Swimming performance of robotically controlled jellyfish in three dimensional trajectories

Robotically controlled jellyfish, or biohybrid jellyfish, have demonstrated potential both as energy efficient ocean profilers and as tools to study the fluid dynamics of jellyfish swimming. Previous work has been limited to vertically oriented, unidirectional swimming, without investigations into horizontal swimming or turning maneuvers. Here we explore the hydrodynamics of biohybrid jellyfish turning and consider how jellyfish wake interactions with the payload influence stability. To conduct these experiments robotic augmentation was expanded to achieve 4 degrees of freedom, including translation along three axes and rotation around one axis. The biohybrid jellyfish were tracked in three dimensions as they performed swimming maneuvers in a 1.8 by 1.8 by 4.9 meter test tank. Horizonal and vertical swimming speeds were evaluated with the payload positioned forward and aft of the jellyfish. Deviation from the commanded trajectories during straight line swimming and turning was also quantified for both these configurations. These experiments enabled the differences in hydrodynamic drag and stability between payload configurations to be evaluated. The unsteady wake interactions of the payload and the jellyfish were also explored.