State Flow混杂系统的BUCK变换器设计

尝试用包含连续状态变量和离散开关变量的混杂动态系统模型描述BUCK型DC-DC变换器。依据混杂系统的概念和模型,基于BUCK电路理论,采用一种新型控制方法,给出混杂系统的控制边界,建立BUCK电路中的变化器和控制器两个单元混杂机器。通过数学表达式对模型进行描述,阐述两个单元混杂机器联合工作流程。以24-12 V降压变换器的BUCK电源设计为例使用State Flow仿真和实验研究,验证了该方法的有效性。与传统平均法相比,基于混杂动态系统的模型中没有线性近似处理,理论上可以得到更加精确的模型,更高效实现对电力电子电路的控制。

基于Fuzzy Logic与State flow的汽车换挡策略研究

针对车辆在复杂的路况下行驶时,车辆自动变速器的频繁换挡和车辆动力不足的问题,设计了一种基于升、降档模糊控制器基本模块的换挡策略.升降挡模糊控制器模块是以加速度的正负作为控制参量,加速度为正时,基于升档规律曲线的升档模糊控制器起作用;加速度为负时,基于降档规律曲线的降档模糊控制器起作用.通过State Flow的逻辑来判断哪个控制器起作用.在上述基本模块的基础上,建立了以制动力的大小,弯道大小以及坡度大小作为控制输入参数的模糊修正模块,其输出对上述基本模块的升档模糊控制器和降档模糊控制器的输出进行修正.仿真结果表明:所设计的换挡控制策略具有很好的避免频繁换挡和动力不足的问题.

基于Stateflow的民机自动飞行工作模式切换

Stateflow是有限状态机原理的图形化实现,可以实现连续状态间的切换.民机的自动飞行系统在各个飞行阶段对应着几十种工作模式,正是一个有限状态机系统.文中基于Stateflow对各工作模式及其逻辑关系进行了建模,实现了工作模式模型对其对应的控制律的调用,并对制定的飞行任务进行了仿真.结果表明,民机自动飞行系统工作模式间的切换可以通过Stateflow较好地实现.

基于Stateflow的无人机多模态控制转换逻辑设计

针对基于Simulink建立的无人机飞行管理系统存在逻辑复杂、全飞行状态航迹仿真建模繁琐等缺点,文章利用有限状态机建立无人机全状态、多种导航控制模态下的控制和逻辑切换流程,并结合飞行管理系统、飞行控制系统和无人机运动学模型建立无人机全状态仿真系统,通过仿真对飞行工作模式的切换效果进行了验证。

移动信道Markov模型的Stateflow仿真技术

针对具有长突发误码特性的无线信道特征,根据移动通信系统的仿真要求,基于简单分群马尔科夫(Markov)信道模型,提出了利用stateflow技术的信道仿真方法,并生成移动信道的差错序列。仿真结果表明,该信道模型能够有效地描述无线移动信道的统计特性,并具有可视化、流程化和层次化的特点,在无线移动通信系统的软件仿真中具有实用性。

Application of empirical mode decomposition based energy ratio to vortex flowmeter state diagnosis

To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter.

Direct Calculation of Unsteady-State Weymouth Equations for Gas Volumetric Flow Rate with Different Friction Factors in Horizontal and Inclined Pipes

Direct calculations of unsteady-state Weymouth equations for gas volumetric flow rate occur more frequently in the design and operation analysis of natural gas systems. Most of the existing gas pipelines design procedures are based on a particular friction factor and steady-state flow analysis. This paper examined the behavior of different friction factors and the need to develop model analysis capable of calculating unsteady-state gas flow rate in horizontal and inclined pipes. The results show different variation in flow rate with Panhandle A and Panhandle B attaining stability in accurate time with initial unsteadiness at the instance of flow. Chen and Jain friction factors have opposition to flow with high flow rate: The prediction also reveals that Colebrook-White degenerated to Nikuradse friction factor at high Reynolds number. The horizontal and inclined flow equations are considerably enhanced on the usage of different friction factors with the aid of Matlab to handle these calculations.

Resistance characteristics of paste pipeline flow in a pulse-pumping environment

Paste flow patterns and microscopic particle structures were studied in a pressurized environment generated by a pulse pump.Complex loop-pipe experiments and fluid-solid coupling-based simulations were conducted.The scanning electron microscopy technique was also applied.Results revealed that flow resistance is closely related to pipeline curvature and angle in a complex pipe network.The vertical downward-straight pipe-inclined downward combination was adopted to effectively reduce the loss in resistance along with reducing the number of bends or increasing the radius of bend curvature.The maximum velocity ratio and velocity offset values could quantitatively characterize the influences of different pipeline layouts on the resistance.The correlation reached 96%.Particle distribution and interparticle forces affected flow resistance.Uniform particle states and weak interparticle forces were conducive to steady transport.Pulse pump pressure led to high flow resistance.It could improve pipe flow stability by increasing flow uniformity and particle motion stability.These results can contribute to safe and efficient paste filling.

Investigation of Micro Formability of Bulk Amorphous Alloy in the Supercooled Liquid State Based on Fluid Flow and Finite Element Analysis

Research results on the viscous flow deformation behavior of bulk amorphous alloy in different systems are reviewed. The material exhibits an ideal Newtonian fluid at a high temperature. Analytical solution of lamellar fluid flow behavior is used to discuss the viscous flow behavior of the bulk amorphous alloy in the supercooled liquid state. A material model, which describes such deformation behavior of Mg6oCusoYlo amorphous alloy, is introduced into the finite element method of microformin8 process. Surface feature size was investigated and found not sensitive to the micro formability. Bulk amorphous alloy may possibly be applied to microelectro-mechanical-systems （MEMS） fabrication.

Cold-state Experimental Study on Flow Characteristics of Multi-nozzle in Natural Gas Reburning Burner

Based on the prototypes of a 130 t/h boiler, constant proportional cold-state test bench is established, flow characteristics of multi-nozzle in natural gas reburning burner and its influence on the covering effect for the upflow in the furnace are researched. Numerical simulations of this process are also made with standard ?turbulence model. The results show that air flow fullness in furnace is better in the case of the reburning zone with 8 nozzles compared to 4 nozzles and also coverage effect of the reburning flow for the updraft gas in the furnace is better. In the condition each nozzle airflow velocity is constant, the effect of reburning flow on coverage of up-secondary air is best when the incident angle for four corners is 14.17?, while Center of the furnace wall is 84.57. And while the best incident angle is invariable, the effect of reburning flow on coverage of up-secondary air is best when the speed of reburning gas in the corners of furnace is 51 m/s, the same to the center of the furnace wall’s.

Dynamic Load Flow Used for Electric Power System State and Tendency Analysis

Dynamic load flow technology can simulate actual frequency and load flow change when a load naturally varies and generator units adjust their power output by an adjustment system during a certain time. Dynamic load flow is a basic part of power system state and tendency analysis. In this paper, a dynamic load flow model and its solution method are first presented and discussed. Then, the application of dynamic load flow to a real power system is given as a demonstration.

Impact of Typical Steady-state Conditions and Transient Conditions on Flow Ripple and Its Test Accuracy for Axial Piston Pump

The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ~6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test accuracy of flow ripple is above 93.07%. The model constructed in this research proposes a method to determine the flow ripple characteristics of pump and its attainable test accuracy under the large-scale and time-variant working conditions. Meanwhile, a discussion about the variation of flow ripple and its obtainable test accuracy with the conditions of the pump working in wide operating ranges is given as well.

Numerical method of the Riemann problem for two-dimensional multi-fluid flows with general equation of state

Based on the classical Roe method, we develop an interface capture method according to the general equation of state, and extend the single-fluid Roe method to the two-dimensional （2D） multi-fluid flows, as well as construct the continuous Roe matrix for the whole flow field. The interface capture equations and fluid dynamic conservative equations are coupled together and solved by using any high-resolution schemes that usually suit for the single-fluid flows. Some numerical examples are given to illustrate the solution of 1D and 2D multi-fluid Riemann problems.

比例伺服阀非线性液动力模型修正与特性分析

比例伺服阀的高速运行以及油液流动状态直接影响液动力的变化,进而影响比例伺服阀和伺服机构的动静态性能。基于此,为明确比例伺服阀液动力的变化规律和特性,首先基于阀芯和阀体配合的节流口结构建立液动力的理论数学模型。然后结合流场仿真,分析不同开度和不同压差下液动力变化情况,明确液动力仿真结果和理论结果的偏差,修订液动力理论数学模型。最后,基于液动力测试平台,验证了不同开度和压差下液动力变化情况。结果表明:射流角的减小会导致稳态液动力不断增大,阀口开度的增大使稳态液动力呈现先增大后减小的趋势,同时在小开度下压差越大对应稳态液动力的峰值也越大,研究成果为比例伺服阀非线性补偿控制提供理论基础。

煤层气水平井筒倾斜-水平耦合流动规律影响分析

精确掌握煤层气水平井井筒内气液流动规律,对煤层气水平井的合理开发工艺和设备的选择具有重要意义。基于气液两相流理论采用Fluent软件模拟分析的方法,研究了煤层气水平井段倾斜-水平耦合条件下变状态流动规律。分析结果表明:水平段井筒中,上倾斜段井筒内的流动会加剧井筒内气液两相界面的波动。高气、液量下水平段井筒内持液率在流体流动方向上不断增大,低气、液量下水平段井筒内持液率在流体流动方向上不断减小。上倾段倾斜角小于20°时,倾斜角对水平段平均持液率影响较大;下水平段井筒中,倾斜段井筒的长度和倾斜角会影响水平井筒中假想断面的位置,同一流动条件下,出口上倾井筒的倾斜角越大、长度越大,假想断面位置越远离出口端上倾井筒。研究结果可为煤层气水平井下泵深度等排采工艺设计和优选提供理论依据。

泵站进水系统三维水动力特性数值模拟研究

【目的】研究泵站进水系统结构对水泵进水流场的影响。【方法】基于Fluent平台,假定水流为不可压缩湍流流体,在满足连续方程和动量方程的基础上,引入RNGk-ε紊流模型,对改造前后泵站进水系统进行了数值模拟,采用适于稳态流场的收敛速度更快的SIMPLEC算法,利用有限体积法进行空间离散求解,分析了不同断面的流场流速、流速旋角及流线分布,对比分析了改造前后泵站进水系统的水动力指标。【结果】改造方案各水动力指标均小于改造前方案,进水池流速标准差减小了6%~64%,进水管进口流速标准差降低了41%~96%,平均流速旋角减小了60%~73%,流速旋角标准差降低了59%~72%,水流流态分布趋向均匀,水泵进水条件明显改善。【结论】改造后泵站进水系统流速分布较均匀,流态趋于平稳,对减轻泵站机组汽蚀破坏有重要意义。

高海况下客滚船风浪阻力和功率航速预报

高海况下风浪阻力对客滚船航速预报的准确性有很大影响。对此,以某型客滚船为例,分别采用二维方法和三维方法预报船舶升沉和纵摇运动,采用全浪向波浪增阻预报方法SNNM计算波浪增阻,在此基础上开展高海况下的功率航速预报,并与模型试验结果进行对比分析。研究表明:当航速较低时,采用二维方法与三维方法预报的升沉运动结果的精度接近,随着速度的增加,二者的差异变大;当航速较高时,采用三维方法预报的纵摇结果比试验结果大,采用二维方法预报的纵摇结果比试验结果小;长波范围内采用SNNM方法预报的波浪增阻偏小,当谱峰周期为7 s和9 s时,采用SNNM方法近似预报的功率与试验值较为接近,但当谱峰周期变大时,近似预报结果偏小;整体来看,采用SNNM方法得到的航速预报值比试验值大。

穿越层状多孔介质的非达西渗流特征研究

穿越层状多孔介质的非达西渗流多见于人类活动影响下的土壤-地下水系统中。采用自行开发设计的室内渗流实验装置,设置不同粒径的单层多孔介质和相应粒径组合的双层多孔介质,从水力坡降与渗流流速关系、非达西渗流参数和临界雷诺数等方面,探讨了平均粒径、粗细颗粒界面对穿越层状多孔介质非达西渗流特征的影响规律。结果表明:当水流穿越层状多孔介质时,粗细颗粒界面对非达西流渗流特征具有重要影响;作为判断达西流态到非达西流态转换的临界雷诺数,其在单层多孔介质中随多孔介质平均粒径的增大而减小,而当水流穿越层状多孔介质时,临界雷诺数不仅随平均粒径的增大而增大,而且随粗/细颗粒粒径差的减小而增大;受粗细颗粒界面的影响,单层多孔介质中临界雷诺数均低于粗颗粒层与单层多孔介质相同相应粒径组合的双层多孔介质;通过引入非线性分量指数发现,粗细颗粒界面对水流惯性力分量的影响具有一定抑制作用,其抑制性影响程度与粗细颗粒差别大小呈负相关。研究结果对研究穿越层状岩土体的非达西渗流问题具有较好的指导意义。

Determination of Curie Point Depth, Heat Flow and Geothermal Gradient from High Resolution Aeromagnetic Data around Lamurde Area, Adamawa State, North-Eastern Nigeria

Analysis of high resolution of aeromagnetic data was carried out over Lamurde, Adamawa state north-eastern Nigeria to determine the Curie point depth (CPD), heat flow and geothermal gradient. The aeromagnetic data used for this work was obtained at Nigerian geological survey agency, the total magnetic intensity was processed to produce the residual magnetic map which was divided into 4 overlapping blocks, each block was subjected to spectral analyses to obtain depths to the top boundary and centroid, while depth to bottom of the magnetic sources was calculated using empirical formula. The depths values obtained were then used to assess the CPD, heat flow and geothermal gradient in the area. The result shows that the CPD varies between 9.62 and 10.92 km with an average of 10.45 k, the heat flow varies between 150.73 and 132.78 mWm−20⋅°C−1 with an average of 139.12 mWm−20⋅°C−1 and the geothermal gradient in the study area varies between 12.16 and 15.67 °C/km with an average of 13.39 °C/km. In view of the above results, the high heat flow may be responsible for maturation of hydrocarbon in Benue Trough as well as responsible for the lead Zinc Mineralization. Again by implication, Lamurde area can be a good area for geothermal reservoir exploration for an alternative source for power generation.

基于轨迹数据的快速路交织区拥堵演变特征研究

对快速路交织区拥堵演变过程中宏观交通流参数与交通状态的时变关系进行研究,可以为快速路交织区交通状态判别提供科学依据。利用YOLO算法从高清视频中提取车辆轨迹数据后,利用卡尔曼滤波对原始轨迹数据进行降噪平滑处理;对快速路交织区拥堵演变过程中速度、流量、密度等宏观交通流参数与交通状态进行时变分析,揭示快速路交织区宏观交通流参数在拥堵演变过程中的时变特征。结果表明,在快速路交织区交通状态判别时,融合平均行程速度和交通流密度等指标,可以有效提高交通状态判别精度。