人工神经网络电阻点焊质量监测模型的研究

利用 BP网络对电阻点焊的动态电参数进行融合处理 ,建立了以电阻点焊动态电参数为输入空间、点焊熔核尺寸为输出空间的电阻点焊质量智能监测模型。检验结果表明 :该模型的熔核尺寸预测精度完全满足工程实际需要 ;有很大的实用价值。在网络训练中采用综合改进的 BP算法 ,使得网络的训练效率大大提高     

基于声发射信号的铝合金点焊裂纹神经网络监测

铝合金热加工过程的冶金行为比较复杂,在电阻点焊快速加热和冷却条件下,极易产生裂纹缺陷。基于虚拟仪器技术,以Lab VIEW为软件平台,结合Matlab数值分析软件,构建了电阻点焊过程声发射信号采集分析及铝合金点焊裂纹监测系统。以2A12铝合金电阻点焊熔核冷却结晶过程,即点焊焊接循环维持阶段的声发射信号为研究对象,提取与声发射信号强度相关的振铃计数、能量、有效电压及5层小波分解125~250 k Hz频带能量系数4个特征参数作为输入矢量,裂纹作为输出矢量,建立3层BP神经网络铝合金点焊裂纹的监测模型,并利用测试样本对该模型进行验证。结果表明,裂纹监测的正确率达到89.1%,为监测铝合金电阻点焊裂纹提供了一种有效的方法。     

点焊电流有效值神经网络实时计算方法研究

通过理论分析,推导出交流电阻点焊电流有效值实时计算方程,建立了不同功率因数角的电流有效值系数K的神经网络计算模型,研究出电阻点焊电流有效值神经网络实时计算方法。在以DSP为核心的电阻点焊测控系统中实现了交流电阻点焊电流有效值实时计算。理论分析和实际检测表明,该方法的检测误差小于±0.9％,并且能够在二分之一周期内完成电阻点焊电流有效值的检测和计算。该方法的研究为电阻点焊质量的精确控制提供了可靠的保障。     

三层不锈钢板电阻点焊温度场数值模拟

根据三层不锈钢板电阻点焊熔核形成过程,建立了模拟三层板点焊温度场的轴对称有限元模型。在分析了三层板点焊的热电过程基础上,计算结果表明三层板点焊熔核初期是先形成包含中间板和上下工件/工件接触面的较小的熔核,随时间延长,熔核再沿轴向和径向逐渐长大的过程。通过试验验证表明,数值模拟结果与实际吻合良好。该模型为进一步的电阻点焊多层板的温度场和应力场分析提供了基础。     

一种新的电阻点焊方法

通过比较传统的电阻点焊及检验方法,提出了一种新的电阻点焊方法--Delta电阻点焊系统,并对其工作原理、过程和优点做了较详细的阐述.应用结果表明,该方法能在检验点焊质量的同时有效地提高焊点质量和工作效率.     

基于动态电阻理论的支持向量机点焊质量评估方法

电阻点焊过程是一个具有高度非线性、有多变量耦合作用和偶然不确定因素的过程,且熔核形成过程时间极短,因此在工程应用中,大多采用破坏性试验检验焊接质量。针对这一问题,利用电阻点焊过程中动态电阻理论,建立了支持向量机预测模型,对点焊进行无损检测、质量评估。分析了电阻点焊过程、动态电阻的变化过程和熔核的形成过程,进而建立了支持向量机回归预测模型。利用该数学模型预测熔核直径的大小,评估焊接质量。利用焊接电流、焊接时间等主要焊接参数构造支持向量机样本数据,预测熔核直径。通过试验仿真证明,该模型能够较为准确地预测熔核直径。     

重型卡车电阻点焊合梁的质量控制研究

电阻点焊具有低成本、高效率的特点,是重型卡车生产厂家进行纵梁两层板结构连接的主要工艺,一根纵梁上通常有18 ～30个焊点,焊接质量直接影响重型卡车的外观和使用性能.介绍了电阻点焊的原理,分析了焊接电流、焊接压力、焊接时间等参数对电阻点焊质量的影响.采用正交试验法对不同规格纵梁电阻点焊的焊接压力和焊接时间进行试验,对试验结果进行对比分析,确定不同规格纵梁在电阻点焊合梁过程中的最优焊接压力和焊接时间.通过对重型卡车电阻点焊合梁进行质量控制,提高了生产效率,降低了生产成本,并且提高了重型卡车车架的整体质量.     

六自由度点焊机器人运动学仿真

针对ABB的IRB-1400型六自由度点焊机器人,基于D-H方法建立其运动学方程,分析正问题,并通过拟定机器人点焊过程中的两个点推算运动学逆解.利用CATIA软件建立机器人几何模型,采用ADAMS仿真软件,对其运动学进行仿真分析.验证了几何模型,数学模型以及逆解的正确性,并得到机器人点焊过程中的空间轨迹.为对机器人进一步的动力学分析以及PTP轨迹控制奠定了基础.     

基于神经网络的点焊质量评估专家系统研究

简要介绍了专家系统在焊接中的应用与发展,给出了点焊过程神经网络训练模型,设计了点焊专家系统的神经网络模块,建立了Windows环境下的点焊质量评估专家系统,能够进行点焊质量的在线智能评估,为最终实现电阻焊单元制造的智能集成提供了技术基础。     

白车身焊接质量标准及其有效控制

电阻焊具有生产量大、成本低、效率高、低耗、焊接变形小、易操作、自动化程度高等特点,特别适合对汽车车身薄板覆盖件的焊接.尽管各种焊接工艺在车身中应用逐渐增多,但电阻点焊仍是车身制造的主要焊接工艺.在汽车工业车身制造过程中,电阻点焊约占90％.文中主要介绍了白车身电阻点焊的基本原理、点焊质量标准以及点焊工艺参数对焊接质量的影响等基本内容.     

Optimization of pulsed current in resistance spot welding of Zn-coated hot-stamped boron steels

Metallic coatings have been widely used for hot-stamped boron steel in automotive applications. Surface coating in hot-stamped boron steels has improved corrosion resistance. However, a thick coating layer degrades resistance spot weldability. In the case of a Zn-coated hot-stamped boron steel, the high contact resistance and material stiffness with low vaporization temperature of the alloyed layers result in a narrow current passage at the faying surface. Expulsion occurs at low current due to rapid heat development, resulting in a narrow weld current range. The pulsed current can control the heat input by applying a fast cool time during welding to improve the mechanical properties of the joint and acceptable current range. In this study, Zn-coated hot-stamped steels were resistance spot welded using various pulse current procedures, and welding condition was optimized via three pulsed current steps. Step 1: Contact area was controlled without nugget formation. Step 2: Nugget growth was minimized and contact area was maximized. Step 3: The maximum acceptable current range and nugget diameter were achieved. These welding conditions improved the acceptable current range and mechanical properties of spot welds due to increased spot weld size.

     

Quality monitoring based on dynamic resistance and principal component analysis in small scale resistance spot welding process

The present study aims at solving weld quality monitoring problem in small scale resistance spot welding of titanium alloy. Typical dynamic resistance curves were divided into several stages based on the weld nugget formation process. A smaller electrode force or lower welding current was found to promote the initial resistance peak. The bulk material heating stage could not be detected under very high welding current condition. Electrode force effect on dynamic resistance and failure load was much smaller than that of welding current. Principal component analysis was made on discrete dynamic resistance values. The first principal component was selected as independent variable in regression analysis for quality estimation. A back propagation neural network model was then proposed to simultaneously predict the nugget size and failure load. The electrode force, welding current, welding time, and first five principal components were designed as network inputs. Effectiveness of the developed model was validated through data training, testing, and validation. The realtime and online quality monitoring purpose could be realized.     

基于电极位移的点焊飞溅量化评价与自适应控制研究

飞溅是电阻点焊过程中一种常见的缺陷,严重的飞溅会显著影响焊接质量.针对典型的异常工况,通过飞溅金属量化分析与飞溅骤停实验,发现电极位移信号突变量与飞溅金属总质量之间线性相关,且电极位移信号突变量与飞溅前后熔核厚度减少量基本一致,因此电极位移信号突变量可以表征飞溅程度.在此基础上,提出了基于量化统计的点焊飞溅自适应控制策...     

点焊熔核形成过程的有限元模型

介绍了模拟点焊熔核形成过程的轴对称电、热、力学有限元模型。提出了点焊过程导电、传热和力学行为之间耦合作用的模拟方法和接触电阻分析方法。模型中也考虑了焊机特性、随温度变化的材料性能以及各种边界冷却条件的影响。试验验证结果表明，数值模拟结果与实际吻合良好。该模型提供了一种有效的点焊过程理论分析手段。     

逆变点焊电源模糊神经网络自适应控制模型研究

研究了逆变点焊电源恒流自适应控制的模糊神经网络模型,设计了模糊神经网络结构。利用BP算法,采用先正弦函数输入后恒定输入的方法对网络进行了分段训练,并使用MATLAB语言,对系统进行了自适应控制和比例因子影响的仿真分析。结果表明,逆变点焊电源恒流自适应控制模糊神经网络,能够实现在线调整隶属函数参数,控制系统可快速感知外来干扰和过程变化,平均控制相对误差小于2.08%;比例因子的选取,对系统有很大影响,不同的比例因子在与训练好的网络结合进行控制时,系统控制效果不同。     

异质金属Fe-Ni电阻点焊熔核形成过程三维数值模拟分析

介绍了异质金属Ｆｅ－Ｎｉ电阻点焊熔核形成过程的三维电、热学有限差分模型,提出了异质金属点焊过程导电、传热三维耦合作用的模拟方法、接触电阻分析方法和产热结构处理方法。模型中也考虑了随温度变化的材料性能以及各种边界冷却条件的影响,模拟过程分析了改善异质点焊接头的办法。数值模拟结果与实验吻合良好。该模型提供了一种有效的异质点焊过程理论的分析手段。     

电阻点焊品质稳定性的控制方法

针对目前电阻点焊存在的焊接电流有时波动大、影响焊接品质稳定性等缺点,以汽车产业点焊工艺为例,介绍了在现有条件下,通过过程品质控制的方法及工艺措施的保证,解决点焊品质不稳定问题,并简单介绍了将来电阻点焊机的发展方向与品质控制的研究方向。     

不锈钢单侧磁控电阻点焊工艺研究

为提高单侧焊接接头的质量,减少焊接缺陷,基于传统双侧轴向磁化装置,设计了一种适用于单侧电阻点焊设备的单侧径向充磁磁控装置。通过与传统电阻点焊进行对比性实验,研究了传统焊点与单侧磁控焊点随焊接电流的变化规律,揭示了单侧磁控电阻点焊装置对焊点熔核形貌、熔核尺寸、微观组织、力学性能等方面的作用机制及改善效果,验证了单侧磁控电阻点焊工艺的可行性。     

Online nugget diameter control system for resistance spot welding

The aim of this paper is to provide an integrated real-time control system for resistance spot welding (RSW), which is capable of producing welds with predetermined nugget diameters. Nugget diameter is a commonly used criterion for estimating the weld quality; thus, the system can be used for online quality control of RSW. The proposed system consists of two parts: a constant current controller and an online nugget diameter estimator. The constant current controller is used to guarantee the consistency of the nugget formation and growth during the welding process, while the online nugget diameter estimator can be used as a sensor for online estimation of the nugget diameter. The proposed online nugget diameter estimator is a mathematical function of the heat energy absorbed by the weld, which is taken into account only after the time when the first melting point of a weld appears. This time can be obtained by means of the dynamic resistance curve with a high resolution. A mathematical model of the online nugget diameter estimator is proposed and realized based on the experiment results and mathematical analysis. The welding process would be terminated when the difference between the actual nugget diameter and the predetermined desired value is within a given tolerance. According to a series of experiments, the welds used in the experiments had nugget diameters, which were well within the limits and the errors were within the given tolerance.     

SPOT WELDING QUALITY FUZZY CONTROL SYSTEM BASED ON MULTISENSOR INFORMATION FUSION

The multisensor information fusion technology is adopted for real time measuring the four parameters which are connected closely with the weld nugget size(welding current,electrode displacement,dynamic resistance,welding time),thus much more original information is obtained.In this way,the difficulty caused by measuring indirectly weld nugget size can be decreased in spot welding quality control,and the stability of spot welding quality can be improved.According to this method,two-dimensional fuzzy controllers are designed with the information fusion result as input and the thyristor control signal as output.The spot welding experimental results indicate that the spot welding quality intelligent control method based on multisensor information fusion technology can compensate the influence caused by variable factors in welding process and ensure the stability of welding quality.