Electrical impulses add weight to robot muscles

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.