Environmental disturbances

Modeling, system identification and controller design for a 16’ catamaran is
described with the objective of enhanced operation in the presence of environmental
disturbances including wind, waves and current. The vehicle is fully-actuated in surge,
sway and yaw degrees of freedom. Analytical and experimental system identification is
carried out to create a numerical model of the vehicle. A composite system of a Multiinput
multi-output Proportional-Derivative (PD) controller and a nonlinear disturbance
observer is used for station-keeping and transiting modes of operation. A waypoint
transiting algorithm is developed to output heading and cross-track error from vehicle
position and waypoints. A control allocation method is designed to lower azimuthing
frequency and incorporate angle saturation and rate limits. Validation is achieved with
improvement in simulation with the addition of the nonlinear observer.

Disturbance events occur outside the normal disturbance regime of a system and
can cause changes in behavior of some organisms. The 2010 cold event is an example of
a disturbance event that influenced the behavior of Common Snook (Centropomus
undecimalis). Common snook are euryhaline sportfish native to Florida, Texas, and the
Caribbean. Florida is the northern most part of their distribution, based on the 15o C
winter isotherm. They move between offshore areas during spawning season and
freshwater coastal rivers during non-spawning season. With the use of previously
collected acoustic telemetry and biological data this project identifies the impact on
population dynamics and movement near the time of the event. The goal is to understand
fine scale movements and physiological conditions under normal and abnormal
conditions to further inform management of the species.