• International Journal of Control, Automation, and Systems
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• 제1권1호
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• pp.35-42
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• 2003

This paper proposes a simple, robust, nonlinear controller based on Lyapunov stability for tracking the reference welding path and velocity of a two-wheeled welding mobile robot (WMR). The system has three degrees of freedom including two wheels and one torch slider. Torch slider motion is used for faster tracking because the welding speed is very slow. Control law is obtained from the Lyapunov control function to ensure the asymptotical stability of the system. The controller has three free parameters for adjusting the performance of the controlled system. A simple way of measuring the errors using two potentiometers is introduced. The effectiveness of the proposed controller is shown through simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.191-196
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• 2003

This paper presents a method to design an adaptive controller for the kinematic model of a two-wheeled welding mobile robot (WMR) with unknown parameters. We propose a nonlinear controller based on the Lyapunov function to enhance the tracking properties of the WMR. The WMR can track any smooth curved welding path at a constant velocity of the welding point. The system has three degrees of freedom including two wheels and one torch slider. Torch slider motion is used for fast tracking. To design the tracking performance, the errors from WMR to steel wall is defined, and the controller is designed to drive the errors to zero as fast as possible. The effectiveness of the proposed controller is shown through simulation results.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.314-319
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• 2002

The Automation and Control Group at the University of Brasilia is developing an automatic welding station based on an industrial robot and a controllable welding machine. Several techniques were applied in order to improve the quality of the welding joints. This paper deals with the implementation of a laser-based computer vision system to guide the robotic manipulator during the welding process. Currently the robot is taught to follow a prescribed trajectory which is recorded a repeated over and over relying on the repeatability specification from the robot manufacturer. The objective of the computer vision system is monitoring the actual trajectory followed by the welding torch and to evaluate deviations from the desired trajectory. The position errors then being transfer to a control algorithm in order to actuate the robotic manipulator and cancel the trajectory errors. The computer vision systems consists of a CCD camera attached to the welding torch, a laser emitting diode circuit, a PC computer-based frame grabber card, and a computer vision algorithm. The laser circuit establishes a sharp luminous reference line which images are captured through the video camera. The raw image data is then digitized and stored in the frame grabber card for further processing using specifically written algorithms. These image-processing algorithms give the actual welding path, the relative position between the pieces and the required corrections. Two case studies are considered: the first is the joining of two flat metal pieces; and the second is concerned with joining a cylindrical-shape piece to a flat surface. An implementation of this computer vision system using parallel computer processing is being studied.

• 한국CDE학회논문집
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• 제10권3호
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• pp.210-216
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• 2005

Digital manufacturing could be very effective in shipbuilding in order to estimate the process time, to improve the operation efficiency, and to prevent bottleneck processes in advance. The subassembly process having done research consists of piece arrangement, tack welding, robot welding, manual welding and so on. The robot welding of them was the focus of the simulation. The analysis and modeling were carried out by using UML (Unified Modeling Language) as well as $IDEF\phi$ (Integration DEFinition). The characteristics of the process resources were analyzed using the shipyard data, and the layout of the subassembly line was designed with the resources. Using the constructed resource and process model, the productivity and efficiency of changed robot welding stage were investigated. It was simulated how much the variations in the resource performance have influence on improvement of productivity. One of the important outputs in this simulation was the cycle time during a certain period's work. The cycle time prediction was also undertaken for the different torch and the different piece arrangement. The proposed model was established three-dimensionally in a digital environment so that interferences among objects and space allocations for the resources could be easily investigated.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1094-1106
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• 2004

In this paper, a nonlinear controller based on sliding mode control is applied to a two-wheeled Welding Mobile Robot (WMR) to track a smooth curved welding path at a constant velocity of the welding point. The mobile robot is considered in terms of dynamics model in Cartesian coordinates under the presence of external disturbance, and its parameters are exactly known. It is assumed that the disturbance satisfies the matching condition with a known boundary. To obtain the controller, the tracking errors are defined, and the two sliding surfaces are chosen to guarantee that the errors converge to zero asymptotically. Two cases are to be considered: fixed torch and controllable torch. In addition, a simple way of measuring the errors is introduced using two potentiometers. The simulation and experiment on a two-wheeled welding mobile robot are provided to show the effectiveness of the proposed controller.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.319-324
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• 2001

This paper presents the motion control of a mobile robot with arc sensor for lattice type welding. Its dynamic equation and motion control method for welding speed and seam tracking are described. The motion control is realized in the view of keeping constant welding speed and precise target line even though the robot is driven along a straight line or corner. The mobile robot is modeled based on Lagrange equation under nonholonomic constraints and the model is represented in state space form. The motion control of the mobile robot is separated into three driving motions of straight locomotion, turning locomotion and torch slider controls. For the torch slider control, the proportional integral derivative (PID) control method is used. For the straight locomotion, a concept of decoupling method between input and output is adopted and for the turning locomotion, the turning speed is controlled according to the angular velocity value at each point of the comer with range of $90^{\circ}$ constrained to the welding speed. The experiment has been done to verify the effectiveness of the proposed controllers. These results are shown to fit well by the simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.270-275
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• 1993

In this paper, the arc welding robot controller using a touch sensor and a arc sensor is presented. The controller is composed of robot controller parts for moving torch, and arc welding controller for welding and tracking. In the controller, an compensated data is generated to control robot trajectory and seam tracking by the arc sensor function. The data is obtained by integration of arc current. Experimental results are presented confirming the controller performance.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.797-800
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• 1992

Much experience and knowledge is needed in welding because there are many working parameters and quantitative description is difficult. Therefore, introduction of expert system based on such data base has been required. In this study, welding heat and shape of bead was controlled by fuzzy inference with the welding condition, position error and voltage and current error of robot. For this, torch trajectory of robot was generated by modeling the working data with CAD and then welding was carried out through down loading to robot. And working error was controlled by on-line communication.

• 대한산업공학회지
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• 제11권1호
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• pp.21-32
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• 1985

Presented in this paper is a procedure of developing graphical simulation software for planning robot welding processes. Welding is by far the highest application area for industrial robots, and it has been in great need of such a simulator in designing robot work cells, in justifying the economics of robot welding and in planning robotized welding operations. The model of a robot welding cell consists of four components: They are an welding structure which is a collection of plates to be welded, a positioner to hold the welding structure, a robot with a weld torch, and a set of welding lines (in case of arc welding). Welding structure is modeled by using the reference plane concept and is represented as boundary file which is widely used in solid modeling. Robot itself is modeled as a kinematic linkage system. Also included in the model are such technical constraints as weaving patterns and inclination allowances for each weld joint type. An interactive means is provided to input the welding structure and welding lines on a graphics terminal. Upon completion of input, the program displays the welding structure and welding lines and calculates the center of mass which is used in determining positioner configurations. For a given positioner and robot configuration, the welding line segments that can be covered by the robot are identified, enabling to calculate the robot weld ratio and cycle time. The program is written in FORTRAN for a VAX computer with a Tektronix 4114 graphic terminal.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.678-682
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• 2000

The purpose of this study is to develop a powerful 6-axes general welding robot utilizing a low cost vision system. The developed vision system is composed of a CCD camera, a PC with windows 98 OS, and a PC-Robot communication program using Visual C++. A test was carried out to investigate whether the welding torch can precisely follow up the welding path. It shows that the result of this study can readily be applied to practical welding operations.