MAE Faculty Awarded Patent on New Application of CMG Technology
Dr. Brij Agrawal and Dr. Jae Jun Kim, left to right, stand in front of their control moment gyroscope (CMG) test bed in Halligan Hall, April 13. The two Graduate School of Engineering and Applied Sciences faculty, along with Military Faculty member Air Force Col. Timothy Sands, were recently awarded a patent on a method to propel and maneuver satellites in a quick fluid motion using CMG technology.
Titled "Method and Apparatus for Singularity Avoidance for Control Moment Gyroscope (CMG) Systems Without Using Null Motion," Agrawal and Kim say the basic idea behind the invention is about maneuvering spacecraft quickly with expected results.
"There are two ways to move satellites. You can use thrusters to help move it from here to there, or use our method using CMGs," said Kim. "The CMGs spin very fast and if we change the speed on one of them, it will create unwanted change on the craft and that is how you create momentum without using thrusters."
The ability to maneuver satellites through its CMGs is not as simple as spinning the wheels to get where you need to be at the push of a button.
"The problem is that, at certain gimbal angles and combinations, you cannot create the torque that you want," explained Kim. "Mathematically, if you hit on this surface, you lose torqueing capability so you cannot control it anymore."
This region of problematic combinations, known as a Jacobian Doughnut, became the source for the researchers' solution, developing a systematic way to counter its effect on CMG maneuvers.
"We noticed that, on this surface you lose torqueing capability, but if you go through that surface, there is another area that is like a hollow donut. As long as you pass through, you're okay again," said Kim. "So what we did is we developed a technique that can transit through this singular surface without slowing down or having unwanted results."
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