针对滩涂履带车在受潮汐影响的滩涂环境中进行长时间勘测作业的需求,提出柯西贝塞尔快速搜索随机树星(Cauchy Bessel Rapidly-exploring Random Tree Star,CB-RRT^(*))算法进行路径规划。为规划出安全路径,基于全局地图和潮汐数据,并通...针对滩涂履带车在受潮汐影响的滩涂环境中进行长时间勘测作业的需求,提出柯西贝塞尔快速搜索随机树星(Cauchy Bessel Rapidly-exploring Random Tree Star,CB-RRT^(*))算法进行路径规划。为规划出安全路径,基于全局地图和潮汐数据,并通过滩涂履带车到分界区的距离构建出滩涂预测模型;为提高滩涂履带车移动到目标点需进行多次路径规划的速度,对初始路径的关键树节点使用柯西概率密度函数进行采样缩小采样范围来提高节点的利用率,进而提高算法的收敛性;在重选父节点过程中考虑最大转角约束设定相应系数,并使用连续二次贝塞尔曲线进行拼接的方式来生成路径,达到提高路径平滑度的目的和解决平滑后路径与原路径偏差过大造成的安全性问题。仿真实验结果表明,CB-RRT^(*)算法在静态滩涂环境和动态滩涂环境中,能大大提高算法的收敛性和路径的平滑性,且保证路径长度最优,研究内容可以保证滩涂履带车在各种滩涂环境中进行长时间安全作业。展开更多
近年来无人机遥感发展迅速,其高机动性、高分辨率和低成本等特点,已经被证明为低空遥感探测的重要手段。通过配准序列图像,最优化迭代得到内外方位元素,基于核线约束,利用改进的密集匹配方法,直接生成整个区域的数字地表模型。在密集匹...近年来无人机遥感发展迅速,其高机动性、高分辨率和低成本等特点,已经被证明为低空遥感探测的重要手段。通过配准序列图像,最优化迭代得到内外方位元素,基于核线约束,利用改进的密集匹配方法,直接生成整个区域的数字地表模型。在密集匹配中,添加所有图像的FAST(Features from Accelerated Segment Test)角点,扩展投影点集,用于构建初始点云的格网平面。基于影像相关和核线约束,在相关的子区域内搜索最优投影点,然后通过最小二乘迭代各投影点,定位最优地面点。通过高斯函数的加权平均方法,引入各投影点的辐射比例因子,生成归一化的图像像素值,获得彩色点云。实验表明,该方法生成的真实彩色三维模型,有效地表现出建筑、道路和树木等基础地物类型。展开更多
This paper proposes and applies a method to sort two-dimensional control points of triangular Bezier surfaces in a row vector. Using the property of bivariate Jacobi basis functions, it further presents two algorithms...This paper proposes and applies a method to sort two-dimensional control points of triangular Bezier surfaces in a row vector. Using the property of bivariate Jacobi basis functions, it further presents two algorithms for multi-degree reduction of triangular Bezier surfaces with constraints, providing explicit degree-reduced surfaces. The first algorithm can obtain the explicit representation of the optimal degree-reduced surfaces and the approximating error in both boundary curve constraints and corner constraints. But it has to solve the inversion of a matrix whose degree is related with the original surface. The second algorithm entails no matrix inversion to bring about computational instability, gives stable degree-reduced surfaces quickly, and presents the error bound. In the end, the paper proves the efficiency of the two algorithms through examples and error analysis.展开更多
文摘针对滩涂履带车在受潮汐影响的滩涂环境中进行长时间勘测作业的需求,提出柯西贝塞尔快速搜索随机树星(Cauchy Bessel Rapidly-exploring Random Tree Star,CB-RRT^(*))算法进行路径规划。为规划出安全路径,基于全局地图和潮汐数据,并通过滩涂履带车到分界区的距离构建出滩涂预测模型;为提高滩涂履带车移动到目标点需进行多次路径规划的速度,对初始路径的关键树节点使用柯西概率密度函数进行采样缩小采样范围来提高节点的利用率,进而提高算法的收敛性;在重选父节点过程中考虑最大转角约束设定相应系数,并使用连续二次贝塞尔曲线进行拼接的方式来生成路径,达到提高路径平滑度的目的和解决平滑后路径与原路径偏差过大造成的安全性问题。仿真实验结果表明,CB-RRT^(*)算法在静态滩涂环境和动态滩涂环境中,能大大提高算法的收敛性和路径的平滑性,且保证路径长度最优,研究内容可以保证滩涂履带车在各种滩涂环境中进行长时间安全作业。
文摘近年来无人机遥感发展迅速,其高机动性、高分辨率和低成本等特点,已经被证明为低空遥感探测的重要手段。通过配准序列图像,最优化迭代得到内外方位元素,基于核线约束,利用改进的密集匹配方法,直接生成整个区域的数字地表模型。在密集匹配中,添加所有图像的FAST(Features from Accelerated Segment Test)角点,扩展投影点集,用于构建初始点云的格网平面。基于影像相关和核线约束,在相关的子区域内搜索最优投影点,然后通过最小二乘迭代各投影点,定位最优地面点。通过高斯函数的加权平均方法,引入各投影点的辐射比例因子,生成归一化的图像像素值,获得彩色点云。实验表明,该方法生成的真实彩色三维模型,有效地表现出建筑、道路和树木等基础地物类型。
基金Supported by the National Natural Science Foundation of China (6087311160933007)
文摘This paper proposes and applies a method to sort two-dimensional control points of triangular Bezier surfaces in a row vector. Using the property of bivariate Jacobi basis functions, it further presents two algorithms for multi-degree reduction of triangular Bezier surfaces with constraints, providing explicit degree-reduced surfaces. The first algorithm can obtain the explicit representation of the optimal degree-reduced surfaces and the approximating error in both boundary curve constraints and corner constraints. But it has to solve the inversion of a matrix whose degree is related with the original surface. The second algorithm entails no matrix inversion to bring about computational instability, gives stable degree-reduced surfaces quickly, and presents the error bound. In the end, the paper proves the efficiency of the two algorithms through examples and error analysis.
