The objective of this research is the creation of a coastal observing system that enables dense, in situ, 4D sensing through networked, sensor-equipped underwater drifters. The approach is to develop the technologies required to deploy a swarm of autonomous buoyancy controlled drifters, which are vehicles that can control their depth, but are otherwise carried entirely by the ocean currents. Such Lagrangian sampling promises to deliver a wealth of new data, ranging from applications in physical oceanography (mapping 3D currents), biology (observing the dispersion of larvae and nutrients), environmental science (tracking coastal pollutants and effluents from storm drains), and security (monitoring harbors and ports).
This observing system fundamentally requires accurate positions of the drifters (to interpret the spatial correlations of data samples), swarm control algorithms (to achieve desired sampling topologies), and wireless communication (to coordinate between the individual drifters). This research will create distributed techniques to self-localize the drifter swarm, novel swarm control algorithms that enable topology manipulation while purely leveraging the stratified flow environment, and efficient wireless underwater communication for information sharing.
This project has significant societal impact and educational elements. Underwater drifter swarms will enable novel insights into a wide array of scientific questions, including understanding plankton transport, accumulation and dispersion as well as monitoring harmful algal blooms. Undergraduates will play an active role in many aspects of this project, thereby offering them a uniquely interdisciplinary experience. Finally, outreach to high school students will occur through the UCSD COSMOS summer program.
The goals of the project are to develop the cyber technology needed to create a novel kind of underwater sensing technology, where a large number of autonomous underwater vehicles organize themselves as a swarm, thereby forming a dense four-dimensional spatio-temporal sampling system. The unique strength of the system is that it consists of Lagrangian drifters that float with the coastal currents that are networked together using underwater communications. The cyber innovations include networking protocols, distributed position finding algorithms, and under-actuated control algorithms. The overall outcome of the project, in addition to the development of a number of algorithms was the successful deployment of 17 miniature vehicles adjacent to the La Jolla coast during October 2013. The data was analyzed over the last year and we discovered many interesting oceanographic features related to the spatial dynamics of ocean circulation on sub-kilometer and sub-daily scales. For one, we observed the swarm to "breath", in that the vehicles alternately coalesced and then spread out. For another, we observed no net transport of the vehicles motion that would be associated with various modes of sub surface propagation. Finally, the propagation of internal, or density waves is of great interest to oceanographers. Our spatial and temporal resolution was adequate to observe them via the measurement of temperature fluctuations through the swarm. Our system was largely a success and we hope to export this technology to the larger oceanograhic community in creating a next generation of less expensive, more informative, ocean vehicles. This is very important as the health of the planet is inextricably related to that of the oceans.
