A Biomimetic Robot Modeled on the Shrimpfish, Aeoliscus strigatus

Shrimpfish, Aeoliscus strigatus, inhabit the Indo-Pacific coral reefs in coastal waters. They assume a vertical posture, with their head facing downwards, which augments their ability to quickly maneuver. Their unique posture and impressive maneuverability are possible by careful actuation of the pectoral fin pair. Observations show that the pectoral fins constantly oscillate while hovering, turning and swimming vertically or horizontally. The dorsal, caudal, and anal fins are also unusually placed in a cluster on the posterior-ventral side of the fish. The combination of the pectoral fin and the median fin motions are of high interest to develop a biomimetic robot that can match the maneuverability of the shrimpfish.It is important to know and understand the location and effect of the center of gravity and center of buoyancy. These parameters are based on the weight and volume of the shrimpfish and have a large effect on the hydrostatic stability and maneuverability of the fish. Many fish are inherently unstable, and must continuously overcome numerous perturbations from their environment to maintain their position in the water column to prevent the tendency to roll belly-up. Their dynamic response is often successfully accomplished by left and right pectoral fin oscillation which creates stabilizing forces. The static stability of the shrimpfish is currently under investigation. Once known then the positions of the center of gravity and center of buoyancy can be adjusted in the robot to match that of the real fish.A biomimetic robot displaying the basic characteristics of the pectoral fins of the shrimpfish has been built and tested. By controlling the motion of the pectoral fins with RC servo motors through a microprocessor, programming can be adapted to match the fin kinematics of the shrimpfish. The robot has demonstrated forward propulsion, backward propulsion, as well as turns of varying radii’s. The system will be further modified to incorporate relevant shrimpfish fluid mechanical characteristics the positions of the centers of gravity and buoyancy as mentioned above. We will then experiment with robot’s fin kinematics to better understand how the actions of the pectoral fins generate the forces necessary for stabilization in both the robot and the real shrimpfish. Such experiments would be difficult to impossible to perform on the slender and delicate shrimpfish. The biomimetic robot makes these experiments possible and shows the power of the biomimetic approach to understanding the bio-fluidmechanics of aquatic organisms