Abstract:

Swimming fish has unparalleled swimming performance, both in terms of speed and agility. A fish can accelerate from standstill to its max speed in less than a second and can change its trajectory equally fast. In performing fast turns, a fish will recruit its entire body using the same muscles that propel it forward. The key to this swimming prowess lies in its tail: its strong antagonistic muscles provide both forward thrust and a change in direction. A design for a fast swimming robotic fish is proposed with 2 control surfaces, with a novel underactuated control method for the yaw direction which is governed solely by the tail. However, complex fluid dynamics at high swimming speeds poses control challenges for the robotic fish as the interaction with the environment is chaotic and turbulent. A PID control system based on local sensors is proposed that can provide pitch, roll, and yaw information for attitude control by filtering out the internal dynamics caused by the undulatory swimming and turbulent flows. This is a first attempt at the control of an untethered fast swimming robotic fish in the world at speeds of 2.4m/s.