恶劣天气下的仿生偏振定向方法

针对偏振光导航在恶劣天气下精度显著下降的问题，提出了一种可以在恶劣天气下基于大气偏振模式的定向算法。与现有方法相比，首次将三维块匹配与canny边缘检测结合的思想应用于修复被不同天气破坏的偏振角度图像中。具体而言，将偏振角度图像的修复分为噪声粗处理和边缘提取处理去噪两部分。在噪声粗处理阶段采用三维块匹配算法,在边缘提取处理去噪部分，利用canny边缘检测算法对偏振角度图像进行二次去噪。实验结果表明，该方法不仅能够提高晴朗天空下的定向精度，而且能够显著提升在阴天、沙尘、雾霾等恶劣天气条件下的导航定向精度，即使在偏振角图像对称∞模式被破坏的情况下，航向角精度仍可由9.4470°提高到1.6859°。     

恶劣天气下的仿生偏振定向方法

针对偏振光导航在恶劣天气下精度显著下降的问题,提出了一种可以在恶劣天气下基于大气偏振模式的定向算法。与现有方法相比,首次将三维块匹配与canny边缘检测结合的思想应用于修复被不同天气破坏的偏振角度图像中。具体而言,将偏振角度图像的修复分为噪声粗处理和边缘提取处理去噪两部分。在噪声粗处理阶段采用三维块匹配算法,在边缘提取处理去噪部分,利用canny边缘检测算法对偏振角度图像进行二次去噪。实验结果表明,该方法不仅能够提高晴朗天空下的定向精度,而且能够显著提升在阴天、沙尘、雾霾等恶劣天气条件下的导航定向精度,即使在偏振角图像对称∞模式被破坏的情况下,航向角精度仍可由9.4470°提高到1.6859°。     

Z-源稀疏矩阵变换器励磁的双馈风力发电系统

针对矩阵变换器电压传输比低和其励磁的双馈风力发电系统(DFIG)易受非正常输入波动影响的不足,提出了一种适用于DFIG励磁的Z-源稀疏矩阵变换器系统。利用Z-源的升压特性来提高电压传输比,检测电容电压实现对直通因子的自动调节,从而实现对网侧波动的自动抑制。建立了系统数学模型,推导了DFIG系统定子磁场定向矢量控制策略表达式,搭建试验样机对所提方案进行试验验证,在亚同步、同步、超同步三种发电状态下的波形和并网试验结果验证了方案的可行和有效性。     

Effects of fiber orientation on tool wear evolution and wear mechanism when cutting carbon fiber reinforced plastics

The aim of the present paper is to reveal the influence of different fiber orientations on the tool wear evolution and wear mechanism. Side-milling experiments with large-diameter milling tools are conducted. A finite element (FE) cutting model of carbon fiber reinforced plastics (CFRP) is established to get insight into the cutting stress status at different wear stages. The results show that different fiber orientations bring about distinct differences in the extent, profile and mechanism of tool wear. Severer wear occurs when cutting 45° and 90° plies, followed by 0°, correspondingly, the least wear is obtained when θ = 135° (θ represents the orientation of fibers). Moreover, the worn profiles of cutting tools when θ = 0° and 45° are waterfall edge, while round edge occurs when θ = 135° and a combined shape of waterfall and round edge is obtained when θ = 90°. The wear mechanisms under different fiber orientations are strongly dependent on the cutting stress distributions. The evolution of tool wear profile is basically consistent with the stress distribution on the tool surface at different wear stages, and the extent of tool wear is determined by the magnitude of stress on the tool surface. Besides, the worn edges produce an actual negative clearance angle, which decreases the actual cutting thickness and leads to compressing and bending failure of fibers beneath the cutting region as well as low surface qualities.