Engineers develop deft solution to keep robots oriented in space

To keep a repair robot stable while fixing satellites in space, University of Cincinnati engineers took a page from experts in balance: bull riders.

UC College of Engineering and Applied Science graduate student James Talavage and Professor Ou Ma looked for simple but effective ways to maintain a robot's orientation while working on a broken satellite in zero gravity.

And just as a bull rider uses a free arm for balance, the aerospace engineers found that inertia generated by a second robotic arm kept both the robot and the satellite stable in simulations of in-space service, assembly and manufacturing.

Talavage and Ma call the system Dual-Arm Zero Momentum, which minimizes the attitude disturbance to the vehicle being repaired by maneuvering one arm while the other performs repairs. In simulations the robot effectively used a free arm autonomously to correct any yaw, pitch or roll fluctuations caused by its interaction with the satellite.

Ma said making contact with a satellite is a tricky part of the operation. A slight bump can send both satellite and robot careening wildly in different directions.

“Physical contact is always the most difficult and critical part. Physical interactions can cause damage and make the satellite unstable,” Ma said.

They presented their simulation at the American Institute for Aeronautics and Astronautics’ SciTech Forum in Orlando, Florida, this year. The research is supported with grants from the U.S. Space Force.

“I think it’s a very practical solution with the current hardware that we have and the typical conditions for servicing satellites,” Talavage said.

Ma said the robot responds much like a person does while learning how to ice-skate.

“Think about standing on the slippery ice. If I ask you to grab something with one arm, I’m sure you’ll use the other arm to balance yourself. It’s unconscious. You do it naturally,” Ma said.

“Our idea is if you have another arm not doing anything, why not use it to make intentional movements to cancel out reactions for balance?”

Ma studies solutions to these problems in his Intelligent Robotics and Autonomous Systems Laboratory. In simulations, Ma and Talavage demonstrated that a robot can use a second arm to make adjustments in yaw, pitch and roll autonomously.

Ma said there is financial interest in developing robots that can repair or remove broken or damaged satellites.

Scientists are growing increasingly concerned about dangerous overcrowding by satellites and space debris in low earth orbit. If these objects become too dense, one or more collisions could trigger a cascade of other collisions that would make space travel risky or even impossible. Scientists call this inflection point the Kessler Syndrome. 

“It is definitely something that will have an effect in my lifetime unless we can do something about it,” Talavage said. “There have been previous ventures to demonstrate the de-orbiting or scavenging capabilities from defunct satellites in orbit.”

The late Andrew Barth, an assistant professor, UC graduate and longtime research collaborator of Ma’s, also contributed to the project. He died in 2025.

“He was always willing to put down what he was working on to help you understand something or to help nail down some of the gritty details of our research,” Talavage said.