Nonlinear Dynamics and Control Lab

Aeronautics and Astronautics
University of Washington

HOME
PEOPLE
RESEARCH
COURSES
PUBLICATIONS
LINKS
CONTACT INFO

Fin Actuated Autonomous Underwater Vehicle

The multivehicle underwater testbed in the Nonlinear Dynamics and Control Lab consists of three fin-actuated untethered autonomous vehicles.  The current vehicles are the second generation built in our lab.     Each vehicle contains a microprocessor to collect sensor data, to handle communication with other vehicles, and to determine control commands to the servos.  Each robot is equipped with an RC receiver.  In small spaces such as the tank in our lab, or caves and littoral zones, noise in acoustic communication becomes prohibitive.  In the case of our tank, RC communication has been demonstrated to be effective.  Onboard programming can be used to allow the RC system to emulate the acoustic system.

The robots are each powered by four servos. Two are located in the rear of the robot and power the two links of the tail assembly. The other two servos control the motion of the forward fins; their motion is fully independent of one another. To be able to orient itself, the robot has a depth gauge (a pressure sensor) and a 3-D magnetic compass.  The fish is tuned to be neutrally buoyant; that is, when placed at some depth, it will neither float nor sink. Due to pressure changes and compression/decompression resulting in volume changes of the vehicle, the buoyancy is not constant. A current device under development is a buoyancy tuner to adjust buoyancy as the robot moves to different depths.

For purposes of development and testing, an instrumented tank has been built in the lab.  The tank is an above-ground swimming pool 8ft deep, 8ft wide and 20ft long.  Underwater cameras connected to an external computer provide the ability to track the vehicles in the water in real time.  This data is processed for 3D position information and transmitted via RC broadcast to all vehicles in the tank.  The broadcast information contains vehicle identification codes and can also include information for simulated vehicles to provide a group effectively much larger than the existing three vehicles.

VIDEO GALLERY

Videos of the first two prototypes in action are below. Movies are in wmv or avi format. Note that our server has some issues with wmv files. If the video will not stream correctly, please right click and save the video to your computer. We apologize for the inconvenience.

Robofish 1.0 & 2.0 (wmv)

·  Robofish 2.0:Heading and Depth Control

·  Robofish 2.0: Depth Control in the new indoor tank.

·  Robofish 1.0 & 2.0: Heading Control in the outdoor pool.

·  Robofish 1.0: Pectoral Dolphin movement in the outdoor pool.

If the wmv files above are not compatible with your operating system, there are some avi and mpg encoded raw footage files below:

Robofish 2.0 (avi)

·  Robofish 2.0, Depth Heading (13Mb avi)

·  Robofish 2.0, Heading and Depth Control (6.7Mb avi)

Robofish 1.0 (avi/mpg)

·  Robofish 1.0, Depth Heading (21Mb avi)

·  Pectoral Dolphin Locomotion (16Mb avi)

·  Pectoral-Kick (15Mb avi)

·  Pectoral-Wave (12Mb avi)

·  Robofish 1.0 Depth Control (16M mpg)

PHOTO GALLERY

Click on the thumbnails for a larger view.  Pop-up blocking software may interfere with this page.  If clicking on a thumbnail does not pop up a high resolution photo, turn off the blocking software and try again.

RoboFish 2.0 Side View.  Note the red acoustic modem on the top of the robot.

RoboFish 1.0.  This version is not as hydrodynamic as version 2.0 and has carbon fiber side panels rather than aluminum.

Another view.  The servo drive train assembly is clearly visible.

Side view of the robot.  Note the external on/off switch on the side of the robot.  The external rocker switch has now been changed to a magnetic switch.

The original prototype had carbon fiber fins and panels.  The second robot used acrylic panels and Styrofoam/fiberglass fins for greater stiffness, providing more consistent buoyancy.

Rear view of version 2.0.  The metal components are aluminum to withstand corrosion.

View of the inside of the robot.  The side panels are removable for easy access to electronics.

Top view.  A dime is shown for scale.  Note the two-bar linkage tail assembly.  Each link is independently powered by a servo.

Another view of the electronics.  The large coaxial cable is used for the modem transmissions.

Here the electronics are being removed.  Note the O-ring along the side of the fish.  The removable side panel increases the accessibility of the electronics compared to the first prototype.

Last updated on: Wednesday, July 23, 2008 14:22. Send questions or comments to morgansen@aa.washington.edu.