一类非线性系统的变结构控制问题

本文研究了简约型非线性控制系统的变结构控制问题,针对变结构控制切换函数的确定问题进行了深入研究,给出了一类非线性系统切换函数的确定方法。研究结果表明,该方法适用于一类难于或不能可控正则化和线性化的非线性控制系统的综合。最后通过仿真证实了该方法的有效性。     

基于辛几何构作一类新的带仲裁的认证码

具有仲裁的认证码既要防止敌手的欺骗,又要防止收方和发方的互相欺骗。利用有限域上辛几何构造了一类具有仲裁的认证码,计算了其容量参数。假设编码规则是按照均匀概率分布选择,给出了敌手模仿攻击、敌手替换攻击、发方模仿攻击、收方模仿攻击和收方替换攻击的成功概率。研究结论表明可用辛几何构作许多带仲裁的认证码。     

开裂式方向舵在变前掠翼布局中的操纵性能研究

 针对变前掠翼(VFSW)无尾布局的横航向操纵,设计了开裂式方向舵(SR)操纵面,采用Navier-Stokes控制方程的有限体积离散方法以及剪切应力输运(SST)湍流模型,计算了变前掠翼中平直翼和典型的前掠翼布局开裂式方向舵的操纵性能,并对其操纵效率进行了比较,分析了其流场形态。计算结果表明:右侧开裂式方向舵打开后,平直翼时迎角对偏航力矩的影响较小,而舵偏量对偏航影响显著,利于偏航;前掠翼的偏航力矩随迎角的增加有所波动,但在小迎角时较为稳定,偏航作用随舵偏量增加而增强;右侧滑对滚转作用强于左侧滑,偏航作用低于左侧滑。经比较,平直翼的偏航作用明显强于前掠翼,平直翼和前掠翼的滚转和偏航作用均具有耦合性,但平直翼的耦合效应弱于前掠翼。     

A new structural reliability index based on uncertainty theory

The classical probabilistic reliability theory and fuzzy reliability theory cannot directly measure the uncertainty of structural reliability with uncertain variables,i.e.,subjective random and fuzzy variables.In order to simultaneously satisfy the duality of randomness and subadditivity of fuzziness in the reliability problem,a new quantification method for the reliability of structures is presented based on uncertainty theory,and an uncertainty-theory-based perspective of classical Cornell reliability index is explored.In this paper,by introducing the uncertainty theory,we adopt the uncertain measure to quantify the reliability of structures for the subjective probability or fuzzy variables,instead of probabilistic and possibilistic measures.We utilize uncertain variables to uniformly represent the subjective random and fuzzy parameters,based on which we derive solutions to analyze the uncertainty reliability of structures with uncertainty distributions.Moreover,we propose the Cornell uncertainty reliability index based on the uncertain expected value and variance.Experimental results on three numerical applications demonstrate the validity of the proposed method.     

进口导叶形式对核心机驱动风扇级的影响

以某变循环发动机(VCE)所用核心机驱动风扇级(CDFS)为研究模型,数值模拟了CDFS在真实边界环境下的流动特性,分析了单/双涵道工作模式下,不同形式的可调进口导叶(IGV)对CDFS流动特性及性能的影响机理。结果表明:不同工作模式时,CDFS靠导叶角度的开闭实现大范围的流量调节。单涵道(SB)工作模式时,不同形式的可调进口导叶(VIGV)对CDFS性能的影响差异很小;双涵道(DB)工作模式时采用常规可调导叶(CIGV)会在其吸力面产生较大的流场分离,且流通能力和流量调节范围大大降低。可变弯度导叶通过可转动部分的开闭实现CDFS对流量调节的需求;通过固定部分保证CDFS导叶进口气流攻角基本不变,同时在固定部分和可转动部分连接处所形成的收缩通道的加速效应显著抑制了导叶吸力面的流动分离。可变弯度导叶是适用于CDFS在不同工作模式下性能参数及流量调节需求的可调导叶的形式。     

A closed-form solution for moving source localization using LBI changing rate of phase difference only

Due to the deficiencies in the conventional multiple-receiver localization systems based on direction of arrival(DOA) such as system complexity of interferometer or array and amplitude/phase unbalance between multiple receiving channels and constraint on antenna configuration,a new radiated source localization method using the changing rate of phase difference(CRPD)measured by a long baseline interferometer(LBI) only is studied. To solve the strictly nonlinear problem, a two-stage closed-form solution is proposed. In the first stage, the DOA and its changing rate are estimated from the CRPD of each observer by the pseudolinear least square(PLS) method,and then in the second stage, the source position and velocity are found by another PLS minimization. The bias of the algorithm caused by the correlation between the measurement matrix and the noise in the second stage is analyzed. To reduce this bias, an instrumental variable(IV) method is derived. A weighted IV estimator is given in order to reduce the estimation variance. The proposed method does not need any initial guess and the computation is small. The Cramer–Rao lower bound(CRLB) and mean square error(MSE) are also analyzed. Simulation results show that the proposed method can be close to the CRLB with moderate Gaussian measurement noise.     

软管锥套式空中加油系统建模与特性分析

针对自主空中加油研究中软管锥套运动模型过于简化,现有建模方法又存在成本高、计算量大、软管长度恒定等缺陷的问题,根据集中参数法原理,提出了一种长度可变的多级串联理想单摆系软管锥套运动模型.同时考虑软管收放、加油机牵连运动、重力、定常流、大气扰动、加油机尾流等内外部因素,推导了迭代形式的变长度软管锥套三维运动方程.由摆长约束导出了求解软管拉力的代数线性方程组,进而给出了模型稳定性证明和适用条件.通过数值仿真,测试了锥套阻力、平衡位置、软管收放等稳态特性,分析了加油机滚转运动、尾涡流场对软管锥套的动态影响以及软管甩鞭现象的产生机理.数值仿真结果验证了所建模型的有效性.      

根据两颗导航星信息估计捷联惯导系统误差的一种方法

针对高机动短时间飞行的飞行器,介绍了一种根据它相对2颗导航卫星的伪距离和伪速度信息,估计捷联惯导系统定位和定速度误差的方法.考虑到由确定飞行器相对每颗星的径向距离和速度的非线性方程施加的约束,根据这些误差矢量长度最小值的条件确定误差值.用空间解析几何法得出了计算捷联惯导系统误差估值的最终算法,这种算法能给出非线性最小值问题的精确解.     

空空导弹模型参考变结构飞控系统设计

应用模型参考变结构最终滑态控制方案设计了某型中距拦射空空导弹变结构自动驾驶仪。理论分析证明，该方案有效地改善了系统的动态品质，并且对系统的不确定性因素具有较强的鲁棒性，数字仿真结果表明，所设计的变结构自动驾驶仪具有良好的指令跟踪性能，对于系统参数的变化不敏感。