Nominal Model-Based Sliding Mode Control with Backstepping for 3-Axis Flight Table

Based on nominal model, a novel global sliding mode controller （GSMC） with a new control scheme is proposed for a practical uncertain servo system. This control scheme consists of two combined controllers, One is the global sliding mode controller for practical plant, the other is the integral backstepping controller for nominal model. Modeling error between practical plant and nominal model is used to design GSMC. The steady-state control accuracy can be guaranteed by the integral backstepping control law, and the global robustness can be obtained by GSMC. The stability of the proposed controller is proved according to the Lyapunov approach. The simulation results both of sine signal and step signal tracking for 3-axis flight table are investigated to show good position tracking performance and high robustness with respect to large and parameter changes over all the response time.

Stiffness of Postural Alignment System Based on 3-Axis Actuators for Large Aircraft Components

Aircraft digital flexible assembly fixture and technologies are widely used in developed countries, while the traditional jig-based assembly mode is still used in China. The application study of aircraft digital flexible assembly system is just beginning in our country recently. To meet the requirements of automated posture alignment and join in digital assembly system for large aircraft components, a novel fitting fixture called 3-axis actuator is developed. On the basis of the actuators, three kinds of posture alignment system for large aircraft components are proposed, including the non-redundant system, the redundant actuating system, and the redundant leg system, and their constitutions and properties are introduced. Through deriving the feeding transmission stiffness model of single actuator and analyzing the inverse kinematics of these systems, the relationship between the external force and the changes of position and orientation of large aircraft component is obtained, and then the postural alignment stiffness models are established. With the method mentioned above, the postural alignment stiffness of three systems is computed by using the algebraic formulate, and the results show that redundant properties can increase system＇s postural alignment stiffness. As an example, a optimized layout of the assembly system for a given model of aircraft is developed, the results of application show that the layout has many advantages, such as high accuracy, stiffness, stability, reliability, efficiency and flexible, which can satisfy the requirement of aircraft digital assembly system well. The proposed study of postural alignment stiffness for different systems can supply the theoretic support for the optimization layout design of aircraft digital assembly system, and contribute to evaluate the system working performance of systems.

QFT Robust Control Design for 3-Axis Flight Table Servo System with Large Friction

The 3-axis flight table is an important device and a typical high performanceposition and speed servo system used in the hardware-in-the-loop simulation of flight controlsystem. Friction force and uncertainty are the main characteristics in the 3-axis flight table servosystem. Based on the description of dynamic and static model of a nonlinear Stribeck frictionmodel, and taking account of the practical uncertainties of 3-axis flight table servo system, theQFT controller is designed. Simulation and realtime results are presented.

A 3D Simulator for Autonomous Robotic Fish

This paper presents a 3D simulator used for studying the motion control and autonomous navigation of robotic fish. The simulator’s system structure and computation flow are presented. Simplified kinematics and hydrodynamics models for a virtual robotic fish are proposed. Many other object models are created for water, obstacles, sonar sensors and a swimming pool. Experimental results show that the simulator provides a realistic and convenient way to develop autonomous navigation algorithms for robotic fish.

Geant4 simulation of fast-electron bremsstrahlung imaging at the HL-3 tokamak

To further research on high-parameter plasma,we plan to develop a two-dimensional hard X-ray(HXR)imaging system at the HL-3 tokamak to measure HXRs with energies ranging from 20 to 300 keV.The application of an array-structured detector ensures that this system can measure HXR-radiation spectra from the entire plasma cross section.Therefore,it is suitable for the study of fast-electron physics,such as radio-frequency wave current drives,fast electrons driving instabilities,and plasma disruptions in fusion research.In this study,we develop a simulation for calculating fast-electron bremsstrahlung in the HL-3 tokamak based on the Monte Carlo simulation code Geant4,in which the plasma geometry and forward scattering of fast-electron bremsstrahlung are considered.The preliminary calculation results indicate that the HXR energy deposi-tion on the detector is symmetrically distributed,even though the plasma distribution is asymmetric owing to the toroidal effect.These simulation results are helpful in constructing the relationship between the energy deposition on the detector and parameter distribution on the plasma cross section during HL-3 experiments.This is beneficial for the reconstruction of the fast-electron-distribution function and for optimizing the design of the HXR-imaging system.

Ru团簇对Ni/Ni_(3)Al合金纳米线形变影响的原子模拟

镍基高温合金是制造先进航空发动机热端部件的关键材料之一,其高温力学性能直接关系到发动机运行安全和使用寿命.本文采用改进分析型嵌入原子模型(MAEAM)和分子动力学(MD)研究合金化元素钌(Ru)团簇对Ni/Ni_(3)Al纳米线形变机制的影响,结果表明:在单轴拉伸应变下,纳米线的弹性模量和屈服强度随温度升高而降低.温度较低时,纳米线形变由位错产生与发射而导致晶格滑移所引起.由于晶格热振动非谐效应不明显,Ru团簇阻碍效果显著,使得晶格滑移区域仅限于Ru团簇与Ni/Ni_(3)Al相界面之间且呈非对称分布.温度较高时,纳米线的形变由位错发射而引起晶格滑移所致,但因非谐效应显著,Ru团簇无法阻碍位错运动,滑移区域在Ru团簇周围对称分布于Ni_(3)Al相中.最后从Ru团簇微观结构及其稳定性的角度进一步分析其对纳米线形变影响.

Molecular dynamics simulation of relationship between local structure and dynamics during glass transition of Mg_7Zn_3 alloy

The rapid solidification process of Mg7Zn3 alloy was simulated by the molecular dynamics method. The relationship between the local structure and the dynamics during the liquid-glass transition was deeply investigated. It was found that the Mg-centered FK polyhedron and the Zn-centered icosahedron play a critical role in the formation of Mg7Zn3 metallic glass. The self-diffusion coefficients of Mg and Zn atoms deviate from the Arrhenius law near the melting temperature and then satisfy the power law. According to the time correlation functions of mean-square displacement, incoherent intermediate scattering function and non-Gaussian parameter, it was found that the β-relaxation in Mg7Zn3 supercooled liquid becomes more and more evident with decreasing temperature, and the α-relaxation time rapidly increases in the VFT law. Moreover, the smaller Zn atom has a faster relaxation behavior than the Mg atom. Some local atomic structures with short-range order have lower mobility, and they play a critical role in the appearance of cage effect in theβ-relaxation regime. The dynamics deviates from the Arrhenius law just at the temperature as the number of local atomic structures begins to rapidly increase. The dynamic glass transition temperature （Tc） is close to the glass transition point in structure （TgStr）.

Material driven workability simulation by FEM including 3D processing maps for magnesium alloy

The three-dimensional （3D） processing maps considering strain based on the two-dimensional （2D） processing maps proposed by PRASAD can describe the distribution of the efficiency of power dissipation and flow instability regions at various temperatures, strain rates and strains, which exhibit intrinsic workability related to material itself. Finite element （FE） simulation can obtain the distribution of strain, strain rate, temperature and die filling status, which indicates state-of-stress （SOS） workability decided by die shape and different processing conditions. On the basis of this, a new material driven analysis method for hot deformation was put forward by the combination of FE simulation with 3D processing maps, which can demonstrate material workability of the entire hot deformation process including SOS workability and intrinsic workability. The hot forging process for hard-to-work metal magnesium alloy was studied, and the 3D thermomechanical FE simulation including 3D processing maps of complex hot forging spur bevel gear was first conducted. The hot forging experiments were carried out. The results show that the new method is reasonable and suitable to determine the aoorooriate nrocess narameters.

3-D Simulation of FINFET

An SOI MOSFET with FINFET structure is simulated using a 3 D simulator. I V characteristics and sub threshold characteristics,as well as the short channel effect(SCE) are carefully investigated.SCE can be well controlled by reducing fin height.Good performance can be achieved with thin height,so fin height is considered as a key parameter in device design.Simulation results show that FINFETs present performance superior to conventional single gate devices.

CASMO-4E/SIMULATE-3程序系统计算BEAVRS基准题

BEAVRS基准题是麻省理工学院计算反应堆物理小组2013年公布的压水堆三维全堆芯高保真计算基准题。本文使用传统两步法程序系统CASMO-4E/SIMULATE-3对其进行建模与跟踪计算。结果表明:在热态零功率(HZP)工况下,径向探测器反应率最大相对误差为-18.8%,与蒙特卡罗程序MC21程序的-16.1%相当;在燃耗深度为38.7 MW·d/tHM、堆芯功率为20.3%FP时,径向探测器反应率最大相对误差为-12.9%;在堆芯第1循环内,堆芯各燃耗点处临界硼浓度与测量值误差在40ppm以内,满足工程精度要求。

Simulating leaf net CO_2 assimilation rate of C_3 & C_4 plants and its response to environmental factors

Basic structure and algorithm of leaf mechanism photosynthesis model were described in first part of this study based on former researcher results. Then, considering some environmental factors influencing on leaf photosynthesis, three numerical sensitivity experiments were carried out. We simulated the sing le leaf net CO2 assimilation, which acts as a function of different light, carbo n dioxide and temperature conditions. The relationships between leaf net photosy nthetic rate of C3 and C4 plant with CO2 concentration intercellular, leaf tempe rature, and photosynthetic active radiation (PAR) were presented, respectively. The results show the numerical experiment may indicate the main characteristic o f plant photosynthesis in C3 and C4 plant, and further can be used to integrate with the regional climate model and act as land surface process scheme, and bett er understand the interaction between vegetation and atmosphere.

Using 3D TCAD Simulation to Study Charge Collection of a p-n Junction in a 0.18μm Bulk Process

Single event transient of a real p-n junction in a 0.18μm bulk process is studied by 3D TCAD simulation. The impact of voltage, temperature, substrate concentration, and LET on SET is studied. Our simulation results demonstrate that biases in the range 1.62 to 1.98V influence DSET current shape greatly and total collected charge weakly. Peak current and charge collection within 2ns decreases as temperature increases,and temperature has a stronger influence on SET currents than on total charge. Typical variation of substrate concentration in modern VDSM processes has a negligible effect on SEEs. Both peak current and total collection charge increases as LET increases.

基于SolidWorks Simulation的3D打印机机体静力学分析

近年来,3D打印机作为一种高效率的成型设备被广泛的使用,然而,其高速性、高精度与高可靠性与其机体的轻量化设计存在一定的矛盾关系。通过SolidWorks软件对3D打印机机体进行轻量化设计,并使用集成的Simulation仿真软件对设计模型进行快速静态力学分析,参照仿真结果对轻量化设计的模型进行验证与优化。通过集成化的三维建模软件和仿真软件,实现了3D打印机的模型设计和模型力学分析,验证了3D打印机设计的合理性和可靠性,为3D打印机的轻量化设计提供理论指导和修改建议,节省设备的研发周期和研发成本。

Simulating leaf net CO2 assimilation rate of C3 & C4 plants and its response to environmental factors

Basic structure and algorithm of leaf mechanism photosynthesis model were described in first part of this study based on former researcher results. Then, considering some environmental factors influencing on leaf photosynthesis, three numerical sensitivity experiments were carried out. We simulated the sing le leaf net CO2 assimilation, which acts as a function of different light, carbo n dioxide and temperature conditions. The relationships between leaf net photosy nthetic rate of C3 and C4 plant with CO2 concentration intercellular, leaf tempe rature, and photosynthetic active radiation (PAR) were presented, respectively. The results show the numerical experiment may indicate the main characteristic o f plant photosynthesis in C3 and C4 plant, and further can be used to integrate with the regional climate model and act as land surface process scheme, and bett er understand the interaction between vegetation and atmosphere.

基于FASnI_(3)的钙钛矿太阳电池仿真研究

为提高电池的效率、减少环境污染,提出一种结构为FTO/Zn(O_(0.3),S_(0.7))/FASnI_(3)/NiO/Au的无铅钙钛矿太阳电池。该电池以FASnI_(3)为光活性层,Zn(O_(0.3),S_(0.7))和NiO分别为电子传输层和空穴传输层,FTO和Au为接触电极。在太阳电池电容模拟器(SCAPS)中构建模型并设置材料参数,通过控制变量法进行参数优化。结果表明,当FASnI_(3)厚度为500 nm时,器件对光子的吸收较充分,输出最高的功率转换效率(PCE);随着FASnI_(3)缺陷态密度的升高,器件内部载流子复合中心增多,提高了载流子复合率,控制FASnI_(3)缺陷态密度不超过10^(14) cm^(-3)可确保电池输出性能较佳;当Zn(O_(0.3),S_(0.7))的厚度和电子亲和势优化为30 nm和3.5 eV时,载流子运输更为有效,电池输出最高的PCE;增大Zn(O_(0.3),S_(0.7))与FASnI_(3)界面缺陷态密度,导致光生载流子在界面更容易被捕获,控制Zn(O_(0.3),S_(0.7))与FASnI_(3)界面缺陷态密度不超过10^(13) cm^(-3)有利于提高电池性能。

Fe-3%Si合金薄带连铸板热处理过程层状异构组织演变的相场模拟研究

本研究基于Fe-3%Si合金铸轧板材组织特征,构建了不同类型柱状晶/等轴晶层状异构组织相场模型,实现了界面曲率为驱动力的情况下层状异构组织的高温粗化过程模拟,量化分析了层状异构特征对铸轧组织演化过程的影响规律。研究表明,由于晶粒长径比对晶粒尖端曲率的影响,当初始状态下柱状晶长径比较高时,在界面曲率的驱动下最终会形成等轴化的多晶组织;反之则等轴化程度减小。明确了不同类型异构组织演化特征,相同退火时间下组织的等轴化程度受其层状异构特征的影响,这一现象的本质是等轴晶通过自身演化引起柱状晶两端曲率变化,诱发柱状晶间的相互“吞噬”并发生等轴化,柱状晶则在部分结构的组织中生长至带钢表面后停止生长,最终保持柱状特征。本研究进一步加深了对铸态薄带中初始凝固组织在后续热处理时演化过程的认识,对硅钢制备工艺优化具有重要的理论指导意义和实际应用价值。

Simulation of 1,3-Butadiene Production Process by Dimethylfomamide Extractive Distillation

Nowadays, extractive distillation is the main technique to produce 1,3-butadiene. This study simulated the 1,3-butadiene production process with DMF extractive distillation by Aspen Plus. The solvent ratio is the most important parameter to the extractive distillation process. The article has given out the proper solvent ratios, reflux ratios, distillate ratios, and bottom product ratios of the columns. It also discusses the thermal loads of several columns. The results of simulation are consequently compared with the plant data, which shows good accordance with each other.

Numerical simulation of 3D-microstructures in solidification processes based on the CAFE method

It was analyzed that the finite element-cellular automaton （CAFE） method was used to simulate 3D-microstructures in solidification processes. Based on this method, the 3D-microstructure of 9SMn28 free-cutting steel was simulated in solidification processes and the simulation results are consistent with the experimental ones. In addition, the effects of Gaussian distribution parameters were also studied. The simulation results show that the higher the mean undercooling, the larger the columnar dendrite zones, and the larger the maximum nucleation density, the smaller the size of grains. The larger the standard deviation, the less the number of minimum grains is. However, the uniformity degree decreases first, and then increases gradually.

Numerical simulation of a combined oxidation ditch flow using 3D k-ε turbulence model

The standard three dimensional（3D） k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.

Surface Air Temperature Simulations over China with CMIP5 and CMIP3

Historical simulations of annual mean surface air temperature over China with 25 CMIP5 models were assessed.The observational data from CRUT3v and CN05 were used and further compared with historical simulations of CMIP3.The results show that CMIP5 models were able to simulate the observed warming over China from 1906 to 2005(0.84 C per 100 years)with a warming rate of 0.77 C per 100 years based on the multi-model ensemble(MME).The simulations of surface air temperature in the late 20th century were much better than those in the early 20th century,when only two models could reproduce the extreme warming in the 1940s.The simulations for the spatial distribution of the 20-yearmean(1986–2005)surface air temperature over China fit relatively well with the observations.However,underestimations in surface air temperature climatology were still found almost all over China,and the largest cold bias and simulation uncertainty were found in western China.On sub-regional scale,northern China experienced stronger warming than southern China during 1961–1999,for which the CMIP5 MME provided better simulations.With CMIP5 the diference of warming trends in northern and southern China was underestimated.In general,the CMIP5 simulations are obviously improved in comparison with the CMIP3 simulations in terms of the variation in regional mean surface air temperature,the spatial distribution of surface air temperature climatology and the linear trends in surface air temperature all over China.