Robonaut Lends a Hand

Everyone could use an extra set of hands now and then, and if two Rice researchers and a crack team of scientists at NASA’s Johnson Space Center (JSC) have their way, astronauts aboard the International Space Station might have just that in Robonaut.

Marcia O’Malley, assistant professor of mechanical engineering and materials science, with Robonaut.

A humanoid robot, Robonaut will function as a second set of eyes, arms, and hands on spacewalks. Two Rice assistant professors—Marcia O’Malley of mechanical engineering and materials science and Nancy Niedzielski of linguistics—are working on the project, a collaborative effort between NASA and the Defense Advanced Research Projects Agency. The project is based at the Robot Systems Technology Branch at JSC.

NASA chose to build a humanoid robot because spaceflight hardware has been designed for construction and servicing by astronauts. Robonaut won’t be replacing astronauts, however, and it won’t be able to “think” for itself. Instead, it will be attached to the robotic arm of the space shuttle or space station and will be remotely operated by an astronaut inside the spacecraft using a 3-D virtual-reality helmet and two joysticks. The operator will see what Robonaut sees and feel what it feels outside the craft and will be able to control its movements accordingly.

Although the concept sounds basic, making a robot duplicate even the simplest of human tasks is extremely challenging. O’Malley’s work on the project involves the “haptic” interface used in the robot’s control system. Haptic, a term that originated in psychology, refers to the perception of touch. Among the myriad sensors on Robonaut—up to 150 in each arm—several allow the astronaut operator to sense where the robot is and the amount of force that it is exerting. Encoding the software needed to move that information from the robot’s arm to the operator—and allow the astronaut to react to it—is very complex.

In tests last summer, operators using the two Robonaut prototypes at JSC were asked to hold a soccer ball at arm’s length between both hands and move it in a circle in front of their chests. Even this very simple act created serious problems for the robot’s control system. “They were dropping the ball—literally—more often than not,” says O’Malley. The problem turned out to be a slight but significant delay in the time it was taking to transfer information between the robot’s arms and the operator.

“They would push with both arms, and they wouldn’t feel anything, so they would push some more, just to make sure they had a tight grip on the ball,” said O’Malley. “Then, the original signal would finally get to them, and they would feel the pressure. They would respond by relaxing, but they wouldn’t feel that right away. Instead, they would feel the increased pressure they had applied earlier, so they would relax even more, and then the whole cycle would start over again.” O’Malley and her colleagues eventually were able to solve the problem by inserting some additional programming that compensated for the delay.

Niedzielski’s work also is critical for the control of the robot. She is part of a team that is creating a voice-recognition system that the operator will use for added control of Robonaut. “If your hand movements are being transmitted directly to the robot’s hands, it’s not like you can reach over and touch a button on a control panel,” Niedzielski says. “We’d like to give the astronaut the ability to do things like freeze one arm after they get it positioned just right.”

Niedzielski’s team hopes to design a voice-recognition system that is capable of operating both on the ground and in space and thus is sensitive to changes in vocal quality that result from these very different conditions.

Human listeners adjust to these changes effortlessly, but scientists don’t yet fully understand how the human brain interprets language, so they’re hard-pressed to teach a computer to do it. “So much of the meaning we attach to words comes from context,” says Niedzielski, “and it’s very difficult to teach a computer to rely on context.”

Moreover, the system must be flexible enough to compensate for the physiological changes that astronauts undergo in orbit. For instance, astronauts’ nasal passages expand in microgravity, and as a result, the tone of their speech changes. Niedzielski says the voice-recognition team faces a real challenge in creating a system that can adapt to these kinds of parameters.

If all goes according to NASA’s timeline, Robonaut will make its initial flight in about five years.

—Jade Boyd