基于变论域自适应模糊PID的压铸机压射速度控制研究

压铸机控制系统是一个非线性、大滞后的复杂系统,传统的压射速度控制算法难以保障精密铸件的压铸品质。对压铸机速度控制系统进行数学建模分析,将变论域与自适应模糊PID技术结合起来,设计了变论域自适应模糊PID控制算法,结果表明,该算法能精确有效地控制电液伺服阀,压射速度动态响应平稳无超调,响应快以及鲁棒性好。     

自适应模糊PID在压铸机控制系统中的应用

为改善压铸机在生产现场的抗干扰性,提高系统的稳定性,采用自适应模糊PID控制技术,进行了模糊算法设计及压射系统数学模型的分析。利用模糊控制器的智能非线性特征弥补PID控制器不足,更好地控制电液比例阀,使系统达到更优的控制状态。通过实验仿真可知,该算法可以减少系统的稳态误差,提高系统抗干扰性。     

基于逆系统方法的压铸机快压射速度控制

压铸机在工作过程中由于液压元件的节流特性及液压动力元件的死区、滞环和限幅等因素使系统具有较强的非线性。为了提高压铸机快压射阶段速度系统的鲁棒性,提出一种基于逆模型的控制算法。建立速度系统的非线性模型;分析系统的可逆性,将系统线性化为伪线性系统;利用反馈控制设计线性系统控制器,实现对系统的控制。利用MATLAB验证基于逆系统方法的压铸机快压射速度控制的有效性。     

P—Q~2图及其应用价值(二) 有效压力线

P—Q~2图说明了压铸过程快压射阶段的性能,即压铸机传给金属的压力和流量的相互关系。压铸上内金属所需压力和压铸机传递的压力能在同一图模表示。因此,可以预测金属临界流动状态。 在研究有效压力线(通常称为机床线)的过程中,深入了解了压铸机压射系统,发现一些锌合金压铸机性能不佳。然而,改造这种压射系统并不困难,压铸厂自己就可进行。通过改造可使压铸机能力提高2—3倍,为改进老设备,增加生产能力,找到了有效方法。     

基于改进差分进化算法的机械手轨迹控制

为提高机械手系统的轨迹控制精度,提出了一种基于改进差分进化算法(Differential Evolution, DE)的机械手轨迹控制方法。以单关节机械手为研究对象,首先,假设其做摆线运动,同时采用PD控制方法跟踪机械手实际运动轨迹;然后,提出改进差分进化算法,优化整个运动过程中机械系统消耗的能量,进而得到一组最优的离散偏差;最后,对这些离散偏差使用三次样条插值法,从而得到连续的机械手实际的运动轨迹。与差分进化算法进行仿真对比,该控制方法得到的机械手运动轨迹精度更高、消耗的能量更少。     

冷室压铸机压射速度的匀加速控制

目前冷室压铸机的压射过程大多采用三级压射的控制方法,不仅给压铸机的调整带来不便,而且还对压铸件的质量和压铸机本身产生不良影响。为了克服这些缺陷,提出了压射速度的匀加速控制,并给出了一种压射速度匀加速控制系统的控制方法、基本组成和控制过程。在实际应用中,通过对原压铸机的液压系统和电气系统进行改造,实现了压射速度的匀加速控制,并取得了良好的效果,从而为压铸机压射速度的控制提供了一种简便而有效的方法。     

变异模糊神经网络算法在压铸机PID闭环压射系统中的应用

针对压铸机压射系统在不同阶段对压力PID闭环控制效果的要求,提出一种变异的模糊神经网络算法对控制系统快速压射阶段进行PID参数优化,对快速压射阶段的压力系统进行模糊寻优。引入的遗传因子自动进行变异,对速度与压力模型快进行参数迭代优化。搭建了仿真平台,通过仿真实验证明,提出的算法可以大大提高压铸机速度与压力的控制效果,其超调量、调整时间明显得到改善,同时也提高了压铸机控制系统的整体压射效率。     

基于模糊PID控制的压铸机实时控制系统设计

为了克服当前压铸机控制系统中存在的不足,设计了一种以ARM为控制核心的压铸机实时控制系统,采用自适应模糊PID控制策略对压射蓄能器与增压器的电液比例阀纠偏控制,完成对压射速度与增压压力等参数的闭环控制与实时监控,通过硬件与软件的相应设计,实现了压铸机工况的实时控制。研究结果为提高压铸机自动控制水平提供借鉴。     

基于差异进化算法的数控永磁直线同步电动机优化设计

在标准差异进化算法(DE)的基础上,提出一种改进的差分进化算法,该算法从动态更新种群、关键参数自适应处理两个方面进行了改进。针对永磁直线同步电动机的特点,运用有限元法精确的求解直线电机内的磁场分布,分别计算边端力和齿槽力后合成得到磁阻力,并将有限元数值分析与DE法相结合,为提高数控系统中直线电动机运行的平稳性,对其磁阻力进行最小优化,具体实例的优化计算结果表明DE算法与有限元结合是电机优化设计领域中一种行之有效的方法。     

压铸机压射系统的试验研究

本文介绍J1125C型压铸机压射机构、增压系统和液压系统的设计原则,研究了压射工艺参数之间的关系。文中重点介绍增压系统中增压控制阀的结构及其控制方法;影响压射速度的因素。最后根据试验中出现的问题,提出了改进压铸机设计的建议。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.