The radiative properties of three different materials surfaces with one-dimensional microscale random roughness were obtained with the finite difference time domain method(FDTD) and near-to-far-field transformation.Th...The radiative properties of three different materials surfaces with one-dimensional microscale random roughness were obtained with the finite difference time domain method(FDTD) and near-to-far-field transformation.The surface height conforms to the Gaussian probability density function distribution.Various computational modeling issues that affect the accuracy of the predicted properties were discussed.The results show that,for perfect electric conductor(PEC) surfaces,as the surface roughness increases,the magnitude of the spike reduces and eventually the spike disappears,and also as the ratio of root mean square roughness to the surface correlation distance increases,the retroreflection becomes evident.The predicted values of FDTD solutions are in good agreement with the ray tracing and integral equation solutions.The overall trend of bidirectional reflection distribution function(BRDF) of PEC surfaces and silicon surfaces is the same,but the silicon's is much less than the former's.The BRDF difference from two polarization modes for the gold surfaces is little for smaller wavelength,but it is much larger for the longer wavelength and the FDTD simulation results agree well with the measured data.In terms of PEC surfaces,as the incident angle increases,the reflectivity becomes more specular.展开更多
针对快速扩展随机树(rapid-exploration random tree^(*),RRT^(*))算法在三维避障路径规划中存在盲目性、低效率和路径不光滑的问题,提出一种改进的RRT^(*)算法,以提高焊接机器人路径规划的性能。通过采用双向搜索策略,缩短搜索时间;结...针对快速扩展随机树(rapid-exploration random tree^(*),RRT^(*))算法在三维避障路径规划中存在盲目性、低效率和路径不光滑的问题,提出一种改进的RRT^(*)算法,以提高焊接机器人路径规划的性能。通过采用双向搜索策略,缩短搜索时间;结合人工势场(artificial potential field,APF)算法与RRT^(*)算法以提升路径平滑性并平衡局部优化与全局最优;提出一种基于角度与密度的改进APF算法策略,提高避障与路径引导效率;提出动态目标偏置策略和动态步长策略,以增强算法在障碍物密集和稀疏区域的自适应性及搜索效率;采用路径修剪策略缩短和平滑路径。最后,通过改进的RRT^(*)算法与RRT^(*)、APF-RRT^(*)、Bi-APF-RRT^(*)(bidirectional-APFRRT^(*))3种算法对比仿真实验以及真机实验,验证了改进算法的高效性和实用性。展开更多
基金Project(2009AA05Z215) supported by the National High-Tech Research and Development Program of China
文摘The radiative properties of three different materials surfaces with one-dimensional microscale random roughness were obtained with the finite difference time domain method(FDTD) and near-to-far-field transformation.The surface height conforms to the Gaussian probability density function distribution.Various computational modeling issues that affect the accuracy of the predicted properties were discussed.The results show that,for perfect electric conductor(PEC) surfaces,as the surface roughness increases,the magnitude of the spike reduces and eventually the spike disappears,and also as the ratio of root mean square roughness to the surface correlation distance increases,the retroreflection becomes evident.The predicted values of FDTD solutions are in good agreement with the ray tracing and integral equation solutions.The overall trend of bidirectional reflection distribution function(BRDF) of PEC surfaces and silicon surfaces is the same,but the silicon's is much less than the former's.The BRDF difference from two polarization modes for the gold surfaces is little for smaller wavelength,but it is much larger for the longer wavelength and the FDTD simulation results agree well with the measured data.In terms of PEC surfaces,as the incident angle increases,the reflectivity becomes more specular.
文摘针对快速扩展随机树(rapid-exploration random tree^(*),RRT^(*))算法在三维避障路径规划中存在盲目性、低效率和路径不光滑的问题,提出一种改进的RRT^(*)算法,以提高焊接机器人路径规划的性能。通过采用双向搜索策略,缩短搜索时间;结合人工势场(artificial potential field,APF)算法与RRT^(*)算法以提升路径平滑性并平衡局部优化与全局最优;提出一种基于角度与密度的改进APF算法策略,提高避障与路径引导效率;提出动态目标偏置策略和动态步长策略,以增强算法在障碍物密集和稀疏区域的自适应性及搜索效率;采用路径修剪策略缩短和平滑路径。最后,通过改进的RRT^(*)算法与RRT^(*)、APF-RRT^(*)、Bi-APF-RRT^(*)(bidirectional-APFRRT^(*))3种算法对比仿真实验以及真机实验,验证了改进算法的高效性和实用性。
