基于动态递归模糊神经网络的轧机辊缝动态辨识

模糊系统和神经网络,由于具有逼近任意连续非线性映射的特性,而广泛应用于系统的辨识与控制。但是传统的模糊神经网络是一种静态映射,不适用于动态系统的辨识,而轧制过程中影响轧机辊缝的因素复杂,外界干扰严重,过程参数难以确定,为提高轧机辊缝动态的辨识精度,提出了一种基于动态递归模糊神经网络的辨识模型。轧制仿真结果表明,该模型具有很高的辨识精度。     

基于多层前馈BP网络的非线性逆系统自学习控制

提出的基于神经网络的非线性逆系统自学习控制方案运用逆动力学的基本思想，在系统模型未知的情况下，构造了神经网络一致的控制器和辨识器。运用自适应变步长冲量BP学习算法实现了网络辨识器对系统逆动力学模型的动态辨识，并通过网络辨识器向网络控制器在线动态传递更新权值的方法使神经网络控制器产生期望控制量。使得整个神经网络控制系统具有了自学习、自适应的控制能力。     

电液伺服结构加载系统的神经网络直接自适应输出跟踪控制

本文利用神经网络的学习能力和非线性映射能力研究了电液加载系统的神经网络直接自适应输出跟踪控制方法，控制器是由一个具有反馈动力学的多层前馈神经网络及其学习算法组成。该控制器不需要被控对象的先验知识，也不依赖于被控对象的辨识模型，能快速跟踪对象的动力学行为，具有良好的自适应性和动态输出跟踪响应性能。     

直驱XY平台伺服系统的递归神经网络鲁棒跟踪控制

针对永磁直线同步电机驱动的XY平台存在的系统滞后、未建模动态、系统参数变化摩擦力以及外部负载扰动等不确定性因素对伺服系统性能的影响,提出一种递归神经网络控制方法,来控制XY平台伺服系统的运行状态,以达到鲁棒精密跟踪控制的目的。由于递归神经网络是一种动态的映射结构,对上述不确定性均能有效控制,它具有前馈和反馈两种的网络连接方式,同时递归神经元具有内部的反馈回路,不需外部的延时反馈,即可获得系统的动态响应。仿真实验结果表明,所设计的控制系统具有较强的鲁棒性能和快速跟踪性能,大大减小了系统的轮廓误差,提高了系统的定位精度。     

气动比例位置系统的神经网络控制

采用加入辨识的神经网络PID控制方法对气动比例位置系统进行了实验研究, 研究表明采用该控制方法可以实现气缸活塞全行程任意位置上的精确定位。系统辨识的加入可以在线获得系统动态特性, 辨识输出可以预测系统输出, 从而使控制参数的修正更准确, 能够进一步提高控制精度, 在以抛物线作为理想缓冲曲线, 利用所编制的控制软件控制该系统时, 定位精度可达±0 15mm, 完全能够满足工业机械手的定位要求, 具有较高的工程应用价值。     

VPPAW工艺的变极性焊接电流受控稳定性

在铝合金的变极性等离子弧焊(variable polarity plasma arc welding,VPPAW)工艺中,变极性焊接电流的受控稳定性是确保焊接成形质量的前提. 然而,等离子电弧形态会随焊接电流极性的切变而变化,使得等离子电弧作为VPPAW电源的输出负载具有显著的非线性特性,常规比例积分微分(proportional integral derivative, PID)控制策略无法确保VPPAW电源输出电流波形畸变,而输出焊接电流波形的畸变又会进一步加剧电弧负载的非线性特性,降低变极性焊接电流的受控稳定性. 为了改善VPPAW工艺的变极性焊接电流的受控稳定性,研究了常规PID控制策略下铝合金的变极性等离子弧穿孔立向上焊接工艺的焊接电流受控稳定性以及等离子电弧的动态稳定性,引入了模糊控制理论,基于现场可编程门阵列(field programmable gate array, FPGA)的并行逻辑时序设计方法,设计出了一种具有并行运算能力的模糊PID控制器. 验证试验结果表明,具有并行运算能力的模糊PID控制器能够有效地改善VPPAW工艺的变极性焊接电流波形的受控稳定性.     

电液位置伺服系统神经网络辨识的实验研究

针对电液伺服系统非线性建模问题,研究了电液位置伺服系统神经网络辨识模型的基本结构。分析伺服系统动态模型的输入、输出关系,依据遗传算法优化神经网络权值和阈值,建立神经网络辨识模型的基本结构。利用xPC技术建立阀控缸实时电液伺服实验台,以实验台的阶跃输出信号作为改进BP神经网络系统辨识信号,以实验台正弦输出信号作为验证信号。结果表明:该神经网络辨识模型的基本结构可达到较高的辨识精度,其可信性得以验证,适用于非线性系统模型辨识。     

考虑摩擦影响的机构运动参数动态神经网络预测

研究目的是建立机构复杂非线性运动参数的动态预测模型。考虑摩擦影响的机构运动形态为高度非线性，机构在线控制难度较大。利用人工神经网络方法，建立径向基函数动态神经网络拓扑结构，将机构驱动力矩、阻尼力矩、时间和机构非线性运动参数分别作为神经网络的输入和期望输出，将它们作为RBF神经网络的学习样本，对RBF神经网络进行训练，速度快精度高。该方法为实现复杂机构系统的预测提供了一个理想的建模途径。     

基于RBF神经网络的柔性机构非线性运动模型辨识

柔性机构的运动形态为高度非线性,机构的在线控制难度较大.建立径向基函数(RBF)神经网络,将机构驱动力矩和机构非线性运动参数分别作为RBF神经网络的输入和输出,并将它们作为RBF神经网络的学习样本,对RBF神经网络进行训练.计算速度快,精度高,为实现复杂大系统的辨识提供了一个理想的建模途径.     

基于DRNN的直线永磁同步电机精密位置控制

对直线永磁同步电机伺服系统提出了一种基于动态对角递归网络补偿器的IP位置控制方案.在对比干扰观测器前馈IP位置控制器的基础上,利用动态对角递归网络(DRNN)具有内部反馈结构和动态映射能力对系统参数变化和扰动具有较强鲁棒性的特点,设计出DRNN非线性补偿器,并提出一种改进的RPE学习算法加快权值调整速度、节约在线训练时间.仿真表明该方案能明显改善位置跟踪精度并增强系统鲁棒性.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。