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The automatic off-line generation of welding robot trajectories with emphasis on kinematic feasibility and collision detection

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Title: The automatic off-line generation of welding robot trajectories with emphasis on kinematic feasibility and collision detection
Author: Buchal, Ralph O.
Degree: Master of Applied Science - MASc
Program: Mechanical Engineering
Copyright Date: 1984
Issue Date: 2010-05-17
Publisher University of British Columbia
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]
Abstract: This thesis defines and discusses the problems involved in automatic off-line programming of a robot welding workstation with a minimum of human intervention, and proposes some solutions. The work is motivated by the desire for faster and more powerful programming capabilities combined with reduced robot down-time for programming, resulting in increased flexibility, efficiency and productivity. The system proposed in the thesis uses data generated by commercial Computer Aided Design (CAD) systems. An "Expert Welder" software module selects the correct welder settings based on workpiece and workstation characteristics. Provision is made for the eventual incorporation of a real-time seam tracking system. The kinematics of a welding robot and workstation are considered in detail. The welding torch position and orientation relative to the robot are found from a series of known relative homogeneous coordinate transformations. Path feasibility is determined by the kinematic constraints of joint limits and the work envelope, as well as by physical interference between the arm and other objects in the workstation. The inverse kinematics solution is found and the solutions are checked against the joint limits and work envelope for each desired robot position. The sixth degree of freedom is redundant for welding, and this redundancy is used to search for feasible kinematic solutions. A simplified interference detection algorithm is proposed. The workstation is modelled as a collection of solid polyhedra. The robot links sweep out volumes of space which are approximated by volumes bounded by parametric ruled surfaces. A number of simple tests can be made to determine whether any intersections exist between the swept volumes and the stationary polyhedra, indicating interferance. Much of this fundamental work is incorporated in a preliminary interactive programming software package called AUTOP. The interference detection algorithm is demonstrated by a program called TESTIN.
Affiliation: Applied Science, Faculty of
URI: http://hdl.handle.net/2429/24806
Scholarly Level: Graduate

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