Tipping Point

Early Season Design:

Objective:

In this year's game, two important goals were to stack the mobile goals (red, blue, & yellow heptagons ) onto the seesaw platforms, and to score rings onto the poles of the mobile goals. This year there would be both solo skills runs (autonomous programming & remote control driving) as well as competitive matches versus other teams. Our objective was to be highly efficient in our building, and to make multiple robot designs to keep up with the latest competitive robot trends.

Brainstorming process:

We researched robotics competitions with similar elements, and decided on a four wheel drive base powered by four motors. We used another motor for a front four bar that would allow us to lift the mobile goals onto the platform and a rear tilter that angled the goals so that the rings could be scored onto them using our conveyor. We chose a vertical conveyor because at the time, the approach seemed to be most effective and used our last motor to build a spike which would allow our team to score rings on the high branches of the yellow goals. We also decided to use pneumatics for the front clamp.

Assembly:

Assembly of the the drive base went smoothly. By splitting up the work, our team was able to build the front four bar and the conveyor very quickly. However, the conveyor proved difficult to build. We cycled through several different lexan shapes to maximize ability to pick up the rings before settling on an arrow-shape. Additionally, it took a fair amount of trial and error to get the back tilter to line up with the conveyor. The spike also had to be carefully mounted so that it would line up at the perfect height and angle with the higher branches of the yellow goal. In order to build the front clamp, we needed to learn how to use pneumatics. Finally, we used proportional, integral, and derivative feedback control to effectively code the robot and in order to make the autonomous driving very precise.

Results:

Our robot worked reasonably well, and we were able to qualify for the NJ State Championship early in the season. However, we noticed several weaknesses in our robot. The spike was largely ineffective, requiring too much precision and time to use. Additionally, our robot lacked the power to drive up the platform, a method of scoring that proved to be very important. Finally, the rings were largely ineffective, and only worked around 50% of the time.

Building the spike

Final design from the front

Final design from the back

Midseason Design:

Objective:

Given our early season experience, our new objectives were straightforward. Our goals were to be able to reach the yellow mobile goals more quickly during the initial autonomous period during matches and to be able to drive up the ramp. We also wanted to score rings more effectively and build a stronger pneumatic clamp. Finally, we wanted to focus intently on the Skills aspect of the competition as we believed this would grant us the best chance to qualify for the World championship.

Brainstorming process:

In order to power our robot to drive faster and get up the ramp, our team decided to build a six motor drive and modify the gear ratios in the drive base to be much faster. However, this approach left us with only two remaining motors to perform the other tasks. The lift and the conveyor had to be powered by motors, which meant that we needed to use pistons for the rear tilter. We also opted for a diagonal conveyor that dropped the rings over the pole instead of violently flinging them on like the previous design. Finally, we decided to use a locking clamp to make the front clamp stronger.

Assembly:

First, our team built the drive base. It was quite difficult to fit all six motors in, but we were able to make it work. We built a four bar that was similar to our prior version, but we moved it back so that we had a greater range of motion. The diagonal conveyor was quite intuitive to build and it immediately worked much better than the vertical one. We were able to get the rear tilter to work by using two double action pistons, which both clamped onto and tilted back the mobile goal in one actuation. The most innovative part of our robot, however, was our locking clamp. Using the geometry of an asymmetrical four bar, we were able to create a shape that locked the clamp into place. Even if the mobile goal that the clamp holds was pushed up, it was physically impossible for the clamp to release unless the metal was bent or if a person actuated the piston, releasing the mobile goal. This attribute was extremely useful as it meant mobile goals could not be stolen from us. Given the success of our previous code, we followed a similar approach for this next iteration. However, we devoted much more time to refining coding with this robot in an attempt to achieve our Skills goal. I also practiced driving a lot to be fully prepared for competition.

Results:

Success! Our team performed extremely well at the NJ State Championship. We placed 1st overall in qualification matches, and placed 1st in Skills for New Jersey. We also won the Excellence award (top overall award for innovative design, autonomous programming & remote control driving), double qualifying our team for the World Championship. Furthermore, our 1st place Skills score was high enough to rank us 17th in the World! Even so, there were still a few improvements that could be made. We faced a significant tipping issue, and I had to be very careful when driving to avoid getting stuck on rings.

Diagrams demonstrating how the locking claw functions

The final product

NJ State Championships, Two Awards

Final Design:

Objective:

Although our robot moved quickly in our initial rush to clamp the mobile goal, we knew that to compete on the world stage, it would have to move even faster. Our goal was to secure the yellow goals as soon as possible during the autonomous period of the match. Additionally, we wanted to build a robot that was less prone to tipping to make driving and programming easier.

Brainstorming process:

We brainstormed multiple ways to make the robot faster in order to reach the mobile goals before the opposing alliance did so. The first way was to make the robot as light as possible. The second way was by building a goal cover to block the other team from locking onto the goal. However, we did not have any more motors left and we did not want to use pneumatics as we had a limited amount of air each match, so we designed it to work passively by using rubber bands. The third way was by making kickstands, which would allow the robot to start an extra 5 inches ahead of the line by suspending the front of the robot off the ground using standoffs. To prevent the tipping problem, we opted to use smaller wheels so that the distance between the points at which each wheel touched the ground would be larger, increasing our stability. We used CAD to model the drive train to maximize efficiency and to make the robot as lightweight as possible.

Assembly:

Using the CAD of the robot, our team was able to rapidly build the drive. The majority of the design was fairly similar to the 2nd design, but we reduced the robot weight significantly. Splitting up the work, the team was able to quickly build the lift, the back tilter, and the conveyor. We decided to build a new front clamp with optimized geometry and spacing that would clamp onto the mobile goals even more tightly. Next, we built the kickstands which shaved a lot of time off of our goal rush. We once again used proportional, integral, and derivative feedback control to precisely code the robot. Finally, we built what is, in my opinion, the most impressive part of the robot. We designed and built a goal cover that deployed, latched onto the goal, and undeployed entirely using rubber bands. There were 3 separate stages of rubber bands that released using the motion of the drive base and the movement of the lift.

Results:

Success! We made it to the quarter finals in our division at the World Championship! This was the best outcome that any team in our robotics organization has ever achieved, and my team and I are very proud of our work. We also placed first at a multi-state VEX U tournament even though we were competing against college teams that were allowed to fully customize parts and use more motors and pneumatics.

Goal Cover in starting position before the match begins

Goal cover deployed after the spinning of the drivetrain releases the rubber band holding the cover down

Goal cover returned to the upright position after the lift is raised, releasing the rubber bands holding the cover down

CAD of the drive base

Building the drive base

Final World Competition robot design

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