Using biological spring to improve propulsive efficiency for fishlike robot

This paper proposes a new way for improving the swimming efficiency of fishlike robots. The approach is based on the observation of natural fishes whose muscle tendons play the role of ldquobiological springsrdquo. These springs allow the fish to recover a part of the energy usually lost (by dissipation in the actuators). Mechanically, this energy is produced by the negative work of inertial forces. This principle is here applied to the swim through a spring located between the body and the tail of the robot. More than qualitatively exploring this way, the article proposes a computation of the ldquooptimal valuerdquo of the spring stiffness based on the use of a simple efficiency criterion. The results deduced from this study are physically interpreted, and applied through first simulations, where the propulsive efficiency is improved of 12%.