基于Legendre伪谱法的固体运载火箭轨迹优化研究

Legendre法则是一种高阶积分近似法则,用较大积分步长得到较高精度。以结点伪谱法处理不连续问题后,可以把一个无限维的动态最优控制问题转化为有限维的静态优化问题,大大降低了问题复杂性。将其应用于轨迹优化,力求使其成为一种求轨迹优化问题的通用算法。以三级固体运载火箭为例,在惯性直角坐标系中建立动力学模型,给出轨迹优化模型。轨迹优化算例结果验证了Legendre伪谱法在弹道时间和精度优化的正确性和有效性。     

变厚度弹性件柔性接头的非线性分析

结合试验数据,采用Mooney-Rivlin模型模拟了柔性接头的弹性件材料;根据非线性理论,采用混合插值有限元法对某一摆角状态下的柔性接头进行了大变形非线性弹性分析,并在此基础上初步探讨了厚度不均匀弹性件对层间应力的影响。计算结果表明,弹性层减薄到一定程度时,层间剪切应力沿宽度方向分布变得均匀,应力值仍集中在2 MPa以下;层间法向应力分布变化较小,呈二次曲线分布,最大值有所降低;其中,接近后法兰的弹性件厚度不均时,对各项应力最大值影响较大。     

固体火箭发动机药柱表面裂纹分析

为了分析含表面裂纹的固体火箭发动机药柱在温度、燃气内压与轴向过载联合作用下的扩展情况,在固体火箭发动机的危险截面上沿危险方向预设表面裂纹。采用有限元方法,在裂纹尖端构建三维奇异裂纹元,模拟裂纹扩展,分别计算随着裂纹扩展所对应裂纹深度的应力强度因子,得到了应力强度因子随裂纹深度的变化规律。根据应力强度因子的变化规律,探讨了发动机药柱裂纹扩展的趋势。     

Evaluation method for helicopter maritime search and rescue response plan with uncertainty

Helicopter plays an increasingly significant role in Maritime Search and Rescue (MSAR), and it will perform MSAR mission based on response plans when an accident occurs. Thus the rationality of response plan determines the success of MSAR mission to a large extent. However, with the impact of many uncertainty factors, it is difficult to evaluate response plans comprehensively before performing them. Aiming at these problems, an evaluation framework of helicopter MSAR response plan named UMAD is proposed in this paper, which reveals the influence mechanism of uncertainty factors based on Multi-Agent method and analyzes the mission flow based on Discrete Event System (DEVS) method. Furthermore, the evaluation criterion and indicators of response plan are extracted from the aspects of safety and effectiveness. Meanwhile, the Monte Carlo method is adapted to calculate the probability distribution and robustness of response plan comprehensive result. Finally, in order to illustrate the validity of this method, it is discussed and verified by an application example of evaluating multiple response plans to the same MSAR scenario. The results show that this method can analyze the influence of uncertainty more systematically and optimize response plans more comprehensively.     

迭代法求解航天器热网络方程的收敛条件与时间步长优化

热分析计算是航天器热设计验证和在轨温度预示的重要手段,其实质是对描述航天器在轨状态的能量平衡方程即热网络方程的求解。作为典型的非线性问题,航天器热网络方程通常采用迭代法求解,且目前尚无完善的理论可以判断迭代过程的收敛性和收敛条件。文章根据航天器热控设计的工程实际,提出一种可行的近似方法,实现了热网络方程的线性化;在此基础上对迭代法求解过程中的收敛性进行分析,确定了收敛条件下对节点热参数和时间步长的约束关系;并进一步分析时间步长与计算效率的关系,提出了以计算效率为优化目标的最优时间步长确定方法。最后通过某典型航天器热物理模型的计算验证了上述方法的正确性。     

考虑参数关联的缘板阻尼器减振性能分析

建立了缘板阻尼器(UPDs)各参数间的关联关系,揭示了减振性能随主要参数的变化规律,形成参数联动设计准则.基于双叶片-缘板阻尼器集中参数模型,采用多阶谐波平衡法(MHBM)计算稳态响应以衡量阻尼器性能;推导了解析雅可比矩阵,使收敛性和计算效率显著提高.结果 表明:考虑参数的关联性是必要的;选取较大材料密度与特定底角的对...     

燃气轮机周向拉杆转子连接刚度对转子振动特性影响的研究

为研究燃气轮机周向分布式拉杆转子轮盘间存在的连接刚度对轴系转子振动特性产生的影响,提出一种基于六自由度的弹簧单元等效方法.首先,将轮盘接触刚度与拉杆弯曲刚度同时等效进连接界面,便于使用一维梁单元求解其临界转速与振动响应变化,验证其与全三维有限元法吻合度在3％以内.然后,改写了非线性动力学方程,采用谐波平衡法对其进行求解...     

镜模波识别方法研究及其在火星磁鞘中的应用

镜模波是温度各向异性等离子体中的一种波动结构,根据磁场和离子分布及波动特性可以进行识别.本文对比了只使用磁场数据与同时使用磁场及离子数据两种识别方法,分析了两类方法的特点.只使用磁场数据的方法基于磁场强度变化大、方向沿背景磁场的特征,通常使用磁场强度的波动幅度ΔB/|B|以及磁场变化方向与背景磁场的夹角θ_min,θ_max作为参数;同时使用磁场及粒子数据的方法利用的是磁场纵波特性、总压平衡和波动在等离子体坐标系下静止的特征.使用两种方法对MAVEN卫星在火星磁鞘内的数据进行识别,结果表明在某些情况下,只使用磁场数据会导致对镜模波的误判.通过研究改变上述参数阈值时识别结果的变化,发现当θ_min> 40°,θ_max < 40°,ΔB/|B|> 80%时,只用磁场数据可取得较好的识别效果.     

Multi-mode optimal fuzzy active vibration control of composite beams laminated with photostrictive actuators

Firstly, a multi-field coupling finite element formulation of composited beam laminated with the photostrictive actuators is developed in this paper. Moreover, an optimal fuzzy active control algorithm is also proposed on the basis of the combination of optimal control and fuzzy one.This method opens a new avenue to resolve the contradiction between the linear system control method and nonlinear actuating characteristics of photostrictive actuators. The desired control for suppressing multi-modal vibration of photoelectric laminated beam is firstly obtained through optimal control and then the fuzzy control is used to approach the desired mechanical strain induced by photostrictive actuators. Thus, the multi-mode vibration control of beam is realized.In the design process of optimal fuzzy controller, the design of fuzzy control is independent of optimal control. The simulation results demonstrate that the proposed control method can effectively realize multi-modal vibration control of photoelectric laminated beams, and the control effect of optimal fuzzy control is better than that of optimal state feedback control.     

Exploration and implementation of commonality valuation method in commercial aircraft family design

Commercial aircraft family design can reduce development costs, shorten development cycles, and expand the market coverage of aircraft. Commercial aircraft family development has become one of the most important features of modern aircraft design. This paper explores the effects of commonality on different aircraft models in a commercial aircraft family. The existing product commonality indexes are summarized and their limitations in the application to aircraft design are discussed. Then a new component commonality index is proposed based on the component decomposition structure. A model for calculating the aircraft program value is established,which considers development costs, manufacturing costs, sale price, operation costs and residual costs. The effects of aircraft commonality on time and economic costs of both development and manufacturing, and on sale price, are analyzed and quantified. The commonality evaluation strategy is obtained, which features comprehensive consideration of the aircraft program value and time costs. The break-even analysis of aircraft is proceeded on the basis of costs and price data. By using a real option method, the strategy considers the uncertainty of the aircraft program and the flexibility of the manufacturer. This strategy proves to be rational and applicable to aircraft design based on the calculation of three examples and the analysis of parameter sensitivity.