Design and Validation of a Robotic Control Law for Observation of Deep-Ocean Jellyfish

Abstract

Limits on the technology available to marine scientists to study jellyfish in situ motivate the development of an automated robotic tracking system for deployment in the deep ocean. This paper synthesizes a control strategy for robotic jellyfish tracking with a remotely operated vehicle (ROV). The control strategy employs three feedback loops tailored to the jelly-tracking task. A primary loop provides moderate proportional-derivative feedback to track animal swimming motion without producing excessive hydrodynamic disturbances, which might impact the behavior of the animal under study. A second boundary-control loop provides aggressive thrust, in a direction away from the target and only when needed to prevent loss of the target outside the boundaries of the vision sensor. A third disturbance-accommodation loop counters low-frequency bias forces without fighting commands issued by the human pilot. The complete system was implemented and tested in the Monterey Bay using the Monterey Bay Aquarium Research Institute's ROV Ventana. The control system autonomously tracked six animals for durations longer than 15 min, including a Plychogena medusa which was tracked for 89 min