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A crowd of people watch the ME72 competition in front of the Beckman Auditorium, a round white building with columns

Caltech's Battle of the Bots Returns for 38th Year

March 15, 2023

As with many of Caltech's time-honored traditions, the annual ME72 Engineering Design Competition pushes students to the limits of possibility. Unlike other Caltech traditions, ME72 involves ball-launching, self-driving, all-terrain robots—which occasionally burst into flames.

Every year from September to March, third-year mechanical engineering undergraduates take ME 72, a two-term, hands-on lab course. Advised by instructor Michael Mello (PhD '12), teaching professor of mechanical and civil engineering, student teams each design and build three robots to participate in a unique competition created by that year's teaching assistants (TAs).

This year, the "Rubble Rush: Rabblerousing Racquetball Rustlers" competition on March 9 challenged five teams of five to seven students to build one mobile robot to collect racquetballs from a dispenser, one stationary robot to shoot those balls into goals, and another mobile robot to traverse an obstacle course. Points were awarded for successful goals, and balls worth extra points went to teams whose robots navigated the obstacle course autonomously, without the need for remote control.

A round-robin tournament pitted each team's robots against one another in four-minute matches, and teams that scored the most points advanced to a final bracket playoff.

"I've been surprised by the variety of robots we're seeing this year," said TA Martin Peticco at this year's competition. Peticco's team won the competition last year. "One team is trying to use computer vision to navigate the obstacle course autonomously, and another team is using ultrasonic signals, which work kind of like echolocation."

Students gain the necessary technical knowledge in prior mechanical engineering courses at Caltech. "ME14 was a good starting ground to learn the basics of the engineering process," says Jonah Rolfness, from team Purple Prickly Pineapples. "ME72 is kind of like a beefed-up version of that."

Students begin the class designing their robots in computer-aided design (CAD) software. Then they build prototypes, test, fail, go back to the drawing board, and build again. "Every team goes through the forming, storming, norming, and performing stages of group dynamics," Mello says.

Assisted by co-instructor Paul Stovall, lecturer in mechanical engineering and supervisor of the mechanical engineering shop; and Trent Wilson, lab machining assistant; students spend many hours constructing their robots.

"We advise them on how to manufacture parts, troubleshoot, and fix things that are broken," Stovall says. "Most students spend at least six hours a day in the shop." This time commitment is no easy feat. When asked how long it took to build their three bots, one member from team Candace said it felt like "100 million hours."

Though ME72 is known to take over third-year mechanical engineering students' lives, they come away with invaluable skills. "I had an internship last year at OffWorld, a company that builds smart robots for space and mining applications," says TA Logan Hayes, a fourth-year undergraduate who took the class last year. "ME72 was very helpful in preparing me for that and getting experience in the full design process."

All the students' labor came to fruition on March 9. Cheered on by a crowd of Caltech peers and around 40 visiting students from Sierra Madre Middle School, teams faced off on the grassy battlefield of Beckman Mall. Mello and competition announcer Gunnar Ristroph (BS '06) narrated the play-by-play for the audience.

In an energetic start to the day, team MechE Wednesdays faced off against team [REDACTED]. MechE Wednesdays employed the unique strategy of parking their shooting robot under the racquetball dispenser, allowing it to collect balls with an extended arm and volley off goal shots immediately. [REDACTED]'s robots were among the most reliable of the bunch but couldn't manage to outscore MechE Wednesdays.

In the second match, team Squeezable and Bouncy started off with a strong lead against Purple Prickly Pineapples. But in the middle of play, one of Squeezable and Bouncy's robots caught fire and an acrid smell filled the air. A TA swooped in and removed the bot's battery to a round of applause from the audience.

Eighth-grader Angelica Melchor and her classmates enjoyed the action from front-row bleacher seats next to the course. "It's super cool to see what Caltech students can build," Melchor said. "I'm on the robotics team at school, and I'd love to go to Caltech someday and do this competition."

From 11 a.m. to 3 p.m., robots brawled, and occasionally, broke. Teams took timeouts as needed to repair their beloved bots with names like Dumpy, Turnip Truck, and Optimus Prime. Sierra Madre Middle School students kept the energy high by chanting the names of the teams and their members, and curious bystanders walking through campus stopped to watch the chaos unfold.

Eventually, the round-robin came to an end and finalists advanced to the playoff bracket. Team Candace did not make it to the semifinals, but the other four teams still had a chance to stake their claim for the trophy. MechE Wednesdays and Squeezable and Bouncy outperformed Purple Prickly Pineapples and [REDACTED], with Squeezable and Bouncy setting a short-lived record high number of points in the day during their semifinals match.

The highly anticipated final match came down to the top-scoring, resilient bots of Squeezable and Bouncy versus the undefeated goliath MechE Wednesdays. At the start of the play, it seemed like a toss-up, with each team shooting countless goals and earning bonus balls for navigating the obstacle course. But halfway through the match, Squeezable and Bouncy once again ran into trouble. Their obstacle course robot lost one of its treads, and their ball-collecting bot flipped to its side, unable to drive. As the school kids in the audience screamed, Ristroph shouted into the microphone, "It's carnage out there!"

MechE Wednesdays continued scoring and racked up 481 points, setting a new all-time record for points in the competition and taking the championship. The audience erupted into cheers as MechE Wednesdays collected their gear-shaped trophy, hoisting it into the air.

"It feels great to win," said team member Nico Jimenez. "We put many, many hours in over the last two terms, but it's all been worth it. We wanted to put our best foot forward and represent our team and Caltech. We are really proud of our work."

Jimenez added that ME 72 is the most informative and valuable class he has taken at Caltech so far. "The real-world engineering takeaways that I gained are not something I could learn from any other class, so I'm really thankful to have this experience," he said.