Latis II Underwater Remotely Operated Vehicle Technical Report

ROV ELECTRONICS
MAIN CONTROLLER
At the heart of Latis II is a National Instruments
Compact RIO controller (cRio). The cRio is most
commonly used for data acquisition and
automation control. The cRio on Latis II has
slots for four drop-in modules, of which three
are used. The team used two 9401 Digital
Input/ Output modules, as well as a 9205
Analog Input module. These modules are used
to link the cRio processor to its environment
through sensors and output devices.
THRUSTERS
Six BTD-150 Seabotix thrusters are used on Latis
II for propulsion. Three Sabertooth 2x10
electronic speed controllers are used to
regulate thruster power. Each Sabertooth
controls two thrusters.
SERVOS
The motion of each arm joint is provided by a
small hobby servo. Eight HS-7775MG Hitec
servos are used for the shoulders, elbows, and
grippers. Two HS-805BB Hitec servos are used
for the shoulder rotation joint. All of the servos
connect back to custom circuit boards in the
main enclosure for control and power signals.
SENSORS
To provide feedback on internal and external
conditions, Latis II is equipped with a variety of
sensors.
4
� Phidgets Temperature and Humidity
Sensor Board to measure thermal
conditions inside the ROV enclosure
� OMEGA Thermistor for measuring
external water temperature
� H1a Aquarian Audio Hydrophone for
measuring external sound sources
LATIS II
TECHNICAL REPORT
CUSTOM CIRCUIT BOARDS
To make it easier to interface to the cRio
modules, three custom printed circuit boards
(PCBs) were designed and manufactured. Each
PCB connects to its cRio module through a
ribbon cable, and connects to various devices
through three-conductor cables commonly
found in radio-control hobby electronics.
THRUSTER BOARD
The Thruster Board breaks six digital output
channels from a 9401 module on the cRio into
three-pin headers for the Sabertooth units to
plug into. The remaining two channels are used
to control the gripper servos. Each servo pulls
power from the 5V supply through a PCBmounted
3A fuse.
Figure 1: Thruster PWM Board
To work with this PCB, the 9401 module on the
cRio is configured for pulse-width-modulation
(PWM) output. Each channel produces a square
wave with a duty cycle proportional to the
desired speed.
A resistor-capacitor (RC) circuit is used to filter
the pulse with modulation (PWM) signal into an
analog signal for the Sabertooth. The servos
require an actual PWM signal, so no filtering
circuit is used.