GTSR - Georgia Tech Systems Research Lab

 

Office of Naval Research, National Science Foundation, U.S. Naval Research Laboratory

 

Underwater Glider Navigation

In collaboration with Dr. Catherine Edwards at Skidaway Institute of Oceanography, we develop methods for efficient navigation of underwater gliders, which are low-speed robust sensor platforms suitable for long-duration ocean sampling deployments. We have developed a method for real-time guidance of gliders using predictive ocean models, and our methods have been tested in field deployments in 2012 and 2013 off the coast of Long Bay, South Carolina—a region with strong tidal and Gulf Stream currents.

Underwater Glider
Long Bay glider deployment

Long Bay glider deployment Techniques like Controlled Lagrangian Particle Tracking (CLPT) have been developed to quantify the effects of error in ocean models on a path planned for a glider. Large errors in the model flow can invalidate path planning efforts. In the simulation below, different regions of the flow have a different background color. Each color shows a finite-time Lyapunov exponent, which quantifies the amount of “stretching” between particles freely advected by the flow.

Controlled Lagrangian particle tracking simulation

Our contribution to the efficient navigation of gliders continued in Gliderpalooza 2013, a collaborative ocean-survey experiment. Data collected from the experiments will create a coastal continental scale data set supporting goals like improved hurricane forecasts.

Autonomous Oil Sampling Survey

A year after the Deepwater Horizon oil spill, we carried out collaborative autonomous oil sampling, and depth mapping experiments in a coastal lagoon in Grand Isle, Louisiana.

Depth map created using data collected by a survey vehicle during multiple missions over several weeks
Satellite image of the lagoon that was the site of the survey

Student-Developed Robots

Central to our environmental sensing efforts were two student-built robot platforms, autonomous surface vehicle (ASV) Victoria and remotely operated vehicle (ROV) Beta, developed and built by an interdisciplinary team of graduate and undergraduate students over a period of several years.

ROV Beta
Closeup ASV Victoria's systems
ASV Victoria in action

 

Glider CT (Computerized Tomography) Experiments

This work focuses on developing approximated methods for modeling and estimating ocean currents to guide autonomous underwater gliders more effectively. Glider CT can be viewed as analogous to CT scanning in medical imagery, where instead of reconstructing a cross-sectional image from X-rays passing through varying density tissue in the body, we produce a map of ocean currents from underwater gliders passing through varying current flows. For the experimental setup, we navigate Khepera III robots in a simulated flow field created by a light source, where light intensity measured by each robot corresponds to horizontal flow velocity. After collecting navigation data from the Khepera III robots, we reconstruct the simulated flow field from the trajectories of the robots by running the Glider CT algorithm.

Khepera III robots drive across a light field in a lab experiment validating the Glider CT algorithm

Undergraduate Student Researchers

Our group is actively involved with Georgia Tech’s Vertically Integrated Program (VIP), which connects undergraduate students with ongoing research projects in a team-based environment. Through this program we are able to develop reliable and imaginative robotic platforms that support our existing research, inspire the student teams through hands-on experience, and even supply some new ideas for the future of our program.

Undergraduate student Phillip Cheng tests the custom wireless control system he designed for a helium blimp