Modeling and attitude control of CubeSat utilizing moving mass actuators

Any vehicle propelled by solid rocket motors (SRMs) must include an attitude control system capable of dealing with the torque generated by thrust misalignment. In order to expand the application of SRMs on CubeSats, an attitude control system utilizing moving mass actuators is discussed. The present research develops an eight-degree-of-freedom simulation model of a 2U CubeSat with two moving mass actuators. That model also considers the influence of propellant combustion processes. By analyzing the model disturbance source and systematic coupling, the key layout parameters are designed and a simplified control model is proposed. The controller is derived based on a combination of backstepping and sliding mode techniques. An orbit maneuver from 300 km circular orbit to 300 and 500 km elliptical orbit using this attitude control system is verified.     

Space object material identification method of hyperspectral imaging based on Tucker decomposition

Space object material identification method based on Tucker decomposition is proposed and demonstrated experimentally. Space target generally has a low spatial resolution because of the limitation in detection distance. Hyperspectral imaging (HSI) technology can capture the image from visible light to shortwave infrared continuously while providing the spatial and spectral information of the target, thereby introducing a new space target detection and identification approach. However, the data obtained by the HSI system often contain mixed pixels, thereby causing difficulties in target material identification. In this work, a material identification method of hyperspectral data based on Tucker decomposition is proposed by combining mixed spectral theory with tensor decomposition. The feasibility of the method is verified by using satellite model hyperspectral data with different spatial resolutions compared with the endmember obtained from the non-negative matrix decomposition (NMF), independent component analysis (ICA), tensor singular value decomposition (t-SVD). The average CORR of NMF, ICA, t-SVD and the proposed method is 0.2694, 0.5818, 0.6397 and 0.937, correspondingly. Therefore, the proposed method has demonstrated a more remarkable performance in terms of material identification, the analysis results of the material abundance distribution that used the proposed method.     

Time-varying linear control for tiltrotor aircraft

Tiltrotor aircraft have three flight modes: helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrange-form model, which takes into account inertial/control couplings and aerodynamic interferences. Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear (TVL) model is obtained using a Taylor-expansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.     

基于希尔伯特-黄变换的雷达数据误差修正处理技术

由于雷达跟踪测量数据总存在误差,而目前采用的误差处理算法修正效果并不理想,为了有效估计数据中的未知误差,提高数据处理的精度,提出了一种基于希尔伯特-黄算法的雷达误差残差诊断方法,利用得到的内蕴模态函数拟合出误差残差的特征,准确分离出设备的误差信息。通过对某雷达的实测数据分析证明该方法较其他方法对解决该类问题更为有效,且在事后高精度数据处理中具有较好的实用性。     

基于比例分配的过驱动碟形飞行器滑模控制

为了避免一些执行机构提前出现饱和,针对具有位置约束的过驱动碟形飞行器,按照执行机构的约束范围,提出了一种比例分配策略.基于该策略,可以使双输入系统简化成单输入系统,并避免有执行机构提前出现饱和.考虑执行机构具有一阶动态特性和系统气动参数的不确定性,设计了滑模控制律.通过比例分配和伪逆分配的比较,得出了一种确定伪逆分配权矩阵的方法.仿真结果表明了该方法的正确性和有效性.     

基于自适应观测器的飞轮故障诊断物理仿真

研究了反作用飞轮的故障诊断问题.针对反作用飞轮的非线性数学模型,分析了其故障模式,建立了其故障的参数化描述方法,并在此基础上提出了一种基于参数自适应投影的反作用飞轮故障诊断方法.该方法通过构造观测器,利用参数自适应投影算法来更新参数信息,保证观测器的误差收敛到零.最后对飞轮的正常模式和3种故障模式进行了物理仿真实验,结果表明提出的方法有效可行.     

总线容错机制及其验证方法

卫星系统广泛采用容错技术以提高系统的可靠性,而总线通信的稳定性和可靠性对于系统任务的成功至关重要．工程研制中,通常采用总线容错技术对系统通信故障进行识别和屏蔽．介绍了基于故障仿真技术的总线容错机制验证方法,包括故障规格分析技术、故障用例生成技术和故障仿真技术,利用该方法对某星载软件的总线通信功能进行了容错测试,验证了方法的有效性和实用性．     

基于正交分解法的非平稳随机振动响应计算

为高效地获得非平稳随机振动响应的高精度结果,对过滤白噪声非平稳激励信号用精确积分法获得了 K L 分解的精确向量,并对其进行了分析。单自由度和多自由度仿真结果表明, 用较少量的K\|L向量即可满足精度的要求,尤其对峰值的把握较准确。在二自由度的非线性杜芬剪切系统中利用基于能量的等价线性化方法与正交展开方法进行迭代计算并与蒙特卡洛方法进行比较,仿真结果验证了方法的精确性。     

飞行器滑模变结构姿态控制器参数优化设计

研究了大气层外飞行器姿态控制器设计。基于误差四元数建立飞行器姿态运动学与动力学方程,用滑模变结构控制方法设计控制器,通过构造Lyapunov函数验证了控制器具全局稳定性和鲁棒性。以控制器参数为优化变量,机动时间为优化指标,飞行器发动机输出力矩为约束条件,用粒子群算法实现对滑模控制器参数的优化设计。仿真结果表明：控制器设计可行且有效,并能对参数进行优化。