| 摘要: | 摘要 本論文描述自動遮蔽金屬電弧焊接控制系統的發展，它可以取代需要良好訓練的技工手動焊接操作，有幾種控制方法被應用到這個焊接系統控制上。 首先，我們推導此焊接控制系統的數學模型，它主要由一交流伺服馬達驅動之焊條進給控制機構所組成。當此一系統被當成焊條進給速度控制機構時，我們可以把它當成一階或二階動態系統，”Matlab IDENTIFICATION Tool Box”被用來估測此一階或二階動態系統的最佳合適的參數值。 之後，一個模糊增益程序PID控制器，調節一階的焊條進給控制機構，以控制電弧電流之大小，具有此種控制器，並以交流伺服馬達驅動的焊條進給控制機構，在操作期間，可以補賞熔掉的焊條部份，也可以穩定不必要的電弧長度變動，這種控制技術，很容易被應用到任何其他種類之消耗性電極的焊接過程。再者，適應性滑動模態控制器可以估測不定量的上界，並且利用調節焊條進給，以控制電弧電流的大小，我們以實驗檢測適應性滑動模態控制器的性能，模擬與實驗皆顯示滑動模態的確發生了。 滑動面可以被用來作為模糊控制器的前件部，以簡化其推論法則，對於這個適應性模糊滑動模態控制器，我們使用適應性定律，以更新模糊控制器的後件部，去逼近傳統滑動模態控制器的等量控制，調整焊條進給機構，以控制電弧電流的大小。此為我們用來控制SMAW焊接系統之控制器的一種，使用這種控制器，焊接電流的穩定性，焊珠的均勻性，焊道噴濺的降低量，皆大大的改善。 最後，介紹一個使用單一模糊輸入變數的適應性模糊控制器，基於FLC控制法則與具有邊界層厚度的普通SMC之間的相似性，與傳統之二維FLC的推論規則相比較，單輸入符號距離可以被用來降低FLC的推論規則數。適應性定律再一次地被使用，作為FLC的參數，以便逼近傳統滑動模態控制器的等量控制，以致於系統的狀態被迫趨近於零，因此，可以保證此一控制器的穩定性。此控制器的可行性及簡單性以SMAW系統的模擬加以驗證，結果顯示，期望的滑動模態特性的確發生了，實驗之結果顯示所提控制器的可行性，並且也顯示它能有效的執行焊接控制工作，此外，起弧亦非常地容易。 Abstract This thesis describes an automatic welding control system developed for alternating current shield metal arc welding (SMAW). It can replace manual operations which require a well-trained technician. Several methods are applied to control this SMAW welding system. First, we derive a mathematical model of the welding control system, which consists primarily of an electrode feed-rate mechanism driven by an AC servomotor. Both first-order and second-order dynamics are used to represent this mechanism, when we consider it for an electrode feed-rate velocity control system. The “Matlab IDENTIFICATION Tool Box” is used to estimate the best-fit values of the parameters of the welding control system, using first-order and second-order dynamics, respectively. A Fuzzy Gain scheduling PID controller can be used to modulate the rate of the first-order electrode feed-rate mechanism that regulates the arc current. The electrode feed-rate mechanism for this controller is driven by an AC servomotor which can both compensate for the molted part of the electrode and for the undesirable fluctuations of the arc length during welding operation. It can also be easily applied to any welding system where the electrode is consumed during the welding process. Furthermore, an adaptive sliding mode controller can estimate the uncertainty bounds, and modulate the rate of the electrode feed mechanism regulating the arc current. We also examine the performance of this adaptive sliding mode controller experimentally. The simulations and the experiments both show that the sliding mode occurs. The sliding surface can be used to as antecedent part to simplify the inference rule base for the fuzzy logic control (FLC). An adaptive fuzzy sliding mode controller uses an adaptive law to update the consequent part of the FLC to approximate the equivalent control of a conventional sliding mode control, modulating the rate of the electrode feeding mechanism that regulates the arc current. This is one method that we have applied to control the SMAW system. The stability of the arc welding current, the uniformity of the welding beads, and the reduction of spatter generation all can be dramatically improved by using this control method. Finally, in this thesis, we introduce an adaptive fuzzy logical controller design using a single fuzzy input variable signed distance . Based on the similarity between the control rule table of the prevalent FLCs and an ordinary SMC with a boundary layer, the single input variable signed distance can be used to reduce the number of fuzzy reasoning rules, compared to the conventional two-dimensional FLCs. Again, an adaptive law is used to obtain the FLC parameters, and is applied to approximate the equivalent control part of the SMC, so that the system states can be forced to zero, thus guaranteeing the stability of the adaptive fuzzy signed distance sliding mode control. The feasibility and the simplicity of this controller for an SMAW system is verified by a simulation. The results show that the expected approximation of the sliding property occurs. The experimental results verify the feasibility of the proposed controller and also show that it can effectively perform arc welding, as well as effectively initiate the welding arc. |
