Weld Tracking Research Articles

Welding deviation detection algorithm based on extremum of molten pool image contour

The welding deviation detection is the basis of robotic tracking welding, but the on-line real-time measurement of welding deviation is still not well solved by the existing methods. There is plenty of information in the gas metal arc welding(GMAW) molten pool images that is very important for the control of welding seam tracking. The physical meaning for the curvature extremum of molten pool contour is revealed by researching the molten pool images, that is, the deviation information points of welding wire center and the molten tip center are the maxima and the local maxima of the contour curvature, and the horizontal welding deviation is the position difference of these two extremum points. A new method of weld deviation detection is presented, including the process of preprocessing molten pool images, extracting and segmenting the contours, obtaining the contour extremum points, and calculating the welding deviation, etc. Extracting the contours is the premise, segmenting the contour lines is the foundation, and obtaining the contour extremum points is the key. The contour images can be extracted with the method of discrete dyadic wavelet transform, which is divided into two sub contours including welding wire and molten tip separately. The curvature value of each point of the two sub contour lines is calculated based on the approximate curvature formula of multi-points for plane curve, and the two points of the curvature extremum are the characteristics needed for the welding deviation calculation. The results of the tests and analyses show that the maximum error of the obtained on-line welding deviation is 2 pixels(0.16 mm), and the algorithm is stable enough to meet the requirements of the pipeline in real-time control at a speed of less than 500 mm/min. The method can be applied to the on-line automatic welding deviation detection.

Image processing of the weld pool and tracking of the welding line in pulsed MAG welding

In order to trace the welding line in the lap welding, weld pool in the pulsed MAG welding was taken by using the CCD camera. The weld pool was observed in the front and rear to the welding direction. The features of the weld pool were investigated to recognize the welding pool. The welding line was detected by using image processing and the digital controller was designed to trace the welding line.

The Method and Experimental Research on Seam Tracking and Dual-Beam Laser Welding for T-Type Welding Seam

Aimed at the goal of improving the quality and the efficiency of welding for T-type welding seam, This paper put forward a method to track the seam by using the vision sensor. Machine tool main motion trajectory is generated from the numerical model of the parts. The position of two welding torches are adjusted independently based on the machine tool main motion trajectory to ensure the welding precision. Two sets of adjusting mechanism are needed for T-type welding seam. The vision sensor measure the seam and pass the deviation signal to the CNC system. The CNC system adjust the position of the welding torch installed on the cross slide table to reach the goal of seam tracking and dual-beam laser welding for T-type welding seam. Practice shows that this system for T-type welding seam dual-beam laser welding is easy to operate and can improve the quality and the efficiency.

Weld Line Detection and Tracking via Spatial-Temporal Cascaded Hidden Markov Models and Cross Structured Light

Unlike weld seam detection in a welding process, weld line localization for inspection is usually performed outdoors and challenged by noise and variation of illumination intensity. In this paper, we propose a weld line localization approach for mobile platform via a cross structured light (CSL) device and spatial-temporal cascaded hidden Markov models (HMMs). A CSL device is designed to project cross red laser stripes on weldment surfaces and capture the weld convexity in video sequences. Stripe edge images are extracted and then a spatial HMM is designed to detect the regions of interest (ROIs) in the video frames. Detected ROIs in successive video frames are fed to the proposed temporal HMM as observations to track the weld lines. In this way, we incorporate both the spatial characteristics of laser stripes and the continuity of the weld lines in an optimal framework. Experiments show that the proposed approach can effectively reduce the influence of illumination and noise, contributing a robust weld line detection and tracking system.

Vision Control System of Pipe Welding Robot

The author of this article designs a non-track automatic pipe welding robot, which mainly studies the image processing system of visual welding tracking. With the requirement of various interference noise and tracking accuracy in the welding process, this study adopts structure light CCD sensor checking system and image acquisition card processing images of computer software, in which sample filtering, edge checking, contour tracking, laser centerlines selection and checking of its characteristics. This processing method has the advantages of good effect and speedy processing that is able to meet the timely requirement of tracking system.

Autonomous seam acquisition and tracking system for multi-pass welding based on vision sensor

Automatic welding technology is a solution to increase welding productivity and improve welding quality, especially in thick plate welding. In order to obtain high-quality multi-pass welds, it is necessary to maintain a stable welding bead in each pass. In the multi-pass welding, it is difficult to obtain a stable weld bead by using a traditional teaching and playback arc welding robot. To overcome these traditional limitations, an automatic welding tracking system of arc welding robot is proposed for multi-pass welding. The developed system includes an image acquisition module, an image processing module, a tracking control unit, and their software interfaces. The vision sensor, which includes a CCD camera, is mounted on the welding torch. In order to minimize the inevitable misalignment between the center line of welding seam and the welding torch for each welding pass, a robust algorithm of welding image processing is proposed, which was proved to be suitable for the root pass, filling passes, and the cap passes. In order to accurately track the welding seam, a Fuzzy-P controller is designed to control the arc welding robot to adjust the torch. The Microsoft Visual C++6.0 software is used to develop the application programs and user interface. The welding experiments are carried out to verify the validity of the multi-pass welding tracking system.

The Welding Track Planning and Motion Control of T-Type Tube Autowelding Machine

Combining with welding and numerical control technology, welding automation technology has brought the new development for welding equipment industry. This paper mainly aimed at automatic welding process needs for intersecting line of T-type tube, developed a practical automatic welding machine of T-type tube intersecting line, used the PCL893 movement control card as the core control unit, realized whole rotary feed of welding head and front and rear feed of the torch, etc. Integrating with mechanical cam and digital cam, the work achieved space fitting of saddle-shaped weld track so as to realize automatic welding process, imitate the manual welding process of space curve, reduce labor intensity, improve the efficiency of welding and quality.

Automatic Welding Method and Main Parameters Calculation of Tube Connected Five-Star Feet

In view of the situation that low quality and high cost of manual welded five-star feet, this paper proposed a new method to weld five-star feet. The method is compositing linear motion of welding torch and rotary motion of the workpiece to realize 3d welding track. After mathematic analysis and detailed calculation, the welding trajectory equation is obtained, and the speed matching relation between the welding torch and the workpiece is gained too.

The Study on Weld Tracking of TIG Based on Rotating Arc

Aimed at the situation that the welding voltage is easy to be disturbed by the voice outside, median filtering and average filtering are adopted to filtering signal of the voltage the rotating arc sensor collected in this paper. They can make the voltage waveform get obvious improvement. In order to get information which the welding torch deviated the welding seam more accurately, left and right integration, Characteristic Harmonics method and welding torch deviation recognition algorithm are adopted to identify the deviations in this paper. Finally compare the two kinds of identification deviation methods and obtain better welding torch deviated information.

Automatic Welding Track Detection for Welding Process by Machine Vision

The use of machine vision technology in the welding process has been developed along with the need for more consistent and more qualified welding results. The application of machine vision to perform object analysis without direct contact to the object itself making the whole processes fast while maintaining the accuracy. In this study, some image processing algorithms are combined which include : image enhacement (grayscaling and median filtering), edge detection, binarization, and Hough Transform for line detection. The candidate of welding tracks are produced through this standard algorithm. However, afterward, some modifications to the Hough transforms are carried to enable finding the actual welding tracks. The implemented method is capable of detecting the actual welding tracks and their appropriate welding path with accuracy not more than 0.9 mm.

Compact visual control system for aligning and tracking narrow butt seams with CO2 gas-shielded arc welding

In this paper, a visual control system is proposed to locate the start welding position and track the narrow butt welding seam in container manufacturing. It estimates the error between the welding torch and the welding seam with a camera and a panel computer. It adjusts the torch's position via a stepper motor to eliminate the error. A decision controller with three gates is designed to decide the working procedure. Feature extraction algorithms are designed according to the seams and pre-weld spots. The seam line and the position of the pre-weld spot are detected to locate the start welding position in initial aligning. Then the torch is aligned to the seam. In the welding stage, the reference feature is determined with many frames of images based on their statistical property. The current estimated feature is checked to ensure only normal features to be used for welding seam tracking. Experiments are well conducted to verify the effectiveness of the proposed system and methods.

Development of a precision welded impact sled test track

Finding an appropriate test track, especially suitable for higher velocity impacts, has become increasingly important in today’s sled testing environment. This paper describes the design and development of a new sled test track recommended for evaluating the crash safety performance of vehicle components and injury characteristics of impact biomechanics experimental samples. The extensive development programme considered the track foundation stability, rail grinding and welding techniques, track alignment procedures, and track precisions while meeting or surpassing the requirements of ECE R94 and higher velocity impacts. This facility was finally developed to be a continuously welded, high-precision, 82 metre impact test track. In order to examine its experimental precisions, the linearity, parallelism and flatness of this sled track were evaluated by means of precise surveying and mapping instruments, and six dummy 30 mph frontal impact tests were carried out. The experimental results point out the reliability of the precision welded impact sled test track.

Three‐dimensional weld seam tracking for robotic welding by composite sensing technology

PurposeThis paper aims to develop a method to achieve automatic robotic welding and seam tracking so that three‐dimensional weld seam could be tracked without teaching and good welding formation could be accomplished.Design/methodology/approachAdaptive image processing method was used for various types of weld seam. Also the relationship between welding height and arc signal was calibrated. Through the decomposition and synthesis, three‐dimensional space type weld seam could be extracted and tracked well. The workpiece without teaching was finally tracked precisely and in a timely way with use of the fuzzy controller.FindingsComposite sensing technology including arc and visual sensing had obvious advantages. Image processing method could be used for tracking plane weld seam efficiently while arc sensing could characterize welding height. Through the coupled controlling algorithm, arc sensing and visual sensing could be fused effectively.Research limitations/implicationsHow to couple information more accurately and quickly was still one of the most important problems in composite sensing technology.Practical implicationsComposite sensing technology could reduce costs to achieve weld seam instead such expensive device as laser sensor. The simulating parts of scalloped segment of bottom board for rockets were tracked in the project. Once more adaptive algorithms were developed, more complicated practical workpieces could be dealt with in robotic welding which promotes the application of industry robots.Originality/valueA useful method for three‐dimensional space type weld seam tracking without teaching was developed. The whole procedure of adaptive image processing method was simple but efficient and robust. The coupled controlling strategy addressed could accomplish seam tracking by composite sensing technology.

Welding Technique for New High Speed Railway Track Key Part

With the development of continuous welded rail (CWR) in China high speed railway, the innovative study has been carried out for the welding technique of track key part. Firstly, the paper introduces the traditional rail welding technique and its problems in China, and then, it proposes the new “SQ” gas welding technique on that basis, finally, it describes “SQ” gas welding technique in terms of technical feature, flow, economic benefit and application, which will be conductive to China railway track welding.

Low-Cost System for Weld Tracking Based on Artificial Vision

A laser-stripe system for the automation of welding processes in heavy industries is presented. Conventional methods use human intervention. A new solution using only common usage computer components has been developed, offering at least the same quality of performance at a low price, making laser systems without human intervention attractive for cost sensitive applications in heavy industries. A new system that guarantees satisfactory tracking results even when the welding gap geometry varies strongly or is distorted by noise has been developed.

On-Line Detection and Tracking Welding Control Technology of Thin-Walled Bellow

In order to improve the welding speed, quality and automation level of thin-walled bellow, on-line detection and tracking welding control technology is proposed which includes on-line detection system and tracking welding control system. Based on laser sensor, on-line detection system can rapidly filter the data, and the data is stored in a queue, the control system which is based on motion control card is developed by using ActiveX controls for programming, VB is used to develop the integrated user operating system, other control tasks are completely integrated on this system to realize real-time welding control bellow. Results showed that the system is reliable and effectively, the automation level of the bellow welding is greatly improved.

Study on Control Method of Smelting-Pool Width in TIG Welding Basded on Fuzzy Control

Aimed at the manufacture process of TIG( tungs-ten inert-gas) welding of copper-clad aluminum wire in enterprise, the methods of detecting and automatic tracking welding seam edge , detecting and automatic control smelting-pool width were studied and designed with fuzzy control in the paper. The experiment shows that the scheme has the advantages such as better control effect, high control precision and favorable stability.

Study on Sensor Design Technique for Real-Time Robotic Welding Tracking System

Based on visual measurement techniques, the real-time robotic welding tracking system achieves real-time adjustment for robotic welding according to the position and shape changes of a workpiece. In system design, the sensor design technique is so important that its performance directly affects the precision and stability of the tracking system. Through initiative visual measurement technology, a camera unit for real-time sampling is built with multiple-strip structured light and a high-performance CMOS image sensor including 1.3 million pixels; to realize real-time data process and transmission, an image process unit is built with FPGA and DSP. Experiments show that the precision of this sensor reaches 0.3mm, and band rate comes up to 10Mbps, which effectively improves robot welding quality.With the development of advanced manufacturing technology, it becomes an inexorable trend to realize the automatic, flexible and intelligent welding product manufacture. With the advantage of interchangeability and reliability, robotic welding can boost productivity, improve work condition, stabilize and guarantee weld quality, and realize welding automation of the short run products [1]. At present, robotic welding has already become the application trend of automatic welding technology. Traditional welding robots are play-back ones, which cannot adapt environment and weld distortion. Especially in the more and more extensive arc-welding course, the deficiency and limitation of play-back welding technology becomes more prominent because of changeable welding condition. It becomes one of the key technology influencing the development of modern robotic welding technology to eliminate or decrease uncertain influence on quality of welding such as changing welding condition etc [2]. Based on visual measuring principle, this text adopts active visual measuring technology, cooperated with high-speed image process and transmission technology to structure a tracking sensor, to realize real-time measurement of the space location and posture information of the work piece and reliable and accurate tracking of the welding seam.

Robot Calibration Using Iteration and Differential Kinematics

In the applications of seam laser tracking welding robot and general measuring robot station based on stereo vision, the robot calibration is the most difficult step during the whole system calibration progress. Many calibration methods were put forward, but the exact location of base frame has to be known no matter which method was employed. However, the accurate base frame location is hard to be known. In order to obtain the position of base coordinate, this paper presents a novel iterative algorithm which can also get parameters' deviations at the same time. It was a method of employing differential kinematics to solve link parameters' deviations and approaching real values step-by-step. In the end, experiment validation was provided.

Detection of weld position and seam tracking based on Kalman filtering of weld pool images

This paper presents a novel method of detection of weld and seam tracking during gas tungsten arc welding (GTAW). The weld position equations are established based on an estimation of the centroid position of the weld pool images. A Kalman filter (KF) is applied to the weld pool images from a visual sensor to recursively compute the solution to the weld position equations. The estimation of the state provided by a Kalman filter can be used to estimate the weld feature location on the image plane at the next sampling time and its uncertainty. This allows adjusting the welding torch position in real time, which may sensibly reduce processing time and improve seam tracking accuracy. The effectiveness of the proposed algorithm in the presence of weld pool image noise has been tested by the computer simulations and actual welding experiments. Also, the results of experiments have demonstrated the robustness of weld position detection for seam tracking.