Deferred Correction Methods for Initial Boundary Value Problems

In this paper, we consider the deferred correction principle for initial boundary value problems. The method will here be applied to the discretization in time. We obtain a method of even order p by applying the implicit midpoint rule p/2 times in each time step. For the space discretization we will use a compact implicit difference scheme. We derive error estimates for the case of time dependent coefficients and present numerical experiments confirming the theoretical analysis.     

基于Walker星座的导航卫星自主导航的GDOP最小值分析

卫星自主定轨时选择测量卫星的几何构型对于定轨精度有着重要的影响.目前地面接收机与导航卫星的几何构型对定位精度的影响主要由GDOP（几何衰减因子）来衡量,GDOP值的下限限制了在一定的测量精度下用户定位的精度范围.通过构建Walker构型的导航星座将地面接收机GDOP取最小值时的边界确定,推广应用到自主导航环境下,利用均匀采样和遗传算法分别独立得到GDOP的最小值,同时用仿真数据验证了这个值的正确性.     

Mars Rover Autonomous Navigation

Autonomous navigation of a rover on Mars surface can improve very significantly the daily traverse, particularly when driving away from the lander, into unknown areas. The autonomous navigation process developed at CNES is based on stereo cameras perception, used to build a model of the environment and generate trajectories. Multiple perception merging with propagation of the locomotion and localization errors have been implemented. The algorithms developed for Mars exploration programs, the vision hardware, the validation tools, experimental platforms and results of evaluation are presented. Portability and the evaluation of computing resources for implementation on a Mars rover are also addressed. The results show that the implementation of autonomy requires only a very small amount of energy and computing time and that the rover capabilities are fully used, allowing a much longer daily traverse than what is enabled by purely ground-planned strategies.     

基于激光传感器的智能车自主导航系统设计

从硬件电路设计和软件设计两大方面入手,分析基于激光传感器的智能车自主导航系统的设计过程。通过分析基于激光传感器芯片制作的自主导航智能车的设计原理和方案,从机械结构设计,硬件电路设计,程序算法设计以及调试经验等四个方面全面介绍智能车的制作及调试过程。经过实验对比和竞赛,表明测速模块、电机驱动模块及激光传感器的设计和选择,软件程序的编写和算法的选择有效地实现了智能车的高速自主导航。     

基于主动式传感器的道路导航

由于林荫道中阴影的影响,目前常用的基于被动式传感器技术的视觉导航方法(如采用图像的方法),难以取得比较理想的结果。对于这种环境,主动式传感器具有一定的优势,文中采用了激光雷达传感器。首先利用传感器对路边的树木等物体作为障碍物来进行检测,并据此信息来推算道路边界,详细介绍了具体的方案和算法。实验结果表明,所设计的方法具有很好的鲁棒性,可以满足实际导航的需要。     

基于SCADE的无人机自主导航飞行软件设计

该文研究了一种无人机飞行控制软件设计方法,利用高安全性的应用程序开发环境-SCADE(Safety-Critical Application Development Environment)开发无人机自主导航功能模块的软件;按照SCADE开发嵌入式软件设计流程,自动生成可直接面向工程的高安全性嵌入式代码;并通过代码的效率测试和安全性测试,验证了在SCADE环境下进行无人机软件开发的优越性;由此得出SCADE很大程度上实现了软件开发的自动化,节约了开发成本和开发时间,并具有很高的安全性特征.     

A Parallel Boundary Value Technique for Singularly Perturbed Two-Point Boundary Value Problems

A class of singularly perturbed two-point boundary-value problems (BVPs) for second-order ordinary differential equations (DEs) is considered here. In order to obtain numerical solution to these problems, an iterative non-overlapping domain decomposition method is suggested. The BVPs are independent in each subdomain and one can use parallel computers to solve these BVPs. One of the characteristics of the method is that the number of processors available is a free parameter of the method. Practical experiments on a Silicon Graphics Origin 200, with 4 MIPS R10000 processors have been performed, showing the reliability and performance of the proposed parallel schemes. Error estimates for the solution and numerical examples are provided.     

自主飞行机器人导航系统设计

自主飞行机器人系统是以微型直升机模型为载体的复杂系统。在该系统中导航系统采集各传感器数据得到机器人当前飞行姿态、空间位置以及相应的监控信息,控制模块依此监控信息按照给定策略计算并发出控制信号,实现飞行机器人的自主控制。本文对自主飞行机器人导航系统设计及功能实现做出了详细阐述。首先,给出了本自主飞行机器人的系统构造;其次,给出了导航系统的硬件组成部分以及各部分所完成的功能任务;最后阐述了导航系统的功能实现,包括飞行姿态和空间位置的获取。     

基于势场的移动机器人自主导航研究综述

人工势场法因简单实用、易于实现等优点，在机器人导航中获得广泛应用。势函数的构造也随着其它相关技术的发展不断得到完善。该文综述了势函数应用于机器人自主导航的发展历程，对其存在的问题作了分析，并对各种改进方案做了分析和比较，对影响其发展的制约性问题做了深入探讨。     

惯性基高精度组合导航方法研究与仿真

研究了一种基于捷联惯性导航系统(SINS)的高精度组合导航方法;选取SINS的系统误差作为组合导航系统状态,利用天文导航系统(CNS)输出的姿态矩阵和SINS输出信息计算得到的等效姿态矩阵来构造量测,设计SINS/CNS组合导航算法;利用SINS与北斗卫星导航系统(RDSS)各自的位置输出构造量测,设计SINS/RDSS组合导航算法,从而,利用联邦卡尔曼滤波技术设计SINS/CNS/RDSS组合导航算法;仿真结果表明,惯性基SINS/CNS/RDSS组合导航方法具有较高的导航定位精度,工程应用前景良好。     

小型无人机三维导航控制研究

为提高小型无人机自主飞行的安全性能,更好地执行特定任务,在二维平面导航的基础上提出一种三维导航控制方法;给出三维导航控制器总体结构的设计,介绍了非定高下航程推算的原理,重点阐述了自主飞行中如何在平面导航基础上引入高度控制;利用Matlab/Simulink工具箱搭建仿真模型对三维导航控制律进行仿真验证;仿真结果表明,设计的控制方法切实可行,三维导航系统稳定性良好。     

A Domain Decomposition Method Based on Natural Boundary Reduction for Nonlinear Time-Dependent Exterior Wave Problems

Received October 10, 2000; revised August 15, 2001 Published online February 18, 2002     

一种机器人的寻迹算法

针对基于光电传感器组寻迹的自动导引机器人,设计了传感器阵列的布置方式。根据此布置方式,提出了三个处理规则结合而成的轨迹识别算法。即使在导引线复杂的情况下,用此算法也能得出行进方向,控制机器人沿轨迹运动。甚至遇到干扰走错时,机器人也能自动纠错。     

一种机器人的寻迹算法

针对基于光电传感器组寻迹的自动导引机器人。设计了传感器阵列的布置方式。根据此布置方式，提出了三个处理规则结合而成的轨迹识别算法。即使在导引线复杂的情况下，用此算法也能得出行进方向，控制机器人沿轨迹运动。甚至遇到干扰走错时，机器人也能自动纠错。     

C 0 Interior Penalty Methods for Fourth Order Elliptic Boundary Value Problems on Polygonal Domains

C ⁰ interior penalty methods for fourth order elliptic boundary value problems on polygonal domains are analyzed in this paper. A post-processing procedure that can generate C ¹ approximate solutions from the C ⁰ approximate solutions is presented. New C ⁰ interior penalty methods based on the techniques involved in the post-processing procedure are introduced. These new methods are applicable to rough right-hand sides.Susanne C. Brenner: The work of S.C. Brenner was supported in part by the National Science Foundation under Grant Nos. DMS-00-74246 and DMS-03-11790. This revised version was published online in July 2005 with corrected volume and issue numbers.     

Learning View Graphs for Robot Navigation

We present a purely vision-based scheme for learning a topological representation of an open environment. The system represents selected places by local views of the surrounding scene, and finds traversable paths between them. The set of recorded views and their connections are combined into a graph model of the environment. To navigate between views connected in the graph, we employ a homing strategy inspired by findings of insect ethology. In robot experiments, we demonstrate that complex visual exploration and navigation tasks can thus be performed without using metric information.     

基于ARM9处理器的GPS车载导航系统终端

针对传统的车载导航系统终端大多采用单片机为主控处理器,存在处理速度慢,功耗高等问题,提出了采用32位ARM9的嵌入式系统进行控制,研制了新一代的GPS车载导航系统终端。给出了详细的系统硬件电路图,介绍了导航地图的实现。该系统以较少的硬件资源,实现了较高的性能,使得系统具有处理速度快、功耗低、可靠性高等特点。     

Polynomial Time-Marching for Nonreflecting Boundary Problems

The newly developed polynomial time-marching technique has been successfully extended to nonperiodic boundary condition cases. In this paper, a special non-periodic boundary condition, nonreflecting or absorbing boundary condition, is incorporated into the pseudospectral polynomial time-marching scheme. Thus, this accurate and stable time-dependent PDE solver can be applied to some open domain or free space problems. The balanced overall spectral accuracy is illustrated by some numerical experiments in the one-dimensional case. The error goes to zero at a rate faster than many fixed orders of the finite-difference scheme. The order of the absorbing boundary approximation is addressed in one-dimension. Also, in the two-dimensional case, a 2nd-order absorbing approximation has been incorporated into the polynomial time-marching scheme with Chebyshev collocation in space. Comparison with the previous finite-difference implementation indicates that the high stability and efficiency of the polynomial time-marching remains. The overall accuracy is mainly limited by the 2nd-order absorbing approximation.     

基于蓝牙技术的微型车辆导航系统

主要讨论了把一种新型的短距离无线通信技术应用于车辆导航系统的双“CPU”系统——单片机和DSP组成，介绍了整套系统的硬件组成及其各部分所完成的功能，证明该车辆导航系统具有使用价值，满足了一般用户的要求，有一定的发展空间。     

星载SINS/GPS自主组合导航系统仿真研究

重点讨论了应用于低轨道卫星的自主组合导航滤波器设计问题。考虑星上环境、精度要求和可靠性,对标准卡尔曼滤波器进行了改进。采用加权衰减记忆滤波抑制滤波发散,同时设计简易的最小二乘器实时监控卡尔曼滤渡过程是否发散,若发散则重置,进行分段滤波。通过仿真,证实了该方法的可行性,且滤波效果较理想、精度较高。