【作者】 刘威；

【导师】 徐国成； 黄治轶；

【作者基本信息】 吉林大学 ， 工程硕士（专业学位）， 2024， 硕士

【摘要】 电阻点焊作为一种常见的金属焊接工艺,因其快速高效、成本低廉、适用性强等优点,在汽车、航空航天、船舶制造以及电子领域得到了广泛的应用。而点焊电极在焊接过程中起着传导焊接电流、对工件施加机械压力及对工件焊接区起散热及控制温度场的作用,电极对中状态不良及电极端面的不平整会导致多种焊接质量缺陷,影响焊接质量。目前,对电极对中性及点焊电极端面磨损状态的检测评估主要是依靠简单量具及人工经验,不仅效率低,评估的可靠性亦较低,对点焊质量控制及保障质量的稳定性带来较大的不利影响。而目前在工程上对电极对中性及电极端面的自动化检测设备尚未得到应用。因此设计一种可以快速检测点焊上、下电极的同轴度及其位姿与点焊电极表面状态的装置及检测方法十分有必要。本文设计了一种电阻点焊电极位姿及端面自动检测系统,目的是在实际工程中对电阻点焊上、下电极的对中性及点焊电极磨损状态进行在线检测与评估。该系统主要由工业机器人、二维激光测距传感器及工业计算机等组成。检测软件主要包括检测控制、机器人通讯、传感器通讯等模块。其中,二维激光测距传感器装配于工业机器人机械臂末端法兰盘上,通过示教编程器控制工业机器人对被测电极及电极端面进行非接触式扫描检测,工业计算机与工业机器人及二维激光测距传感器建立通讯联系,并获取其检测数据。通过手眼标定实验得到的手眼标定矩阵将所得二维激光测距传感器数据与工业机器人偏移量及欧拉角转换为工业机器人基坐标系下的坐标,以便于后续的数据处理。通过对同一位姿的电极对与同一电极端面的不同角度的检测,获取其三维坐标并输出其检测外观的三维坐标。根据二维激光测距传感器发射的激光在被测电极对表面总是表现为圆弧形这一特性,拟合所检测的每条圆弧并计算其中心点,可知中心点的连线即为被测电极的轴线。通过计算上、下电极轴线的相对空间角度及位置可知上、下电极的空间位置姿态,通过比较不同检测角度下上、下电极的相对空间角度及位置,可知其相差在误差允许的范围内,认为在不同的检测角度下对同一电极对的位姿的检测结果是相同的。通过对同一电极端面不同角度的检测,将所得的检测数据对电极端面进行拟合,计算电极端面的直径及表面粗糙度,并比较不同检测角度所计算的电极端面的直径及表面粗糙度,在其相差在误差允许的范围内,认为在不同的检测角度下对同一电极端面的检测结果是相同的,实现了电极姿态及点焊电极磨损评估的高效、自动化检测,提高点焊质量控制水平及工作效率。更多还原

【Abstract】 As a common metal welding process,resistance spot welding has been widely used in automobile,aerospace,shipbuilding and electronic fields because of its advantages of high speed,high efficiency,low cost and strong applicability.In the welding process,the spot welding electrode plays the role of conducting welding current,exerting mechanical pressure on the workpiece,radiating heat to the welding area of the workpiece and controlling the temperature field.Poor electrode centering state and uneven electrode end face will lead to various welding quality defects and affect the welding quality.At present,the detection and evaluation of electrode alignment neutrality and end-face wear of spot welding electrode mainly rely on simple measuring tools and manual experience,which not only has low efficiency,but also has low reliability,which has a great adverse impact on spot welding quality control and quality stability.At present,the automatic detection equipment for electrode pair neutrality and electrode end face has not been applied in engineering.Therefore,it is necessary to design a device and detection method that can quickly detect the coaxiality,posture and surface state of the upper and lower electrodes in spot welding.In this paper,an automatic detection system for position,posture and end face of resistance spot welding electrode is designed,aiming at on-line detection and evaluation of the alignment of upper and lower electrodes and the wear state of spot welding electrode in practical engineering.The system is mainly composed of industrial robots,two-dimensional laser ranging sensors and industrial computers.The detection software mainly includes detection control,robot communication,sensor communication and other modules.Among them,the two-dimensional laser ranging sensor is assembled on the flange at the end of the mechanical arm of the industrial robot,and the industrial robot is controlled by the teaching programmer to carry out non-contact scanning detection on the electrode to be measured and the electrode end face.The industrial computer establishes communication with the industrial robot and the two-dimensional laser ranging sensor and obtains its detection data.The hand-eye calibration matrix obtained by hand-eye calibration experiment converts the obtained two-dimensional laser ranging sensor data,industrial robot offset and Euler angle into coordinates in the industrial robot base coordinate system,which is convenient for subsequent data processing.By detecting the different angles between the electrode pair with the same posture and the end face of the same electrode,the three-dimensional coordinates are obtained and the three-dimensional coordinates of the detection appearance are output.According to the characteristic that the laser emitted by the two-dimensional laser ranging sensor always appears as a circular arc on the surface of the electrode pair to be measured,each detected circular arc is fitted and its center point is calculated,and it is known that the connecting line of the center point is the axis of the electrode to be measured.By calculating the relative spatial angles and positions of the axes of the upper and lower electrodes,we can know the spatial positions and postures of the upper and lower electrodes.By comparing the relative spatial angles and positions of the upper and lower electrodes at different detection angles,we can know that the difference is within the allowable error range,and it is considered that the detection results of the same electrode pair are the same at different detection angles.By detecting the same electrode end face at different angles,the obtained detection data are fitted to the electrode end face,and the diameter and surface roughness of the electrode end face are calculated.By comparing the diameter and surface roughness of the electrode end face calculated at different detection angles,it is considered that the detection results of the same electrode end face at different detection angles are the same,which realizes the efficient and automatic detection of electrode posture and electrode wear evaluation in spot welding,and improves the quality control level and work efficiency of spot welding.更多还原