基于DSP波控CO,2弧焊电源控制系统的研究.pdf

华 中 科 技 大 学 硕 士 学 位 论 文 I摘 要 随着科学技术在焊接领域应用的不断深入数字化技术和波控技术在弧焊电源中的应用已成为新型焊机的主要发展方向 本文以表面张力熔滴过渡STT为基本指导思想应用数字信号处理技术对CO2气体保护焊短路过渡用电源的控制系统加以研究根据 CO2焊短路过渡过程的特点把其细分成七个阶段在颈缩形成过程中提高电流促使颈缩形成而在短路过渡后期降低电流使液桥在低能量条件下爆破完成较小飞溅的短路过渡在此过程中通过数字信号处理器TMS320LF2407A DSP对焊接电流电弧电压实时采样对采样值进行分析处理最后控制输出符合于短路过渡特点的电流波形 表面张力熔滴过渡 STT中各阶段状态的特征值的提取和判定是制约其发展的一大瓶颈随着焊接过程测试技术的发展人们认识到焊接电流电弧电压是各种电弧物理现象的丰富信息的载体本文基于数据采集卡 PCL_818L应用 Visual C++技术开发了一套信号采集信号处理的测试分析软件该软件对电弧电信号的瞬时I-U 图电压一阶微分电压二阶微分电压和电流的概率密度分布电弧功率和熔滴过渡频率以及短路时间燃弧时间熔滴过渡周期等参数进行了分析瞬时 I-U图能很好地反映短路过渡中的小概率不规则现象而焊接电压的概率密度分布图短路过渡时间的统计分析过渡频率分布图都能够很好地反映短路过渡的规则性和稳定性利用这些模块可对 CO2气体保护焊的熔滴过渡电弧特性进行分析从而提取有价值的焊接电弧特征信息 借助电弧电信号的测试分析软件探讨了 CO2气体保护焊短路过渡过程的控制策略并提出了以下两套控制策略策略一利用电弧电压的起伏变化来正确地检测 CO2气体保护焊短路时刻和燃弧时刻同时通过恰当的设定各阶段的时间参数和控制算法来实现对应阶段的电流波形控制策略二利用电弧电压的起伏变化来正确地检测 CO2气体保护焊短路时刻和燃弧时刻同时用短路峰值电流和焊接基值电流分别来标示液桥爆破段开始和回复段结束经各阶段的对应算法来实现对各阶段华 中 科 技 大 学 硕 士 学 位 论 文 II的电流波形控制 控制系统芯片采用数字信号处理器 TMS320LF2407A主要用到其 A/D 转换接口和事件管理器中 PWM 输出等功能软件技术采用了中断服务技术及时处理各类故障和实时控制程序结构采用子程序编程思想使其清晰明了便于调试修改提高系统的可移植性 本文设计了基于 DSP 分析 CO2焊接过程的试验平台通过该平台可以判断 DSP的控制效果还设计了电弧电压和焊接电流的预处理电路其线性关系良好能灵敏的检测短路过渡中各阶段的焊接电流和电弧电压使电弧电信号进数据采集卡和DSP 时不失真 示波器标准方波信号模拟弧压进行的仿真试验和实际焊接试验都证明了控制思想合理且总体方案有效可行本研究对波控 CO2弧焊电源的研究而言是一种新的有益的尝试 关键词CO2弧焊电源 波控 表面张力熔滴过渡STT 数字信号处理器DSP 脉宽调制PWM 华 中 科 技 大 学 硕 士 学 位 论 文 IIIABSTRACT With the further application of advanced technology in the welding field, the research of digital technology and wave controlled technology in new welding machine have been exploited two mainstream directions. In this paper, the control system of the power source for CO2 short circuiting transfer is researched which is based on the technology of STT (the Surface tension transformation) and DSP (digital signal process). In terms of the character of short circuit transfer of CO2 welding, the process is fractionalized into seven subsections. During the neck of metal becoming, rising the current make it coming into being. And at the later of short-circuiting transfer, the welding current is declined, as makes the bridge destroyed at the low energy and finishes the transfer without splash. During the process, the real time current and voltage values information are obtained and sent to the DSP (digital signal processor) for processing, then the wave of current is produced by the control of DSP at the output end that is suit for the short-circuiting transfer. The problem of the accurate capture and estimate of each subsection’s characteristic signal is a bottleneck in the development of the Surface tension transformation. With the development of detecting technology in welding process, it has been known that welding current and arc voltage carry about abundance information of various arc physics phenomena. This paper designs a welding arc information testing and processing system based on data acquisition card PCL_818L, which can deal with data acquisition and signal analysis processing in Visual C++. The system has a friend by interface and is very easy to use. It contains instantaneous I-U, differential analysis, welding voltage and current probability density distribution diagram, arc power, metal transfer frequency distribution diagram and the time of metal transfer period etc. Instantaneous I-U diagram can be used to find the irregular metal transfer. Welding voltage probability density distribution 华 中 科 技 大 学 硕 士 学 位 论 文 IVdiagram, the variance of metal transfer period and metal transfer frequency distribution diagram can be used to judge the stability and the regularity of metal transfer. By these functions, the arc character of the CO2 droplet transfer welding process can be analyzed so as to extract more valuable information. In this paper, basing on the welding arc information testing and processing system, the control project of short-circuiting transfer is probed and two control projects are obtained. One is that at the time of day of short circuit, arc and other subsections, the arc values are exactly checked in real time and processed by DSP, then, initializing the time constant of per subsection so as to realize the control. The other is that at the time of day of short circuit, arc and other subsections, the arc values and the welding current are exactly checked in real time and processed by DSP. The out character of the power source that comes up to every subsection of short circuit transfer of CO2 welding is obtained. In software technology, interrupting service technology is used, which can disposal every kind of malfunction in time and real time control. The structure of software adopts the subroutine thinking which is in focus and easy to debug and modify and improve the system stability and replantation. The estimation system of experimentation, which can estimate the effect of DSP control in CO2 welding, is designed in the paper. The pretreatments of welding current and arc voltage, which is good linearity and sensitive to inspect welding current and arc voltage so as to insure that welding current and arc voltage are not distortion before 。