基于VSG的正弦锁定技术研究

为了实现新能源系统中各并网运行设备的实时同步,采用了一种不需要进行滤波器设计且计算量小的正弦锁定器技术。本文通过虚拟同步发电机的控制思想模拟同步发电机的运行情况,控制其与电网的功率交换为0,实现对电网输入信号幅值、频率及其相位的同步。仿真分析可知,在输入信号发生阶跃突变时,由于虚拟惯性的存在其输出信号不发生瞬时突变;当输入电压信号中含有幅值为10%基波的2、3、5次谐波成分时,正弦锁定器的输出电压总谐波畸变率从增强型锁相环条件下的4.28%减小到0.01%,有效的验证了正弦锁定器的抗谐波干扰能力。     

2PPPPS-R-2PPPPS新型串并联机构研究

基于传统的串联和并联机构构建了一种新型6自由度串并联机构,通过直线驱动实现输出主轴的三维移动和转动,利用机构分解和综合得到机构的等效形式;同时也对其位置反解进行了研究,发现其符合限定区域条件下的无穷解,且能够利用数值搜索法得到其全部位置反解;通过输出主轴在空间的位置和姿态对各输入运动参数敏感性的影响进行研究与分析,发现同类运动参数之间存在着程度相同或对称关系,得知4类输入运动参数对输出主轴空间位置的敏感性起关键作用,有3类输入运动参数对输出主轴在空间的姿态敏感性起关键作用,同时还以实例形式计算得到具体情形下的敏感性数值,从而知道各类输入运动参数对输出主轴姿态变化上的影响程度的瞬时差异.     

Unsupervised image thresholding: hardware architecture and its usage for FPGA-SoC platform

ABSTRACT

Otsu’s global automatic image thresholding operation is used in various image processing applications. It needs computation of normalized cumulative histogram, mean and cumulative moments that are compute-intensive operations. In this paper, a custom architecture is presented for an efficient computation of Otsu’s algorithm along with its utilization as an intellectual property (IP) core in a field programmable gate array (FPGA) based system-on-chip (SoC) environment for the application of connected component analysis (CCA). A self-normalization technique is employed, where single-cycle, read–modify–write operations are performed with block random access memories (BRAMs) and digital signal processing (DSP)slices. The architecture is designed for 640 × 480 size of images that are captured by a high-resolution analouge camera and buffered in a DDR2 SDRAM of Xilinx ML-507 platform at 25.175 MHz clock frequency. The embedded PowerPC processor core is used to control the frame acquisition process. Experimental results on Virtex-5 xc5vfx70t FPGA device show that the architecture utilizes 1.4% slices, 2.7% BRAMs and 3.9% DSP48E slices. The total power consumption of the design is 1440.59 mW. The proposed architecture as an IP core is able to work in real-time with standard VGA resolution video and requires low computational resources.     

能量高效的传感器网络虚拟骨干网构造算法

提出一种新的可用于无线自组传感器网络路由中的能量高效的虚拟骨干网构造算法。该算法将网络中的节点按照地理距离最近的原则划分为若干簇,簇头与簇成员的距离为k-hop,增大了簇的规模,减少了通信开销;利用最小连通支配集理论优化簇内结构,选择新的参数作为权值,在保证骨干网规模的同时,优先选择剩余能量高的节点担任骨干节点,均衡了网络的能量消耗,从而延长了网络寿命。仿真结果表明,该算法构造的虚拟骨干网规模较小,对降低路由复杂度、延长传感器网络寿命有较好的效果。     

三维旋转激光扫描测量系统中的多视数据拼合

在三维旋转激光扫描测量过程中,如果被测物体为不规则的圆柱类产品,则需要从不同的方位对被测对象进行测量,然后对这多个方位的数据进行拼合。在多视拼合过程中,对重叠区域的数据处理是一个非常关键的问题。为了解决这个问题,本文提出了两种方法,即基于基准点的标记法和点集之间最小距离和方法,同时给出了具体的测量实例。     

社区结构感知的间断连接无线网络路由机制

针对间断连接无线网络中消息投递成功率低的问题1依据网络中节点社会关系的差异性,提出了一种社区结构感知的路由机制.该机制根据节点在各个运动周期内的状态信息建立马尔可夫模型,以描述节点运动状态转换过程,进而以分布式的方式感知节点中心度,并以社区中心度为参数,采用社区标签交换方法对网络结构进行动态检测,最终利用社区内中心节点为中继辅助完成消息的转发.仿真结果表明,所提出的路由机制在投递率方面的性能改善程度接近90％,极大地优化了网络性能.     

LD抽运Nd:YVO4/LBO腔内和频橙黄光连续激光器

报道了一种激光二极管抽运Nd:YVO4晶体、腔内Ⅰ类临界相位匹配LBO和频、连续波输出的全固态橙黄色激光器的设计和实验结果。橙黄色激光由Nd:YVO4晶体的1064nm和1342nm谱线腔内和频产生,输出波长为593.5nm。实验采用了双镜谐振腔结构,在1.6W的808nm注入抽运功率下,获得了最高功率为84mW连续波TEM00的橙黄色低噪声激光输出,光-光转换效率为5.3%,光束质量因子M21.2。实验和分析表明,采用激光二极管抽运Nd:YVO4晶体、LBOⅠ类临界相位匹配腔内和频是获得橙黄色激光的实用方法,并可以应用到Nd:YVO4晶体的其它谱线或具有多条谱线的其它激光增益介质,获得更多不同颜色的单谱线激光输出。     

基于深度神经网络的可编程超表面智能波束形成

通过在超表面单元上加载二极管等有源器件,可编程超表面可实现对电磁波的实时灵活调控。通常利用全波仿真软件计算可编程超表面的辐射场,但该方法需要消耗大量的时间,因而降低了设计效率。为了实现准确高效求解给定编码序列计算辐射场,该文首先设计了辐射场自动测试系统,利用该测试系统实测了少量的编码和辐射场数据,其后提出了一个正向深度...     

信道估计误差对双向中继通信的影响

在基于中继的双向无线通信系统中,分析了两时隙、三时隙和四时隙的中继传输模式的系统和速率性能。考虑到实际通信场景中,信道估计误差的存在使得两时隙和三时隙传输系统的自干扰无法完全消除,研究了信道估计误差对系统和速率性能的影响。仿真结果表明,在公平的发送总功率和信息交换的前提下,两时隙和三时隙传输的和速率在无信道估计误差时在任何信噪比情况下均优于四时隙传输,随着信道估计误差的增加,其和速率显著下降。     

Rheological characterisation of sorbet using pipe rheometry during the freezing process

Sorbet produced without aeration is a dispersion of ice crystals distributed randomly in a freeze-concentrated liquid phase. The rheological properties of this suspension will be affected by the viscosity of the continuous liquid phase and the volume fraction of ice crystals. The knowledge of the viscosity of sorbet is essential for the improvement of product quality, the selection of process equipment, and for the optimal design of piping systems. This work aimed firstly, at studying the influence of the ice volume fraction (determined by the product temperature) on the apparent viscosity of a commercial sorbet, and secondly, to propose a rheological model that describes the evolution of the viscosity of the product as a function of the ice volume fraction. The rheology of sorbet was measured in situ by means of a pipe rheometer connected at the outlet of a continuous scraped surface heat exchanger (SSHE). The pipe rheometer was composed of a series of pipes in PVC of different diameters, making it possible to apply a range of apparent shear rate from 4 to 430 s⁻¹. The flow behaviour index of sorbet decreased as the temperature of the product decreased, the effect of which indicates that the product becomes more shear thinning as the freezing of sorbet occurs. The consistency coefficient and therefore the magnitude of the apparent viscosity of sorbet increased with the decrease in product temperature and with the increase of the ice volume fraction. Results also showed that the rheological model described the experimental data within a 20% error.