The Centaur 4x4 wheeled vehicle combines a camera head on a neck system, a pair of highly advanced arms designed for remote force-feedback operation and a number of proximity and location sensors, including an arm laser to indicate depth close-up.
Mogensen used a force-feedback control system developed at ESA, letting him feel for himself whenever the rover’s flexible arm met resistance.
These tactile sensations were essential for the success of the experiment, which involved placing a metal peg into a round hole in a ‘task board’ that offered less than a sixth of a millimetre of clearance. The peg needed to be inserted 4cm to make an electrical connection.
“We are very happy with today’s results,” said André Schiele, leading the experiment and ESA’s Telerobotics and Haptics Laboratory. “Andreas managed two complete drive, approach, park and peg-in-hole insertions, demonstrating precision force-feedback from orbit for the very first time in the history of spaceflight.”
The real challenge was achieving meaningful force feedback despite the 144,000km round trip the signals had to travel: from the Station, moving around Earth at 8km/s, up to satellites almost 36,000km high and then down to a US ground station in New Mexico, via NASA Houston and then through a transatlantic cable to ESTEC – and back.
The inevitable time delay approaches 1s in length, but the team used sophisticated software based on a dedicated control method termed ‘model mediated control’ to help compensate for this lag, incorporating sophisticated models to prevent the operator and arm from going out of sync.
Remote-control rovers are useful in dangerous or inaccessible environments, not only in space. On Earth, they can work in Arctic conditions, the deep sea or at nuclear disaster sites.
The Interact experiment is a first step towards developing robots that provide their operators with much wider sensory input than currently available.
In future, similar systems could be used for ground-based operators to oversee dexterous robotic tasks in orbit – such as removing debris around Earth – or even to build a base on the Moon. Or astronauts could steer rovers across the Martian surface while safely in orbit around Mars.
