For this project we created a robot that makes a coin disappear right before your eyes. The trick starts off with the robot moving forward and grabbing a clear cup with a tissue placed over it. The robot then moves this cup on top of the coin. It then releases the cup and backs up to allow the assistant to remove the tissue and reveal that the coin has disappeared. The tissue is then placed back on the cup and the robot picks it up. It then moves back to reveal that the coin is back in its original position.
The robot has three main mechanisms. The first one is the propulsion system which consists of two wheels attached to two separate large motors at the back of the EV3 brick. The two wheels are joined by a single axle to ensure that the movement is kept straight and on track. The second mechanism is the crane arm at the front of the brick, this is what allows the robot to lift the cup up after it has grabbed it. The crane arm is made up of a large motor which has two long Lego pieces extruding out. These Lego pieces each have their own attached Lego pieces, which point toward the ground and have mini-wheels to act as a balance. The large motor has two small pieces attached to the top in order to stop the arm from going too far back. The third mechanism is the claw hand attached to the end of the crane arm, this allows the robot to grasp the cup. It is basically a medium motor attached to a worm gear with two axles on either side which are then attached to curved Lego pieces via axles. This translates the rotation of the motor into a grasping motion by the curved Lego pieces. The cup had two holes cut near the top in order to allow the claw to get a good grip.
The program for the robot was written in LabVIEW. It consists mainly of starting and stopping different motors after a certain “wait for” parameter is reached. The code allows the robot to complete the trick by itself from start to finish (aside from the movement of the tissue by the assistant). The trick behind the magic in this case is that the cup has a piece of paper glued to its underside which matches the color of the surface. Once the cup is placed ontop of anything flat, like a coin, it gives the illusion that the coin has disappeared when in reality it is simply under the fake cup bottom.
The Magic Trick