超声波测距系统中的温度补偿

超声波测距系统具有使用方便,可靠性强等特点,被广泛用于建筑施工、倒车雷达、车距测量、管道测量等场合.文章首先介绍了采用AT89S52控制的超声波测距系统原理,考虑到温度对超声波测量的影响,着重阐述了DSl8820在测距时的测温原理及温度补偿方法.实验表明,采用温度补偿后的超声波测距系统明显提高了测量精度和稳定性.     

基于RSSI的室内移动机器人测距方法分析

作为一种全新的定位技术,RSSI(Receive Signal Strength Indicator)被广泛应用在WLAN(Wireless Local AreaNetwork)中的室内移动机器人定位领域。为采用几何法进行室内移动机器人定位,提出基于RSSI的测距方法。分析无线信号传播的特点和RSSI测距的原理,建立无线信号传播损耗模型。采用带有无线网卡的笔记本和LINKSYS路由器构建测距实验系统,其中路由器作为基站固定于一点,无线网卡作为移动节点时刻发送信号,通过实验得到距离d与RSSI值的关系曲线,利用无线信号传播损耗模型中的参考点信号强度和比例因子进行标定,并分析测距精度。结果表明,影响测距精度的因素主要包括障碍物和空间大小等。根据确定的无线信号传播损耗模型进行测距实验,实验结果表明:在3 m范围内测距最大误差为0.79 m,能够较好地满足室内移动机器人定位的需要。     

热轧板带轧机辊型检测模拟实验研究

在对电涡流测距传感器进行的重复性和稳定性实验基础上 ,将电涡流测距传感器作为辊型在线测量装置用传感器。根据宝钢热轧厂使用需要 ,在ORG磨轮预留孔内设计了一套电涡流传感器与超声波测距传感器通用的径向运动机构 ,并将该检测装置用于 1∶1模拟工况实验。在简易模拟工况实验系统和 1∶1模拟工况实验系统上进行的辊型检测实验中 ,均得到了被测辊型     

基于MC9S12DP256的汽车ABS数据采集系统设计

设计了基于MC9S12DP256单片机的汽车ABS数据采集系统;详细介绍了该系统的硬件电路以及系统软件设计.大量的ABS实车实验证明:该数据采集系统工作性能良好,可靠性高.采集数据的精度完全可以满足汽车ABS系统的要求.     

公交客车气制动继动阀性能测试系统研究

通过对继动阀在汽车气制动系统的作用,以及其在气制动系统中工作原理的分析,提出了继动阀的性能测试方法,设计了继动阀的测试系统.该系统主要包括工控机、数据采集系统、气动系统、排气系统、传感器、控制电路.当气压调节范围为0.05～1.5MPa,气压测量范围为0～ 1.2MPa时,继动阀性能测试结果表明,气压测量精度可以达到0.25％,系统测试精度高,满足设计要求.     

基于STC89C51单片机超声波测距系统的设计

介绍超声波测距原理和基于STC89C51单片机的超声波测距系统的组成、硬件结构和软件构成。从实验情况来看,该系统可靠性好、精度高。在设计中兼顾系统性能和器件成本的关系,降低整套系统的成本。     

内部轮廓超声成像系统的设计

针对现有内部轮廓成像系统精度不高的缺点,提出一种基于三通道时差法的测距思路,实现了以FPGA与C8051F340单片机为控制器的内部轮廓高精度成像。该系统通过内部轮廓三通道超声测距的方式,得到3个通道的回波时间差来推算待测距离,有效解决了被测物体内部轮廓表面不平坦的难题,提高了成像精度,并通过MATLAB实现内部轮廓的实时呈现。实验表明:该系统性能稳定,精度高,量程大,有广阔的应用前景。     

基于线结构光的工件台阶特征尺寸测量方法研究

提出了一种应用线结构光光源和CCD摄像机对工件台阶特征尺寸进行视觉测量的方法.该方法针对线结构光光平面受工件表面台阶形状调制时发生的形变,利用较高精度的视觉测量系统和算法检测出形变位置从而实现工件台阶特征尺寸的测量.详细阐述了测量系统的原理和系统构建过程,介绍了测量中采用的形变位置亚像素检测算法,并利用实验说明了系统具有较高的测量重复性及准确性.通过台阶测距误差评定实验表明,该方法的测量误差小于0.05 mm.     

基于双目视觉的船舱格子间角焊缝路径识别

针对船舱格子间工作空间狭小,大型自动化设备难以完成舱内自动焊接的问题,提出了一种基于双目视觉获取焊缝路径三维信息的策略。基于张正友标定原理获取双目系统基本参数后,利用C++与OpenCV编写了自适应阈值的二值化处理、改进的Sobel轮廓提取算子、非连续像素点筛除等程序,对双目相机采集的图像进行处理,提取了清晰、低噪点的直角角焊缝中心轮廓图像。基于BM特征点匹配算法与像素点扫描方法,得到了焊缝轮廓上连续特征点的三维信息数据集,利用Origin作图软件拟合后生成了三维直角角焊缝路径。为了验证双目系统测距精度与鲁棒性,设计了可升降、角度可调的滑轨万向节组合模块,实现了从不同拍摄角度、高度采集焊缝图像,并对焊缝上设置的等距特征点的距离进行识别。试验结果表明,当拍摄偏角在30°之内,或正拍高度在150～190 mm内变化时,测距偏差都可以控制在2 mm内,基本满足焊接的精度与稳定性要求,并为焊接的自动化循迹过程提供了数据基础。 创新点： (1)将双目视觉识别测距技术应用于小型船舱格子间内矩形角焊缝中心路径的识别,为自动化的焊接过程提供了循迹数据基础。 (2)设计了滑轨万向结模块,证实了该双目视觉识别系统在不同角度与高度下良好的鲁棒性与识别精度。     

单程调频连续波测距系统的研究

数控机床鲁棒性控制问题一直制约着数控机床的发展,鲁棒性问题严重影响着数控机床的加工精度,为了解决该难题,文章设计了一种新型测距方式,这种方式和传统测距形式不同,是一种采用单程调频连续波测距。它是采用发射装置和接收装置分离的,其测距原理是发射装置发射调频连续信号,发射的信号被接收装置直接接收,接收的信号被称为回波信号,回波信号和发射装置发射的本振信号进行差频处理得到差频信号,并对其构建数学模型。这种测距方式可以解决数控机床刀具运行轨迹误差的快速测量问题,促进误差源参数辨识技术的发展,将会解决数控机床加工空间内对刀具的全闭环控制问题,使得数控机床的加工精度再不会受到机床结构变形、热变形、导轨几何误差等因素的影响,使得数控机床的加工精度显著提升。     

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.