RoboTwin: a platform to study hydrodynamic interactions in fish schools

Liang Li, PhD
Project Leader (PI)
University of Konstanz, Germany
Research interests
Collective Behavior, Bio-Inspired Robotics, Hydrodynamic Interactions, Agent-Based Modeling

By living and moving in groups, fish gain many benefits, such as heightened predator detection, greater hunting efficiency, more accurate environmental sensing, and energy saving. Although the benefits of hydrodynamic interactions in schooling fish have drawn growing interest in fields such as biology, physics, and engineering, and multiple hypotheses for how such benefits may arise have been proposed, it is still largely unknown which mechanisms fish employ to obtain hydrodynamic benefits, such as in increased thrust, or improved movement efficiency. One main bottleneck has been the difficulty in collecting detailed sensory information, corresponding locomotory responses and hydrodynamic information from real schooling fish. In this paper, we present the RoboTwin platform designed to aid such data collection: it allows us to replay the 3D movements and body posture kinematics of real fish in fish-like robots, allowing us to measure power cost, thrust, and detailed flow fields. To demonstrate the capabilities of our platform, we conduct experiments with two goldfish (Carassius auratus) swimming in a flow tank, from which 3D positions and corresponded body postures are quantified. By replaying these in RoboTwin we reveal large benefits in thrust (around 50% compared to swimming alone) obtained by the follower exploiting vortices shed by the leader. Our results show the effectiveness of our design. We outline future applications of this system for the study of hydrodynamic interactions in schooling fish.

Liang Li is a Project Leader (PI) at the University of Konstanz and the Max-Planck Institute of Animal Behavior. He received a bachelor’s degree in automation from Chongqing University in 2011 and a PhD in general mechanics and foundation of mechanics from Peking University in 2017. From February 2017 to June 2021, he was a Postdoctoral Research Fellow in the Department of Collective Behaviour, Max Planck Institute of Animal Behavior, Konstanz, Germany. His research interests include bio-inspired robots, swarm robots, collective behaviour in hybrid animal-robot systems, and bio-fluid dynamics in fish schools. He has published interdisciplinary studies in more than 37 peer-reviewed journals, including Nature Communications and PNAS. He also serves as a reviewer for these journals. He was awarded the distinction of outstanding graduate of Peking University and Beijing and has received several grants to pursue research on developing and using robots in studying biological questions.