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Universal Robots vision-based LEGO DUPLO stacker

June 7th, 2017 No comments

As part of the Robot Vision course at the Institute of Electronic Systems at Aalborg University we had to develop a vision-based LEGO DUPLO stacker using a Universal Robots UR5 robot, a webcam and MATLAB. Equipped with a robot cell as shown below, the task was to develop a system capable of stacking randomly placed LEGO DUPLO bricks in a certain order.

A detailed description of the project and the development of both the image processing and robot control software, is contained within the project report available here: Universal Robots vision-based LEGO stacker.pdf

Conceptual robot cell layout


Using several image processing techniques, including color segmentation, thresholding, BLOB analysis, feature extraction etc. the system is capable extracting the color, location and orientation of the DUPLO bricks currently present in the camera image. This allows an Universal Robots UR5 robot arm to pick up the brick and stack them in an color-ordered scheme of: red, green, blue, yellow, orange.

The webcam is mounted on the robot arm to avoid having to fixate it anywhere else and to link it up to the tool position. This allows easy calibration between the robot tool frame and the camera frame by using the free-drive mode of the Universal Robots arms, allowing the user to grab the robot arm and move it manually to a calibration spot.

A video demonstration of the project including the calibration procedures is shown below.

The project is Open Source and all resources, including both MATLAB code and the URScript, are available online in the GitHub repository: https://github.com/mindThomas/URRobot-LEGOstacker

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