Modeling Biomorphic Robotic Fish Swimming: Simulations and Experiments

We present a fish robot implementing a thunniform type of movement in aquatic medium. The shape of the robotic fish body was copied from tuna fish using 3D model constructed from a photograph. The robot is equipped with a flexible tail whose oscillations provide translational motion in a water pool. We designed a control system imitating a simple CPG (central pattern generator), propulsion system implementing a simple form of muscle contraction activity and build experimental setup to monitor functional characteristics of the robot movement. We analyze how these characteristics including motion speed and energy consumption depend on the parameters of the oscillating tail, e.g. shape of the tail, frequency and amplitude of the oscillations. The fish robot demonstrated rather effective performance and can be further optimized. We also developed a simulation model of the fish swimming. The model includes exact copy of the geometry of the robotic fish body comprising rigid compartments and oscillating tail. Virtual robot movement in the water medium is modeled by numerical solutions of hydrodynamic and robot body biomechanics equations. In numerical experiments we calculated kinematic parameters of fish movement and visualized hydrodynamic flows at different stages of movement. Detailed simulation showed good qualitative agreement with experimental swimming in real water environment.