In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. ...In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. Main results are given by exact cycle-by-cycle computer simulations as well as theoretical analysis. It is found that the instability phenomenon manifests itself as a fast-scale bifurcation at the switching period, which implies the occurrence of border collision bifurcation, or is related to the transition of the regular operating mode of the SEPIC. According to the theoretical analysis and simulation results, the effects of parameters on system stability, and the locations of the bifurcation points are confirmed. Moreover, the effects of such an instability on power factor and switching stress are also discussed. Finally, the occurrence of the asymmetric bifurcation locations is investigated. The results show that this work provides a convenient means of predicting stability boundaries which can facilitate the selection of the practical parameters.展开更多
针对在无人机高速运动场景下,相关滤波跟踪算法存在边界效应和滤波器退化等问题,提出了一种融合相机运动补偿的自适应时空正则化的无人机跟踪相关滤波算法。首先,在相关滤波器中设计了一种自适应空间正则化方法来缓解边界效应;其次,为...针对在无人机高速运动场景下,相关滤波跟踪算法存在边界效应和滤波器退化等问题,提出了一种融合相机运动补偿的自适应时空正则化的无人机跟踪相关滤波算法。首先,在相关滤波器中设计了一种自适应空间正则化方法来缓解边界效应;其次,为防止滤波器退化,设计了基于高置信度样本的时间正则化方法及优化更新策略,同时利用交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)优化目标函数的求解,保证了算法的运行效率;然后,设计了快速尺度滤波器,实现目标尺度的快速估计;最后,提出了一种鲁棒性的跟踪不确定性规则及基于相机运动补偿的重检测器,使得目标丢失后可及时恢复。实验结果表明,提出的算法在无人机数据集上的精确度和成功率分别可达0.739和0.634,与ECO_HC(Efficient Convolution Operators-Hand Crafted)算法相比分别提升了1.65%和6.9%,与同类主流算法相比,有效地提升了跟踪时的精确度和成功率,经历快速运动、目标遮挡等情况时应用该算法的无人机也表现出良好的跟踪性能。展开更多
在计算大规模介质-金属复合周期结构的电磁散射时,传统积分方程方法存在未知量大、存储占用多和计算时间长等问题。本文采用广义PMCHWT(Poggio-Miller-Chang-Harrington-Wu-Tsai)-电场积分方程(electric field integral equation,EFIE)...在计算大规模介质-金属复合周期结构的电磁散射时,传统积分方程方法存在未知量大、存储占用多和计算时间长等问题。本文采用广义PMCHWT(Poggio-Miller-Chang-Harrington-Wu-Tsai)-电场积分方程(electric field integral equation,EFIE)方法计算均匀介质-金属复合结构的电磁响应。该方法通过在分界面处设置区域连接模型(contact-region modeling,CRM)来保证边界处的连续性。为加速子阵列阻抗矩阵填充,采用快速偶极子方法(fast dipole method,FDM)来提高计算效率并降低内存占用。结合子全域(sub-entire-domain,SED)基函数方法,子阵列的电流分布特征可被推广到大规模介质-金属复合周期结构的电磁场计算中。数值算例表明,本文方法能够在保证计算精度的同时大幅度降低计算代价,内存占用降低至商业软件Altair FEKO(使用多层快速多极子方法)的1/10,计算误差在2.6 dB以内。展开更多
文摘In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. Main results are given by exact cycle-by-cycle computer simulations as well as theoretical analysis. It is found that the instability phenomenon manifests itself as a fast-scale bifurcation at the switching period, which implies the occurrence of border collision bifurcation, or is related to the transition of the regular operating mode of the SEPIC. According to the theoretical analysis and simulation results, the effects of parameters on system stability, and the locations of the bifurcation points are confirmed. Moreover, the effects of such an instability on power factor and switching stress are also discussed. Finally, the occurrence of the asymmetric bifurcation locations is investigated. The results show that this work provides a convenient means of predicting stability boundaries which can facilitate the selection of the practical parameters.
文摘针对在无人机高速运动场景下,相关滤波跟踪算法存在边界效应和滤波器退化等问题,提出了一种融合相机运动补偿的自适应时空正则化的无人机跟踪相关滤波算法。首先,在相关滤波器中设计了一种自适应空间正则化方法来缓解边界效应;其次,为防止滤波器退化,设计了基于高置信度样本的时间正则化方法及优化更新策略,同时利用交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)优化目标函数的求解,保证了算法的运行效率;然后,设计了快速尺度滤波器,实现目标尺度的快速估计;最后,提出了一种鲁棒性的跟踪不确定性规则及基于相机运动补偿的重检测器,使得目标丢失后可及时恢复。实验结果表明,提出的算法在无人机数据集上的精确度和成功率分别可达0.739和0.634,与ECO_HC(Efficient Convolution Operators-Hand Crafted)算法相比分别提升了1.65%和6.9%,与同类主流算法相比,有效地提升了跟踪时的精确度和成功率,经历快速运动、目标遮挡等情况时应用该算法的无人机也表现出良好的跟踪性能。
文摘在计算大规模介质-金属复合周期结构的电磁散射时,传统积分方程方法存在未知量大、存储占用多和计算时间长等问题。本文采用广义PMCHWT(Poggio-Miller-Chang-Harrington-Wu-Tsai)-电场积分方程(electric field integral equation,EFIE)方法计算均匀介质-金属复合结构的电磁响应。该方法通过在分界面处设置区域连接模型(contact-region modeling,CRM)来保证边界处的连续性。为加速子阵列阻抗矩阵填充,采用快速偶极子方法(fast dipole method,FDM)来提高计算效率并降低内存占用。结合子全域(sub-entire-domain,SED)基函数方法,子阵列的电流分布特征可被推广到大规模介质-金属复合周期结构的电磁场计算中。数值算例表明,本文方法能够在保证计算精度的同时大幅度降低计算代价,内存占用降低至商业软件Altair FEKO(使用多层快速多极子方法)的1/10,计算误差在2.6 dB以内。
