复杂地形下铣刨机械切削深度模糊PID控制研究

以污染砂土铣刨收集机械电液切深随动控制系统为研究对象,针对被控对象具有非线性、时变性和外负载干扰的特点,利用模糊控制理论研究污染砂土铣刨收集机械切深量的自动控制方法,设计模糊PID控制器,并利用Matlab/Simulink建立切深控制系统的仿真模型.仿真结果表明:采用模糊PID复合控制策略,系统的响应速度、调整时间、超调量等指标均较好地满足了控制要求,是一种有效的控制算法.     

基于切削颤振抑制系统的BP神经网络PID控制研究

从颤振的发生机制及集中质量系统的颤振运动微分方程出发,以镗削颤振抑制问题为背景,建立了具有连续分布质量的压电智能切削颤振抑制系统动力学模型,重点研究了BP神经网络与经典PID控制相结合的智能控制策略,为切削颤振的智能控制提供了新的方法。继而在Simulink中分别利用经典PID和BP神经网络PID对切削颤振抑制系统进行控制仿真。仿真结果表明:和经典的PID控制相比,BP神经网络PID控制自适应能力更强。     

基于BP网络自整定的PID控制在加工过程中的应用

基于BP神经网络自整定的PID控制,把BP神经网络与传统的PID控制很好的结合在一起,利用BP神经网络实时在线学习来调整PID的三个系数,这样充分发挥各自优势,从而拓宽PID控制的应用领域.对车床加工过程进行建模,加入BP神经网络自整定PID控制,以车床加工过程作为被控对象进行仿真研究.仿真结果表明,加工过程在BP神经网络自整定的PID作用下的控制效果良好.基于BP神经网络自整定的PID控制较传统的PID控制具有更好的鲁棒性和自适应性.     

BP神经网络在流量比值控制系统中的应用

针对在PCT-2型过程控制装置进行流量比值控制时,PID参数难以整定的问题,提出了一种基于神经网络自适应的PID流量比值控制方法.该算法利用BP神经网络的非线性表示能力,通过系统的自学习来实现具有最佳组合的PID控制.这种方案达到了在线实时控制的目的.实验表明:在流量比值控制系统中,基于BP神经网络的PID控制算法比普通PID控制算法具有更好的动态性能和鲁棒性,能取得很好的控制效果.     

基于神经网络的电液位置伺服疲劳试验机控制系统研究

以电液位置伺服控制系统为研究对象,在传统PID控制的基础上,提出一种基于BP神经网络的控制策略。利用神经网络的自适应、自学习的特点,实现对电液位置伺服系统PID参数的自整定。搭建试验机并进行实验,结果表明:BP神经网络PID控制很好地解决了电液伺服控制系统中加载速度及稳定性等问题,是一种实用性很强的控制策略。     

BP神经网络在轧机厚度控制AGC-PID系统的应用

针对采用传统的PID控制系统,在轧制升速降时,带钢厚度变化的问题,采用BP神经网络技术和传统的PID技术相结合,通过神经网络来控制PID系统的参数,从而达到对带钢厚度的控制,取得了良好的效果。     

神经网络PID控制的液压驱动主动升沉补偿预测控制研究

为了提高船舶在海面上作业时补偿精度,采用BP神经网络PID控制方法,并对船舶升沉运动输出误差进行仿真。建立船舶主动升沉补偿系统简图,分析船舶升沉运动工作原理,给出液压缸驱动传递函数。引用BP神经网络算法,采用梯度下降法对BP神经网络加权值进行修正,通过学习速率来补偿控制系统输出误差,从而实现PID控制器参数在线调节。在受到不同负载影响状况下,采用MATLAB软件对船舶升沉运动补偿精度进行仿真,并且与PID控制补偿精度进行对比。结果表明:采用PID控制器,船舶升沉运动输出误差较大,控制系统反应速度较慢;而采用BP神经网络PID控制器,船舶升沉运动输出误差较小,控制系统反应速度较快,同时,随着负载质量的增加,输出误差就会增大。采用BP神经网络PID控制系统,响应速度快,补偿精度高,提高了船舶在海面上作业定位精度。     

枕式包装机伺服控制系统的研究与优化

为了确保枕式包装机各项功能能够得到精确高效的运行,对神经网络控制策略进行了具体的研究。通过建模仿真,对比分析经典PID控制与神经网络PID控制的优劣,论证了神经网络PID的控制方法更有优势。在优化完成的基础上,开发出色标切功能。对包装机进行实际生产测试结果表明,整套系统在完成相应功能的过程中满足了稳定性和包装精度的要求,具有良好的应用价值。     

伺服系统中PID控制器参数整定的研究

针对伺服系统中常用的比例-积分-微分(PID)控制器的参数手动整定不方便的问题,对机器学习算法和模糊控制进行研究,重点分析反向传播(BP)算法和模糊控制器的设计方法,提出一种基于机器学习和模糊控制的PID参数整定方法。利用BP神经网络的学习能力得到系统模型,结合模糊控制进行预测得到PID参数,并在实验平台上进行验证。研究结果表明:通过机器学习和模糊控制得到的PID参数具有较好的控制效果,该方法能够避免手动整定PID参数,节省大量时间。     

基于神经网络的疲劳试验机控制系统仿真及实验研究

针对疲劳试验机控制系统，设计了基于BP神经网络和PID的并行控制器。该控制器充分利用了经典PID控制算法简单的特点，又利用了神经网络良好的自适应能力，首先通过PID控制为神经网络的在线学习提供训练样本，然后神经网络逐渐学习被控对象的动态逆模型并取代PID控制器起主导作用。该方法降低了PID参数的调整难度，同时对控制对象的刚度变化表现出良好的鲁棒性，并通过仿真证明了所设计系统的有效性。     

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.     

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.     

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.