基于FIA*-APF算法的蟹塘投饵船动态路径规划

为了提高无人投饵船在含障碍物河蟹养殖池塘自主巡航的作业效率和安全性,该研究提出基于改进A*算法与人工势场法相融合(fusion of improved A*and artificial potential field,FIA*-APF)的蟹塘投饵船动态路径规划算法。首先引入动态加权因子优化A*算法评价函数;其次加入转折惩罚函数并删除冗余点,接着利用B样条曲线对全局路径进行平滑处理;最后将改进A*算法得到的全局路径作为改进人工势场法中的引力路径,生成投饵船自主巡航高效路径。根据养殖池塘创建静态和动态2种仿真环境,分别对传统人工势场法(traditional artificial potential field,TAPF)、基于A*和人工势场法的融合算法(the A*and artificial potential field,TA*-APF)和FIA*-APF算法的性能进行20次测试。仿真试验结果表明:2种环境下,FIA*-APF算法的平均规划时间是TAPF算法的17.23%,是TA*-APF算法的51.96%,平均指令节点数量比TAPF算法减少50.64%,比TA*-APF算法减少65.03%,平均路径长度比TA*-APF算法减少2.82%。蟹塘试验结果表明:FIA*-APF算法的规划时间为TAPF算法的38.16%,为TA*-APF的62.42%,路径长度比TAPF算法减少29.13%,比TA*-APF减少10.15%;另外,TAPF和TA*-APF算法规划路径上大于60°的转角分别是FIA*-APF算法的3.28和2.62倍,大于100°的转角分别是FIA*-APF算法的3.73和1.67倍,该研究算法规划的路径更高效平滑。研究结果可为无人投饵船自主导航提供参考。

基于APF的局部路径规划算法研究

针对传统人工势场法(artificial potential field,APF)规划的路径存在易陷入局部最优与路径不平滑问题,提出一种“触碰引导”策略为先导的控制方法。该方法在无人机运动过程中,引入合适的阶段性子目标点引导无人机飞行,从而降低规划结果陷入局部极值点的概率,并利用贝塞尔曲线法处理控制点以解决路径平滑问题。仿真实验结果表明,改进后的算法能够有效解决易陷入局部极小值点和路径不平滑问题,相较于传统算法效率更高。

关于变频多联机APF能效试验中针对低温制冷实测时准确性的检讨和建议

目前我国多联机变频空调机组均采用全年性能系数(APF)替代IPLV作为评价指标。基于现有多联变频空调器的调节范围广的特点,指出了现有APF中对于选择性试验即低温制冷工况实测时,会出现不符合实际的情况,利用实测数据和理论分析产生的原因,水平展开,并给出了针对实测的改进建议。

矿井救援机器人的B样条-APF-BRRT路径规划方法

针对矿井非结构化、形状狭长的地形结构以及传统BRRT算法规划路径曲折、转折点较多等路径质量较差问题,提出一种基于B样条-APF-BRRT算法的矿井救援机器人路径规划方法。首先根据BRRT路径中产生的目标点和矿井环境中障碍物信息,引入APF目标引力的思想,构建人工势场;然后利用Douglas-Peuker算法进行分线段处理,重新提取关键节点;最后使用B样条函数进行光滑拟合获得路径,减少了APF-BRRT算法所得路径的转折点和长度。对B样条-APF-BRRT算法进行实验,结果表明改进算法所获路径转折点和长度都明显优于BRRT算法,在矿井狭窄巷道中,相对于BRRT算法,B样条-APF-BRRT方法产生的路径更加平滑,转折次数减少到9次,路径长度减少了7.73%。

基于改进麻雀算法的多APF协调控制研究

有源电力滤波器(APF)因其具有快速追踪和消除谐波的功能而广泛应用于配电网中。其中,LCL型APF对高频谐波有更好的抑制能力。随着APF并网数目的日益增多,各APF间的交互影响问题变得不可忽视。针对多APF间的交互影响,首先基于诺顿定理推导了多APF并网等效模型,其次利用广义动态相对增益矩阵(GDRGA)对交互影响进行定量分析,最后将抑制交互影响转化为多目标优化问题。针对传统麻雀算法在搜索后期存在全局寻优能力差、易陷入局部最优的缺陷,引入tent混沌和动态随机柯西变异进行改进,并采用改进麻雀算法对APF各控制参数进行协调优化。结果表明,改进麻雀算法能得到分布更加良好的pareto解集,求解性能更优,多目标优化后能有效抑制APF间的交互影响,验证本文所提方法的有效性。

POMDP-APF:一种基于POMDP模型的APF无人机路径规划策略

针对无人机在路径规划过程中会遇到静态或者动态的障碍物,从而导致路径规划失败的问题,提出一种基于部分可观测马尔可夫决策过程(partially observable Markov decision process,POMDP)模型的人工势场(artificial potential field,APF)无人机路径规划策略(POMDP-APF)。首先使用传感器获得的障碍物信息结合POMDP模型预测障碍物的未来位置,为无人机的路径规划做准备;其次,提出一种新的基于障碍物的正方体外接球的模型,保障无人机在路径规划过程中的安全性;最后,结合改进的APF算法实现无人机的路径规划。仿真结果表明,POMDP-APF策略在无人机实时路径规划中具有良好的可行性和有效性,使无人机能够有效避开障碍物,同时路径长度以及耗费时间更短。

变频空调器APF快速计算的显式表达式

国家标准中给出的空调器能效指标APF的确定方法,包含一系列的判断与嵌套计算,过程复杂。本文旨在将新版空调器能效标准GB 21455—2019中给出的APF系列计算公式转化为显式计算式,从而满足APF计算便捷的要求。首先采用将自变量直接代入的方法对国标定义的APF的4个中间变量进行化简;然后通过数值拟合的办法对化简计算式中需要判定计算区间与分段计算的过程进行简化;最后将4个中间变量的显式表达式代入APF定义式中,得到APF显式表达式。开发的APF显式表达式适用于所有额定制冷量范围的变频空调器并有良好的精度,其中5测试工况点、7测试工况点的APF显式表达式相比于空调器能效标准中APF的定义式计算误差分别为0.73%、1.17%。

Microstructure,mechanical property and in vitro biocorrosion behavior of single-phase biodegradable Mg-1.5Zn-0.6Zr alloy

The microstructure,mechanical property,and in vitro biocorrosion behavior of as-cast single-phase biodegradable Mg-1.5Zn-0.6Zr alloy were investigated and compared with a commercial as-cast AZ91D alloy.The results show that the Mg-1.5Zn-0.6Zr alloy had a single-phase solid solution structure,with an average grain size of 34.7±13.1μm.The alloy exhibited ultimate tensile strength of 168±2.0 MPa,yield strength of 83±0.6 MPa,and elongation of 9.1±0.6%.Immersion tests and electrochemical measurements reveal that the alloy displayed lower biocorrosion rate and more uniform corrosion mode than AZ91D in Hank's solution.The elimination of intensive galvanic corrosion reactions and the formation of a much more compact and uniform corrosion film mainly account for the better biocorrosion properties of the Mg-1.5Zn-0.6Zr alloy than AZ91D.

Dynamic behavior of coalbed methane flow along the annulus of single-phase production

Dynamic behavior of coalbed methane (CBM) flow will provide the theoretical basis to optimize production performance for a given well.A mathematical model is developed to simulate flowing pressures and pressure drops of CBM column from well head to bottom hole.The measured parameters and independent variables of flow rates,flowing pressures and temperatures are involved in CBM producing process along the annulus.The developed relationships are validated against full-scale measured data in single-phase CBM wellbores.The proposed methodology can analyze the dynamic behavior in CBM reservoir and process of CBM flow with an overall accuracy of 2%.The calculating process of flowing pressures involves friction factor with variable Reynolds number and CBM temperature and compressibility factor with gravitational gradients.The results showed that the effect of flowing pressure on CBM column was more obvious than that on CBM and water column accompanied by an increase of dynamic water level.The ratios of flowing pressure on increment of CBM column to the whole column increased with the declined flow rates of water column.Bottom-hole pressure declined with the decreased flowing pressure of CBM column along the annulus.It will lead to the results of the increased pressure drop of CBM column and CBM flow rate in single-phase CBM wellbores.

Prediction of Outdoor Noise Propagation Induced By Single-Phase Power Transformers

Outdoor power transformers are one of the most pervasive noise sources in power transmission and distribution systems.Accurate prediction of outdoor noise propagation plays a dominant role for the evaluation and control of noise relevant to the transformer stations.In this paper surface vibration tests are carried out on a scale model of a single-phase transformer tank wall at different excitation frequencies.The phase and amplitude of test data are found to be randomly distributed when the excitation frequency exceeds the seventh mode frequency,which allows the single-phase power transformer to be simplified as incoherent point sources.An outdoor-coherent model is subsequently developed and incorporated with the image source method to investigate noise propagation from single-phase power transformers,due to the occurrence of multiple reflections and diffractions in the propagation path of each point source.The proposed model is used to calculate the sound field of the power transformer group by exploiting the additional phase information.In comparison with the ISO9613 model and the boundary element method,it is found that the proposed coherent image source method leads to more accurate prediction results,and hence better performance for the prediction of the outdoor noise induced by single-phase power transformers.

Symmetrical dynamical characteristic of peak and valley current-mode controlled single-phase H-bridge inverter

Complex dynamical phenomenon was studied in the single phase H-bridge inverter which was controlled by either a peak current or a valley current. The state functions and the discrete iterative map equations were established to analyze the dynamical phenomenon in the single phase H-bridge inverter. The dynamical characteristics of the single phase H- bridge inverter, such as time domain waveform diagram, bifurcation diagram, and folding map, were obtained by using the numerical calculation when the circuit parameters varied in specific range. Moreover, the simulation results were obtained by using the OrCAD-PSpice software to validate the numerical calculation. Both the numerical calculation and the circuit simulation show that the symmetrical dynamical phenomenon occurs in the single phase H-bridge inverter controlled by the peak current or the valley current.

The Use of Single-Phase Immersion Cooling by Using Two Types of Dielectric Fluid for Data Center Energy Savings

Data centers are recognized as one of the most important aspects of the fourth industrial revolution since conventional data centers are inefficient and have dependency on high energy consumption,in which the cooling is responsible for 40%of the usage.Therefore,this research proposes the immersion cooling method to solving the high energy consumption of data centers by cooling its component using two types of dielectric fluids.Four stages of experimentalmethods are used,such as fluid types,cooling effectiveness,optimization,and durability.Furthermore,benchmark software is used to measure the CPU maximum work with the temperature data performed for 24 h.The results of this study show that the immersion cooling reduces 13℃ lower temperature than the conventional cooling method which means it saves more energy consumption in the data center.The most optimum variable used to decrease the temperature is 1.5 lpm of flow rate and 800 rpm of fan rotation.Furthermore,the cooling performance of the dielectric fluids shows that the mineral oil(MO)is better than the virgin coconut oil(VCO).In durability experiment,there are no components damage after five months immersed in the fluid.

GB 21455—2019中低温中间制冷工况参数获取方法不唯一导致的APF值计算的问题分析

按GB 21455—2019确定空调器能效APF时,低温中间制冷工况性能参数既可采用测试法也可采用换算法;同一空调器在这2种不同的方法下,会有2种不同的APF值。针对国标规定中的方法不唯一而造成的结果差异,需要分析产生该差异的合理性,提出改进方案。本文基于APF的定义公式,分析采用测试法和换算法获取低温中间制冷工况性能参数造成APF存在差异的原因;指出国标中给出的测试法,会导致额定中间制冷工况能效的变化趋势与计算得到的APF值变化趋势相反,这是不合理的。将国标规定的获取低温中间制冷工况性能参数的方法,由“既可测试获得也可根据额定中间制冷工况参数换算获得”改为“仅能根据额定中间制冷工况参数换算获得”是可供选择的解决方案。

Real-Time Method for Detecting Harmonic and Reactive Currents of Single-Phase Circuits

According to the characteristics of single-phase circuits and demand of using active filter for real-time detecting harmonic and reactive currents, a detecting method based on Fryze＇s power definition is proposed. The results of theoretical analysis and simula- tion show that the proposed method is effective in realtime detecting of instantaneous harmonic and reactive currents in single-phase circuits. When only detecting the total reactive currents, this method does not need a phase-locked loop circuit, and it also can be used in some special applications to provide different compensations on the ground of different requirements of electric network. Compared with the other methods based on the theory of instantaneous reactive power, this method is simple and easy to realize.

基于以太网上位机的三电平APF实验监测平台设计

现代电力系统存在大量的非线性负载,产生的电流谐波严重污染电力环境,三电平有源电力滤波器(active power filter,APF)是一种动态抑制谐波的电力电子装置。该文设计了三电平APF电流环,并使用二阶广义积分器(second-order general integrator,SOGI)锁相环提升谐波补偿效果。为观测APF系统的负载电流、网侧电压/电流等多路电量,设计了基于以太网上位机的三电平APF实验监测平台。平台使用W5300芯片搭建以太网通信电路硬件,使用Visual Studio编写APF监控系统上位机软件。实验结果表明该实验平台能够有效补偿谐波电流,基于以太网上位机可观测多路电压、电流波形,以及控制系统内部变量,便于实验平台的调试和监测。

Modified surface tension model for free surface flow with single-phase lattice Boltzmann method

A single-phase lattice Boltzmann model with modified surface tension is developed in this paper to solve the problem of high-density-ratio free surface flow.The computational efficiency and accuracy are both enhanced.The restriction to the relaxation factor （which needs to be smaller than 1） is circumvented by the new surface tension algebra,due to its rational physical nature compared with the treatment of Xing,Buther and Yang in their paper （Comp.Mater.Sci.,2007,39（2）：282-290）.The proposed stable surface tension scheme is applied to simulate the free deformation of a square droplet with surface tension effect and the process of a droplet impinging on a liquid film.The numerical solution for free deformation of a droplet agrees well with thermodynamic principles,and also achieves high accuracy in comparison with Xing,et al.＇s model.Three typical impinging modes are successfully obtained with the new scheme,and another particular mode found by Wang and Chen is also successfully simulated.The evolutions of liquid crown agree well with the power law related to time.

基于PSC-PWM的MMC-SAPF中压配电网谐振阻尼技术

中压(medium voltage,MV)配电网中无功补偿电容器易与网侧电感形成并联谐振,放大公共耦合点(point of common coupling,PCC)电压。为了应对两电平并联型有源电力滤波器(shunt active power filter,SAPF)不适用于中压配电网场合,且只抑制谐波不能解决谐波与谐振同时存在的问题,提出了一种基于模块化多电平的并联型有源电力滤波器(modular multilevel converter based SAPF,MMC-SAPF)的谐振阻尼技术。首先分析了MMC-SAPF的工作原理,采用载波移相调制策略(phase shifted carrier PWM,PSC-PWM)以及电容电压平衡控制策略,以实现MMC-SAPF的高等效开关频率。然后分析了MV配电网的谐振机理,指出谐波抑制策略失效的原因,在此基础上,提出将MMC-SAPF控制为谐振频率处的虚拟电阻,提高系统阻尼比以治理谐振。搭建了一台60 V/2 kVA的实验样机,并构建7次谐振环境,实验结果验证了复合控制策略阻尼谐振的有效性。

Industrial frequency single-phase AC traction power supply system for urban rail transit and its key technologies

To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation （MSS） and cable traction network （CTN）. The MSS includes a single-phase main traction transformer and a negative-se- quence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as （1） the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; （2） the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; （3） a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.

LCL型APF在含非线性负荷系统中的应用

非线性负荷和电力电子器件的广泛并入,导致电网电压与电流正弦波畸变,电能质量降低。目前国内外比较主流的滤波装置,如PPF(无源电力滤波器)、APF(有源滤波器)、UPQC(统一电能质量调节器)等,由于自身的特点和缺陷,并不能对各种谐波起到很好的抑制效果。故本文提出了一种ILCLI型APF混合滤波器,协调控制以降低电网谐波含量,在降低非线性负荷谐波的同时,还能滤除开关频率附近的谐波。通过MATLAB/SMULNK建立混合滤波器仿真模型,经过FFT(快速傅里叶变换)分析,验证本模型不仅可以能够动态抑制谐波,而且能够很好地滤除开关谐波。