The shadow of a circle casting on a unparallel plane is an ellipse, the shadow algorithm involves a perspective affine transformation. Under commonly used light, the transformation matrix for parallel circles of diffe...The shadow of a circle casting on a unparallel plane is an ellipse, the shadow algorithm involves a perspective affine transformation. Under commonly used light, the transformation matrix for parallel circles of different diameters casting shadows onto the same plane is identical. Using AutoCAD to get the shadow of a general object of revolution, it only needs to take a series of circles along the axis of symmetry and get their corresponding shadows of ellipses, drawing an envelope to cover all these silhouettes results in the required overall shadow. Then the discrete points of shadow contour line are projected back onto the original object surface, shadow on the object is obtained altogether.展开更多
An efficient approach was proposed for discriminating shadows from moving objects. In the background subtraction stage, moving objects were extracted. Then, the initial classification for moving shadow pixels and fore...An efficient approach was proposed for discriminating shadows from moving objects. In the background subtraction stage, moving objects were extracted. Then, the initial classification for moving shadow pixels and foreground object pixels was performed by using color invariant features. In the shadow model learning stage, instead of a single Gaussian distribution, it was assumed that the density function computed on the values of chromaticity difference or bright difference, can be modeled as a mixture of Gaussian consisting of two density functions. Meanwhile, the Gaussian parameter estimation was performed by using EM algorithm. The estimates were used to obtain shadow mask according to two constraints. Finally, experiments were carried out. The visual experiment results confirm the effectiveness of proposed method. Quantitative results in terms of the shadow detection rate and the shadow discrimination rate(the maximum values are 85.79% and 97.56%, respectively) show that the proposed approach achieves a satisfying result with post-processing step.展开更多
针对在局部阴影条件下,光伏阵列的功率-电压特性曲线呈现多个峰值,传统群体智能优化存在收敛速度慢、振荡幅度大和易陷入局部最优等问题,提出一种基于PSO-GWO(Particle Swarm Optimization-Grey Wolf Optimization)算法的MPPT(Maximum P...针对在局部阴影条件下,光伏阵列的功率-电压特性曲线呈现多个峰值,传统群体智能优化存在收敛速度慢、振荡幅度大和易陷入局部最优等问题,提出一种基于PSO-GWO(Particle Swarm Optimization-Grey Wolf Optimization)算法的MPPT(Maximum Power Point Tracking)控制方法。该算法引入余弦规律变化的收敛因子,平衡GWO算法的全局搜索与局部搜索能力;引入PSO算法,提高灰狼个体与自身经验之间的信息交流。仿真结果表明,提出的PSO-GWO算法在局部阴影条件下不仅能快速收敛,而且功率输出震荡幅度更小,有效提升了局部遮阴条件下光伏阵列的最大功率跟踪效率和精度。展开更多
局部阴影情况下,光伏阵列输出功率具有多峰值特性,针对最大功率点跟踪(Maximum power point tracking,MPPT)算法在实际应用中存在着收敛速度较慢,效率较低,且容易陷入局部功率极值的问题,将兼顾收敛速度、精度、功率稳定性的快速布谷鸟...局部阴影情况下,光伏阵列输出功率具有多峰值特性,针对最大功率点跟踪(Maximum power point tracking,MPPT)算法在实际应用中存在着收敛速度较慢,效率较低,且容易陷入局部功率极值的问题,将兼顾收敛速度、精度、功率稳定性的快速布谷鸟搜索(Fast cuckoo search,FCS)算法应用于光伏阵列最大功率追踪。FCS算法采用自适应步长和机会因子可避免过早收敛,全局搜索和跳出局部搜索能力强,收敛速度快,算法后期局部开发能力强,功率振荡小,功率输出稳定,最大功率追踪精度高。仿真表明,在静态阴影、动态阴影条件下,FCS算法较灰狼算法(Grey wolf optimizer,GWO)、粒子群算法(Particle swarm optimization,PSO)具有更快地收敛速度和更高的收敛精度,且稳定性好,有效地提升光伏阵列的输出效率。展开更多
文摘The shadow of a circle casting on a unparallel plane is an ellipse, the shadow algorithm involves a perspective affine transformation. Under commonly used light, the transformation matrix for parallel circles of different diameters casting shadows onto the same plane is identical. Using AutoCAD to get the shadow of a general object of revolution, it only needs to take a series of circles along the axis of symmetry and get their corresponding shadows of ellipses, drawing an envelope to cover all these silhouettes results in the required overall shadow. Then the discrete points of shadow contour line are projected back onto the original object surface, shadow on the object is obtained altogether.
基金Project(50805023)supported by the National Natural Science Foundation of ChinaProject(BA2010093)supported by the Special Fund of Jiangsu Province for the Transformation of Scientific and Technological Achievements,ChinaProject(2008144)supported by the Hexa-type Elites Peak Program of Jiangsu Province,China
文摘An efficient approach was proposed for discriminating shadows from moving objects. In the background subtraction stage, moving objects were extracted. Then, the initial classification for moving shadow pixels and foreground object pixels was performed by using color invariant features. In the shadow model learning stage, instead of a single Gaussian distribution, it was assumed that the density function computed on the values of chromaticity difference or bright difference, can be modeled as a mixture of Gaussian consisting of two density functions. Meanwhile, the Gaussian parameter estimation was performed by using EM algorithm. The estimates were used to obtain shadow mask according to two constraints. Finally, experiments were carried out. The visual experiment results confirm the effectiveness of proposed method. Quantitative results in terms of the shadow detection rate and the shadow discrimination rate(the maximum values are 85.79% and 97.56%, respectively) show that the proposed approach achieves a satisfying result with post-processing step.
文摘针对在局部阴影条件下,光伏阵列的功率-电压特性曲线呈现多个峰值,传统群体智能优化存在收敛速度慢、振荡幅度大和易陷入局部最优等问题,提出一种基于PSO-GWO(Particle Swarm Optimization-Grey Wolf Optimization)算法的MPPT(Maximum Power Point Tracking)控制方法。该算法引入余弦规律变化的收敛因子,平衡GWO算法的全局搜索与局部搜索能力;引入PSO算法,提高灰狼个体与自身经验之间的信息交流。仿真结果表明,提出的PSO-GWO算法在局部阴影条件下不仅能快速收敛,而且功率输出震荡幅度更小,有效提升了局部遮阴条件下光伏阵列的最大功率跟踪效率和精度。
文摘局部阴影情况下,光伏阵列输出功率具有多峰值特性,针对最大功率点跟踪(Maximum power point tracking,MPPT)算法在实际应用中存在着收敛速度较慢,效率较低,且容易陷入局部功率极值的问题,将兼顾收敛速度、精度、功率稳定性的快速布谷鸟搜索(Fast cuckoo search,FCS)算法应用于光伏阵列最大功率追踪。FCS算法采用自适应步长和机会因子可避免过早收敛,全局搜索和跳出局部搜索能力强,收敛速度快,算法后期局部开发能力强,功率振荡小,功率输出稳定,最大功率追踪精度高。仿真表明,在静态阴影、动态阴影条件下,FCS算法较灰狼算法(Grey wolf optimizer,GWO)、粒子群算法(Particle swarm optimization,PSO)具有更快地收敛速度和更高的收敛精度,且稳定性好,有效地提升光伏阵列的输出效率。
