改进的格网惯导系统无阻尼综合校正方法

综合校正技术可作为抑制格网惯导系统（INS）导航误差的有效手段。加速度计零偏所造成的水平姿态误差是导致综合校正中陀螺漂移估计精度受限的重要因素。针对这一问题，提出了一种改进的无阻尼综合校正方法。首先，推导了格网坐标系框架下估计加速度计零偏和姿态的目标函数；其次，介绍了无阻尼条件下综合校正的两个核心方程；最后设计了无阻尼两点校策略。综合校正前，在多普勒计程仪（DVL）提供的速度辅助下完成加速度计零偏的估计和补偿，以此消除加速度计零偏所造成的水平姿态误差对综合校正中陀螺漂移估计精度的影响。在两次间断的外部位置和航向辅助下通过所设计的综合校正策略完成对陀螺漂移的估计。校正策略中所涉及的水平姿态误差在DVL辅助下由参数估计方法估计得到。仿真及实验结果表明：与现有的研究相比，所设计的综合校正方案进一步减少了DVL的辅助时间，同时由于准确地估计和补偿了加速度计零偏，陀螺漂移的估计精度显著提高，该方案在抑制导航误差方面具备更明显的优势。     

Solitary and periodic waves in magneto–rotating plasmas: Effect of the Kappa–Cairns distributed electrons

The nonlinear propagation of ion–acoustic (IA) waves in a magneto–rotating plasma is studied by considering the Kappa-Cairns electron distribution. Employing the perturbation scheme, Korteweg–de Vries equation is derived. It is seen that both positive and negative potential solitons can be supported in the present plasma model. The numerical results reveal that the Kappa-Cairns distributed electrons modify features of the electrostatic waves significantly. The effects of non–thermal parameters, plasma rotation frequency, ion temperature, and the wave propagation angle on electrostatic solitary wave structures are also discussed here. It is found that the plasma parameters considerably influence the propagation of IA waves in rotating plasmas. Furthermore, using the bifurcation theory of planar dynamical systems to the K-dV equation, we have presented the existence of solitary and periodic traveling waves. Our study may be helpful to understand the behavior of ion–acoustic wave in the rotating plasma.     

Receptivity and structural sensitivity study of the wide vaneless diffuser flow with adjoint method

The stability of the flow in the vaneless diffuser of a centrifugal compressor is studied with the linear theory. The characteristics of direct and adjoint perturbation modes are investigated, and the receptivity of the instability mode to momentum forcing or mass injection is identified based on the adjoint modes. Analysis shows that the perturbation with the largest amplitude is located at the outlet of the vaneless diffuser, while the highest-receptivity region is located in the middle of the vaneless diffuser along the radial direction. The large difference between the direct and adjoint modes indicates that the instability mechanism cannot be identified from a study of either eigenmode separately. Therefore, the structural sensitivity analysis is adopted to study the feedback of the instability mode. The structural sensitivity of the eigenvalue which is proportional to the perturbation pressure and velocity is used to explain the mechanism of flow control for the vaneless diffuser.     

Development of secondary flow field under rotating condition in a straight channel with square cross-section

The developing secondary flow fields in the entrance section of a rotating straight channel were experimentally investigated using Particle Image Velocimetry (PIV). The effects of streamwise position, Reynolds number and rotation number on the development of the secondary flow fields were revealed. The results show that the absolute values of vorticity flux of the trailing side roll cells increase with increasing radius of the measured plane and rotation number. When the absolute value of vorticity flux exceeds a critical value, the merging of the trailing side roll cells appears. Moreover, when the number of the trailing side vortex pairs is even, the absolute values of vorticity flux of the leading side vortices increase along streamwise direction. Otherwise, the absolute values decrease along the streamwise direction. By the circulation analysis, this phenomenon was found to have relationship with the merging of the trailing side roll cells, and further concluded that the secondary flow field in a rotating channel has to be treated as a whole. At last, the increase of the Reynolds number was found to be able to induce the merging position moves upstream.     

带盖板预旋系统的流动实验

通过低转速的模拟实验对涡轮盘腔的带盖板预旋系统的流动特性进行了研究。在不同的紊流参数（0.5〈λT〈0.96）和旋转比（1.03〈βp〈1.9）下测量了预旋腔和盖板腔内的压力与速度分布,得到了两个腔内的旋转比变化情况,并分析了旋转雷诺数和进出口压比对预旋喷嘴流量系数的影响。实验结果表明：在两个腔内离心升压效应明显,预旋喷嘴出口气流对预旋腔内的气流压力和速度的影响要远大于接收孔出口气流对盖板腔的影响,压比和旋转雷诺数对喷嘴流量系数有较小的影响。     

激光陀螺惯性导航系统旋转技术综述

旋转技术能够有效调制激光陀螺和加速度计的误差,提高惯性导航系统的精度。首先基于惯性测量单元的误差模型,分析了旋转技术的基本原理。然后对旋转技术的旋转方案、最优转动速率、旋转机构误差对系统精度的影响、载体角运动对旋转效果的影响、采用旋转技术的惯导解算、采用旋转技术的初始对准与测漂等进行了综述,探讨了我国研究旋转技术的重点研究方向,为开展我国旋转式光学陀螺惯导系统的研究提供了一定参考。     

以恒星位置为基准的运动平台上测控雷达精度标校技术

利用FK5星表，可以精确实时地计算出恒星位置，用作陆基雷达标校的基准。本文把这种技术推广到运动平台上雷达的精度标校，提出了技术方案和初步的数学模型，给出了试验的解算结果和统计结果。     

GPS软件接收机原理样机设计与实现

为了满足GPS/INS(Global Positioning System/Inertial Navigation System)超紧组合导航系统研究的需要,克服硬件接收机参数固定,适应性差的弱点,设计了一种参数可调、灵活控制的GPS软件接收机.采用GPS L1频率的中频采样信号,运用FFT(Fast Fourier Transform)频域捕获算法和锁相环与锁频环相互辅助的载波环路,实现了信号捕获、码环和载波环路跟踪、导航电文提取与解码、伪距及导航定位解算,并与NovAtel公司的FlexPax型硬件接收机进行了比较.跑车测试结果表明,该GPS软件接收机捕获迅速、跟踪准确,导航定位精度小于10m,动态抗干扰能力明显优于一般GPS硬件接收机,适合于GPS/INS超紧组合导航系统的应用.     

模拟旋转内冷通道中压力测量的实验研究

在旋转内冷通道中,用压力传感器测量垂直于旋转轴的矩形管道充动气体的压力分布,实验结果表明：（１）在同一半径处,转速增加引起压差减少,（２）在转速较低时随着半径增大,压差减小,但转速较大,总的压差反而随着半径增大而增大,（３）流体管道中的扰流柱起着增另气流紊流的作用,导致压力损失增大,压降增大。     

GPS/BDS/INS tightly coupled integration accuracy improvement using an improved adaptive interacting multiple model with classified measurement update

An Extended Kalman Filter (EKF) is commonly used to fuse raw Global Navigation Satellite System (GNSS) measurements and Inertial Navigation System (INS) derived measurements. However, the Conventional EKF (CEKF) suffers the problem for which the uncertainty of the statistical properties to dynamic and measurement models will degrade the performance. In this research, an Adaptive Interacting Multiple Model (AIMM) filter is developed to enhance performance. The soft-switching property of Interacting Multiple Model (IMM) algorithm allows the adaptation between two levels of process noise, namely lower and upper bounds of the process noise. In particular, the Sage adaptive filtering is applied to adapt the measurement covariance on line. In addition, a classified measurement update strategy is utilized, which updates the pseudorange and Doppler observations sequentially. A field experiment was conducted to validate the proposed algorithm, the pseudorange and Doppler observations from Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) were post-processed in differential mode. The results indicate that decimeter-level positioning accuracy is achievable with AIMM for GPS/INS and GPS/BDS/INS configurations, and the position accuracy is improved by 35.8%, 34.3% and 33.9% for north, east and height components, respectively, compared to the CEKF counterpart for GPS/BDS/INS. Degraded performance for BDS/INS is obtained due to the lower precision of BDS pseudorange observations.