Prototypes
Paddle Wheel Prototype
In order to test whether the paddle wheel idea would be able to collect balls, a prototype using a paint roller, foam core, and cardboard was made. As the video below shows, it was able to pick up a large number of balls simultaneously. Since the paddle wheel was passive, it would run right over stationary balls and push them upward along a curved surface behind the wheel. We did not have to worry about pushing balls away because it was not motorized.
Lead Screw Prototype
While the paddle wheel was able to pick up the balls, we still needed a way to transport them high into our ball container. We experimented with lifting up a platform containing the balls deposited by the paddle wheel using lead screws. As can be seen in the video below, the prototype platform was able to be lifted, but it was too slow to be effective. The robot would not be able to collect balls while the platform was lifting or lowering, so the lead screw idea was not seen as a viable option.
First Vehicle Prototype
Since the lead screw platform idea did not work out, we needed to come up with a different way to transport the balls from the paddle wheel into the container. We decided to install a fan into the ball container so that the balls could be sucked up into the box using the difference in air pressure. Our first prototype, including the passive paddle wheel and the fan, can be seen in the video below. This prototype was successful in picking up balls, but its container could not hold as many balls as we would have liked, and it easily jammed.
Larger Box Prototype
Much of the space in our first vehicle prototype was wasted, so we decided to try prototyping a larger ball container. This was done by combining the original container with a cardboard box. We were concerned that the fan would have problems sustained the pressure difference with a larger box, but that ended up not being an issue. It was able to pick up balls just as easily as the prototype with the smaller container. The prototype can be see in the image to the left.
Final Robot Design
In order to incorporate the larger ball container, and design an intermediate ball holding area that was less likely to jam, we decided to rebuild the robot with a modified design. The main difference was the larger box, and the decision to move most of the electronic components to the top of the ball container.