Micro-force measuring apparatus for robotic fish: Design, implementation and application

Robotic fish are widely studied for their high propulsive efficiency, maneuverability, speed, acceleration and stealth. Compared to the measurement of the speed and acceleration of robotic fish, the propulsion can hardly be detected because of the micro-force and the movement. In this paper, we designed a micro-force measuring apparatus consisting of a micro-force sensor and a fixing device for robotic fish. The sensor has an accuracy of 0.1mN and can transform the force to electronic signal which is convenience to measure. The designed fixing device can limit the lateral movements of robotic fish but have non drag force in the forward swimming direction. Through this apparatus we first measured different propelling models and then compared the propulsion of robotic fish with different shape and stiffness of caudal fins. Robotic fish designed with soft caudal fin can generate maximum propulsion when undulation in the carangiform model.