深空测控通信中GMSK体制非相干解调算法研究

针对深空测控通信中GMSK体制非相干解调损失较大的难点,提出了一种改进的GMSK信号非相干维特比解调算法。通过分析相位状态网格图中相位转移规律,建立理论仿真模型。通过原理样机的研制和测试,实测数据表明：该算法具有解调损失低、实现复杂度适中的优点;相比于理论的最佳相干解调算法,在误码率1×10 -4 量级下,实测仅损失0.6 dB。目前该算法已应用于国内某深空测控通信系统GMSK体制基带设备中,并成功解调出欧空局Herschel–Planck卫星数据。     

Effects of uncertainties and flexible dynamic contributions on the control of a spacecraft full-coupled model

One of the most important problems for performing a good design of the spacecraft attitude control law is connected to its robustness when some uncertainty parameters are present on the inertial and/or on the elastic characteristics of a satellite. These uncertainties are generally intrinsic on the modeling of complex structures and in the case of large flexible structures they can be also attributed to secondary effects associated to the elasticity. One of the most interesting issues in modeling large flexible space structures is associated to the evaluation of the inertia tensor which in general depends not only on the geometric ‘fixed’ characteristic of the satellite but also on its elastic displacements which of course in turn modify the ‘shape’ of the satellite. Usually these terms can be considered of a second order of magnitude if compared with the ones associated to the rigid part of a structure. However the increasing demand on the dimension of satellites due to the presence for instance of very large solar arrays (necessary to generate power) and/or large antennas has the necessity to investigate their effects on their global dynamic behavior in more details as a consequence. In the present paper a methodology based on classical Lagrangian approach coupled with a standard Finite Element tool has been used to derive the full dynamic equations of an orbiting flexible satellite under the actions of gravity, gravity gradient forces and attitude control. A particular attention has been paid to the study of the effects of flexibility on the inertial terms of the spacecraft which, as well known, influence its attitude dynamic behavior. Furthermore the effects of the attitude control authority and its robustness to the uncertainties on inertial and elastic parameters has been investigated and discussed.     

IPDI型HTPB推进剂界面软化因素研究

根据界面推进剂状态和粘接拉伸强度,研究了HTPB—IP—DI推进剂界面软化的影响因素。结果表明,存放期间半固化衬层吸收的水分是HTPB—IPDI推进剂界面软化的根源：衬层吸水量的大小决定界面软化的程度;衬层中的吸水性填料、存放时间和环境湿度影响衬层的吸水量;而衬层中的固化催化剂、推进剂中的碱性功能助剂ZGY及高固化温度等因素对界面软化起着明显的促进作用。     

基于Contourlet与HIS变换的SAR与多光谱影像融合方法

为了提高SAR影像的解译水平,本文利用Contourlet变换在影像表述上能够弥补小波变换不能有效捕捉二维空间实体的特点,提出了一种基于Contourlet与HIS变换的SAR与多光谱影像融合方法。实验选取了一组TM 多光谱影像与ERS-2 SAR影像进行融合研究,并将融合结果与基于HIS变换、DWT结合HIS变换融合方法的融合结果进行视觉比较与统计分析。结果表明,无论是目视比较还是统计分析,本文方法都很好的将SAR影像的空间细节与多光谱影像的色彩信息集成到了一起,显著地提高了SAR影像的解译水平,相对于基于HIS、DWT+HIS变换的融合方法获得了更好质量的融合影像。     

对解线频调ISAR的间歇采样转发干扰

针对间歇采样转发应用于宽带ISAR干扰问题,研究了间歇采样转发信号经解线频调ISAR二维成像处理后信号特性,通过推导干扰信号对应的二维输出形式,讨论了干扰图像变化情况并由此分析了间歇采样周期和占空比对干扰效果的影响。利用数字仿真验证了干扰输出形式及图像特征理论分析的正确性;将实测数据与间歇采样转发处理相结合,初步验证了间歇采样转发干扰能够形成二维ISAR假目标。     

空间机器人在轨更换ORU的力/位混合控制方法

针对ORU在轨更换任务,首先推导了空间机械臂末端自由、末端与环境接触等情况下的动力学方程,并提出了相应的接触力计算方法;其次,改进了传统的R\|C控制方法,采用加权选择矩阵代替原有的选择矩阵,实现了力控制与位置控制之间的平滑切换;最后,开发了基于Matlab/Simulink的闭环控制仿真系统,该系统由多体动力学、接触动力学、轨迹规划、力/位混合控制、3D显示等模块组成。利用该系统开展了ORU转移与安装过程的闭环控制仿真,仿真结果校验了所提方法的有效性。     

飞轮扰动经验模型参数的识别与改进

对飞轮扰动模型参数的精确识别是研究光学卫星高稳定度、高分辨率成像的基础. 目前, 飞轮的扰动模型识别主要有两种: 经验模型和分析模型. 经验模型需要识别的参数是谐波级数和幅值系数, 而当前存在的参数识别算法忽略了时域截断的影响, 导致幅值系数识别存在较大偏差, 这会引起扰动响应分析的不确定性. 针对上述情况, 提出了窗函数法和与其相关的频域恢复技术, 有效弥补了时域截断的影响. 通过实验仿真结果可见, 该方法大幅度提高了幅值系数的识别精度.      

基于稳频电路的差动控制系统研究

本文从理论上说明背向散射与锁区的关系,给出了如何减小背向散射对激光陀螺影响的方法。利用该原理设计了基于稳频电路的差动控制系统,并对其进行了试验验证,得到了良好的试验结果。为进一步进行差动控制的试验提供了参考依据,也为稳频系统电路设计提供了改进方向和依据。     

Soybean cultivar selection for Bioregenerative Life Support Systems (BLSSs) – Hydroponic cultivation

Four soybean cultivars (‘Atlantic’, ‘Cresir’, ‘Pr91m10’ and ‘Regir’), selected through a theoretical procedure as suitable for cultivation in BLSS, were evaluated in terms of growth and production. Germination percentage and Mean Germination Time (MGT) were measured. Plants were cultivated in a growth chamber equipped with a recirculating hydroponic system (Nutrient Film Technique). Cultivation was performed under controlled environmental conditions (12 h photoperiod, light intensity 350 μmol m⁻² s⁻¹, temperature regime 26/20 °C light/dark, relative humidity 65–75%). Fertigation was performed with a standard Hoagland solution, modified for soybean specific requirements, and EC and pH were kept at 2.0 dS m⁻¹ and 5.5 respectively.     

一种共轴双旋翼式火星飞行器设计及其试验验证

针对火星飞行器探测需求,提出了一种共轴双旋翼式火星飞行器,基于计算流体力学方法优选了桨叶翼型、平面形状和扭转角等结构参数,基于叶素动量理论建立了旋翼气动力学模型,利用数值模拟方法选择了旋翼转速、旋翼间距和桨叶安装角等飞行参数,设计了原理样机"火星飞鸟-I"的结构与控制系统。构建了火星大气环境模拟器和重力补偿与运动约束装置,开展了模拟火星环境下旋翼式飞行器地面飞行试验,验证了共轴双旋翼式火星飞行器的推进性能,展望了旋翼式火星飞行器技术的发展方向。研究成果对我国开展的火星探测工程具有重要借鉴价值。