焊接工艺解耦控制机理及执行机构与控制策略的研究

An innovative method is proposed to decouple the welding current, voltage and droplet mass in GMAW. In particular, it uses joint actions from two piezoelectric actuators to adjust the position of the wire in relation to the torch at ultra-high or moderate speed. An ultra-high adjustment away from the work-piece generates an ultra-high acceleration to detach the droplet despite the actual values of the current and droplet mass. A moderate speed allows the arc length, thus the arc voltage, be adjusted at relatively high speed rather than through the relatively slow feeding-melting balance process. The coupling among the welding current, voltage and droplet mass in conventional GMAW needed to effect the metal transfer is thus fully decoupled. The proposed research will analyze the mechanism behind this innovative GMAW decoupling method, mathematically model the components in the decoupling GAMW system, establish the dynamic model for the entire system, formulate the effective operation of the system as a feedback control problem, and solve the control problem using an advanced model predictive control algorithm. To those ends, an experimental system will be established using the proposed actuators, established models, and developed model predictive control algorithm. The established experimental system will also be used to experimentally demonstrate the effectiveness of the proposed decoupling method.

项目拟从控制学及新型执行机构应用的角度研究GMAW解耦控制原理和实现方法。基于常规GMAW系统分析，将其分解为熔滴过渡与焊接电流、电压解耦和在恒流源模式下实现弧长自由调节。基于对熔滴过渡的研究，提出并验证了采用压电材料进行熔滴过渡和弧长控制的可行性。建立GMAW解耦控制的系统动态模型，并提出采用模型预测控制的方法来实现。研制一套实验系统并进行解耦控制实验，以检验上述原理分析、系统设计及控制方法的有效性和实用性。项目的意义是：从控制学角度在原理上解释GMAW解耦控制的可行性，并通过设计压电执行器，建立控制模型，研究解耦算法加以实现。研究GMAW的解耦控制系统可以扩展GMAW工艺区间，提高焊接质量。

熔滴过渡与弧长控制是GMAW焊接工艺的主要挑战，焊接工艺稳定性、飞溅的形成以及焊接的能量输入、焊缝成型等都与其关系紧密。项目通过采用压电执行器对熔滴施加机械力的方式，实现了在焊接电流不变的前提下熔滴的小颗粒过渡。在压电执行机构设计实现的基础上，完成了执行机构的特性测试与弧长控制系统的动态分析、执行器运动协同性分析与优化设计、系统研制及GMAW解耦控制的试验研究等工作。熔滴过渡的高速摄像研究表明，熔滴的加速推进与突然减速是熔滴过渡发生的驱动力。该研究为研究电弧空间的电场分布以及新型的直线电机复合送丝工艺研究奠定了基础，同时为脉冲GMAW的研究指明了方向，在相关的合作研究中取得了丰硕的成果。