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Spherical Induction Motor Eliminates Robot’s Mechanical Drive System
PITTSBURGH— More than a decade ago, Ralph Hollis invented the ballbot, an elegantly simple robot whose tall, thin body glides atop a sphere slightly smaller than a bowling ball. The latest version, called SIMbot, has an equally elegant motor with just one moving part: the ball.
The only other active moving part of the robot is the body itself.
The spherical induction motor (SIM) invented by Hollis, a research professor in Carnegie Mellon University’s Robotics Institute, and Masaaki Kumagai, a professor of engineering at Tohoku Gakuin University in Tagajo, Japan, eliminates the mechanical drive systems that each used on previous ballbots. Because of this extreme mechanical simplicity, SIMbot requires less routine maintenance and is less likely to suffer mechanical failures.
The new motor can move the ball in any direction using only electronic controls. These movements keep SIMbot’s body balanced atop the ball.
Early comparisons between SIMbot and a mechanically driven ballbot suggest the new robot is capable of similar speed — about 1.9 meters per second, or the equivalent of a very fast walk — but is not yet as efficient, said Greg Seyfarth, a former member of Hollis’ lab who recently completed his master’s degree in robotics.
Induction motors are nothing new; they use magnetic fields to induce electric current in the motor’s rotor, rather than through an electrical connection. What is new here is that the rotor is spherical and, thanks to some fancy math and advanced software, can move in any combination of three axes, giving it omnidirectional capability. In contrast to other attempts to build a SIM, the design by Hollis and Kumagai enables the ball to turn all the way around, not just move back and forth a few degrees.
Though Hollis said it is too soon to compare the cost of the experimental motor with conventional motors, he said long-range trends favor the technologies at its heart.
“This motor relies on a lot of electronics and software,” he explained. “Electronics and software are getting cheaper. Mechanical systems are not getting cheaper, or at least not as fast as electronics and software are.”
SIMbot’s mechanical simplicity is a significant advance for ballbots, a type of robot that Hollis maintains is ideally suited for working with people in human environments. Because the robot’s body dynamically balances atop the motor’s ball, a ballbot can be as tall as a person, but remain thin enough to move through doorways and in between furniture. This type of robot is inherently compliant, so people can simply push it out of the way when necessary. Ballbots also can perform tasks such as helping a person out of a chair, helping to carry parcels and physically guiding a person.
Until now, moving the ball to maintain the robot’s balance has relied on mechanical means. Hollis’ ballbots, for instance, have used an “inverse mouse ball” method, in which four motors actuate rollers that press against the ball so that it can move in any direction across a floor, while a fifth motor controls the yaw motion of the robot itself.
“But the belts that drive the rollers wear out and need to be replaced,” said Michael Shomin, a Ph.D. student in robotics. “And when the belts are replaced, the system needs to be recalibrated.” He said the new motor’s solid-state system would eliminate that time-consuming process.
The rotor of the spherical induction motor is a precisely machined hollow iron ball with a copper shell. Current is induced in the ball with six laminated steel stators, each with three-phase wire windings. The stators are positioned just next to the ball and are oriented slightly off vertical.
The six stators generate travelling magnetic waves in the ball, causing the ball to move in the direction of the wave. The direction of the magnetic waves can be steered by altering the currents in the stators.
Hollis and Kumagai jointly designed the motor. Ankit Bhatia, a Ph.D. student in robotics, and Olaf Sassnick, a visiting scientist from Salzburg University of Applied Sciences, adapted it for use in ballbots.
Getting rid of the mechanical drive eliminates a lot of the friction of previous ballbot models, but virtually all friction could be eliminated by eventually installing an air bearing, Hollis said. The robot body would then be separated from the motor ball with a cushion of air, rather than passive rollers.
“Even without optimizing the motor’s performance, SIMbot has demonstrated impressive performance,” Hollis said. “We expect SIMbot technology will make ballbots more accessible and more practical for wide adoption.”
The National Science Foundation and, in Japan, Grants-in-Aid for Scientific Research (KAKENHI) supported this research. A report on the work was presented at the May IEEE International Conference on Robotics and Automation in Stockholm, Sweden.
Video by: Carnegie Mellon University
About Carnegie Mellon University: Carnegie Mellon (www.cmu.edu) is a private, internationally ranked research university with programs in areas ranging from science, technology and business, to public policy, the humanities and the arts. More than 13,000 students in the university’s seven schools and colleges benefit from a small student-to-faculty ratio and an education characterized by its focus on creating and implementing solutions for real problems, interdisciplinary collaboration and innovation.
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May 17, 2016 — When Jacqueline Leonard proposed a program that would introduce gaming and robotics into public school classes to help improve mathematics learning, the University of Wyoming College of Education professor hoped it would be a tool for students to become interested in college careers.
Three years later, the project has shown positive results among the original eight Wyoming schools that were introduced to the Innovative Technology Experiences for Students and Teachers (ITEST) program. The National Science Foundation (NSF) supported the three-year, $1.2 million grant.
The “Visualization Basics: uGame-iCompute Project” was designed to help teachers engage fifth- through ninth-graders in gaming and robotics to promote interest in science, technology, engineering and mathematics (STEM) programs.
UW’s project has engaged elementary and middle school students in at least 24 Wyoming schools since the ITEST program was first introduced in 2013. Some school districts have participated in the program since year one of the three-year project, and nearly 900 students have participated during that time.
The eight original schools participating were Arapahoe Middle School, Laramie Junior High School, Powell Middle School, University Park Elementary School (Casper), UW Lab School, Wheatland Middle School, Worland Middle School and Wyoming Indian Middle School. Since then, seven and nine school districts, respectively, have joined the program in years two and three.
“Robotics and game design were used as a hook to enhance children’s interest in STEM and STEM careers. We also were interested in developing computational thinking skills and the processes that we know students need to be successful in computer science and engineering,” Leonard says. “Finally, we wanted children to understand how mathematics, technology and communication are critical to 21st century careers.”
Leonard, UW Science and Mathematics Teaching Center director, originally put together a multidisciplinary team from the UW colleges of Education, Engineering and Applied Science, and Arts and Sciences to research a question that has been part of her research agenda for several years: Can gaming and robotics be used to teach computational thinking skills to students in culturally sensitive ways?
“I am so thankful for this program. What a great way to get students prepared for possible careers in their future. Many of the jobs that students will have after they graduate haven’t even been created yet,” says Kait Quinton, who teaches seventh-grade math at Rock Springs Junior High School. “This program helps to enhance students’ critical thinking skills in a way that is fun and interactive. They learn so quickly. It is incredible, because I feel like I teach them the foundation of robotics and game design, and they just take it and run. By the end, they are the ones teaching me.”
During the multiphase project, team members first trained teachers to develop mathematical and scientific lessons that were culturally relevant to their students. Leonard and her supporters worked with the teachers to analyze the impact on students’ overall learning. The research team also worked with participants interested in becoming peer trainers to help extend the project’s reach after the grant period ended.
Program’s Positive Results
“The data reveal that using intact classrooms at the middle school level and elementary students during after-school programs reduced student attrition and ensured broader participation of girls and underrepresented minority students,” Leonard says.
Additionally, UW researchers have observed improved student development of computational thinking skills and problem-solving skills. Leonard says, early in the project, there was a learning curve that teachers and students had to overcome to learn the programming and software.
“Overall, students learned how to make their own games, which involved formulating problems, abstraction, use of algorithms, logical thinking, analyzing and debugging, and generalizing and transfer of knowledge,” Leonard says. “They also learned to use 21st century skills as they worked in teams to solve problems and created products for self-enjoyment and competition.”
Ty Ruby, who is a fourth- and fifth-grade special education instructor at North Evanston Elementary School, says the robotics and gaming program taught his students to work together on projects. He introduced the robotics class at Clark Elementary School.
“I believe this is a great program for students. I was so impressed with how the students worked together. Their conversations about how to solve issues or problems they were having were the best,” he says. “This provides a safe environment for students to talk about ideas with programming and working together. The students reacted really well to the program. They were excited to come to school and work with their robots.”
Robotics teams compete at local competitions, and gaming teams have taken field trips to the National Center for Atmospheric Research-Wyoming Supercomputing Center in Cheyenne. Teachers accepted into the program enrolled in continuing education courses, led after-school programs, and further developed instructional skills on how to incorporate cultural uniqueness into fun science and technology projects.
The NSF-sponsored grant has ended this semester, but Leonard says her research team has actually been granted a “no-cost extension,” meaning that the project will end during September 2017. Planning for the next phase of the program is underway, she adds.
“We intend to go to more school districts and work with both elementary and middle school students,” Leonard says. “It has been a pleasure working with teachers and students in Wyoming. The excitement and energy observed in the classrooms and after-school clubs were infectious. The students loved the program and learned a great deal.”
For more information about the program, visit the website at www.ugameicompute.com/ or contact Leonard at (307) 766-3776 or firstname.lastname@example.org.
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