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Robust adaptive backstepping control for a class of uncertain nonlinear systems based on disturbance observers

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Science china(Information Sciences) 2010年第6期53卷 1201-1215页

作者： MEI Rong 1,2, WU QingXian 1 & JIANG ChangSheng 1 1 Automation college, nanjing university of aeronautics and astronautics, nanjing 210016, china 2 Criminal Investigation Department, nanjing Forest Police college, nanjing 210042, china 1. Automation college Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. Criminal Investigation Department Nanjing Forest Police College Nanjing 210042 China

In this paper, a novel robust adaptive control scheme for a class of uncertain nonlinear systems is proposed using disturbance observer and backstepping ***, a disturbance observer is developed using radial basis function(RBF) neural *** parameter updated law of the RBF neural network is given for monitoring subsystem disturbance *** robust adaptive control scheme is then presented with backstepping method based on the designed disturbance *** uniform ultimate boundedness(SGUUB) of all signals in the closed-loop uncertain nonlinear system is *** closed-loop system stability analysis shows that semiglobal uniform boundedness of all signals is guaranteed by appropriately choosing design ***, two examples are taken to illustrate the effectiveness of the proposed control scheme.

关键词： uncertain nonlinear systems disturbance observer RBF neural network backstepping control robust adaptive control

Online-SVR-compensated nonlinear generalized predictive control for hypersonic vehicles

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Science china(Information Sciences) 2011年第3期54卷 551-562页

作者： CHENG Lu , JIANG Chang Sheng & PU Ming college of Automation Engineering, nanjing university of aeronautics and astronautics, nanjing 210016, china 1. college of Automation Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

This paper is concerned with the problem of hypersonic vehicle (HSV) attitude control system in uncertain flight conditions. The problem can be expressed as the adaptive robust control for a class of uncertain nonlinear systems. Based on the description of the aerodynamic structure and the model of flight control system of a certain kind of HSV, the ideal nonlinear generalized predictive control (NGPC) law based on uncertain nonlinear model is raised first to optimize the receding-horizon criterion of tracking errors. Then the online support vector regression (SVR) is employed to identify the uncertain item in the ideal control law. It is the compensating part of the controller. In addition, the stability of the close-loop system is analyzed using the Lyapunov method. The developed control strategy is well-implemented in this HSV attitude control system, and the simulation results compared with both nominal NGPC and RBF neural network disturbance observer show the good robustness and disturbance attenuation ability of this strategy and demonstrate the efficiency of online SVR algorithm.

关键词： hypersonic vehicle flight control nonlinear generalized predictive control online support vector regression

Preparation and characterization of nanostructured Al_2O_3-13wt.%TiO_2 ceramic coatings by plasma spraying

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Rare Metals 2009年第5期28卷 465-470页

作者： WANG Dongsheng TIAN Zongjun SHEN Lida LIU Zhidong HUANG Yinhui jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China college of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions （a three-dimensional net or skeleton-like structure： Al2O3-rich submicron particles embedded in the TiO2-rich matrix） and solid-phase sintered regions （remained nanoparticles）. The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO2 nanoparticles during plasma spraying. On the other hand, the TiO2 and Al2O3 nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.

关键词： surface coating nanostructured coating plasma spraying microstructure microhardness wear resistance

Influence of MgO-type Expansive Agent Hydration Behaviors on Expansive Properties of Concrete

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Journal of Wuhan university of Technology(Materials Science) 2011年第2期26卷 345-347页

作者：卢小琳 college of Materials Science and Technology Nanjing University of Aeronautics & Astronautics

The hydration behaviors and expansive properties of MgO-type expansive agent curing at different temperatures and environment were *** the curing temperatures changed from 25. to 5.℃,the conductivities of MgO samples increased from 40 to 80 μs/cm,and the hydrations of MgO were quickened up *** SEM observation,the hydration product of MgO cured at 5.℃ for 28 day was about 2-3μm in *** expansion of pastes with 5. of the MgO-type expansive agent was from 0.36% to 1.01% when the curing temperature changed from 25.C to 5.℃.When 8% of the MgO-type expansive agent was added,the early shrinkage of concrete was *** expansion ratio increased with the curing temperature,and the expansive cracking of concrete with MgO-type expansive agent might be decreased by blending fly ash.

关键词： concrete expansive agent expansion hydration conductivity

Theoretical Model of Transformation Superlastic Diffusion Bonding for Eutectoid Steel

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厦门大学学报（自然科学版） 2002年第S1期41卷 13-14页

作者： LU Shi-hong, YUN Jun-bi (college of Mechanic and Electricial Engineering, nanjing university of aeronautics & astronautics, nanjing 210016, china)

Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is mainly described as two-stage process: Ⅰ The interfacial cavity with shape change from diamond to cylinder.Ⅱ The radius of the cylindrical cavity are reduced and eliminated gradually. A new theoretical model is established for the process of transformation superplastic diffusion bonding (TSDB) on the basis of a theoretical model for isothermal superplastic diffusion. The model can predict the bonding quality which is affected by technological parameters, such as limit cycling temperature, the compressive stress, the numbers of thermal cycles and temperature cycling through the phase transformation in the thermal cycling and so on. Results show that the maximum temperature, the compressive stress, the numbers of thermal cycles and the rate of temperature changing speed in the thermal cycling have an important influence on TSDB process. Meanwhile, reasonable technological parameters chosen from theoretical analysis is in good agreement with those obtained from experimental results.

关键词： TSDB eutectoid steel phase transformation superplasticity diffusion bonding theoretical model

Research on Knowledge-based Connecting Elements Modeling

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厦门大学学报（自然科学版） 2002年第S1期41卷 162-163页

作者： HUANG Xiang, YAN Chong-jing (college of Mechanical and Electrical Engineering, nanjing university o f aeronautics and astronautics, nanjing 210016, china)

Steps of manipulation is required to complete the m od eling of the connection elements such as bolt, pin and the like in commerce CAD system. It leads to low efficiency, difficulty to assure the relative position, impossibility to express rules and knowledge. Based on the inner character analy sis of interpart, detail modification and assembly relation of mechanical connec ting element, the idea, which extends the feature modeling of part to the interp art feature modeling for assembly purpose, is presented, and virtual part based connecting element modeling is proposed. Virtual part is a complement set of lo cal modification of part to be connected. In assembly modeling, base part is mod ified by Boolean operation between base part and virtual part. The modeling and assembly is finished just in one operation, at the same time the rules and knowl edge of the connection elements are encapsulated through virtual part. According to this mechanism, a knowledge-based connecting elements rapid design module i s developed on commerce software package UG with satisfying results.

关键词： CAD knowledge-based engineering assembly conn ecting element

Photocatalytic activity of porous TiO_2 films prepared by anodic oxidation

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Rare Metals 2007年第2期26卷 136-141页

作者： WANG Wei TAO Jie WANG Tao WANG Ling college of Material Science ＆ Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Anatase titanium dioxide is an active photocatalyst, however, it is difficult to be immobilized on the substrate. The crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation. The film was then used for photocatalysis via the methyl orange degradation method. The effects of anodization voltage, pH value, TiO2 film area and degradation time on the photocatalyst were investigated respectively by UV-visible spectrum. It was indicated that the TiO2 film prepared by anodic oxidation at 140 V had the best photocatalysis capability and the degradation of methyl orange was accelerated with acid addition.

关键词： titanium porous films anodic oxidation photocatalysis methyl orange

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高低温环境下摩擦系数的高准确度测试

数据采集与处理 2004年第1期19卷 111-114页

作者：吴惠祥杨忠毛万华南京航空航天大学航空宇航学院南京210016 南京航空航天大学自动化学院南京210016 南京航空航天大学理学院南京210016

在航空要求的高低温环境下 (-5.5. +1 2 5. ) ,为实现摩擦系数与接触电阻的高准确度测试 ,本文研制了适合于在高低温环境下测试摩擦件摩擦系数与接触电阻的测试试验台。通过对试验件载荷和摩擦力矩的测量 ,测量出试验件在不同温度及... 详细信息

在航空要求的高低温环境下 (-5.5. +1 2 5. ) ,为实现摩擦系数与接触电阻的高准确度测试 ,本文研制了适合于在高低温环境下测试摩擦件摩擦系数与接触电阻的测试试验台。通过对试验件载荷和摩擦力矩的测量 ,测量出试验件在不同温度及不同载荷下的摩擦系数与接触电阻 ,用试验及曲线拟合方法研究并解决了力传感器的温度补偿问题。为提高测试精度 ,对测试系统的硬件和软件进行了抗干扰优化设计 ,通过对某航空产品的试验 ,数据显示测试台的测试精度达 4%。

关键词：机械零部件摩擦系数高准确度测试接触电阻

Vibrations in High Speed Milling of Thin-walled Components

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武汉理工大学学报 2006年第S3期28卷 824-827页

作者： WANG Tongyue~(1,2) HE Ning~2 LI Liang~2 (1.Departrnent of Mechanical Engineering,Huaiyin Institute of Techunology,Huaian 223001,china, 2.college of Mechanical & electrical Engineering,nanjing university of aeronautics and {5.,nanjing 210016,china) Department of Mechanical Engineering Huaiyin Institute of TechnologyHuaian 223001China college of Mechanical & electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China college of Mechanical & electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Thin-walled structures have been widely used in the aerospace *** dynamic interaction between the milling cutter and thin-walled workpiece can easily lead to *** paper investigates the vibration caused during milling the thin-walled workpiece on the NC machining center,presents a theoretical milling vibration model of thin-walled *** model was verified by using milling experiments and numerical *** valuable conclusions are derived,this will be references to scientific research and guides to the vibration-free milling of thin-walled structures at different cutting speeds.

关键词： thin-walled components vibration simulation cutting parameters