Mathematical model for robotic arc-welding off-line programming system

Processing configuration off-line optimization for functionally redundant robotic drilling tasks

A robotic simulation and off-line programming package has been developed for use on Silicon Graphics workstations that has the capability of using several types commercially available virtual reality (VR) hardware devices. The software includes a library of 4, 5, and 6 degree-of-freedom (DOF) industrial robots with closed form inverse kinematics and translators that convert graphical simulation commands into the device control language that can be transferred to the robot control hardware. Forward kinematics, inverse kinematics, and joint space path planning methods used in the software development are discussed. The performance of three types of commercially available 6-DOF input devices are compared for use in interactive off-line programming. Stereo vision and external 6-DOF positioning devices were added to enhance programming efficiency and offer more realistic access to the virtual workcell environment.

In this paper, a model is presented which, based on a description of the shape of a welding seam (the gab size and bevel angles), can be used to select variables controlling the welding of a root-bead. The model can be used in an off-line programming system as well as in a geometry-sensor based control system.The model is a stationary model and it is established on an empirical basis. Tests indicate that the model can be used to select control variables for seams with root gabs between 2 and 5 mm. The allowed deviation from the nominal value of the gab is app. 0.5 mm.The model has been implemented in an off-line programming system generating robot programs for welding thick walled large diameter nozzles perpendicular onto pipes. Tests with this off-line programming system indicate that if the workpiece geometry is defined sufficient well, a satisfactory weld quality is obtained when executing the control variables computed by the model.

Modern high power diode laser systems supply an output power of up to 3 kW, which is sufficient for their use in material processing. By building up a low cost 3D-laser assembly consisting of a diode laser and a common industry robot, combined with an off-line programming system and a flexible sensor interface, it was possible to make use of the high power diode laser’s characteristic attributes. This system is already qualified for different manufacturing methods like laser beam welding, hardening and remelting. Detailed information about the required system technique and working results for each manufacturing process are given as follows.Modern high power diode laser systems supply an output power of up to 3 kW, which is sufficient for their use in material processing. By building up a low cost 3D-laser assembly consisting of a diode laser and a common industry robot, combined with an off-line programming system and a flexible sensor interface, it was possible to make use of the high power diode laser’s characteristic attributes. This system is already qualified for different manufacturing methods like laser beam welding, hardening and remelting. Detailed information about the required system technique and working results for each manufacturing process are given as follows.

Task level off-line programming system for robotic arc welding — an overview

In order to realize automatic flexible drilling with high efficiency and good quality, a drilling system was established, which integrates the technology of laser measurement, off-line programming, computer control and robotics. In this system, the key coordinate frames are established by the laser tracker, the drilling programs are generated by the off-line programming and simulation system, the communication between the automatic drilling control system and the robot control system is based on the socket technique. By running drilling program, the moving platform, robot and the end effector can work automatically and harmoniously. In addition, the deviation compensation methods of hole position and its normal vector are proposed. The experimental results show that the efficiency of drilling can achieve 6 holes per minute, the position accuracy can be effectively controlled within 0.3mm, and the normal accuracy is better than 0.5°.

Off-line-programming intends to increase the flexibility of robot systems and thereby the degree of automation in production. At present the available commercial off-line programming systems might be grouped in very efficient, but expensive workstation based systems and in PC-based ones which often possess only restricted efficiency with regard to their numerical and graphical power. This paper presents the PC-based and thereby low-cost robot off-line programming system of the University of Siegen (Ropsus) as a very efficient alternative. This efficiency is available by using optimized algorithms to solve the inverse kinematic problem as well as the collision detection problem and by using CAD-hardware which is optimized for 3D-animation, i.e., graphical standards for presentation and manipulation of cell objects are not used. The underlying operating system is Unix System V.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper develops an off-line programming system to generate tool paths for robotic polishing. The system extracts CAD data from STL format files of free-form surfaces and builds topology relations of triangular facets. We adopt direction-parallel path pattern, since it needs less degrees of freedom and is much easier to avoid the physical intervention and the dynamic singularity. We incorporate topology relations of triangular facets into the direction-parallel path generation algorithm with equal axis intervals, so this can remove the redundant data and facilitate the efficiency of path generation. Again, we propose the constant contour interval path generation algorithm, which can generate paths with equal contour intervals. The generated paths with equal contour intervals are desired for robotic polishing. We implement the off-line programming system based on Qt and OpenGL. The system can generate accurate and uniform paths of free-form surfaces, such as the turbine blade surface and the propeller blade surface.

The work described in this paper address the problems of productivity of Grohe's Portugal grinding/ polishing department, related to the frequent stops of robotic cells for on-line programming and program adjustments. The solution to the stated problem was achieved through the adoption of off-line programming as an alternative to the conventional on-line method. Efforts were developed to overcome some limitations and restrictions found in terms of the software applications used, in order to adapt and improve their use to the needs of this type of contact applications. The solution developed is currently used for off-line programming the grinding robots at Grohe Portugal, with a significant reduction in the cells stop time to program the robots and also in the cycle time. The application of the off-line programming method and of the new programming techniques allowed to obtain a reduction of the cell stop time (up to 85% reduction), to optimize the production cycle time (up to 10% reduction) and, simultaneously, good results in terms of product finishing. The main limitations faced are the lack of realism of the wheel flexibility and the lack of sensitivity of the contact force with it.

This paper presents a dedicated off-line programming system for robotic cutting in pipe processing based on Visual Studio 2010 and OpenGL. The off-line programming system can calculate the space trajectory and generate the programs for a 6-DOF industrial robot automatically. It has a convenient and friendly interactive interface, and the process of cutting can be seen intuitively. Robot programs generated by using the developed system have been tested on a robotic cutting system, and the experimental results are provided, which demonstrate the practicability of the off-line programming system.

A major problem when using off-line programming system is today's robot-based workcells still is that for more complex tasks like e.g. arc welding, general coating, grinding or laser-based applications, the support by these programming tools is poor. Particularly, together with intricate workpieces designed from free-form surfaces (e.g. NURBS) the programming of the desired robot motion still requires a lot of manual, teach-in like work by the programmer. This paper presents two approaches which now support the programmer in a comprehensive manner to solve this problem efficiently.

Grinding/lapping process is the final process for mold manufacturing, and is the criteria to check the quality of molds. However, this process depends on manual operation due to its work characteristics, and becomes the bottleneck process in the whole mold manufacturing process. To reduce mold manufacturing lead time, and to improve its productivity, multi joint robot system is implemented to automate grinding/lapping process. Total 8-axis redundancy grinding/ lapping robot system is developed as automation system which consists of 6-axis multi joint robot, 1-axis straight line carriage, 1-axis index table for walk rotation. Especially, we developed simulator which enables virtual drive simulation using OLP (Off Ling Programming) by importing 3D mold design data. In this study, we analyzed position error by measuring drive position command value and actual site robot driven automatic teaching using laser tracker, to optimize OLP simulation's operation program for grinding/lapping robot system. Based on this error analysis data, it will be able to compensate position for 3D walk model in virtual environment.

More and more robot control systems require intelligent extensions such as vision or virtual reality (VR) system in order to be capable of easy and flexible interaction with the environment or humans. This paper describes the stereo vision, virtual reality and off-line programming part of the intelligent control system of the Puma 560 robot and the dextrous hand developed at the Technical University of Budapest. With the use of the detailed graphic models of the VR system, efficient off-line robot programming and simulation of the contact forces between the hand and the grasped object is available. A simple robot programming language, which was written specifically for this robot-hand system, is introduced.

HELGA, a graphical simulation program of the IBM 7535 robot, uses animation to simulate the motion of the robot. A feature of HELGA is its off-line programming capability which has been designed specifically for use as an educational tool. Included in this paper are a description of the HELGA simulation program, some of its commands, and an example of the system's off-line programming capability.

High power Nd-YAG lasers enable wide variety of material processing. Good control of power and affected area enables good results with minimum distortion. Beam delivery with flexible optical fibers enables robotized 3D processing which requires complicated paths and programming. Short delivery cycles and small batch sizes require short response times. Off-line programming of laser robot cells is usually the only solution to meet these needs.Without physical toolpoint, teaching the hardening paths on complex shapes is very difficult and slow. Aligning the tool visually is demanding. What cause teaching to be virtually impossible are paths inside the workpiece. When 3D model of workpiece is available, programming can easily be done with off-line programming software.One robot program can consist of over 1000 tagpoints, which are automatically generated on model features like surfaces and edges. All laser controls can be added to robot program already at off-line stage. With simulation, created programs can be tested against collisions and robot performance limitations.In this paper a case of large area hardening of cylindrical workpieces is presented. Process is fully automated and gained hardening area is over 1 m2 per hour, regardless of the workpiece shape.High power Nd-YAG lasers enable wide variety of material processing. Good control of power and affected area enables good results with minimum distortion. Beam delivery with flexible optical fibers enables robotized 3D processing which requires complicated paths and programming. Short delivery cycles and small batch sizes require short response times. Off-line programming of laser robot cells is usually the only solution to meet these needs.Without physical toolpoint, teaching the hardening paths on complex shapes is very difficult and slow. Aligning the tool visually is demanding. What cause teaching to be virtually impossible are paths inside the workpiece. When 3D model of workpiece is available, programming can easily be done with off-line programming software.One robot program can consist of over 1000 tagpoints, which are automatically generated on model features like surfaces and edges. All laser controls can be added to robot program already at off-line stage. With simulation, created programs can ...