The first robotic fish that moves like a real fish - in 3D

RoboCarp paves the way for future submarines

The first robot fish that moves in 3D could pave the way for better and more efficient autonomous underwater vehicles (AUV) for military and scientific purposes.

Being able to move in all three dimensions is a key skill for swimming and diving. However, existing robotic fish were so far only able to move in two dimensions.

A team of researchers from the National University of Singapore (NUS) has now developed and built a robot fish prototype that can mimic natural movements of a carp – that means the fish can swim up and down the water column as well as change directions horizontally.

The robo-carp is about one and half metres long, weighing about 10kg and it can dive to a depth of 1.8 metres.

“Currently, robot fish capable of 2-D movements are common, meaning that these models are not able to dive into the water. Our model is capable of 3-D movements as it can dive and float, using its fins like a real fish,“ said Professor Xu Jianxin, leader of the project.

The team believes their invention could represent the next step in the development of AUVs. “Compared to traditional AUVs, they are certainly more mobile, with greater manoeuvrability. If used for military purposes, fish robots would definitely be more difficult to detect by the enemy,” said Professor Xu.

The robo-fish developed by the team is essentially an AUV ready for applications. It can serve many tasks that are difficult for human divers and traditional UAVs. For example, it could be programmed to detected leakages in underwater pipes, to explore submerged archaeological sites or sunk ships.

There are many advantages to the fish robots compared to the traditional AUVs – for example, they require less energy and can manoeuvre in very small places. “Some fish can achieve almost 180 degree turning in a small turning radius through bending their body while traditional underwater vehicles have a much larger turning radius. Hence it is quite a feat for us to achieve this movement in our robot fish,” said Dr Ren Qinyuan.

The scientists modelled the movements of the robot after carefully studying the way carps swim. “We chose to study carps because most fish swim like them. There is no literature at all on designing a mathematical model on the locomotion of fish and so we had to start from scratch,” said Fan Lupeng who worked on the project during his final year at the university. “We used a camera to capture all the possible movements of a carp and then converted the data mathematically so that we could transfer the locomotion of real carp to our robot using different actuators.”

In the future, the team would like to construct a smaller and more realistic robo-fish and add some high tech features. The team hopes to make their robot fish even smaller and more realistic. ”We intend to equip it with more sensors like GPS and video camera to improve autonomous 3-D movement. We also intend to test out our fish with more challenging tasks such as object detection,” Fan concluded.

The fish will be featured at the International Conference on Intelligent Robots and Systems, in Tokyo in November this year.

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