ME 442 Senior ProjectAutonomous Hovercraft – Class of 2008-2009

Joseph Cochrane, Patrick Dickey, Aldo Glean, James McMahon,

Omar Monterrubio, Kalin Petersen, Jason Shao

Project Summary4/30/09

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 land-mine location that is inexpensive and easily reparable

• Our intention is to design the platform for carrying detection technology, not develop the technology itself

• 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

Presentation Outline

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 SystemsFlow 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• 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

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

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

For more information:http://students.cua.edu/51mcmahon/

Questions?