Seam Tracking System Research Articles

Study on Weld Seam Tracking System Based on Laser Vision Sensing

Seam tracking is a basic condition to ensure a fine welding shape. In order to meet this requirement, the researchers have put forward a variety of sensors and some of them have been applied to practice successfully, such as contact sensor, arc sensor and vision sensor. Laser vision sensor has been proven to be one of the most successfully technology for its many advantages. In this paper, based on laser visual sensing technology, a seam tracking system is established with an embedded microcontroller LPC1768. With this system, a real-time tracking algorithm is proposed and the seam tracing process is realized under a smaller error. Finally, the tracking errors resources and their influence have been simulated and analyzed.

Passive vision based seam tracking system for pulse-MAG welding

Welding robots have been widely used in manufacturing process to substitute for human welders. However, most of them are rigid and cannot adjust to variations in the weld seam positions caused by natural welding environmental factors. To address this problem, this paper presents a passive vision-based robotic welding system, which can realize the seam tracking function for pulse-MAG welding. In this paper, the light spectrum of the welding process is analyzed to determine the optical filters used during the image capture. Then, a robust image processing method is proposed to extract the offset from the image which contains much noise. The transformation formula is calibrated to obtain the relationship between the image coordinate system and the robot coordinate system. The tracking strategy is designed to improve the tracking precision and the stability of the welding process. Finally, experiments are conducted on straight line and curved line seam to verify the feasibility of the developed system.

Annular beam shaping system for advanced 3D laser brazing

Abstract As laser brazing benefits from advantages such as smooth joints and small heat-affected zones, it has become established as a joining technology that is widely used in the automotive industry. With the processing of complex-shaped geometries, recent developed brazing heads suffer, however, from the need for continuous reorientation of the optical system and/or limited accessibility due to lateral wire feeding. This motivates the development of a laser brazing head with coaxial wire feeding and enhanced functionality. An optical system is designed that allows to generate an annular intensity distribution in the working zone. The utilization of complex optical components avoids obscuration of the optical path by the wire feeding. The new design overcomes the disadvantages of the state-of-the-art brazing heads with lateral wire feeding and benefits from the independence of direction while processing complex geometries. To increase the robustness of the brazing process, the beam path also includes a seam tracking system, leading to a more challenging design of the whole optical train. This paper mainly discusses the concept and the optical design of the coaxial brazing head, and also presents the results obtained with a prototype and selected application results.

Welding Seam Turbulent Tracking Technique for Spiral Welded Pipe Ultrasonic Flaw Detection

In the process of spiral submerged-arc welding automatic flaw detection, the weld edge reflection echo is very close to the back edge of the detection gate (generally around 3Ls, is equal to steel transversal wave approximately 4.5mm); therefore once the detector approaches the welding seam, the edge refection echo will enter in the gate, which causes the false alarming. In the past, the mechanical cam tracking, approaching switches tracking and photograph tracking methods were applied, but the mechanical cam tracking and the approaching switches tracking method have low precision, the result is not good. Although photograph tracking method has high measure precision, because of the light scattering of the water flow on the surface of the steel pipe, which will affect the precision. Both photograph tracking and stepping motor-driven methods is commonly used national wide, the effect is not good. Base on the above situation, the electromagnetic welding seam tracking and servo control electromechanical system with functions of electromagnetic tracking and servo control is developed.

A Vision-Based Self-Tuning Fuzzy Controller for Fillet Weld Seam Tracking

In this paper, an intelligent seam-tracking system is developed for fillet weld workpiece. Structured light vision is employed to detect the deviation of the welding torch. Two stripe lines are formed on the surface of the fillet weld workpiece by the structured laser light. Their intercepts are selected as the image feature, which can result in an approximately uncoupled relationship between the image feature and the movement of adjustment mechanism. A two-step feature-extraction method is designed to robustly detect the two lines in image. In order to get a favorable tracking precision in the welding process, a new self-tuning fuzzy controller is designed. Its input and output scaling factors are tuned according to its active working region. Moreover, a supervisory level is introduced into the control system to limit the output pulses in order to guarantee steady and safe tracking. Finally, experiments are well conducted to verify the performance of the proposed system and methods.

Design of Weld Seam Tracking Control System Based on DSP

In the process of weld seam tracking, traditional mathematical model of classical and modern control theory is hard to meet the requirement of high performance controller. This article based on the embedded digital signal processor DSP-TMS320F2812 for the field of industrial automation control.The fuzzy control technology is applied to real-time welding seam-tracking system, according to the F2812 which has the characteristics of real-time multitasking scheduling of resources and then designed the real-time control value adjustment Fuzzy-PI control system. The designed DSP real-time fuzzy control system gives full play to powerful control and signal processing ability of F2812, it can fully adapt for the controlling requirement of super-speed and high-precision.

Deviation Control of Weld Seam Tracking Based on Laser Image Sensing

Because welding system is given the look function by laser image sensing, the automation of welding system is well improved. But the two problems are image processing deviation under welding interference and adjusting deviation of machine set tracking. Targeting at these problems, the weld seam tracking (WST) system is designed. Some mathematics are brought forward, including the log grey transformation, Laplace edge detection, extracting center route of laser strip and detecting the characteristic points of weld seam image. The dynamic trend of WST is controlled by the current seam deviation calculated by seam characteristic points. The subsection control strategy and the decision algorithm of WST stability in abnormal circumstances are used. The WST experimental results show that tracking S shape weld seam is delivered effectively with high precision based on the proposed weld seam tracking, can meet welding technology requirement and provide experimental data for manufacturing WST system.

Visual Technique for Detecting Weld Position Based on Hough Transformation

Detecting the weld position is the precondition of seam tracking during an arc welding process, and is crucial to achieve high-quality welds. Visual sensing is one of the most attractive approaches to detect the weld position, which provides valuable information to control the arc following the expected path. The weld edge is main characteristics of the weld position image, here the visual technique for detecting the weld position based on Hough transformation is proposed. The weld position can be detected and recognized through Hough transformation, while the weld edge image is detected using the Canny operators. And Hough transformation is modified based on the actual weld situation. Therefore, the precision of the weld detection can be improved. From the analysis of experiments, it has been proved that the proposed method can detect the width and the center of the weld, and is suitable for the seam tracking system based on the computer vision.

Real-Time Seam Tracking Technology of Welding Robot with Visual Sensing

A seam tracking system with visual sensing free from calibration was developed for the robot applied in gas tungsten arc welding. A visual sensor with double-layer filter system was researched for the different levels of the welding current. An image processing in C+?+ language was developed to extract the seam trajectory and the offset of the torch to the seam in the welding images of aluminum alloys plates with grooves. The rectifying rule of the robot used in this paper was found based on the experimental data, and the seam tracking controller was also analyzed and constructed. The experimental results on straight line seam and curve seam demonstrated the efficiency of the proposal seam tracking system.

Visual seam tracking system for butt weld of thin plate

An image-based visual seam tracking system is designed for butt weld of thin plate in this paper. The torch deviation from the joint in the horizontal direction is measured from the seam image. Since the weld seam is so narrow, its image is based on natural lighting. Due to the hardness of measuring depth information using monocular vision, structured laser light is used for detecting the torch deviation in the vertical direction. For steady seam tracking, a robust and fast feature extraction algorithm is developed. Moreover, a reliable controller is designed with error filtering and output pulse verification. Finally, experiments are conducted to verify the proposed seam tracking system.

Design of Robot Welding Seam Tracking System with Structured Light Vision

Robot welding is an important developing direction of welding automation and intelligentization, and automatic seam tracking technology is one of principal research domains. Nowadays, seam tracking system with structured light vision becomes a hot research. Structured light vision seam tracking products abroad are generally very expensive and can only be applied on special occasions. In China, the research of structured light vision seam tracking system is still just on the stage of experiments. A robot real-time seam tracking system with line structured light vision is designed. The hardware system is set up, a filtering method for line structure seam image is improved, and compared with common filtering, it has better effect and characteristic of real time. Two methods, fast template matching and fast Hough transform, to recognize the image coordinates of seam center are improved. Two new image recognition methods, structure element matching and corner detecting, are proposed. The comparison of seam image recognition shows that fast template matching and corner detecting are more precise and stable than the other two methods, and corner detecting is the best in real time. A simultaneous calibration for camera parameters and robot hand-eye is also proposed, and calculation shows that the calibration is effective and feasible. The robot seam tracking tests for linear and folded lap-joint are performed, which are based on the above four image recognition methods, and the results indicate that four image recognition methods are all applicable to real-time seam tracking, and the whole system sufficed for the requirements of real-time seam tracking. Automatic seam tracking with line structured light vision is feasible and has good versatility.

Vision Based Modeling and Control for Fillet Weld Seam Tracking

A vision based seam tracking system is designed for fillet weld in this paper. Laser structured light is used to detect the weld joint, and image-based visual control method is adopted. Due to the nonlinear relationship between the image feature change and the movement of adjusting mechanism, back propagation (BP) neural network is used to establish the vision model. Two independent controllers in two orthogonal directions are developed based on the vision model. To verify the effectiveness of the proposed seam tracking system, a series of experiments are well conducted. The results show that high tracking accuracy can be obtained using the proposed system and methods.

Seam Tracking Technology for Hyperbaric Underwater Welding

Automatic weld seam tracking technology to be used in hyperbaric underwater damaged pipeline repair welding is much more important, because of poor bevel preparation and severe working condition. A weld seam tracking system based on digital signal processing(DSP) passive light weld image processing technology has been established. A convenient charge coupled device(CCD) camera system was used in the high pressure environment with the help of an aperture and focus altering mechanism to guarantee overall image visibility in the scope of pressure below 0.7 MPa. The system can be used in the hyperbaric environment to pick up the real welding image of both the welding arc and the welding pool. The newly developed DSP technology was adopted to achieve the goal of system real time characteristics. An effective weld groove edge recognition technique including narrow interesting window opening, middle value wave filtering, Sobel operator weld edge detecting and edge searching in a defined narrow area was proposed to remove the guide error and system accuracy was ensured. The results of tracking simulation and real tracking application with arc striking have proved the validity and the accuracy of the mentioned system and the image processing method.

Robot Based Laser Welding Technology

In order to obtain a good result in the laser welding process, the laser welding technology for manufacturing an automobile body is studied in this research. The monitoring of the welding quality and the seam tracking are studied to improve the productivity. The robot, the seam tracking system and CW Nd:YAG laser are used for the robot laser welding system. The laser system is 4kW Nd:YAG laser_(HL4006D) of Trumpf and the robot system is IRB6400R of ABB. The robot laser welding system is equipped with the seam tracker and plasma sensor. The seam tracking system is composed of SMART-20LS and RAPAL of Servo-Robot and MVS-5 sensor of MVS. The precise positioning of the laser beam on the joint to be assembled is obtained by seam tracker. The welding joints of steel plate are butt and lap joint. The three dimensional welding for non-linear tailored blank is performed after the fundamental experiments of bead-on-plate. Finally, the welding process for non-linear tailored blank and front side member is studied. The monitoring method of welding quality and seam tracking along the butt-joint are studied. The artificial defects in joint are well observed by the plasma intensity signal from the plasma sensor of UV and IR. The robot based laser welding system is developed for the precision seam tracking and the real-time monitoring of welding quality.

Optimization of Welding Process Parameters for Rotating Arc Welding Sensor Based on Genetic Algorithm

The high speed rotating arc welding sensor (RAWS) driven by motor with air axis is widely used in seam tracking system. Using the characters of the RAWS, the purpose of this study based on Genetic Algorithm (GA) is to optimize welding process parameters of the RAWS for obtaining satisfied seam geometry. The output variables are penetration, width and height of the seam geometry. These output variables are determined by input variables, which are the welding current, welding voltage, welding speed, rotating arc radius, rotating arc frequency and rotating arc direction. Experimentations are made according to the optimal welding process parameters, and the result shows that the GA is an effective method to optimize the welding process parameters of the RAWS. The described computational methodology enables obtaining a seam with desired geometry.

Sensor Guided Laser Welding Robot System

In order to obtain a good result in the laser welding process, the laser welding technology for manufacturing an automobile body is studied in this research. The robot, the seam tracking system, and CW Nd:YAG laser are used for the laser welding robot system. Especially, the development of the laser-stripe sensor is highlighted. The laser-stripe sensor can measure the profile of the welding object and obtain the gap and seam line. Moreover, the working distance of the sensor can be varied. The control scheme of the whole system is also presented. The profile and gap measurement and the seam tracking experiments were carried out to validate the operation of the system.

Visual Sensor for Automatic Weld Seam Tracking System to Submerged Arc Inner Welding of Spirally Steel Tubes

Aimed at submerged arc inner welding of spirally steel tubes,a visual sensor for automatic weld seam tracking system is developed.Visual camera is used as sensor,the image of the side obtuse edge is taken at three hundred millimeters front of welded point. Video signal is magnified,trimmed and processed into binary,the pulse waveform of obtuse edge is obtained.Based on vertical center in video signals,the deviation from direction is judged and the deviation value is estimated by computer on-slice,and the deviation signals in the form of pulse signals are transmitted to the drive ofAC servo motor,the motor will control the movement of torch sliding platform, so as to ensure the welding wire to be directed at the weld in real time.Experiment results show that the method is feasible to identify obtuse edge with visual camera;a reliable system for real-time seam tracking to submerged arc inner welding of spirally steel tubes is developed.The response cycle of this system is less than 50 ms,and the tracking precision is±0.3mm.

A visual seam tracking system for robotic arc welding

A novel circular laser three-dimensional (3D) scanner is developed instead of a one-dimensional laser spot scanner (1D) and two-dimensional (2D) striped laser light. Using the proposed circular laser scanner, a seam tracking system is constructed, and architecture based on the Visual C++ and RAPID languages which determines the cooperation among image processing modules is carried out. Finally, real seam tracking experiments are investigated and the error analysis is carried out. The results show that: (1) the proposed system can realize seam tracking; (2) the precision of this system is affected by the light scanning system, calibration results, image processing, and the welding seam 3D algorithm—the tracking accuracy is satisfied for robotic arc welding; (3) this system can be used in a welding robot system as a weld seam finder, flatness detector, and weld seam tracker.

Vision-based seam tracking system of the underwater flux-cored arc welding

To track seam automatically during underwater flux-cored arc welding(UFCAW),a vision-based seam tracking system has been studied.This seam tracking system consists of a vision sensing system,an image processing and seam recog- nizing system,a control system and executive unit.The edge of the weld line is precisely detected by a wavelet transform method.The seam position error is calculated by a seam posi- tion recognition algorithm based on the binary image.Based on the theoretic analyze of the structure model of the vision-based seam tracking system,a control rule self-adjust fuzzy controller is designed.The factors of decreasing the precision of the seam tracking system are analysised,and some measures are adopted to improve the tracking precision.The tracking experiments results of the UFCAW confirm that the control rule self-adjust fuzzy controller meet the demand of the tracking precision.In the tracking trials of sidelong,reflex and curve weld line,the system can all meet the demand of the tracking precision.With the improved mini drain water cap,the tracking experiments of the underwater local dry welding are carried.The results indi- cate that this process can not only meet the demand of improve welding quality but also satisfy the tracking results.

Vision based seam tracking system for underwater flux cored arc welding

Manual underwater welding is usually time consuming, expensive and hard to perform because of the rigorous underwater environment. Automatic underwater welding can be performed faster at less cost and with higher quality. An automatic seam tracking system for underwater flux cored arc welding has been developed. It consists of a vision sensing module, a seam recognition module, a fuzzy controller (FC) and an X–Y travel platform. The vision sensing module can capture clear seam images during welding, successfully resolving the problem of welding arc interference during underwater flux cored arc welding. The seam recognition module filters, enhances and thresholds the seam images and then recognises the seam deviation angle with a three layer back propagation neural network. The FC outputs the control parameters according to the seam deviation angle and then controls the X–Y platform to drive the torch to the centre of the seam. In this study, three different welds were considered: a straight line, a kinked straight line and an S curved line. These welds were tracked real timely during underwater flux cored arc welding. The results show that this seam tracking system can meet the requirements of the automatic underwater flux cored arc welding.