空间晶体生长炉综合控制方法

空间晶体生长炉控制对象复杂, 具有纯滞后、强耦合、非线性等不利于控制的特性. 为实现炉温的精确控制, 提出了一个空间晶体生长炉综合控制方法并通过软件来实现. 将相关系数法和增广递推最小二乘法相结合, 辨识系统模型, 使用Hooke-Jeeves模式搜索法进行PID参数的自整定, 采用PID加前馈控制的算法对系统进行仿真, 使用同样的算法和控制参数对空间晶体生长炉进行实时控制, 并在控制的过程中实时调整控制参数, 以达到最佳的控制结果. 实验结果表明, 当三个温区的温度均达到700oC时, 温度稳定度小于±0.3oC, 满足系统设计要求. 同时介绍了实现综合控制软件的基本原理、功能、特点及在实际中的应用. 实际工程的应用结果表明, 该软件可满足空间晶体生长炉对控制系统的要求.      

Generating precise and homogeneous orbits for Jason-1 and Jason-2

Driven by the GMES (Global Monitoring for Environment and Security) and GGOS (Global Geodetic Observing System) initiatives the user community has a strong demand for high-quality altimetry products. In order to derive such high-quality altimetry products, precise orbits for the altimetry satellites are a necessity. With the launch of the TOPEX/Poseidon mission in 1992 a still on-going time series of high-accuracy altimetry measurements of ocean topography started, continued by the altimetry missions Jason-1 in 2001 and Jason-2/OSTM in 2008. This paper contributes to the on-going orbit reprocessing carried out by several groups and presents the efforts of the Navigation Support Office at ESA/ESOC using its NAPEOS software for the generation of precise and homogeneous orbits referring to the same reference frame for the altimetry satellites Jason-1 and Jason-2. Data of all three tracking instruments on-board the satellites (beside the altimeter), i.e. GPS, DORIS, and SLR measurements, were used in a combined data analysis. About 7 years of Jason-1 data and more than 1 year of Jason-2 data were processed. Our processing strategy is close to the GDR-C standards. However, we estimated slightly different scaling factors for the solar radiation pressure model of 0.96 and 0.98 for Jason-1 and Jason-2, respectively. We used 30 s sampled GPS data and introduced 30 s satellite clocks stemming from ESOC’s reprocessing of the combined GPS/GLONASS IGS solution. We present the orbit determination results, focusing on the benefits of adding GPS data to the solution. The fully combined solution was found to give the best orbit results. We reach a post-fit RMS of the GPS phase observation residuals of 6 mm for Jason-1 and 7 mm for Jason-2. The DORIS post-fit residuals clearly benefit from using GPS data in addition, as the DORIS data editing improves. The DORIS observation RMS for the fully combined solution is with 3.5 mm and 3.4 mm, respectively, 0.3 mm better than for the DORIS-SLR solution. Our orbit solution agrees well with external solutions from other analysis centers, as CNES, LCA, and JPL. The orbit differences between our fully combined orbits and the CNES GDR-C orbits are of about 0.8 cm for Jason-1 and at 0.9 cm for Jason-2 in the radial direction. In the cross-track component we observe a clear improvement when adding GPS data to the POD process. The 3D-RMS of the orbit differences reveals a good orbit consistency at 2.7 cm and 2.9 cm for Jason-1 and Jason-2. Our resulting orbit series for both Jason satellites refer to the ITRF2005 reference frame and are provided in sp3 file format on our ftp server.     

Drag balance Cubesat attitude motion effects on in-situ thermosphere density measurements

The dynamics of Cubesats carrying a drag balance instrument (DBI) for in situ atmosphere density measurements is analyzed. Atmospheric drag force is measured by the displacement of two light plates exposed to the incoming particle flow. This system is well suited for a distributed sensor network in orbit, to get simultaneous in situ local (non orbit averaged) measurements in multiple positions and orbit heights, contributing to the development and validation of global atmosphere models. The implementation of the DBI leads to orbit normal pointing spinning two body system. The use of a spin-magnetic attitude control system is suggested, based only on magnetometer readings, contributing to making the system simple, inexpensive, and reliable. It is shown, by an averaging technique, that this system provides for orbit normal spin axis pointing. The effect of the coupling between the attitude dynamics and the DBI is evaluated, analyzing its frequency content and showing that no frequency components arise, affecting the DBI performance. The analysis is confirmed by Monte Carlo numerical simulation results.     

太阳帆航天器被动姿态控制研究

针对由有效载荷、太阳帆和4个控制叶片所组成的太阳帆航天器系统,从物理模型出发,利用欧拉方程建立了姿态动力学模型,并通过数值仿真对太阳帆航天器基于控制叶片的对日定向性能进行了研究。研究结果表明,在行星际飞行中太阳帆航天器可以通过使控制叶片保持偏置来保持姿态稳定。     

基于B-Splines网络的飞行姿态控制器设计

设计了一种自适应飞行姿态控制器,在某一飞行条件下,建立了某型飞机的滚转通道动态逆模型,针对动态逆控制需要获得飞机精确数学模型的难点,基于B-Splines函数,构建了B-Splines网络,在线逼近模型逆误差,并根据李亚普诺夫能量函数推导了B-Splines网络权值的更新算法,确保模型跟踪误差和网络权值的有界性。仿真结果表明,该控制器能够对模型逆误差快速自适应,系统对输入命令有较好的响应特性。     

基于Gauss-Newton和UKF结合的微小卫星姿态确定算法

为提高微型低成本姿态敏感器的姿态确定精度,文章基于磁强计/太阳敏感器/陀螺的姿态敏感器配置,设计了高斯牛顿（Gauss-Newton,GN）迭代算法和无迹卡尔曼滤波（Unscented Kalman Filter,UKF）有机结合的微小卫星姿态确定算法,先用Gauss-Newton算法融合磁强计和太阳敏感器的数据,迭代计算最优四元数,然后以最优四元数联合陀螺数据作为观测量,以姿态四元数和惯性系下的角速度为状态量进行UKF,降低观测维数,并将观测方程转化为线性方程,显著减小计算量,同时克服了测量误差对姿态确定精度的影响。     

卫星姿态大角度机动的轨迹规划和模型预测与反演控制

空间科学观测、态势感知、对地遥感、操控服务等应用对卫星提出了高精度、高稳定度、平稳柔顺大角度姿态机动的需求。采用欧拉角形式,对时变、非线性卫星姿态动力学系统进行了分析与建模,将每一个测控周期视为一个姿态机动过程。基于动力学系统受控运动的规律,在每一个姿态跟踪机动过程中,预测姿态偏差,通过卫星姿态演化的反演得到控制指令。以三角函数为基础,设计了一种卫星姿态大角度机动的运动轨迹规划方法。本文所述的轨迹规划及控制方法具有轨迹跟踪精度高、稳定性好,跟踪和机动过程平稳柔顺的特点。数学仿真验证了该方法的可行性和有效性。 关键词：轨迹规划; 模型预测与反演控制; 卫星姿态; 大角度机动     

一种基于李群描述的深空探测器姿态估计方法

针对深空探测器姿态估计问题,提出了一种基于星敏感器的深空飞行器姿态估计新型算法,用李群替代了传统的四元数来描述姿态,避免了四元数转换为姿态矩阵产生的非唯一性和复杂计算等问题。该算法给出了基于星敏感器的姿态观测方程和空间中刚体的运动学模型在李群下的描述并提出了一种基于李群的滤波算法,完成了深空飞行器动态姿态的确定。该线性化模型解决了传统非线性模型在滤波过程中产生的误差,同时省去了四元数转化为姿态矩阵的步骤,减少了计算量。最后,仿真实验中对比了传统的基于四元数的姿态确定算法,可以看出该算法具有更好的稳定性和准确性。     

基于LightGBM的HXMT在轨运行模式监测算法

HXMT卫星的空间硬X射线巡天和定点观测计划切换频繁,需要对卫星有效载荷在轨状态进行实时监测和判别.目前采用的是地面监测人员根据总结的规则进行人工监测的方式,虽然执行方便,可解释性强,但人力消耗较大,且对规则之外的情况无法灵活处理.本文利用HXMT卫星的实时遥测数据,提出一种基于LightGBM机器学习模型的在轨运行模式监测算法,将监测工作规约为多分类问题,并构建判别模型,对卫星在轨运行模式进行判断.在保障判别准确率的前提下,算法模型构建迅速,具有很高的实用性.基于真实遥测数据的试验表明,模型的判别准确率达到99.9%,满足在轨运行模式监测要求,可为HXMT卫星的运行监控任务提供参考依据.      

基于事件触发的航天器姿态自适应容错控制

针对航天器通信和计算资源约束以及执行器故障场景下的姿态控制问题,提出了一种基于事件触发的航天器姿态自适应容错控制策略。首先,采用自适应方法估计故障信息、外界扰动等系统中未知参数,并引入事件触发机制,在执行器故障下实现容错控制的同时,节约星载计算机的计算资源。然后,基于李雅普诺夫方法证明了所提出的控制策略保证了闭环系统状态全局一致且最终有界稳定,并能有效避免Zeno现象,保证了执行器故障场景下对姿态的精确控制。最后,应用于航天器的姿态稳定试验,仿真结果验证了该方法的有效性。