Design of the Multi-Robot Coherent Structure Testbed (mCoSTe) for Distributed Tracking of Geophysical Fluid Dynamics

We present the design and validation of the multi-robot coherent structure testbed (mCoSTe). The mCoSTe is an experimental testbed that is used to evaluate the performance of manifold and coherent structure tracking strategies by a team of autonomous surface vehicles in two-dimensional flows. It consists of a fleet of micro-autonomous surface vehicles (mASVs) equipped with onboard flow sensors and three experimental flow tanks: a Low Reynolds number (LoRe) Tank, a High Reynolds number (HiRe) Tank, and a Multi-Robot (MR) Tank. Each of the flow tanks are capable of producing controllable ocean-like flows in a laboratory setting. Flows in the HiRe and MR tanks are generated using a grid of independently controlled vortex driving cylinders. We show how the HiRe tank is capable of producing repeatable and controllable coherent structures in 2D by analyzing the surface flows using a a combination of Finite-Time Lyapunov Exponents (FTLE) and Dynamic Mode Decomposition (DMD). Using these results, a scaled flow is replicated in the MR Tank for experimental validation of robotic tracking strategies. Building upon our existing work, robotic tracking of manifolds and coherent structures in 2D flows is achieved through local sampling of the flow field using each vehicles onboard flow sensors. We describe the design and development of the mASVs and the onboard flow sensor and present experimental results to show the validity of our designs.