An active damping vibration control system for wind tunnel models

In wind tunnels, long cantilever sting support systems with low structural damping encounter flow separation and turbulence during wind tunnel tests, which results in destructive low-frequency and big-amplitude resonance, leading to data quality degradation and test envelope limitation. To ensure planed test envelope and obtain high-quality data, an active damping vibration control system independent of balance signal based on stackable piezoelectric actuators and velocity feedback using accelerometer, is proposed to improve the support stability and wind tunnel testing safety in transonic wind tunnel. Meanwhile, a design of powerful sting-root embedded active damping device is given and an active vibration control method is presented based on the mechanism analysis of aircraft model vibration. Furthermore, a self-adaptive fuzzy Proportion Differentiation(PD) control model is proposed to realize control parameters adjustment automatically for various testing conditions. Besides, verification tests are performed in laboratory and a continuous transonic wind tunnel. Experimental results indicate that the aircraft model does not vibrate obviously from -4° to 11° at Ma = 0.6, the number of useable angle-of-attack has increased by 7° at Ma = 0.6 and 5° at Ma = 0.7 respectively, satisfying the requirements of practical wind tunnel tests.     

一种基于数据融合的加速度传感器的静态模型辨识方法

通过对现有加速度传感器静态模型参数辨识方法进行分析,指出传统的算术平均值法在实现加速度传感器静态模型参数辨识中存在的缺陷,提出了数据融合方法,并对其进行了讨论。数据融合方法是将来自同一目标的多源数据加以智能化合成,从而产生比单一数据源更精确更完全的估计和判决。通过分析表明,采用数据融合方法进行参数辨识得到的参数的离散度小于传统的算术平均值法所求参数的离散度,使模型参数的精度有明显提高。因此数据融合方法优于传统的算术平均值法,特别适合于加速度传感器静态模型参数的辨识。该方法的提出为控制系统的实时补偿提供了良好的条件。     

LXJ-70型精密离心机

精密离心机是用于惯导加速度计校准的重要设备之一 ,本文介绍了最新研制的 L XJ-70型精密离心机组成部分、分系统的设计方法、关键技术及其主要性能     

激光捷联惯性/卫星组合导航系统基本原理及应用情况

激光捷联惯性/卫星组合导航系统是国外飞机上普遍采用的一种导航设备,但在国内飞机上的应用则刚刚起步。本文简要介绍了激光捷联惯性/卫星组合导航系统的基本原理及应用情况。     

捷联惯导加速度计尺寸效应误差建模及其标定

高动态条件下,加速度计（简称加计）的尺寸效应将成为捷联惯导系统精确导航的重要误差源。这个误差源于加计组合中三个加计振动中心（有效的加速度测量点）的不重合。从几何角度对加计尺寸效应误差进行了建模。设计了三类基于精密三轴速率转台的加计尺寸标定方案,即匀角速度旋转、匀角加速度旋转和正弦角加速度旋转方案。以旋转过程中捷联惯导系统的速度输出作为量测,利用Kalman滤波器可以实现对加计尺寸系数的有效估计。利用分段定常系统可观性分析方法研究表明,三类旋转标定机动均能使系统状态完全可观测。仿真结果证明了三类标定方案的有效性,而以匀角速度旋转方案估计过程最平稳,以正弦角加速度旋转方案估计精度最高。     

石英摆片激光切割技术研究

针对激光切割技术在典型石英结构——加速度计摆片加工成形中的应用,探讨了激光与石英材料的作用机理,进行了激光切割成形以及消应力试验。在此基础上详细分析了激光切割工艺参数和后处理对石英摆片成形质量的影响,对精密石英结构的制造具有普遍的意义。     

重力测量技术与惯性技术之间的关系

以加速度计为代表的惯性器件技术和以惯性稳定平台为代表的惯性系统技术,极大地推动了重力仪和重力梯度仪的发展。重力测量技术的不断进步,也有效支撑惯性导航系统性能的不断提升,并牵引了惯性技术研究的不断深入。国内惯性技术领域应将重力测量仪器研制作为一项长期而重要的主题,研制过程中应充分发掘现有技术潜力加快研制进度,并注重产品小型化和轻量化设计,推进重力/重力梯度测量技术协同发展,不断提高技术水平,拓展产品应用领域,推进惯性技术的可持续发展。     

加速度计专用动态实验装置

介绍一种既能实现加速度计在离心机上的动态实验测试 ,也能实现静态实验测试的装置。详述了影响整个系统性能的干扰问题的硬件及软件解决方法。     

Magnetic torquer induced disturbing signals within GRACE accelerometer data

The GRACE (Gravity Recovery And Climate Experiment) gravity field satellite mission was launched in 2002. Although many investigations have been carried out, not all disturbances and perturbations upon satellite instruments and sensors are resolved yet. In this work the issue of acceleration disturbances onboard of GRACE due to magnetic torquers is investigated and discussed. Each of the GRACE satellites is equipped with a three-axes capacitive accelerometer to measure non-gravitational forces acting on the spacecraft. We used 10 Hz Level 1a raw accelerometer data in order to determine the impact of electric current changes on the accelerometer. After reducing signals which are induced by highly dominating processes in the low frequency range, such as thermospheric drag and solar radiation pressure, which can easily be done by applying a high-pass filter, disturbing signals from onboard instruments such as thruster firing events or heater switch events need to be removed from the previously filtered data. Afterwards the spikes which are induced by the torquers can be very well observed. Spikes vary in amplitude with respect to an increasing or decreasing current used for magnetic torquers, and can be as large as 20 nm/s². Furthermore, we were able to set up a model for the spikes of each scenario with which we were able to compute model spike time series. With these time series the spikes can successfully be removed from the 10 Hz raw accelerometer data. Spectral analysis of the time series reveal that an influence onto gravity field determination due to these effects is very unlikely, but can theoretically not be excluded.     

Performance of GPS-based accelerometry: A simulation experiment

Recent studies have shown that with the availability of high-quality CHAMP and GRACE gravity field models, it is feasible to determine accurate non-gravitational accelerations for low Earth orbiting satellites indirectly from precise GPS satellite-to-satellite observations. Possible applications of this so-called GPS-based accelerometry approach consist of accelerometer calibration and atmospheric density and wind computations. With the growing number of high-quality space-borne GPS receivers, this method could be applied to a large range of satellites. In this paper an extensive simulation study has been carried out, based on real accelerometer data from the GRACE mission, in order to determine the optimal processing strategy and the resulting accuracy of the estimated non-gravitational accelerations. It is shown that the optimal processing strategy consists of a piecewise linear parameterization of the estimated empirical accelerations, together with short 6-h orbit arcs. The GPS-based accelerometry approach makes use of triple-differenced GPS observations and the impact of considering the correlated observation noise was found to be marginal in the presence of other error sources such as GPS ephemeris errors. Using a priori non-gravitational force models improves the recovery of low temporal resolution accelerations, except during huge geomagnetic storms. With this strategy, non-gravitational accelerations can be recovered during high solar activity with an accuracy of better than 10% of the total signal in along-track direction and around 25–40% in cross-track direction, at time resolutions of around 8–20 min. During solar minimum conditions, the relative recovery error will increase to approximately 50% in along-track direction and around 60–70% in cross-track direction, due to the reduced atmospheric drag signal. Unfortunately, GPS-based accelerometry is hardly sensitive in the radial direction.