双轴旋转调制捷联惯导系统旋转方案优化设计

针对双轴旋转捷联惯导系统自标定旋转路径和旋转调制方案不一致的问题,48次序一体式方案将标定路径和旋转调制方案融合,减小了实际操作的复杂性,提高了导航精度。为减少48次序方案的冗余次序,进一步增强旋转调制效果,提出了一种改进的40次序一体式旋转方案。所提方案不仅能同时实现自标定和旋转调制功能,而且由惯性器件安装误差引起的数学平台姿态角误差小于传统16次序方案,对零偏误差的调制周期短于48次序一体式方案。基于奇异值的可观测度分析及仿真和实验结果表明,40次序方案的标定结果更接近真实值,经过旋转调制后的导航误差更小。在3天的导航时间内,所提方案的速度精度和位置精度相比于48次序一体式方案分别提高了20%和12%。     

基于有限差分法的江坪河溢洪洞出口段开挖方案对比研究

基于项目组开发出的前处理程序,建立AUTOCAD初步建模、ANSYS进行形体切割和网格划分、FLAC3D进行模型计算的多软件联合建模模式,极大提高建模效率和精度.提出单位开挖方量对应的最大不平衡力λi的概念,结合数值模型关键点位移的检测技术和塑性区显示,针对两种开挖方案进行了对比分析.分析显示:不同开挖方案对最终位移的影响不明显,方案二的施工中的位移控制要稍优于方案一;演化过程对比说明,两方案第9步开挖的单位开挖方量对应的最大不平衡力λi比值最大,为最危险开挖步,方案二明显优于方案一,若采用方案一,第6步和第9步开挖时岩体所受开挖应力调整幅度增大,失稳可能性增大;最终塑性区为比较标准时两方案可行性相同.综合对比,方案二优于方案一.     

一种车辆航位推算改进方法

针对车辆导航的特点,给出了一种基于单陀螺单加速度计的简化航位推算方案,同时研究了差速里程仪导航方案存在的问题,提出了基于单陀螺单里程仪的航位推算方案.该方案可以充分发挥陀螺短时精度高,里程仪测量误差随着时间增长变化较小(特别是在车辆低速行驶时)的优点,并对这几种航位推算方案进行了仿真研究.仿真结果表明:单陀螺单里程仪航位推算方案的航向精度和位置精度都是较高的.     

飞航导弹光学方位瞄准技术

本文在研究弹道导弹光学瞄准技术的基础上,提出了适应飞航导弹方位瞄准要求的新方案。光学瞄准新方案设施简单、对准时间短、对准精度高,并能适应不同初始条件的发射阵地,应用灵活。新方案已做了对准试验,证实方案可行,效果显著。     

在线铁谱仪电磁装置磁场的有限元分析

针对在线铁谱仪中的一种新型的直流电磁装置,通过有限元分析揭示了其工作气隙中的磁场分布规律,采用正交设计方法确定了夹角方案条件下的最佳工作气隙尺寸,比较了磁场在夹角方案和倾角方案条件下的分布情况.结果表明,该装置在夹角方案条件下可以在油样流动方向上形成由弱到强的磁场分布,但效果不如倾角方案好.     

机抖激光陀螺的磁电拾振技术

经分析指出,磁电拾振技术应用在机抖激光陀螺抖动反馈方案中,其工作原理属于速度型传感器,直接反映抖动偏频量。给出了磁电拾振器的误差因素和结构特点,并测试了磁电拾振器方案与压电陶瓷反馈方案的输出特性。对同一机抖陀螺分别使用以上两种抖动反馈方案;在静态测试零偏稳定性、抗振动和冲击能力中,前者皆好于后者。研究表明磁电拾振方案比压电陶瓷反馈或光电反馈方案更适合作为抖动反馈。     

两种零速校准方案的比较

采用零速校准技术是提高地面惯性测量系统定位精度的一项有效手段。本文分析比较了两种零速校准方案,即方案Ⅰ和方案Ⅱ。分析结果表明;方案Ⅱ不仅简单易行,而且对系统各项非模型误差的影响不太敏感。这一点在车载试验中得到了进一步的证实。     

陀螺寻北仪二位置寻北方案

讨论了挠性陀螺寻北仪二位置寻北方案。二位置寻北方案是利用陀螺仪敏感在相差180°的两个方向上的地球自转角速率分量,准确解算出地理真北方向与陀螺轴向的交角,从而实现寻北的方案。该方案利用转位对消了陀螺的常值漂移,因此,大大降低了对陀螺精度的要求,已经成功的应用于我所研制的CFN系列寻北仪中。实践证明:对于双轴陀螺采用二位置寻北方案易于实现,精度较高。     

一种新型高精度大功率电动飞行仿真转台的驱动方案设计

针对一种新型电动飞行仿真转台高精度、大功率的突出特点,设计了十分有效的驱动方案。首先简要介绍了该电动飞行仿真转台的主要技术指标,然后提出了高精度大功率飞行仿真转台驱动方案的详细设计策略,驱动方案中采用PWM功率放大器驱动,最后给出了该驱动方案在飞行仿真转台控制系统中的设计实现。实际应用表明:该驱动方案可以很好地满足新型电动飞行仿真转台的高精度、大功率要求,具有很强的抗干扰性和鲁棒性,完全适合在高精度大功率电动仿真转台上应用。     

固体力学中的无网格方法

简要地介绍了目前在无网格方法中主要使用的近似方案:移动最小二乘法、核函数法和单位分解法,并对这些方案的联系及各自的一致性条件进行了讨论;此外,对于无网格方法在数值计算中的离散方案、积分方案、边界条件的引入以及如何处理场函数或其导数的不连续性加以论述．      

基于H_∞滤波的主/子惯导组合中挠曲变形补偿算法

针对舰载环境下,主/子惯导组合中主、子惯导间的挠曲变形问题,设计了H?滤波算法。算法将主、子惯导间的挠曲变形作为一种能量有限的量测噪声,通过H?滤波对不确定噪声的鲁棒性来保证滤波精度。在经典的"速度+姿态"匹配方法的基础上,仿真比较了:1)方案一,已知挠曲变形时的标准Kalman滤波算法;2)方案二,未知挠曲变形时的标准Kalman滤波算法;3)方案三,未知挠曲变形时的H?滤波算法。仿真误差曲线直观表明:基于H?滤波算法可以在未知挠曲变形时有效提高组合精度;统计结果表明:滤波方案三得到的姿态与速度的系统误差、随机误差均与理想条件下的方案一相当;相较于方案二,滤波方案三得到的姿态与速度的系统误差至少可减小40%,随机误差至少可减少15%。     

基于旋转矢量误差模型的舰载机大失准角传递对准技术（英文）

为实现舰载机大方位失准角条件下的快速传递对准,提出采用旋转矢量误差模型。分别推导了速度匹配和速度加角速度匹配的量测模型。为解决非线性滤波器的稳定性和快速性,提出采用平方根无迹卡尔曼滤波SRUKF来估计失准角。仿真结果表明,旋转矢量误差模型相对于非线性的欧拉角误差模型有更高的估计精度。在海况引起的摇摆运动下,运用速度加角速度匹配方法可以在50 s内完成对准,此时水平精度达到20?以内,航向精度达到1?以内。由此表明所提出的算法可以满足舰载机传递对准快速性和精确性的要求。     

Measurement of velocity and velocity derivatives based on pattern tracking in 3D LIF images

Pattern tracking in consecutive 3D LIF images based on least squares matching (LSM) of grey levels has been developed recently for velocity and velocity gradient measurements. The shortcomings of this method are clearly shown. The present article presents an improvement on this method by introducing a local multi-patch (LMP) technique through the LSM approach. The method is validated using the flow field of a turbulent channel flow obtained by direct numerical simulation (DNS) and a synthetic image with grey-level patterns. The results show that LMP matching allows the determination of the velocity and the velocity gradient fields with high accuracy including the second derivatives. Measurements of a round non-buoyant jet are presented which demonstrate the good performance of the method when applied under laboratory conditions. This method can also be applied on two-dimensional images provided that the flow is strictly two-dimensional. Received: 7 July 1999/Accepted: 13 November 1999     

混合式光纤陀螺惯导系统在线自主标定

混合式光纤陀螺惯导系统IMU的安装误差、光纤陀螺的漂移及标度因数等参数会随着时间发生变化,对系统误差产生影响,使系统在使用一段时间之后精度发生变化,因而需要重新标定。在混合式系统中,通过台体旋转调制,惯性元件常值漂移误差对系统的影响得到抑制,但安装误差和标度因数误差对系统的影响无法得到完全调制,这些误差会与地速及旋转角速率耦合,引起锯齿形速度误差,降低了系统的各项性能。针对混合式惯导系统,建立了IMU误差模型,设计出一种在线自主标定方法,并进行了可观性分析。该方法采用"速度+位置"匹配,对惯导系统30项相关误差项进行在线标定。系统实验结果表明,系统级在线标定参数较分立式标定参数在导航定位精度上提高了半个数量级。     

机载分布式POS传递对准建模与仿真

为了提高机载分布式POS中子POS的测量精度,补偿机翼的挠曲变形,提出了一种机载环境下传递对准方法。为验证该方法的有效性,搭建了机载分布式POS地面演示系统。针对该地面演示系统,提出了运用ANSYS辅助力学建模的方法建立了模拟机翼杆挠曲运动模型,并将由机翼挠曲运动产生的挠曲变形角和挠曲变形角速度增广为卡尔曼滤波的状态变量。在此基础上,详细推导了考虑挠曲变形时姿态误差量测方程,设计了基于"速度+姿态"匹配方式的卡尔曼滤波器。仿真结果表明,采用该挠曲变形补偿方法进行传递对准,水平失准角精度优于3?,方位失准角精度优于5?。仿真结果验证了该方案的可行性,为机载分布式POS提供了工程应用参考。     

一种用于无陀螺捷联惯导系统的角速度融合算法

无陀螺捷联惯导系统(GFSINS)是用加速度计的合理空间组合解算出载体的角速度。载体角速度的解算精度是GFSINS的技术关键。在分析GFSINS九加速度计配置方案的基础上,提出一种新的角速度融合算法,消除该方案解算过程中开方计算及符号判断带来的误差。该算法还明显抵消了加速度计输出中包含的常值零点偏移误差和温度漂移误差等,具有实时性好、计算量小、通用性强的优点。仿真计算表明该算法可行,并能在一定程度上提高系统解算精度。     

一种有效的空－空导弹捷联惯导系统快速精确传递对准方法

针对空－空导弹对于准确度与速度的特殊要求,建立了动基座姿态角传递对准的卡尔曼滤波模型,详细及准确地推导了姿态角匹配方案中卡尔曼滤波器的量测方程,提出了一种有效的空－空导弹捷联惯导系统快速精确传递对准方法。通过计算机仿真,验证了该方法的快速性和有效性,最后,采用分级标定的思路,实现了在飞机摇摆机翼情况下,对惯性器件误差的准确标定。     

An entropy fixed cell‐centered Lagrangian scheme

On the basis of the work [P.‐H. Maire, R. Abgrall, J. Breil, J. Ovadia, SIAM J. Sci. Comput. 29 (2007), 1781–1824], we present an entropy fixed cell‐centered Lagrangian scheme for solving the Euler equations of compressible gas dynamics. The scheme uses the fully Lagrangian form of the gas dynamics equations, in which the primary variables are cell‐centered. And using the nodal solver, we obtain the nodal viscous‐velocity, viscous‐pressures, antidissipation velocity, and antidissipation pressures of each node. The final nodal velocity is computed as a weighted sum of viscous‐velocity and antidissipation velocity, so do nodal pressures, whereas these weights are calculated through the total entropy conservation for isentropic flows. Consequently, the constructed scheme is conservative in mass, momentum, and energy; preserves entropy for isentropic flows, and satisfies a local entropy inequality for nonisentropic flows. One‐ and two‐dimensional numerical examples are presented to demonstrate theoretical analysis and performance of the scheme in terms of accuracy and robustness.Copyright © 2013 John Wiley & Sons, Ltd.     

Instantaneous pressure and material acceleration measurements using a four-exposure PIV system

This paper describes a non-intrusive technique for measuring the instantaneous spatial pressure distribution over a sample area in a flow field. A four-exposure PIV system is used for measuring the distribution of material acceleration by comparing the velocity of the same group of particles at different times and then integrating it to obtain the pressure distribution. Exposing both cameras to the same particle field at the same time and cross-correlating the images enables precision matching of the two fields of view. Application of local image deformation correction to velocity vectors measured by the two cameras reduces the error due to relative misalignment and image distortion to about 0.01 pixels in synthetic images. An omni-directional virtual boundary integration scheme is introduced to integrate the acceleration while minimizing the effect of the local random errors in acceleration. Further improvements are achieved by iterations to correct the pressure along the boundary. Typically 3–5 iterations are sufficient for reducing the incremental mean pressure change in each iteration to less than 0.1% of the dynamic pressure. Validation tests of the principles of the technique using synthetic images of rotating and stagnation point flows show that the standard deviation of the measured pressure from the exact value is about 1.0%. This system is used to measure the instantaneous pressure and acceleration distributions of a 2D cavity turbulent flow field and sample results are presented.     

An extension of digital PIV-processing to double-exposed images

 In this paper digital processing techniques for PIV (Partical Image Velocimetry) using double-exposed particle images have been studied. It has been found that a pattern matching technique is significantly superior to the traditional autocorrelation method in the case that a large particle displacement between the double exposures is present on the image. In PIV using double-exposed images, the image shifting technique is usually used to solve the directional ambiguity problem. The performance of PIV using autocorrelation technique is dependent on the flow speed and the amount of image shift applied. This dependence, for example, causes a difficulty of autocorrelation in flows close to a solid boundary. The present study shows that a pattern matching technique eliminates such a difficulty. At the same signal-to-noise ratio, the pattern matching techndique has a better spatial resolution than that of autocorrelation. In concert with the pattern matching technique, PID (Particle Image Distortion) can be applied to double-exposed images, further improving the reliability and accuracy of velocity estimates of PIV in the presence of large velocity gradients. Generally speaking, PIP-matching and PID extend the validity of PIV using double-exposed images. The total processing time required by the PIV using the pattern matching technique and one PID iteration is of the same order as that required by the PIV using autocorrelation. Received: 7 July 1995 / Accepted: 11 September 1997