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This Robot makes use of the 3D accelometer as 3D tilt sensor. Tow separated PID controlling algorithms were implemented to work in the same time. Each algorithm control one of the servo motors. the plastic panel at the top of the platform should be in level and parallel to the ground. These servo motors will try to keep this panel in this orientation incase of tilting the platform right side, left side or inclination.
This is a companion discussion topic for the original entry at https://community.robotshop.com/index.php/robots/show/2-dof-balancing-robot