Phase controller for a robotic fish to follow an oscillating source

This work develops a method for controlling a robotic fish, as it swims in a school, by following periodic stimuli generated by a neighboring robot. To track the motion of a periodically oscillating neighboring source, the hydrodynamic pressure around the body of the robotic fish is measured by a PVDF sensor attached to the robot. The pressure induced by the source is obtained by subtracting the predicted pressure generated by the robotic fish from the measured pressure. The controlled fish tail mechanism is represented as an oscillator, and a moving oscillating sphere is considered to be an external source. A dipole model based on the potential flow theory is used to predict the hydrodynamic pressure close to the fish tail. The relative phase between the tail and the oscillating source is estimated from the pressure measurements of the PVDF sensor. The difference in phase angle between the tail and the oscillating source is used to determine the torque used to drive the tail mechanism. The proposed method is demonstrated by the tank experiments that involve a captured model of a robotic fish that swims close to an oscillating source.