【作者】 王大勇；

【导师】 吴林；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2011， 硕士

【摘要】 铝合金自动化焊接时常出现变散热、变间隙等情况,采用恒规范焊接时无法得到均匀一致的背面熔宽,使铝合金焊接产品的强度等性能较差,因此需要对背面熔宽进行实时控制。此外,大尺寸工件焊接时常需要焊枪运动,由此带来了传感器和焊枪同步运动的问题。本文针对以上两个问题,利用背面熔池在图像中位置的变化来闭环控制传感器运动,使传感器随焊枪同步运动,在此基础上对铝合金焊接过程中的背面熔宽进行控制。首先,搭建了传感器随动铝合金背面熔宽控制实验系统,该系统具有背面图像熔池及焊缝图像实时采集与处理、CCD随动控制和背面熔宽控制功能。其次,对铝合金背面熔池及焊缝图像的处理算法进行了研究。根据图像的特点,开发了熔池及焊缝边缘提取算法,该算法的步骤为最大方差阈值分割、二值开运算、二值闭运算和轮廓提取,在此基础上准确的提取了背面熔池位置信息和背面熔宽信息,为随动控制和背面熔宽控制奠定了良好的基础。再次,研究了背面传感器随动控制和背面熔宽控制的方法。设计了PID控制器进行背面传感器随动控制,并用试凑法对PID参数进行了整定,取得了很好的随动控制效果。由于焊接过程具有强非线性等特点,本文用Matlab模糊逻辑工具箱设计模糊控制器对背面熔宽进行控制,模糊控制器的输入为背面熔宽误差及误差的变化,输出为焊接速度。用面积法辨识了焊接速度与背面熔宽之间的二阶传递函数,以此为基础通过Simulink仿真对模糊控制器的控制效果进行了验证,并研究了量化因子和比例因子对控制性能的影响规律,为实际焊接过程的参数调节提供了指导依据。最后,同时进行了传感器随动控制实验和背面熔宽控制实验,实验结果表明:本文PID控制器控制效果很好,随动控制的稳态误差小于3.2mm。模糊控制器的适应性强,在背面熔宽设定值、工件形状、间隙大小等因素不同时,均能得到满意的背面焊缝成形,在参数选取适当的情况下,稳态误差不超过0.4mm。更多还原

【Abstract】 In aluminum alloy automatic welding process, heat dissipation conditions and butt gap are often different, it is difficult to guarantee the uniform of back weld width using constant parameters, this will reduce the performance of the weld, so it is necessary to study real-time control of back weld width. Besides, in process of large-size parts welding, welding torch need to move, in this case, CCD and welding torch must move synchronously. In order to solved these two problems, the change of back weld pool’s position was used to control sensor’s motion, on this basis, back weld width was controlled.Firstly, experimental system was built, this system can be used to capture and process the back weld’s image, on this basis, CCD’s motion and back weld width could be controlled.Secondly, back weld pool’s image processing algorithm was studied. According to the characteristics of the image, the molten pool and weld edge detection algorithm was developed, including maximum between-class variance method, binary opening operation method, binary closing operation method, contour extraction method. On the basis of above algorithm, back weld’s information about position and width was accurately extracted, laid a good foundation for servo control and control of back weld width.Thirdly, backside sensor’s servo control method and back weld width control method was studied. A PID controller was designed for backside sensor’s servo control, trial and error method was used in PID parameters tuning, a good control effect had been achieved. As welding process has strongly nonlinear characteristics, fuzzy controller was designed with Matlab fuzzy logic toolbox to control back weld width. Fuzzy controller’s input is back weld width’s error and error change, its output was welding speed. The second-order transfer function between back weld width and welding speed was identified by area method. On the basis of this transfer function, Simulink was used to verify fuzzy controller’s control effect, quantized factor and proportional factor’s impact effects to control performance were studied, through these works a basic guidance was provided for parameters’ adjustment during actual welding process.Finally, sensor servo control experiment and back weld width control experiment were done at the same time. Experiment results show that: PID controller works well, servo control’s steady-state error is less than 3.2mm.Fuzzy controller has a strong adaptability, when back weld width’s given value, parts’ shape, or gap size is different, good formation of weld can always be obtained, when parameters are suitable, back weld width control’s steady-state error is less than 0.4mm.更多还原