COBEM99

S22 Mecatrônica

Title:

A 3-D VISION-BASED MEASUREMENT SYSTEM FOR ROBOT CALIBRATION

Summary :

ONE OF THE PROBLEMS THAT SLOW THE DEVELOPMENT OF OFF-LINE PROGRAMMING IS THE LOW STATIC AND DYNAMIC POSITIONING ACCURACY OF ROBOTS. ROBOT CALIBRATION IMPROVES THE POSITIONING ACCURACY AND CAN ALSO BE USED AS A DIAGNOSTIC TOOL IN ROBOT PRODUCTION AND MAINTENANCE. A LARGE NUMBER OF ROBOT MEASUREMENT SYSTEMS ARE NOW AVAILABLE COMMERCIALLY. YET, THERE IS A DEARTH OF SYSTEMS THAT ARE PORTABLE, ACCURATE AND LOW COST. IN THIS WORK IT IS PRESENTED A MEASUREMENT SYSTEM THAT CAN FILL THIS GAP IN LOCAL CALIBRATION. THE MEASUREMENT SYSTEM CONSISTS OF A SINGLE CCD CAMERA MOUNTED ON THE ROBOT TOOL FLANGE WITH A WIDE ANGLE LENS, AND USES SPACE RESECTION MODELS TO MEASURE THE END-EFFECTOR POSE RELATIVE TO A WORLD COORDINATE SYSTEM, CONSIDERING RADIAL DISTORTIONS. SCALE FACTORS AND IMAGE CENTER ARE OBTAINED WITH INNOVATIVE TECHNIQUES, MAKING USE OF A MULTIVIEW APPROACH. THE TARGET PLATE CONSISTS OF A GRID OF WHITE DOTS IMPRESSED ON A BLACK PHOTOGRAPHIC PAPER, AND MOUNTED ON THE SIDES OF A 90-DEGREE ANGLE PLATE. RESULTS SHOW THAT THE ACHIEVED AVERAGE ACCURACY VARIES FROM 0.2MM TO 0.4MM, AT DISTANCES FROM THE TARGET FROM 600MM TO 1000MM RESPECTIVELY, WITH DIFFERENT CAMERA ORIENTATIONS.

Author :

McMaster, Robert S.
Motta, José Maurício S. T.

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