The Efficiency of Spine Stiffness in regards to Anguilliform Locomotion

Fish come in varying shapes, sizes, and ecosystems that lead to a multitude of different modes of swimming. To categorizes these different methods, fish are separated by fin and body motion. In particular the order of fish Anguilliformes or ‘eel-like’ locomotion utilizes a large portion of their body to produce thrust while swimming known as undulatory locomotion [1]. Due to the developments of high-speed video capture, research with in the past two decades have been able to understand eel locomotion, kinematics, and hydrodynamics. These results have given us more accurate models for Anguilliformes and data about the efficiency, stiffness, and kinematics of their swimming behaviors.

As a result of the improved analysis of eels, robots that emulate their swim patterns have become increasingly more prevalent. In order to mimic this motion, these robots have used a variety of complex actuators or system of actuators such as pneumatic muscles, origami, and chains of servo motors to accomplish this behavior [2], [3], [4]. However, the proposed method of actuating a flexible spine to generate this undulation would be a much simpler mechanism. From the research being done on this mode of swimming, body stiffness of the eel is an important factor in the success of undulatory locomotion [5]. Therefore, it is reasonable to assume that stiffness will have an effect on the efficiency and speed of the proposed method. For the purpose of this project, I would like to specifically focus on studying how the spine stiffness is a factor in the efficiency of a passively actuated spine. The objective of this project would be to learn more about the correlation between spine stiffness and speed and its relation to the efficiency of the system. Additionally, this research is being done with the hope that this study could provide information for when applying this mechanism in a future project.