双电极电弧焊系统的非线性鲁棒自适应控制

本文针对可消耗双电极熔化极气体保护电弧焊接(DE-GMAW)系统,建立了一个双输入双输出非线性模型,并基于此提出了一种鲁棒自适应控制器的设计方法,可用于系统存在未建模动态和未知有界扰动的情况.应用Lyapunov稳定性理论证明,该鲁棒自适应控制器可保证整个系统的稳定性,且通过适当选择设计参数,可满足高精度的跟踪.仿真结果表明此控制器对DE-GMAW具有良好的控制效果.     

DE-GMAW焊接系统的非线性建模及参数估计

为了更好地研究和控制可消耗的双电极熔化极气体保护电弧焊接系统(DE-GMAW),针对该系统建立了一个多输入多输出(MIMO)的非线性模型,并采用递推最小二乘法原理对模型参数进行了估计.阶跃信号下交叉验证结果表明,所得模型很好的反映了其系统特性,可以用来进行控制系统的设计与系统本身的分析理解.     

室温单电子晶体管制备进展

单电子晶体管由于其纳米级的器件尺寸和超低功耗等优点被广泛认为是当前最有应用前景的纳米电子器件之一,实现室温下的正常工作和器件结构的精确控制是其实用化的关键。室温单电子晶体管的主流制备方法为自顶向下工艺和自底向上工艺。自顶向下工艺便于器件集成,但纳米尺度下的制备工艺误差较大,室温单电子晶体管的性质难以稳定;自底向上工艺能够比较容易地制备出室温单电子晶体管,但同样有耦合结构误差较大的问题。在结合自顶向下工艺和自底向上工艺的基础上,引进纳米结构制备的新技术来提高工艺过程的可控性,是下一步室温单电子晶体管制备的研究重点。     

Effects of Impact Inertia and Surface Characteristics on Deposited Polymer Droplets in Microcavities

Microflow visualization and computational fluid dynamics (CFD) are complementarity performed to study the evolution of a single poly(ethylenedioxythiophene) (PEDOT) droplet ejected from a piezoelectric ink-jet printhead and the equilibrium film characteristic of the droplet deposition in a microfabricated cavity. The verified CFD code is further applied to investigate the influences of contact angles thetas_s of the PEDOT droplet/air interface and the PEDOT droplet/cavity sidewall interface as well as droplet impact velocity Vd on the transient deposition process in the micro cavity. Impact inertia was studied by varying the droplet Weber number from 30.3 to 42.6. The surface characteristics are explored by choosing thetas_s of 10deg, 30deg, 50deg, 70deg, 90deg, and 110deg. The influences of impact inertia are also examined by increasing Vd from 2.0 to 12.0 m/s at 2.0 m/s interval. The computed results are found in good agreement with the experimental ones. For the first time, critical Weber numbers have been found relating to the ability of the droplet to wet the side walls and fill a microcavity with a uniform film. The results are also new in terms of the identifications of the critical contact angle (thetas_s)_C and critical impact velocity (Vd)_c. At (thetas_s)_C and at and beyond (Vd)_c, the formation of an intact flat film in the cavity is fulfilled.     

精密金属焊接坏点的视觉识别方法研究与仿真

研究高精密金属焊接坏点准确视觉识别的问题.由于高精密金属焊接坏点的颜色特征与金属本身特征相似,而在坏点很小并且与外部环境过于类似的干扰下,传统的基于像素差异的识别结果不精确,一旦焊接坏点分布的过于集中,干扰将更大,导致焊接坏点识别准确性降低.为解决上述问题,提出一种新的计算机视觉的高精密金属焊接坏点识别方法.采集高精密金属焊接坏点计算机视觉图像,针对金属图像进行特征提取,并对提取的特征进行离散小波变换处理,获取增强处理后的视觉图像.根据增强处理后的视觉图像特征值,获取高精密金属焊接坏点的分布密度,计算焊接坏点的空间位置,实现高精密金属焊接坏点识别.实验结果表明,利用改进算法进行高精密金属焊接坏点识别,能够提高识别的准确率,并且获取焊接坏点在高精密金属制品中的分布位置,为高精密金属制品的生产质量提供保障.     

RBF-NN-based model for prediction of weld bead geometry in Shielded Metal Arc Welding (SMAW)

Welding processes are considered as an essential component in most of industrial manufacturing and for structural applications. Among the most widely used welding processes is the shielded metal arc welding (SMAW) due to its versatility and simplicity. In fact, the welding process is predominant procedure in the maintenance and repair industry, construction of steel structures and also industrial fabrication. The most important physical characteristics of the weldment are the bead geometry which includes bead height and width and the penetration. Different methods and approaches have been developed to achieve the acceptable values of bead geometry parameters. This study presents artificial intelligence techniques (AIT): For example, radial basis function neural network (RBF-NN) and multilayer perceptron neural network (MLP-NN) models were developed to predict the weld bead geometry. A number of 33 plates of mild steel specimens that have undergone SMAW process are analyzed for their weld bead geometry. The input parameters of the SMAW consist of welding current (A), arc length (mm), welding speed (mm/min), diameter of electrode (mm) and welding gap (mm). The outputs of the AIT models include property parameters, namely penetration, bead width and reinforcement. The results showed outstanding level of accuracy utilizing RBF-NN in simulating the weld geometry and very satisfactorily to predict all parameters in comparison with the MLP-NN model.

     

Model reference adaptive controller for enhancing depth of penetration and bead width during Cold Metal Transfer joining process

In this paper, an adaptive control scheme is employed for joining Aluminium 6061 alloy sheets by Cold Metal Transfer (CMT) process. The transfer function model of the CMT welding system is derived using empirical equations. The CMT plant transfer function is estimated using system identification technique. For the estimated plant model, a conventional PID controller is initially designed by tuning the controller parameters. The designed control system is tested for its ability to control the welding current when short circuit phase and arcing phase are detected. Following the conventional PID controller, a Model Reference Adaptive Controller is implemented to maintain the welding current at desired range during melting and electrode wire short circuiting. The performance analysis for the proposed adaptive control scheme and the conventional PID controller is compared. The simulation results indicate that the conventional PID controller is unable to retrieve the desired current during short circuit phase and arcing phase. Nevertheless, the proposed MRAC for CMT process successfully maintains the welding current at the setpoint when subjected to arcing phases and short circuit respectively, while ensuring arc stability. The experimental validation is carried out in the CMT welding set up using the designed MRAC. The experimental results emphasize that the MRAC improves the welding performance by yielding good weld joints swiftly and enhanced quality besides minimizing the design complexities.     

多机器人协作无夹具焊接系统设计

与传统的单机器人系统相比,多机器人协作系统的设计存在诸如协作机器人之间的基坐标系标定、协作机器人末端位姿间的运动协调以及多机器人系统间的同步通讯控制等若干特殊性的关键问题.在初步论述多机器人协作系统设计中的若干问题的基础上,特别针对协作机器人间的基坐标系标定、工具手位姿约束分析和控制器通讯同步3个问题,进行了深入讨论,并介绍了实验室相关研究工作的结论.基于本文提供的解决方法,利用VA1400弧焊专用机器人和HP20通用型机器人基于主从式的分布控制结构组成了无夹具焊接实验系统,初步验证了提出的各问题解决方法的有效性.     

塑料熔焊封口机焊头温度PID控制的数字化实现

塑料熔焊封口机对焊头的温度非常敏感,要求温度波动小,控制系统惯性小。这对传统的温度控制提出了挑战。在研究PID算法的基础上,使用计算机手段将其数字化,设计出了针对塑料熔焊封口机的温度控制系统,经过实践证明可以达到塑料制品对焊头温度的要求。     

低温等离子体辅助聚乳酸表面接枝乳酸链球菌素 及抗菌性

该文主要通过低温等离子体处理聚乳酸薄膜,并研究了不同处理时间(0、15 s、30 s、45 s 和 60 s)后薄膜的表面形貌及亲水性。在此基础上,将低温等离子体处理后的聚乳酸薄膜浸泡到乳酸链球 菌素溶液中,对其抗菌性能进行测定。通过调节等离子体处理时间,可以明显改善聚乳酸薄膜的表面 亲水性及粗糙度。结果表明,随着处理时间的增加,聚乳酸薄膜表面粗糙度先增加后减小,接触角先 降低后增加。经过 60 s 低温等离子体处理的聚乳酸薄膜,浸泡乳酸链球菌素溶液进行接枝,可有效降 低单核增生李斯特菌的菌落总数。因此,低温等离子体处理聚乳酸薄膜,为其在食品抗菌包装领域提 供了一个非常好的思路。     

管道焊接机器人焊枪姿态智能控制系统

该文提出了一种基于专家系统的焊枪姿态智能控制系统,用以解决管道焊接机器人焊枪姿态控制问题。系统中采用ADXRS300微机械陀螺作为焊枪位置传感器,获取焊枪的空间位置后,通过专家系统的经验推理,得到合适的俯仰角,并采用DSP作为控制器驱动焊枪俯仰角步进电机动作,实现对焊枪俯仰角的实时调节。实验结果证明,利用专家系统对焊枪姿态进行智能控制是可行的,可以提高焊接质量。该系统具有广泛的应用前景。     

焊接温度场图像的获取及焊缝提取

叙述了焊接温度场检测系统的焊接温度场灰度图像的获取，简述小波变换用于检测边缘的原理，论述了小波变换在焊接温度场灰度图像中识剐焊缝位置的具体方法。研究结果证明：该焊缝识剐的方法优于传统的检测方法，具有更好的去噪性能，可以准确地识别焊缝的位置。     

采用平行缝焊机封盖的工艺研究

本文主要介绍利用平行缝焊机封盖的工艺;并对调试过程中出现的盖板对位不准和漏气问题进行了分析和研究。     

气体密封性能检测仪设计

针对压差法气体密封性能检测设计的缺点,提出容腔压降方案,可以避开温度扰动障碍,满足精度要求。     

弧焊机器人工具标定与接触寻找焊缝实现

机器人工具标定就是确定工具坐标系相对于末端坐标系的转换矩阵,标定的准确度对机器人后续操作有很大影响。提出了一种工具坐标系标定方法,并在昆山一号机器人研发的过程中试验。在标定完成后实现了接触寻找焊缝,针对特定的焊接接头,使用焊枪末端或侧边触碰工件,记录触碰点的坐标,通过记录点的坐标值自动确定焊缝的始末端和焊缝的轨迹,减少了焊接每个工件均需示教始末端的过程,以及示教不准确带来的误差。     

温度变送器热电偶冷端补偿电路的设计

用ＡＤ５９０温度－电流传感器进行冷端补偿，同时考虑了热电偶的非线性补偿，设计出较实用的温度变送器。     

柱式称重传感器密封性改进

应变式称重传感器是电子衡器称量系统的核心元器件,传感器的准确度和稳定性直接影响电子衡器称量系统的准确度和稳定性,称重传感器的稳定性尤为重要。而影响传感器稳定性最主要的因素就是传感器的密封性,文中给出了提高传感器的防护和密封性,从而有效保证传感器稳定性的几种方法。     

双疏纳米涂层改善轴承密封性能技术研究

为了提升滚动轴承密封性能,提出了采用双疏纳米涂层改善滚动轴承密封的方案并进行了系统的试验研究。首次独立研发了可实时光学监测润滑剂端泄的密封试验机。采用水和不同粘度的甘油水溶液作为润滑剂,对比研究了不同转速下双疏纳米涂层对密封性能的改善效果。试验结果表明,在一定的转速范围内,这种双疏纳米涂层都具有一定的防侧泄性能;在速度较低时纳米涂层可以显著提升密封性能,随着速度提高,密封性能下降。     

Sealing of adhesive bonded devices on wafer level

In this paper, we present a low temperature wafer-level encapsulation technique to hermetically seal adhesive bonded microsystem structures by cladding the adhesive with an additional diffusion barrier. Two wafers containing cavities for MEMS devices were bonded together using benzocyclobutene (BCB). The devices were sealed by a combined dicing and self-aligning etching technique and by finally coating the structures with evaporated gold or PECVD silicon nitride. The sealing layer was inspected visually by SEM and helium leak tests were carried out. Devices sealed with silicon nitride and with known damage of the sealing layer showed a helium leak rate of about 7–14 times higher than the background level. Devices of the same size without damage in the sealing layer had a leak rate of only 1.5 times higher than the background level. Experiments with evaporated gold as cladding layer revealed leaking cracks in the film even up to a gold thickness of 5 μm. The sealing technique with silicon nitride shows a significant improvement of the hermeticity properties of adhesive bonded cavities, making this bonding technique suitable for applications with certain demands on gas-tightness.