优化策略既降低了各构件间较小的接触力,减少了设计变量,节约了设计时间,而且考虑了更多的设计因素具有更强的工程实用意义。(6)利用截尾分布基本理论,提出了常用的4种截尾分布密度函数、累积分布函数的一般表达式及相应截尾分布的期望和方差。在此基础上,根据各个截尾分布的累积分布函数推导了截尾分布随机变量随机数的抽样方法,并推广到一般典型分布随机数的抽样方法。截尾分布及其抽样方法的讨论为机构运动可靠性分析中设计变量的有效处理打下了基础。(7)讨论了精确分析方法(应力—强度干涉模型)、近似方法(均值一次二阶矩法、JC法)、数值模拟法(蒙特卡罗法)理论及其在机构可靠性分析中的应用。在精确分析方法中证明了截尾正态分布不具有叠加性。(8)针对卡弹定位机构这一多维、强非线性系统的机构运动可靠性问题,建立了可靠性准则,用数值模拟法分别以随机变量服从一般分布和截尾分布进行了机构运动可靠度分析。对两者结果进行了比较,结果显示计算运动可靠度时随机变量选择截尾分布比一般分布更加精确。更多还原

【Abstract】 Automatic mechanism technology is one of combat vehicle gun’s key Technologies.Because a new-type special ammuniton and rotating chamber technology have been used in a combat vehicle gun, while enhancing firing frequency, increasing the power, but also brings the corresponding technical problems, such as collectivity match, shell loading and positioning, etc. Based on the key beforehand project of the "eleventh five-year", the research is developed and aims at the automatic mechanism of a combat vehicle gun and its key technology using the theory of automatic weapon dynamics, multi-body dynamics, optimization design, probability distribution and mechanical reliability, which can provide theoretical foundation and design decision for engineering practice of such weapon systems. The main research content is as follows:(1) Collectivity structure and its working principle of this new type automatic mechanism of a combat vehicle gun are discussed. And then the shell loading and positioning movement, the firing movement and so on has carried on the kinematics match analysis. The shell loading and positioning technology is a key technology in this automatic mechanism.(2) Through load analysis of every part in cartridge retaining mechanism, motion differential equations of shell are built during its feeding and positioning time via dynamics theory of automatic weapons. And then numerical simulation is done base on this differential equations. Each item has its meaning; this builds theoretical foundation for understanding the dynamic response of mechanism system.(3) Virtual dynamic models of cartridge retaining mechanism and guided-chain ramming mechanism are built in multi-body system dynamic software based on the first kind of Lagrange equation via multi-body system dynamics theory.Through merging both dynamic models, the dynamic model of the shell loading and positioning system is acquired. Finally, rigid-flexible coupling dynamic model is builted via replacing some key parts with their flexible parts in dynamic model of cartridge retaining mechanism.And its simulation results and multi-body dynamics model are compared, results show that the two are basically the same. Equivalent spring stiffness of chain links and stiffness of all contact pairs in those dynamic models are calculated using finite element method. This will make virtual prototype and real physical prototype more consistent.(4) Based on the multidisciplinary integrated optimization platform, with buffer spring, braking spring, positioning spring’s stiffness and pre-deformation as design variables, with proper positioning as constraint conditions, an experimental design is carried out on cartridge retaining mechanism for dynamic matching of three springs. Through dynamic matching experimental design, several groups of feasible design variables are obtained, and the preliminary design variables, and the probability density of shell displacement presents in three "island" state. For complex mechanical system with many elastic components and contact collisions, this method overcomes the disadvantage of the traditional methods which can hardly do dynamic matching design.(5) To reduce the contact forces between shell and retaining pawl, shell and hold down plate in the cartridge retaining mechanism, and prolong the life of those parts, with stiffness minimums of buffer spring, braking spring, positioning spring as objective functions, with three spring’s stiffness and pre-deformation as design variables, with proper positioning as constraint conditions, multi-objective dynamic matching optimization design is conducted. And spring stiffness and pre-deformation are obtained. Based on this, considering the design problem of springs, multi-objective dynamic matching optimization design is conducted using hierarchical optimization design. The first layer is a global level, mainly consider the optimal design of shell proper positioning. The second layer is the local level, considering the optimal design of the spring.This kind of hierarchical optimization strategy can not only reduce the contact forces, design time cost,the number of design variables, but also consider more design factors. Hence, it has more practical meaning.(6) Using truncation distribution theory, the paper derives four kind of truncated distribution density functions and cumulative distribution functions of commonly used typical distributions and corresponding means, variances. On this basis, according to cumulative distribution functions of various truncation distributions, the sampling method of random variables is deduced, which is available for non-truncated distribution. The discussion of truncated distribution and sampling method is foundation for design variables in mechanism motion reliability analysis.(7) Discussing theory and its application of accurate analysis method (stress-strength interference model), approximate method (mean first-order second-moment method, JC method), and the numerical simulation method (Monte Carlo method) are discussed in motion reliability analysis. And then it is proved that trucated normal distribution don’t have superposition in accurate analysis method.(8) Aiming at cartridge retaining mechanism which is multi-dimensional, strong nonlinear systems, with some motion reliability rules built, mechanism motion reliability analysis are done via numerical simulation method when random variables obey general distribution and truncated distribution respectively. At last, the data is compared with both,and the results show that random variables which obey truncated distribution is more accurate than the other when mechanism motion reliability analysis is done.更多还原