Eraserbot Autonomous Whiteboard Eraser
The Design
Eraserbot was intended to be suspended vertically via a winch while it erased a dry erase board. A key limitation imposed was that we could not simply mount the eraser to a motor and spin it, adding significant challenge to the task of creating a wiping motion. To solve this issue I designed a system of linear gears connected via chain and sprocket to two motors mounted to the eraser that would drive the eraser left and right in a wiping motion. The other major design challenge was making sure our robot did not apply so much force to the board that it lifted itself up off of the surface it was supposed to clean.
When building this robot I had two especially large hurdles- creating a motion for the eraser that wasn't spinning and controlling the force applied to the white board. Our wiping mechanism worked extremely fluidly, allowing us to move the eraser over a larger surface area than many of the other solutions implemented. The other major issue was the force we were applying- it was incredibly easy to push too hard and actually lift the robot off of the whiteboard and moving the robot left and right rather than doing any actual wiping. To ensure this did not happen I used four springs in combination with a linear potentiometer to determine how hard the robot was pressing.
When the potentiometer read a value that meant the eraser was extended too far, and thus lifting the robot off of the white board, we would pull it in toward the robot's center using two worm gears. One such worm gear can be seen in the picture fourth picture above, along with the linear potentiometer. Finally, we added the "tail" to our robot, as seen in the first picture, in order to pull the center of gravity for the robot back and increase the maximum force it could apply before lifting itself off the white board surface. This was added when we noticed during testing that because the robot was being hung it was applying very little normal force to the white board before it was lifting itself up and no longer wiping. This meant that whent he eraser did move it wasn't completely erasing the expo marker. By adding the tail with additional weight we were able to increase the force we could apply to the white board before lifting the robot and successfully erased what was written on it.
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