Seam-tracking based on dynamic trajectory planning for a mobile welding robot

A new seam-tracking method based on dynamic trajectory planning for a mobile welding robot is proposed in order to improve the response lag of the mobile robot and the high frequency oscillation in seam-tracking. By using a front-placed laser-based vision sensor to dynamically extract the location of the weld seam in front of torch, the trend and direction of the weld line is roughly obtained. The robot system autonomously and dynamically performs trajectory planning based on the isometric approximation model. Arc sensor technology is applied to detect the offset during welding process in real time. The dynamic compensation of the weld path is done in combination with the control of the mobile robot and the executive body installed on it. Simulated and experimental results demonstrate that the method effectively increases the stability of welding speed and smoothness of the weld track, and hence the weld formation in curves and corners is improved.     

Mathematical modeling and simulation application for a wheeled mobile robot applied on pipe welding

A geometric model was built to represent the position relation of a wheeled mobile robot relative to a pipe. The relationship between the deviation of falling off for the robot and the curvature of the pipe was formulated quantitatively. Based on the relationship, a mathematical model was derived and a fuzzy control algorithm for the robot was developed. Simulations were carried out to confirm the dynamic index and the validity of the mathematical model of the fuzzy control algorithm for seam tracking of pipe welding. Experiments for pipe welding with the mobile robot were also carried out to verify the algorithm, and the results showed that the seam has a good quality with a preferable appearance of weld.     

Study on intelligent welding mobile robot with the function of auto-searching weld line

The development of welding robots suitable for specially unstructured working enviroments has been become an important development direction of industrial robot application because large-scale welding structures have been used more and more widely in modern industry. In this paper, an intelligent mobile robot for welding of ship deck with the function of autosearching weld line was presented. A wheeled motion mechanism and a cross adjustment slider are used for the welding robot body. A sensing system based on laser-PSD （position sensitive detector） displacement sensor was developed to obtain two dimensional deviation signals during seam tracking. A full-digital control system based on DSP and CPLD has also been realized to implement complex and high-performance control algorithms. Furthermore, the system has still the function of auto-searching weld line according to the characteristics information of weld groove and adjusting posture itself to the desired status preparing for welding. The experiment of auto-searching welding line shows that the robot has high tracing accuracy, and can satisfy the requirement of practical welding project.     

Inverse kinematics analysis of tubular joint welding robot

A rail type mobile robot introduced in this paper is used to carry out automatic welding on the T,Y and K-joints in offshore platform jackets.This robotic system is composed of a mobile platform and a ...     

Dynamic and control system analysis of two-wheeled robot for welding application

Aiming at the welding condition of space complex seam is uncertain and the intelligerwe of welding robot is unideal, a two-wheeled mobile robot is developed. It not only has the capacity of autonomous decision and avoiding obstacles, bat also can flexibly move and strongly adapt variable environment. The composition of the welding robot is described and the dynamic model is established. The feasible control strategy and control algorithm is pat forward. The simulation experiments of real world are conducted, the results are satisfying.     

A method of initial welding robot based onposition guiding for arc welding visual servo control

In order to solve the visual guiding task of initial welding position for arc welding robot, this paper presents a practice-prone image-based visual servo control strategy without calibration, and we perform validating experiments on a nine-DOF arc welding robot system. Experimental results illustrate presented method has the function to fulfill the task of welding robot initial positioning with certain anti-jamming ability. This method provides a basis for guiding welding gun to initial welding pose with real typical seam‘ s image properties to replace flag block properties, and is a significant exploit to realize visual guiding of initial welding position and seam tracing in robot welding system.     

The characteristics of welding currents in a rotating arc lead tandem GMAW process and the weld-seam tracking

Tandem gas metal arc welding (T-GMAW) process shows a high deposition rate that up to three times of the single electrode GMAW,so the welding speed could be significantly increased in this process.However,the majority of this process applications are based on the pre-programmed robotic welding,which does not allow them to track the seam real-time during welding.Rotating arc sensor,sensing the seam position by detecting the changing of welding currents,has been widely adopted in the automatic robot welding process.It is proposed in this paper to integrate the rotating arc sensor with a trailing torch to develop a new approach of rotating arc lead tandem gas metal arc welding (RLT-GMAW) process.The characteristics of the welding currents in the proposed new welding process were firstly studied,and then a self-turning fuzzy control seam tracking strategy was developed for the mobile robot automatic welding.The experimental results showed that the proposed RLT-GMAW process had an excellent seam tracking performance and high welding deposition rate.Even if there were some electromagnetic interactions between the two arcs,the deviation of the welding seam could also be reflected by the fluctuation of the welding currents on the leading arc once the correct welding parameters were selected.Based on the detected deviation,the welding tracking experiments showed that the proposed self-turning fuzzy controller had a good performance for the RLT-GMA W process seam tracking.     

Study on DC welding parameters of Al-alloy shaping based on arc-welding robot

The Al-alloy arc-welding shaping system based on arc-welding robot is established, and the Al-alloy shaping manufacture is realized with the DC （direct current） gas metal arc welding （GMAW）. The research indicates that the metal transfer type of DC GMA W, heat input and the initial temperature of the workpiece greatly affect the Al-alloy shaping based on arc welding robot. On the penetration, the weld width and the reinforcement, the influence of welding parameters is analyzed by generalized regression neural network （GRNN） fitting.     

Study on path planning and compensation of off-line programming for thick walled curve welding

Thick walled curve welding are usually joined by multi-layer and multi-pass welding,which quality and efficiency could be improved by off-line programming of robot welding. However, the precision of off-line programming welding path was decreased due to the deviation between the off line planned welding path and the actual welding path. A path planning algorithm and a path compensation algorithm of multi-layer and multi-pass curve welding seam for off-line programming of robot welding are developed in this paper. Experimental results show that the robot off-line programming improves the welding efficiency and precision for thick walled curve welding seam.     

Underwater robot local dry welding system

To satisfy the demand for good quality underwater welding and maintenance of nuclear power stations, a set of local dry automatic welding systems has been developed. These systems were based on an underwater robot that consisted of a special high-power underwater welding power supply, diving wire feeder, mini drain cap, welding robot, and special underwater welding torch. With a digital signal controller microprocessor as its core and combined with a dual inverter topology, the welding power supply was characterized by full-digital construction and multi-waveform flexible output. A compact diving wire feeding device was designed, based on the armature voltage negative feedback and high-frequency chopping pulse width modulation.This device yielded a high-efficiency seal of the driving motor with the help of dynamic and static sealing technology. To overcome the difficulty of local protection and deslagging in the welding area, a mini drain cap (with a duplexgas structure) based on the principle of the convergent nozzle was designed. The practical tests and the underwater welding experiments revealed that the underwater robotic local dry welding system is quite feasible. That is, the system could strike the arc stably and reliably in the shallow water environment, and formed beautiful welding seams.     

Study on full automatic arc welding machine for spherical tank

A full antomatic welding machine for spherical tanks‘ all position multi-layer welds has been developed. This machine is mainly composed of a two-dimension seam tracking system based on microcomputer‘ s memory and a welding tractor as well as rail. The main features of the machine are : while welding the first layer of a seam, its microcomputer system can analyze and store the tracing information from a two-dimension sensor, and control the welding head device to realize two-dimension real time tracing; while welding the second layer up to the top layer of the seam, it can realize two-dimension tracing based on the memorial data, automatically determine the layer number and continually sway the welding head. The welding test shows that the machine has good tracing and welding behavior, and is suitable for spherical tank‘‘ s all position multi-layer welds.     

Spline-based automatic path generation of welding robot

This paper presents a flexible method for the representation of welded seam based on spline interpolation. In this method, the tool path of welding robot can be generated automatically from a 3D CAD model. This technique has been implemented and demonstrated in the FANUC Arc Welding Robot Workstation. According to the method, a software system is developed using VBA of SolidWorks 2006. It offers an interface between SolidWorks and ROBOGUIDE, the off-line programming software of FANUC robot. It combines the strong modeling function of the former and the simulating function of the latter. It also has the capability of with on-line robot. The result data have shown its high accuracy and strong reliability in experiments. This method will improve the intelligence and the flexibility of the welding robot workstation.     

Study on fuzzy control IGBT inverter arc welding power source for robot

Arc welding robot is playing more and more important roles in modern welding manufacturing, but now available welding power sources seldom satisfy with robot system requirements. In this paper, study on fuzzy control IGBT inverter arc welding power source for robot is developed to bring robotic advantages into full play. Firstly, fast response 500A IGBT inverter arc welding rectifier is developed. Secondly, fuzzy control system, which features multi-functions, fast response and wide using range, is developed and reliable measures for preventing interference are designed. Finally, technological experiments for carbon steel are made. The welding experimental results show that the goal of design is attained.     

Welding deviation detection method based on weld pool image contour features

Automatic on-line detection of welding deviation based on machine vision is one of the key technologies of arc welding robot tracking welding,in which obtaining high quality weld pool image and accurate welding deviation detection algorithm are two important steps of tracking welding.Through the research and analysis of the weld pool image of gas metal arc welding(GMAW),it was found that the weld pool contains abundant welding information.First,the average gray value of the weld pool image can reflect the interference degree of arc to weld pool image and the heat input of welding process.Secondly,the tip of the weld pool image contour can reflect the center of the groove gap.Finally,the horizontal distance between the center coordinate of the wire contour and the tip coordinate of the weld pool image contour can reflect the welding deviation.On the basis of analyzing the characteristics of weld pool image,this paper proposes a new method of weld seam deviation detection,which includes the collection of weld pool image,image preprocessing,contour extraction and deviation calculation.The results of the tests and analyses showed that the maximum error of the on-line welding deviation obtained was about 2 pixels(0.17 mm) when the welding speed was ≤60 cm/min,and the algorithm was stable enough to meet the requirements of real-time deviation detection for I-groove butt welding.The method can be applied to the on-line automatic welding deviation detection of arc welding robot.     

A research of arc welding inverter with high stable precision

This paper mainly introduces an output control method with high stable precision of a large power IGBT arc welding inverter.Experiments indicate that this kind of control mode can effectively improve the static and dynamic characteristics and stability of power supply system.And it can decrease the spatters in the welding process apparently.This power supply is especially suitable to automatic robot welding assembly line.It will be the developing direction of robot welding supply in the future.     

Investigation on the communication network of long wire transmitting in remote welding

According to the characteristics of remote welding, including multiple parameters, real-time, and reliability of long wire transmitting, a distributing computer control scheme is adopted. A serial communication network between the master and the slavery computers is constructed. A synchro-control network among slavery computers is designed. Uniform message format and communication protocols are made. Considering intensive high-frequency noises at the welding zone, a quadruple check mode, including data sum check, parameter type check, welding parameters check and Exclusive OR （ XOR ） check, is adopted to assure the reliability of communication among multiple computers. Based on disturbing circuit, common circuit and sensitive circuit, the measures are brought forward to ensure the stabilization of communication network of remote arc welding by analyzing the wiring principle of anti-high-frequency interference of system bus, signal wires and shielding twisted-pair（STP） wires. The results provide the theoretical and practical references for the manufacture of remote welding robot and the quality of remote welding.     

Study on motion simulation of arc welding robot based on UG

The motion simulation of arc welding robot is the basis of the system of robot off-line programming, and it has been one of the important research directions. The UGNX 4. 0 is adopted to establish 3D simulating model of MOTOMAN-HP6 arc welding robot. The kinematic model under link-pole coordinate system is established by the second development function offered by UG/OPEN API and the method of programming using VC ＋＋ 6. 0. The methods of founding model and operational procedures are introduced, which provides a good basis for off-line programming technique under Unigraphies condition.     

Investigation on the communication network of long wire transmitting in remote welding

0IntroductionThe welding is needed during a ocean engineeringconstructed and a nuclear electricity station repaired.Be-cause the survival condition of human is very severe in thelocations,the welding must be fulfilled by robot.Since thecomplete-independence robotwelding is difficultto be real-ized in terms of the current technology levels of robot,arti-ficial intelligence and sensor,the conception of remotewelding is broughtforward.In safe surroundings,the oper-ator remotely watches and contro…     

Subpixel accuracy for extracting groove center based on corner detection

Subpixel accuracy for V-groove center in robot welding is researched and a software measure to increase the accuracy of seam tracking by laser is presented. LOG （ Laplacian of Gaussian ） operator is adopted to detect image edge. Vgroove center is extracted by corner detection of extremum curvature. Subpixel position is obtained by Lagarange polynomial interpolation algorithm. Experiment results show that the method is brief and applied, and is sufficient for the real time of robot welding by laser sensors.     

Control algorithm based on trajectory and orientation of oblique intersection line welding-cutting robot

Working principle for a four-axis oblique intersection line welding robot is analyzed.A mathematical model for welding torch orientation angle is established,and an interpolation algorithm based on tim...