机器人柔性关节前馈力/位混合控制策略研究

针对机器人关节柔性引起的轨迹跟踪误差问题和末端执行器残余振动现象,在PD反馈控制律基础上,提出一种基于柔体动力学模型的前馈力矩补偿控制算法和后置多模态自适应输入整形算法前馈力/位混合控制策略。建立六轴工业机器人柔体动力学简化模型,在不附加关节编码器和外设的情况下进行柔体动力学参数辨识,再将动力学模型改写为力矩计算方程,经计算得到前馈力矩并加入控制律中进行补偿;计算前馈力矩所用的期望轨迹需经过输入整形器处理,考虑机器人系统的时变性问题,采用后置多模态自适应输入整形算法对期望输入位移信号进行命令整形,从而抑制末端的残余振动现象。结果表明：所提出的前馈力/位混合控制策略能有效减少轨迹跟踪误差,抑制机器人末端的残余振动现象。     

含谐波传动关节的机械臂在不同转速下的时频特性

谐波传动关节是机械臂的典型关节。为了研究含谐波传动关节的机械臂在不同转速情况下的时频特性,针对空间机械臂,研制机械臂实验装置和测试系统,测试不同转速下机械臂关节处和末端标志点的振动响应。采用小波变换信号分析方法并借助于机械臂的驱动模型,分析谐波传动关节处的摩擦和运动滞后等非线性因素对不同转速下机械臂振动特性的影响。基于非线性响应面法和非线性规划方法分析了机械臂的最佳运行工况。研究结果表明:小波变换能够较好地表征机械臂在不同转速下关节和末端振动响应的时频特征;随着转速的增大,机械臂关节处和末端标志点的振动能量向低频段集中,振动能量峰值及其对应的频率呈现出局部波动;机械臂末端的振动特性明显弱于关节,关节处的振动频率更为丰富,但关节的振动能量峰值衰减比末端要快;且机械臂处于低速运行工况时可以保持较好的动力学性能。研究结果揭示了含谐波传动关节的机械臂在不同转速下的时频特性,对含谐波关节的机械臂设计及其振动抑制技术水平的提高具有重要意义。     

基于参数解耦陷波滤波器的工业机器人末端振动抑制

六自由度工业机器人关节因传动装置刚度不足而引发末端振动,通常采用传统陷波滤波器解决该问题;但滤波器参数之间存在耦合,导致滤波器参数难以快速整定。为此,基于所建立的工业机器人双惯量负载模型设计出具有参数解耦的陷波滤波器。分析传统陷波滤波器传递函数,采用极点零点抵消法对陷波器参数进行解耦设计;将陷波器中心频率、宽度以及深度作为陷波滤波器的参数;最后,利用傅里叶变换和对数衰减法快速整定改进后的陷波器参数,以此来抑制工业机器人末端振动。搭建六自由度工业机器人实验平台进行实验。结果表明:参数解耦陷波滤波器不存在参数耦合,参数整定方便;使用参数解耦滤波器比未使用滤波器相比可降低78.5%的工业机器人定位振动,证明改进的参数解耦陷波滤波器对定位振动抑制的可行性与有效性。     

降低防护型装甲车体焊接接头残余应力工艺研究

为了降低超高强装甲钢车体焊接接头残余应力,文中通过对超高强装甲钢焊接接头频谱振动时效和超声波冲击振动时效,验证焊缝残余应力消除效果,并评价时效处理前后尺寸精度变化,最后通过焊接工艺评定试验来分析焊态、整体振动时效和超声波冲击振动时效不同状态下的力学性能、硬度和金相组织差异。通过分析研究可知：经频谱时效振动后的焊缝残余应力可降低29.52%;经超声波冲击振动后的焊缝残余应力可降低50%左右;超声波双面双侧冲击的试板尺寸变化量最小,尺寸变化量在±0.05 mm内;频谱时效振动的试板尺寸变化量最大,尺寸变化量在±0.2 mm内。同时超声波冲击时效后的焊缝显著提高了接头的连接强度及抗弯能力;但不同状态下对应的焊接接头各区域硬度变化无显著差异,焊接接头各区域的组织基本一致,无差异。     

锻造操作机行走系统液压冲击振动及定位控制

针对锻造操作机大车行走系统在停止时刻液压冲击振动噪声大、定位不准确等问题,分析产生液压冲击和定位不准的原因,建立了大车行走液压系统数学模型,提出在大车位移到达目标值精度范围临界点时,控制策略由PID控制切换为比例方向阀零控制信号,并在靠近行走液压马达进出油口背向并联二次溢流阀组,设置阻尼孔连通液压马达进出油口,通过AMESim平台进行仿真分析对比。结果表明:切换控制策略结合二次溢流阀组和连通阻尼孔的硬件补偿措施,可以隔离高压油源和快锻压机锻压工件的反作用力对大车行走马达的影响,有效降低操作机停止时刻液压冲击振动,提高系统阻尼比,加快液压冲击的衰减,提高大车定位精度。     

一种加速度反馈式液压阻尼器的研究

在传统液压线性阻尼器的基础上并联一阻尼补偿器,组成了一种加速度反馈式液压阻尼器.该阻尼器的阻尼系数随激振频率的升高而降低.当激振加速度大而激振位移小时,该阻尼器能提供较小的阻尼,以减小被隔振物体的振动响应加速度;当激振位移大而激振加速度小时,该阻尼器提供较大的阻尼,以减小被隔振物体的振动响应动行程.     

LSP提高TC6钛合金振动疲劳性能及强化机理研究

针对TC6钛合金进行了激光冲击强化(LSP)参数设计,应用XRD衍射仪对LSP试件进行了残余应力分布规律测试和图谱分析,采用透射电子显微镜对强化层微观组织进行了观察,对有无LSP标准振动疲劳试件进行了振动疲劳对比试验。研究表明,TC6钛合金LSP较佳功率密度为3 GW/cm2,LSP能在材料表层产生深度为1.6 mm的高数值残余压应力场,表面残余应力可达-660 MPa,深度为0.1 mm处残余应力最大,最大值可达-690 MPa;LSP后没有新相产生,且晶粒细化、残余微观应变导致Bragg衍射峰宽化;LSP后钛合金表层出现高密度位错和纳米晶;钛合金标准振动疲劳试件LSP后疲劳极限由438.6 MPa增加至526.7 MPa,提高20.1%;疲劳断口分析表明LSP产生的组织细化和高数值残余压应力场可以有效抑制疲劳裂纹的萌生和扩展,从而提升TC6钛合金的抗疲劳性能。     

基于非线性能量阱的小卫星飞轮微振动抑制

研究基于橡胶材料迟滞阻尼特性的非线性能量阱对光学卫星飞轮微振动的抑制。通过对飞轮扰动机制的分析,建立考虑飞轮扰动的动力学模型。结合飞轮微振动模型,提出一种基于非线性能量阱的飞轮微振动抑制方法,设计一种基于非线性能量阱的金属橡胶减振器。设计卫星飞轮地面试验方案,验证了微振动抑制方法的有效性。试验结果表明:飞轮微振动模型分析准确,设计合理,基于该模型的减振器能有效抑制飞轮微振动。     

钒掺杂镁基微弧氧化膜的制备及电化学与光学性能

针对TC6钛合金进行了激光冲击强化(LSP)参数设计,应用XRD衍射仪对LSP试件进行了残余应力分布规律测试和图谱分析,采用透射电子显微镜对强化层微观组织进行了观察,对有无LSP标准振动疲劳试件进行了振动疲劳对比试验.研究表明,TC6钛合金LSP较佳功率密度为3 GW/cm2,LSP能在材料表层产生深度为1.6 mm的高数值残余压应力场,表面残余应力可达-660 MPa,深度为0.1 mm处残余应力最大,最大值可达-690 MPa; LSP后没有新相产生,且晶粒细化、残余微观应变导致Bragg衍射峰宽化;LSP后钛合金表层出现高密度位错和纳米晶;钛合金标准振动疲劳试件LSP后疲劳极限由438.6 MPa增加至526.7 MPa,提高20.1％;疲劳断口分析表明LSP产生的组织细化和高数值残余压应力场可以有效抑制疲劳裂纹的萌生和扩展,从而提升TC6钛合金的抗疲劳性能.     

XYZR焊接机器人运动学的研究

设计了一种XYZR型四自由度直角坐标焊接机器人,传动机构由x、y、z三个方向上的滑动机构和一个R方向的转动机构组成,转动机构连着末端执行机构即焊枪,在控制系统作用下,通过各个传动机构的运动实现末端执行机构的焊接功能。利用D-H参数法建立XYZR焊接机器人的运动学方程,对机器人的末端执行机构的运动进行理论推导,并利用ADAMS软件对机器人的末端执行机构进行运动学仿真研究,最后运用半实物仿真平台对焊接轨迹进行仿真测试。结果表明,由4个关节引起的运动的机器人末端位移、速度曲线变化平稳,验证了结构设计的合理性,为机器人控制系统的设计提供了依据。     

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.     

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.     

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。