A method for collision handling for industrial robots

University essay from Linköpings universitet/Institutionen för systemteknik; Linköpings universitet/Institutionen för systemteknik

Author: Fredrik Danielsson; Anders Lindgren; [2008]

Keywords: Collision;

Abstract:

This master's thesis presents the development of a collision handling function for Motoman industrial robots and investigates further use of the developed software. When a collision occurs the arm is to be retracted to a safe home location and the job is to be restarted to resume the production. The retraction can be done manually, which demands that the operator has to have good knowledge in robot handling and it might be a time consuming task. To minimise the time for restarting the job after a collision and allowing employees that have limited knowledge in robot handling to retract and restart the job, Motoman provides an automatical retraction function. However, the retraction function may cause further collisions when used and therefor a new function for retracting the arm is needed. The new function is based on that the motion of the robot is recorded by sampling the servo values, which are then stored in a buffer. A job file is automatically created and loaded into the control system, and the position variables of the job file are updated using the contents of the buffer. This will ensure a safe retraction of the arm as long as the environment surrounding the robot remains the same.

The developed software made it possible to control the robot in real-time by changing the buffer information, which has lead to a cognitive system called the Pathfinder. By initiating the Pathfinder function with at least a start and an end point, the function generates a collision free path between the start point and the end point. A pilot-study has also been made concerning integration of a vision system with the Pathfinder to increase the decision handling for the function.

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