Electrical impulses add weight to robot muscles

A research team has created artificial muscles with the potential to carry 80 times their own weight and extend to five times their original length when carrying a load.

The team from the National University of Singapore’s (NUS) Faculty of Engineering believe their invention will pave the way for the construction of life-like robots with extraordinary strength. In addition, these novel artificial muscles could potentially convert and store energy, which could help the robots power themselves after a short period of charging.

Led by Dr Adrian Koh from NUS’ Engineering Science Programme and Department of Civil and Environmental Engineering, the four-member team has been working on the project since July 2012.

Robots are restricted by their muscles which are able to lift loads only half its own weight – roughly equivalent to an average human’s strength. Artificial muscles have been known to extend to only three times its original length when similarly stressed. The muscle’s degree of extendibility is a significant factor contributing to the muscle’s efficiency as it means that it could perform a wider range of operations while carrying heavy loads.

In a statement, Dr Koh said, ‘Our materials mimic those of the human muscle, responding quickly to electrical impulses, instead of slowly for mechanisms driven by hydraulics. Robots move in a jerky manner because of this mechanism. Now, imagine artificial muscles which are pliable, extendable and react in a fraction of a second like those of a human. Robots equipped with such muscles will be able to function in a more human-like manner – and outperform humans in strength.’

In order to achieve this, Dr Koh and his team have used polymers which could be stretched over 10 times their original length.

A good understanding of the fundamentals was largely the cause of their success, Dr Koh said.

‘Last year, we calculated theoretically that polymer muscles driven by electrical impulse could potentially have a strain displacement of 1,000 per cent, lifting a load of up to 500 times its own weight. So I asked my students to strive towards this…no matter how impossible it sounded,’ he said.

Though they could only achieve a modicum of their target, it is a first in robotics.

‘Our novel muscles are not just strong and responsive. Their movements produce a by-product: energy. As the muscles contract and expand, they are capable of converting mechanical energy into electrical energy. Due to the nature of this material, it is capable of packing a large amount of energy in a small package. We calculated that if one were to build an electrical generator from these soft materials, a 10kg system is capable of producing the same amount of energy of a 1-ton electrical turbine,’ Dr Koh said.

This means that the energy generated may lead to the robot being self-powered after a short period of charging, which is expected to be less than a minute.