Four power control
boards convert the input voltage to levels required by the computer and
sensors. The first converts to five
volts, which powers the computer and other three power control boards;
output 12, 15 and 12 volts respectively.
The power control boards were designed for the profiler and run
software written in C to perform the appropriate switching and
To allow monitoring of various system status
power control board that outputs 5 volts functions as a "watchdog"
that also monitors pressure, range and time, and will release the
weights in case the logger fails to terminate the dive appropriately. A dive would be terminated if a low voltage
condition is detected, or the logger program stops running or if the
data from the CTD is bad.
The profiler's main computer is a low power 200Mhz 386 PC104 with an 8-port serial card and a 16-bit A/D converter card. PC104 is a form standard widely used for small computers, so replacement parts should be available in the years to come. The computer gets power directly from the power control board that outputs five volts, since the operation of the main computer is mission critical.
The photograph shows the PC104 computer stack (right), A/D filters (center), and power control boards (left) used in HRP-II.
The autonomous operation of the HRP-II is
“logger” software written in C running on Windows 2000.
The logger program was developed using
National Instruments CVI software tools, which supplies functions to
everything from the Graphical User Interface (GUI) to the serial and
The logger program is the primary brain of the profiler. It was designed to allow easy reconfiguration of the sensors employed. Any sensor may be used or de-selected prior to each dive by clicking a button on the GUI interface. Adding or replacing sensors is enabled by modifying the sensor connectivity table to include the new sensor id, port or channel, baud rate, gain, and power switch setting. An example of this table (called att_tab.asc) showing the configuration used on the test cruise is listed here
The logger is also
responsible for dive configuration, sensor control, simultaneous
and logging of data from the configured sensors (in this case: five
serial sensors and 10 A/D channels) during descent, along
real-time monitoring of pressure, range and time as potential dive
termination criteria. All data is stored
during the downcast and written to disk at the end of the profile after
weights are released to eliminate any vibrations resulting from disk
activity. Data logging on the upcast is possible,
but hasn't been used yet.
The protocol used for communications between the logger program on the PC104 stack and the Watchdog and power control boards is RS485, which allows two-way communication shared among multiple nodes. Our method is based on the logger program (controller) being the main talker, with the power control boards listening for whether the message applies to them, then acting accordingly- this block diagram shows the general scheme we used. The Rottweiler protocol is not documented on the web.
A variety of sensors used to measure the smallest to the largest scales of mixing in the ocean were chosen for use on HRP-II. The underwater movement from the GPS data determines the largest scales, and the shear probes the smallest. Five sensors output ASCII serial data for logging, and ten sensors are connected to the A/D converter and logged as binary data. The data from each sensor is logged in a separate file. The synchronization of data from the files is obtained by powering up the configured sensors well before the start of logging, so data is streaming from the sensors well before the logger starts saving the data. Simultaneity of logging start has been verified in bench tests in the lab. Time words embedded in several of the data streams is further used to quantify drift of the various clocks.
A list of the sensors and their manufacturers is detailed here. The configuration of the sensors used on the test cruise with the port and power control connections are also described. A short description of each sensor is provided below.
Acoustic current meter (ACM):
In the HRP-II, X is defined as “up” when the
internal electronics chassis is horizontal as used in bench
Internally, North on the compass is aligned to X by how the electronics
are attached to the chassis. The
accelerometers are rigidly mounted in
pairs, with one 90°
from the other.
One pair is bolted to the bottom end cap, and the other to the
The bolt hole positions ensure that one accellerometer of each pair is
aligned with X. The ACM transducer sting
had to be
installed at a
known offset of 22.5°
to HRP-II X because of space limitations on the end cap, and to keep
the transducer arms from interfering with the release weights and the
The electronics chassis (and
sensors attached to the lower endcap) is always installed in the same
relative to the body, which allows sensors mounted on the upper endcap
to be aligned with the rest. In the photo, HRP-II is in it's
allow access to the weight dropper doors which puts
+X pointing down and right as viewed from the bottom. Since the
upper end cap is hidden by the skin, a schematic was
drawn to show what it would look like when viewed from the top.
appears to be pointing the wrong way, but think about a mirror image,
and you realize the drawing is correct. The
collar supporting the EF
not be secured rigidly to the body due to noise issues, so it floats. However, efforts were made to ensure that EF-1
remained aligned with the instrument X.
The raw acoustic travel times were used to compute U & V velocities
relative to the sting,
which were then rotated by 22.5° to obtain X & Y velocities
corresponding to the accellerometer and EF sensor data.
During the test cruise, the sensors were aligned as follows:
with X: accelerometers 2 (top) and 4 (bottom), EF 1 and compass N
with Y: accelerometers 1 (top) and 3 (bottom), EF 2 and compass E
The body of the HRP-II is the structure that
protects the sensors and electronics during operation.
The body consists of five major parts:
electronics pressure case, the support and integration elements
lifting bail and skin), the floatation, the battery packs, and the
releases. The dimensions of
the vehicle, along with the major structural elements are shown at the left.
housing was made of 8” internal
diameter, 1" wall 7075-T6 aluminum tube, anodized to prevent corrosion. The endcaps were fabricated of the same
material. The largish diameter was dictated
partially by the size of the electronics, and partially to allow a big
enough endcap (10") for all the sensors to fit without interfering with
The dimensions and materials were also selected to
minimize vibrational noise, and facilitate quiet data
measurement. Titanium rods and a truss connect the pressure
housing through the buoyancy element to the lifting bail at the
top, assuring a "stiff" body.
The amount of syntactic foam attached at the top controls the rates of vehicle descent and ascent. The desired nominal descent rate is 0.6m/s, which was achieved as drawn, after the addition of ~30 lbs of lead shot attached near the lower endcap.
The skin was fabricated from two cylinders of
polypropylene. By minimizing the number
of seams the frictional effects on body motion were decreased. The collar holding the two EF sensors is
mounted mid-body between the two cylinders.
Power is supplied to the controller and sensors from two battery packs mounted between the pressure housing and the skin. Each pack can supply adequate power for operations independently. The solenoids that function to release the descent weights are also housed under the skin, but outside the pressure case.
Inside the pressure
case, a chassis supports the
power control and filter boards, , as well as the electronics for the
MAVS, compass, EF sensors, altimeter and
pinger. Electrical noise
was minimized by physical separation and internal partitions separating
the sub-systems. The chassis
layout with some of the electronics installed is shown in the photo at
the right. The lower endcap (where the CTD and ACM stings will
eventually be attached) is at the left edge of the picture.