Twin sisters build robotic prosthetic arm for national competition

Twin sisters build robotic prosthetic arm for national competition

(Jeffrey D. Allred, Deseret News)


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OGDEN — Twin 14-year-old sisters built a functioning robotic prosthetic arm that qualified them to compete in a national engineering competition this week at Weber State University.

Jasmine and Karina Rubalcava built the arm out of string, springs and a mannequin model hand for the Mathematics, Engineering, Science Achievement district competition last year.

"We wanted to do a challenge because it’s better to do challenges than do something easy, you know?” Jasmine said.

They won first place at the district competition and took third place at the state event in 2015.

But the rules changed for the 2016 competition. The prosthetic arms had to be controlled by computer program coding.

The girls redesigned their arm using a cardboard tube, light sensors and a servo motor, altogether weighing around 14 ounces.

Northwest Middle School students and twin sisters Karina and Jasmine Rubalcava demonstrate their prosthetic arm prior to the national Mathematics, Engineering, Science Achievement competition at Weber State University in Ogden on Friday, June 24, 2016. (Photo: Jeffrey D. Allred, Deseret News)
Northwest Middle School students and twin sisters Karina and Jasmine Rubalcava demonstrate their prosthetic arm prior to the national Mathematics, Engineering, Science Achievement competition at Weber State University in Ogden on Friday, June 24, 2016. (Photo: Jeffrey D. Allred, Deseret News)

"It was kind of hard because we didn’t know anything about coding. We just had to do the basics and go with what we had," Karina said.

Amy Boom, a seventh-grade math teacher at Northwest Middle School in Salt Lake City, taught the girls coding after attending a programming training course herself.

"There were many days we were all ready to throw (the project) out the window," Boom said, laughing. "The coding was right, the wiring looked right, but the board still wasn’t working.”

The sisters practiced coding from November to February, starting with turning LED lights on and off. They decided to use light sensors in the final design of their prosthetic arm.

The light sensors were made into a belt the girls could wear to control the arm. When the arm is lowered, sensors read a low amount of light and the prosthetic hand closes. When the arm is raised, the sensors recognized high light and the hand opens.

But the design had to change after the girls were almost disqualified from the state competition for using their arms to manually control the prosthetic. The girls decided to regulate the light sensors by using their chin and nodding.

Northwest Middle School student Karina Rubalcava competes in the national Mathematics, Engineering, Science Achievement competition at Weber State University in Ogden on Friday, June 24, 2016. (Photo: Jeffrey D. Allred, Deseret News)
Northwest Middle School student Karina Rubalcava competes in the national Mathematics, Engineering, Science Achievement competition at Weber State University in Ogden on Friday, June 24, 2016. (Photo: Jeffrey D. Allred, Deseret News)

“We had to change it, so we made (the belt) kind of like a necklace," Jasmine said. "It actually worked better than before.”

The robotic arm had to pass a series of performance events that test dexterity and accuracy. Challenges include throwing a beanbag into a target area, screwing a nut on a bolt and moving objects from one end of a table to the other end.

"Each one of the events has their own difficulty," head judge Phil Gillaspy said. "It depends on the design of their prosthetic arm and hand."

Fifty-three students from eight middle school and nine high school teams from across the country competed in the national competition, held June 23-25. This is the second consecutive year WSU has hosted the event.

The sisters, the only middle school students from Utah in the national competition, weren't too concerned about winning.

"Even if we lose, I think we've done OK. We went to nationals, so that's enough," Jasmine said.

"It was basically to see how far we could go with coding,” Karina added.

The sister's parents, Eduardo and Zulma Rubalcava, are happy their daughters have made it as far as the national competition.

"I feel so proud of them to make it to this point," Zulma Rubalcava said in an email. "I always taught my daughters to follow their dreams, to take every opportunity they have."

Originally from Mexico, the Rubalcava family moved to the United States to help their families, Jasmine said. Though the girls have heard teasing remarks about their race, they aren't afraid to break stereotypes.

"I think everyone should be able to do what they want to do, no matter what kind of race or culture they are from," Jasmine said.

Northwest Middle School students and twin sisters Karina and Jasmine Rubalcava demonstrate their prosthetic arm prior to the national Mathematics, Engineering, Science Achievement competition at Weber State University in Ogden on Friday, June 24, 2016. (Photo: Jeffrey D. Allred, Deseret News)
Northwest Middle School students and twin sisters Karina and Jasmine Rubalcava demonstrate their prosthetic arm prior to the national Mathematics, Engineering, Science Achievement competition at Weber State University in Ogden on Friday, June 24, 2016. (Photo: Jeffrey D. Allred, Deseret News)

Karina is thinking about being a pediatrician when she grows up. She said her inspiration comes from seeing people in need.

"I don’t think it’s just one specific person who inspires me. When I grow up I really want to help people," she said.

Jasmine said she's inspired by her Catholic patron saint, Joan of Arc.

"Even if people tell me that I can’t do something, I’m gonna do it because that’s what I believe that I want to do," she said.

The girls are going to Innovations Early College High School in the fall.

"Even just the troubleshooting and problem-solving skills that these girls had to go through to get this arm working will help them," Boom said. "It’s very rewarding as a teacher to do something like MESA and watch these kids achieve.”

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