基于迭代学习的电动直线加载复合控制

为测试某型航天用电动伺服机构的实际工作性能,设计一种以大导程精密滚珠丝杠副为力矩/力转换元件的电动直线加载系统。为克服电动直线加载系统多余力扰动问题,提出一种引入角速度前馈补偿、串入电流内环和位置内环的多闭环复合控制策略;采用一种以分数阶PIλDμ控制器作为力外环的反馈控制、分数阶迭代学习控制(FO-ILC)作为补偿控制的方法。直线加载仿真实验和多余力抑制仿真实验表明,所提控制策略较好地抑制了直线加载多余力。     

电动直线加载系统不确定性分析及扰动抑制补偿研究

为测试某型航天电动直线伺服阀实际工作性能,提出了一种永磁同步电机加滚珠丝杠的电动直线加载方案,采用机理建模方法,建立电动直线加载系统数学模型,并分析系统模型不确定性来源:电机模型结构不确定、驱动器参数摄动、滚珠丝杠扭矩波动和舵机不确定性扰动。针对理论模型,提出基于扰动观测器的双回路控制系统设计方法,通过鲁棒内回路控制结构等价变换,以抑制舵机扰动要求为性能权函数,采用H∞混合灵敏度方法设计内回路扰动观测器,外回路以提高加载系统整体性能为要求,采用PID控制算法。试验结果表明,在加载力2000N,加载频率4Hz下,系统多余力抑制比达到86. 4%,且系统静态和动态加载均达到"双十"指标。     

基于改进萤火虫算法的电动负载模拟系统设计

针对飞机舵机电动负载模拟系统因非线性干扰和多余力导致加载性能不良的问题,采用直线音圈电机改变传统加载方式,并提出一种基于不完全随机萤火虫算法、结合扰动信号前馈控制和多工况专家控制的复合控制策略。在前馈环节,以舵机输出位置信号作为扰动,计算并设计前馈补偿控制器对其进行抑制;在反馈环节,采用多工况专家控制,通过对模拟气动载荷工况和误差信号的判断,设计专家控制规则;同时,利用不完全随机初始化法和动态变步长搜索法对萤火虫算法进行改进,使其完成对专家控制的参数寻优。仿真结果表明,系统在复合控制器作用下的加载精度和加载误差均优于传统PID控制系统,对多余力的抑制程度可达78%,控制性能得到明显提升。     

对流量补偿电液负载模拟器的研究

针对多余力影响电液负载模拟器加载精度的问题,增加了流量补偿回路。由于运动的承载系统强迫负载模拟器跟随其运动产生多余力,而多余力是影响电液负载模拟器跟踪精度的主要因素。利用流量补偿速度回路、伺服阀力回路分别控制负载模拟器速度和输出力,从结构上实现力与速度的解耦,消除被测系统主运动对电液负载模拟器加载精度的影响。利用阀口压差对速度回路中的伺服阀流量进行修正,以消除压降对流量的影响从而提高流量补偿回路动态性能。基于PID控制建立系统数学模型并搭建物理仿真模型,通过理论分析和仿真结果分析证明该方案具有可行性。     

速度同步控制在抑制多余力中的应用

以某直升机旋翼加载系统为例,对被动式力加载系统的多余力抑制进行了研究.提出了传统的结构不变性原理的补偿方案,分析它的优点和不足,进一步提出了利用助力器的控制信号进行速度同步控制、抑制多余力的新方案.仿真和试验结果证明该方案在系统的动态品质、鲁棒性和消扰能力等方面具有相当好的效果.     

直线电机速度和加速度的复合前馈控制

针对直线电机伺服控制,提出将带自适应前馈系数调节的速度+加速度复合前馈控制引入直线电机PID的控制中,与单纯的加速度前馈、速度前馈及反馈控制相比,能显著减小系统的超调量和调整时间,同时具有很快的响应速度和良好的动静态特性,使直线电机更好地应用于对速度和精度要求严格的系统。并进行MATLAB仿真和实验。     

P-Q伺服阀在减摇鳍电液负载仿真台中的应用

由于P-Q伺服阀内部的压力反馈作用,使得采用P-Q伺服阀控制的被动式加载系统能取得较好的抑制多余力效果.通过对P-Q伺服阀工作原理的分析,分别建立了P-Q伺服阀和采用P-Q伺服阀控制加载的减摇鳍负载仿真台的传递函数模型.通过对P-Q伺服阀加载试验曲线的分析表明,采用P-Q伺服阀控制可以有效地抑制减摇鳍仿真台的多余力,特别是减摇鳍系统启动和换向时的多余力.     

阀控非对称缸被动加载系统中多余力的抑制

从系统的力传递函数出发,分析了阀控非对称缸被动加载系统中多余力的存在对系统加载性能的影响,此多余力经结构不变性原理补偿后在低频段可以很好地被消除,但由于在高频段滞后现象加重,多余力对加载系统的影响仍然存在。针对这一问题提出了采用最优二次型抑制多余力的控制方法,将系统的力传递函数经最优二次型控制理论优化设计并仿真后发现,在结构不变性原理的基础上采用最优二次型的控制方法可以使阀控非对称缸被动加载系统中的多余力在高频段得到较好的抑制,提高了系统的加载性能。     

被动式力伺服系统的多余力抑制方法

为测试某型电动伺服阀是否满足姿轨控发动机的高推力、快响应要求,采用伺服旋转电机与精密滚珠丝杠的方式,研发了一种被动式力伺服系统(PFSS)。硬件上采用先进的PXI总线搭建了PFSS,软件上采用Lab VIEW作为PFSS的上位机平台;针对多余力严重干扰PFSS加载精度的问题,为抑制多余力,基于耦合被测阀的数学模型,提出一种多闭环复合控制方法,并引入了位置闭环补偿控制,并采用复矢量PI控制应用于电流内环,提出一种模糊自适应整定PID控制方法应用于力外环。实验结果表明,所提控制方法有效地抑制了多余力,满足了"双十指标"。     

电液伺服加载力差信号前馈控制

提出利用电液加载前馈舵机系统力差信号减少多余力的控制方法。传统的方法是测量舵机近似的速度信号进行前馈控制,力差前馈控制是测量舵机系统产生加速度的力信号进行前馈控制。仿真结果表明,采用该方法消除多余力的效果很好。     

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。