From mechanical manta rays to giant robo jellyfish, the marine world is well represented in the field of robotics. While many autonomous underwater vehicles (AUVs) take advantage of energy-efficient gliding or pulsing motions, a team of scientists at the National University of Singapore’s Department of Electrical and Computer Engineering have invented two robots that mimic the movements of a carp. The machine is capable of diving, floating, and using its fins like a real fish, and it can be maneuvered into spaces that are difficult for many AUVs to access.
For three months, professors Xu Jianxin, Fan Lupeng, and Dr Ren Qinyuan studied how carp move underwater. With no preexisting mathematical models to assist them, they began their observations from scratch. They used a camera to capture the fish’s locomotion, and then they converted the data into equations that could help imitate muscle function via actuators.
“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.
The body, control box, and motor are all waterproofed, and the fins and tails are composed of thin acrylic board. Plastic foam pieces on each side control the balance and buoyancy of the body, and an internal ballast system allows the carp to change density in order to dive. The system is tuned to let the fish descend suddenly and to a precise depth. The team built two prototypes, with the larger measuring 1.5 meters and 10 kg and the smaller measuring 60 cm and 1.5 kg. The bigger carp can reach depths of 1.8 meters, and the team has plans to further increase its range. They also hope to reduce the overall size of their robots while adding sensors, cameras, and GPS units. The researchers believe their robo fish can be used for detecting pipeline leaks, military surveillance, and the installation of communication cables.
Images by National University of Singapore