Bio-inspired Robotic Fish with Multiple Fins

In order to improve the performance of AUVs in terms of efficiency and maneuverability, researchers have proposed biomimetic propulsion systems that swim using flapping fins rather than rotary propellers. This calls for the exploration of unique locomotion characteristics found in a variety of fish for use in underwater robots. (Sfakiotakis et. al., 1999) present a good review of fish swimming modes targeted at roboticists interested in aquatic locomotion. A classification scheme of fish locomotion mechanisms, originally presented in (Lindsey, 2006) and was modified in (Colgate & Lynch, 2004), is shown in Fig. 1. The three main swimming styles are characterized by undulatory body motion, undulatory fin motion, and oscillatory fin motion. A more traditional classification is one proposed by Breder (Breder, 1926) that broadly identifies two styles of swimming: one is Body and/or Caudal Fin (BCF) locomotion, and the other is Median and/or Paired Fin (BMP) locomotion. Fish classes that use varying degrees of body undulation and/or caudal fin oscillations for thrust generation are examples of BCF swimming, and fish that use paired fins like the left and right pectoral fins, dorsal, and ventral pelvic fins for thrust generation are classified under the MPF swimming style.