基于角速率和速度增量的捷联惯性导航算法研究

捷联惯性导航算法一般是基于惯性器件输出为角速率、比力或角增量、速度增量进行设计的,不能直接应用于陀螺输出为角速率、加速度计输出为速度增量的捷联惯性导航系统。为了解决此问题和满足精度要求,重新设计了一套捷联惯性导航算法:姿态更新算法采用了经典的四阶龙格-库塔法,推导出了一种新的速度更新算法,该算法可以有效补偿速度计算中的划桨效应误差。仿真结果表明,该种速度更新算法仿真速度快、精度高,具有一定的工程实用价值。     

无轴向通流对转轴间的流动与传热特性

为研究航空发动机对转轴间的流动与换热,建立了无轴向通流的对转环腔湍流边界层的修正卡门三层结构速度分布模型。基于该速度分布模型并依据动量传递与热量传递的比拟理论,推导了外轴内壁面换热努塞尔数的表达式及准则关系式。与CFD数值计算的速度分布、外轴内壁面换热努塞尔数进行对比验证,结果表明,对转环腔湍流边界层的修正卡门三层结构模型给出了一致的速度分布和换热规律。理论与CFD计算得到的外轴内壁面换热努赛尔数在低旋转雷诺数下符合较好,高旋转雷诺数下偏离不超过20%。     

Slip boundary conditions for rough surfaces

The velocity slip and temperature jump for a two-dimensional rough plate under hypersonic conditions were analyzed using the Direct Simulation Monte Carlo (DSMC) method. Surface roughness was explicitly modeled by introducing various structures on the flat plate. The influences of relative roughness height, which involves the roughness height, roughness spacing, incoming velocity, and the degree of rarefaction, were analyzed and discussed. It is found that with the increase of the relative roughness height, the jump temperature increases, while the slip velocity decreases gradually. The effects of surface roughness on the slip coefficients can be attributed to the change of accommodation coefficients. A new slip model for rough surfaces was established in this paper, which accounts for the coupling effects of gas rarefaction and surface roughness, without the effort to model the surface roughness explicitly. The nitrogen flows in the microchannel, and flows over a blunt cone and an axisymmetric bi-conic body, were simulated under the modified and conventional slip boundary conditions, respectively. The numerical solutions were validated with experimental data. It can be safely concluded that compared with the traditional first-order slip boundary conditions, the modified slip model improves the accuracy of macroscopic properties, especially the heat transfer coefficient.     

CCD互相关粒子图像测速及其在对抗流流场测量中的应用

在常规自相关粒子图像测速（ＰＩＶ）系统的基础上,发展了一个采用ＣＣＤ像机的互相关粒子图像测速系统。用这一新系统测量了对抗流流场的结果表明,这一技术克服了自相关粒子图像测速技术在测量具有滞止点的流场中的困难。实验说明,与自相关粒子图像测速技术相比,这一技术更快捷有效。     

3D—PDA测量2相流场时散射粒子的选择

应用激光技术测量流体速度时，需要合适的散射粒子。本文研究了激光三维粒子动态分析仪（３Ｄ－ＰＤＡ）测量２相流场速度时，如何选择合适散射粒子的问题。研究结果表明，散射粒子的合理选择是保证测量精度的重要措施之一；测量湍流脉动较强流场时，应选用密度小、直径小、折射率大的粒子作散射粒子，并选择合适的粒子散播浓度。     

“速度积分”匹配传递对准方法研究

传递对准时,飞机机翼的弹性变形会对挂在机翼上导弹的子惯导系统的对准精度产生很大的影响。本文研究了"速度积分"匹配传递对准方法,通过与速度匹配和"速度+姿态"匹配方法的仿真结果进行比较得出以下结论:"速度积分"匹配方法比速度匹配和"速度+姿态"匹配方法更适用于机翼存在较大弹性变形时的传递对准。另外,此种方法对由时间延迟所引起的时间标记偏差也有比较好的估计效果。     

测速雷达的电波折射简易修正方法及精度分析

为尽量简化多测速雷达定轨系统的气象测量，探讨了采用Hopfield对流层折射指数模型代替探空气象测量的适用性。主要分析了采用Hopfield模型与采用实际探空测量数据的折射误差修正量差别，目标轨迹误差对修正量的影响，以及气象参数对修正量的影响。     

Present-day crustal movement of the Chinese mainland based on Global Navigation Satellite System data from 1998 to 2018

A total of more than 260 continuous stations and 2000 campaign stations from the Crustal Movement Observation Network of China (CMONOC) project, covering the Chinese mainland and its surrounding areas during the period of 1998–2018, are processed using the Bernese Global Navigation Satellite System (GNSS) software via a state-of-the-art method. We obtain the coordinate time series of all the stations given in the reference frame ITRF2014, estimate the coseismic deformation, and remove outliers. Lastly, we present the latest, most complete, and most accurate contemporary horizontal velocity field with respect to the stable Eurasian plate, irrespective of the postseismic deformations. This study shows that the signal of tectonic movement in Western China is stronger than that in Eastern China particularly in the Tibetan Plateau, with a rate of 18–32?mm/a. Moreover, the signal decays sharply from south to north. However, North China and South China move coherently to the ESE direction mostly at a rate of 4–10?mm/a and have not experienced any abrupt velocity gradients in their interiors. Meanwhile, Northeast China has the lowest velocity of only 2–4?mm/a in addition to the coastal areas that have slightly larger velocities. The densified and continuous observation of GNSS stations are of great significance to the study of the present-day crustal movement and tectonic deformation characteristics of the Chinese mainland. This would help to provide better constraints on the kinematics and dynamics of the region.     

Initial accuracy and reliability of current BDS-3 precise positioning,velocity estimation,and time transfer (PVT)

The primary system of Chinese global BeiDou satellite system (BDS-3) was completed to provide global services on December 27, 2018; this was a key milestone in the development process for BDS in terms of its provision of global services. Therefore, this study analyzed the current performance of BDS-3, including its precise positioning, velocity estimation, and time transfer (PVT). The datasets were derived from international GNSS monitoring and assessment system (iGMAS) tracking networks and the two international time laboratories in collaboration with the International Bureau of Weights and Measures (BIPM). With respect to the positioning, the focus is on the real-time kinematic (RTK) positioning and precise point positioning (PPP) modes with static and kinematic scenarios. The results show that the mean available satellite number is 4.8 for current BDS-3 system at short baseline XIA1–XIA3. The RTK accuracy for three components is generally within cm level; the 3D mean accuracy is 8.9 mm for BDS-3 solutions. For the PPP scenarios, the convergence time is about 4 h for TP01 and BRCH stations in two scenarios. After the convergence, the horizontal positioning accuracy is better than cm level and the vertical accuracy nearly reaches the 1 dm level. With respect to kinematic scenarios, the accuracy stays at the cm level for horizontal components and dm level for the vertical component at two stations. In terms of velocity estimation, the horizontal accuracy stays at a sub-mm level, and the vertical accuracy is better than 2 mm/s in the BDS-3 scenario, even in the Arctic. In terms of time and frequency transfer, the noise level of BDS-3 time links can reach 0.096 ns for long-distances link NT01–TP02 and 0.016 ns for short-distance links TP01–TP02. Frequency stability reaches 5E–14 accuracy when the averaging time is within 10,000 s for NT01–TP02 and 1E–15 for TP01–TP02.     

优化速差补偿方案的激光角反射器设计研究

在分析光学角反射器速差补偿两种经典方法的基础上，指出在实际工程设计中速差补偿方案的选取不是由某一种方法独立实现的，而是两种方法的综合体现。据此给出了适合工程设计特点的差速补偿方法考虑。