基于AMESim和MATLAB/Simulink联合仿真的采棉头液压系统设计

为解决采棉机采棉头液压马达由于负载不断变化引起的转速不稳定和不同步的问题,采用AMESim和MATLAB/Simulink联合仿真的方法,对采棉头液压系统进行了AMESim液压系统建模,在施加不断变化的负载情况下进行PID控制和模糊自整定PID控制仿真。结果表明:施加PID控制要比不施加任何控制的液压马达转速更加稳定,转速更加趋近于设定值;模糊自整定PID和PID控制都可以使液压马达转速趋近于设定值,但模糊自整定PID控制比PID的控制马达同步精度更高。     

电液力伺服系统参数自整定模糊PID控制器设计

针对飞机结构强度试验中常用的电液力伺服系统,讨论了系统组成和数学模型。利用MATLAB设计参数自整定模糊PID控制器以克服系统非线性和负载扰动的影响;通过系统辨识建模的方法,采用预报误差法得到系统ARMAX参数模型辨识结果;以辨识结果为对象对设计的参数自整定模糊PID控制器进行Simulink仿真。结果表明:相比常规PID控制器,采用参数自整定模糊PID控制器进行控制,系统具有更好的稳态精度、快速性和鲁棒性。     

基于AMESim和MATLAB的盾构推进液压系统仿真

根据AMESim和MATLAB软件各自的特点,采用了AMESim和MATLAB联合仿真的方法对盾构推进液压系统进行了仿真,并在控制仿真中采用了基于普通PID和模糊自整定PID的压力和速度复合比例控制,结果表明：系统稳态精度较高,调节时间短,超调小,可以克服非线性时变特性的影响.     

数控机床伺服系统的模糊自整定PID仿真研究

以数控机床进给伺服系统为研究对象,结合模糊控制和PID调节的各自优点,分析研究模糊PID控制器的实现方法。运用MATLAB建立应用模糊PID控制的伺服系统仿真模型,对模糊PID控制器的设计方法与应用效果进行了研究探讨。仿真实验结果表明模糊PID控制器能够很好的弥补常规PID控制整定不良、性能欠佳和适应性差的缺点,有效地减少了系统响应的超调,具有良好的动态特性。     

气动油压伺服系统模糊自适应整定的PID控制研究

针对经典的基于对象精确模型的PID控制方法自适应性差,难以适应具有非线性、时变不确定性的被控对象,采用了一种结构简单的模糊自适应整定的PID控制方法。将该智能PID控制应用于气动油压伺服系统中。实验结果表明：具有自学习和自适应能力的模糊PID控制方法,能够适应被控对象在较大范围内的变化,具有较强的鲁棒性,其控制品质明显优于常规PID控制方法,将其应用于气动油压伺服系统是可行的。     

一种模糊自整定PID复合控制在非对称液压缸电液伺服系统中的应用

针对非对称缸电液伺服系统所具有的非线性、时变性和增益不对称性的特点,采用模糊自整定PID控制的方法,根据系统控制性能的变化使PID的参数进行在线调整,以克服系统的非线性、时变性和增益不对称性对电液伺服系统的不利影响.仿真和实验结果表明,采用模糊自整定PID控制的非对称缸电液伺服系统具有良好的控制性能.     

模糊自适应整定PID控制在数控精密校直机电液伺服系统中的应用研究

数控精密校直机电液伺服控制系统具有低阻尼、时变性、非线性等性质,运用常规的PID控制难以达到满意的控制效果,运用模糊自适应整定PID控制,结合模糊控制和PID调节的优点,将专家经验用于对PID的kp、ki、kd参数在线自适应整定,增强PID控制器对非线性、时变性系统的调节控制性能,通过仿真实验结果表明:模糊自适应整定PID控制器在数控精密校直机液压伺服系统的控制中,表现出了良好的自适应性、稳定性、鲁棒性,能够用来实现对数控精密精校机电液伺服系统的有效控制.     

新型电动调节阀的驱动与控制系统

设计了以STC89C52RC单片机作为控制器核心的新型电动执行器,建立了驱动系统的数学模型,采用模糊参数自整定PID作为该驱动系统的控制策略,从而实现了对调节阀阀门开度的精确控制。MATLAB仿真结果表明：与传统的PID控制器相比较,该控制器具有响应快、响应平稳的特点,改善了系统的动态特性。     

改进预估模糊PID控制在气动阀门定位系统中的应用北大核心

针对工业中常见气动阀门定位控制系统中的大惯性、时滞性等问题,在建立并辨识得到系统简化模型的基础上,提出了一种基于改进预估模糊PID的控制方法。在传统PID控制的基础上引入变论域模糊控制器和改进型Smith预估器以提高控制系统的自适应能力并补偿纯滞后环节;针对论域伸缩因子参数难整定的问题,采用加入多种群和自调节交叉变异概率的改进型遗传算法对其进行参数寻优,在改善传统遗传算法早熟现象的同时,以获取最优的控制器参数。仿真和实验结果表明,所提出的控制方法在气动阀门定位系统中的应用较传统PID控制和Smith预估模糊PID控制,有效提高了系统的动静态性能,且具有较强的鲁棒性和抗干扰能力。     

自整定模糊PID控制在脱硫搅拌速度控制系统中的应用

以铁水预处理脱硫搅拌器速度控制系统为研究对象,介绍铁水脱硫搅拌器液压系统及其控制策略;设计基于自整定模糊PID的脱硫搅拌器速度控制器及模糊控制规则;通过仿真,对比传统PID控制、自整定模糊控制及自整定模糊PID控制的阶跃响应曲线.结果表明,自整定模糊PID控制响应速度快,稳态误差小.     

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).     

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.     

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.     

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。