本文選題：視覺傳感 + 焊接偏差��； 參考：《華南理工大學(xué)》2016年博士論文

【摘要】：焊接自動(dòng)化和智能化是焊接技術(shù)的發(fā)展趨勢。為了克服示教再現(xiàn)型焊接機(jī)器人的不足,在焊接過程中利用傳感器和相關(guān)算法對(duì)焊接偏差進(jìn)行實(shí)時(shí)識(shí)別的同時(shí)對(duì)電弧進(jìn)行實(shí)時(shí)監(jiān)測,將大大提升焊接機(jī)器人的自動(dòng)化水平和智能化水平。本課題提出了不使用外部光源或?yàn)V光片,僅使用寬動(dòng)態(tài)范圍(Wide Dynamic Range,WDR)相機(jī)采集焊接圖像的視覺方案。在此基礎(chǔ)上構(gòu)建了熔化極氣體保護(hù)焊(Gas Metal Arc Welding,GMAW)機(jī)器人系統(tǒng),并開展了以下幾個(gè)方面的研究:(1)提出一種基于熔池中心的CO_2焊焊接偏差識(shí)別算法。利用基于快速混合重建的形態(tài)學(xué)算法自動(dòng)提取感興趣區(qū)域(Region of Interest,ROI)。開發(fā)了改進(jìn)的Canny算法得到坡口邊緣,并結(jié)合Hough變換和先驗(yàn)知識(shí)提取出坡口邊緣。為了擬合出熔池前端邊緣,依據(jù)熔池前端的外形類似橢圓的特點(diǎn),提出一種基于條件約束的自適應(yīng)差分進(jìn)化(Differential Evolution,DE)算法。求取熔池邊緣的兩個(gè)特征點(diǎn)并將其作為DE算法尋優(yōu)迭代的約束條件。然后,初始化其他三個(gè)未知點(diǎn)的種群并重新定義了評(píng)價(jià)函數(shù)和終止條件。變異因子可在算法進(jìn)化中自適應(yīng)地確定。在此基礎(chǔ)上計(jì)算得出焊接偏差。最后,通過試驗(yàn)對(duì)算法的魯棒性和精度進(jìn)行了驗(yàn)證并闡述了其實(shí)時(shí)性。(2)提出一種基于電弧頂端中心的MAG焊焊接偏差識(shí)別算法。開發(fā)了基本全局閾值和最佳全局閾值相結(jié)合的雙閾值方法分割出精確電弧區(qū)域。根據(jù)MAG焊射流過渡時(shí)電弧和焊絲末端的銜接關(guān)系,提出了焊絲中心線提取方法。在改進(jìn)Canny算法基礎(chǔ)上,結(jié)合MAG焊焊接圖像的特點(diǎn),對(duì)Canny算法進(jìn)行了進(jìn)一步的優(yōu)化、改進(jìn)和完善,提出一種基于Canny理論的坡口邊緣檢測算法。ROI經(jīng)高斯濾波后,分別計(jì)算x、y方向的梯度幅值。對(duì)x方向梯度幅值圖像進(jìn)行坡口邊緣提取而y方向梯度幅值圖像產(chǎn)生掩模,兩者做邏輯與操作后得到單像素坡口邊緣二值圖像。針對(duì)基于Canny理論的坡口邊緣檢測算法,提出了高斯濾波標(biāo)準(zhǔn)差的自調(diào)整方法。試驗(yàn)表明,基于電弧頂端中心的焊接偏差識(shí)別算法的精度滿足MAG焊焊縫跟蹤的要求。(3)闡述了導(dǎo)電嘴與工件之間的距離(Contact Tip to Work Distance,CTWD)與焊絲伸出長度變化的基本原理。運(yùn)用CTWD的靜態(tài)數(shù)學(xué)模型和焊絲伸出長度模型分析了CTWD與焊絲伸出長度之間的關(guān)系,并設(shè)計(jì)CTWD階躍變化試驗(yàn)進(jìn)行了驗(yàn)證。分析了噴嘴邊緣在焊接圖像中的特征并提出了焊絲伸出長度檢測算法。試驗(yàn)表明,算法可有效檢測焊接圖像中的焊絲伸出長度,精度可滿足GMAW機(jī)器人焊接過程中保持CTWD基本恒定的要求。(4)在射流過渡、射滴過渡和旋轉(zhuǎn)射流過渡三種不同的熔滴過渡過程中分別采集了包含圓錐形、鐘罩形和扭曲束形三種不同電弧形態(tài)的焊接圖像。在運(yùn)用改進(jìn)Canny算法提取非閉合電弧邊緣的基礎(chǔ)上,提出一種改進(jìn)的快速行進(jìn)法(Fast Marching Method,FMM),重新定義了FMM的速度函數(shù)和停止準(zhǔn)則,從而獲得了完整的電弧形態(tài)。提出一種基于標(biāo)記圖的識(shí)別方法對(duì)三種電弧形態(tài)進(jìn)行識(shí)別。試驗(yàn)表明,電弧形態(tài)提取算法和電弧形態(tài)識(shí)別算法能夠在MAG焊過程中有效提取并識(shí)別電弧形態(tài),可應(yīng)用于焊接過程的電弧實(shí)時(shí)監(jiān)測。最后,通過卡爾曼濾波算法利用前一幀的偏差預(yù)測值和當(dāng)前幀的偏差識(shí)別值來估計(jì)最優(yōu)焊接偏差值。結(jié)果表明,焊接偏差的最優(yōu)估計(jì)值更接近焊接偏差預(yù)設(shè)值。以GMAW機(jī)器人系統(tǒng)為平臺(tái),分別針對(duì)CO_2焊和MAG焊設(shè)計(jì)了二維、三維焊接軌跡和電弧監(jiān)測試驗(yàn),驗(yàn)證了焊接偏差實(shí)時(shí)識(shí)別、CTWD調(diào)節(jié)和電弧監(jiān)測在自動(dòng)化焊接過程中的有效性。
[Abstract]:Automation and intelligentization of welding is the development trend of welding technology. In order to overcome the shortage of teaching and reproducing welding robot, the real-time recognition of welding error and real-time monitoring of welding arc by sensors and related algorithms in the process of welding will greatly improve the automation level and intelligent level of the welding robot. The project proposes a visual scheme that uses a wide dynamic range (Wide Dynamic Range, WDR) camera to collect welding images without using an external light source or filter. On this basis, a melted polar gas shielded arc welding (Gas Metal Arc Welding, GMAW) robot system is constructed, and the following studies are carried out: (1) a kind is proposed based on the molten pool. The CO_2 welding error recognition algorithm of the heart is used to automatically extract the region of interest (Region of Interest, ROI) based on the fast hybrid reconstruction algorithm. The improved Canny algorithm is developed to get the edge of the slope, and the edge of the slope is extracted with the Hough transformation and prior knowledge. An adaptive differential evolution (Differential Evolution, DE) algorithm based on conditional constraints is proposed. The two feature points of the edge of the pool are obtained and the constraint conditions for the optimization of the DE algorithm are obtained. Then, the population of the other three unknown points is initialized and the evaluation function and the terminating condition are redefined. The difference factor can be adaptively determined in the evolution of the algorithm. On this basis, the welding deviation is calculated. Finally, the robustness and accuracy of the algorithm are verified by the experiment and its practicality is expounded. (2) a method of identifying the MAG welding deviation based on the center of the arc is proposed. The basic global threshold and the best global threshold are developed. The precise arc region is segmented by the combined double threshold method. Based on the connection between the welding wire and the end of the welding wire, the method of extracting the center line of the welding wire is proposed. On the basis of the improved Canny algorithm and the characteristics of the welding image of the MAG welding, the Canny algorithm is optimized, improved and perfected, and a kind of Can based on the Can is proposed. The slope edge detection algorithm of NY theory.ROI calculates the gradient amplitude in the direction of X and y after Gauss filtering. The masks are generated for the gradient edge of the X direction gradient image and the gradient amplitude image of the Y direction. Both of them get the two value image on the edge of the single pixel slope after the logic and operation. For the edge detection based on the Canny theory, the slope edge detection based on the Canny theory is detected. The self adjustment method of the Gauss filter standard deviation is proposed. The experiment shows that the accuracy of the welding deviation recognition algorithm based on the center of the arc top satisfies the requirements of the MAG welding seam tracking. (3) the basic principle of the distance between the guide nozzle and the workpiece (Contact Tip to Work Distance, CTWD) and the elongation of the welding wire is described. The application of CTWD The relationship between CTWD and the elongation length of welding wire is analyzed by the static mathematical model and the length model of welding wire. The CTWD step change test is designed and verified. The characteristics of the nozzle edge in the welding image are analyzed and the detection algorithm of the length of the welding wire is put forward. The experiment shows that the method can effectively detect the welding wire in the welding image. The length and precision can satisfy the requirement of maintaining the basic CTWD constant during the welding process of the GMAW robot. (4) in the three different droplet transition processes of the jet transition, the droplet transition and the rotating jet transition, the welding images containing three different arc shapes including conical, bell shaped and twisted beam are collected. The improved Canny algorithm is used to extract the welding images. On the basis of the edge of unclosed arc, an improved fast moving method (Fast Marching Method, FMM) is proposed. The velocity function and stopping criterion of FMM are redefined, and the complete arc shape is obtained. A recognition method based on the label graph is proposed to identify three kinds of electric arc states. The arc shape recognition algorithm can effectively extract and identify the arc shape during the MAG welding process, and can be applied to the arc real-time monitoring of the welding process. Finally, the optimal welding deviation value is estimated by using the Calman filtering algorithm and the deviation recognition value of the previous frame. The results show that the optimal estimation value of the welding deviation is shown. It is closer to the preset of welding deviation. Based on the GMAW robot system, the two-dimensional, three-dimensional welding trajectory and the arc monitoring test are designed for the CO_2 welding and MAG welding respectively. The validity of the real-time identification of the welding deviation, the CTWD regulation and the arc monitoring in the automatic welding process are verified.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TP391.41;TP242

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