Fish Swarm: Hydrodynamic Interactions of Robotic Fishes

Fish Swarm
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Fish Swarm
One of the areas that have attracted scientists’ interests in the field of engineering, physics, and biology is how robotic fish move in groups. The potential advantage of swimming together in well-coordinated schools is to enable fish to extract energy from their neighbors’ vortices to reduce their locomotion costs [1]. When engineers are making robotic fish, they emphasize how swimming together can save energy. Fish swarm has algorithms that allow them to swim in groups, and experiments have revealed that group swimming makes robotic fish stable underwater. However, one of the primary challenges that engineers encounter is the lack of an effective bottom-level control system for robotic fish. The paper focuses on how fish swarm work, the technique used to control fish auto swim in a group, and Fumin Zhang’s fish swarm and the technique used to control them. Additionally, it determines whether any group succeeded or failed in using ultrasonic or sonar to locate other fish, the techniques used underwater for locating, and their advantages and disadvantages.
How Fish Swarm Work
Engineers are working hard to promote the robustness and diversity of locomotive strategies of robotic fish in fluid environments. Biologists believe that fish swarm uses the Central Pattern Generator (CPG) to generate rhythmic outputs that control their locomotion [2]. In that light, robotic fish have CPG controllers with feedback, reinforcement learning, and proprioceptive sensing. The CPG controller helps the robotic fish to adjust their bodies’ undulation when they receive feedback from proprioceptive sensors, which are decoded through reinforcement learning. In addition, schooling fish dynamically optimize body undulations so that they can save energy and improve their swimming efficiency without taking into account their spatial formations [3]. Lateral line and vision are the two primary sensory modalities that fish swarm use to gather environmental information so that they can make effective movement decisions. However, researchers identified that fish swarms can still react to nearby flows even when their vision systems and lateral line are impaired. Fish use proprioception sensors to know the local flow dynamics and adjust to kinematics appropriately. Besides, proprioception means muscle force and self-motion sensing.
Technique Used to Control Fish Auto Swim in Group
Neural networks and hydrodynamic interactions are used to control fish auto swim in groups. Robotic fish swim side-by-side, which makes them generate rhythmic signals that facilitate swimming efficiency in groups [1]. A robotic fish has a camera, motor, and battery. The motor propels the fish, creating a side-by-side motion. An acoustic communication system resembles the CPG controller, and it helps fish change their swimming speed and control their buoyancy. The diagram below shows how hydrodynamic interactions control fish auto swim in a group [3].
Figure 1
How Hydrodynamic Interactions Control Fish Auto Swim in a Group


Source: https://iopscience.iop.org/article/10.1088/1748-3190/ac165e/pdf
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