ESA research works to overcome feedback delays in Analog-1 testingLeigh Mc Gowranon April 21, 2022 at 10:06 Silicon RepublicSilicon Republic

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Research at the European Space Agency (ESA) continues to explore the potential for astronauts to work from spacecraft in orbit while controlling robots to perform on-ground studies.

A new study published yesterday (20 April) in the journal ScienceRobotics details how the ESA’s Analog-1 experiments overcame a two-way signal delay between the rover robot on Earth and its controller on the ISS.

The Analog-1 mission was a culmination of 11 experiments conducted over a decade by the ESA under the Multi-Purpose End-To-End Robotic Operation Network (METERON) project to test ways of interacting with robots from afar.

The biggest success occurred in 2019 when astronaut Luca Parmitano obtained direct haptic feedback from an Earth-based robot that had an advanced gripper with the equivalent mobility of a human hand.

“This is the first time that an astronaut in space managed to control a robotic system on the ground in such an immersive, intuitive manner,” Aaron Pereira of the German Aerospace Center DLR said.

Pereira said the control interface incorporates force feedback so the astronaut can experience what the rover feels.

“What this does is help compensate for any limitations of bandwidth, poor lighting or signal delay to give a real sense of immersion – meaning the astronaut feels as though they are there at the scene,” Pereira added.

Adding ‘passivity’ to force feedback

The research team said they had to overcome issues with the delay in force feedback received by the operator, which meant the operator could continue moving the robot even if it was stuck on a rock.

“This could lead to the robot going out of sync with its controller, potentially vibrating like crazy, perhaps even damaging itself,” Pereira said.

To prevent this, the research team used a concept called ‘passivity’, by looking at the amount of energy the operator puts in and ensuring the robot never gives out more energy than what it receives.

“So for instance, when the robot arm is moving and suddenly hits a rock it would take extra energy to move which the astronaut did not command, so we reduce the command energy at once to slow down the arm,” Pereira said.

“Then, after the 850 microsecond delay, when the astronaut feels the rock they can then choose to add the extra energy to push it.”

The research team said the biggest limitation of their experiments to date is that the indoor lunar testing environments lack realism. To improve on this, the next phase of Analog-1 testing will take place on the volcanic slopes of Mount Etna in Italy this Summer.

In 2020, China’s Chang’e 5 mission became the first to bring back rocks from the moon since 1976 – making it the third country to achieve the feat. The rocks and lunar samples were collected by a lander craft using a robotic arm and deposited in an ascender craft.

While many missions have taken robots to the moon and other planetary surfaces in the last five decades, with more on the way, the dexterity and control seen in the Analog-1 test could help astronauts undertake more complex missions in future.

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