限时令牌网络实时特性的关键参数研究

针对限时令牌网络消息传输的实时性问题 ,建立了网络和消息模型 ,指出影响网络实时性能的关键参数 ,并依据线性令牌传递网络 ( L TPB)的消息调度原则推导出其关键参数的数学表达 ,最后 ,对限时令牌网络典型代表光纤分布式数据接口网络 ( FDDI)和 L TPB的实时特性进行了分析比较     

SAR线性调频脉冲干扰抑制研究

首先通过 SAR成像处理介绍线性调频脉冲干扰的原理。然后 ,分析这种干扰信号的特性及检测方法 ,并重点研究利用频域陷波和参数化方法对降斜率处理后的干扰信号进行抑制 ,即通过分数域滤波抑制线性调频脉冲干扰。最后 ,进行计算机仿真 ,给出仿真结果 ,并对仿真结果进行了分析     

Linear stability of ring systems around oblate central masses

In this paper, we consider the stability of a ring of bodies of equal mass uniformly distributed around a large oblate central mass. The purpose of this and previous papers is to shed light on the stability of Saturn’s rings. Previous papers have been limited by the assumptions that (1) all ring bodies are at the same distance from the central body, (2) the central body acts like a point mass (i.e., is a perfect sphere), and (3) the ring bodies all have the same mass and are evenly spaced around the ring. The third limitation is probably the least important; as long as there are a large number of masses and the mass distribution is approximately uniform then the system should behave as a system of equally-spaced, equal-mass bodies. The first main purpose of this paper is to remove the second limitation. But, the paper also aims to address limitation (1). Recent computer simulations of single-ring systems have shown that the threshold for stability, as determined by a linear stability analysis, matches precisely the stability threshold predicted by simulation. In other words, a linear stability analysis while presumably just a mathematical abstraction actually tells us something quite real. Furthermore, simulations of multi-ring systems suggest that instability comes from azimuthal perturbations; small azimuthal changes are more destabilizing that small radial perturbations. Hence, in this paper, we also consider the situation where the central body consists not just of an oblate central mass but also incorporates a flat ring representing in aggregate all ring bodies at radii other than the one under consideration. The central oblate body together with a flat ring is modeled simply by introducing two oblateness terms to the gravitational potential associated with the central mass. The subsequent analysis is almost identical to the case of a single oblateness term. For Saturn, the oblateness of the central mass is six orders of magnitude more significant than the rings at other radii as a destabilizing influence.     

Indirect Radau pseudospectral method for the receding horizon control problem

To solve the receding horizon control (RHC) problem in an online manner, a novel numerical method called the indirect Radau pseudospectral method (IRPM) is proposed in this paper. Based on calculus of variations and the first-order necessary optimality condition, the RHC problem for linear time-varying (LTV) system is transformed into the two-point boundary value problem (TPBVP). The Radau pseudospectral approximation is employed to discretize the TPBVP into well-posed linear algebraic equations. The resulting linear algebraic equations are solved via a matrix partitioning approach afterwards to obtain the optimal feedback control law. For the nonlinear system, the linearization method or the quasi linearization method is employed to approximate the RHC problem with successive linear approximations. Subsequently, each linear problem is solved via the similar method which is used to solve the RHC problem for LTV system. Simulation results of three examples show that the IRPM is of high accuracy and of high compu-tation efficiency to solve the RHC problem and the stability of closed-loop systems is guaranteed.     

轻型飞机燃油油量表指示器的原理设计和定量分析

燃油油量的测量，方法很多。本文首先论述了浮子电位器式传感器与电阻电桥相匹配的测量原理以及计算方法，     

适用于空间通信的LDPC码GPU高速译码架构

鉴于目前空间通信对高速、可重配置信道译码器的需求,利用图形处理器(GPU)的并行化运算特点,提出了一种低密度奇偶校验(LDPC)码软件高速译码架构。通过优化Turbo消息传递译码(TDMP)算法节点更新运算线程块内和块间并行度、减少非规则行重造成的线程分支、降低线程对节点更新信息存储资源的访问延时以及合理量化译码器存储信息来提升译码内核函数的执行效率。并在此基础上引入异步统一计算设备构架(CUDA)流处理机制,设计优化的译码器输入输出数据传输和内核函数之间的执行调度方式以及CUDA流上的译码线程资源配置方式,最大化译码吞吐率的同时降低译码延时。在Nvidia最新的Tesla K20和GTX980平台上对国际空间数据系统咨询委员会(CCSDS)遥测标准LDPC码进行的TDMP译码实验结果表明,本架构进行10次迭代译码的吞吐率最高可达约500 Mbps,平均译码延时约为2ms左右。与现有结果相比,本架构在保持软件架构配置灵活性的同时更加有效的兼顾了译码吞吐率和延时性能。     

星载子网1553B总线数据传输与管理

卫星正常运行要求星载子网的数据传输管理需具备可靠性、安全性与实时性,能够在规定的时间内完成传输任务,因此需要设计一种合理的数据传输管理方案来满足要求。考虑到1553B总线的数据传输具备速率高、可靠性好和实时性强等优点,选取1553B总线作为星载子网的数据总线,并提出了一种适用的数据传输管理方案。方案合理设计了星载子网的消息结构、消息种类、组网方式、消息传输机制、消息传输流程、消息传输时隙等。最后通过搭建测试平台对传输管理方案进行测试,测试结果表明此方案传输速率高、误码率低、实时性强,可以满足要求。     

Influence of sensor and actuator errors on impulsive satellite formation control methods

This paper investigates how sensor and actuator errors are impacting formation control accuracy and propellant consumption of a two-satellite formation in a low Earth orbit. Realistic relative navigation errors are implemented, based on the results from the PRISMA mission, as well as realistic actuator uncertainty and actuator constraints. Two impulsive control methods are investigated. The first method is based on a controller that is implemented onboard PRISMA and the second method uses linear programming to arrive at a model predictive controller. The control methods are tested in a simulation environment and are subjected to orbital perturbations and realistic sensor errors and actuator errors. Both control methods are able to maintain the desired relative geometry of a projected circular orbit in the presence of the errors. The PRISMA control method demonstrates lower propellant consumption, while the model predictive controller shows better control accuracy. The results show that, based on the used scenario, sensor errors dominate both the formation control accuracy and propellant consumption. The versatility of the model predictive controller is demonstrated in a challenging formation control scenario including formation maintenance and formation reconfiguration tasks.     

基于VPX总线的智能供配电系统设计

介绍了VPX标准及技术特点,提出了基于VPX总线架构的供配电系统组成和功能,并对各板卡的供电、控制、指令等进行分析,形成技术方案。实现了各功能板卡间的优化配置,开展了相关的试验验证。试验结果表明,该系统稳定可靠,具有广泛的应用前景。     

卫星姿态控制系统故障重构观测器设计

对于卫星姿态控制系统,提出一种基于PD型学习观测器(Learning observer, LO)的系统故障重构方法。在P型LO的学习算法基础上引入测量输出估计误差的微分项,设计了一种PD型LO,估计卫星姿态角速度和姿态角的同时,快速精确重构卫星执行机构故障。给出了所提观测器的稳定性条件,并基于线性矩阵不等式技术提出一种系统化PD型LO设计方法。进一步,将所提PD型LO设计扩展用于卫星姿态敏感器故障的快速重构。最后,将所提方法应用于微小卫星推力器故障重构和陀螺故障重构,仿真结果校验了所提方法的有效性。