装备保障机动模拟研究

装备保障机动模拟是装备指挥训练模拟系统开发中的内容之一;对作战情况下地面装备保障机动进行了描述,对装备保障机动模拟时的数据准备进行了归纳;提出了装备保障机动模拟的基本框架和处理流程,分析了各种因素对机动速度的影响;给出了速度修正流程框图.

一种有效的中性浮力下实验体姿态机动模拟控制律设计

在空间微重力环境的地面模拟技术中,中性浮力法利用水的浮力使实验体处于漂浮状态,可以提供六自由度运动模拟,并且可进行长时间的与空间十分相似的自由运动。因此可以采用该方法实现空间飞行器空间任务的地面模拟演示和功能验证。姿态控制作为空间任务的基本操作之一,其在中性浮力实验环境下的控制模拟非常重要,需要针对复杂的水下环境进行设计。目前针对水下航行器的研究非常广泛,但是专门针对中性浮力环境下空间任务模拟的研究并不多,缺少理论验证与仿真。本文针对中性浮力环境下实验体姿态机动模拟控制律设计问题进行研究。首先根据流体力学和动量矩定理推导出实验体的姿态动力学方程,根据四元数与角速度的关系得到实验体的姿态运动学方程;然后在理想状态下基于动力学方程,使用Lyapunov方法设计实验体的姿态机动模拟控制律,并证明了闭环系统的渐进稳定性;最后通过仿真验证了控制算法的性能,为中性浮力环境下实验体姿态机动模拟提供理论基础。

日本研制隐身／高机动飞行模拟装置

1996—1999年日本防卫厅与三菱重工签订20．38亿日元的合同，研究开发隐身／高机动飞行(失速后高机动飞行等)模拟装置。

飞机方案设计阶段机动载荷快速计算方法研究

提出了一种在方案阶段能快速准确预估飞机设计机动载荷的简捷计算方法。通过静气弹理论计算飞机的气动导数,以气动导数、操纵特性和质量特性为输入对飞机进行了机动模拟,得到各运动参数的时间历程,最后用涡格法计算出部件的分布载荷。将本文的计算结果与后续的传统方法计算结果进行比较,结果表明该方法是准确可靠的,能满足方案阶段飞机设计的载荷需求。该方法在方案阶段能有效克服传统方法需要大量的风洞试验得来的气动特性数据和压力分布数据的不足。本文的方法只需要较少的输入参数就可以进行,可在型号研制中节省时间,加快研制进度。

离心机模拟空战机动训练时飞行员的心律变化

目的 研究高性能战斗机飞行员进行模拟空战机动 (SACM )训练时心血管功能变化情况 ,从而提出保护措施。 方法 高性能战斗机飞行员 10名 ,在载人离心机上进行SACM训练。训练中 ,飞行员穿用抗荷服 ,做L 1抗荷动作及进行抗荷正压呼吸 (PBG) ;监视并记录心电图、耳脉搏和呼吸。 结果 10名飞行员在SACM时均发生不同程度的心律失常。心律失常以室性期前收缩为主 ,多发生于吸气末 ,4G以上的高G暴露中开始有心律失常发生 ,9G时发生率最高。心率增快程度和 +Gz 值呈正相关。在抗荷动作的吸气相 ,耳脉搏的幅值突然降低。 结论 SACM训练中 ,室性期前收缩多发 ,这可能为一种潜在性的危险。应训练飞行员正确掌握抗荷动作和PBG的实施要领 ,调控有氧体育锻炼强度 ,定期进行SACM训练 ,并实行心电图监控 。

Phase-field simulations of forced flow effect on dendritic growth perpendicular to flow

The effect of supercooled melt forced laminar flow at low Reynolds Number on dendritic growth perpendicular to melt flow direction was investigated with the phase-field method by incorporating melt convection and thermal noise under non-isothermal condition. By taking the dendritic growth of high pure succinonitrile （SCN） supercooled melt as an example, side-branching shape difference of melts with flow and without flow was analyzed. Relationships among supercooled melt inflow velocity, deflexion angle of dendritic arm and dendritic tip growth velocity were studied. Results show that the melt inflow velocity has few effects on the dendritic tip growth velocity. A formula of relationship between the velocity of the melt in front of primary dendritic tip and the dendritic growth time was deduced, and the calculated result was in quantitative agreement with the simulation result.

Photolithography Process Simulation for Integrated Circuits and Microelectromechanical System Fabrication

Simulations of photoresist etching,aerial image,exposure,and post-bake processes are integrated to obtain a photolithography process simulation for microelectromechanical system（MEMS） and integrated circuit（IC） fabrication based on three-dimensional （3D） cellular automata（CA）. The simulation results agree well with available experimental results. This indicates that the 3D dynamic CA model for the photoresist etching simulation and the 3D CA model for the post-bake simulation could be useful for the monolithic simulation of various lithography processes. This is determined to be useful for the device-sized fabrication process simulation of IC and MEMS.

Phase-field simulation of forced flow effect on random preferred growth direction of multiple grains

The random distribution problem of dendrite preferred growth direction was settled by random grid method.This method was used to study the influence of forced laminar flow effect on multiple grains during solidification.Taking high pure succinonitrile （SCN） undercooled melt as an example,the forced laminar flow effect on multiple grains was studied by phase-field model of single grain which coupled with flow equations at non-isothermal condition.The simulation results show that the random grid method can reasonably settle the problem of random distribution and is more effective.When the solid fraction is relatively low,melt particles flow around the downstream side of dendrite,and the flow velocity between two dendrite arms becomes high.At the stage of solidification time less than 1800Δt,every dendrite grows freely;the upstream dendrites are stronger than the downstream ones.The higher the melt flow rate,the higher the solid fraction.However,when the solid fraction is relatively high,the dendrite arm intertwins and only a little residual melt which is not encapsulated can flow;the solid fraction will gradually tend to equal to solid fraction of melt without flow.

飞行载荷临界情况筛选方法

1.引言一架飞机,从滑跑、起飞、爬升、巡航、直至下滑、着陆,无时不在承受着载荷。这些载荷主要分为二大类:一类为空气动力载荷;另一类则为惯性力载荷。决定载荷大小及分布的主要因素亦为二个方面:一为大气环境;二为飞机自身特性。

IMPROVED LANDING-GEAR DESIGN FOR FLEXIBLE AIRPLANE

Landing dynamic simulation and landing-gear optimization design are used to improve the landing-gear design for a flexible airplane. Landing response is simulated by using velocity-squared damping, polytropic exponential air-compression spring, tire force power function characteristics, and an equivalent three-mass system.Optimization of landing-gear parameters is performed considering the maximum displacement of the landing-gear shock stroke, the maximum landing-gear force and the maximum deformation of the wingtip in the landing impact. Resutls show that landing-gear design parameters have an important influence on the structural flexibility of the airplane. And the landing performance of the landing-gear can be improved by the optimized metering pin type landing-gear.

Research on the Dynamic Simulation System of Maize Growth

Dynamic simulation system of maize growth is developed by the physiological and ecological model,morphological structure model,computer science and virtual reality technology,to improve the level of precise operation of maize production.The computer graphics algorithms,virtual reality technology,animation design and information integration technology are applied to maize production by this system.establishment of dynamic simulation system of maize growth is conducive to raise level of precise operation in maize production.The system also can assist the relevant production research and testing,to reduce cost and improve efficiency.

基于模型的交叉路口公交站台NOx排放特性

为计算交叉口NOx排放量与排放因子的变化,并分析交叉口机动车尾气排放的规律,通过将机动车废气模拟系统(MOVES)排放模型与VISSIM交通仿真模型相结合的方法研究了NOx尾气排放特性,以及仿真分析交叉路口不同类型公交站台对机动车尾气排放情况的影响。结果表明:新型交叉路口比传统交叉路口NOx降低0.27 g。公交车在交叉口上游港湾式、下游港湾式与下游拓宽港湾式NOx实测数据是模型数据的1.14、1.28和1.24倍,在模拟实验中,NOx污染物在下游相同区域排放量降低15.07%,排放因子降低14.67%。可见通过交通模型对研究实际交叉路口公交站台NOx排放特性有实际意义。

Modeling of Hillslope Runoff and Soil Erosion at Rainfall Events Using Cellular Automata Approach

A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.

Dynamic simulation and experimental study of inspection robot for high-voltage transmission-line

A mobile robot developed by Wuhan University for full-path hotline inspection on 220 kV transmission lines was presented. With 4 rotating joints and 2 translational ones, such robot is capable of traveling along non- obstaclestraight-line segment and surmounting straight-line segment obstacles as well as transferring between two spans automatically. Lagrange’s equations were utilized to derive dynamic equations of all the links, including items of inertia, coupling inertia, Coriolis acceleration, centripetal acceleration and gravity. And a dynamic response experiment on elemental motions of robot prototype’s travelling along non-obstacle straight-line segment and surmounting obstacles was performed on 220 kV 1∶1 simulative overhanging transmission-line in laboratory. In addition, dynamic numerical simulation was conducted in the corresponding condition. Comparison and analysis on results of experiment and numerical simulation have validated theoretical model and simulation resolution. Therefore, the dynamic model formed hereunder can be used for the study of robot control.

Random vibration analysis of switching apparatus based on Monte Carlo method

The performance in vibration environment of switching apparatus containing mechanical contact is an important element when judging the apparatus’s reliability. A piecewise linear two-degrees-of-freedom mathematical model considering contact loss was built in this work, and the vibration performance of the model under random external Gaussian white noise excitation was investigated by using Monte Carlo simulation in Matlab/Simulink. Simulation showed that the spectral content and statistical characters of the contact force coincided strongly with reality. The random vibration character of the contact system was solved using time (numerical) domain simulation in this paper. Conclusions reached here are of great importance for reliability design of switching apparatus.

Dynamics and screening characteristics of a vibrating screen with variable elliptical trace

The ideal motion characteristics for the vibrating screen was presented according to the principle of screening process with constant bed thickness.A new vibrating screen with variable elliptical trace was proposed.An accurate mechanical model was constructed according to the required structural motion features.Applying multi-degree-of-freedom vibration theory,characteristics of the vibrating screen was analyzed.Kinematics parameters of the vibrating screen which motion traces were linear,circular or elliptical were obtained.The stable solutions of the dynamic equations gave the motions of the vibrating screen by means of computer simulations.Technological parameters,including amplitude,movement velocity and throwing index,of five specific points along the screen surface were gained by theoretical calculation.The results show that the traces of the new designed vibrating screen follow the ideal screening motion.The screening efficiency and processing capacity may thus be effectively improved.

Research on a Multi-grid Model for Passenger Evacuation in Ships

In order to enhance the authenticity and accuracy of passenger evacuation simulation in ships, a new multi-grid model was proposed on the basis of a traditional cellular automata model. In the new model finer lattices were used, interaction of force among pedestrians or between pedestrians and constructions was considered, and static floor fields in a multi-level exit environment were simplified into cabin and exit static floor fields. Compared with the traditional cellular automata model, the multi-grid model enhanced the continuity of the passengers'track and the precision of the boundary qualifications. The functions of the dislocation distribution of passengers as well as partial overlap of tracks due to congestion were realized. Furthermore, taking the typical cabin environment as an example, the two models were used to analyze passenger evacuation under the same conditions. It was found that the laws of passenger evacuation simulated by the two models are similar, while the simulation's authenticity and accuracy are enhanced by the multi-grid model.

Engine Multi-Body with Flexible Crankshaft Modeling and Numerical Simulation

A multi-body model of engine system with flexible crankshaft was presented in this paper to analyze the dynamic behavior of an internal combustion engine. The flexible crankshaft structural dynamics was coupled with the main beating hydrodynamic lubrication in this model by a system approach. An application of an 14 engine was given to show this sophisticated simulation model and to predict the loads and the orbit plots in the journal beatings by the dynamic response of the multi-body engine system with flexible crankshaft. The numerical results show the capabilities and significance of the flexible crankshaft in this system. The objective of the research is to provide the scientific guidance for design and maintenance of the internal combustion engine.

DYNAMIC MODEL AND SIMULATION OF A NOVEL ELECTRO-HYDRAULIC FULLY VARIABLE VALVE SYSTEM FOR FOUR-STROKE AUTOMOTIVE ENGINES

In modem four-stroke engine technology, variable valve timing and lift control offers potential benefits for making a high-performance engine. A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced. The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented. Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control. Consequently the engine performance on different loads and speeds will be significantly increased. The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.

Simulating the dynamics of fluid-cylinder interactions

We present the simulation of the dynamics of fluid-cylinder interactions in a narrow three-dimensional channel filled with a Newtonian fluid, using a Lagrange multiplier based fictitious domain methodology combined with a finite element method and an operator splitting technique. As expected, a settling truncated cylinder turns its broadside perpendicular to the main stream direction and the center of mass moves to the central axis of the channel. In the case of two truncated cylinders, they first move around each other for a while and then stay together in a "T" shape. After the "T" shape has been formed for a long enough time, we found no vortex shedding behind the cylinders. When simulating the fluidization of 60 truncated cylinders, we captured the features of interactions among fluidized cylinders as observed in experiments.