China is working on an exoskeleton suit for astronauts that has smart sensors to help with strength and mobility, according to space engineers involved in the project.

A team from the Beijing Machine and Equipment Institute - China's version of Nasa's Jet Propulsion Laboratory - said the smart sensors could predict movements by monitoring electrical signals in a person's muscles.

The accuracy of these predictions was more than 90 per cent, higher than that of a similar exoskeleton for astronauts developed by Nasa a decade ago.

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Led by senior engineer Hu Yuanyuan, the team reported their progress on the exoskeleton in Chinese peer-reviewed journal Manned Spaceflight in June.

In the paper, they said the smart sensors would allow the exoskeleton system to respond to the intentions of the user "within 0.1 second - good enough to meet the practical needs of astronauts by providing force assistance precisely on demand".

Traditional spacesuits have high joint resistance that restricts movement. Exoskeletons can improve the situation but the sensors they use do not usually work in the low-gravity conditions of space, the team said.

Nasa's X1 robotic exoskeleton uses a joint encoder as a sensor for motion intention, which "has apparent response lags that harmed user experience", according to Hu.

The timing of assistance when using an exoskeleton is important for how useful it is because a delay could have the opposite effect and add more burden on the joints.

But getting that right is not easy - the ankle joint, for example, only has concentrated power mid-cycle in a single step, and the exoskeleton has to kick in at precisely that moment to provide assistance.

To do this, Hu and the team developed a system to monitor electromyogram signals, or the electrical activity of muscles during movement. Those signals occur before joint movement and can indicate motion intention.

The system uses an algorithm to measure the signals and accurately predict the starting point of motion intention. It has flexible sensors - a 4x4 electrode array - that fit more closely to the body than flat electrodes.

Put to the test at low gravity, the system achieved unprecedented accuracy of 94.2 per cent in estimating motion intention and actual movement - suggesting it could provide almost real-time feedback, according to the team.

"The results show that this method could support man-machine cooperative control," Hu said in the paper.

In an earlier paper published in April, the team said the exoskeleton had improved the efficiency of motor function during testing and it could also work for longer after the system's algorithm was refined.

"Wearer comfort and the integration of the [sensor] system with the exoskeleton will remain our research goal," Hu said in the June paper.

Three Chinese astronauts are currently on a six-month mission on the country's new Tiangong space station to complete the assembly work. It is part of a space programme that includes plans for astronauts to work on a moon base, collect lunar samples and carry out space telescope maintenance - tasks that could be helped by the use of exoskeletons.

Early this month, Nasa administrator Bill Nelson told German newspaper Bild that Chinese astronauts were learning how to destroy other countries' satellites, a claim Beijing has denied.

This article originally appeared in the South China Morning Post (SCMP), the most authoritative voice reporting on China and Asia for more than a century. For more SCMP stories, please explore the SCMP app or visit the SCMP's Facebook and Twitter pages. Copyright © 2022 South China Morning Post Publishers Ltd. All rights reserved.

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