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Automatic programming for industrial robot to weld intersecting pipes
Abstract
An articulated robot cooperated with a positioner is widely used in the field of intersecting pipes welding. In order to resolve the bottlenecks in productivity caused by the burdensome manual teaching process, this article presents an algorithm to generate motion codes for industrial robot to weld intersecting pipes. A unique welding scheme that simplifies welding technology complexity is introduced and adopted. Based on the geometrical model of intersecting pipes with the most complex intersecting mode, the welding trajectory planning is developed which contains posture planning of the welding torch and weaving welding control strategy. Then the welding trajectory is decomposed into the motion of the robot torch and the positioner, and the spatial relationship between the torch and the robot base is described with homogeneous transformation matrix. Finally, an algorithm flow chart with welding speed control strategy is provided for generating robot motion codes. Simulation and welding experiment verify the feasibility of the algorithm.
... However, Tang et al. [15] proposed a geometric error modeling method for a multiaxis system based on the stream of variation (SOV) theory, in which the axis was treated as a continuous workstation and the intermediate deviations were evaluated station by station. Nonetheless, previous studies mainly focused on conventional machine tools, in which multi-axis welding equipment is less mentioned, especially a kind of 6-axis welding equipment, consisting of a five-axis industry robot and a positioner, which is used in the field of intersecting pipes welding [16]. Compare with conventional machine tools for turning, milling, boring, and grinding, the main geometric error sources of the welding equipment are kinematic errors and control errors. ...
... The one DOF positioner, B-axis, is used to rotate the main pipe, which rotates around Y-axis. The kinematics of the 6-axis welding equipment is shown in Fig. 1, and the reference coordinate system (RCS) is set at the center axis of the main pipe, which is coincident with the User Coordinate System defined in [16]. The welding torch coordinate system (TCS) is coincident with the RCS in the origin. ...
... In this section, the numerical simulations are carried out to verify the effectiveness of the geometric error model and sensitivity analysis of all axes. The welding trajectory planning for intersecting pipes introduced in literature [16] is a typical algorithm to weld intersecting pipes, which can be used to verify the kinematics model and conduct the sensitivity analysis of geometric errors. ...
The influence of geometric errors on the accuracy of machine tools tends to attract more attention to the increasing demand for high-precision machining. In this paper, geometric error modeling and sensitivity analysis are employed to quantify the importance of geometric error for a new efficient and automatic 6-axis welding equipment. The geometric error model of the 6-axis welding equipment with 36 geometric error components is established based on Lie theory. Based on the geometric error model, the new sensitivity analysis method, in which the deviation of the welding torch pose is treated as a distance metric in SE(3), is proposed to evaluate the influences of geometric errors on the accuracy of the welding torch. And the sensitivity coefficient of each geometric error is derived by considering the basic value of geometric errors. Numerical simulations of a typical welding trajectory for intersecting pipes are conducted to analyze the sensitivity of geometric errors by the new method. The simulation results verified the validity of the sensitivity analysis method and the dominant geometric errors affecting the accuracy of the welding equipment were identified. Compared with the previous sensitivity analysis method, the proposed sensitivity analysis method considers the orientation error and position error of the welding torch simultaneously, which is more convenient and effective, and can also be applied in precision design and geometric error compensation of machine tools.
... Without doubt, the position-posture control is more difficult than the position control because the angles of all links are further restricted. [22] and [23] present the position-posture control strategies for the fully actuated manipulators. But when one of the actuators fails, these strategies are not suitable for the underactuated manipulators. ...
... where q i0 (i = 2, 3, 4) are initial angles of three active links, and Fig. 2 shows the mathematical relationship of Eq. (22). Here, the system employs the step PD controllers instead of the general PD controllers. ...
... Mathematical relationship of(22) ...
This paper presents a continuous control strategy based on the differential evolution (DE) algorithm for a planar four-link underactuated manipulator with a passive first joint to realize its position-posture control objective. First, we obtain the coupling equation in integral form between the angle of the passive link and the states (angles and angular velocities) of three active links according to the angular velocity constraint of the system. Then, according to this coupling equation, we construct a Lyapunov function only based on the control targets of three active links, and use the Lyapunov function to design the PD controllers. In addition, these general PD controllers are modified to be the step PD controllers to overcome the sudden change in the initial torques. Next, we use the DE algorithm to optimize the target angles of all links and the design parameters of the step PD controllers, which ensures that the angle of the passive link converges to its target angle when the angles of three active links converge to their target angles. Finally, simulation results demonstrate the effectiveness of the proposed control strategy.
... where η arc efficiency, expressed as a fraction, % n proportion of the energy radiated and convected from the arc column per unit of time and transferred to the workpiece, expressed as a fraction, % q p energy radiated and convected from the arc column per unit of time, Btu/min (cal/s) m proportion of heat radiated away from the workpiece, expressed as a fraction, % q w rate of heat absorbed by the workpiece, Btu/min (cal/s) E voltage, V I welding current, A Experiments reveal that arc efficiency is higher for consumable electrode processes than for non-consumable electrode processes due to heat losses from the arc to the surroundings. With consumable electrodes, heat loss from the electrode can often be ignored as the energy transferred to the electrode [7][8][9][10][11][12][13][14][15][16] Welding speed [7][8][9][10][11][12][13][14][15][16] Gas flow rate [7,8,11,13,15,16] Contact tip to work distance (CTWD) ...
... where η arc efficiency, expressed as a fraction, % n proportion of the energy radiated and convected from the arc column per unit of time and transferred to the workpiece, expressed as a fraction, % q p energy radiated and convected from the arc column per unit of time, Btu/min (cal/s) m proportion of heat radiated away from the workpiece, expressed as a fraction, % q w rate of heat absorbed by the workpiece, Btu/min (cal/s) E voltage, V I welding current, A Experiments reveal that arc efficiency is higher for consumable electrode processes than for non-consumable electrode processes due to heat losses from the arc to the surroundings. With consumable electrodes, heat loss from the electrode can often be ignored as the energy transferred to the electrode [7][8][9][10][11][12][13][14][15][16] Welding speed [7][8][9][10][11][12][13][14][15][16] Gas flow rate [7,8,11,13,15,16] Contact tip to work distance (CTWD) ...
... Electrode extension [11,15] Arc length [7][8][9][10][11][12][13][14][15] Wire feed speed [11,15] Wire diameter [7,8,10,11,[13][14][15][16] Torch angle Torch position [8] Torch travel angle [11] Fig. 6 Arc penetration characteristics of GMAW with a DCEN and b DCEP electrode polarity is eventually absorbed by the workpiece. Arc efficiency in GMAW falls within the range 66-85% [17,23]. ...
The use of welded lightweight steels in structural applications is increasing due to the greater design possibilities offered by such materials and the lower costs compared to conventional steels. Ultra-high-strength steels (UHSS) having tensile strength of up to 1700 MPa with a high strength-to-weight ratio offer a unique combination of qualities for diverse industrial applications. For productivity and quality reasons, gas metal arc welding (GMAW) is usually utilized for welding of UHSS. However, for full penetration fillet welded joints, the need for high heat input to gain acceptable weld penetration is problematic when welding UHSS. This is due to UHSS sensitivity to heat input and possible heat-affected zone (HAZ) softening. In this paper, an attempt is made, on the basis of analysis of experimental reviews, to identify and define relationships between nonlinear weldability factors to enable creation of an artificial intelligence model to predict full penetration in robotic GMAW fillet welded joints of UHSS S960QC. Welding variables and parameters associated with GMAW are first evaluated by reviewing scientific literature. The possibility of employing an artificial neural network (ANN) to predict full penetration fillet weld characteristics is then examined. It is noted that nonlinear variables associated with the GMAW process, such as heat input, contact tip to work distance (CTWD), and torch angle, and their related parameters, which pose weldability challenges, can be modeled by applying artificial intelligence systems. Ensuring full penetration in fillet welded joints of UHSS using artificial intelligence is thus feasible. Further, an optimized control system could potentially be developed by incorporating adaptive robotic GMAW with an artificial intelligence-based system to guarantee sound structural integrity that conforms to EN ISO 5817. The paper increases awareness of welding aspects of UHSS S960QC and presents an approach for overcoming existing limits to GMAW via adaptive robotic welding and artificial intelligence systems.
... One such system employs a specially designed orbital welding robot that can move around a track mounted on the circumference of a pipe adjacent to the joint to be welded [3], such that the entire welding pass can be fully covered in a single run. Another type of welding system is equipped with a turntable to support the workpiece [4,5], and it can rotate and translate all the welding positions into horizontal or vertical positions. In this research, due to the large size of the cross-tubular structures in shipyards, the welding robot is stationary with respect to the joint, as illustrated in Fig. 1. ...
... Tsai et al. [9] developed an offline programming system for robot arc welding in which the workpieces and the welding pass were represented using analytical geometries. Shi et al. [4,5] developed a single pass robot path planning scheme for welding intersecting pipes based on the geometric models of the pipes. ...
... Analytical methods have been reported to model the cross-sectional area of the weld bead [10,14]. These studies did not consider welding segmentation planning to assure that the welding area will be fully reached by the welding torch, as their focus has been on the use of a welding positioner [4,5] or pass planning of a linear groove model [10,14]. Numerous studies focused on weld bead geometry modeling, e.g., integration of artificial neural networks with Taguchi method or regression techniques [15,16], have been reported to address the non-linear effect of welding parameters on the weld bead formation. ...
In robotic welding, the planning and generation of the motion of the welding torch are crucial in welding complex joints. This paper presents an approach for optimal robot path planning of the centroid pass in welding a Y-joint. Relevant data associated with the welding passes is defined and managed to facilitate robot path planning and generation. With properly selected welding torch inclination angles and welding pass segmentation techniques, a solution space containing a number of robot paths is generated to account for functional redundancy and different welding robot configurations. A solution with minimum joint movement is determined using a beam search algorithm as the optimal robot path for each welding pass segment. A case study of robot path planning of the centroid pass of a scaled-down Y-joint is simulated and discussed.
... The polar coordinates of any point (X 1 , Y 1 , Z 1 ) on the branch pipe weld seam are denoted as (r, δ), which can be determined through spatial analytic geometry [18,19]. The equations for the intersecting structure in both the main and branch pipe coordinate systems are as follows: ...
... By solving the intersecting structure of Eq. (19) and Eq. (20), the area ΔS of the groove error surface at the v-th layer can be determined: ...
The welding of intersecting structures requires multi-layer multi-pass welding. Manual welding of intersecting curves is being replaced by robotic welding due to its low efficiency and poor consistency. To enhance weld accuracy in intersecting structures and optimize multi-layer multi-pass planning in robot welding of large components, a realistic groove model is devised to address discrepancies between theoretical and actual groove surfaces. This includes determining the size of the actual error angle, and the modeling of the actual groove in the intersecting structure. A method for groove error correction is then proposed based on this model. Firstly, the total and the error areas of the actual groove are calculated. Subsequently, the errors for each layer of the groove are computed from the total error area of the groove. Error correction for the groove layout is implemented layer by layer, resulting in an algorithm for multi-layer multi-pass groove layout correction. Additionally, a fitting function that closely approximates the groove profile is derived. This procedure finalizes the groove error correction, and through MATLAB simulation, the corrected intersecting structure groove is modeled, with results aligning with the error correction algorithm. Finally, further simulation and experimentation validate the feasibility, accuracy, and effectiveness of the error correction algorithm for multi-layer multi-pass weld planning the actual intersecting structure groove, offering a theoretical foundation for the intricate weld planning required in robotic welding of intersecting components.
... This strategy used the method of constant speed to track the path to make the 5-DOF robot and 2-DOF positioner move simultaneously. Shi et al. [18] studied robots' and positioners' trajectory planning in the process of coordinated welding of intersecting tubes, and Shi et al. proposed an algorithm for generating motion codes for welding intersecting tubes. This algorithm used the welding speed control as the basis of the industrial robot's trajectory planning, and it can prevent the cable winding up. ...
... According to ϕ, the coordinates of each discrete point on the intersecting line can be calculated. The position calculation formulas of the intersecting line in the branch tube coordinate system and the main tube coordinate system are Equations (18) and (19), respectively. ...
In this paper, we propose a synchronous cooperative path planning (SCPP) algorithm for the robot and the positioner to process complex space curve workpieces. The specific algorithm design is illustrated by using the intersecting line welding as an example. The robot and positioner are regarded as an 8-degree-of-freedom (DOF) system to plan the whole synchronous cooperative motion path, and the constraint for the Y-axis of the welding torch coordination system is added for solving the intersecting line orientation information. SCPP is used to process the intersecting line. The changes of welding torch orientation and robot joint rotation angles during welding of the intersecting line by using the improved method and compared to the traditional method. The experimental results show that 8-DOF keeps synchronous cooperative in the whole movement. There is no interference happening during the entire cooperative movement and the welding torch’s orientation remains basically unchanged during the welding intersecting line.
... Welding is one of the most common applications of the dual-robot system. Shi et al. developed an automatic programming for an industrial robot cooperated with a one DOF positioner to weld intersecting pipes, where the posture of the welding torch was considered [5]. Chen et al. established the parametric equation of the intersecting curve and proposed a path planning method to deal with the tube-sphere intersection welds [6]. ...
... For (8) and (9), T c;b c;t;0 is given by the initial pose, T c;t;t c;e;t and T g;t;t g;e;t are constant and determined by the structure of the tool, T c;t;0 g;t;t and T c;t;0 c;t;t are determined by (5) and the method to calibrating T g;b c;b has been widely researched. Finally, the inverse kinematics are employed to calculate the joint displacements. ...
In this paper, automatic programming for dual robots is proposed to realize autonomous robotic grinding of intersecting curves. Compared to grinding with a single robot, dual robots provide more degree-of-freedom to optimize the grinding path. In this paper, a special grinding path, named as intersecting grinding curve, will be realized by the dual robots. Since the intersecting curve is generated by two motions, the dual robots can decouple the motion and finish this task much easier and more effective than a single robot. Also, the motion of each joint becomes smoother, which will benefit for robotic grinding.
... In 2023, China's steel production amounted to 1.363 billion tons, with more than half of it requiring welding processing, indicating a huge demand for welding. The emergence of industrial welding robots has propelled the welding industry towards high-quality development, playing a pivotal role in enhancing production efficiency, reducing costs, ensuring consistent welding quality, and ultimately boosting enterprise profitability [1][2][3] . ...
Automated welding robots face challenges in unstructured field conditions, limiting their use in complex steel structures like pipelines, bridges, and buildings. Expandable convoluted pipe (ECP) poses unique welding challenges due to their confined spaces and irregular shapes. Manually performed butt-welding for ECPs is inefficient. To address this, a flexible mobile welding robot tailored for ECPs was developed. This paper analyses the robot’s structure, working principle, and drive system, minimizing drive chain force-velocity angles to reduce power loss. Transmission modelling, finite element analysis, and life prediction using the Archard model yield promising results. Virtual simulations and prototype welding tests validate the robot’s design, with satisfactory weld formation. Expanding the ECP with a hydraulic pump verifies the robot’s reliability with no weld cracks observed.
... However, teaching and playback applications continue in the industry. Instead, robotic applications that can adapt to different types of profiles and weld in both 2 and 3 dimensions will become more widespread in the coming years inevitably [4,5]. ...
In recent years, seam tracking has become a key focus in autonomous intelligent robotic welding. Accurate detection and recognition of the weld seam are crucial for effective tracking by welding robots. Passive vision technology, favored for its simplicity and cost-effectiveness, is commonly used in the industry. However, software-based improvements are necessary to achieve high-precision weld joint detection, as passive vision systems do not use external light sources. To overcome this problem, the detection of the weld joint on the image is transformed into an image segmentation problem in this study, and a TransUNet structure that combines convolution and transformer structures is proposed to obtain the shape of the welding joint. The proposed method’s detection performance was tested under various lighting conditions. An augmented joint image set was created by adding different contrast values and noises. During training, various loss functions were compared to find the best detection performance. Additionally, the detection performance of the proposed model was compared with various model architectures. The model’s performance was further analyzed by adjusting certain model parameters and modifying the image dataset. Experimental results indicate that the proposed method is robust against different lighting and noise conditions, with TransUNet achieving the highest accuracy rates.
... Tsai et al. [8] developed a robotic arc welding offline programming system in which the workpieces and the welding step were represented by analytical geometries. Shi et al. [9,10] developed a single-step robotic path planning system for the welding of intersecting pipes using geometrical models of the pipes. Yang et al. [11] reported a visionbased approach to obtaining workpiece groove information for double-sided, double-arc, double-sided welding. ...
The field of inspection for welded structures is currently in a state of rapid transformation driven by a convergence of global technological, regulatory, and economic factors. This evolution is propelled by several key drivers, including the introduction of novel materials and welding processes, continuous advancements in inspection technologies, innovative approaches to weld acceptance code philosophy and certification procedures, growing demands for cost-effectiveness and production quality, and the imperative to extend the lifespan of aging structures. Foremost among the challenges faced by producers today is the imperative to meet customer demands, which entails addressing both their explicit and implicit needs. Furthermore, the integration of emerging materials and technologies necessitates the exploration of fresh solutions. These solutions aim to enhance inspection process efficiency while providing precise quantitative insights into defect identification and location. To this end, our project proposes cutting-edge technologies, some of which have yet to gain approval within the sector. Noteworthy among these innovations is the integration of vision systems into welding robots, among other solutions. This paper introduces a groundbreaking algorithm for tool path selection, leveraging profile scanning and the concept of joint symmetry. The application of symmetry principles for trajectory determination represents a pioneering approach within this expansive field.
... The transition to automation has begun with the existence of autonomous systems instead of human-based production due to the existence of harsh conditions in industrial environments, the lack of people in sensitive operations, and the lack of manpower in heavy operations [1,2]. The use of industrial robots in many different areas can be listed as transporting the materials produced from one place to another, welding-soldering works, assembly-disassembly, painting, and cutting [3,4]. Studies such as cutting, welding, and metal shaping, which require precise movements and robots are the main premise in the operations to be carried out, continue to be studied by researchers [5,6]. ...
The welding process, which is an indispensable part of the manufacturing industry, has been in demand for years and continues to attract the attention of researchers. With the transition to Industry 4.0, the welding process got out of the control of the operators and became automated with sensors and artificial intelligence methods, and as a result, it became inevitable for industrial manipulators or robots to enter the production sector. One of the most important details in making the welding process autonomous in manufacturing is the sensors, and among the sensors are the vision sensors. In recent years, it is seen that robotic welding applications are applied very sensitively and successfully when visual sense and artificial intelligence are used together. This study comprehensively reviewed research and development for cutting-edge applications using visual sensors and artificial intelligence for robotic welding applications. The processes that are the subject of intelligent robotic welding applications such as calibration, determination of welding starting point, seam tracking, and welding quality are determined and discussed based on current studies and critical analyzes. The detection, tracking, diagnosis, classification, and prediction performances of various methods of machine learning (ML), which is one of the most used areas in artificial intelligence-based applications, in welding applications are examined comparatively. This review article will help researchers about what should be considered in vision sensor aided robotic welding applications and how to contribute more to studies with artificial intelligence support.
... Another task-specific feature is welding weaving [35,162]: traditionally it is obtained by adding an oscillating device between the robot flange and the welding torch, but such device is not required when weaving is introduced at the motion planning level, simply by adding a sinusoidal displacement to the end-effector path [96,129] (Fig. 4.7). ...
The problem of robotic path planning has been the focus of countless investigations since the early works of the ’70s and, despite the large number of results available in literature, is still a topic that draws a great interest. In virtually all robotic applications it is required to somehow define a feasible and safe path, and such a problem can be cast and solved in many ways, given the several possible combination of robots—industrial robots, Autonomous Guided Vehicles (AGVs), Unmanned Aerial Vehicles (UAVs), underwater vehicles—and scenarios—a production line, a warehouse, an hazardous mountain—and therefore a large number of approaches and solutions have been, and are being, investigated. The aim of this chapter is to provide an overview of such widespread literature, first by briefly recalling some classic and general-purpose methods used in path planning, then by focusing on some application-specific problems, related to AGVs in industry, medical robotics and robotic welding. This choice is motivated by the prominent relevance of the path planning problem in these three applications. Then, a single application of great industrial interest, such as robotic spray painting, is analysed. Its specific features are described, and several techniques for task modelling and path planning are considered. A detailed comparison among these techniques is carried out, so as to highlight pros and cons of each one, and to provide a methodology to choose the most suitable one for the specific robotic spray painting application.
... Weaving welding technology is usually applied to weld steel structures in architectural applications [18], and it is difficult to automate [19] due to the challenges associated with parameter selection and process control [20]. Research on robotic autonomous welding shows that guaranteeing weld quality in the groove edge area is more difficult than in the central groove area [21,22]. ...
The weaving welding process is a key method used to improve the welding quality in multi-layer and multi-pass welding processes using robots. However, the heat-input fluctuation in the weaving welding process restricts its development. In this paper, we developed a novel weaving welding control algorithm to maintain a constant weld heat input through velocity adaptive planning. First, the heat consumption during the weaving welding was modeled to describe the influence of weaving parameters on the weld heat input. Then, based on the obtained relationship between the weld heat input and the weaving parameters, a velocity-adaptive trajectory planning strategy was proposed by leveraging the transformation matrix derived from the relationship between the workpiece and the robot co-ordinate systems. The simulation and experimental results show that the proposed strategy can compensate for the weaving parameters to maintain a constant heat input based on heat consumption and improve the quality of the robotic multi-layer and multi-pass welding process.
... The lack of the reported results for complex 3D cases was also highlighted in [2]. In fact, the majority of experimental results reported in the literature focus on robot welding path planning, and the scanning (or other data collection) step is not sufficiently described [20][21][22]. Alternatively, the robotic welding system is simulated, and the data is virtually generated, making a scanning algorithm unnecessary [23,24]. ...
This paper presents a novel procedure for robotic scanning of weld grooves in large tubular T-joints. The procedure is designed to record the discrete weld groove scans using a commercially available line laser scanner which is attached to the robot end-effector. The advantage of the proposed algorithm is that it does not require any prior knowledge of the joint interface geometry, while only two initial scanning positions have to be specified. The position and orientation of the following scan are calculated using the data from two previous weld groove scans, so once initiated, the scanning process is fully autonomous. The procedure is a two-step algorithm consisting of the prediction and correction substeps, where the position and orientation of the sensor for the following scan are predicted and corrected. Such a procedure does not require frequent weld groove scanning for navigation along the groove. The performance of the proposed procedure is studied experimentally using an industrial-size T-joint specimen. Several cases of scanning motion parameters have been tested, and a discussion on the results is given.
... Foi utilizado o algoritmo SFS (Shape from shading) para reconstruir as formas 3D do segmento de solda e a informação da curvatura é extraída como vetor de recurso das soldas. Por último, o trabalho de [75] apresenta um algoritmo para gerar os códigos de movimento de um robô de solda. Baseado no modelo geométrico, o planejamento da trajetória de solda é desenvolvido com um controle estratégico para o movimento de costura de solda. ...
Resumo: O processo de soldagem é um método de união de materiais metálicos por meio do aquecimento até uma temperatura adequada. Esse processo é crucial na manufatura de diversos componentes, desde a microeletrônica até componentes estruturais de máquinas pesadas. Com o advento da automação industrial, houve o início da utilização de robôs de solda na indústria, visando uma maior produtividade, qualidade e acuracidade do processo. A partir do século XXI, com a chegada da Indústria 4.0, é possível enxergar novas oportunidades de melhoria no processo de solda, tais como a introdução do sistema CPS (Cyber Physical System), a realidade aumentada e a realidade virtual. Tais técnicas permitem não só a automatização da operação de soldagem, mas também um maior controle do processo, cruzando informações do método planejado com a operação real de modo dinâmico e adaptativo. Nesse contexto de diversificado portifólio de tecnologias usadas no processo de soldagem, o presente trabalho se propõe a realizar uma revisão da literatura com o objetivo de mapear as principais evoluções tecnológicas da automação dos processos de soldagem a arco nos últimos anos.
... Xu et al. [18] developed a new welding seam tracking software program, which can obtain better tracking accuracy in most welding applications by analyzing the characteristics of robot GMAW, which can obtain better tracking accuracy in most welding applications. Shi et al. [19] proposed an automatic welding algorithm applicable to different welding equipment, which described the kinematic characteristics of the welding scheme. The noise in the welding process will seriously affect the detection of feature points, resulting in inaccurate and unstable path planning and deviation correction [20]. ...
With the development of manufacturing industry and technology, traditional manual welding technology is gradually unable to meet the need for industrial mass production in the field of fusion welding and additive manufacturing. As a result, an automatic welding method using robots to replace manual welding is needed. This paper studies the additive weld seam tracking technology based on laser vision and designs a welding seam tracking system. The images of linear structure light which reflect welding seam information are collected by vision sensor. The structure light extraction algorithm window is selected under the guidance of the over-exposure characteristics of all kinds of noises. The ERFNet network is applied for the structure light and its corresponding feature point extraction. The accurate center line of structure light is extracted from strong background noise and the feature point of weld seam is obtained through regression. It realizes the online path planning and deviation correction of the weld seam tracking in real-time. The proposed algorithm is demonstrated by the weld feature extraction experiment and welding seam tracking experiment based on groove additive task. It shows that the offset is within one pixel and the distance is within 0.25 mm between the welding feature points extracted by ERFNet and the manually marked welding points. The proposed algorithm has the performance of high robustness, strong adaptability and can meet the practical welding requirements.
... Ren et al. 19 modelled the weld seam and welding torch pose in welding intersected T-shaped pipes. Shi et al. 20,21 proposed an algorithm for industrial robots to weld intersecting pipes. Li et al. 22 used the Solidworks API CAD software for path planning. ...
The V-groove joint of thick wall intersecting pipes must be filled by multi-layer weld. The welding path of intersecting pipes is complicated, and hence multi-layer welds increase the complexity of the problem. This paper proposes a methodology for path planning of multi-layer weld of thick wall intersecting pipes. The methodology is based on measuring the electrode pose located in both side and front views of intersecting pipes. In order to compensate for the path deviation around the pipe circumference, the measured values are used to interpolate the path of each pass between two views.
The methodology has been applied in a case study. Simulation results approve that multi-layer weld
appropriately fills the V-groove joint space around the pipe circumference. In addition, collision avoidance between welding torch and pipes is considered by introducing a safety ring. While the robot wrist moves inside the safety ring, no collision occurs. Simulation results show the robustness of the proposed path planning method, introduced for collision avoidance.
... Therefore, some off-line automatic motion planning (OLAMP) algorithms have been proposed to improve the efficiency and accuracy of the planning. For example, Shi et al. [9,10] presented an off-line algorithm for intersecting pipes welding and this automatic programming method avoids the bottlenecks in productivity caused by burdensome manual teaching. Although these OLAMP algorithms have greatly solved the existing problems to some degree, they are still not suitable for more complex welding, such as the complex weld seam (complex space curve) and the seam which is situated in complex environments (narrow passage or dense obstacles), etc. ...
Automatic motion planning in complex environment is significant in manufacturing. This paper presents an off-line collision-free motion planning algorithm by considering the task redundancy existing in manufacturing. The paper takes a typical welding technique as an example, which mainly aims at solving the complex continuous welding motion planning problems. In the proposed algorithm, the angular redundancy existing in the welding process is fully considered for planning and optimizing the welding torch path by minimizing the torch angular cost. Besides, some strategies have been introduced to improve the efficiency of the proposed algorithm, such as the heuristic region sampling strategy based on Gaussian sampling, which is adopted to guide planning. Midpoint collision checking strategy is employed to improve the efficiency of the collision checking. The proposed algorithm is very effective in solving the complex welding motion planning problems, such as in the welding environment where the weld seam is situated in the narrow passage or the dense obstacles. The experiments are carried out to verify that our proposed algorithm is feasible in the relevant scenarios. All the experimental results show that not only the proposed algorithm could find a feasible collision-free path in the different complex environments if any path exists, but also the torch angle could be optimized with the increase of iteration.
... More repetitive works are required to execute these degrees of freedom. Corresponding structural designs have some special difficulties [15][16][17][18]. Traditional methods rely on experts' experiences and these kinds of experiments may increase the costs of production and the randomness of the products [19]. ...
To reduce weight and improve overall performance of the industrial welding robot, light-weight design using the finite element method and structural topological optimization is presented in this paper. The work analyzed an upper arm of an industrial welding robot in the most unfavorable working condition, both under static and dynamic working situations, using ABAQUS and ADAMS software tools. Then the Tosca unit in ABAQUS was employed to accomplish the structural topological optimization, in order to reduce weight and improve the natural frequencies under the situation of low orders. The analyses results showed that the actual weight had been reduced to 17.9%, and the natural frequencies in low orders had increased. The maximum Mises stress, tensile stress, and elastic displacement of the gyration center had decreased. Lastly, an actual product was produced according to the model obtained from preceding analyses. The experiments of the repeatability tests showed that the overall performance of the optimized upper arm had been improved when compared to the original one. This research can present references and foundations for the kinetic analyses under the static and dynamic working conditions, and structural topological optimization designs for relative industrial welding robots.
... Then this paper gives the parameter equations of intersecting curve based on independent rotation variable and proposes the welding mechanism of the main pipe rotation. On the basis of the above research, paper [12] added the robot swing welding technology and proposed the calculation method of sinusoidal swing curve. However, the curve cannot be stopped on both sides of the weld, and the center swing speed is not adjustable. ...
Sphere-pipe joints welding is widely used in industrial applications. This paper presents a robot welding approach for the sphere-pipe joints with swing and multi-layer planning. Firstly, various coordinate systems are used to describe the geometric relationship between weld seam and robot welding torch. The sphere-pipe intersecting curve welding process is basically uphill and downhill welding. Therefore, this paper establishes a description model of the welding torch attitude, which parameterizes the attitude description and automatically adjusts the torch attitude during the welding process according to the change of weld inclination angle. To overcome the negative effects of gravity, such as deepening of the molten pool and reduction of the weld width, this paper integrates the swing welding technology into trajectory planning and gives a solving algorithm for the welding torch swing curve. The swing welding also can reduce the number of weld pass. Therefore, multi-layer single-pass swing welding is an economical and efficient way for thicker weldments. In this paper, a multi-layer single-pass swing welding planning algorithm is proposed, which can automatically determine the height and swing amplitude of each welding layer. Finally, the industrial robot Puma560 is used to carry out experimental simulation, and the simulation results are used to verify the feasibility and accuracy of this approach.
... Korayem and Ghariblu considered the effect of base position and a mobile manipulator redundancy on the trajectory planning of a robotic manipulator in its workspace (Korayem And Ghariblu 2003, korayem, Ghariblu, andBasu 2004). Zhang 2015) proposed an algorithm for industrial robot to weld intersecting pipes. Li et al. (Li et al. 2009) used Solidworks API CAD software for path planning. ...
The main objective of this paper is to develop a redundancy-resolution algorithm to optimize the joint motion of a redundant robotic welding system. At first, the Joint Limit Avoidance (JLA) and Singularity Avoidance (SGA) optimizations are employed. Due to complicated geometry of the welding path, despite using JLA & SGA optimizations, some constraints like joint angles violate their allowable limits. Hence, functional redundancy (FNR) is employed as the best solution because it has no effect on the welding electrode direction. In this paper, the functional redundancy is used as an augmented task, which changes the desired path without effecting the electrode direction. To select the best functional redundancy angle, two indexes, i.e. the minimum joint angles movement and the singularity indexes, are introduced. Simulation results show that the planned path using FNR not only satisfies all constraints, but it also is smooth.
... They did not study path planning with benefiting from redundancy. Shi et al. [18,19] proposed an algorithm for industrial robot to weld intersecting pipes. They considered welding requirement in path planning, but didn't consider the path planning limitation in joint space. ...
In this paper, a path planning algorithm for robotic systems with excess degrees of freedom (DOF) for welding of intersecting pipes is presented. At first step, the procedure of solving the inverse kinematics considering system kinematic redundancy is developed. The robotic system consist of a 6 DOF robotic manipulator installed on a railed base with linear motion. Simultaneously, the main pipe is able to rotate about its longitudinal axis. The system redundancy is employed to improve the welding quality. Three different simulation studies are performed to show the effect of the robotic system kinematic redundancy to plan a better path for welding of the intersecting pipes. In the first case, it is assumed that robotic manipulator base and main pipe are fixed, and path is planned only with manipulator joints motion. In the second case, only robot base is free to move and main pipe is fixed and finally, in the third case main pipe is free to rotate together with base of the manipulator. It is seen that kinematic constraints according to the system's redundancy helps us to plan most efficient path for welding of complex pipe joints.
... To a certain extent, the reliability and consistency of welding production will not depend on the welder's skills and experiences anymore [3]. However, in some complex structures such as the tubular intersecting structure, called as the T, K, and Y node structure, which is widely used in shipbuilding, high-pressure vessel, and offshore industries [4][5][6][7], it is still a difficult problem to realize robotic welding. ...
In order to meet the demand of robotic multi-pass welding of single V-groove with an uneven and irregular change of intersecting pipes, a novel method in which the weld was divided into several segments according to the change rate of cross-sectional area was put forward in this paper. It was effective to avoid repair welding and secondary processing for such complex joints. By controlling the welding parameters in each segment, the amount of filler metal changed with the cross-sectional area of weld groove; thus, the number of weld passes kept unchanged in each layer and the appearance of the weld remained flat. For each segment, the appropriate welding parameters were identified according to the target value of the size of welding seam through the second-order regression prediction model which was related to the width and height of weld seam. Finally, the feasibility of the welding trajectory was verified by virtual simulation. Welding experiment was carried out and the actual welding seam was basically consistent with the planning results. It was proved that this planning method for sectional welding of the welding seam according to the variation of cross-sectional area is feasible and can be applied to practical welding engineering.
... It also described the position and orientation of weld seam and welding torch quantitatively in the form of coordinate system, and determined the parameters that can describe the welding torch's attitude accurately. Paper [12,13] introduced a kind of automatic welding scheme for intersecting pipes. The geometric model of the intersecting pipes is established, and the parameter expressions of the intersecting curve based on the independent rotation variable are given. ...
When the deviation between the actual pipelines and the ideal models cannot be neglected, the intersecting curve weld seam based on non-ideal models should be specially studied. This paper will introduce a novel method to quantify the deviation of the intersecting curve weld seam based on the non-ideal models. Weld location is a technical means for obtaining the actual position of weld seam, which may be used to obtain the location information of some key points on the intersecting curve. Combined with the information of weld location and the inherent characteristics of the intersecting curves, this paper analyzes the experimental results of actual intersecting curve welding, and all these works laid the foundation for the proposed algorithm. First of all, on the basis of previous studies, this paper introduces a kind of model for intersecting pipelines, which can cover most of the ways of coherence. Secondly, based on this model, the factors which may lead to the deviation of the theoretical intersecting curve from the actual intersecting curve are analyzed. Generally, there may be some connections or coupling between the sources of deviation. Against the above problem, the paper gives a solution to model each source of deviation and discuss the relationship among them, and then makes use of the information of weld location to quantify the main sources of deviation one by one, especially the quantification of the main pipes ovality. Finally, the correctness and flexibility of the algorithm are verified by the MATLAB simulation.
... Each discrete point on the fitted intersecting curve can be obtained by substituting the discrete variable u in the (16), and then, the position and orientation of the welding torch are determined by the (24) and (30). Since we have known the information of the welding torch, the mechanical parameters of the welding device are subjected to kinematic inverse transformation, and the position of each axis is obtained and the welding NC code is generated [20]. Figure 16 shows the actual welding effect of the fitted intersecting curve weld seam in accordance with the parameters given in Table 1. ...
In the industrial applications of intersecting curve welding, in order to improve the accuracy and quality of welding, the automation program of weld seam positioning, data processing, and the actual welding is widely used. In this paper, a lot of research has been carried out, and a method based on non-uniform rational B-spline (NURBS) curve fitting is presented, while the trajectory of the welding torch is planned. The method can use the position data of the discrete weld seam points obtained by manual teaching or weld seam location. By the improved least squares method and the White rule, the outliers are eliminated and the weld seam points for intersecting curve fitting are obtained. These points are fitted based on NURBS, and then the parameter expressions of the fitted intersecting curve are given. For the purpose of obtaining the orientation of the welding torch, the coordinate system which can describe the feature of the fitted intersecting curve is established. The coordinate system is combined with the theoretical intersecting curve model and the fitted intersecting curve model and gives a novel approach to compute the orientation of the welding torch according to the position of the fitted intersecting curve. In the process of planning the welding trajectory, a fitted intersecting curve discrete algorithm based on the equal arc length principle is proposed to reduce the fluctuation of the feed rate according to the restriction of chord error. Finally, this method gives the position and orientation of the welding torch in the form of a homogeneous matrix and verifies the correctness and flexibility of the algorithm by MATLAB simulation and intersecting curve welding experiment.
... A seam tracking sensor in an automation welding system is necessary [19][20][21]. Although a vision sensor was the most outstanding technique with non-contact, quick processing, and anti-interference characteristic, the image processing is very complex. ...
To solve the problems that the current seam tracking process cannot find the weld line and the control method based on the kinematic model of welding mobile robot leads to low accuracy, a method for searching the welding seam is designed firstly. By this method, the initiation point of the weld line can be found and the attitude of the robot parallel to the weld line can be adjusted automatically. Secondly, for improving the tracking precision and anti-interference performance, a new controller based on the kinematic and dynamic model of the mobile welding robot is designed. To deal with the partial uncertainty and the disturbances of welding process, this controller combines the sliding mode variable structure control and low-pass filter, so that it is able to complete the controlling of cross-slider and wheels coordinately. The stability and convergence of the designed controller are proved through the use of Lyapunov theory. The effectiveness of the proposed method is verified by simulation and experiments. In the seam tracking process, the welding torch is able to track the welding seam well and the robot moves steadily without any obvious chattering.
... It plays a very important role in stabilizing and improving the quality of products, the production efficiency, the working conditions and the rapid upgrading of products. Robot technology [3][4][5] is the combination of computer control theory, multi discipline mechanism, information and sensor technology, artificial intelligence, bionics. It is extremely active and can be widely used in various fields. ...
The industrial robot plays a very important role in stabilizing and improving the quality of products, production efficiency, working conditions and the rapid upgrading of products. It is often composed of a mechanical body, control device, driving system and detection and sensing device, and can be used in three-dimensional space to complete integration of automatic production and processing equipment. Spraying robot is one of the most important advanced coating production and processing equipment. It has the advantages of considerable flexibility and wide working scope, high spraying quality and material utilization efficiency. Due to the increasing competition for the market share, it should minimize the cost continually to accomplish the producing process. For the spraying process, how to optimize the trajectory of the spray gun and the spray parameters are the key factors to reduce the material consumption and improve the efficiency. In this paper, the spray gun trajectory and spraying effect are studied, and the experimental results show that the spray trajectory and spray effect are available. The results can also be used in other fields to get better performance.
Saddle-shaped weld seams of the header-and-nozzle joints challenge both manual and robotic welding with their complex spatial characteristics, poor welding consistency, and the need for multi-layer and multi-pass welding. This paper proposes a multi-layer and multi-pass welding path planning method based on laser scanning and 3D reconstruction for complex saddle–shaped weld seams. A user coordinate system is established based on the workpiece benchmark determined by the continuous scanning of the scanner and the coordinate transformation. The 2D segmented weld seams feature is converted from the 3D feature obtained by a given scanning pose in the user coordinate system by a dimension reduction transformation. The path planning is completed by the equal-area method on the filled area determined by the contour of the welding layer obtained from the simplified curve with an accuracy within ± 1 mm. The robot’s 3D trajectory is formed by the 2D path points represented by the centroid of welding pass on each cross-section after inverse space transformation. Experimental results confirm the path planning’s efficacy in robotic welding automation, ensuring good welding formation.
In boiler industries, the automated welding of header and tube-seat joints is a critical topic. Traditional offline programming method suffers from deviations between models and real workpieces. Vision aided welding provides a feasible way to deal with the problem, but the point cloud acquisition and reconstruction are yet to be developed. In this paper, a fast point cloud reconstruction method for saddle-shape welding seams in boiler header and tube-seat joints has been proposed. The point clouds of header and tube-seat joints in boilers are acquired by a partition scanning strategy, and then reconstructed using a two-step registration method. The partial point clouds are first coarsely spliced using position relationship, and then fine registered to improve accuracy. Besides, a simple but effective benchmark, the registration mark, has been proposed. The performance of splicing in each stage has been evaluated with the registration mark. The registration mark after fine registration in each iteration is lower than 1 mm. Finally, the partial clouds are spliced to form a complete cloud.
Aiming at the problems of the complex motion simulation model in the offline programming process of the robot, taking 6-DOF industrial robot as an example, the construction scheme of the complex motion model is introduced in detail, the model includes three parts: a 3D model, a mathematical model, and a motion algorithm and use unified coordinates calibration. The storage problem of the project is solved through the task data interface, and the data exchange between the project file and the project data module is realized, and verified the processing process through simulation.
The welding of spatial intersecting curves is widely used in the pressure vessels, in which the welding quality cannot be achieved by traditional methods. To this end, this paper proposes a novel methodology of dual-robot welding for the intersecting pipes by means of motion planning and off-line programming. This method takes advantage of the redundancy of the dual-robot system to obtain alternative paths for the collaborative welding task. Based on the mathematical model of the welding seam, the intersecting curve trajectory of the intersecting pipes is generated through the relevant mathematical theory and the MATLAB programming. The intersecting curve trajectory is decomposed into the welding trajectory and collaborative trajectory, and then imported into the RobotStudio simulation platform. The collaborative welding operation of dual-robot is finally achieved, which verify the effectiveness of the proposed methodology.
A real-time robotic weld tracking system based on laser vision sensor is designed for intersecting seam. Firstly, the traditional image processing method is used to determine the weld feature point in the first frame when there has no arc noise. Then, an extending and adopting Kalman Filter with Spatio-Temporal Context algorithm was proposed to extract the weld feature point when the laser stripe was blocked by heavy arc and splash noise during welding. Next, in order to control torch to weld automatically, the torch frame was established through novel three points principle and an expanding circle and arc length method. In addition, a segmentation weld method and an intermediate proportional interpolation method for step-size control of mobile torch were proposed to guarantee the accurate of weld. Finally, Experiments and analyses results show that the tracking system is good in real-time, accuracy, stability and flexible, which can meet the weld requirements.
With the rapid development of industrial automation, the traditional manual operation is no longer suitable for the development of modern enterprises, because the industrial robot control system dynamic response is fast, high position accuracy, strong overload capacity, so it is very suitable for the production of mechanical parts and processing line automation transformation. In this paper, an air conditioning compressor company to the pump body production line for the theme of automation, the application of industrial robots instead of artificial automation production. Aiming at the transformation of the L2 series pump body assembly line in the assembly plant of the company, the industrial robot was used to transform the production line, and the program debugging was carried out on the site. The robot was able to run stably and work as required. At last, the actual working beat of the robot is calculated to be 13.7 seconds, which is 2.3 seconds less than 16 seconds in manual operation. Experimental results show that the actual working tempo of the robot can meet the requirements, and can improve the assembly efficiency and save manpower.
In welding, the actual weld seam is the target path of welding robot. When the deviation between the actual pipelines and the ideal models cannot be ignored, special research should be carried out. This paper introduces a novel method to quantify and compensate the path deviation of actual intersecting curve, which is used to determine the welding path of robot. Weld location is a technical means, which can be used to find the position of some key points on intersecting curve. Combining the information of weld location with the inherent characteristics of intersecting curve, this paper has analyzed the results of actual welding experiments, all these works laid the foundation for the proposed algorithm. First of all, on the basis of previous studies, this paper introduces a kind of geometric model for ideal intersecting pipelines, this model can cover most of the ways of intersection. Secondly, based on this model, the factors leading to the deviation between the theoretical intersecting curve and the actual are analyzed. Generally speaking, there may be some connections or coupling between the deviation sources. In view of the above problem, this paper constructs model for each source of deviation and discusses the relationship between them, then quantifies the main sources of deviation by using the weld location information, especially the quantification of the main pipe's ovality. Subsequently, the deviation after the quantification is compensated to the parametric equations of the theoretical intersecting curve. As the goal of this paper, the actual intersecting curve's equations based on non-ideal model are obtained, which is regarded as the path of welding robot. The correctness and flexibility of the path planning approach are verified by the welding robot at last.
In this paper, a customized interface developed in the framework of the ROBOT FASE II project is described. This project aimed at improving the productivity of two FANUC ARCMate 100iC MIG welding robots with R-30iA controllers mounted in an 8 meters-high mobile gantry crane at Navantia company in Puerto Real, Spain. The solution designed for welding application by the University of Cadiz consists of four parts (1) a library of piece templates including relevant information for each piece to be welded, including obviously the typical piece geometry shape and dimensions, but also all parameters needed for welding(sequence, intensity of the arc, waving description,…) and optimized to get a perfect result by a professional welder team (2) a coordinate measuring arm used to capture 3D information from the real world, (3) a software to generate automatically the optimized FANUC welding program using both the template and the 3D information captured by the arm, adapting the template to real-world coordinates and orientation, (4) and finally an FTP interface to transmit the optimized welding program to each robot for immediate welding operation. The use of this solution for welding operation has reduced robot programming time from hours to minutes for a typical structure allowing an important increase of productivity at Navantia company.
The welding seam of intersected pipes is a typical and complicated space welding seam. The models of weld position and welding torch pose were founded for arc welding robot, and their position and pose were described precisely and quantificationally by coordinates. Then, the welding torch orientations were described by work angle, traveling angle and rotation angle, and the calculation methods were presented. A new simple method of calculation is put forward to establish the coordinate system of welding seam according to the characteristic analysis that any tangent through the point on intersection line coincides with the intersection line of two cylinder sections at this point. The model is general to the intersected pipes and it has significance for modeling on weld position and welding torch pose, simulating and off line programming for robot welding.
Early studies on robot machining were reported in the 1990s. Even though there are continuous worldwide researches on robot machining ever since, the potential of robot applications in machining has yet to be realized. In this paper, the authors will first look into recent development of robot machining. Such development can be roughly categorized into researches on robot machining system development, robot machining path planning, vibration/chatter analysis including path tracking and compensation, dynamic, or stiffness modeling. These researches will obviously improve the accuracy and efficiency of robot machining and provide useful references for developing robot machining systems for tasks once thought to only be capable by CNC machines. In order to advance the technology of robot machining to the next level so that more practical and competitive systems could be developed, the authors suggest that future researches on robot machining should also focus on robot machining efficiency analysis, stiffness map-based path planning, robotic arm link optimization, planning, and scheduling for a line of machining robots.
Effects of gravitational orientation on gas tungsten arc (GTA) welding of nickel were studied to determine the impact of free-surface deformation on weld-pool shape. This was accomplished through GTA welding and a numerical study of the welding process. Welding was conducted by varying scan velocity and gravitational orientation, e.g., welding upward opposing gravity (parallel-up weld), welding downward with gravity (parallel-down weld), and welding perpendicular to gravity (perpendicular weld). Slower scan velocity produced more significant free surface deformation. Gravitational orientation caused 21% deeper penetration in the parallel-up weld compared with the parallel-down weld (resulting from 50% or more maximum surface deformation). Weld penetration of the perpendicular weld was between that of parallel-up and parallel-down cases. A model of the welding process, in which an experimentally generated free surface was implemented as a boundary condition, supported the results by showing similar trends.
Tough pitch or OFHC copper was welded in argon-x mixed gases. Porosity increases with the nitrogen addition to argon very steeply in tough pitch copper welds and somewhat gradually OFHC copper welds. From the viewpoint of weld soundness and penetration depth, the nitrogen or argon-nitrogen gas metal- arc welding of copper using electrode wires alloyed with titanium is proposed. Use of the new electrode wires results in sound welds and greater penetration.
This study establishes trajectory model and welding torch pose model, and presents a four-axis (θ, y, r and η) interpolation algorithm for saddle curve (SC) automatic welding. Algorithm is simulated to verify its feasibility by simulating SC with MATLAB and OpenGL tool software.
Main pipe-rotating welding scheme for intersecting pipes can enhance welding quality by translating all of the welding position to horizontal vertical position. For purpose of the automation of this welding scheme, this article presents an automatic welding algorithm with a general description of the kinematic character, which is applicable to different welding equipment. Geometrical models containing pipes’ parameters and welding torch’s posture and dynamic model adequately expressing the welding process are established successively. Two different piecewise linear fitting methods used for real-time interpolation and off-line programming are introduced and analyzed subsequently. A three-dimensional simulation and a welding experiment with a 6-axis machine tool verify the feasibility of the algorithm.
All-position robots are widely applied in the welding of complicated parts.Welding of intersecting pipes is one of the most typical tasks.The welding seam is a complicated saddle-like space curve,which puts a great challenge to the pose planning of end-effector.The special robots designed specifically for this kind of tasks are rare in China and lack sufficient theoretical research.In this paper,a systematic research on the pose planning for the end-effectors of robot in the welding of intersecting pipes is conducted. First,the intersecting curve of pipes is mathematically analyzed.The mathematical model of the most general intersecting curve of pipes is derived,and several special forms of this model in degraded situations are also discussed.A new pose planning approach of bisecting angle in main normal plane(BAMNP) for the welding-gun is proposed by using differential geometry and the comparison with the traditional bisecting angle in axial rotation plane(BAARP) method is also analytically conducted.The optimal pose of the welding-gun is to make the orientation posed at the center of the small space formed by the two cylinders and the intersecting curve to help the welding-pool run smoothly.The BAMNP method can make sure the pose vertical to the curve and center between the two cylinders at the same time,therefore its performance in welding-technique is superior to the BAARP method.By using the traditional BAARP method,the robot structure can become simpler and easier to be controlled,because one degree of freedom(DOF) of the robot can be reduced.For the special case of perpendicular intersecting,an index is constructed to evaluate the quality of welding technique in the process of welding.The effect of different combination of pipe size on this index is also discussed.On the basis of practical consideration,selection principle for BAARP and BAMNP is described.The simulations of those two methods for a serial joint-type robot are made in MATLAB,and the simulation results are consistent to the analysis.The mathematical model and the proposed new pose-planning method will lay a solid foundation for future researches on the control and design of all-position welding robots.
The welding with weaving has been used widely to obtain better weld quality by avoiding lack of side wall fusion and improve the weld efficiency by obtaining the wide weld bead. But the effect of weave frequency and weave amplitude on the temperature field is not clear. In the present paper, a coordinate transformation method is put forward to simulate the weave welding process. The temperature distribution during the welding with weaving under different weave parameters are compared and discussed. Comparison between experimental and simulation results reveals a good agreement. The peak temperature and the average temperature in weld seam center decreased due to the increasing of the weave amplitude and weave frequency. But the weave frequency has less effect on the average temperature.
Among most developed sections of CAM (Computer Aided Manufacturing) utilization in area of technical praxis there is the generation of different kinds of NC programs for various manufacturing devices. Yet these CAM systems do not affect entire production in a satisfactory way. Therefore there is a need for definition of the systems of Computer Aided Manufacturing Engineering - CAME systems. CAME presents a special part of the CIM area regarding the computer aided systems that concern all the tasks related to the performance of industrial manufacturing.
A robot belt grinding system provides promising prospects for relieving hand grinders from their noisy work environment, as well as for improving machining accuracy and product consistency. However, for a manufacturing system with a flexible grinder, controlling the robot to perform precise material removal from free-form surfaces is a challenge. In the belt grinding process, material removal is related to a variety of factors, such as workpiece shape, contact force, and robot velocity. Some factors of the grinding process, such as belt wear, are time-variant. To achieve the desired removal in the grinding process, an intelligent control method for the industrial robot is proposed in this paper. First, an adaptive grinding process model that can track discontinuous changes in working conditions is constructed to precisely predict material removal in accordance with in situ measurement data. With incorporated prior knowledge, the method considerably improves model accuracy, which worsens when new samples from an in situ measurement are insufficient or are unevenly distributed under new working conditions. After this, an online trajectory generation method for the robot control parameters is proposed. By calculating the optimal control parameters in real time, the control transition process is shortened and its negative effect on grinding quality is reduced. Finally, the preliminary grinding experiments validate the workability and effectiveness of the proposed control method.
In actual manufacturing process, many weldments have large dimensions and complex shapes, and they are usually assembled through a multi-pass welding process. The joints of the tube–sphere intersection (J-groove joints) are complex. This paper presents a complete solution in determining the welding paths based on a developed J-groove joint robot. Generating complex welding paths in terms of cubic B-spline curves is made easy using path control modules such as interpolation module and local modification module. The point inversion module using particle swarm optimization is introduced to address the partition of path, which is required of the welding process. Experimental results show that higher efficiency as well as better weld quality can be achieved, indicating a promising and practical use of the robot for welding applications, which is rarely available at present.
This paper describes the development of a robotic CAM system for an articulated industrial robot RV1A from the view point of robotic servo controller. It is defined here that the CAM system includes an important function which allows an industrial robot to move along cutter location data (CL data) consisting of position and orientation components. In addition, the developed CAM system has a high applicability to other industrial robots whose servo systems are technically opened to end-users. The developed robotic CAM system works as a straightforward interface between a general CAD/CAM and an industrial robot. At the present stage, the relationship between CAD/CAM and industrial robots is not well established compared to NC machine tools that are widely spread in manufacturing industries. The CAM systems for NC machine tools are already established, however, the CAM system for industrial robots has not been sufficiently considered and developed yet. A teaching pendant is generally used to obtain position and orientation data of the arm tip before an industrial robot works. Here, in order to enhance the relationship between a conventional CAD/CAM system and an industrial robot, a simple and straightforward CAM system without using any robot language is developed and implemented. The basic design of the robotic CAM system and the experimental results are presented in this paper.
Purpose
The purpose of this paper is to develop a portable all‐position welding robot for the welding of intersected pipes.
Design/methodology/approach
A complete procedure is adopted to conduct the design. The task and motion of the robot are analyzed and a mathematical description of the pose and position of the welding tool is given. Based on that, three representative types of robot are chosen in the type synthesis of mechanism. Two new indices proposed to evaluate required properties of the robot, along with the traditional dexterity index, are chosen to be the criteria in the dimension synthesis of mechanism. Through the optimization by genetic algorithm, the best robot in type and dimension is determined after comparison on their performances. Finally, the prototype is developed.
Findings
The paper finds a new robot for welding intersected pipes.
Originality/value
A new robot is introduced for the welding of intersected pipes. A complete design procedure is adopted to conduct the design. Two new indices are constructed for evaluating the required properties of this robot.
This paper presents the architecture of a system for robotic welding of complex tasks. The system integrates off-line programming, control of redundant robots, collision-free motion planning and sensor-based control. An implementation for pipe structure welding made at Odense Steel Shipyard Ltd., Denmark, demonstrates the system can be used for automatic welding of complex products in one-of-a-kind production.
Large amount of stainless steel tubes would be applied in the desalination system. If the tubes are welded manually, there would be a lot of the repeated work accompanied with the extremely low efficiency and the welding quality could not guaranteed either. So the best choice to finish the work is using a robotic welding system. In this paper, a robotic system to be employed in welding the pipes for desalination of sea water is introduced. The robotic system contains four revolute axes and could be mounted on a branch pipe, so it can both maneuver between the pipes and adjust to a wide range of pipes’ diameter. Moreover, it is very convenient to take with for it is compact and lightweight. The mathematical method for calculating of the geometry of welding path of the intersecting cylinders is also explained. The welding robot, a digital welding power and the gas shielded system are included in the welding system. The robot movement is controlled by a micro-controller and it could communicate with the host IPC (industrial personal computer) through RS232. Other devices are directly controlled by the host IPC. Finally, a simulation is taken and the result shows that the welding system is able to meet the requirements.
Although an automated flexible production cell is an intriguing prospect for small to median enterprises (SMEs) in current global market conditions, the complexity of programming remains one of the major hurdles preventing automation using industrial robots for SMEs. This paper provides a comprehensive review of the recent research progresses on the programming methods for industrial robots, including online programming, offline programming (OLP), and programming using Augmented Reality (AR). With the development of more powerful 3D CAD/PLM software, computer vision, sensor technology, etc, new programming methods suitable for SMEs are expected to grow in years to come.
The paper presents a linear solution that allows a simultaneous
computation of the transformations from robot world to robot base and
from robot tool to robot flange coordinate frames. The flange frame is
defined on the mounting surface of the end-effector. It is assumed that
the robot geometry, i.e., the transformation from the robot base frame
to the robot flange frame, is known with sufficient accuracy, and that
robot end-effector poses are measured. The solution has applications to
accurately locating a robot with respect to a reference frame, and a
robot sensor with respect to a robot end-effector. The identification
problem is cast as solving a system of homogeneous transformation
equations of the form AiX=YBi,i=1, 2, ..., m.
Quaternion algebra is applied to derive explicit linear solutions for X
and Y provided that three robot pose measurements are available.
Necessary and sufficient conditions for the uniqueness of the solution
are stated. Computationally, the resulting solution algorithm is
noniterative, fast and robust
Gas metal arc welding handbook
- W H Minnick
- WH Minnick