Researchers at the Tallinn University of Technology, in collaboration with partners across Europe, have created, within the framework of the EU research project FILOSE, a robotic fish inspired by real fish, which has a sensitive artificial lateral line similar to the sensory organs of real fish.
The artificial lateral line allows the robot to use its body to sense changes in the flow and pressure of fluids, and to enhance its swimming efficiency by reacting to them. With its sensitive lateral line, the fish robot will help to study the fish passage facilities at hydroelectric plants, rapids, spawning areas, and other aquatic environments . In the future, it can be used to ensure, for instance, that migratory fish have access to spawning areas, but it has its applications in other areas as well.
The robotic fish uses the flow of water to its advantage
“In robotics, currents have so far been regarded as distractions that divert robots away from their planned course,” says Prof. Maarja Kruusmaa, Co-ordinator of the FILOSE project. “We have shown that currents are also a source of information that facilitates a better control of a vehicle. Additionally, currents can be used as a source of energy if we are able to understand the flow dynamics and interact with eddies and streams in a clever way.”
Experiments with flow sensing and actuation in the experimental pool at the Centre for Biorobotics and other laboratories revealed that the fish robot can save energy by finding energetically favourable regions in the flow. With respect to the objective, the environments that are more favourable are those where the currents are weaker, or where the fish can use the energy of eddies to its advantage. These robots can also determine the direction of the flow, as well as swim against it or remain stationary in a current, compensating for downstream movement by measuring flow velocity. It has been demonstrated experimentally that a FILOSE robot, hovering in the wake of an object in the flow, reduces its energy consumption. “It is similar to reducing your effort in the tailwind of other cyclists, or reducing the fuel consumption of your car by driving behind a truck,” claims Prof. Kruusmaa.
Helps to create energy-efficient underwater robots
The knowledge gained from the use of robotic fish will make it possible to create superior underwater vehicles, the fish-like movement of which would provide an alternative to the inefficient devices currently in use. In the future, robotic fish are also expected to be implemented in demining operations, monitoring environmental pollution, and rescue operations.
The fish with a sensitive lateral line was created after four years of extensive research, which helped to understand the movement of fish and the sensory ability of the lateral line. As a result, based on how fish detect and exploit properties of flowing water, it will become possible to develop energy-efficient underwater robots that function on the basis of biological principles.
The design of the lateral line is currently developed and used within the framework of the FishView project of the BONUS programme in order to explore the characteristics of fish passage facilities at hydroelectric plants, with the aim of providing an explanation of how fish perceive the existing passages. With the outcome of this project, the scientists seek to explain why some fish passage facilities fulfil their intended function while some do not.