We were tasked wtih creating a line-following robot that senses light along the line.The idea was to have the robot guide a plant along the line so that it would always have optimal sun conditions. We decided to make a circular robot. In the interest of having as few motors as possible, we decided to make it have only one driving wheel and a servo that would turn it.
Our robot has a wheel and motor in the center that are connected to a disk which spins freely from a servo. To save space we have the motor right alongside the wheel, the wheel has a gear cut into it which attaches to the motor. The servo connects it to an outer circle which has other wheels for stabilization. Originally the outer wheels were casters which spun in all directions. We changed these to more traditional wheels. The center wheel is much bigger then the outer wheels so we had to put spacers under them to make them the same.
In the first iteration we had casters on the outer disk. This allowed for a much smoother ride. The casters could move in all directions, unfortunately this was a problem. Since the casters were easier to spin then the center wheel the servo ended up spinning the outer disk around the inner one, instead of the other way around. We decided to change the casters to 3D printed wheels. These were much harder to turn side to side, so we stopped having the servo problem. This made our robot move significantly slower though, because not all the wheels could be facing the right way all the time.