Analog-1. Image: ESA/A Koehler
The ESA is planning further tests as it tackles feedback delays in its ‘immersive’ Analog-1 rover system.
Research at the European Space Agency (ESA) continues to explore the potential for astronauts to work from spacecraft in orbit while remotely controlling robots to perform on-ground studies on planetary surfaces.
A new study published yesterday (20 April) in the journal Science Robotics details how the ESA overcame feedback delay issues in experiments testing how the Analog-1 rover on Earth could be controlled by someone on the International Space Station (ISS).
The Analog-1 mission was the culmination of experiments conducted over a decade by the ESA under the Multi-Purpose End-To-End Robotic Operation Network project to test ways of interacting with robots from afar.
In 2019, astronaut Luca Parmitano was able to obtain direct haptic feedback from an Earth-based robot that had an advanced gripper with the equivalent mobility of a human hand. From the ISS, Parmitano could remotely pick up and ‘feel’ rock samples from a mock lunar environment that had been set up at an ESA base in the Netherlands.
“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 explained that 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.”
Adding ‘passivity’ to force feedback
In the study published this week, the research team said they had to overcome issues with the delay in force feedback received by the operator, which meant the operator could possibly 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’, looking at the amount of energy the operator puts in and ensuring the robot never gives out more energy than 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, the dexterity and control seen in the Analog-1 tests could help astronauts undertake more complex missions in future.
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