Project Plan - ECpE Senior Design
LOCKHEED MARTIN CHALLENGE
PROJECT PLAN
ECPE 491/Engineering 466
CLIENT
Cory Tallman of the Lockheed Martin Corporation
FACULTY ADVISORS
Dr. Steve Holland Dr. Peter Sherman
TEAM MEMBERS
Jason Ekstrand Jordan Lee
Tyler Fast
Peter Hodgell
Timothy Jacobs
Daniel Jason
Matt Krajewski
Aidan Rinehart
David Snyder
Matt Stemper
Scott Strong
Eric Villhauer
DATE SUBMITTED
October 12, 2009
Page | 1
REPORT DISCLAIMER NOTICE
DISCLAIMER: This document was developed as a part of the requirements of a multidisciplinary engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design or a professional land‐surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student‐prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the course coordinator.
NOTE: * denotes work of 08-09 Lockheed Martin Challenge Team.
Page | 2
Table of Contents
Page | 3
Page | 4
ABSTRACT
Currently, no unmanned aerial reconnaissance vehicle capable of vertical launch exists on the market. Lockheed Martin has asked us to design a prototype for them. The 2008 Team designed a plane capable of vertical launch but were not able to achieve stable video or a functioning autopilot system. We hope to finish these two features.
The existing UAV and launch system currently work to spec and no major changes are planned.
However, the autopilot will need a number of new sensors and programmed to work with the plane. The camera system will likely need a complete redesign due to a number of issues that add together to create significant motion blur.
Page | 5
EXECUTIVE SUMMARY
Modern warfare has seen a shift in location to more urban settings. Urban structures are the new terrain for soldiers. These structures can be a large hindrance to military operations because they block large lines of sight. To better equip the modern solider a new system needs to be implemented. This new system should allow soldiers to see around urban structures which will provide them with an advantage over their opponent. The Multidisciplinary Design Class has the task of continuing the work of the Multidisciplinary Design Class of 2008-2009. The end result will be a Unmanned Aerial Vehicle (UAV) that can be utilized in urban settings for revealing dangerous situations. One of the largest differences of this UAV compared to other UAV already in use is the vertical launch capabilities. This will allow the UAV to maneuver over the top and in the midst of urban buildings. The UAV system should be completely autonomous ensuring simple use for soldiers. The UAV will be designed to launch, provide surveillance, and land autonomously. The soldier’s requirement is to input the waypoints. The camera system mounted on the UAV will provide live feedback to the launch station. The current task is divided into three sub groups; optics, which will research new cameras and implement a device capable of meeting resolution requirements, aeronautics, which will improve on the wing design from last year, and avionics, which will model the current aerodynamics to program the autopilot. These three groups will be integrated throughout the process to develop a seamless UAV vertical launch surveillance system.
ACKNOWLEDGEMENTS
The LM Challenge Team would like to thank Dr. Sherman, Dr. Holland, and Cory Tallman from
Lockheed Martin Skunk Works out of Fort Worth, TX for all of their guidance and support on this project. The LM Challenge Team would also like to extend thanks and gratitude to last year’s team who made so many great steps towards accomplishing the goals set out for us.
Page | 6
CUSTOMER REQUIREMENTS
STATEMENT OF NEED
Currently, UAV technology is not capable of launching vertically for use in an urban environment.
This makes it difficult for soldiers to see dangers in an urban combat zone. Due to this problem,
Lockheed Martin has asked the ISU Multidisciplinary Design Team to design a UAV that can be launched within the confines of an urban setting. This vehicle will be used to fly low reconnaissance missions prior to U.S. ground troops occupying the designated area.
CUSTOMER DESIGN CONCEPT
Figure 1 - Detailed SolidWorks model of assembled UAV*
Page | 7
Figure 2 - Exploded SolidWorks model of UAV*
Page | 8
SYSTEM DISCRIPTION
Lockheed Martin recommends the design of the UAV to have an approximate gross weight of ten pounds which includes a target avionics payload of three pounds. This system should be able to fly for approximately one hour with fifteen minutes of setup time. The avionics subsystem must include video and navigation systems that are capable of communicating with a ground station. The
UAV must be vertically, pneumatically rail launched. When launched, the UAV must be able to clear a forty foot tall obstacle located twenty feet down the flight path which represents buildings in an urban environment. After launch, the UAV must reach a cruise altitude of 100 feet and a cruise speed of 40 to 50 knots. The UAV will be designed for a belly landing. Lastly, this UAS must be able to fit in the back of a military Humvee for easy transport.
Figure 3 - System Flowchart*
OPERATING ENVIRONMENT
The system will be designed to operate when wind is minimal, and no severe weather conditions exist such as rain, sleet, or snow. No provisions will be made for the possibility of operation in inclement weather.
The system will be designed to allow for transportation in a military Humvee (5'x2.5'x1.5') without damage to components or failure of subsystems.
Page | 9
FUNCTION REQUIREMENTS
FR01- The UAV shall be capable of flying at a cruising speed of 40-50 knots.
FR02- The UAV shall be capable of flying for 1 hour.
FR03- The UAV shall be capable of resolving a 6 inch target 100 feet below the aircraft.
FR04- The UAV shall be capable of vertical or near vertical launch from a pneumatic rail system.
FR05- The UAV shall be capable of climbing to an altitude of 100 feet.
FR06- The UAV shall be capable of clearing a 40 foot tall obstacle, 20 feet downrange.
FR07- The UAV shall not be very noticeable to a ground observer.
NON-FUNCTIONAL REQUIREMENTS
NFR01- The UAV shall use an electric motor.
NFR02- The UAS shall fit into the back of a Military Humvee (5’x2.5’x1.5’).
NFR03- The UAV shall only fly under moderately calm, clear conditions.
NFR04- The UAS shall be capable of autonomously navigating through GPS waypoints.
Page | 10
USER INTERFACE REQUIREMENTS
UIR01- The ground station for the UAS shall display real time video as transmitted from the onboard camera.
UIR02- The ground station for the UAS shall have the controls necessary for manual override of the UAV.
UIR03- The ground station for the UAS shall have the ability to transmit and receive flight data to the onboard autopilot system.
UIR04- The ground station for the UAS shall be mobile and have the ability to be transported in the back of a Military Humvee.
UIR05- The launch and control systems will be designed for easy set-up, taking approximately 15 minutes.
UIR06- Safety of operators and observers of the UAS will be of high priority when designing the system.
UIR07- The operator must have the ability to override the autopilot system through a remote control system.
ACCOMPLISHED BY 2008-2009 TEAM
A01- Rail launch UAV under R/C
A02- Rail launch UAV-autopilot control for steady level flight, R/C control for take-off and landing
A03- Demonstrate in-flight live video feed.
A04- Size constraints met
Page | 11
DELIVERABLES FOR 2009-2010 TEAM
D01- Project Plan–Sept 25th, 2009
D02- Launch system verified—Oct 25, 2009
D03- Simulink airplane model complete–Oct 31, 2009
D04- Additional prototype body–Nov 18, 2009
D05- Simulink control system complete–Nov 29, 2009
D06- Testing of airplane and launch system–Dec 1 , 2009
D07- New video system installed—Dec 1 , 2009
D08- Final report –Dec 2, 2009
D09- Complete positive identification test with camera system – February 15, 2010
D10- Reduce total system weight to 10 lbs – March 15, 2010
D11- Achieve a predetermined flight path under full auto pilot – April 15, 2010
D12- Resolve an assault type weapon under autonomous flight – May 1, 2010
Page | 12
MARKET LITERATURE SURVEY*
Unmanned Aerial Vehicles have become a staple for modern military operations, ranging from tiny hand launched spy bots to massive aircrafts that can scan an area the size of Illinois in 24 hours.
After conducting research on current UAS technology, three systems have similar capabilities as put forth by Lockheed Martin. These are the Lockheed Martin Desert Hawk and Stalker, and the Boeing
Scan Eagle TM .
DESERT HAWK
Military forces use the Desert Hawk system primarily for surveillance and reconnaissance during the day or night. The system is especially designed for portability, with a wingspan of 54 inches and an overall length of 36 inches. It weighs 6.5 pounds dry, with the possibility of adding 2 pounds of plug and play payload. The payloads range from a rotating camera that can be used to fix on targets at greater distances to a fixed camera which utilizes IR technologies to conduct surveillance during the day or night. Also A third camera can be used to allow the Desert Hawk to see in total darkness.
The Desert Hawk UAS has a lightweight, portable ground station that is capable of pre-flight planning and uploading waypoints for the UAV. It is also capable of sending real-time information, such as waypoints to dynamically change the flight path as needed.
The Desert Hawk also incorporates stealth characteristics. With its ultra quiet motor, it is not easily seen or heard within a 100 foot range.
STALKER
The Lockheed Martin Stalker is a UAS created by Skunk Works in 2006. The Stalker was created by the same team that made the Desert Hawk. The Stalker has a ten foot wingspan, its maximum takeoff weight is fourteen pounds, and the endurance of the plane is two hours. The plane is hand launched and belly landed. The Stalker uses an ultra quiet electric motor and propeller, and it carries a camera payload along with the ability to carry other payloads. The Stalker’s camera system is quite advanced: it has modules for daylight, low light, and infrared cameras. The camera system can be detached to allow for droppable payloads. When landing the payload system retracts into the fuselage.
Page | 13
SCAN EAGLE
TM
The Scan Eagle™ is a UAS that was developed by Boeing for autonomous surveillance of the battlefield and introduced to the armed forces in 2005. The Scan Eagle™ carries a payload that consists of an inertial stabilized camera and turret for taking surveillance video. The camera can be swapped out for an infrared camera. Also onboard the Scan Eagle™ is a Synthetic Aperture Radar
(SAR). The radar system on the UAV is the world’s smallest SAR. The Scan Eagle™ has a communication range of about 100 kilometers and has a flight time of over twenty hours at seventy knots. The Scan Eagle™ is launched using a pneumatic launching system that has been patented by
Insitu®. For the landing phase of the flight, the Scan Eagle™ uses a hook retrieval system that uses a forty to fifty foot tall pole which has a hook on it that catches a hook on the UAV. Using differential
GPS on the pole and on the UAV, the UAV is able to navigate to the pole and catch on the hook.
Page | 14
DESIGN CONCEPTS
This section reviews the design concepts which will be explored throughout the semester in order to better the current design.
AUTOPILOT DESIGN
A major goal of this year’s team will be to improve image quality by flying on a predetermined flight path about the target to focus video capture on the target. The flight path will be determined from flight testing and simulation and will most likely be in the form of a conic section. A flight path of this nature would focus the camera on a single point on the ground eliminating the blur associated with the moving airplane.
Specifications
MicroPilot Model 2128
Weight: 28g
Dimensions: 100 (L) x 40 (W) x 15 (H) mm
Power Requirements: 140mA at 6.5VDC
Supply Voltage: 4.2-26VDC
Capabilities
Figure 4 - MicroPilot Model 2128
This model from MicroPilot includes ground station software (Horizon), can handle up to 1000 waypoints with in-flight modification possible (FR01), and is capable of controlling up to 24 servos simultaneously. The on-board GPS updates at a rate of 4 Hz.
Page | 15
Sensors
The 2128 provides support for airspeed (up to 500kph), altimeter (up to 12,000 MSL), IMU (3-axis rate gyro/accelerometers), and GPS. The accelerometers saturate at 4 G’s.
Data Collection and Customization
The integrated sensors – 4 Hz GPS and compass – provide the necessary data to ensure reliable launch and recovery of the aircraft (FR08). The number of I/O ports and user-defined telemetry allow for unparalleled customization of the autopilot, ranging from a special launch sequence initiation to in-flight refinement of PID control loops to the ability to monitor system performance and power usage. This autopilot also increases the modularity of the design (NFR02) by allowing for a broad range of changes during any future iteration or work on the project. Additional systems or redesigned systems may be easily incorporated into and controlled by the autopilot.
One of the primary limitations of the autopilot, with regard to our current launch sequence and mission, is the relatively low saturation point of the IMU accelerometers (4 G’s). Due to the high Gload, the accelerometers are unreliable during the launch phase. However, this issue can be overcome by implementing a custom launch configuration that does not rely on the accelerometers, but rather, on other peripherals that are unaffected by the G-forces.
Backup of Automation Navigation System
Currently, the UAV is set up to navigate using GPS signals exclusively, and is not prepared with backup support for the event of loss of GPS signal. The plan this year will be to add a 3D compass unit built by MicroPilot to the autopilot system to provide backup to GPS navigation. The ground station software or the autopilot can record the UAV’s position, altitude, and velocity at the time of
GPS signal loss, then use the 3D compass and AGL to navigate to a preprogrammed landing position or towards the subsequent waypoints.
Turning Autopilot Navigation
This year, we will need to tune all PIDs to allow for waypoint navigation. Last year’s team was able to tune for pitch and yaw but we will be finding a way to tune all PIDs to allow for more confidence in our results and uniformity in our solutions. A large number of test flights will be necessary.
Page | 16
Purchase of New Radio
In case of loss of radio signal to the ground station, the current autopilot configuration is not compatible with the radio controller presets and does not allow for the UAV to return on a set path through the autopilot. In order for the flight to be completely autonomous in the event of a signal loss, a new radio system will need to selected, purchased and installed.
Landing Procedure
The UAV will not be required to land under autopilot control. The system will be switched to radio control once the UAV has returned from completing its mission and then landed manually.
LAUNCH SYSTEM DESIGN
Specifications
Launch a 10 lb UAV using a pneumatically power system
Clear 40 foot tall obstacle within 20 feet down range
Achieve a final speed of 35 knots 40 feet above ground
Entire launch system must fit with the confines of a military Humvee.
Launch must be nearly vertical
Bearing or Guide Design
The current launch system has a significant gap between the ceramic bearing and guide system, allowing for undesired degrees of rotation.
This problem can be remedied by the following solutions:
1.) Re-Coat Guide Rail
Using a Teflon coating will lower the coefficient of friction between the rail and UAV, allowing for higher velocities at launch. Dupont’s Lube-Coat cost $200 per unit and is heat, chemical, and weather resistant.
Page | 17
2.) Lower fit tolerance between bearing and guide rail
The ceramic bearing has a 90 degree cut-a-way allowing for additional play to prevent the launch from seizing (see figure to right). Reducing this cut-a-way should prevent rotation and focus more force on the UAV. Additional ceramic bearings will cost approximately $30.00 per unit.
3.) New Bearing Material
After researching various materials, the ceramic bearing in contact with steel proved to be most cost-effective combination. Harder materials may not scratch, but they are more expensive and will cause greater friction build up.
Slip Resistant Feet
Since the setup isn’t completely vertical, the support system is slightly displaced due to the horizontal component of the launch force. Utilizing slip resistant feet will limit, if not eliminate, this issue.
Solutions:
1.) Increase Pad Size
Using larger slip resistant feet will provide extra stability and help spread out the force over a larger area.
2.) Add Weight to Launch System
By adding weight to launch system will create a greater normal force to offset the large launch force. This can be done by adding sandbags to support legs, which are priced at
$3.00.
3.) Using More Slip Resistant Materials
Rubber is currently priced at $0.95 cents / pound and would be a minor expense when compared to the stability it would add to the support legs.
Page | 18
Parachute Release System
Currently, the air cylinder propels both a PVC push rod and the UAV along the guide rail and into the air during launch. A string is attached to the end-cap of the PVC rod, which releases a parachute when the string reaches its end. The PVC rod decelerates, but still acts as a projectile and could cause harm to anyone down range.
Solutions
1.) Helicopter design
Utilizes a “helicopter-like” fin which releases immediately after launch. This design decelerates the rod a quicker rate which prevents it from gaining enough speed to cause any harm for bystanders.
2.) Bungy Chord
Currently, the string attached to the end-cap breaks nearly every launch. Installing hooks onto the end-cap and air cylinder would restrict the PVC rod from turning into a projectile.
Using a bungy cord allows for multiple launches, and cuts down on set up time.
3.) Timed Fuse
Eliminate string attachment and utilize a timing mechanism for parachute deployment.
This limits abrupt jerks during launch and fluent launch.
Leg Assembly
Support legs are currently (3) Aluminum square stock pieces with are attached to launch rail by
(12) wing nuts. Although the supports fit it the confines of a Humvee, it makes for long assembly.
Attachment of the legs to the launch rail needs to be improved to decrease assembly time. A part on one of the leg assemblies will need to be replaced.
Solution
1.) Collapsing Legs
This system incorporates folding legs allowing for a uniform launch system that can be easily assembled and broken-down.
2.) Telescoping Legs
This system will use a push-pin design to decrease assembly time and eliminate additional loose parts.
Page | 19
IMAGING SYSTEM DESIGN
Requirements for the Imaging System
The customer requirements for the imaging system are decidedly vague. We have decided to further constrain “resolve a 6” target” to be able to positively identify a handgun (approximately
7.25” x 4”).
The design of the plane adds further constraints.
The payload limits of the plane restrict the full camera system to approximately one pound
This further limits us to requiring a simplistic design with minimal onboard electronics.
The camera must have a suitably high resolution.
Image size is constrained by air-to-ground bandwidth
The camera system must work with the existing plane with minimal modifications.
Current Camera Status
Specifications
Weight: 137g
Dimensions: 55 (L) x 31 (W) x 31 (H) mm
Power: 180mA at 12VDC
Effective pixels (NTSC): 768 (H) x 494 (V)
Figure 5 - KT&C Model KPC - 650
Page | 20
The 2008 group choose the KT&C KPC-650 camera with a varifocal lens (Tamron 13VG550ASIISQ
5-50mm) to provide video capabilities to the aircraft. However, in-flight tests did not provide a meaningful assessment as to whether or not this camera will work in this application. The camera was tested in-flight, but an erratic flight path contributed to blurred video. While portions of the video were able to identify objects on the ground, most of the video was not useful.
This year’s group will first evaluate the camera performance on three fronts:
Mathematical calculations and simulation to assess the effects of vibration and flight path
In-flight tests using the autopilot and a more stable flight path
Lab testing using a moving camera
An expected limitation with this camera is a lack of manual control. This camera is designed to automatically adjust to the optimal lighting condition; most commonly by increasing the shutter time. However, at the speeds the plane will be moving this will lead to considerable motion blur. It is also limited to NTSC video (768x494) which necessitates the use of a high powered zoom lens to be able to identify a small target. This limits the time an object is in view (under .25 seconds in many cases) and introduces significant blur due to plane vibration. A higher resolution still camera
(2 megapixel) would allow for a significant reduction in zoom and while retaining or improving the resolution capabilities.
If it is determined that the current camera will not meet the requirements, a new camera system will be purchased and added to the aircraft. The camera must be able to positively identify a 6-inch handgun at an altitude of 100 feet in face of challenges such as motion-blurring.
To simulate camera performance, a Matlab program was created which would take a variety of inputs and output a typical image frame and the corresponding values.
Page | 21
Figure 6 - Matlab Camera Blur Simulation
By inputting the parameters Height, Focal Length, Speed, Camera Resolution, Shutter Speed, CCD
Size, and the rates of Pitch, Roll and Yaw, the program is capable of generating a predicted image frame and the values for Horizontal and Vertical image size (in feet), the size of a pixel (inches), expected motion blur, and the time an object will remain in view of the camera.
In the image, the red dashed line is the field of view of the camera. The center red box is the relative size of a 6” square and the overlapping blue box shows the corresponding motion blur for a given frame. The upper two boxes sets of boxes show the path an object will take while moving through the cameras field of view. With the creation of a predetermined flight path, the presence of motion blur will be minimized. This can be accomplished by focusing on the target for a longer period of time.
Page | 22
Current Video Transmitter Status
Specifications
Weight: 30g
Dimensions: 26 x 50 x 13 mm
Power: 500mA at 12VDC
Output: 1 Watt transmission signal
Operating Frequency: 2.4 GHz
Figure 7 - LawMate Model TM-241800
The current video transmitter is not able to provide video transmission at the required distance. It is not possible to purchase a video transmitter at a power higher than 1W due to civilian regulations, but a higher power transmitter could be used in a final military product. While a directional antenna would provide greater range than the omnidirectional antenna used, a directional antenna would not work in the application of an aircraft transmitting data throughout its flight. The group plans to investigate purchasing a different antenna at the base station to improve the range of the video transmission system.
For testing and prototype purposes, onboard storage may be introduced. This would eliminate bandwidth and range issues while a military production model would be able to overcome these limitations with higher powered transmitters.
Page | 23
Single Video Camera Approach
The existing video camera will likely be unsuitable due to lack of manual exposure controls, however a video camera with more features would still meet requirements.
Pros
Simple
Use off-the-shelf NTSC video equipment to return data to ground
Light
Cons
Low Resolution
Current camera has no manual control
Video Camera with Gimbal Approach
Pros
Some correction for vibration blur
Cons
Heavy
Complicated - requires three servos that must react in real time to plane rotation
No correction for velocity blur
Vibration/rotation likely too rapid to provide much correction
Still Camera Approach
Pros
High resolution
Lightweight
Cons
Complicated transmission protocol
Limited refresh rate - 10 frames/second likely generous
Page | 24
Combination Video and Still Camera Approach
Pros
Combines fast refresh rate of video and high resolution still camera
Cons
Heaviest two cameras
Requires modification of plane
Requires high bandwidth
Requirements Weighting Existing Camera Gimbal Still Camera Combination Still/Video
Weight 3 4 2 3 2
Simple
Framerate
Resolution
1
2
3
4
3
2
1
3
2
3
2
4
2
4
4
Bandwidth 1
Work w/ plane 3
Total:
4
4
44
4
1
3
3
29 40
Figure 8 - Imaging System Design Matrix
2
2
36
Page | 25
PROPELLER DESIGN
It was suggested in the report from spring 2009 in the “Recommendations for Future Work” section that a 16 x 10 propeller should be tested in replace of the 14 x 10 propeller .The report states the motivation for using the 16 x 10 propeller would be to “produce a more significant amount of thrust at lower speeds…. [It] will be a better trade off for the launch portion…” Although the 16 x 10 propeller will produce more thrust for launch portion of the flight, it will have a significantly lower cruise speed and endurance.
Although a simple analysis can be conducted with respect to each propeller’s efficiency, to completely understand the extent of the tradeoffs between the two propellers they will need to be tested with the completed aircraft. Propeller efficiency is defined as
𝑃
𝐴
= 𝜂 𝑝𝑟
𝑃
Where 𝑃
𝐴
is the power available from the motor propeller combination, 𝜂 𝑝𝑟
is the propeller efficiency, and 𝑃 is the shaft power transmitted to the propeller from the motor. The propeller efficiency is a function of the advance ratio, 𝐽 , which is defined as
Where 𝑉
∞
𝐽 =
𝑉
∞
𝑁𝐷
is the free stream velocity of the aircraft, 𝑁 is the number of propeller revolutions per second, and 𝐷 is the diameter of the propeller. As 𝐽 increases so does the propeller efficiency therefore a larger diameter propeller would make 𝐽 smaller decreasing the propeller efficiency.
This conclusion suggests that it would be more beneficial to try to reduce the weight instead of increasing the propeller diameter if the thrust generated by the propeller is not sufficient at launch.
The 14 x 10 costs $4.98 and the 16 x 10 propeller costs $7.50 which compared to the rest of the aircraft are both relatively cheap. Compared to each other the 16 x 10 propeller costs more than one and half times the 14 x 10 propeller.
It may be such that the weight of the aircraft cannot be reduced and the thrust generated by the 14 x 10 propeller cannot be sufficient during launch. In this case a more powerful power plant configuration may need to be considered in order to obtain the desired cruise speed and endurance with the 16 x 10 propeller. Ultimately fight tests will need to determine the capability of each propeller.
Page | 26
WING DESIGN
Requirements
The requirements for this wing are outlined in the previous year’s report. The performance requirements are high enough lift to steady state cruise at 40– 50 knots with an all up weight of approximately 10 lbs. The wing must also develop enough lift at low velocities to accommodate the vertical launch sequence when the aircraft transitions from a nearly vertical trajectory to horizontal flight. Structurally the wing must be able to withstand the launch acceleration in excess of 20 g’s.
Last year’s construction strategy using spyder foam cores with a carbon fiber skin proved to have adequate structural integrity. Utilizing the same construction method will produce a wing with enough strength and an adequately low weight.
Aspect Ratio
AR = b 2
S
Aspect ratio has the most effect on the maximum coefficient of lift of a wing, more so than taper ratio. The equation is wingspan squared over the wing area. Increasing AR will increase the maximum C
L
and potentially the maximum lift force. Drag also decreases with an increase in AR , and the maximum speed of the aircraft can increase. However, when AR is increased for a limited wingspan the total wing area can decrease which could lead to a lower actual lifting force.
Decreasing chord also decreases the effective Reynolds number of the airfoil section which can lead to poor characteristics at low speed if the airfoil is not chosen carefully.
The AR effect on the maximum C
L equation and the 2D airfoil data.
of a wing can be determined analytically using the following dC
L d α
= C
L α
=
C l α
∗ AR
(2 + (4 + AR 2 )
1
⁄
2 )
To utilize this equation the 2D lift slope is input as C l α
and the equation is solved with a given AR to find the lift slope of the 3-dimensional wing, per degree. Then, the 2D airfoil characteristics are used to determine the zero lift angle of attack, α
L=0
. Then, to find the total lift the difference in degrees between the zero lift angle and the desired cruise angle is multiplied by the 3D lift slope.
XFLR5 is a freely downloadable program and is a GUI for the XFoil airfoil analysis FORTRAN code developed by Mark Drela. XFLR5 also a very effective means of 2D and 3D wing analysis. XFLR5 was used to determine 2D airfoil characteristics and to verify lift approximations.
Page | 27
Taper Ratio
Taper Ratio = c root c tip
The Taper ratio increases the maximum C
L the aspect ratio.
, and decreases induced drag, but to a lesser degree than
Airfoil Cross Section
The airfoil 2D cross section affects the wing C
L
and the C
D
. Balanced airfoil characteristics are necessary for this project because there are a variety of different flight conditions the aircraft must adequately perform in. The takeoff and landing require stable flight (no stall), low moment, and high lift at low velocity. The cruise portion requires optimal lift at minimal drag with a low moment so not very much elevator trim will be required. For this project an airfoil with smooth transient response is also required because an autonomous navigation and stabilization system will be used.
An airfoil with high moment and poor stall reattachment properties could saturate the autopilot and lead to stability problems.
An airfoil with higher camber will have a higher maximum C
L
and be thicker which will make it structurally stronger longitudinally and more resistant to torsion. However, a highly cambered airfoil will not always perform better at low velocity because at extremely low Reynolds numbers the flow will separate causing a stall condition. A high cambered airfoil will also have higher drag because of the increased cross section and flow separation.
A moderately cambered airfoil will perform better at intermediate velocity and have better all around characteristics. It will not have the lowest drag possible for the cruise portion of the mission, and it won’t have the maximum lift for the takeoff and landing conditions. However, a medium camber airfoil will have a moderate moment and usually good stall characteristics.
Winglets and Boundary Layer Control Devices:
Winglets and other flow modification devices, when implemented correctly can positively modify the wing’s performance. Martin Hepperle’s model aircraft website provides information about winglet benefits and design guidelines. From his experiments the most beneficial and easy to implement winglet design is a sharp angle transition from wing to winglet shifted downstream 50% of the tip chord. The winglet’s function is to increase the effective AR and prevent the formation of tip vortices and induced drag. However, the size of the winglets and the orientation must be chosen carefully to prevent the planform and skin friction drag increases from negating the positive aerodynamic effects of adding winglets. Winglets which are angled out from the center of the wing would also increase the lateral stability by inducing a dihedral effect even if the rest of the wing is flat.
Page | 28
Pneumatic and mechanical turbulators are used on low Reynolds number wings to trip the boundary layer flow from laminar to turbulent before the natural transition occurs. The intent is to decrease the size of the flow separation bubble and decrease the pressure drag created by the bubble. Turbulators are difficult to design because at intermediate Reynolds numbers they are very thin, are very sensitive to angle of attack, and require a very smooth wing surface to function correctly.
Current State
The current state wing design is outlined below and was tested with XFLR5 to verify performance predictions.
Airfoil: Clark Y
Wingspan: 56 inches
Root Chord: 10 inches
Tip Chord: 8.5 inches (taper starts 18 inches from wing tip)
Mounted with 2.5 degree AOA with respect to motor thrust line
Below are wing design tables which calculate the wing size needed based on the aspect ratio, velocity, weight and steady state flight conditions. Approximations made included a linear lift slope, rectangular wing, and that the specifications of the airframe match the report. The numbers are generated using the lift slope correction equation and lift equation.
Page | 29
The constants used are:
Weight = 10lb
V
∞
= 45 knots ≈ 64.29 ft/s
Clark Y
Weight, lbs
Current State
Cruise
Velocity, ft/s
Aspect
Ratio dCL/d_alpha,
CL/deg
Steady
State
AOA, degrees
Steady
State
C_L
S,
Wing
Area, ft^2 b, wingspan inches b in feet c, chord inches c in feet
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
64.29 4.00
64.29 5.00
64.29 6.00
64.29 7.00
64.29 8.00
64.29 9.00
64.29 10.00
64.29 11.00
64.29 12.00
64.29 13.00
64.29 14.00
0.06
0.07
0.07
0.08
0.08
0.08
0.08
0.08
0.08
0.09
0.09
7.00 0.43 4.71 52.06 4.34 13.02 1.08
7.00 0.47 4.30 55.62 4.63 11.12 0.93
7.00 0.50 4.04 59.05 4.92 9.84 0.82
7.00 0.53 3.86 62.34 5.20 8.91 0.74
7.00 0.55 3.73 65.51 5.46 8.19 0.68
7.00 0.56 3.63 68.55 5.71 7.62 0.63
7.00 0.57 3.55 71.48 5.96 7.15 0.60
7.00 0.58 3.49 74.30 6.19 6.75 0.56
7.00 0.59 3.43 77.03 6.42 6.42 0.53
7.00 0.60 3.39 79.66 6.64 6.13 0.51
7.00 0.61 3.35 82.22 6.85 5.87 0.49
Using this above analysis with the Clark Y airfoil data generated a wing planform very similar to last year’s design. This is the most efficient wing which will provide adequate lift and have a wingspan less than 5 feet to fit in the vehicle’s cargo area. So if a collapsible wing were feasible, efficiency could be increased by using a larger aspect ratio. Using a multiple piece wing would increase the weight of the design at the joint and create a failure point where the carbon fibers are discontinuous. However, a longer wing would allow for a greater aspect ratio without losing wing area. The maximum lift coefficient would increase and the drag coefficient would decrease which would allow for more efficient cruising conditions and higher maximum payload.
Page | 30
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
NACA 4414
Weight, lbs
Cruise
Velocity, ft/s
Aspect
Ratio dCL/d_alpha,
CL/deg
Alpha, degrees
Steady
State
C_L
S,
Wing
Area, ft^2 b, wingspan inches b in feet c, chord inches c in feet
64.29 4.00
64.29 5.00
64.29 6.00
64.29 7.00
64.29 8.00
64.29 9.00
64.29 10.00
64.29 11.00
64.29 12.00
64.29 13.00
64.29 14.00
0.06
0.07
0.07
0.08
0.08
0.08
0.08
0.08
0.08
0.09
0.09
8.00 0.49 4.12 48.70 4.06 12.18 1.01
8.00 0.54 3.76 52.02 4.34 10.40 0.87
8.00 0.58 3.53 55.23 4.60 9.21 0.77
8.00 0.60 3.37 58.32 4.86 8.33 0.69
8.00 0.62 3.26 61.28 5.11 7.66 0.64
8.00 0.64 3.17 64.12 5.34 7.12 0.59
8.00 0.66 3.10 66.86 5.57 6.69 0.56
8.00 0.67 3.05 69.50 5.79 6.32 0.53
8.00 0.68 3.00 72.05 6.00 6.00 0.50
8.00 0.69 2.97 74.52 6.21 5.73 0.48
8.00 0.69 2.93 76.91 6.41 5.49 0.46
Using an airfoil with greater camber would have a positive effect on the low speed characteristics of the wing. The 2D lift slopes for the Clark Y and NACA 4414 are the same, but the NACA 4414 has a lower 𝛼
𝐿=0
which means at the same angle of attack the 4414 will generate more lift and has a higher maximum lift coefficient. The camber of the Clark Y is approximately 3.5% and the NACA
4414 has a camber of 4%. While producing more lift the NACA 4414 also is thicker and would increase the wing weight because of volume and increases drag due to greater drag due to lift.
Increasing the drag at steady state cruise will increase the power required if the planform is not modified accordingly to decrease the induced drag. As can be seen in the table above using the
NACA 4414 would allow for a smaller chord still with a wingspan less than 5 feet, increasing the aspect ratio.
If a two piece wing structure was selected adding dihedral to the wing planform would be beneficial in providing lateral stability. Increased lateral stability would decrease the load on the stabilization system and pilot. Winglets could provide the same effect, but possibly to a lesser degree. Winglets would allow the current wings to be retrofitted and the wing design would not necessarily have to be changed.
Page | 31
Requirements Weight
Increase
Aspect
Ratio
Increase
Span,
Sectioned
More
Tapered
Wing
Higher camber airfoil
Winglets
Boundary
Layer/Stall
Control
Weight
Manufacturabi
7
5
9
Compatibility 7
Cruise Velocity 7
Durability 6
Total
6
6
284
7
8
6
9
6
6
9
5
9
5
281
7
5
7
7
6
6
264
7
4
4
6
4
6
211
8
6
9
9
8
7
328
10
7
6
9
6
8
312
Page | 32
FALL 2009 SEMESTER PLAN
WORK BREAKDOWN STRUCTURE
Create prototype
Inventory/Order Prep
Material Lead Time
Assembly
Video System
Prepare Aircraft for Flight
Flight Tests
Evaluate Video System in Lab
Research Alternative Camera Systems
Finalize Design and Order New Parts
Integrate New Video Parts
Improve Wiring of Electrical Components
Rewire Electrical Components
Document Wiring
Improve GPS Back-Up System
3-D Compass
Research Compasses and Order Part
Integrate Compass
Integrate AGL Sensor
Video Transmission Range
Conduct In-Flight Range Tests
Conduct Video Transmission Range Lab Tests
Research Alternative Video Transmission Systems
Finalize Design and Order New Parts
Integrate New Video Transmission Parts
Launch System Testing
With a tennis ball or t-shirt
With a dummy airplane
With essential flight systems
Full Systems Test
Computer Modeling of Airplane Dynamics
Wind Tunnel Testing for Dynamic Coefficients
Derivation of 6 Degree of Freedom Dynamic Model
Creation of Model in Simulink
Design of Feedback Control System
Determine PID Loops to be Used
Integrate Control System with Airplane Model in
In-Flight Control System Gain Tuning
Totals:
10
5
10
10
10
10
10
10
10
5
Scott Strong Jordan Lee David Snyder Peter Hodgell
10
10
10
10
15
10
10
5
5
5
5
5
10
10
10
10
10
10
10
10
10
10
5
10
10
15
5
5
5
5
15
10
10
5
10
10
10
10
10
110 110 110 110
Page | 33
Create prototype
Inventory/Order Prep
Material Lead Time
Assembly
Video System
Prepare Aircraft for Flight
Flight Tests
Evaluate Video System in Lab
Research Alternative Camera Systems
Finalize Design and Order New Parts
Integrate New Video Parts
Improve Wiring of Electrical Components
Rewire Electrical Components
Document Wiring
Improve GPS Back-Up System
3-D Compass
Research Compasses and Order Part
Integrate Compass
Integrate AGL Sensor
Video Transmission Range
Conduct In-Flight Range Tests
Conduct Video Transmission Range Lab Tests
Research Alternative Video Transmission Systems
Finalize Design and Order New Parts
Integrate New Video Transmission Parts
Launch System Testing
With a tennis ball or t-shirt
With a dummy airplane
With essential flight systems
Full Systems Test
Computer Modeling of Airplane Dynamics
Wind Tunnel Testing for Dynamic Coefficients
Derivation of 6 Degree of Freedom Dynamic Model
Creation of Model in Simulink
Design of Feedback Control System
Determine PID Loops to be Used
Integrate Control System with Airplane Model in
In-Flight Control System Gain Tuning
10
10
10
5
10
10
10
5
Aidan Rinehart Matt Krajewski Tyler Fast Eric Villhauer
5
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
5
10
10
10
10
10
10
5
5
10
10
10
10
10
10
10
10
10
5
10
10
10
5
Totals: 110 110 110 110
Page | 34
Create prototype
Inventory/Order Prep
Material Lead Time
Assembly
Video System
Prepare Aircraft for Flight
Flight Tests
Evaluate Video System in Lab
Research Alternative Camera Systems
Finalize Design and Order New Parts
Integrate New Video Parts
Improve Wiring of Electrical Components
Rewire Electrical Components
Document Wiring
Improve GPS Back-Up System
3-D Compass
Research Compasses and Order Part
Integrate Compass
Integrate AGL Sensor
Video Transmission Range
Conduct In-Flight Range Tests
Conduct Video Transmission Range Lab Tests
Research Alternative Video Transmission Systems
Finalize Design and Order New Parts
Integrate New Video Transmission Parts
Launch System Testing
With a tennis ball or t-shirt
With a dummy airplane
With essential flight systems
Full Systems Test
Computer Modeling of Airplane Dynamics
Wind Tunnel Testing for Dynamic Coefficients
Derivation of 6 Degree of Freedom Dynamic Model
Creation of Model in Simulink
Design of Feedback Control System
Determine PID Loops to be Used
Integrate Control System with Airplane Model in
In-Flight Control System Gain Tuning
Totals:
5
10
10
10
5
10
10
10
Tim Jacobs
15
5
10
10
110
10
10
5
10
Dan Jason Jason Ekstrand Matt Stemper
10
10
10
10
10
10
10
5
10
10
10
10
10
10
10
10
10
15
10
10
10
5 10
15
15
15
15
10
110 110 110
Page | 35
RESOURCE REQUIREMENTS
Resources Required for One Aircraft*-(electronics/motors will be shared between aircrafts)
Bill of Materials
(1 Aircraft)
Quantity Vendor Category Part
$272.00 1 GraphiteStore.com Carbon Tube
$167.97
$18.99
$26.97
$15.00
$1.20
3 yards Soller Composites
1 yard Soller Composites
3 yard Soller Composites
1 of each ACE Hardware
2 ACE Hardware
Carbon Fiber
Kevlar
Fiber Glass
30 min
Epoxy/Hardener
Wing T-Nuts
1” IN/1.12”, OD 72” long carbon tube
3 yard by 40’’ piece of carbon fiber material
1 yard by 50’’ piece of Kevlar
3 yard by 38’’ piece of Fiber
Glass
1/4” X 20 thread
$3.00
$6.00
$8.00
$4.00
$3.00
5
2
3
1
1
ACE Hardware Avionics T-Nuts
Hobby Lobby
Country Plastics
Tail Balsa Wood
Hobby Haven Aileron Balsa Wood
Firewall
24 thread
Hobby Lobby Internal Balsa Wood Strips for T-Nut Connections
4” X 36” ¼ inch sheets
1’’ X 36’’
3.5’’ X 3.5’’ X .5’’ Polycarbonate
$240.00
$360.00
$5.00
$8.00
$3.60
$3.00
$5.00
$18.00
$3.00
$23.45
$6.00
$14.00
$28.00
$12.00
Total Cost
1
4
2
1
6
5
1
3
3
5
1
2
1
2
$895.18
ACP Composites Spider Foam
Horizon Hobby Metal Gear Servos
ACE Hardware
ACE Hardware
U-Straps
Aluminum
Lowe’s
Lowe’s
Industrial Velcro
Duct Tape
Digital Mini MG Servos
Bag of ¾ inch plastic pipe
1/8 th straps
ACE Hardware Nylon Bolts
ACE Hardware Avionics Nylon Bolts
¼’’ X 20 bolts
10 X 24 bolts
N/A
ACE Hardware
Hobby Haven
U-Channel Aluminum 1’’X 0.5’’, only need 6’’ long
Spray Paint
Control Horns visibility
Tower Hobbies Propeller (+ extras)
Lowe’s Dowel (Launch
14 X 10 Propellers
1’’ Dowel Rod
1’’ X 3’’ strips
15’ strip (Don’t need this together
Page | 36
Auxiliary Material Resources
Material
Camera
Cost
$200.00
Remote Control $340.00
Total Cost $540.00
RC
Transmitter/Receiver
Spectrum DX7
Package
Repair Cost Estimation
Material
Carbon Fiber
Hardware
Electronics
Total Cost
Cost
$200
$50
$500
$750.00
Nylon bolts, ubrackets, hinges
Servos, gears, propulsion batteries
Labor Costs
Member
Scott Strong
Jordan Lee
David Snyder
Peter Hodgell
Aidan Rinehart
Matt Krajewski
Tyler Fast
Hours: Labor @ $20/hr
160 $3,200.00
160 $3,200.00
160
160
160
160
160
$3,200.00
$3,200.00
$3,200.00
$3,200.00
$3,200.00
Eric Villhauer
Tim Jacobs
Dan Jason
Jason Ekstrand
Matt Stemper
160
160
160
160
160
$3,200.00
$3,200.00
$3,200.00
$3,200.00
$3,200.00
Peter Sherman (advisor) 25
Cory Tallman (industry professional) 10
$1,250.00
$1,000.00
Total $40,650.00
Total Cost
The total predicted cost for this project is projected to be $42835.18
Page | 37
FALL 2009 MILESTONES AND SCHEDULE
Milestones
D01- Project Plan–Sept 25th, 2009
D02- Launch system verified—Oct 25, 2009
D03- Simulink airplane model complete–Oct 31, 2009
D04- Additional prototype body–Nov 18, 2009
D05- Simulink control system complete–Nov 29, 2009
D06- Testing of airplane and launch system–Dec 1 , 2009
D07- New video system installed—Dec 1 , 2009
D08- Final report –Dec 2, 2009
D09- Complete positive identification test with camera system – February 15, 2010
D10- Reduce total system weight to 10 lbs – March 15, 2010
D11- Achieve a predetermined flight path under full auto pilot – April 15, 2010
D12- Resolve an assault type weapon under autonomous flight – May 1, 2010
Page | 38
Fall 2009 Schedule
Page | 39
