Our State design looked like this. After taking notes on what happened in the county competition, we decided to make some changes to our original design. Our main change was the way the platform operated. Instead of having a flat platform like it did before, we left it open and added a linear motion slide that acted like a pole that could push out the small ball that was collected and hopefully be enough to push it into the tube to score extra points.
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Basically the way it was structured, the whole robot lifted up like a wedding/layered cake, which is how we described it as, with a large outer layer and then smaller and smaller inner layers that snugly fit inside it. The claw/arm had two joints, on at the elbow and one at the wrist, where it could move up and down to put the cones in place. An added benefit we had in using the claw was that we were also able to pick up cubes to a certain point. In order to reach a height of 5 stacked cones, we added an extra layer inside, a total of 4 layers, in the form of a differential with a turntable on top. One of the things we made sure to implement in our design was the fact that our robot didn't have to move a single bit as it was building the Skyrise tower. The whole time, the robot is stationary, only repeating a set of actions like if it would be a factory robot. This increased accuracy and saved time in the long run. It also helped when programming the robot for the Autonomous Skills Challenge, which is something we took more seriously that year than we did in the Toss Up season. Basically all the robot did in the Autonomous Challenge was build the Skyrise tower until the time ran up. It was in our county competition that our robot won the Design Award and earned a spot in the Maryland State Competition.
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For the Maryland State competition, this was how the robot looked like. We decided to change the arm system because it was evident in the county competition that it was way too complex to control and program as it had two different joints that needed to be synchronized and that ate up too much of the actual competition time to get it in exactly the right position. So, it was changed to a kind of linear sliding claw. It was faster, more efficient, more accurate, and it was way easier to program compared to what we had before. It was also lighter on the structure, since we took away the differential and turntable, which at this point weighed nearly 20 pounds! It was a definite improvement. We also decided to add another mechanism on the back: a kind of hook that was attached to a worm gear for strength that allowed us to pick up the cubes with better grip. We also added gearboxes with more worm gears and attached them to the gears that were lifting up the outer layer since without them, the structure started getting stuck and falling back down whenever we lifted up the lift. At the State competition, we performed fairly well! Although we didn't make to the finals, we did score high in the Autonomous Challenge! Despite this, though, Elizabeth's dad didn't think that we would be able to advance to the World competition. However, Elizabeth insisted that she and her dad stay to here the results, and sure enough, our ranking in the Skills Challenge was high enough that we scored our first ticket to the World Championships! You can imagine how excited she and her dad were to tell the news to Stephanie and their mom at home!
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Our design for the World Championship didn't vary that much from the State design. One of the main differences was that we changed the linear sliding head from using linear gears to a chain and sprockets for smoother and faster travel. We also wanted the lift to be faster and more efficient, so we kept the motors in the outer layer, but took away the other motors in the inner layers and then connected them together with rope. This way, the whole thing becomes one system.
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This year we mainly focused on the shooters and making the system mostly autonomous. The theory was that if one ball could make it into the top net, and no one changed any variables, then all the balls that followed would follow the same trajectory. The shooting system consisted of two rubber regular wheels spinning in opposite directions to provide the thrust needed to launch the balls into the nets. Then on the base where the balls would be located, we had a conveyor belt that would carry the balls all the way into the shooting system to be launched. The whole robot followed a repeated system of prep, carry, and shoot. On the base of the robot we had three wheels connected by a string of gears and one motor on each side. We had decided that the best plan of action was to stay where we were and launch the objects from that space. After all, the starting grid was the optimal place to start launching from.
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This is the final product of our robot. We replace the rubber wheels, for two sprocket gears coated in rubber bands. This was better because it provided more traction between rubber ball and shooter and thus provided the most thrust. However the down side to this was that the rubber bands could at some points randomly break apart. This meant that we would have to replace them or else there would be another variable that might affect the way the ball was shot.
The main problem we had was the battery level. You would be surprised how much just one percent less battery effected the robot and how it launched each ball. What happened was that the battery would die too quickly and therefore the motors would lose power. No matter how fast the gears were spinning they wouldn't be able to spin if there was no power. We tried connecting a second battery and the extra 9 volt battery, but the problem didn't seem to be getting any better. We had probably spent twice as many nights awake than any year before. However we plowed through and did out best with what we built and knew. |
This is what the final product looked like. When the claws were retracted, it was barley just able to fit within the 18" by 18" by 18" restrictions. The long claws were perfect for grabbing multiple stars and the 12.5" cube. The unique three armed claw was better at grabbing the oddly shaped stars no matter what position they were in. On the back we had a simple lift with three motors on each side for maximum power. After all with the weight of the stars, cubes, and the actual, everything was pretty heavy for the robot to handle. However we solved that problem by changing the gear ratio to fully make use of the extra power it provided. The chain on the top of the arm of the lift was a cushion so that the impact of the arm slamming against the fence would be lessened and the arm supported. Later on at States we changed these chains to a diamond shaped support made up off various small pieces.
Also you may not see it from the way the pictures are angled, but on the back of the robot were multiple rubber bands connecting from the arm of the lift to the base of the robot. This was an important design detail, because without these rubber bands helping to support the weight of both scoring objects, arm, and claw we wouldn't be able to lift the arm as fast as we could. There were on multiple occasions that the rubber bands would fall off because of the lift going to far backwards, but this was just another challenge for the driver to think about as she was driving the robot. |
At the last 30 seconds of a match, teams are allowed the option to high hang from a 30" high vertical PVC pipe located in the corner of your alliance's field. Our robot was able to do this, although admittedly not all the time. The difficult part was figuring out a mechanism that was able to support the 14 pounds that was our robot, while not using any motors. What we came up with was a flexible hook that grabbed onto the edges of the pipes opening and used the power of the lift to pull to robot up. However even with the modifications we made to the robot to support this design, the motors were just not strong enough to lift up the entire robot 100% of the time. Fortunately about 60% of the time the lift was able to pull itself up in the last minute and score those few necessary points needed to win a match.
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