Two robots on each side of the field were locked in a fight at the centerline barrier to push a massive exercise ball. Finally, one robot — that of Community’s 5708 Zebrotics team — slammed the ball off the field. The other side’s robots maneuvered to push the ball back, but with only a few seconds left, the ball stayed trapped.
The siren for the end of the match sounded. A few moments of suspense settled in for the teams as the points were tallied. Zebrotics were pretty sure they had won, but there was no way to be sure.
When the score for the final round of the playoffs came in, Zebrotics was cheering for a victory. They had expected to perform well with the robot they built from scratch in their first Washtenaw Area Pickup Robotics (WAPUR) competition, but they did not expect to make it to the end.
On Dec. 8, Zebrotics competed in the WAPUR competition with other FIRST Robotics Competition (FRC) teams at the University of Michigan Sports Coliseum. Essentially a match of beach volleyball with an exercise ball and two robots on each side, each side could get more points the less the ball was on their side, and by kicking the ball across to the other side.
“This competition is just for training and practice,” said Christia West, the lead mentor and CHS Science teacher. “It’s like when boxers prepare for a competition; they have a sparring partner. We are doing all the things we would do during the season but scaled down. [New students] can see the whole process, so when we hit the kickoff, they know what’s going on.”
The team began designing their robot by brainstorming a variety of ideas for the mechanism that would push the ball, such as a rotating shaft with a “boot” that would kick the ball. Next, they prototyped the best concepts with simple materials. Eventually, the design simplified to a rotating lever flanked by duct tape-plastered yard sticks that kept the massive ball from rolling off to the sides of the robot.
“How simple can we make this, and still have it do the job?” West said.
The chassis of the robot was an old spare, refitted with mecanum wheels; with a set of rollers attached to it, such wheels can drive in any direction. Though they have little traction and are easily pushed around, the mobility of the mecanum wheels allowed the robot to slide into position to kick the ball to the other side of the field.
After the opening ceremony, WAPUR initiated with a set of qualification matches, with Zebrotics winning three out of five matches, and even doing so without the other team scoring. Zebrotics charged the ball at the beginning of each round, jostling the ball onto the other side. The mecanum wheels allowed their robot to slide into position to stop the other side’s attempts to push the ball over the centerline barrier. Zebrotics’ lever mechanism — built specifically for the competition — consistently hit the ball onto the other side. On the other hand, more complicated grabbers on other robots — mostly built during the previous season — struggled to grasp a ball much larger than the ones they were designed for.
Even during the losses, the robot continued to perform smoothly. When the robot trapped itself on the barrier, it managed to break free by the end of the match.
“Our team is especially good at just sort of moving forward despite the problems so I’m less nervous for the coming season,” Clemetson said.
After a pizza-laden lunch and the last set of qualification matches, it was time for the alliance selection. Here, the top teams select a partner team to play with them in the playoffs. 5708 Zebrotics was selected as a partner of 5067 Steiner Steel Storm of Rudolf Steiner School.
Throughout the playoffs, the two allied robots complemented their strengths and weaknesses leading to victory. 5067’s massive swiss cheese board resisted charges by the opposing alliance, which included 1506 Metal Muscle, a team that competed in the FRC world championship in the previous season. 5708 then moved into position to send the ball across the barrier, and the ball remained trapped as the remaining seconds on their clock drained to zero.
WAPUR is foremost an inexpensive, low-stakes opportunity for teams to train new students for the upcoming FRC season.
“The biggest thing was how my team prepared for the competition,” West said. “All the students on the team are there to really learn and have fun and participate in this amazing opportunity and community.”
In West’s opinion, the design philosophy the team followed during WAPUR will serve the team well in the upcoming season, when Zebrotics participates in two competitions at Belleville and Livonia on Mar. 13-14 and 27-28 respectively.
“Simple always wins,” West said. “We came up with a really simple design, we executed it and it’s really robust. With a lot of engineering solutions, simplicity often wins over complexity.”