适应于极区的惯导系统传递对准技术研究

针对飞机、舰艇全球航行的需求,以及由地球经线在极区收敛而导致的以真北向作为航向参考时的导航算法失效问题,在传统的“速度+姿态”匹配对准及修正算法的基础上,提出了格网导航系下的“速度+姿态”传递对准方法。基于格网导航系下惯性导航算法的编排,建立了格网坐标系的惯导误差模型,推导了格网导航系“速度+姿态”匹配的量测方程,利用卡尔曼滤波器对子惯导的速度、失准角、陀螺漂移、加速度计零偏、主子惯导间的安装误差角等进行了估计与修正。数学仿真及基于极区航行试验数据的半实物仿真结果表明,采用本文提出的格网导航系下的“速度+姿态”匹配传递对准算法,可实现中低精度惯导系统在高纬度地区时间为30s、水平对准精度优于1角分、方位对准精度优于6角分的快速、高精度对准。     

Influence of SPS casing treatment on axial flow compressor subjected to radial pressure distortion

The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed (SPS) casing treatment when fan/compressor suffers from a radial total pres-sure inlet distortion. Experimental researches are conducted on a low-speed compressor with and without SPS casing treatment under radial distorted inlet flow of different levels as well as uniform inlet flow. The distorted flow fields of different levels are generated by annular distortion flow gen-erators of different heights. The characteristic curves under these conditions are measured and ana-lyzed. The results show that the radial inlet distortion could cause a stall margin loss from 2% to 30% under different distorted levels. The SPS casing treatment could remedy this stall margin loss under small distortion level and only partly make up the stall margin loss caused by distortion in large level without leading to perceptible additional efficiency loss and obvious change of charac-teristic curves. The pre-stall behavior of the compressor is investigated to reveal the mechanism of this stall margin improvement ability of the SPS casing treatment. The results do show that this casing treatment delays the occurrence of rotating stall by weakening the pressure perturbations and suppressing the nonlinear amplification of the stall precursor waves in the compression system.     

INTEGRATED GPS/INS OF PSEUDO-RANGE DELTA-RANGE SEMI-PHYSICAL SIMULATION'S RESEARCH

In order to further study the performance of tightly integrated navigation system of GPS/INS, a semi-physical simulation of tightly coupled system has been done based on the data gathered from the experiment of integrated system of GPS and INS. The closed-loop Kalman Filter and U-D discompose algorithm have been used. The simulation results associated to four integrated models of pseudo-range, delta-range, pseudo-range and delta-range alternation, and pseudo-range and delta-range synthesis have been provided, and the actual effects of variously integrated models have been analyzed. The results show that the pseudo-range and delta-range synthesis coupled model is the most effective to improve the coupled system performance and the individual delta-range coupled model had better be avoided in application.     

步进电机转速稳定度的测定与分析

在分析低速扫描中步进电机转速质量影响的基础上，介绍了用光电编码器测量转速稳定度的方法以及判定标准，并讨论了不同条件下步距角、惯性负载和微步距驱动对步进电机转速稳定度的影响。     

INS／GPS／TERCOM组合制导系统中的信息融合方法研究

提出由坐标变换、误匹配检测和卡尔曼滤波三个单元构成的一种新型INS／GPS／TERCOM系统优化结构，并对INS／GPS／TERCOM组合系统自适应联邦滤波信息融合和分散式信息融合两种算法分别进行了研究，将这两种算法与传统的集中滤波算法进行了比较。结果表明，系统无故障情况下三种方法精度相同；而在有故障情况下自适应联邦融合法优于另两种方法。     

基于置信度加权的组合导航数据融合算法

 针对联邦滤波融合算法中由于模型量测噪声统计特性未能被准确描述导致其子滤波器误差变大,进而导致联邦滤波估计出现偏差的问题,为了改进联邦滤波融合方法,将模糊自适应卡尔曼滤波方法和置信度加权方法与联邦滤波融合方法相结合,应用于组合导航系统。该方法首先将模糊自适应卡尔曼滤波方法应用于各子滤波器,使其能够跟踪真实量测噪声统计特性。然后通过模糊方法计算得到各子滤波器的置信度,进而得到联邦滤波器的置信度,再由得到的置信度对各子滤波器及联邦滤波器输出进行加权,得到最终的全局输出。对车载组合导航系统的仿真结果表明,这种算法对量测噪声具有较强的自适应性,能够抑制置信度低的子滤波器在融合系统中所占的权重,提高联邦滤波融合算法的精度,是一种可行的车载组合导航数据融合算法。     

压气机旋转不稳定性的研究进展

在压气机运行过程中,旋转不稳定是一种常见的流动不稳定现象.研究旋转不稳定性对保障压气机安全高效工作具有重要意义.首先回顾了旋转不稳定性研究的发展历程,从概念特征、产生机制和影响因素等方面进行了介绍.从现有的研究情况来看,旋转不稳定性与叶顶泄漏流有关的动力学模式或者与剪切层不稳定性有关.随后,梳理了旋转不稳定性的若干研究...     

Design and optimization of supersonic turbines for detonation combustors

Detonation-based engines offer a potential surge in efficiency for compact thermal power systems. However, these cycles require ad-hoc components adapted to the high outlet velocity from the detonation combustors. This paper presents the design methodology of turbine stages suitable for supersonic inlet conditions and provides a detailed analysis of optimized turbine geometries. A reduced-order solver examines the supersonic blade rows’ functional design space, quantifies the turbine’s non-isent...     

部分模糊度固定方法在GNSS/INS紧组合中的应用研究

针对动态环境下GNSS/INS导航定位模糊度固定难的问题,提出了一种基于部分模糊度固定的GNSS/INS紧组合导航定位算法,通过选择模糊度的最优子集进行固定,并利用实测车载实验进行了算法验证.实验结果表明:在开阔环境下,基于部分模糊度固定的GNSS/INS紧组合与基于全模糊度固定的GNSS/INS紧组合算法的定位精度相...     

Quadratic extended Kalman filter approach for GPS/INS integration

GPS/INS integration system has been widely applied for navigation due to their complementary characteristics. And the tightly coupled integration approach has the advantage over the loosely coupled approach by using the raw GPS measurements, but hence introduces the nonlinearity into the measurement equation of the Kalman filter. So the typical method for navigation using measurements of range or pseudorange is by linearizing the measurements in an extended Kalman filter (EKF). However, the modeling errors of the EKF will cause the bias and divergence problems especially under the situation that the low quality inertial devices are included. To solve this problem, a quadratic EKF approach by adding the second-order derivative information to retain some nonlinearities is proposed in this paper. Simulation results indicate that the nonlinear terms included in the filtering process have the great influence on the performance of integration, especially in the case that the low quality INS is used in the integrated system. Furthermore, a two-stage cascaded estimation method is used, which circumvents the difficulty of solving nonlinear equations and greatly decreases the computational complexity of the proposed approach, so the quadratic EKF approach proposed in this paper is of great value in practice.