here - EDGE

Underwater Robotic Fish
Phase III: Obstacle Avoidance and Navigation P16229
Project Summary
The Robofish is an aquatic robot that mimics the
locomotion of an actual fish. It is designed to utilize
McKibben Muscles to actuate a tail that provides
horizontal propulsion. By employing both image
processing and ultrasonic ranging, Robofish is able to
detect obstacles and determine how to best avoid a
collision while autonomously moving through the
water. In addition, Robofish is equipped with a
buoyancy system, as well as the capability to detect an
object falling through the water and intercept it. The
current incarnation of Robofish builds on the previous
two designs from P14029 and P15029, employing a
more powerful pump and more robust tail.
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Team Members (Left to Right): Nicholas Gulati (BME), Khalfan Alzaabi (ME),
Jon Nguyen (EE), Ryan Selby (EE), Matthew Yap (ME), Corey Muench (EE)
McKibben Muscle
The main component behind Robofish’s
locomotion
Transmits pressure into a contraction
and corresponding applied force.
The force generated by the McKibben
Muscle, as well as the percent total
length change experienced by it are
directly related to the pressure provided
to the muscle
The pictures below depict a McKibben Muscle in a relaxed (top)
and a pressurized (bottom) state.
Electrical Systems
Robofish relies on a combination of PCB boards, an
Arduino, and a Raspberry Pi to provide instruction
and communication between its various
subsystems.
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Depicted above is an all-encompassing schematic of the Robofish electrical system. This
schematic includes the microcontrollers, gate drive circuits, interface circuits, battery pack,
boost converter, camera, pressure sensor, jaw sensor, water detection, valves, and pump.
Below is a picture of the PCB Boards
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Mechanical/Structural Systems
The main mechanical system of concern for P16229 is the tail, which provides horizontal propulsion to
the fish. Shown above is a schematic that illustrates the motion through which the tail cycles in order
to produce horizontal motion. The tail, which is powered by McKibben muscles, transforms the linear
force and displacement produced by the muscles into torque and angular displacement. This is
accomplished by tethering a pair of McKibben muscles to pulleys that act as the hinge points of the
tail segments, and guiding the lines such that the linear contraction of the muscle torques the pulleys.
Solenoid
Valve
Tether Line
Attachment
Point
Line Guides
McKibben Muscle
Robofish uses a system that detects and tracks color
as it travels across a 4 quadrant observation
window. Depending on the position of the tracked
pixels, Robofish decides in which direction to move
to avoid collisions with the observed object. This
same system is used to detect objects which
Robofish will retrieve. Robofish is programmed
with a variety of swimming algorithms that allow it
to maneuver, rise, and sink in the water.
The McKibben muscles are supplied with hydraulic pressure by a 100psi pump housed within the body
of Robofish. Three way solenoid valves are used to activate muscles during locomotion, and allow for
the muscles to passively drain as they return to their relaxed state.
The lines used to tether the pulleys to the muscles are 20lb braided fishing line. This type of line was
chosen both because of its strength and its ability to resist elongation by creep and when exposed to
wet conditions.
Depicted to the left is the battery
and electrical systems box of
Robofish. This waterproof box
contains the PCB’s, Arduino, and
Raspberry Pi that make the
Robofish function.
This box also contains enough
batteries to power Robofish for
almost 6 hours of continuous
operation in the water.
Acknowledgments
Special Thanks
Dr. Kathleen Lamkin-Kennard and Art North
Mark Schiesser and Triline Automation
Dr. Gomes, Prof. Slack
Previous Teams: P15029 and P14029
By attaching the muscles directly
to the tail segments, instead of
housing the muscles in the body,
this Robofish mitigates some of
the issues that previous tail
designs had with the tensioning
of the tethering lines. Also, by
utilizing pulleys, the design
reduces the amount of
contraction length required for
the muscles to actuate the tail.