316LVM不锈钢电阻点焊信息检测分析及质量实时控制研究

发布时间：2018-10-10 14:30

【摘要】：电阻点焊过程由于其形核时间极短且伴随大量不确定因素的存在,具有高度非线性、多变量耦合并处于封闭状态无法观测、焊接特征信号提取困难等特点,其质量实时控制是长期存在的难题。本文以医学植入用316LVM不锈钢的点焊过程为研究对象,通过对不同影响因素条件下的多种过程信息进行分析,探讨适应面更广的电阻点焊电极位移质量控制新方法。加热因素和机械因素是影响电极位移的两大主要因素,其中机械因素包括施加的焊接压力和工件约束条件。然而,传统的电极位移控制方法没有考虑机械因素的影响,在实际应用中受到较大制约。针对该情况,本文首先基于伺服电机及DSP控制,设计了电阻点焊伺服加压系统。通过机构分析与优化、系统参数分析与建模、合理的控制方式等,实现了电极快速下压、柔性接触和压力的快速稳定控制。针对机械约束条件变化下的电极位移控制,本文设计了焊接电流、电极间电压、焊接压力和电极位移等电阻点焊多信息检测系统,系统地测试了不同影响因素下的过程信息,探讨了基于动态信息识别机械约束条件的可行性和方法。结果表明,在小边距、工件翘曲等主要机械影响因素存在时,电极间电压、动态电阻和电极位移的综合信息具有可区分的特征,通过对这些信息的深入分析研究,本文提出了小边距和工件翘曲的识别方法,获得了小边距焊接的信息特征和规律。在此基础上,提出了基于电极间电压和电极位移信息的点焊质量实时控制方法。该方法利用电极间电压和位移信息对工件的机械约束变化进行在线辨识,在实际控制中通过跟踪相应机械约束条件下的标准位移对焊接过程进行控制。基于S-Function以及NARX神经网络算法,利用Simulink建立模型进行模拟仿真。结果表明,对于热影响因素以及机械影响因素,此控制方式能够使输出电极位移合理跟踪相应的参考位移,有效提高焊接质量。
[Abstract]:Because of the short nucleation time and the existence of a large number of uncertain factors, the resistance spot welding process is highly nonlinear, multivariable coupled and can not be observed in a closed state, and it is difficult to extract the welding characteristic signals. Real-time quality control is a difficult problem for a long time. In this paper, the spot welding process of 316LVM stainless steel for medical implantation is taken as the research object. Through the analysis of various process information under different influencing factors, a new method of displacement quality control of resistance spot welding electrode with wider adaptive surface is discussed. Heating factor and mechanical factor are two main factors which affect electrode displacement. Mechanical factors include welding pressure applied and constraint condition of workpiece. However, the traditional electrode displacement control method does not consider the influence of mechanical factors, so it is restricted in practical application. Aiming at this situation, this paper first designs the resistance spot welding servo pressurization system based on servo motor and DSP control. By means of mechanism analysis and optimization, system parameter analysis and modeling, and reasonable control methods, the rapid and stable control of electrode pressure, flexible contact and pressure is realized. Aiming at the control of electrode displacement under the change of mechanical constraint condition, this paper designs a multi-information detecting system for resistance spot welding, such as welding current, voltage between electrodes, welding pressure and electrode displacement, and systematically tests the process information under different influence factors. The feasibility and method of identifying mechanical constraints based on dynamic information are discussed. The results show that the comprehensive information of interelectrode voltage, dynamic resistance and electrode displacement can be distinguished when the main mechanical factors such as small margin and warpage of workpiece exist. In this paper, a method of identifying small edge distance and workpiece warpage is proposed, and the information characteristics and rules of small edge distance welding are obtained. On this basis, a real-time control method of spot welding quality based on the information of voltage and displacement between electrodes is proposed. Based on the information of voltage and displacement between electrodes, the mechanical constraints of workpiece are identified online, and the welding process is controlled by tracking the standard displacement under the corresponding mechanical constraints in the actual control. Based on S-Function and NARX neural network algorithm, Simulink is used to build a model for simulation. The results show that the control method can make the displacement of the output electrode track the reference displacement reasonably and improve the welding quality effectively for the thermal and mechanical factors.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG409

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