Transcript CUA Hovercraft

ME 442 Senior Project
Autonomous Hovercraft – Class of 2008-2009
Project Summary
4/30/09
Joseph Cochrane, Patrick Dickey, Aldo Glean, James McMahon,
Omar Monterrubio, Kalin Petersen, Jason Shao
Post-Conflict Mine Fields
• Unexploded landmines from
previous military conflicts are still a
prevalent issue in civilian 3rd world
areas
• Estimated 1 million unexploded
landmines left over from a skirmish
between Israel and Lebanon in 2006
• Cambodia has one amputee for
every 290 people - one of the highest
ratios in the world.
Landmines
• Anti-personnel landmines are generally small and
designed to maim, not kill
• Most anti-personnel landmines are detonated when
about 5psi of contact pressure is applied to a triggering
mechanism on the device
• Can be triggered via a person stepping on device,
driving over device, increased pressure or vibration
Why a Hovercraft?
• Is a vehicle that uses an engine to drive a large fan
inside a structure, which creates an air cushion within
a fabric skirt
• Provides lift force to counteract the weight of the craft
while applying very little pressure to the surface
beneath, ~0.1psi
• Capable of traveling over solid, marshy and wet
terrains, making it adaptable to the various rural
environments
Our Concept
• We intend to develop a means for civilian landmine location that is inexpensive and easily
reparable
• Our intention is to design the platform for
carrying detection technology, not develop the
technology itself
Presentation Outline
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ME 441 summary
Ground Penetrating Radar (GPR)
Lift engine mount
Lift engine shroud
Pressure testing
Pulley attachment
Propulsion and electronics power systems
Thruster housing mesh and design testing
Component layout and balance analysis
Controls
ME 441 Summary
• A larger hull was designed to accommodate the
Ground Penetrating Radar antennae and the various
system components
• Air flow and lift calculations performed
• New hull and skirt constructed and tested
• Lift engine acquired
• Lift fan selected and acquired
• Thruster housing design modified and four units
constructed
Ground Penetrating Radar
• Penetradar GPR system outfitted with IRIS
processing software provided by U.S. Army
Night Vision Directorate
• Test designed to observe its detection
capabilities
Navigation System
• Acquired differential GPS components (~3cm
resolution) from U.S. Army Night Vision
Directorate
• Will allow position and direction of the craft to
be monitored from a remote location
Pressure Testing
• Verification of lift and air
flow calculations
• Used differential pressure
transducer to measure
static pressure inside the
hull
• Average pressure
measured was 0.16psi
• Predicted value was
0.19psi
• ~16% difference
Lift Engine Mount
• Design objectives:
– Maximize space efficiency
– Support and restrain lift
engine while in operation
• Initial testing revealed
significant vibration of
engine, indicating
deformation of the mount
and potential fatigue failure
Lift Engine Mount
• Additional element was added to bolster the
engine’s supporting members and to reduce
stress and resulting deformation
Lift Engine Shroud
• A shroud was designed and tested to protect
lift fan and people working around the craft
• Able to withstand a person falling against it
• Provides sufficient barrier between fingers and
moving components
• Restricts large debris from encountering lift fan
Overall Power Systems
Flow diagram for power systems
Propulsion Power System
• Propulsion system requires 29.6 – 37V voltage
supply
• Three 12V deep-cycle marine batteries in series
provide necessary voltage
• 32V alternator donated by Prestolite Electric
used to charge battery bank (charges at 38.5V)
Electronics Power System
• GPR computer requires a 110-120V supply
voltage
• 12V battery connected to self-exciting 12V
alternator connected to 110-120V power
inverter
Pulley Attachment
• Connection required between lift
engine and lift fan
• Power systems design required
alternators to be driven by lift
engine
• Fabricated part and completed
analysis
Thruster Testing
• Pendulum apparatus allowed testing of various
thrust system parameters:
• Motors
• Propellers
• Housing mesh
configurations
Thruster Housing Mesh Tests
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Housings would restrict air flow and thrust force
Modified mesh improved results
Both meshes required for safety parameters
Maximum force of ~15.67lbf
Mesh Configuration
(with full housing)
Average Thrust
Force Loss
(as compared to
unhoused propeller)
Front and rear mesh
37.1%
Rear mesh only
18.1%
Front mesh only
23.7%
Modified front mesh only
13.0%
Modified both front and rear
meshes
16.2%
Motor Stand Strength Test
• Basic design of motor stand
modified
• Maximum force produced by motor
with housing is 15.67lbf
• Test performed by applying ~35lb
force to stand with force gauge for
30 seconds
• No sign of deformation observed,
therefore stand has at least a safety
factor of 2
Component Layout and
Balance Analysis
• Components need to be arranged to minimize air
flow impedance to thrusters and maximize
balance of craft
• Used modeling software to arrange layout and
assign component weights and calculate center of
mass
Component Layout and
Balance Analysis
• Thrusters arranged to
maximize forward and
backward response
• Turning capability increased
by placing center thrusters
closer to outer units
• ~1ft of free space arranged
between thruster units and
other equipment, so air flow
would not be obstructed
Computer
• Single computer to operate controls, navigation
system, and GPR for functionality
• Will utilize remote desktop so that systems can
be operated from a removed location
Controls
Requirements:
-Control from external location
-Move with 2DOF
-Easily operable interface
Constraints:
-Cost
-Must use computer already on
craft
-4 Simultaneous motors
-Signal must be a PWM square
wave
Controls
Laptop via remote desktop
PC w/ GUI
Microcontroller
Electric Motors
Controls
Direction of airflow
Controls
Direction of airflow
Controls
Direction of airflow
Controls
Direction of airflow
Conclusions
• We produced a hovering craft that is capable of:
• Carrying required lift and power components in
addition to navigation and detection equipment
• Supplying power to the propulsion and electronics
systems
Conclusions
• Tests were completed on each subsystem, for instance
the propulsion system in which each unit is able to
produce ~15.5lb of thrust force
• Controls, Ground Penetrating Radar and navigation
systems need to be refined further
• A basic integrated test has been completed with all of
the various systems
Questions?
For more information:
http://students.cua.edu/51mcmahon/