group 15 phase iv report

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Stevens Institute of TechnologyCastle Point on Hudson

Hoboken, NJ 07030ME-424 Senior Design

Phase IV Report

Unmanned Chopper

Advisor: M.G. Prasad

Group 15 Members:

Christopher Alexander

Brandon MacWhinnie

Michael Manzione

Sonal Pujji

Juan Rodriguez

Date 2/14/2008

I pledge my Honor that I have abided by the Stevens Honor System.

_____________________ _____________________ _____________________

_____________________ _____________________


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I. Abstract

The purpose of this senior project is to design and fabricate an unmanned aerial

vehicle. This report will serve as a means to illustrate the progression of the project fromthe design stage to the fabrication stage. In this report the group will focus on outlining

the objectives we plan to achieve this semester and will address the comments fromPhase III, as well as discuss the final design of the product. This report will analyze thepurpose of prototyping and manufacturability of our chosen design. It will provide a

platform with which to move through the prototyping and performance testing phase of

the project.


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Table of Contents

I. Abstract iII. Project Objectives 1III. Phase III Issues 1IV. Design Finalization .. 3V. Prototype Justification . 4VI. Prototype Manufacturability 5VII. Prototype Testing . 7VIII. Conclusion 8IX. References .... 9X. Appendix

i. Gantt Chartii. Bill of Materials

iii. Nugget Chart


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II. Project Objectives

In order to gain knowledge of enemy terrain surveillance and reconnaissance

missions must be completed. The United States Army has always conducted thesemissions using mostly human power. Recently, automated robots and all-terrain

vehicles have been in use. For our senior design project we wish to add anotherdimension to reconnaissance and surveillance which the military can utilize. Weintend to design and fabricate an unmanned aerial vehicle to conduct surveillance

missions

Designing an aerial surveillance vehicle will allow many more aspect of theterrain to be analyzed, as opposed to ground vehicles. The aerial vehicle we intend to

design will be a helicopter. The group will be modifying designs of current products,

as well as introducing new aspects in the design. Although there are many unmannedvehicles in existence, we wish to create a smaller, faster, lightweight helicopter which

can send real-time video back to its home base. These videos will then be able to be

analyzed and a safe plan of attack can be generated. At this time, the main focus ofthe project will be demonstrating the ability of the design we have created. We hope

to pursue the video option at a later time.

The helicopter will be able to be deployed and operated by a single person,which will ultimately assist troops entering enemy territory. The main focus is to

create a product which the armed forces can use to survey enemy territory. A low

manufacture price would be ideal, however, safety and the life of the chopper is themain focus.

The group aims to market this product to United States Armed Forces and other

government agencies, such as the Border Patrol. Using an unmanned helicopter to

gather information removes the chance of a person being injured or even killed inhostile environment. The groups final product will be targeted toward the armed

forces as the primary customer, with government agencies, and law enforcement

agencies as secondary customers. The versatility of the vehicle will allow it to beused in combat, in a search and rescue mission, or even to follow the presidential

motorcade. It can even be the first to document a compromised crime scene.

A plethora of engineering subjects will be utilized in the completion of thisproject. For the mechanical engineering aspect, aerodynamics and material selection

are two extremely important topics. Electrical engineering will also play an important

role in the incorporation of the real-time video camera.

III. Phase III Issues

The first and foremost concern of the panel at the end of Phase III was the flight

capability of the vehicle. Since the UAV has an unconventional design there are few

precedents to provide an example of how to produce lift and achieve successfulmaneuvering. This issue was the most often mentioned aspect of the design. Many of


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the panel members were unsure of the maneuverability of the vehicle and how it wasto be achieved through the design. The panel also suggested limiting the scope of the

vehicles uses, as it is unnecessary to the design and presupposes too much of the

final product.

The scope of the project was initially too large, and it was suggested thatexploring the surveillance capabilities of the vehicle be postponed until a successfultest flight was conducted. As a result, the design was simplified and would carry less

electronics. The majority of the groups focus was spent on the design of the vehicle

with controlled flight being paramount. Initially, a video camera was going to be

equipped to allow remote viewing from the vehicles point of view. However, aftertaking into account the comments and guidance of the panel, the camera was

tentatively removed from the design. It was not incorporated directly in the design

during the first phases of the project. However, that being said, the camera is stillimportant to the group and should the group have extra time after demonstrating a

successful prototype, the camera will be added to the vehicle.

A more specific scenario was also proposed by the panel. Initially, the aircraft

was to provide surveillance inside and outside of a building. The vehicle would be

small enough to fly through doorways, yet powerful enough to resist wind gusts and

the elements of being outside. However, after consideration of the panels comments,the design needed to be limited. Since there exist a few larger vehicles of similar

characteristics, such as the USAF Predator and Sikorskys Cypher, the decision was

made to specialize the vehicle to indoor uses. Indoor use would simplify the designby having more uniform and favorable flying conditions. The aircraft would not have

to withstand buffeting winds. Also, indoor flight would limit the aircrafts overallchassis size, and building a smaller aerial vehicle was important to the group.

The main concern of the panel was the vehicles maneuverability and flightcharacteristics. The design is unconventional and is not particularly intuitive.

Additionally, the group was weighing a few options on how to tackle steering the

aircraft. However, at the end of the design phase, the group had selected a steeringsystem to easily control the vehicle.

The vehicle steering seems daunting because of its coaxial dual rotor design;

however it consists of simple and tested mechanisms. The coaxial design was chosento reduce the footprint of the aircraft which would make it small and portable.

Maneuverability would also increase with a smaller more nimble chassis. Despite

these benefits, very few full size helicopters use a coaxial design. A coaxial helicopterrequires more complex gearing to power two main rotors with one engine. Coaxial

helicopters also require more power to move two sets of main rotors through the air.


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IV. Design Finalization

The final design employs two electric motors, which do not require complicated

gearing. The two motors would also provide sufficient power to the rotors to achievelift. The drawback of dual motors and rotors is additional weight, but calculations

have showed that enough thrust would be produced to lift the estimated weight of thevehicle. The engines that will power the unmanned aerial vehicle have been selectedto be Great Planes Rimfire 28-30-1450 Outrunner Brushless motors.

Steering will be achieved by actuating the top rotor assembly in the same way a

helicopter steers. The group decided to actuate only the top rotor set to simplify thedesign and reduce added weight. Actuating the bottom rotor assembly may also create

unstable flight by pushing out the bottom of the aircraft. This is very similar to the

systems used in small radio controlled helicopters. In such coaxial R/C helicopters,the bottom rotor set is actuated with a swash plate to simplify the design, as the

helicopter body remains below both sets of rotors. Since the chosen design has a

centrally mounted body, the top rotor could just as easily be actuated. As seen in theR/C helicopters, flight is stable and in some aspects easier to control. Coaxial rotors

where only one rotor set is actuated result in less maneuverable aircraft. However, all

necessary motions are able to be performed, just not to the extremes of a single rotor

set up because of rotor interaction and clashing. The final design has the rotors spreadfar apart vertically to reduce potential clashing and will not tilt far enough to pose a

problem. The limited rotor head tilt will decrease the translational (forward-

backwards, left-right) flight speed, but still provide movement in all directions. Theslower flight speed can reduce possible crashes and decrease the time it takes to

master the controls.

Finally, flight will be stabilized by the design of the chassis. As with all

researched helicopters the weight of the chassis is suspended below the rotors toprovide stable flight. Rather than trying to balance the weight of the chassis above the

rotors, the rotors are used to pull the weight of the chassis off the ground. Helicopters

obtain stable flight by keeping the weight below the rotors. Since the group wanted tokeep the chassis as small as possible the rotor diameter and separation would provide

the basis for the largest dimensions. An encompassing chassis shell was used to shield

the rotors from damage cause by collisions. The chassis does not extend far above or

below the top and bottom rotor set, respectively. This design does not utilize theweight of the chassis as a good stabilizing mechanism. To provide the most stable

flight, weight would have to be concentrated as low in the chassis as possible. The

outside shell was then redesigned to be hollow to allow storage of electronics andbatteries. The motors needed to remain in the center of the chassis to directly power

the rotors, but all other electronics could be moved to the outer ring. The cross section

of the chassis allows for positioning of the electronics low on the fuselage. Thisstorage space in the chassis creates a lower center of gravity which will help produce

more stable flight.


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V. Prototype Justification

Some of the many reasons for building prototypes prior to implementing a

design into full-scale production are to reduce costs, assess potential risks, discoverand resolve any issues associated with production, and to demonstrate the

functionality of the product. The majority of these reasons are intertwined with oneanother, which provides further justification that building a prototype is a useful stepin the design process.

Cost reduction is a key motivation in constructing a prototype. The other

reasons that support prototype building tie into cost reduction. For example,discovering a flaw in your design that can only be found through the construction

phase drastically lowers cost impact if it is discovered while only building one

prototype as opposed to a whole lot during production that would have to bescrapped. Assessing the potential risks, which could prove to be very expensive,

during the prototype construction phase could also save a lot of money as opposed to

discovering the risks during production. These discoveries could also save a lot oftime, which is often referred to as money. Aside from reducing costs, risk assessment

during the prototype building process is a vital part of the design to production

process as it allows the designers and potential customers to discover any risks that

may be associated with the product. This allows them to make informed decisionsrelated to the design, production process, and post production phases associated with

the product.

Other very important reasons that justify the construction of a prototype before

proceeding to production are to discover, and correct, any problems that may beassociated with the design to production process as well as to demonstrate the use and

functionality of the product. In discovering any problems related to the design the

product can be easily corrected to fix the problem without significant impact or extracosts added to the development process. Discovering these problems associated with

the design also increases development and production speed as a change can be made

easily during the prototyping phase, but would require much more extensive work tocorrect during the production phase, which also saves a lot of time and money.

Prototypes are also very useful in that they can be used to check the product

against set requirements and/or project objectives that the team wishes to achieve. Indoing this, it lets the designers see where they are in the process and what they need

to do or change to get where they need to be. Another benefit of building a prototype

of ones product is to present to potential customers. This allows them to see what theproduct is capable of and how it could prove to be beneficial to the company. The

designers can also get feedback from the potential customers at this time in order to

better the product and make any changes that may be desired. Demonstrating theproducts potential uses and functionality could also prove to be a source of funding if

this occurs during the early stages of design of a research and development type

project that a customer or venture capitalist believes in.


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The prototyping phase is a very important part of the design to productionprocess for numerous reasons that include, but are not limited to, cost reduction,

problem or design error detection, assessing risks associated with the product, and

presenting the functionality of the product to potential customers as well as investors.In considering the entire product development process from concept to design to

production, the construction of prototypes is very justified in numerous ways, buteach one alone provides enough sound reasoning to move forward with the buildingof a prototype before going on to full scale production. All of the involved parties

from engineers to customers benefit from the process of prototype building, as it is a

great opportunity to make sure the product is exactly what is desired or make the

necessary changes quickly and easily to achieve the best product in the least amountof time.

VI. Prototype Manufacturability

For the manufacturing of the shell we chose to use a fiberglass composite

material because of its high strength to weight ratio. As with many other compositematerials, the two materials act together, each overcoming the deficits of the other.

Whereas the plastic resins are strong in compressive loading and relatively weak in

tensile strength, the glass fibers are very strong in tension but have no strength against

compression. By combining the two materials together, the fiberglass compositebecomes a material that resists both compressive and tensile forces.

Fiberglass also appealed to us because of the ability of fiberglass to be moldedinto complex shapes. A layer of fiberglass mat is applied over a shape of our

choosing, and resin is applied over it. Next all air bubbles are removed; this is donebecause the presence of air pockets will significantly reduce the strength of the

finished mold. Once the final layers of fiberglass are applied to the mold, the resin is

allowed to set and cure. In addition fiberglass has very low chemical reactivitycharacteristics. Low chemical reactivity becomes an asset not only from a

maintenance stand point but it also allows our unit to be deployed in a wider range of

environments.

After the completion of the fiberglass the internal frameworks will be

manufactured. The internal frame will hold the electrical equipment such as the

motors, servos, and speed controller. The internal frame consists of lightweightaluminum to minimize the weight. The frame will be bolted to the fiberglass and the

motors will be enclosed in a hollow aluminum cylinder. The motors are enclosed in

the hollow cylinder in order to have them coaxial. The servos and other equipmentwill rest outside the aluminum cylinder and bolted to the arm of the frame that

attaches to the fiberglass. View the images below for a section view and conceptual

drawing.


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The aluminum frames such as the hollow cylinder and flat plate will bepurchased already manufactured. The frame and plate would then be cut to meet our

requirements of height and width. Other components such as the swashplate

assembly, rotor blades, speed controller, and rotor shaft will also be purchased.

The decision to purchase these components are base on quality control, cost and

time. Four blades are used for the UAV, all of the blades must be symmetrical andweigh the same, or else an imbalance develops during flight that may make the craft

unstable. Manufacturing the blades would be difficult and time consuming, the most

readily available material is wood and wood working can produce inconsistent

results.

The swashplate assembly and rotorshaft were also purchased because of the

high tolerances needed to produce them. The swashplate assembly and rotorshaft are


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relatively inexpensive components to purchase but require special equipment andintensive labor to produce if done by hand.

Once all components are manufactured and received, the team will then begintesting and building the prototype UAV. Prior to assembly the team will test

individual components to verify that they meet the performance requirements of thegroup. Batteries will be tested to verify that they output the correct voltages, themotors and actuators will be tested to verify that they are capable of working

according to specifications, the speed controller, and radio receiver/transmitter will be

tested as well.

Once all components are verified to be working correctly the prototype will then

be assembled. The mechanical components attached to the inner aluminum frame and

the inner frame to the fiberglass.

VII. Prototype TestingAfter all the components are assembled the team will commence testing. The

testing phase will reveal any inherent instability or excessive vibrations that can cause

catastrophic failure during operations. The testing will be methodically performed in

order to insure correct system response.

The servos will be raised and lowered to verify that they are functioning

properly and that the blades are not coming in contact with each other. Once theactuators are verified to be functioning, power will be gently throttled up and down to

verify that the motors are spinning opposite of each other and that both are insynchronous speed. The speed controller will then be tested to verify that the motors

can come in and out of synchronization automatically. After this is verified enough

power is then applied to cause the UAV to raise 6inches off the ground. The UAVwill be anchored from all sides to prevent it from drifting out of control or from rising

too high from the ground during initial testing.

The UAVs ability to rotate and maintain hover will then be examined. Should

the UAV have a tendency to drift, it may mean that the center of gravity is not on

center, in which case mechanically mixing using the controller would be applied to

negate the affects. If high vibrations are evident it may mean a component is notsufficient secured. Once the pilot has command of the UAVs rotation and hovering

ability, the anchor will be removed and then the UAV will be tested with waypoints

such as traveling around the room or to specific spots and hovering.


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VIII. Conclusion

The mission of the Unmanned Aerial Vehicle has greatly expanded over the

years as military operations increase in complexity and human resources dwindle.The UAV allows the military to survey hostile situations without committing soldiers

into harms way. With UAVs the military can explore the caves of Afghanistanwithout the dangers of soldier stepping on Improvised Explosive Devices or walkinginto an ambush.

Our objective is to give the soldier on the ground flexibility to search, locate and

identify targets and locations, without plunging headfirst into a hostile situation. Theuse of the UAV is also not limited to military applications. The UAV can be utilized

by government agencies such as the Department of Home Land Security to monitor

sites of interest such as power plants, landmarks, and critical infrastructures. Thevehicle can also be used by the Border Patrol for various search and rescue missions.

For example, it can be used to rescue a lost mountain climber. The uses for the UAV

are virtually up to the imagination of its owners.

The final selected design of the Unmanned Aerial Vehicle is a ducted coaxial

rotary blade. The coaxial configuration allows a compact design, as a tail boom is not

needed. The selected design will be able to maintain a hover and level flight as wellas be able to maneuver on all three axes. The minimum flight time is approximately

fifteen minutes and maximum operating altitude is one hundred feet. The UAV will

be upgradeable to transmit a live video feed back to the operator; the camera can bemaneuvered independently of the UAV. The technical areas of focus for the UAV are

the aerodynamics and flight characteristic, the wireless transmission and radiocontrol, the structural integrity of the airframe, and the power plant.

Existing designs used similar technologies such as ducted coaxial blades.However, their disadvantages are their size and weight. The blade diameter of the

Sikorsky Cypher is 6.5 feet, which greatly exceeds the teams blade diameter of 14

inches. The teams compact weight and design allows the UAV to be transported byinfantry and deployed within buildings and in close proximity to obstacles and

structures. The parts needed to create the prototype have been ordered and once they

arrive the group will begin building and testing the UAV.


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IX. References

www.towerhobbies.comwww.heliproz.comwww.trendtimes.comwww.shopmaninc.comwww.xheli.comhttp://www.army.mil/factfiles/http://www.gizmag.com/go/2440/http://www.cbp.gov/xp/cgov/border_security/GlobalSecurity. 14 August 2005. 20 September 2007

http://www.globalsecurity.org/intell/systems/uav.htm

GlobalSecurity.org. Sikorsky Cypher II - Dragon Warrior . 20 February 2005. 20September 2007

http://www.kansasuav.org/index.php?option=com_content&task=view&id=2

2&Itemid=2

Cypher. 2007. 20 September 2007http://www.globalsecurity.org/intell/systems/cypher.htm

www.radioshack.comwww.dynaspy.comFLUID MECHANICS by Frank M. WhiteGessow, Alfred and Garry C. Myers. Aeryodynamics of the Helicopter. New

York: The Macmillan Company, 1952.

How Helicopters Fly and are Controlled. 12 October 2007 .

Morris, Charles Lester. Pioneering The Helicopter. New York: McGraw-HillBook Company, Inc., 1945.

Shapiro, Jacob. Principles of Helicopter Engineering. London: Temple PressLimited, 1955.

Additional References Listed In Bill of Materials


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X. Appendix

i. Gantt Chart

ii. Bill of Materials


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iii. Nugget Chart

group 15 phase iv report

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