Seam Tracking and Visual Control for Robotic Arc Welding Based on Structured Light Stereovision

A real-time arc welding robot visual control system based on a local network with a multi-level hierarchy is developed in this paper. It consists of an intelligence and human-machine interface level, a motion planning level, a motion control level and a servo control level. The last three levels form a local real-time open robot controller, which realizes motion planning and motion control of a robot. A camera calibration method based on the relative movement of the end-effector connected to a robot is proposed and a method for tracking weld seam based on the structured light stereovision is provided. Combining the parameters of the cameras and laser plane, three groups of position values in Cartesian space are obtained for each feature point in a stripe projected on the weld seam. The accurate three-dimensional position of the edge points in the weld seam can be calculated from the obtained parameters with an information fusion algorithm. By calculating the weld seam parameter from position and image data, the movement parameters of the robot used for tracking can be determined. A swing welding experiment of type V groove weld is successfully conducted, the results of which show that the system has high resolution seam tracking in real-time, and works stably and efficiently.

Study on general inverse kinematics of rotating/tilting positioner for robotic arc welding off-line programming

Off line programming provides an essential link between CAD and CAM, whose development will result in greater use of robotic arc welding. An arc welding system with a robot and a rotating/tilting positioner is one of the most typical workcells. The inverse kinematics of robot and positioner is the foundation of the off line programming system. The previous researchers only focused on a special solution of the positioner inverse kinematics, which is the solution at down hand welding position. In this paper, we introduce a method for representing welding position. Then a general algorithm of rotating/tilting positioner inverse kinematics is presented, and an approach to find the unique solution of the inverse kinematics is discussed. The simulation experiment results show that the general algorithm can improve the ability of robotic arc welding off line programming system to program all types of welding positions.

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.

An approach to measure the pose of RHJD4-1 arc welding robot for calibration

A measurement setup used for robot calibration was designed to meet the requirement of off line programming technique. The robot end effector pose (position and orientation) can be calculated indirectly by using this setup. The setup has been applied to RHJD4 1 arc welding robot. The experimental results show the method of pose measuring using the measurement setup is simple and reliable to finish pose measuring for robot calibration. In addition, the setup can measure the position repeatability of robot.

Hybrid Visual Servoing Control for Robotic Arc Welding Based on Structured Light Vision

A novel hybrid visual servoing control method based on structured light vision is pro-posed for robotic arc welding with a general six degrees of freedom robot. It consists of a positioncontrol inner-loop in Cartesian space and two outer-loops. One is position-based visual control inCartesian space for moving in the direction of weld seam, i.e., weld seam tracking, another is image-based visual control in image space for adjustment to eliminate the errors in the process of tracking.A new Jacobian matrix from image space of the feature point on structured light stripe to Cartesianspace is provided for dierential movement of the end-e?ector. The control system model is simplifiedand its stability is discussed. An experiment of arc welding protected by gas CO2 for verifying iswell conducted.

VISION-BASED RECOGNITION AND GUIDING OF INITIAL WELDING POSITION FOR ARC-WELDING ROBOT

A method is put forward to realize the recognition and guiding of initial welding position. The weld seams are marked with black lines, which simplify the computational complexity of image processing greatly. A two-time template matching method has been advanced to search for the target point, which is simple and has higher calculation speed. According to the depth computing principle with the special point matching using binocular stereovision, the initial welding position can be confirmed by calculating the middle point of the perpendicular line of two radials in the space. Taking the welding of propellant fuel container for example, good results are obtained with the algorithms. Finally, similar method for terminating welding position is also advanced.

Real-time monitoring of weld penetration quality in robotic arc welding process

It is of great significance to develop an intelligent monitoring system for weld penetration defects such as incomplete penetration and burn-through in real-time during robotic arc welding process. In this paper, robotic gas metal arc welding experiments are carried out on the mild steel test pieces with Vee-type groove. Through-the-arc sensing method is used to capture the transient values of the welding voltage and current. The raw data of the captured welding current and voltage are processed statistically, and the feature vector SIO is extracted to correlate the welding conditions to the weld penetration information. It lays foundation for intelligent monitoring of weld quality in robotic arc welding.

Geometric model of roboticarc welding for automatic programming

Geometric information is important for automatic programming of arc welding robot. Complete geometric models of robotic arc welding are established in this paper. In the geometric model of weld seam, an equation with seam length as its parameter is introduced to represent any weld seam. The method to determine discrete programming points on a weld seam is presented. In the geometric model of weld workpiece, three class primitives and CSG tree are used to describe weld workpiece. Detailed data structure is presented. In pose transformation of torch, world frame, torch frame and active frame are defined, and transformation between frames is presented. Based on these geometric models, an automatic programming software package for robotic arc welding, RAWCAD, is developed. Experiments show that the geometric models are practical and reliable.

CCWELD:A CIM system for robotic arc welding

This paper describes a CIM system for robotic arc welding.The system is specially designed for producing workpieces in small and medium batch sizes.Based on the development of AUTOCAD and a structure-light visual sensor.low cost CIM is implemented. Feature modeling of weld workpiece is discussed.which provides complete geometric information and process information for off-line programming.The system provides powerful tools for programming of torch orientation to meet the requirents of achieving good welding quality,avoiding collision and not violating kinematics constraints.

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.

Kinematic Study on Motoman HP6 Arc Welding Robot Based on Unigraphics

The links of Motoman HP6 arc welding robot are considered as an open kinematic chain which consists of a series of rotational joints through concatenation. One end of the open chain is fixed to the base or the earth, and the other end which is free fastens the end executor to complete various duties. Each link of this arc welding robot has four kinds of Denavit-Hartenberg parameters: common normal length between two adjacent links, angle of two adjacent joints, distance between the crossing of common normal length and two joints axes, and angle of two adjacent links. The displacement relation between each link of the Motoman HP6 arc welding robot is introduced, and the kinematic positive-going solution and the kinematic passive-going solution are calculated.

A high-precision control system for robotic welding positioner

Aiming at the robotic welding positioner with characteristic of parameter change, load change, nonlinearity, and an intelligent control system was researched and developed. This control system used a two-mode controller that based on Fuzzy and PID control method. The results of simulation show that the dynamic and steady performances of the intelligent controller are better than that of single PID or Fuzzy controller. This paper has made a detail theoretical analysis of the constitution design and real-time controlled software and brought up the design and fulfillment method of multi-task real-time control software of high precisely and numerically controlled welding positioner, which has a good result in practice.

Inverse kinematics and welding experiments of the intersecting pipe welding robot

A robot used for multi-pass welding of the piping branch junctions and nozzle attachments to main pressure vessels is 4-DOF serial mechanism, two mobile joints and two rotary joints are adopted in design. The kinematic model was established with DH parameters, the inverse kinematics was solved. According to the forward and inverse kinematics equations, the robot kinematics was simulated in Matlab, the simulations indicate that the solution for inverse kinematics can satisfy the welding requirements well. As there are size errors, processing errors and welding deformation, the path of welding is forecasted according to the previous welding situation, and then, the path is taught at desired via-points, which plays an important role in submerged-arc welding. The submerged-arc welding experiments indicate that the robot and the welding methods are preferable to ensure welding quality.

FUZZY REGRESSION MODEL TO PREDICT THE BEAD GEOMETRY IN THE ROBOTIC WELDING PROCESS

Recently, there has been a rapid development in computer technology, which has in turn led to develop the fully robotic welding system using artificial intelligence （AI） technology. However, the robotic welding system has not been achieved due to difficulties of the mathematical model and sensor technologies. The possibilities of the fuzzy regression method to predict the bead geometry, such as bead width, bead height, bead penetration and bead area in the robotic GMA （gas metal arc） welding process is presented. The approach, a well-known method to deal with the problems with a high degree of fuzziness, is used to build the relationship between four process variables and the four quality characteristics, respectively. Using these models, the proper prediction of the process variables for obtaining the optimal bead geometry can be determined.

On-Line Detection of Porosity in Gas Tungsten Arc Welding of Aluminum Alloy Based on Spectrum Features

The real-time detection of porosity in welding process is an important problem to be solved in intelligent welding manufacturing.A new on-line detection method for porosity of aluminum alloy in robotic arc welding based on arc spectrum is proposed in this paper.First,k-shape and the improved k-means were used for the initial feature selection of the preprocessed arc spectrum to reduce the data dimension.Second,the secondary feature selection was carried out based on the importance of features to further reduce feature redundancy.Then,the optimal sample label library was established by combining the final characteristic parameters and the X-ray pictures of welds.Finally,an on-line detection method of porosity in gas tungsten arc welding of aluminum alloy based on light gradient boosting machine(LightGBM)was proposed.Compared with extreme gradient boosting(XGBoost)and categorical boosting(CatBoost),this method can achieve better detection performance.The new method proposed in this paper can be used to detect other welding defects,which is helpful to the development of intelligent welding technology.

基于Simufact welding仿真在弧焊机器人教学中的研究

本文主要介绍了Simufact仿真软件的作用和特点,并将Simufact仿真软件应用在技工院校弧焊机器人教学中,运用该软件加强学生对焊接工艺参数焊接电流、送丝速度、焊接速度等参数的理解,通过仿真效果能更直观掌握焊接参数对焊缝成形及应力变形的影响,能更有效快捷的掌握如何根据焊接母材、焊缝尺寸、焊接条件等设置合理的焊接工艺参数。

Digital Twin Implementation of Autonomous Planning Arc Welding Robot System

Industrial robots are currently applied for ship sub-assembly welding to replace welding workers because of the intelligent production and cost savings.In order to improve the efficiency of the robot system,a digital twin system of welding path planning for the arc welding robot in ship sub-assembly welding is proposed in this manuscript to achieve autonomous planning and generation of the welding path.First,a five-dimensional digital twin model of the dual arc welding robot system is constructed.Then,the system kinematics analysis and calibration are studied for communication realization between the virtual and the actual system.Besides,a topology consisting of three bounding volume hierarchies(BVH)trees is proposed to construct digital twin virtual entities in this system.Based on this topology,algorithms for welding seam extraction and collision detection are presented.Finally,the genetic algorithm and the RRT-Connect algorithm combined with region partitioning(RRT-Connect-RP)are applied for the welding sequence global planning and local jump path planning,respectively.The digital twin system and its path planning application are tested in the actual application scenario.The results show that the system can not only simulate the actual welding operation of the arc welding robot but also realize path planning and real-time control of the robot.

金属弧焊机器人加工轨迹智能规划研究

针对金属弧焊机器人加工轨迹运动规划精度低的问题,提出一种基于改进梯形速度规划算法的弧焊加工轨迹智能规划方法。该方法首先根据D-H法构建机器人的运动学模型,根据拉格朗日法构建机器人的动力学模型;然后应用加速度规划改进后的梯形速度规划算法进行运动规划;最后基于稳健控制的运动修正方法对初步运动规划结果进行修正。仿真实验结果表明:相比于梯形速度规划算法,改进的梯形速度规划算法具有更高的运动规划精度;基于稳健控制的运动修正方法的加入,使运动规划精度、抗干扰性都得到提升,且提高了机器人关节的使用寿命;该方法具有较好的弧焊加工轨迹智能规划性能,基本满足研究需求。

基于Robotstudio的弧焊机器人离线编程

弧焊机器人作为一种自动化焊接设备,其自动化程度在很大程度上取决于程序的编制。目前的工业机器人离线编程平台,可进行机器人作业系统的建模、简单作业程序的编制和作业过程仿真演示。对于由不规则曲线段构成的复杂焊接路径编程,可以用ABB机器人公司开发的Robotstudio软件进行机器人的焊接离线编程。试验证明,该软件可用于各种高质量弧焊作业的编程。