Long-Term - Develop an autonomous underwater vehicle capable of economical long-term operation that can maintain station or carry out a simple sampling track, reporting results and receiving instruction through satellite.
The Autonomous Lagrangian Circulation Explorer (ALACE) is a neutrally buoyant subsurface float that occasionally increases its buoyancy in order to rise to the surface to relay observations through Argos satellites. The objective of this collaboration with Breck Owens of WHOI and Webb Research Corporation is to adapt ALACE technology to develop an electric powered winged underwater glider capable of long-term autonomous operations while sustaining average forward velocities of tens of kilometers per day.
In the collaboration Webb Research is responsible for the construction of the vehicle and actuators that move internal ballast in order to control flight. SIO is responsible for the system controller, flight control algorithms, selection of flight control and scientific instrumentation and integration into field-ready instrument. WHOI is responsible for overall coordination, development of two-way satellite communication techniques and coordination of field testing of the completed system.
In preparation for developing control algorithms, a flight simulation program was developed. This is based on lumped aerodynamic parameters (drag and lift curves vs. angle of attack) for each element. These aerodynamic parameters were estimated from some short-duration flight tests carried out by Webb Research. This program will be used to test control algorithms before they are field tested.
While awaiting delivery of the vehicle hull, development focused on acquiring and testing subcomponents (central controller, compass, tilt sensors, 16 bit A/D for the CTD system, etc.) writing software for these parts and testing it. Where possible, these components were used in other laboratory procedures to gain experience in their operations (i.e. the controller and 16-bit a/d were used in calibration procedures for the CTD ALACE).
Webb Research delivered its initial prototype vehicle in October 1996. Subsequently, the glider prototype has been fitted with actuator drivers and the central controller. The central controller software for flight control has been completed and tested, allowing us to control trim, buoyancy, and to drop into a low-power mode. This will facilitate the next stage of testing vehicle response at the surface and flight control characteristics under steady-state conditions. We intend to have the vehicle ready for field testing by Spring 1997.
Impacts
If successful, this development will lead to an inexpensive instrument platform capable of multi-month missions covering O(1000 km) at an operational cost much lower than any other controllable ocean instrument. Applications in which a ship launches an array of autonomous gliders or in which a glider maintains station without the expense of a mooring are anticipated.
Other_projects
This is a component of the Autonomous Ocean Sensor Network initiative. If the instrument is field ready it will be used in the ONR sponsored Deep Convection ARI where it would be used to observe the horizontal structure of convection plumes.