精细指数积分法在卫星编队飞行动力学中的应用

编队飞行卫星间的距离远小于卫星的轨道半径, 其动力学方程表现为弱非线性。针对弱非线性方程的求解, 提出精细指数积分方法, 用精细积分法求解指数积分方法中的指数矩阵。用精细指数积分法和Runge-Kutta方法, 在不同条件下求解弱非线性方程的算例, 验证了精细指数积分法的有效性。通过Lagrange方程, 建立卫星编队飞行动力学方程的半线性形式, 用精细指数积分方法与Runge-Kutta方法求解方程。数值计算结果表明, 与同阶的Runge-Kutta求解弱非线性微分方程相比, 精细指数积分法具有更高的精度, 为卫星编队飞行动力学仿真提供了一种有效的数值算法。     

2维Gross-Pitaevskii方程的辛格式

提出了2维Gross-Pitaevskii方程的辛格式,该格式能够精确地保持电荷守恒和隐式能量守恒,还分析了该格式的数值误差,最后通过数值例子验证了理论结果.     

Dynamics of Charged Particles Around a Magnetized Black Hole with Pseudo-Newtonian Potential

The linear stability of equilibria of charged particles moving near a compact object with a dipole magnetic field and a pseudo-Newtonian potential is analyzed detailedly. An optimal fourth-order force gradient symplectic method, as a global symplectic integrator that can simultaneously solve both the equations of motion and the variational equations, is used to calculate fast Lyapunov indicators. In this way, dynamical structures are described, and parameter domains for causing chaos are found.     

Self-Trapping in Discrete Nonlinear Schrdinger Equation with Next-Nearest Neighbor Interaction

The dynamical self-trapping of an excitation propagating on one-dimensional of different sizes with nextnearest neighbor (NNN) interaction is studied by means of an explicit fourth order symplectic integrator. Using localized initial conditions, the time-averaged occupation probability of the initial site is investigated which is a function of the degree of nonlinearity and the linear coupling strengths. The self-trapping transition occurs at larger values of the nonlinearity parameter as the NNN coupling strength of the lattice increases for fixed size. Furthermore, given NNN coupling strength, the self-trapping properties for different sizes are considered which are some different from the case with general nearest neighbor (NN) interaction.     

General techniques for constructing variational integrators

The numerical analysis of variational integrators relies on variational error analysis, which relates the order of accuracy of a variational integrator with the order of approximation of the exact discrete Lagrangian by a computable discrete Lagrangian. The exact discrete Lagrangian can either be characterized variationally, or in terms of Jacobi’s solution of the Hamilton-Jacobi equation. These two characterizations lead to the Galerkin and shooting constructions for discrete Lagrangians, which depend on a choice of a numerical quadrature formula, together with either a finite-dimensional function space or a one-step method. We prove that the properties of the quadrature formula, finite-dimensional function space, and underlying one-step method determine the order of accuracy and momentum-conservation properties of the associated variational integrators. We also illustrate these systematic methods for constructing variational integrators with numerical examples.     

电子式互感器高频数据采集与传输方案

针对当前电力系统电子式互感器采样率偏低,难以满足行波测距装置准确定位电力故障的问题,提出了电子式互感器高频信号采集与传输方案;电子式互感器内部为Rogowski 线圈,电网电流信号被其微分作用转换为小电压信号并附加了90°超前相差,设计积分电路补偿该相差;设计采样率为2 MSps的高频信号采集电路,FPGA通过LVDS接口读取采样数据,并进行幅值处理,最后利用大容量FIFO(先入先出单元)进行缓存;由于百兆网数据传输速率有限,利用FPGA设计吉比特光纤以太网传输特定格式报文,把电流数据传输至电力行波测距装置;解决了积分电路由于运放输入偏置电压带来的积分饱和问题,以及高速ADC输入量程小于输入信号幅值等技术难点;试验结果表明,高频信号采集及传输方案能够满足行波测距装置百米级别的测距精度要求,具有一定工程应用价值。     

积分器零漂的自动补偿

针对积分器存在的零点漂移现象,通过静态调零和动态补偿的方法减小零漂的影响,并给出了自动补偿零漂的实际电路,该电路能在很大程度上消除积分的零点漂移,使其在微弱信号的测量等场合发挥作用。     

太阳模拟器用光学积分器设计

针对传统太阳模拟器普遍存在辐照均匀度较低的缺陷,改进设计了一种可以有效提高太阳模拟器辐照均匀度的光学积分器.介绍了该光学积分器的组成和工作原理;阐述了光学系统的优化设计技术;对其光机结构进行合理化设计,并使用ansys软件对光机结构进行热分析.最后,利用lightTools软件对太阳模拟器系统进行模拟仿真.结果表明:使用所设计的光学积分器后,太阳模拟器辐照不均匀度明显降低,在Φ60 mm范围内小于±1%,在Φ(60~200)mm范围内小于±2%.该结果与实际检测结果一致,能够满足高准确度的使用要求.     

双斜率积分ADC中开关电容积分器的设计

为提高双斜率积分ADC中模拟输入信号转换成数字信号的准确性,设计了一种高性能开关电容积分器以替代传统的RC有源积分器。该开关电容积分器的运算放大器由折叠共源共栅输入级和Class AB输出级组成,开关部分选用CMOS开关,以抑制电荷注入和时钟馈通的影响。在中芯国际0.18μmCMOS工艺下,采用EDA仿真软件对相关模块进行仿真验证,得到运算放大器的直流增益为110.3 dB,单位增益带宽为5.64 MHz,相位裕度达到79°,输出摆幅为0.013 3～3 299 mV,转换速率为7.56 MV/s。结果表明,开关电容积分器完全满足双斜率积分ADC的实际应用。     

8PSK中频数字化发射机中多级滤波器的研究与设计

本文介绍了8PSK调制方式的原理和相应中频数字化发射机的系统结构,并进一步提出了发射机中多级滤波器各自的作用及实现方法。针对数字化基带成形的处理特点,该文提出一种基于分布式算法和查找表的高速成形滤波器实现方法以基于现场可编程门阵列（FPGA）芯片实现根升余弦FIR,滤波器,以及由CIC内插滤波器实现了发射机中的增采样功能。整个设计采用硬件描述语言VerilogHDL实现,通过仿真验证了以这些方法来实现相应的功能是可行的。