September 2014
Name: Ivan Rodrigues Bertaska
Department: Department of Ocean & Mechanical Engineering
School: Florida Atlantic University
Project:Supervisory Switching Control of an Underactuated/Overactuated Unmanned Surface Vehicle
Research Advisor: Dr. Karl von Ellenrieder
Ivan received his Bachelor of Science in Ocean Engineering from Florida Atlantic University in 2012. While an undergraduate student, he specialized in operating and conducting ocean research with Autonomous Underwater Vehicles (AUVs), and teaching these skills to K-12 students as part of STEM education initiatives. Ivan remained at FAU for his Master of Science in Ocean Engineering degree, which he earned in 2013. His Master’s research included developing autonomy for three different platforms of Unmanned Surface Vehicles (USVs). These vehicles were used for field tests demonstrating self-generated autonomous behaviors. These behaviors included approaching and following targets in an obstacle-laden waterway, as well as COLREGs-compliant multiple vehicle crossings, where a USV followed the “International Regulations for Preventing Collisions at Sea,” avoiding collisions with human-operated vehicles. Most recently, Ivan will be representing one of three teams selected from the United States as part of the RobotX Maritime Challenge – an international robotics competition involving USVs hosted by the Office of Naval Research and the Association of Unmanned Vehicle Systems International.
The Link Foundation is supporting Ivan in his newest endeavor – a supervisory switching controller that transfers control modes between an underactuated mode and overactuated mode for a USV with configurable propulsion characteristics. Typically, most marine vessels feature bow-facing propellers and some sort of rudder system to control yaw motion, leaving the sway direction without any actuation. Thus, these systems are considered underactuated. The vehicle Ivan is working with has the ability to rotate its propellers, a feature commonly found in vessels capable of dynamic positioning. The controller being developed would have the ability to transfer this vehicle between the two states, as each has their advantages and disadvantages. In addition, both controllers are being built around a nonlinear model of the vehicle. Linear controllers restrict the vehicle operating range, and may involve gain scheduling to extend that range. Many times, this leads to unsatisfactory performance outside of that range, with the possibility of undetermined behavior. A solution to this problem would be to utilize nonlinear controllers where vehicle nonlinearities can be accounted for in the control law. Ivan is using a backstepping technique for the theoretical development of these controllers, followed by validation in simulation and experimental field trials.
Name: Chris L’Esperance
Department: Department of Oceanography
School: Dalhousie University
Project: A compact, unattended gas chromatographic system for the measurement of dissolved gases from an unmanned surface vehicle
Research Advisor: Dr. Douglas Wallace (Department of Oceanography), D. Mae Seto (Department of Mechanical Engineering)
Chris received B.Sc. and M.Sc. degrees in Marine Biology and Chemical Oceanography from Dalhousie University in Halifax, Nova Scotia. Chris was among a group of scientists/engineers responsible for furthering the development of the SeaFET Ocean pH sensor following its tech-transfer from Monterey Bay Aquarium Research Institute (MBARI) to Satlantic LP. He made a significant contribution to the integration of a Pro-Oceanus Systems Inc. gas tension device (GTD) with an autonomous profiling explorer (APEX) float, having worked in close association with the senior research engineer responsible for float modifications/sensor integrations at the University of Washington’s Float Laboratory. Chris has strong interests in analytical instrumentation, ocean biogeochemistry and ocean acidification research. Chris is currently working with the Canada Excellence Research Chair (CERC) in Ocean Science & Technology group at Dalhousie University under the supervision of Dr. Douglas Wallace (Oceanography) and Dr. Mae Seto (Mechanical Engineering). With support from the Link Foundation, Chris is developing a compact, unattended gas chromatograph (GC) system for the measurement of dissolved gases. The System will be integrated into the unmanned surface vehicle (USV), Dorado, in support of tracer injection experiments.
Eddy diffusion coefficients are included in ocean circulation models in order to describe the transport of momentum, heat and tracers owing to a variety of mixing processes operating on sub-grid space and time scales. The practical applications of such models include prediction of the dispersion of oil, waste drilling muds and other pollutants. Eddy diffusion coefficients may be estimated by performing dye/tracer injection experiments and through subsequent monitoring of the dispersion of the dye/tracer over space and time. Uncertainties associated with estimates derived from the analysis of tracer dispersion data, however, are large. Bearing heavily on these uncertainties are the speed, endurance and size of the platform used to make tracer concentration measurements, as well as, the sensitivity of the detector employed. We endeavor to enhance the spatial and temporal resolution, as well as reduce the analysis effort of tracer concentration measurements during deliberate tracer release experiments.
Our approach consists of the development of a rugged, GC system for the detection of the conservative tracer, SF6CF3. The instrumentation will be integrated into the snorkeling semi-submersible, Dorado vehicle (International Submarine Engineering, Port Coquitlam, B.C.). A tracer injection experiment which includes implementation of an intelligent vehicle sampling strategy will be carried out in coastal waters. Overall, the methodology is intended to constitute a rapidly-deployable, relocatable procedure for estimating eddy diffusivities which accurately describe the effects of the local mixing conditions.
Name: Andrew Mullen
Department: Applied Ocean Science
School: Scripps Institution of Oceanography, UCSD
Project: A Novel In Situ Microscope for Studying Benthic Organisms
Research Advisor: Dr. Jules Jaffe
Andrew is a PhD student at the Scripps Institution of Oceanography. He aims to spur scientific discovery through engineering by creating in situ instruments to study biological processes as they naturally occur in the ocean. As an undergraduate, Andrew studied civil engineering at the University of Notre Dame, during which he pursued research interests in applying engineering to environmental science. There he studied groundwater hydrology and saltwater intrusion along the coast of Benin, Africa with his advisor Dr. Stephen Silliman. While on the project, Andrew traveled to Benin for two summers using a variety of instruments to collect data from remote field sites and improve models being used to plan the area’s long-term freshwater sustainability. After his junior year, Andrew received a NOAA Hollings scholarship, which allowed him to explore ocean science and technology through an internship at the University of Alaska Fairbanks. He worked with ocean gliders and high frequency radar systems to collect physical oceanographic data from the Arctic Ocean as part of a larger effort to model water transport and circulation near potential future offshore drilling sites. Through these research experiences, Andrew gained the appreciation for the value of novel observational methods and the importance of studying environmental processes in their natural setting.
Following these interests in instrument development and field-based research Andrew entered the Jaffe Lab for Underwater Imaging at the Scripps Institution of Oceanography. Here he is developing a novel diver-operated underwater microscope to study benthic habitats such as coral reefs and kelp forests. Small-scale biological processes in these habitats often serve as mechanisms that control community structure and ecosystem health, yet it is difficult to replicate important phenomena in the lab. This novel instrument provides the ability to unobtrusively observe these processes as they naturally take place in the field. A prototype of the Benthic Underwater Microscope (BUM) has been used to image corals in situ at a resolution that enables distinguishing and observing individual zooxanthellae, single celled symbiotic algae (~10 micrometers in diameter) which provide corals most of their energy. Applied research using the instrument will examine the ecology and physiology of competition between corals and turf algae, which can overgrow reefs leading to significant losses in habitat and biodiversity. The system is also being enhanced to incorporate micro Particle Image Velocimetry (PIV), a technique for observing two dimensional flow fields. This capability will provide a means to investigate the biophysics of small-scale organism-fluid interactions, which are important to activities such as filter feeding and chemical transfer.