Abstract
Since the propulsion mechanism in fluid using elastic fins like caudal fin and pectoral fin of fish is effective, many studies of elastic fin for propulsion in water and development of fish robot using elastic fin were carried out. However, the optimum elasticity of fin is not constant and changed by the movement task and environment, such as swimming speed. It is very difficult to exchange fins of different bending stiffness while moving. Thus, we aimed to develop real-time variable-stiffness fins. As the one of the variable-stiffness-fins, we have developed a fin with variable-effective-length spring. The apparent stiffness of the fin can be changed dynamically. The apparent stiffness of the fin can be changed by effective-length of the spring. This paper describes optimum effective-length of spring for thrust efficiency in uniform flow
