基于位置闭环的制振陷波器改进和参数整定

伺服系统中因传动装置刚度不足会引发定位振动问题。针对采用陷波滤波器解决该问题时存在陷波滤波器参数整定过程繁琐且整定抑制效果不明显,基于零极点抵消法提出一种改进的前馈陷波滤波器。该方法采用振幅最高点所对应的频率和对数衰减法快速整定陷波器的中心频率、陷波宽度和陷波深度。实验结果显示：使用该滤波器比未使用滤波器相比可降低88.4%的定位振动,证明将改进滤波器作为前馈陷波滤波器可实现定位振动抑制以及滤波参数整定方法的有效性。     

伺服系统机械谐振的在线检测及其抑制

伺服系统中的传动环节一般具有一定的弹性，会导致伺服系统产生机械谐振，需要准确检测谐振并将其抑制。在保证伺服系统性能的前提下，引入陷波滤波器抑制机械谐振。设计了一套基于振动信号频谱的陷波器参数整定策略，可以自动设定陷波器陷波频率、宽度、深度参数；设计了基于SDFT(滑动傅里叶变换)的频谱提取算法，可以快速准确获取当前系统的谐振频率，在不依赖于伺服系统机械参数的条件下自动整定陷波器参数，抑制机械谐振。实验证实谐振检测方法的准确性和陷波器参数整定的有效性，该方案可以准确地检测伺服系统谐振并完成谐振的自适应抑制。     

基于模型结构的伺服谐振陷波器参数离线整定

针对传统陷波器在对交流伺服系统因连接轴的弹性而引起的机械谐振无法有效抑制不足,提出了一种基于模型结构的改进型陷波器,重点设计其陷波中心点频率、陷波宽度、陷波深度参数的离线整定过程,将其加入伺服速度控制环节中以达到抑制机械谐振的效果。通过与传统陷波器及常用三参数仿真结果进行对比分析,验证了此陷波器的有效性和整定方法的快速准确性,对高性能交流伺服系统的高频扰动抑制研究具有重要的理论和现实意义。     

基于工具坐标标定改进的工业机器人零点位置自整定方法

在工业机器人应用过程中更换工具时需要重新标定工具坐标,一般情况下工具坐标通过固定点约束的3点法进行标定,此方式在机器人本身零点位置不准确的情况下往往会得到一个较差的结果。基于3点法中定点约束的原理,提出一种改进的工业机器人零点位置自整定方法,对出厂标定过的六自由度串联机器人,修改其零点位置与工具坐标的标准值产生给定误差,基于空间内一个固定点的约束关系,在已知机器人连杆参数的情况下建立机器人坐标变换模型,取21组机器人关节角与笛卡尔坐标数据作为辨识条件参数,机器人工具坐标与零点位置的偏差作为未知数据,通过最小二乘迭代算法计算出工具坐标与零点位置的偏差数据。将实验对象的整定结果和给定的误差参数进行对比,整定结果基本与给定误差一致,并通过比较自整定前后示教器上的位置显示值之间的误差值,证明了校准算法的可行性。     

基于改进陷波器的激光振镜高频振动抑制研究

文章提出一种改进陷波器来抑制激光振镜电机摆动时扭力共振频率所产生的振动与噪音。首先,通过精心设计的实验,分析振镜电机共振频率,建立振镜电机扭力共振频率频谱图,进而设计出抑制共振频率的陷波滤波器电路;其次,通过严格的数学分析与理论推导,计算出最佳电路参数,利用Orcad PSpice与Matlab进行仿真验证电路参数,实现了数字陷波器的优化设计,并将实体电路加入激光振镜电机驱动器回路内。设计两级级联陷波滤波器,通过可变电阻可以方便地调节滤波频率和衰减深度的参数,以抑制一阶和二阶扭转共振。实验结果表明,该陷波器的Matlab仿真结果和计算分析结论一致,级联陷波器能有效地抑制振镜电机运转时的扭转共振,提高激光振镜扫描系统的精度和稳定性。     

最优输入整形抑制柔性机械臂的残留振动

研究机器人柔性机械臂末端残留振动的抑制,给出两自由度柔性臂的动力学方程设计了最优输入整形器,并将其应用到柔性臂的运动,抑制柔性臂末端残留振动,通过实验对比与分析,结果表明最优输入整形能够有效地抑制机械臂末端的残留振动,且引入系统的时滞时间更短.     

关节非线性的串联双连杆机械臂运动控制研究

各轴上的关节非线性和不同轴间的动力学耦合效应是导致多轴工业机器人轨迹跟踪误差的主要非线性因素。因此,提出一种考虑关节非线性的串联双连杆机械臂模型的工业机器人运动控制方法。通过构造机械臂运动学和动力学模型,将连杆的非线性刚度和摩擦力直接辨识为关节非线性,从而进行参数化建模,通过实验验证了模型的有效性;提出了辨识双连杆动态模型的二自由度控制方案及带可变陷波滤波器的反馈整型控制方案,对机械臂运动进行控制。实验结果表明:与常规PI轨迹跟踪控制方法相比,此控制方案缩短了调整时间且减小了最大路径误差,降低了超调量。研究表明该控制方案能够有效地抑制残余振动,提高机械臂运动稳定性和轨迹追踪精度。     

基于自适应陷波器的伺服系统谐振抑制

为了提高伺服系统的性能,需对伺服系统中机械传动装置刚度有限所引发的机械谐振问题进行研究。文章提出了基于改进的FFT在线频率检测法结合陷波滤波器的自适应谐振抑制策略。通过提取旋转因子的公因子来减少内存的读取次数,进而提高FFT的频域分析速率。利用改进的FFT分析伺服系统中电机的转速误差信号,提取谐振频率信息;又设计了一种获取陷波器宽度、深度参数的方法。利用得到的陷波频率、宽度、深度参数设计陷波滤波器来达到谐振抑制的目的。最后通过实验得出,该方案能有效抑制伺服系统的机械谐振。     

工业机器人动力学参数的改进遗传算法辨识

为了准确辨识出六自由度工业机器人的动力学参数,提出一种基于改进遗传算法的参数辨识方法。构建牛顿-欧拉机器人动力学模型,明确反映各关节力矩与动力学参数的函数关系;通过改进遗传算法获取优化激励轨迹,并对机器人进行动力学参数的整体辨识,减少关节间耦合作用影响,避免多次识别实验环境不一致而产生的误差。最后采用最小二乘法计算机器人的动力学参数,解决因初始值选择不合理而导致辨识精度受限的问题。实验结果表明：此方法得到的最优激励轨迹能够满足约束条件,缩短优化时间,有效提高动态参数辨识的准确性和有效性。     

基于输入整形法的一个3自由度机器人抑制残余振动的灵敏度分析

输入整形法是一种抑制机器人残余振动的简单有效的控制策略。输入整形器的鲁棒性是评价整形器性能的重要参数,它表达了整形器能抑制系统残余振动的频率范围。通过分析输入整形器的灵敏度曲线可以获得整形器的鲁棒性。首先,介绍了多种输入整形法的原理;其次,表达了各种输入整形器灵敏度的计算方法;最后,通过数值模拟分析了一个3自由度平面并联机器人的多种输入整形器的不灵敏度。数值仿真结果表明极不灵敏类输入整形器拥有最好的鲁棒性,而零振动类输入整形器的鲁棒性最差。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.