Power Control Circuit:
Power control for the Kraken is configured on one single fully developed power
board that was custom made for this project. It contains separate motor power and
computer/sensor power circuits, reducing the risk of motor power spikes affecting
semiconductor components. Both circuit are powered by lithium polymer batteries.
The current from each battery is first filtered by an electrolytic capacitor and a
high-speed, 30- volt, 1500 W transient voltage suppressor. The filtered motor power is
sent directly to the H-bridges while the computing power goes through a 2- mp, DC-DC
9 V switching regulator. The off-the-shelf components are mounted using point-to-point
connections on perfboard.
Computer Power Circuit:
The Kraken has a modular computer power circuit. Power is fed from the lithium packs through a voltage regulator that maintains a 12 V power output with a variable input of 10-36 V with a maximum of 2 Amps. Power passes from the computing/sensorsbattery through the power distribution board to the Arduino Mega, motor controllers, sonar system, pressure sensor, and the torpedo launching circuit. Power going to the pressure sensor comes from the 9 V regulator.
Motor Control Circuit:
San Diego City Robotics design engineers aimed for a fully modular and
replaceable motor control and power circuit as it is the most likely to develop overloads
due to concept and design testing. Every part of the motor control circuit comes from off
the shelf parts making replacements readily accessible and easy to obtain. Power
passes from the motor battery through the power distribution board to the H-bridges
here it is modulated by the PWM signal from the Arduino Mega microcontroller and then
sent to each of the six motors.
A PWM signal is sent from the Arduino Mega microcontroller to an H-bridge
connected to the motor battery which outputs the amplified signal directly to the motors.
The H-bridge allows the motor to provide bi-directional thrust.
¬†Electronic Components – We utilize the following components in our AUV.
¬†The Kraken uses 2 Seabotix brushed thrusters, as well as 4 water-cooled motors which are modified bilge pumps. The bilge pump motors¬† are completely ¬†waterproof and provide high power-to-weight ratios as they are both more powerful and more efficient.er-cooled motors which are modified bilge pumps. The bilge pump motors¬† are completely ¬†waterproof and provide high power-to-weight ratios as they are both more powerful and more efficient.
¬†Each motor is mounted within a PVC housing with aluminum grate for safety.Six ¬†thrusters are used to provide the most control and precision across all three axis‚Äôs. The dive motors controlling movement along the z-axis allow for control of altitude. The Seabotix drive motors that control¬† position on the x-axis and the strafing motors that control the y-axis ¬†provide the fine control needed when tracking the SONAR pinger or surveying the buoys. The six thruster design gives the Kraken the robust and precise control it needs to successfully navigate uncertain environments.
The FIT-PC2 is an Intel Atom Z530 Linux based computer with 1 GB of RAM. As the main data processing component of our computing system, it is responsible for running the Kraken‚Äôs mission control software. It collects information from the cameras the sonar and the pressure sensor. This information is then processed and commands are sent to the Arduino. It allows for data logging on board the AUV and can connect to
a wireless tether for remote debugging. The Fit PC gives us a much more flexible platform to program off of. While this is much heavier than the microcontrollers we’ve utilized in the past, we believe the trade off in weight for easy of programming will pay off in the overall effectiveness of our AUV.
Arduino MEGA 2560
The standard Arduino Mega used in 2011 was upgraded to an Arduino Mega
2560 multi-controller. The 2560 doubles the Kraken’s program space as well as the
memory available to NavBox, increasing the processing capacity and allows for a more
robust program to run the Kraken. The Arduino Mega reads the current heading and
depth information provided by the IMU. It then determines the appropriate speed and
heading of the Kraken, and sends signals to the motor controllers.
In conjunction with Professor Pruitt of San Diego City College a viable sonar
option was manufactured. The Hydrophone Array consists of (4) custom fabricated
piezoelectric elements that are potted and mounted into an anodized aluminum
adjustable scan angle frame. This array faces forward on a plane tilted downward at 45
degrees. Two hydrophones across the top of the array detect horizontal displacement,
and a third placed below these is paired with one of the upper hydrophones to detect
vertical pinger position. The immense design challenges included pinger level variation
with location, unwanted pinger frequencies, echoes from the pinger signal, and the
mathematical complexity of converting arrival times to pinger heading angles, requiring
the San Diego City Robotics electrical team to engineer several inventive solutions.
FIG 2 Microprocessor / LED Circuit
Hydrophone Array – This is a unique piece of hardware that we have donated to us.¬† It features 4 recievers suspended in ballistics gel.¬† The signal is first processed and then sent to the Fit-PC.
Cameras – These take pictures for the AUV to analyze in order to complete obstacles and such with the aid of our Vision code.