永磁直线同步电机智能分数阶动态面控制

针对永磁直线同步电机(PMLSM)存在的参数变化、外界扰动等不确定因素影响位置跟踪精度的问题，提出一种基于径向基函数(RBF)神经网络的分数阶动态面控制方法。在反步控制器设计的基础上，引入动态面控制技术，避免了反步控制存在的“微分爆炸”问题；在虚拟控制量中加入分数阶微积分项，增加了系统的参数自由度；利用RBF神经网络逼近补偿系统的不确定因素。基于Lyapunov稳定性理论，对所控制的系统进行稳定性分析证明。仿真结果表明，所提出的控制方法能减小系统的跟踪误差，提升鲁棒性，加快系统的响应速度。     

电液位置伺服系统的自适应抗饱和控制

针对电液位置伺服系统的不确定性与输入饱和问题,提出自适应抗饱和控制策略。建立阀控缸系统的数学模型;在基于反步法的设计框架下,将输入饱和导致的跟踪误差加入到李亚普诺夫函数当中,并根据该李亚普诺夫函数设计控制器。通过使李亚普诺夫函数渐近稳定,使得系统跟踪误差收敛于零。针对系统模型中的不确定参数,通过自适应算法对其进行迭代更新,以保证控制器的有效性。以跟踪误差最小为目标函数,采用粒子群搜索算法优化控制器的4个参数。结果表明：加入抗饱和时的控制信号比未考虑输入饱和时的控制信号的幅值明显减小,消除了输入饱和现象;在参数不确定和输入饱和情况下液压缸活塞的最大跟踪误差仅为5.8×10-6mm,相对无抗饱和算法时的跟踪误差有了大幅减小。     

移动机器人神经网络补偿计算力矩控制

针对存在动力学不确定建模项、建模误差及外界干扰的移动机器人,设计RBF神经网络补偿计算力矩控制算法。基于反步法设计运动学辅助速度控制率。根据动力学理想名义模型,基于计算力矩法设计一般的力矩控制器。在此基础上,建立具有不确定建模项、建模误差及外界干扰的移动机器人动力学模型,基于计算力矩法设计带有RBF神经网络补偿的力矩控制器,神经网络的权值由自适应律给出。最后,利用Lyapunov理论证明了系统的稳定性。仿真结果表明：神经网络对系统不确定项具有良好的逼近性能,相比于一般的计算力矩控制,所提出的神经网络补偿计算力矩控制算法具有更好的跟踪性能,控制系统具有更好的鲁棒性。     

基于动态变边界层的PMLSM新型终端滑模控制

为了提高永磁直线同步电机控制系统的动态响应速度和鲁棒性，提出了一种动态变边界层新型终端滑模(DITSM)控制方法。首先，在全局快速Terminal滑模面中引入积分项，构建积分型全局快速Terminal滑模面，在降低抖振的同时避免了奇异问题；其次，设计动态变边界层饱和函数来替代传统饱和函数，保证状态轨迹可以收敛到切换平面而不是边界层内，提高了系统鲁棒性；最后，设计超螺旋干扰观测器估计未知扰动，并采用前馈补偿的方式将观测值引入控制率，增强了系统抗干扰能力。经过仿真验证，DITSM控制方法不仅保证了系统全局鲁棒性，而且有效提高了系统跟踪精度和响应速度。     

基于动态面的并联式加注机器人反步鲁棒控制

针对一种并联式加注机器人,建立包含并联机构动力学方程、液压缸两腔压力动态方程和伺服阀流量方程的多阶动态系统数学模型。为解决系统存在的建模误差、外界扰动不确定性因素,以及递推控制出现的微分膨胀问题,提出一种基于动态面滤波方法的鲁棒控制策略。利用动态面滤波技术简化了控制器的设计,通过构造合适的Lyapunov函数,给出了控制器设计的完整方法,并证明了系统跟踪误差的一致最终有界。仿真结果表明:系统具有良好的轨迹跟踪性能,对于有界的系统模型误差和外界扰动具有较强的鲁棒抑制性能。     

基于改进动态面技术的机械臂系统容错优化

为了提高机械臂系统的控制精度,建立了包含外界干扰、执行器失效故障和模型误差等不确定性的机械臂系统运动模型,通过引入动态面误差来构建改进动态面,设计了自适应律来补偿不确定性和执行器失效故障,从而提出了基于改进动态面技术的容错控制方法,并进行了稳定性分析.实验结果表明:提出的容错控制方法与传统动态面容错控制方法相比,具有更...     

基于改进PID控制的电液伺服系统执行器运动轨迹仿真

电液伺服系统执行器运动轨迹跟踪容易受到外界干扰,导致控制系统不稳定。为解决此问题,设计小波神经网络PID控制系统,并对控制效果进行仿真验证。建立电液伺服阀简图模型,创建阀芯运动的动力学模型,分别推导出控制阀、液压执行器和比例溢流阀动力学方程式。采用小波神经网络对传统增量式PID控制器进行改进,利用MATLAB软件对改进后的控制系统进行仿真;对比分析改进前、改进后系统液压执行器的跟踪轨迹。结果表明：液压执行器在没有受到外界波形突然干扰情况下,2种控制方法都能较好地实现轨迹跟踪;在受到外界波形突然干扰情况下,采用增量式PID控制的液压执行器运动轨迹与期望轨迹存在较大误差,采用小波神经网络PID控制的液压执行器运动轨迹与期望轨迹存在较小误差。所设计的控制系统响应速度较快,能够自适应在线调整控制参数,有效地抑制外界环境对控制系统的干扰,从而提高液压执行器运动轨迹跟踪精度     

水下机械手自适应控制技术研究

针对具有随机干扰及随机参数作用下时变的水下机械手系统,提出水下机械手模型参考自适应系统.将自适应控制理论引入水下机械手位置伺服控制中,并给出理论分析、设计方法及控制算法.仿真结果表明,该系统具有很强的自适应能力,在激烈的随机干扰和随机参数作用下,能有效地抑制模型化误差、外界干扰及系统本身参数变化等影响,使被控对象的输出渐近一致地跟随参考模型的输出,改善了系统的动态性能、精度及稳定性.     

基于径向基函数神经网络控制的机械臂轨迹误差研究

当前,机械臂关节运动轨迹容易受到外界环境的干扰,导致运动轨迹不稳定,抖动现象特别严重,不能很好地满足轨迹跟踪任务的要求。对此,文中创建机械臂双关节运动简图模型,采用径向基函数(RBF)神经网络自适应控制方法跟踪机械臂关节的运动轨迹。分析了机械臂运动轨迹所产生的误差,设计了机械臂关节神经网络自适应控制器,引用李雅普诺夫函数对控制器的稳定性和收敛性进行了证明。结合具体实例,借助于Matlab软件对机械臂双关节的运动轨迹追踪误差进行仿真。同时,与模糊PID控制的仿真误差进行对比和分析。仿真曲线显示,机械臂关节采用RBF神经网络自适应控制方法,运动轨迹追踪所产生的误差较小,输入力矩的振动幅度相对较小。因此,机械臂关节末端采用RBF神经网络自适应控制器,可以降低运动轨迹的跟踪误差,改善振动现象。     

微电网逆变器无差拍控制算法的优化分析

无差拍控制具有跟踪精度高,动态响应迅速的特点,但由于传统的无差拍控制质量在很大程度上取决于控制器和主电路中各器件参数的计算精确度,存在鲁棒性不强的缺点。这里介绍了一种改进优化的无差拍控制算法,同时利用基于最小二乘法求取目标函数最小值的方法进行对系统参数离线优化分析设计,从而解决了存在的参数难以精确设计的问题,也改善了无差拍控制的鲁棒性不强的缺点。同时在Matlab（Simulink）建立系统模型进行仿真实验,验证了无差拍控制算法的优化控制系统具有良好的稳态性能和快速的动态响应,使系统参数的变化有更好的鲁棒性,证明了改进优化算法的可行性。     

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。