Two of the scientists working with the boat via Wi-Fi on the
dockside laptop. The hatch is open revealing the battery.
The Mini ITX controls the other controllers which
actuate the boat and process information from the science
The actuation system that controls each boat includes
dual bi-directional thrusters which a Roboteq AX1500
two-channel motor controller manages. The controller
translates commands from the Mini ITX into high currents
and voltages that drive the two DC motors.
Actuation equipment also includes a rudder which a
servo motor controls, which a serial-servo controller
manipulates. In addition, each boat has a motorized winch
that enables it to lower and raise an underwater sensor
down to a depth of 25 meters.
Sensors on the boat include those used for gathering
scientific data from the water and surrounding elements,
and those used to provide information for navigation. The
navigation instruments include an Inertial Measurement
Unit (IMU), a GPS, and a Dynamic Measurement Unit
The IMU is a Microstrain DMG. The DMG uses angular
rate gyros to determine its orientation. It communicates
with the rest of the system via its RS-485 protocol. The GPS
is a uBlox unit. It provides the system with a latitudinal and
longitudinal position of the ASV.
The boats require all these navigation instruments in
order to get an exact location. The GPS alone is not
accurate enough, especially when the boats need to
maintain their position at a single waypoint for sampling.
To make the location estimates more accurate, the
boats use the IMU — a three-axis accelerometer to provide
the boat’s surge, heave, and sway measurements, which
USC scientists Professor Gaurav S. Sukhatme (right)
and Jnaneshwar Das pose with the water chemistry
sensor and laptop, dockside.
are the x, y, and z axis. The rate gyros provide information
about rotational rates and angular velocities, or in other
words, roll, pitch, and yaw. (yaw is the boat’s heading.)
The ASV uses a Kalman filter to bring all the data from
the different navigation sensors together. Finally, the Mini
ITX uses algorithms to output the craft’s location with
greater accuracy. The Mini ITX uses this data to take
corrective action to maintain course or to hold station.
Scientific sensor equipment includes a wind speed and
direction sensor, a bathymetric profiling sensor, and a water
chemistry sensor. The wind speed and direction sensor,
(made by TWI) compiles weather information. Imaginex
makes the bathymetry profiling sonar. It uses sound to
sense the sea bottom to map out its shape.
The water chemistry sensor is a Hydrolab MiniSonde
MS- 5. A winch lowers the sensor to test the water at
different depths. The MS- 5 measures things like algae,
chlorophyll, oxygen content, the degree of contents of
other elements, pH balance, temperature, and turbidity.
The boat’s shell is an adapted Q-Boat with dimensions
of seven feet in length, two and one third feet in width and
The front of the boat.
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