February 1, 2011
While it's helpful to know what methods have historically worked for controlling a spacecraft, it's even better to have rigorous mathematical analysis that guarantees you can make the craft do exactly what you need it to do. Travis Mercker, an aerospace engineering PhD candidate, has spent much of his graduate career finding that guarantee.
Travis Mercker’s paper, “Rigid Body Attitude Tracking with Vector Measurements and Unknown Gyro Bias,” and his related research, earned him a John Breakwell Student Travel Award to present the paper at the Annual AIAA/AAS Space Flight Mechanics Conference in New Orleans in February of this year. The award, a $1000 travel grant given by the Space Flight Mechanics Committee of the American Astronautical Society, recognizes Mercker’s achievement on the problem of spacecraft attitude control.
"We want to prescribe the attitude of the satellite and then precisely control it to that position," Mercker said. "My research specifically looks at what realistic measurements we have available from sensors on the spacecraft and how to use them to control the system."
Mercker said the technical issue he and his advisor, Dr. Maruthi Akella, are working on is well-established: engineers need to be able to orient a spacecraft toward a particular direction regardless of where it is pointed or how fast it’s moving. Most current methods rely on algorithms with empirical measures. But Mercker's paper offers a better method because of its certitude: he and and Akella have derived a mathematical proof for a technique that guarantees accurate attitude control in every situation except in a very small well-characterized set of conditions.
"From a practical standpoint, I have a theorem that proves that, subject to these conditions, I can control my satellite every single time, no matter what happens," he said.
Mercker became interested in this area of research in his senior year while an undergraduate in UT's aerospace program. He had always had a general interest in aerospace, but after taking a class on flight control systems with Dr. Robert Bishop, he knew exactly what he wanted to investigate further.
"Just the idea that you can take a system that's inherently unstable— it's just not going to do what you want it to do—and then design a control system that is able to control it is something I found to be more interesting than anything else I had done," he said.
After getting his BSAE in 2006, Mercker stayed at UT to earn his MSE in 2008 and now expects to finish his PhD in spring of 2012. As a SMART (Science, Mathematics and Research for Transformation) fellow receiving a stipend for his research from the Department of Defense, Mercker will owe three years to Air Force Research Labs at Wright-Patterson Air Force Base in Dayton, Ohio, after graduation.
