Fully distributed time-varying formation tracking control for multiple quadrotor vehicles via finite-time convergent extended state observer

This paper investigates a time-varying anti-disturbance formation problem for a group of quadrotor aircrafts with time-varying uncertainties and a directed interaction topology. A novel Finite-Time Convergent Extended State Observer (FTCESO) based fully-distributed formation control scheme is proposed to enhance the disturbance rejection and the formation tracking performances for networked quadrotors. By adopting the hierarchical control strategy, the multi-quadrotor system is separated into two subsystems: the outer-loop cooperative subsystem and the inner-loop attitude subsystem. In the outer-loop subsystem, with the estimation of disturbing forces and uncertain dynamics from FTCESOs, an adaptive consensus theory based cooperative controller is exploited to ensure the multiple quadrotors form and maintain a time-varying pattern relying only on the positions of the neighboring aircrafts. In the inner-loop subsystem, the desired attitude generated by the cooperative control law is stably tracked under a FTCESO-based attitude controller in a finite time. Based on a detailed algorithm to specify the cooperative control protocol, the feasibility condition to achieve the time-varying anti-disturbance formation tracking is derived and the rigorous analysis of the whole closed-loop multi-quadrotor system is given. Some numerical examples are conducted to intuitively demonstrate the effectiveness and the improvements of the proposed control framework.     

基于多相正交序列移位序列的CDMA通信系统

介绍多相正交序列的构造方法,对多相正交序列的自相关和互相关特性进行分析。提出采用多相正交序 列的移位序列作为扩频序列的通信方式,并给出接收端序列同步的实现方法。这种方式能解决低相数多相正交序列互 相关特性不理想,而高相数多相正交序列难以搜索的困难。     

实验教学遥测系统中的一种码型反变换方法

在遥测系统中有许多种数字信号码型可以使用。在遥测解调分系统中 ,通常采用 NRZL 码作为输出码型 ,这就需要将系统输入的其它码型反变换为 NRZL 码。文中介绍一种在实验教学遥测系统中采用的利用匹配滤波、门限判决、采样、移位、异或的手段来实现码型反变换的方法。     

CPL蒸发器传热和蒸发流动过程的分布参数模型

针对ＣＰＬ蒸发器，建立了可据以分析其传热过程和蒸发流动过程的分布参数模型，并就一个模拟算例进行了考察，得出了有意义的结论。该模型较之传统集中参数模型的优点在于，其计算结果反映出了蒸发器内沿轴向流动过程中各肋壁温度及肋壁与流动工质之间换热系数大小的变化情况以及蒸发器内局部蒸汽（或液体）的热力状况，因而为从细节上揭示ＣＰＬ蒸发器的传热性能及其工程模型的试验研究、优化设计等打下了一定的基础     

NIM4#铯冷原子喷泉钟新一代时间频率基准

回顾了NIM4 #钟实现 5 μK冷原子云 ,74cm原子喷泉和 0 95Hz线宽Ramsey跃迁实验 ,报道了 9 19GHz微波锁定到铯原子秒定义跃迁 ,频率稳定性达到 (5 - 7)× 10 -15(15 0 0 0s)。目前我们正在进行不确定度评估 ,可望不确定度进入 10 -15量级 ,建立我国新一代时间频率基准装置。     

利用非交错对称矩阵构造Cartesian认证码

利用特征为2的有限域上非交错对称矩阵构造了一个Cartesian认证码，并计算出其参数。进而，假定编码规则按照均匀的概率分布所选取，计算出了该码被模仿攻击成功的最大概率只和被替换攻击成功的最大概率Ps。     

一类特殊的改进捕错译码

捕错译码是传码率满足Ｒ＜１／ｔ的循环码译码最简单的方式，其中ｔ是所能纠错误数的最大值，Ｒ是传码率。这类码传码率低，纠错少。嵩钟雄运用覆盖多项式的概念得出了传码率不满足Ｒ＜１／ｔ的二进制循环码的改进捕措译码方法。本文找到了嵩钟雄译码器的一个子类－－一类特殊的改进捕错译码器。作者的译码器同捕错译码器一样易于硬件实现，并且能够用于传码率不满足Ｒ＜１／ｔ的情况。对于纠错码，作者找到了适合于这一译码器的码判     

在边缘弯矩和局部线性荷载共同作用下圆板的塑性极限分析

本文应用广义阶梯函数对承受边缘弯矩和局部线性分布荷载的筒支圆板进行塑性极限分析，文中考虑了局部线性分布荷载的４种可能分布形式，给出了简支圆板在Ｔｒｅｓｃａ屈服条件下边缘弯矩和线性荷载所满足的关系式。     

Online scheduling of distributed Earth observation satellite system under rigid communication constraints

This paper focused on online scheduling of distributed Earth observation satellite system in a dynamic environment. The objective was to maximize the total profit of the overall system by efficiently coordinating the different satellites with stochastic arrival of urgent tasks, subject to rigid communication and observation time window constraints. We formulated this problem as a single-task, single-robot, time-extended assignment problem with intra-schedule dependency using the multi-robot task assignment taxonomy and formulated the sub-problem after releasing urgent tasks in a mixed-integer linear programming model. We first described the online scheduling algorithm for a single satellite, then we proposed the modified consensus-based bundle algorithm (m-CBBA) and modified asynchronous consensus-based bundle algorithm (m-ACBBA) with synchronous and asynchronous communication, respectively. Compared with initial versions of CBBA and ACBBA, the modified versions added the communication loop prediction phases to efficiently utilize scarce communication opportunities and reduce the communication requirements. Additionally, we introduce two contract net protocol (CNP)-based algorithms for comparison, respectively SingleItem-CNP-based (SI-CNP) algorithm and Batch-CNP-based (BA-CNP) algorithm. Computational experiments indicated that both the total profit and percentage of scheduled urgent tasks achieved by the m-ACBBA and m-CBBA algorithms were much higher than those achieved by both SI-CNP and BA-CNP. Additionally, the number of communications needed by either m-ACBBA or m-CBBA algorithm was lower than that by SI-CNP. When the communication cost in the system is high, the m-CBBA algorithm is preferred because it balances the profit and the required number of communications. When the communication cost is low, the m-ACBBA algorithm is preferred because it achieves high total profit and high percentage of scheduled urgent tasks.