Moorings for Ocean Observatories - Aloha Mooring

Moorings for Ocean Observatories: Continuous and Adaptive Sampling
Bruce M. Howe, Tim McGinnis, and Jason Gobat
Applied Physics Laboratory, University of Washington
1013 NE 40th St. Seattle, WA, USA
Abstract – Present autonomous moored profilers often
undersample the ocean and alias “high” frequency processes
such as tides and internal waves because they are slow and
have short missions and/or intermittent sampling schedules. To
improve this situation we are developing a moored profiler
system to be connected to a cabled observatory node, thereby
removing power as the major constraining factor. A profiler
docking station with an inductive coupler will transfer power
from the cabled node to a modified McLane moored profiler
(MMP). This will permit near-continuous profiling (>90% duty
cycle) at 0.25 m s–1. Further, two-way inductive
communications will be used to offload profiler data at modest
rates in real time as well as transfer adaptive sampling
commands. With sensors on the profiler and with dual sensors
at fixed points top and bottom on the mooring, crosscalibration and overall robustness will be improved.
Secondary junction boxes on the subsurface float and on
the seafloor will provide several hundred watts, 100 Mb/s
Ethernet, precise time, and be ROV-serviceable. Instrument
packages can be added on the subsurface float, such as a
winched profiling system to carry in-situ and point and remote
sensors through the mixed layer to the surface.
This mooring will be tested in mid-2006 in Puget Sound
and deployed on the MARS cabled observatory system in
Monterey Bay, California, in 900 m of water in late summer
2007. These developments enable a wide range of new sensing
modalities with moored profiler systems, one essential element
(hybrid fixed-mobile sensor platform) of ocean observatory
sensor network infrastructure. The current system design is
presented.
The sampling and observational methods developed here
will be transferable to ocean observatories elsewhere in the
world.
After testing a short version of the mooring system in
Puget Sound, the system will be deployed in Monterey on
the MARS observatory [9] in summer 2007 and likely
recovered in summer 2008. A successor mooring will be
proposed for the ALOHA Observatory north of Oahu after a
cabled node is installed [10, 11]. Additional moorings of
this type are expected to play a significant role in the NSF
funded ORION program and the Ocean Observatories
Initiative (OOI) [2, 12, 13, 14, 15, 16, 17, 18].
I. INTRODUCTION
The ALOHA-MARS Mooring (AMM) project will
demonstrate the scientific potential of combining adaptive
sampling methods with a moored deep-ocean sensor
network. It is desgined for use with seafloor observatories
with power and communications provided by a connection
to shore via an electro-optical cable [1]. This system will
address the challenge of sampling the ocean with both high
temporal and vertical resolution [2, 3, 4, 5, 6, 7, 8]. The
mooring will consist of three main components (Fig. 1): a
near-surface float at a depth of 165 m with a secondary node
(J-Box) and suite of sensors, an instrumented motorized
moored profiler moving between the seafloor and the float
that will mate with a docking station on the float for battery
charging; and a secondary node (J-Box) on the seafloor with
a suite of sensors. Both secondary nodes will have ROV
mateable connectors available for guest instrumentation.
The profiler will have real-time communications with the
network via an inductive modem that will provide some
remote control functions to allow the sampling and
measurement capabilities to be focused on the scientific
features of greatest interest. The power and two-way realtime communications provided by cabled seafloor
observatories will enable this sensor network, the adaptive
sampling techniques, and the resulting enhanced science.
Fig. 1. Concept Observatory Mooring Sensor Network,
originally planned for the ALOHA Observatory north of
Oahu at the Hawaii Ocean Timeseries (HOT) site, now
planned for the MARS Observatory in Monterey Bay in
900 m water depth [1].
1
II. GENERAL DESCRIPTION
laid and connected with a ROV equipped with cable
sled/reel.
The AMM is a deep ocean sensor network that extends
from the seafloor at ~900 m water depth to a subsurface
float at 165 m. The mooring contains three “nodes” that
include power supply and network connections and suites of
sensors located on the seafloor, on the subsurface float, and
on a moored profiler that is capable of traversing from the
seafloor to the float (Fig. 2). At all three locations are
CTDO2 and optical backscatter sensors. The float will also
have an ADCP, camera, and attitude sensor and the profiler
will have an acoustic current meter.
The AMM is electrically connected to the MARS
Observatory Node (the “primary” node), which provides
400 and 48 Vdc power, 100BaseT Ethernet communication,
and precision time distribution. Each secondary node in the
AMM provides 48 Vdc, 100BaseT Ethernet, and precise
time distribution to users via ROV-mateable connectors.
The profiler communicates in real time with the float
secondary node via an inductive modem.
Command and control of the mooring as well as data
monitoring and archiving is accomplished from shore via
the MARS network. Voltages, currents, and ground faults
throughout the system are monitored and action taken as
necessary to connect or disconnect secondary networks or
instruments remotely.
The syntactic foam float and mechanical structure
serves as a mounting platform for the float secondary node
and sensors (Fig. 3). The framework around the float is
designed for ease of serviceability by ROV and it has a
modular design to simplify modifications and allow for
future expansion.
AMM
uses
a
combination
of
electrical,
electrical/mechanical
(EM)
and
electrical/optical/
mechanical (EOM) cables. The long cables (>100 m) are
EOM type, which allows optical Ethernet communication
and the short cables are EM type and use twisted pair wire
Ethernet communication. The EOM and EM cables use
synthetic fibers (Kevlar or Vectran) as strength members.
The EOM cables contain a stainless steel tube with four
optical fibers for communications.
The system uses a variety of underwater electrical
connectors. The science connector ports (on the MARS
primary node and the mooring system secondary nodes)
utilize ROV-type wet mateable electrical connectors. The
number of these ROV wet mateable connectors is limited
because of high cost. Whenever possible, dry mate
connectors are used and components that do need an ROVtype disconnect are grouped together with a Science
Instrument Interface Module (SIIM) to allow the use of a
single ROV connector to connect multiple instruments. The
EOM cables are connected into the system with EO
penetrators. An Ethernet optical-to-electrical “in-line”
converter is inserted between the EO cables and electrical
connections at the primary and secondary node science
connectors. The sensors are attached by dry mate
underwater electrical connectors to the SIIM, which has a
single ROV wet mateable electrical connector.
Deployment and recovery requires a dynamically
positioned (DP) ship and an ROV. Deployment is anchor
first. A special rail frame system is used on the fantail to
facilitate deployment operations. The seafloor cable will be
ROV-serviceable
Instrument
Platform
Swivel/Sliprings
Termination and
EO Converter
Inductive Power
System Coupler
MMP Profiler
Fig. 2. Upper part of mooring, with profiler
Instrument
SIIM Bays
TI Center
Post in Slot
ROV-mateable
Receptacles
2ndary Node
Electronics (with
IPS, IM, attitude,
ADCP, camera)
ROV
Positioning
Pins
Cable Termination
with EO Converter
Guard
Rail
SIIM
Float, 2400 lb
floatation
Swivel, 16
conductors
Cable, 0.825in, 4
fiber, 6 conductor,
kevlar, fishbite
Fig. 3. Subsurface float detail
III. FUNCTIONAL REQUIREMENTS
The science user requirements are [11]:
• Provide full water column current profiling Near
continuous in-situ profiling from near surface to
seafloor with CTDO2, acoustic current meter (ACM),
bio-optics
• Profiler rate of advance will allow one sampling
cycle per tidal half cycle (6 h)
• Profiler charging time (in dock) must be less than 6 h
• Profiler duty cycle must be greater than 90%
• Provide extra science user connectors with standard
power and data interface on float and seafloor
2
• Provide
near
real-time,
high-bandwidth
communication for science user instruments
• Compatible with MARS power and data interfaces
• Provide 48 Vdc, 100BaseT communications, and PPS
Timing at Science User Connectors
• Provide interface method for standard RS-232
sensors
• ROV serviceable with replaceable instrument
packages
• Testable during deployment
• Operational life of >2 years
• Located far enough from the primary node to allow
ROV access to observatory node and instruments
In the long-term we want to work towards the concept
of the profiler as a “truck” responding to science commands.
This will make the system more modular and easier to
improve, e.g., to increase the speed and payload.
maintainability in the infrastructure and also to allow
science instruments and SIIM to be connected and
disconnected by ROV without bringing any of the
equipment to the surface. There will be ROV mateable
science connectors at both the seafloor and float nodes. The
science connectors will be compatible with the science
connectors on the MARS primary node, and also with the
science connectors on the VENUS [19] and NEPTUNE
Canada [20] nodes (albeit the latter do not provide 48 V).
The science connectors are supplied by Ocean Design, Inc.,
and have 12 pins: 400 Vdc (2), 48 Vdc (2), 100BaseT
Ethernet (4), PPS Timing (2), Spare (2).
In-line media converters are required to convert
electrical communication and timing signals to optical form
for transmission over any significant distance using optical
fibers and back again. The seafloor and mooring riser cables
both have four fibers. One optical fiber is used for the
Ethernet communications, and one for the PPS/RS-422 time
distribution and two are spares. Wave division multiplexers
(WDMs) allow bi-directional data transmission using 1310
and 1550 nm wavelengths on the fibers. The Ethernet and
time distribution converters (Omnitron models 8910/8790)
plug into a common backplane that provides power to the
converters and also provides SNMP management of the
converters. Management features include event monitoring,
trap notification, and temperature range violations. It will
also send a “Dying Gasp” trap if it loses power. The EO
converters will be housed in a beryllium-copper pressure
case, 4.38-inch inside diameter, 12.8 inches long, weighing
32 lbs, and rated for 5000 m. (Beryllium-copper was chosen
because it is now cheaper than titanium.)
The cable between the primary node and the seafloor
secondary node junction box is a 12.7-mm diameter
electrical/optical cable with six conductors and four single
mode optical fibers in a 1.2-mm stainless steel tube. An
electro-optical penetrator terminates each end of the cable
into the EO converter. ROV mateable connectors will allow
connection of the cable to the primary and secondary nodes.
The Seafloor cable (with EO converters and connectors) will
be installed by ROV with a reel that will be mounted in the
cable laying tool sled on the ROV; the spool will be left on
the seafloor at the end of the cable laying process.
IV. SYSTEM DESCRIPTION
A schematic block diagram (Fig. 4) show that a seafloor
extension cable connects the primary observatory node to
the mooring system seafloor secondary node. Connected to
the latter are the mooring, project instruments, and guest
instruments. The mooring cable rises through the water
column to the subsurface float. There, a float secondary
node connects to project instruments, guest instruments, and
transfers power and communicates with the profiler.
B. Secondary Nodes
The AMM will have two secondary nodes that will
provide the same connectivity functions that are available at
the primary observatory nodes, though with reduced power
and communications rate capability. Fig. 5 shows the basic
block diagram for the secondary nodes; there are small
differences between the seafloor and float secondary nodes
that will be discussed in the following sections. Much of the
design is based on that of the MARS power system [21].
ROV mateable connectors are the same as on the
MARS primary node. An input of 400 V can come in on any
connector; there is one 400 V output, either on one
connector for the mooring cable (seafloor node) or internally
to the inductive charging system (float node). All connectors
output 48 V.
The precise timing signal is split into four and
distributed to the user connectors.
Fig. 4. System Block Diagram
A. MARS Observatory Interface
The voltages available at the MARS Observatory Node
will be 400 Vdc and 48 Vdc. The overall power budget for
the mooring system is approximately 500–1200 W,
depending on whether the MMP is being charged and if any
additional guest instruments are connected. The data
communications provided by the MARS Observatory is
100BaseT Ethernet. This will be provided at each of the
Secondary Node Science Connectors. RS-232 will be
provided by a science instrument interface module (SIIM)
located at each secondary node. The time distribution will
include two different levels of resolution and access: on the
order of 1-10 ms, a Network Time Protocol (NTP), and on
the order of 1–10 µs, a GPS pulse-per-second (PPS) signal.
ROV underwater mateable connectors will be utilized
on the underwater nodes to allow modularity and
3
400V
Load P ow er
S w itching &
M onitoring
400V
48V
Load P ow er
S w itching &
M onitoring
G round
F ault
M onitoring
400V
48V
E th
PPS
P C /104
C ontroller
A nalog
48V
12V
5V
MARS
S cience
C onnectors
S IIM
400V
48V
E th
PPS
MARS
S cience
C onnectors
G uest
Instrum ent
400V
48V
E th
PPS
MARS
S cience
C onnectors
G uest
Instrum ent
48V
E th
PPS
E thernet
S w itch
D C -D C
C onverter
400V -48V
M ooring
C able
E thernet
400V
E xtension
C able to
MARS
N ode
MARS
S cience
C onnectors
D C -D C
C onverter
48V -5/12V
E th
PPS
PPS
R S -422
R epeater
Fig. 5. Secondary node general block diagram
node was done in consultation with the ROV pilots at
MBARI.
The seafloor secondary node has the following:
• Five ROV-mateable connectors
o one for connection to the MARS node via the
seafloor cable
o one for connection to the mooring riser cable
o one for connection to the seafloor SIIM
o two available for guests
• Power capacity
o AMM sensor load ~15W
o 48 Vdc to guest ports, total power ~200 W
• Removable ballast (lead weights) and “fork” slots to
facilitate moving the entire frame with ROV
• Flotation (glass or ceramic spheres) to keep the
weight within the paylod limits of the ROV
The AMM seafloor sensor module is a small rack
suspended on the mooring a few meters above the anchor.
The rack is designed to hold at least four sensors connected
electrically via a SIIM (on the rack, too) to the seafloor
secondary node by a 12-m cable and ROV wet mateable
connector.
The float secondary node has the following:
• Three ROV mateable science user connectors
o one for connection to the float SIIM
o two available for guests
• Power capacity
o AMM sensor load ~45 W
o 48 Vdc to guest ports, otal power ~100 W
• Inductive power coupler electronics (see below)
• Internal SIIM electronics modules (see below)
connected to:
o Sea-Bird inductive modem (for communication
to profiler)
o Attitude sensor
o Acoustic Doppler current profiler (ADCP)
o Video camer and light
The secondary node controller (SNC) consists of a PC104 stack with a Diamond Prometheus CPU board with
analog I/O, a MOSFET power switching board and a
mechanical relay board. The SNC acquires data from the
current sensors, the ground fault isolation circuits, and
controls the relays. It communicates with the shore server
via the 100Mb/s Managed Ethernet switch (Sixnet
EtherTRAK, 9 ports, SNMP management), through which
all the communications to/from the instruments also pass.
Within the secondary nodes are six custom printed
circuit boards: 400–48 V/300 W dc–dc converter,
48-12 V/150 W dc–dc converter, load control and
monitoring, ground fault detection, timing converter (RS422
to 1 PPS), and timing repeater (four channels out).
Vicor dc–dc converters (with filtering) are used
throughout. Each secondary junction box consumes about
40 W for the “hotel” load, and there is ~200–400 W
available for other uses (instruments, inductive power
system, etc). The load control and monitoring board has a
current sensor, a deadface switch to provide galvanic
isolation, and a semiconductor FET switch for each 48-V
channel. Both switches are controlled by the power
management and control system (PMACS). The maximum
current/power through these switches at 48 V is 2 A/100 W.
The ground fault protection board cycles through the output
channels, making a measurement on a separate channel
every 10 s; this circuit is based on a similar one used in the
MARS system. The timing converter board converts the RS422 signals to TTL 1 PPS signals, and then the repeater
board splits the latter to the four science connectors. These
components are packaged in a stainless steel (SS 17-4PH)
pressure case, 7-inch inside diameter by 30.5 inches long,
weighing 230 lbs, and rated for 6000 m.
The seafloor secondary node serves as the terminus for
the 1.7-km seafloor EOM cable that runs from the MARS
node to the base of the mooring. The node will include a
frame, electronics housing, and ROV mateable electrical
connector receptacles (Fig. 6). The mechanical design of the
4
ROV-mateable
connectors
D. Sensors and Instruments
The fixed sensors will be sampled once per second. The
sensors on the profiler will be sampled as fast as possible:
for the MMP sensors (CTDO2, ACM) this is nominally at
1.8 Hz (every 0.14 m at 0.25 m s–1) while for the BB2F, this
is nominally at 1.15 Hz.
The Sea-Bird 52MP/43F CTDO2 will be used, two each
(for redundancy) on the subsurface float and at the base of
the mooring, and one on the profiler. These have titanium
pressure cases rated for 6000 m. They use a pump to control
the flow past the thermistor and through the conductivity
cell.
The WetLabs BBF2 sensor will measure optical
backscatter at 470 nm and 700 nm, and chlorophyll
fluorescence within the same volume. There will be 1 each
on the float, on the seafloor and on the MMP.
The ADCP on the subsurface float is a RD Instruments
Workhorse Sentinel 150 kHz. It is mounted permanently on
the float with a dry mate connector to the float secondary
node electronics case. The ADCP has an integral attitude
sensor package.
The ACM on the profiler is a Falmouth Scientific 4-axis
device measuring a 3D velocity vector.
To better understand the float/mooring dynamics,
related stresses, and impact on the optical fibers, an
orientation sensor package will be included inside the
secondary node electronics case. A 3DM-GX1 Gyro
Enhanced Orientation Sensor combines three angular rate
gyros with three orthogonal DC accelerometers, three
orthogonal magnetometers, multiplexer, 16-bit A/D
converter, and embedded microcontroller to output its
orientation in dynamic and static environments.
There will be a color video camera with lights on the
subsurface float looking at the profiler dock to monitor the
MMP docking and undocking. The primary purpose of this
camera is to better understand the MMP docking dynamics
and to ease any necessary trouble shooting. The camera is a
Deep Sea Power and Light LED Multi SeaCam.
Electronics
ROV
“fork”
slots
Removable
ballast
Fiberglass grating
Fig. 6. Seafloor secondary node (buoyancy not shown)
C. Science Instrument Interface Module (SIIM)
Attached to the secondary nodes will be a number of
science instruments:
• Dual SBE 52MP CTDO2
• Wetlabs BB2F bio-optical sensors
• RDI 150kHz Workhorse ADCP (float node only)
• DSPL Video camera with lights (float node only)
To minimize the number of ROV wet mateable
connectors used, an intermediate multiplexer/SIIM is
required to first connect all the sensors together (using dry
mate connectors); then the SIIM is connected to the
secondary J-box housing using a single ROV-mateable
connector. This SIIM will need to have a mix of the
following features:
• Four–eight RS-232 ports (dry-mate connectors)
• One–two video inputs
• Provide required instrument voltages (48 Vdc and
12 Vdc)
• Provide RS-232 to Ethernet conversion (to
communicate with higher level node)
• Node ROV mateable cable connector interface
• Individual software controlled load switching and
deadface switching
This is accomplished with a custom, easily modified,
four-channel printed circuit board, a “SIIM board.” Each
channel has a Digi Connect ME embedded module, a FET
switch, and a deadface relay. The Digi Connect module
provides a 10/100BaseT network interface, one high-speed
RS-232 serial interface, 2 MB Flash memory, and 8 MB
RAM. It is built on 32-bit ARM technology using the
network-attached NetSilicon NS7520 microprocessor. It
provides an extremely convenient way to convert instrument
RS-232 to Ethernet. It is the only “smart” device in the
SIIM.
On the float and at the base of the mooring, the SIIM
board will be housed in a titanium pressure case 130 mm
inside diameter by 345 mm length (5.13 inches by 13.6
inches), weighing 30 lbs in air, and rated for 5000 m.
A SIIM board will also reside in the float secondary
node for the attitude sensor, ADCP, Sea-Bird inductive
modem, and video camera.
E. Moored profiler
This project will modify and use the McLane Moored
Profiler (MMP, Fig. 7).
Fig. 7. The standard McLane Moored Profiler
5
secondary cores are engaged, as indicated by a
proximity/contact switch, current will start to flow. Keeping
the mating gap small is crucial to the transfer of power.
Similarly, the MPC will be continually polling the MMP
controller and as soon as the MMP docks, the MMP will
reply and the data transfer will begin.
This project will modify the standard design:
• New motor, gearbox, wheel redesign to fit larger
EOM cable (0.85 inch, ~22 mm)
• Mount WetLabs BB2F optical sensor
• Use Sea-Bird 52MP/43F CTDO2
• Interface APL MPC controller to the MMP controller
to offload data after every profile
• Replace primary Li battery pack with rechargeable
860 Wh Li-ion battery bank mounted in glass sphere
• Mount inductive charging coupler and electronics
• Use extended length McLane housing with additional
glass sphere for rechargeable battery bank and for
increased buoyancy
• Ratio run time : charging time = 4 days : 4 h with
reasonably sized battery bank
APL will be adding a Moored Profiler Controller
(MPC) to the modified MMP. The MPC hardware will
consist of a motherboard, CF-2 CPU board, and two OES
U4S 4-port Serial Communications boards. The primary
tasks of the MPC are:
• Collecting optical data (backscatter and fluorescence)
• Interfacing with and downloading data from the
MMP (CTDO2, ACM, engineering data)
• Interfacing with and transferring data/commands
to/from the shore server (SS)
• Interfacing with and controlling the MMP Battery
Controller (MBC)
• Supervising charging of the battery bank
All communication between the MMP and MPC is
initiated usingASCII text messages. Some messages have
the ASCII text string immediately followed by binary data
(in particular, messages containing file content). Messages
can be sent from the MMP to the MPC, including ready
indicator, docking and obstruction status, the current
pressure, and files and directories. Commands can also be
sent from the MPC to the MMP, for instance, to instruct the
MMP to go to the charging dock and to request files and
directories.
Table 1. Inductive power system specifications
Supplier
S&K Engineering
Input voltage
400 Vdc
Input Power
up to 300 W
Output voltage
15 Vdc
Output Power
up to 225 W
Efficiency
70% with 2 mm gap
Operating Frequency
~100 kHz
Primary
on cable
Secondary
on MMP
Attach to MMP
2-inch spring
F. Inductive Power System (IPS)
The inductive power transfer to the profiler is one of the
key new technical development of the project.
The MMP will periodically connect or “dock” to the
mooring float infrastructure to charge its battery bank. Due
to the fact that the system components are submerged in
conducting seawater, the connection must not utilize any
contacts that allow an electrical connection to contact the
seawater. Wet mateable connectors that have enclosed, oilbathed contacts have some potential for this but they
typically require a relatively high mating force and have a
limited number of mate/de-mate cycles. The technique that
has been selected is to use inductive coupling for the power.
S&K Engineering has been contracted to make the inductive
power coupler (the “dock”) and the associated drive and
charging electronics [22].
The solid works model of the inductive coupler is
shown in Fig. 8. Specifications are given in Table 1.
At the end of a profile, the MMP with the coupler
secondary core will ascend and make contact with the guide
and coupler primary core. As soon as the primary and
Fig. 8. Moored profiler inductive coupler
A block diagram of the inductive charging system is
shown below, Fig. 9.
The DC–HFAC converter (DHC) converts the float
400 Vdc to a high-frequency alternating current (HFAC)
that can be transmitted across the inductive coupler. This
circuit board, inside the float secondary node housing,
generates 40 W of waste heat that is conducted to the
pressure case endcap through a long wedge section of
copper.
The primary and secondary ferrite cores can survive
long term submergence in seawater (cf. Sea-Bird inductive
modem). The shapes and mechanical design of the cores
will need to allow reliable coupling between the primary and
secondary and be tolerant of biofouling. Both the primary
and secondary cores will be bolted around the mooring cable
(a future version might have them more easily removable for
ROV servicing).
6
PRIMARY SIDE
continue to be used. If the temperature exceeds 100°C a fuse
opens and the battery is permanently disabled.
The battery charger function is contained on the IPS
HDR board, located in the MMP pressure housing.
Li-ion batteries need to be charged with a constant
current until the cell/pack voltage is 4.1 V/16.4 V and then
with that constant voltage until the charging current drops
below some desired fraction of the original charging current.
The rate of change of pack capacity falls off after 4 h and
reasonable efficiency would be obtained by terminating the
charge with a pack/bank charging current of 1 A/5 A, which
is reached in a little over 4 h. The last hour of charging
(20% of the charge time) only increases the capacity from
11.5 to 12.2 Ah (6% increase). Li-ion batteries do not have
any “memory effect” and, consequently, there is no negative
impact from terminating the charge before 100%.
Terminating the charge earlier may also reduce the chance
of over charging the battery cells which would cause
permanent damage.
The MMP Battery Controller (MBC) is a custom
designed microcontroller board whose primary function is to
tell the MPC the state of battery charge, so it can instruct the
MMP to go to the docking station when the batteries need
recharging. The MBC monitors the battery voltage and
current, monitors battery temperature, and estimates battery
charge level (coulomb counter). Based on these data, the
following check/actions are performed:
• Temperature–charging permitted only between 0°C
and 45°C
• Charge current must not be too high, typically below
0.7C, where C = 12 A/pack (for the bank of five
packs, the maximum charging current is 42 A)
• Discharge current protection to prevent damage due
to short circuits
• Charge voltage–permanent fuse opens if too much
voltage is applied to the battery terminals
• Overcharge protection–stops charging when voltage
per cell rises above 4.30 volts
• Over-discharge protection–stops discharge when
battery voltage falls below 3.2/12.8 volts per
cell/pack.
External Communication
POWER SYSTEM
MICROCONTROLLER
Local Battery
Management
Input Power
From Current Source
DC-HFAC CONVERTER
SHUNT REGULATOR
Series-Resonant 100kHz
PRIMARY SIDE
BATTERY CHAEGER
High Frequency AC Power
Inductive Power
Coupler
PLATFORM
CRAWLER
High Frequency AC Power
HFAC-DC ACTIVE
RECTIFIER
REGULAOR
Connection to Crawler Battery
Voltage and Current Monitor
Battery Charge Controller
CRAWLER SIDE
POWER SYSTEM
On-Board
Communication
MICROCONTROLLER
Fig. 9. Inductive power system block diagram
The HFAC-DC rectifier (HDR) converts the HFAC
power to DC. The DC output can them be converted to the
required voltages with DC-DC converters. Again, a copper
plate attached to the backside of the circuit board conducts
20 W of waste heat to the endcap.
The efficiency of the inductive power coupler is
important for many reasons. Low efficiency leads to long
charge times and waste heat inside pressure cases. This IPS
can be considered a part of the sensor network
infrastructure. This project is clearly showing that the
infrastructure of sensor networks is a major use of the
observatory power. This complete mooring system is about
70% efficient overall; ~300 W is used for hotel electronics
and resistive losses. Power within a cabled observatory, as
well as an ORION “global buoy” observatory [23, 24], will
very quickly become a limited resource. The efficiency as a
function of the coupler gap varies from 72% at 0 mm to
68% at 5 mm; at 2 mm, the power transfer is 250 W.
The profiler battery bank must have sufficient capacity
to allow the profiler to operate for the required survey
duration. The profiler battery bank must utilize a chemistry
that has high power density, is capable of a high number of
charge/discharge cycles, and that can be charged as rapidly
as possible. Lithium ion batteries have been selected for
their good density, cycling and charging characteristics, and
have been selected. The AMM MMP battery bank consists
of five battery packs connected in parallel. Each of the packs
consists of two parallel stacks of four 3.6V Li-ion cells in
series. Charging every 4.6 days for 5 hours gives a 97% duty
cycle.
There are two built in protection functions to reduce the
risk of fire. When temperature increases past ~90°C, a
switch opens; when the temperature decreases below this
temperature, the switch re-closes and the battery can
G. Inductive Modem (IM) Communications
The SeaBird Inductive Modem (IM) system will be
used for communications between the float and the MMP.
The float will contain the IM node that is connected to shore
through the mooring network and the MMP will contain
another IM node that will connect to the MPC, allowing bidirectional communications. Communications rate is
nominally 150 bytes/s; with forward error correction and
other overhead the effective rate is 90 bytes/s.
H. Mooring Riser Cable
The 22-mm (0.85-inch) diameter mooring cable has six
18 AWG conductors with polypropylene insulation, four
loose fibers in a 1.3-mm diameter steel tube (in center), a
Kevlar strength member, and a steel mesh for fishbite
protection, all enclosed in a polyethylene jacket, Fig. 10.
This cable, connecting the seafloor secondary node to the
subsurface float and the float secondary node, has connector
terminations identical to the seafloor cable connecting the
7
modules allow for simple customization for individual
instrumentation and provide space for future instrument
expansion. The present instrument modules consist of a
simple titanium frame, a pressure housing, and a cable
storage tray. The pressure housing contains an Ethernet
switch, a science instrument interface module (SIIM), and
the appropriate voltage conditioning electronics for
connection to a sensor. The instrument modules are
connected electrically by a ~2-m cable and a wet mateable
ROV electrical connector to the connector manifold.
The surface float and structure have the following
characteristics:
• Designed for ROV servicing in collaboration with
MBARI and ROPOS ROV pilots
• Non-corrosive materials (plastic, aluminum, easily
made with water jet cutting)
• Secondary junction box, SIIM and float sensor
package, inductive modem, inductive power system,
two extra guest ports
• Instrument/SIIM with sensors (dual CTDO2, one
BBF2)
• Float structure slotted to engage titanium post at top
of mooring cable
• Slip ring/swivel beneath float (16 electrical passes)
Figures 2 and 3 show the float and structure. The 300-m
depth rated syntactic foam float is 1.829 mm diameter,
0.813 mm high, weighs 2052 lbs in air, and has a buoyancy
of 2400 lbs. The float stucture is made from 6061-T6
painted aluminum.
Using a SIIM permits combining several instruments
that are natural to have together (i.e., the CTDO2 and the
BBF2 bio-optical sensors) together in one package that can
be installed/removed easily from the network using an ROV.
An electro-mechanical swivel/slip ring assembly is used
at the top end of the mooring cable just beneath the
subsurface float. The swivel has 16 slip rings in an oil-filled,
pressure-compensated housing with an external pressure
compensator. The stainless steel swivel is rated at three
tonnes (6600 lbs) working load.
The mooring anchor has not yet been designed. It will
likely consist of either a stack of steel railroad wheels
mounted on a central hub, or a cast steel cylinder with an
eye (to minimize overall height above bottom).
MARS primary node to the seafloor secondary node.
Specifications for the mooring cable are given in Table 2.
Fig. 10. Cross section of 22-mm mooring riser cable
Table 2. Mooring riser cable specifications
Cable Type
EOM, water blocked
Manufacturer
Falmat
Length
800 m (2620 ft.)
Diameter
22 mm (0.865 in)
Conductors
six #18 AWG (4-power, 1-IM, 1spare), 21 Ω/km
Voltage Rating
1 kV, 2.5 A ac
Fiber optic
four fibers, Corning SMF-28™
Outer Jacket
Polyurethane, lime green
Fishbite Protection
Stainless steel braid, 70% coverage,
0.25 mm 304 SS wire
Breaking Strength
24,000 lbs
Working Load
4,000 lbs
Elongation
< 0.5% at working load (< 4 m for
4000 lbs and 800 m length)
Weight in air
864 lbs for 800 m (330 lbs/1000 ft)
Weight in water
241 lbs for 800 m (92 lbs/1000 ft)
J.
Software
The successful operation of the mooring sensor network
depends crucially on software [25].
The mooring will use a scaled-down version of the
MARS power management and control system (PMACS)
with the secondary node controller (SNC) serving a similar
role as the MARS node power controller. The shore server
will run a scaled-down version of the MARS PMACS server
program (this is a SOAP-based server). The PMACS
"console" will be a SOAP client process most likely running
in a web browser.
The secondary node controller (a PC-104 stack) will run
a modified version of the software from the MARS node
power controller. It will monitor load current and bus
voltage, allow for the setting of per-load current limits, and
provide circuit-breaker and ground-fault monitoring
I.
Mooring Float
The subsurface float tensions the mooring riser cable
and serves as an instrument platform. The float contains a
secondary node with ROV-mateable connector manifold, the
profiler dock (just below the float), four instrument/SIIM
bays, and several sensors. The secondary node operates as
the power and communication port for the instrument
modules and the moored profiler and is described in detail
above.
The instrument modules are designed to be installed,
removed, and serviced by ROV. They will snap and lock
into one of the module bays on the subsurface float. The
8
ACKNOWLEDGMENTS
capabilities. The PMACS server will communicate with the
SNC via an XML-RPC interface.
The shore server (SS) will run a dedicated process for
each sensor (an instrument server process). Each process
will interface to its respective sensor over the network and
archive the sensor data on the local disk. All sensor
configuration will be handled through the SS. The system
will also run the PMACS server process. The system
operator will be able to access the server remotely
(physcially residing at MBARI) to make changes to the
infrastructure and instrumentation, via the PMACS and
instrument server processes.
The network description is given in [26]. In total, there
are 36 IP addresses required. All of the switches (secondary
nodes and Digi-Connects on each SIIM board) can be
managed should MARS DCS have a need to do so. From the
point of view of the MARS PMACS and DCS, the AMM is
just another science user and must follow their procedures
with regards to setting current limits and starting/shuttingdown the mooring and managing the network.
There is currently no plan for an integrated observatory
control system (OCS) for the mooring sensor network.
Project personnel will perform this role, including
arbitration between different users on the AMM for power
and communications resources. This is likely to become a
problem only when more instrumentation is added to the
system (e.g., a near-surface winch system competing for
power).
Regarding data management and archiving, the system
is sufficiently flexible that the AMM data can be provided in
a suitable format. We will interface with the HOT DMAS
and live-action server at the University of Hawaii (R. Lukas,
[27]), and the RoadNet system at UCSD (F. Vernon, [28]).
This project is funded by the National Science
Foundation (NSF) Ocean Technology and Interdisciplinary
Coordination (OTIC) program, Grant OCE 0330082. The PI
is Bruce Howe at APL-UW; co-PIs are Roger Lukas at the
University of Hawaii and Emmanuel Boss at the University
of Maine.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
V. CONCLUDING REMARKS
8.
The development of the ALOHA-MARS Mooring is
on-going. The first full test will be in several months (spring
2006). Readers are encouraged to provide comments and
suggestions to the authors, and to visit the web sites [1, 25]
to keep abreast of the effort.
While there is some new development work (e.g., the
inductive power system), much of the project work and
effort is integration. Relative to what has been done before
this is quite a complex system.
There are many other related technical developments
that need to proceed for the vision of sensor networks to
evolve. Some of these topics are: improve profilers with
more power and payload, continue work on anti-biofouling,
address re-usability of components, improve the inductive
power system for general observatory use, drive the
inductive communications modem to higher rates, make use
of the precise timing in short range acoustic and seismic
experiments, quantify and improve reliability, develop an
observatory control system, interface a shallow winch
system on the subsurface float, develop energy storage
capability on mooring/seafloor to accommodate high peak
loads (and/or autonomous operation), add an acoustic
modem to the profiler and/or float and use for local
communications, mooring and mobile platform navigation,
and tomography with bottom transponders and remote
sources [29, 30].
9.
10.
11.
12.
13.
14.
9
ALOHA-MARS
Mooring
Project:
www.alohamooring.apl.washington.edu.
NEPTUNE Phase 1 Partners (University of
Washington, Woods Hole Oceanographic Institution,
Jet
Propulsion
Laboratory,
Pacific
Marine
Environmental Laboratory), Real-time, Long-term
Ocean and Earth Studies at the Scale of a Tectonic
Plate. NEPTUNE Feasibility Study (prepared for the
National Oceanographic Partnership Program),
University
of
Washington,
Seattle,
2000.
http://www.neptune.washington.edu.
B.M. Howe and T. McGinnis, “Sensor networks for
cabled ocean observatories,” Proceedings of the
Scientific Submarine Cable 2003 Workshop, 216–221,
University of Tokyo, 25-27 June 2003.
H.L. Clark, “New sea floor observatory networks in
support of ocean science research,” Proceedings of the
Oceans 2001 MTS/IEEE Conf., Honolulu, Hawaii,
November 5−8, 2001.
P. Brewer and T. Moore, Ocean Sciences at the New
Millenium, University Corporation for Atmospheric
Research,
2001,
152
pp.
(www.geo.nsf.gov/oce/ocepubs.htm).
K.L. Daly, R.H. Byrne, A.G. Dickson, S.M. Gallager,
M.J. Perry, and M.K. Tivey, “Chemical and biological
sensors for time-series research: Current status and new
directions,” Mar. Technol. Soc. J., vol. 38, pp. 121-143.
2004.
P.L. Donaghay, “Profiling systems for understanding
the dynamics and impacts of thin layers of harmful
algae in stratified coastal waters,” Proceedings of the 4th
Irish Marine Biotoxin Science Workshop, 44-53, 2004.
G.M. Purdy and D. Karl (eds), RECONN: Regional
Cabled Observatory Networks (of Networks). A report
to the National Science Foundation on the Cabled
Regional Observatory Workshop. http://www.geoprose.com/cabled_wksp/mtg_report.html, 2004, 64 pp.
Monterey Accelerated Research System (MARS):
http://www.mbari.org/mars/
ALOHA
Observatory:
http://kela.soest.hawaii.edu/ALOHA
B.M. Howe et al., SENSORS: ALOHA Observatory
Mooring and Adaptive Sampling, National Science
Foundation
funded
grant,
2003.
http://kela.soest.hawaii.edu/ALOHA/NSF_Mooring_Fa
stlane_20030306_Text.pdf,.
B.M. Howe, A.M. Baptista, J A. Barth, E.E. Davis, J.K.
Horne, S.K. Juniper, R.M. Letelier, S.E. Moore, J.D.
Parsons, D.R. Toomey, A.M. Tréhu, M.E. Torres, and
N.L. Penrose, Science Planning for the NEPTUNE
Regional Cabled Observatory in the Northeast Pacific
Ocean: Report of the NEPTUNE Pacific Northwest
Workshop, Portland State University, Portland, Oregon,
2003,
72
pp.
http://www.neptune.washington.edu/pub/workshops/PN
W_Workshop/ws_reports_documents.html
Ocean Research Interactive Observing Networks
(ORION): http://www.orionprogram.org.
K. Brink et al., Ocean Observatories Initiative Science
Plan,
2005,
posted
at
http://www.orionprogram.org/PDFs/OOI_Science_Plan
.pdf, 102 pp.
23. R. Detrick, D. Frye, J. Collins, J. Gobat, M.
Grosenbaugh, R. Petitt, A. Plueddeman, K. von der
Heydt, B. Wooding, J. Orcutt, J. Berger, R. Harriss, F.
Vernon, J. Halkyard, and E. Horton, DEOS Moored
Buoy Ocean Observatory Design Study, 2000, 97 pp.
24. J. Orcutt, A. Schultz, J. Bloxham, R. Butler, J. Collins,
R. Detrick, K. Ding, A. Dziewonski, G. Egbert, M.
McNutt, B. Romanowicz, S. Solomon, and M.
Zumberge, DEOS Global Working Group Report:
Moored Buoy Ocean Observatories, 1999, 42 pp.
25. ALOHA-MARS Mooring Software web site:
http://aloha.apl.washington.edu/wiki/index.php/Main_P
age
26. ALOHA-MARS
Mooring
Software,
network
description:
http://aloha.apl.washington.edu/wiki/index.php/Inwater_Network
27. Hawaii
Ocean
Time-series:
http://www.soest.hawaii.edu/HOT_WOCE.
28. Real-time Observatories applications Data management
NETwork (ROADNet): http://roadnet.ucsd.edu
29. Integrated Acoustics Systems for Ocean Observations
(IASOO): http://www.oce.uri.edu/ao/AOWEBPAGE
30. B.M. Howe and J. H. Miller, “Acoustic sensing for
ocean research,” Mar. Technol. Soc. J., vol. 38, 2004,
pp. 144–154.
15. Daly et al., An Interdisciplinary Ocean Observatory
Linking Ocean Dynamics, Climate, and Ecosystem
Response from Basin to Regional Scales, ORION RFA
Concept
proposal,
2005,
http://www.orionprogram.org/RFA/Abstracts/daly.html.
16. P.F. Worcester et al., Gyre-scale ocean heat content
and dynamics: Integral constraints from acoustic
remote sensing, ORION RFA Concept proposal, 2005,
http://www.orionprogram.org/RFA/Abstracts/worcester
.html.
17. Duda et al., Basin-scale float tracking and ocean
interior remote sensing, ORION RFA Concept
proposal,
2005,
http://www.orionprogram.org/RFA/Abstracts/duda.html
.
18. Barth et al., A Multi-Scale Ocean Observatory for
Ocean Dynamics and Ecosystem Response along the
Northeast
Pacific
Continental
Margin,
http://www.orionprogram.org/RFA/Abstracts/barth.htm
l.
19. Victoria Experimental Undersea System (VENUS):
http://www.venus.uvic.ca.
20. NEPTUNE Canada: http://www.neptunecanada.ca.
21. Power system development for cabled ocean
observatories, www.neptunepower.washington.edu.
22. C.P. Henze, Inductive Coupler Concepts for Coupling
1500W Across a Gap up to 15 mm Operating in Air or
Seawater, White Paper, Analog Power Design, Inc.,
Lakeville, MN, 2002.
10