OPTIMAL ALGORITHM FOR NO TOOl-RETRACTIONS CONTOUR-PARALLEL OFFSET TOOL-PATH LINKING

A contour-parallel offset （CPO） tool-path linking algorithm is derived without toolretractions and with the largest practicability. The concept of ＂tool-path loop tree＂ （TPL-tree） providing the information on the parent/child relationships among the tool-path loops （TPLs） is presented. The direction, tool-path loop, leaf/branch, layer number, and the corresponding points of the TPL-tree are introduced. By defining TPL as a vector, and by traveling throughout the tree, a CPO tool-path without tool-retractions can be derived.

Cancellation for frequency offset in OFDM system based on TF-LMS algorithm

In an orthogonal frequency division multiplexing(OFDM) system,a time and frequency domain least mean square algorithm(TF-LMS) was proposed to cancel the frequency offset(FO).TF-LMS algorithm is composed of two stages.Firstly,time domain least mean square(TD-LMS) scheme was selected to pre-cancel the frequency offset in the time domain,and then the interference induced by residual frequency offset was eliminated by the frequency domain mean square(FD-LMS) scheme in frequency domain.The results of bit error rate(BER) and quadrature phase shift keying(QPSK) constellation figures show that the performance of the proposed suppression algorithm is excellent.

Calculation of impact factor of vibrator oscillation in offset printing based on fuzzy controller and genetic algorithm

In the inking system of an offset printing press,a vibrator roller distributes ink not only in the circumferential direction but also in the axial direction.In the control process,if ink amount is determined only by the dot area coverage without considering the impact of vibrator roller's oscillation,the printing colour quality will be reduced.This paper describes a method of calculating the impact factor of vibrator roller' s oscillation.First,the oscillation performance is analyzed and sample data of impact factor is got.Then,a fuzzy controller used for the calculation of the impact factor is designed,and genetic algorithm is used to optimize membership functions and obtain the fuzzy control rules automatically.This fuzzy controller can be used to calculate impact factors for any printing condition,and the impact factors can be used for ink amount control in printing process and it is important for higher printing colour quality and lowering ink and paper waste.

Blind cancellation for frequency offset in OFDM system based on MCMA-RLS algorithm

Modified constant modulus and recursive least squares （MCMA-RLS） algorithm is proposed to cancel interference caused by the variable frequency offset （FO） in the orthogonal frequency division multiplexing （OFDM） system. The MCMA-RLS algorithm is composed of two stages including MCMA scheme and RLS scheme. MCMA is selected to pre-cancel the variable frequency offset firstly, and then the residual interference has been canceled by the RLS scheme. BR error rate is simulated to demonstrate that the proposed method is robust for canceling the variable frequency offset.

快速成型系统中OFFSET型填充算法

在SW 2 50 1快速成型系统中 ,零件的制作是靠热喷头喷出热熔丝逐层堆积成型的 ,在逐层堆积过程中 ,热喷头要做大量的填充扫描 ,填充方法直接影响零件的成型质量 .文中介绍了一种基于截面轮廓的OFFSET型填充路径的生成算法 ,该算法快速可靠 ,能得到比较光滑、平整的成型截面 .

LDPC码offset BP-Based译码算法研究与硬件实现

低密度奇偶校验(Low-Density Parity-Check LDPC)码是一种接近Shannon极限的信道编码,在低信噪比的环境下仍能获得优异的误码率性能,目前应经成为编码界的热点研究课题之一。本文在探讨了LDPC码的经典BP(Belief Propaga-tion)译码算法的基础上,通过分析比较,选取一种复杂度较低,性能较好的offset BP-Based译码算法在FPGA上进行实现,验证了LDPC码的优异性能,对于译码算法的硬件实现具有指导意义。

Research on An Improved PMF-FFT Fast PN Code Acquisition Algorithm

To solve the problem of the large Doppler frequency offset in the LEO communication system, this paper studies a rapid PN code acquisition method based on the PMF-FFT architecture, which searches the phase and frequency offset and at the same time reduces the acquisition time. It presents an improved method equivalent to windowing function and uses windowing process to overcome the attenuation of related peak envelope caused by partial matched filters.

Joint synchronization estimation based on genetic algorithm for OFDM/OQAM systems

This paper investigates the problem of synchronization for offset quadrature amplitude modulation based orthogonal frequency division multiplexing(OFDM/OQAM) systems based on the genetic algorithm. In order to increase the spectrum efficiency,an improved preamble structure without guard symbols is derived at first. On this basis, instead of deriving the log likelihood function of power spectral density, joint estimation of the symbol timing offset and carrier frequency offset based on the preamble proposed is formulated into a bivariate optimization problem. After that, an improved genetic algorithm is used to find its global optimum solution. Conclusions can be drawn from simulation results that the proposed method has advantages in the joint estimation of synchronization.

Large Spacing Array with Offset Phase Center Elements for Highly Integrated Applications

A scanning and uniform array architecture with large spacing,low complexity and high scalability is presented for high integration massive array applications.It is constructed by offset phase center elements arranged in a uniform and regular way,but its spacing can be larger than that of traditional arrays.An ideal model of the offset phase center element is established and its far-field distribution is derived.To suppress grating lobes,the phase center of any element is designed to be movable without changing its physical position.Using genetic algorithm(GA),a new constraint condition limiting the number of phase center changes is proposed to solve the objective function of the minimum values of grating lobes(GLs)and side lobes(SLs).It is shown that the optimal results can be achieved by two changes of phase centers.A multimode circular patch is developed and designed,and characteristics of the offset phase center are analyzed and verified.A prototype array of 12×12 offset phase center elements is implemented based on multi-mode circular patches.Full wave simulation results of radiation patterns show that the level of grating lobes is suppressed at least 7dB with 1.12λ spacing,while the scanning angle is 20°.

Measurement of Apex Offsets for Fiber Connector End Faces

As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the parameter, connector rotating-π method, is proposed. With the method, the apex offset of a common connector end face is measured. The result is compared with that measured by a Norland 3000 fiber connector end face interferometer. It is found that the difference between two results is 1.8μm. Meantime, the influences of relevant error resources on apex offset measurement under rotating-π method and apex-core method are respectively analyzed, and two error equations are derived. The analytical result shows that, compared with apex-core method, if two additional sub-tilts of axis within and in the direction perpendicular to principal plane caused by its rotation are not bigger than the original axis tilt angle, the max. measurement error will then be reduced by at least 22.5% with rotating-π method. The practicability of the method is confirmed by the experiments.

A Domain Extension Algorithm for Digital Error Correction of Pipeline ADCs

A domain extension algorithm to correct the comparator offsets of pipeline analog-to-digital converters (ADCs) is presented, in which the 1.5-bit/stage ADC quantify domain is extended from a three-domain to a five-domain. This algorithm is designed for high speed and low comparator accuracy application. The comparator offset correction ability is improved. This new approach also promises significant improvements to the spurious-free dynamic range (SFDR), the total harmonic distortion (THD), the signal-to-noise ratio (SNR) and the minor analog and digital circuit modifications. Behavioral simulation results are presented to demonstrate the effectiveness of the algorithm, in which all absolute values of comparator offsets are set to |3Vref/8|. SFDR, THD and SNR are improved, from 34.62-dB, 34.63-dB and 30.33-dB to 60.23-dB, 61.14-dB and 59.35-dB, respectively, for a 10-bit pipeline ADC.

一种LDPC码的优化分层阈值偏移最小和译码算法

针对低密度奇偶校验(Low-Density Parity-Check,LDPC)码的译码算法在高信噪比区域性能较差和传统的泛洪调度译码方式收敛速度较慢等问题,提出了一种优化的分层阈值偏移最小和(Improved Layered Threshold Offset Min-Sum,ILTOMS)LDPC译码算法。该算法通过在最小值近零处添加一个阈值,在最小值小于该阈值的情况下选择局部最优的算法规避偏移最小和(Offset Min-Sum,OMS)译码算法的归零损失,在最小值较大时设置一个阈值来改善高信噪比时的译码性能,并且采用分层调度的方式进一步提高译码性能。仿真结果表明,所提的ILTOMS译码算法在复杂度无明显变化的情况下有一定性能增益,相比其他两种译码算法译码性能分别提升了0.4 dB和0.45 dB。

力-热耦合下的MEMS传感器位置偏移自校准方法

在解决力-热耦合作用引发的微机电系统(Micro-Electro-Mechanical System,MEMS)传感器位置偏移问题时,通常运用传统遗传算法实现位置偏移自校准,受到固定参数的影响,该算法容易得到局部最优解,使得自校准后的MEMS传感器测量误差依旧较大。因此,提出一种力-热耦合下的MEMS传感器位置偏移自校准新方法。采用数据融合思想,将多批次采集的MEMS传感器测量数据汇总起来,对比与真实数据之间的差异,判断传感器是否在力-热耦合作用下偏移出工作区。引入误差相位偏移法进一步处理传感器测量数据,获取等间隔变换误差序列,解算出传感器误差模型,以此来体现传感器位置偏移变化。以传感器位置偏差最小化为目标,设定偏移自校准目标函数,并运用结合自适应调整思想的改进型遗传算法进行寻优求解,获取最优自校准参数取值。实验结果表明:以嵌入式角位移传感器为例,运用该方法完成自校准处理后,传感器的测量误差峰值保持在6″以下,有效解决了力-热耦合作用引起的传感器精度损失问题。

中心不重合径向剪切干涉迭代波前重构算法仿真分析

径向剪切干涉测量时经常会出现扩束与缩束光波中心不重合情况,传统波前重构算法会导致较大重构误差,其应用受到挑战。推导了中心不重合径向剪切干涉迭代波前重构算法,仿真分析了组合像差、单阶Zernike像差、中心偏移量大小及其计算误差对重构算法的影响。结果表明,在剪切光波中心不重合情况下,该文算法能够准确进行波前重构,重构效果显著优于传统算法;在论文仿真条件下,随着中心偏移量的增大,本文算法重构波面均方根误差(RMS)不高于0.05λ,而传统算法重构误差RMS值达1.6λ且与偏移量近似线性相关。

基于改进FCOS的遥感图像舰船目标检测

由于遥感图像中舰船目标方向任意,基于深度学习的通用目标检测算法采用水平框,在检测舰船时易框选大量背景,检测效果欠佳。文中提出一种改进全卷积一阶段目标检测网络(FCOS)的遥感图像舰船目标检测算法,以FCOS为基线,在检测头部分增加一条偏移回归分支,通过偏移水平框的上边中点和右边中点,产生旋转框。舰船目标通常具有较大的长宽比,预测框与真实框之间的角度偏差对交并比的影响较大,进而影响模型的检测精度。针对该问题,在计算偏移损失时引入与舰船目标长宽比有关的加权因子,使得具有较大长宽比的目标获得较大的偏移损失。在HRSC2016数据集上的实验结果表明,所提算法的平均精确度达到89.00%,检测速度达到19.8FPS,相比同类型的无锚框算法,其在检测速度和检测精度上均表现优秀。

基于自适应加权增强总变差的CT偏置扫描重建算法

基于降低设备制造成本或辐射剂量等目的,计算机断层成像(Computer Tomography,CT)中的一个实际需求是以有限的探测器尺寸来获得更大的视野(Field of View,FOV),通过将探测器放置在横向偏移位置可以有效的扩大FOV。然而,常规的重建算法无法精确重建偏置投影数据,针对这一问题,本文提出了一种基于自适应加权增强总变差最小化的偏置重建模型及CP(Chambolle-Pock)求解算法。具体来说,构建自适应加权增强总变差范数作为正则项,其中自适应权重根据局部增强梯度自适应调整权值,进而设计了一种基于自适应加权增强总变差最小化的偏置重建模型(Weighted Adaptive-weight reinforced Total Variation,WAwrTV),并推导出了相应的CP算法。实验结果表明,所提算法能有效的重建偏置投影数据并提高重建精度,且具有良好的抗噪性能。

基于相控阵超声的汽车后桥螺旋锥齿轮畸变控制方法

由于汽车后桥螺旋锥齿轮畸变控制的过程中易受畸变回波的影响,存在大量的噪声信号,导致控制误差较大、控制精度较低及控制效果较差,为此,提出基于相控阵超声的汽车后桥螺旋锥齿轮畸变控制方法。首先采用相控阵超声技术采集汽车后桥螺旋锥齿轮的振动信号,并将采集后的齿轮振动信号通过异性扩散降噪法进行降噪处理;然后根据降噪处理结果,采用畸变散射算法计算散射波的散射幅值,获取畸变信号的回波特性,采用曲线矩阵回波算法对畸变信号进行定位,得到畸变信号位置点后,提取畸变信号的特征;最后根据多普勒效应,计算畸变信号特征的频偏曲率,采用重采样畸变控制技术根据不同段的频偏基准点重新采样,进行齿轮畸变控制。实验结果表明,所提方法的畸变控制精度高、效果好。

基于云边协同的交直流混联电网线路过负荷协调控制方法

针对交直流混联电网线路过负荷影响因素较多导致线路运行特征难捕捉、难以实现精准控制的问题,提出基于云边协同的过负荷协调控制方法。建立过负荷状态数学模型,采用解耦算法求解不同程度过负荷情况下电力参数增量值并进行特征提取,将其作为云边协同算法的云计算参照值,获得同时符合功率最佳、能耗最小以及避免切负荷要求的协调控制参数,实现协调控制。实验结果表明:云边协同方法在盲区约束下可以准确检测盲区以外的所有节点,未出现漏检现象;光伏、风电出力的节点功率变化明显高于正常节点,节点过负荷控制效果较好。

车载紧凑式换热器高效轻质的性能优化研究

针对当前车载锯齿型板翅式换热器在某新型车辆有限空间内传热与流动阻力性能不足、整机质量大的问题,提出了一种车载锯齿型板翅式换热器的优化方案。首先,对4种具有不同翅片参数的空气-水车载锯齿型板翅式换热器进行了实验测试,探究了已有换热器的传热与流动特性;然后,基于实验数据构建了锯齿型翅片通道的三维数值计算模型,获得了适用结构参数范围更加宽泛且拟合精度良好的换热器流动换热关联式,同时基于换热器几何结构获得了整机质量计算模型;最后,结合非支配排序遗传算法(NSGAⅡ)以及传热与流动阻力综合性能评价图,开展了车载锯齿型板翅式换热器关键翅片结构参数的多目标优化研究,给出了综合性能优异的换热器结构参数。结果表明:优化后锯齿型板翅式换热器的阻力系数降低了14.3%,综合性能评价因子增加了10.7%,整机质量减少了18.2%,实现了换热器高效轻质的优化目标。所提车载锯齿型板翅式换热器优化方案,对提升其综合性能与降低制造成本具有参考价值。

基于改进RRT算法的冗余机械臂路径规划研究

针对RRT算法在机械臂路径规划的过程中无方向性,在无障碍物处产生过多无用节点的问题,采用目标偏置、双向分段搜索的策略对RRT算法进行改进,提出了具有导向性的双向分段搜索的改进RRT算法并应用于七自由度冗余机械臂的路径规划上,通过Matlab进行了三维环境路径规划仿真实验,并通过ROS平台进行冗余机械臂在简单环境与狭窄环境的避障仿真实验。实验结果表明,改进的RRT算法能够有效地减少路径的节点数量与搜索时间,并提高路径规划的成功率。