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CICEET Progress Report for the period 8/01/00
through 1/31/01
Project Title:
An Autonomous Profiler for Estuarine Research and Monitoring
Principal Investigator(s):
Rocky Geyer, Daniel Frye and Kenneth Doherty
Woods Hole Oceanographic Institution
Woods Hole, MA 02543
UNH Subcontract Agreement No. 01-470
Accomplishments
The effort to date has consisted of developing a conceptual design
for the autonomous profiling system, exploration of the appropriate
materials and components, and definition of the detailed requirements
for the system. The development of the profiler has been divided
into three phases, the first to develop the profiling winch, the
second for the sensor buoy, sensors, RF link and controller, and
the third to test the profiler in the field.
Phase 1
Design, construct and test the winch drum, line and guide wheels,
motor/gear head, shaft bearing, motor housing, motor controller
(hardware and software), battery pack and housing, and frame.
Conceptual Design for the Estuarine Winch
We will use 1/8 inch or smaller Vectran line and a plastic
winch drum that is 8-12 inches in diameter and 1-2 inches
wide. The drum will be driven by a brushless DC motor in air
through a 200:1 gear head. An oil-filled bearing box with
dual O-ring seals will seal the shaft. We will evaluate constant
back-torque as a means of slowing ascent and recovering slack
line. We will evaluate the need for level winding and the
need for maintaining a low fleet angle on the winch line.
Winch control will be handled with a TT8 single board computer
and a motor controller board. Winch ascents and descents will
be on a scheduled (time) basis. Time at the surface will be
minimized except when telemetry is scheduled. The winch will
operate as follows:
a) At time T1, brake is released and buoy begins ascent.
b) Time T2, motor is energized and retrieval begins.
c) Monitor motor current during retrieval and when the value
exceeds a threshold value, retrieval ends.
d) Next cycle begins N minutes after T1.
e) If a telemetry cycle is scheduled (typically once or twice
per day), Time T2' is set longer to allow the appropriate
time on the surface.
Specifications
a) Hourly profiles in 20m of water for 60 days (60,000m
of profiling).
b) Profiling speed- 10 to 15 cm/sec (of order 5-10
minutes/profile).
c) Winch line- 30m.
d) Winch motor- 30-50 Watts (150 W maximum)
e) Controller clock drift- 10 sec/month
Schedule
a) March 15, 2001- Complete design and drawing package
for Phase I prototype.
b) April 30, 2001- Complete parts acquisition and
machining.
c) May 31, 2001- Complete winch assembly and TT8
software development for the winch controller.
d) June 2001- Begin dock tests of winch system.
Phase II
Design, build and test the buoy/sensor module and modify the
winch module based on the tests of the Phase I prototype.
Concept
We plan to use a Seabird Model 19 CTD with DO, turbidity
and fluorescence sensors. We also were planning to use Orbcomm
for telemetry, but given the uncertainty of Orbcomm's future,
we have decided to develop a cell phone based telemetry module.
We may also include a GPS receiver or Argos PTT to track buoy
location in case of failure of the winch line or if the entire
system gets dragged. The electronics and batteries will be
installed in a lightweight foam buoy module rated to at least
100m. It will provide about 20 pounds of net buoyancy and
will be streamlined to minimize current drag. Provision will
be made to adjust buoy buoyancy based on the Phase I test
results. The sensor buoy system will operate independently
of the winch module in the following manner.
a) Based on controller clock, the CTD (and other sensors
will turn on a minute or so prior to the start of a profile.
b) The CTD will record data for a set period of time a few
minutes longer than the anticipated ascent and descent times.
c) When an RF transmission is scheduled, the cell phone in
the buoy will initiate a call and transfer all of the data
collected since the last transmission as well as various engineering
data.
Specifications
a) CTD sample rate 2 Hz
b) Data storage- 40 Mbytes
c) Buoy- Fifteen- 25 pounds of buoyancy. Cylindrical pressure
housing containing CTD and other sensors, TT8, flash disk,
cell phone, antenna, GPS receiver and lithium batteries.
Schedule
a) Design buoy module and order components and parts- August
2001.
b) Assemble and test buoy module and modify winch based on
prior in-water tests- October 2001.
c) Test complete prototype locally- December 2001.
Phase III
Conduct test deployments of the operational winch system in Hudson
estuary and in South Carolina estuary.
Schedule
a) Hudson- March 2002
b) Carolina- May 2002
Present Status
We are on schedule at the present time. The initial winch design
is nearly complete and we will place orders for all the components
by the middle of March. Software development for the winch controller
will begin in April. The present Phase I schedule has been delayed
several months relative to our proposal, but should not impact
our ability to develop the winch system during the project period.
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