Minimum sliding mode error feedback control for fault tolerant small satellite attitude control

This paper proposes a new control strategy (which we call “minimum sliding mode error feedback control, MSMEFC”) for small satellite attitude control. As we know, the attitude control algorithm plays a significant role in the whole performance of the satellite, especially under the existence of uncertain disturbances from the space. Without loss of generality, the MSMEFC is presented based on the sliding mode theory. It is assumed that the equivalent control error is defined to offset the uncertain disturbances to improve the control performance. Hence, in order to estimate the optimal equivalent control error, a cost function is derived on the basis of the principle of minimum sliding mode error. Then, the equivalent control error wills feedback to the conventional sliding mode control to obtain the final MSMEFC. According to the theoretical analyzes, the sliding mode after the MSMEFC will approximate to the ideal sliding mode, resulting in enhancing the control performance. Moreover, an adaptive non-singular terminal sliding mode is employed to compare with the performance of MSMEFC. Several simulations are performed to verify the effectiveness of proposed MSMEFC in the presence of serious perturbations, even in some fault-tolerant scenarios.     

Introduction to global short message communication service of BeiDou-3 navigation satellite system

Short Message Communication (SMC) is a featured service of BeiDou Navigation Satellite System (BDS). After its successful deployment in 2003, Regional Short Message Communication (RSMC) service has been continuously serving China and its neighboring countries and regions, especially in life safety scenarios. In this paper, the architecture of the Global Short Message Communication (GSMC) system is proposed based on the medium earth orbit (MEO) constellation and the crosslinks of the global BeiDou navigation system (BDS-3). Three subtypes of GSMC service, i.e. positioning report, emergency search and rescue (SAR) and regular SMC are designed in accordance with the technical characteristic of integration of navigation and communication in BDS-3, which supports future wide applications of GSMC. The performance of the designed GSMC system is analyzed by numerical calculations. As BDS-3 was officially announced completion on July 31, 2020, GSMC has been providing initial service. First test results of the in orbit GSMC payloads are also presented in the paper to verify the designed capabilities. Preliminary results also show that the requirements of Global Maritime Distress and Safety System (GMDSS) can also be fulfilled.     

某型飞机自动驾驶信号仿真系统设计与实现

自动驾驶信号仿真系统能够模拟某型教练机进行自动驾驶操作时所需要的动态信号。解决飞机地面试验时无真实动态的飞机攻角、高度、马赫数等大气机数据以及飞机姿态角、升降速度等惯导数据信息的问题。本文主要介绍某型教练机自动驾驶信号仿真系统的设计与实现方法。     

不同直径光滑圆管中黄原胶溶液流动减阻特性的实验研究

采用实验的方法,测试了黄原胶溶液在不同直径的光滑管道流动中的减阻特性和管径效应。其中变化参数为：（1）管道直径,共有3种管径,分别为5、10和20mm;（2）黄原胶溶液的浓度,变化范围为50~550ppm;（3）流速,用广义雷诺数（ReM）来表征,变化范围为0~50000。实验测量了不同参数下的管道压降Δp和体积流量Q,得到了黄原胶溶液浓度与减阻率的关系,以及ReM数对沿程阻力系数λ的影响,观测到黄原胶溶液减阻具有很明显的浓度效应,即随着溶液浓度的升高减阻率不断增大,直至达到最佳饱和减阻浓度,减阻率基本保持恒定。还观测到黄原胶溶液在不同管径中高低流速下表现出减阻类型的差异。     

评估法兰结构螺栓松动的改进损伤指标研究

基于压电阻抗法的采用统计学参数作为损伤指标评估螺栓松动的方法有着广泛的应用，然而采用该方法的试验对象多数为实验室条件下的板等结构，并非真实结构。因此，针对真实的法兰结构，这些损伤指标是否适用、是否需要改进仍需进一步研究。通过实验，得出不同损伤指标与法兰结构螺栓松动之间的规律:螺栓松动的程度越大位置越近，均方根偏差（RMSD）、平均绝对百分比偏差（MAPD）、相关系数差（CCD）的值越大，而指标R_y/R_x因无显著规律不适合作为评估法兰结构螺栓松动的损伤指标。通过对比结果发现:结构差异对前3个损伤指标均有不同程度的影响，改进后的损伤指标均方根变化率（RMSCR）只与法兰结构螺栓松动的位置和程度有关，受结构差异影响小。因此，RMSCR具有重要实践意义:当任一压电片损坏时只需更换为同型号的压电片即可，无需更新损伤指标库。通过实验验证了上述结果的正确性与基于RMSCR的法兰结构螺栓松动检测方法的适用性。      

Internet2—未来的Internet

介绍了Internet2的发展、基本结构和网络互连等问题，描述了与Internet2紧密相关的gigaPoP的组成，说明了必须考虑的参数和约束条件，阐明了所要采用的路由和服务质量协议。     

基于Windows消息机制的MSC.Patran集成方法研究

为了解决航天器虚拟振动试验过程中的数据管理问题,提出了一种基于Windows消息机制的MSC.Patran软件集成方法,并设计了总体集成框架,针对其中的关键技术,如集成环境初始化、窗口动态控制等内容进行了详细论述。应用该方法和框架研制航天器虚拟振动试验系统,验证了其可行性。结果表明,该集成方法能够有效解决Patran与数据管理系统的数据集成共享问题。     

核心机派生间冷回热航空发动机热循环参数匹配研究

间冷回热航空发动机作为一种新概念动力技术,可满足未来民用航空发动机对成本控制、环境友好性等方面的要求.以成熟的核心机为基础,在常规热力循环基础上增加间冷过程和回热过程,匹配低压系统派生间冷回热涡扇发动机,进行热力循环参数选择与性能仿真分析.结果表明,派生的间冷回热航空发动机性能提升明显,与常规循环发动机相比,净推力增加...     

区域管制中Y2K问题的风险管理

Y2K将有可能造成管制区域中通信、导航、监视设备的全部或部分失效，为了保证飞行安全，必须进行风险管理。通过对假想空域中Y2K问题带来风险的分析，提出了几点控制风险的措施