Study of Energy Efficiency of Thunniform Locomotion Using a Robotic Fish Example

Abstract

Abstract. The development of biomorphic underwater robots that utilize locomotion principles of aquatic organisms is one of the actively advancing areas of modern robotics. Of particular interest is the design of robots implementing thunniform locomotion, characteristic of highly efficient swimmers.

This paper presents a fish-like robot whose design is based on the morphology of the yellowfin tuna and optimized for experimental studies of swimming kinematics under laboratory conditions. The robot is equipped with a caudal propulsion system that generates forward motion through periodic oscillations of the tail fin, mimicking the natural swimming kinematics of fish.

The article describes the structural features of the robot, its internal layout, sensors, and principles of maneuvering in three-dimensional space. Experimental studies of swimming kinematics were conducted in a pool using video recording followed by computer vision data processing. Based on marker coordinates on the robot’s body, swimming speed was determined under different operating modes of the tail actuator.

The dependence of swimming speed and energy efficiency on tail beat frequency at constant amplitude was investigated. It was shown that swimming speed increases approximately linearly with increasing frequency. The minimum Cost of Transport (COT) value was 6.22 J·kg⁻¹·m⁻¹, which is comparable to biological prototypes and the most efficient biomorphic robots. The obtained results can be used in the further design of energy-efficient fish-like underwater vehicles.