At the Joint European Torus (JET) in Oxfordshire, scientists have been maintaining the world’s largest nuclear fusion reactor with the help of a robotic system called Mascot
“Mascot is a master/slave telerobotic manipulation system,” said Ronan Kelly, software engineer at RACE (Remote Applications in Challenging Environments).
“That essentially means you have two big arms in a control room, you’ve got two robot arms on the end of a robot inside the torus, and the two correspond directly. So as the operator moves the master arms, he gets full feedback to everything the slave arms are doing.”
Manoeuvres carried out by technicians in the control room are mirrored exactly by the robot in the torus — the doughnut-shaped vacuum chamber where plasma is observed — with haptic feedback allowing for pinpoint precision. Mascot effectively provides surrogate limbs for its controllers, who can’t set foot in the reactor for a number of reasons.
“Even when JET isn’t on, you still wouldn’t want to walk around inside it,” said Kelly.
“It’s complicated, it’s contaminated and it gets activated. So that means there’s lots of very precisely calibrated components in there…it gets contaminated with beryllium dust, which is toxic to humans. And nuclear fusion produces neutrons that activate components – making them radioactive. So you can’t send humans in there even if you want to.”
According to Kelly, Mascot provides incredible dexterity. One of the training exercises for new recruits involves playing Jenga – a popular game of skill where small wooden blocks are removed from a tower and replaced at the top. A steady hand and lightness of touch are required, as anyone who has played can attest.
“It’s good enough to do that, and you also get full-force feedback, which is the really important thing,” Kelly explained. “When you’re performing a task such as replacing a [JET] tile, being able to feel the weight of the tile, being able to know when it’s locked in, being able to get that low-latency force feedback is very important.”
Although the Mascot system has been around for more than half a century, it is regularly updated with new technologies. Previously, cameras were used to provide visual feedback, but views inside the torus are very restricted. Kelly and his team have now augmented the old robotic technology with VR, meaning operators can control Mascot from a first-person view in a
virtual JET environment.
“It’s essentially a live model of the system in virtual reality, updated with the positions of the control systems so the operators know where everything is,” Kelly said.
“The exciting bit is that you can take away the slave robot and just put a simulation in. Then you have a simulated robot for the operators to train on for free. That’s fantastic, because training is one of the biggest overheads in operating a system such as Mascot.”
As well as integrating with VR, RACE is also working on the development of Mascot VI. The upgraded system will feature modular components, with a focus on reliability and availability. When previous iterations of Mascot have failed, it has often been difficult to identify the root cause. Kelly believes the latest model will help address this issue. As a software engineer, he was also keen to embed a digital layer onto the evolving system, which will provide enhanced functionality and greater control over the robot.
“It gives us an opportunity to do some very exciting things,” he said. “You can add virtual force fields, you can constrain movement to a particular joint.”
“Maintaining something such as JET, you often have to essentially do the equivalent of open-heart surgery in terms of the sort of tolerances you need. So being able to constrain to a particular axis, being able to compensate for the weight of an object, that’s all really useful.”