北斗导航卫星氢原子钟性能分析评估

星载原子钟是导航卫星最重要的载荷之一,负责星上时间基准的产生和维持.我国北斗三号导航试验卫星首次配置了23 kg级被动型星载氢原子钟,验证了氢原子钟的空间环境适应性和在轨性能,实现在轨运行误差小于1 ns/d.在北斗三号全球导航卫星系统中,氢原子钟已作为主钟应用至GEO,IGSO和MEO三类导航卫星,对系统的运行发挥至关重要的作用.本文从氢原子钟的机理和性能评估方法出发,比较了铷钟、铯钟和氢钟三类原子钟的性能差异,根据地面和在轨测试数据,给出氢原子钟在轨运行性能评估结果;最后利用卫星遥测数据建模,对氢原子钟健康状况和寿命进行了初步分析.     

On-orbit target tracking and inspection by satellite formation

A new type of estimator is developed for the satellite formation to track and inspect on-orbit targets. The follower satellite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and controllability are analyzed to qualitatively evaluate the convergence performance. Finally, an on-orbit target inspection scenario is numerically simulated to verify the performance of the estimator based on pseudo measurement.     

基于集群空间机器人的合作目标协同定位技术

根据集群空间机器人群内各成员功能的差异,设计了合作目标的协同定位方法. 首先,采用状态方程建立了集群动力学模型,并基于线性Kalman滤波理论,设计了集中式协同定位滤波算法,为降低集中式协同定位滤波算法的计算量,进一步设计了分布式协同定位滤波算法. 研究结果表明,本文分析了所提出的协同定位滤波算法的性能,并通过数学仿真进行了验证其稳定性和精度.      

Advanced Credit-Assignment CMAC Algorithm for Robust Self-Learning and Self-Maintenance Machine

Smart machine necessitates self-learning capabilities to assess its own performance and predict its behavior. To achieve self-maintenance intelligence, robust and fast learning algorithms need to be embedded in machine for real-time decision. This paper presents a credit-assignment cerebellar model articulation controller (CA-CMAC) algorithm to reduce learning interference in machine learning. The developed algorithms on credit matrix and the credit correlation matrix are presented. The error of the training sample distributed to the activated memory cell is proportional to the cell‘s credibility, which is determined by its activated times. The convergence processes of CA-CMAC in cyclic learning are further analyzed with two convergence theorems. In addition, simulation results on the inverse kinematics of 2degree-of-freedom planar robot arm are used to prove the convergence theorems and show that CA-CMAC converges faster than conventional machine learning.     

CVC热连轧机支持辊不均匀磨损及辊形改进

非对称的CVC工作辊与对称支持辊辊形配置易导致下游机架支持辊辊形自保持性差.利用ANSYS有限元软件分析F4机架常规支持辊磨损对轧机板形调控性能及辊间接触压力分布的影响,发现严重的支持辊不均匀磨损会影响轧机的板形控制稳定性,并导致支持辊剥落增加辊耗.基于有限元分析提出一种新的支持辊辊形,实验证明新辊形具有良好的自保持性,可在整个服役期内稳定发挥其性能,并在支持辊服役后期缓解辊间接触压力尖峰的出现.     

Dynamics and nonlinear control of space electromagnetic docking

Space electromagnetic docking technology,free of propellant and plume contamination,offers continuous,reversible and synchronous controllability,which is widely applied in the future routine on-orbit servicing missions.Due to the inherent nonlinearities,couplings and uncertainties of an electromagnetic force model,the dynamics and control problems of them are difficult.A new modeling approach for relative motion dynamics with intersatellite force is proposed.To resolve these control problems better,a novel nonlinear control method for soft space electromagnetic docking is proposed,which combines merits of artificial potential function method,Lyapunov theory and extended state observer.In addition,the angular momentum management problem of space electromagnetic docking and approaches of handling it by exploiting the Earth’s magnetic torque are investigated.Finally,nonlinear simulation results demonstrate the feasibility of the dynamic model and the novel nonlinear control method.     

一种状态自维护机制的建模与分析

提出了一种用户广域网环境下的客户服务器系统的资源使用状态自维护机制，使客户在保存自身对资源的使用状况和有关状态的同时定时地将其通知服务器，从而达到应用系统的健壮性和状态参数的一致性。在此基础上，利用Perti网对具备该机制的客户服务器系统进行了建模，对正常和各种异常情况下系统的自维护特性进行了分析，最后介绍了该机制在一个实际的客户服务器系统中的应用情况。     

服务航天器超近程逼近目标的相对姿轨耦合控制

针对服务航天器超近程逼近目标的相对姿态轨道耦合控制问题,推导了耦合动力学模型并设计了相应控制律。通过引入描述相对运动构型变化的期望相对位置矢量和位置误差矢量,将相对轨道跟踪控制问题转化为调节器的设计问题。推导了考虑对接机构安装位置的相对姿态轨道耦合动力学模型。利用李雅普诺夫稳定性理论,设计了考虑未知有界干扰的相对姿态轨道耦合控制律。考虑控制输入受限进行数学仿真,结果表明所设计的控制律是有效的,并具有较好的性能。     

一种利用星敏感器对陀螺进行在轨标定的算法

为确保姿态测量器件长期在轨工作精度、提高姿态确定精度,针对典型的陀螺和星敏感器联合定姿方案,推导了一种星敏感器/陀螺在轨标定算法。考虑到卫星姿态测量过程中的几种主要误差源,建立星敏感器和陀螺标定模型,首先用递推算法对星敏感器单独在轨标定,然后采用Kalman滤波对星敏感器和陀螺同时进行在轨标定,对误差进行实时补偿,有效地提高了星敏感器和陀螺的测量精度,与同类算法相比,为卫星姿态确定提供了更加丰富的信息。最后对该算法进行了数学仿真,仿真结果验证了算法的有效性。     

论高校图书馆员心理健康的维护

分析了高校图书馆员的心理健康现状及某些心理问题产生的原因,说明了图书馆馆员进行心理健康维护的重要性,提出了一系列加强馆员心理健康维护的方法和策略。