System to Remotely Transport and Deploy an

Unmanned Helicopter

Submitted to: Dr. Paul Oh

The Senior Design Project Committee

Mechanical Engineering and Mechanics Department

Drexel University

Team Number: MEM-10

Team Members:

Jason Collins (MEM)

Michael Perreca (ECE)

Caitlyn Worthington-Kirsch (MEM)

Submitted in partial fulfillment of the requirements for the Senior Design Project

May 19, 2008

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Abstract

Despite the recent increase in the use and design of unmanned aerial vehicles (UAVs),

methods of remotely transporting and protecting these valuable pieces of equipment has

gone largely untouched. We have designed and built an enclosed trailer system that can be

used to transport and aide in the launching of UAVs. Combining suspension, leveling and

actuation systems, our design can be incorporated into previously designed autonomous

vehicles and allow for safe transport of a UAV to a specified site while protecting it from

outside dangers, as well as maintaining a level base for safe takeoffs and landings. This

system is designed to be user friendly and is easy to actuate locally or remotely. Our

project was culminated in fully successful testing of the prototype trailer. Videos of the test

launch may be viewed at http://dasl.mem.drexel.edu/SeniorDesign07%2D08/public/.

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Table of Contents

Abstract 2

Introduction 4

Problem Description 4

Constraints on Solution 5

Design Decisions 6

Prototype Fabrication 9

Data Acquisition and Actuation Electronics 14

Testing Results 19

Economic Analysis 21

Project Timeline 22

Teamwork Analysis 22

Social, Ethical, and Environmental Impacts 22

Conclusions 23

Appendix A: Leveling System Test Data 24

Appendix B: Approved Purchase List 25

Appendix C: Gantt Chart 26

List of Figures

Figure 1: The vibration control system 8

Figure 2: Gimbal brakes during testing 10

Figure 3: The completed gimbal, without the counterweight 11

Figure 4: The helicopter on the gimbal, stabilized 11

Figure 5: The gimbal and suspension system mounted on the trailer 12

Figure 6: The latch and linkage mounted to the gimbal 13

Figure 7: The completed enclosure frame, open 13

Figure 8: the completed trailer, with the enclosure frame closed 13

Figure 9: The fully enclosed trailer 14

Figure 10: Two Bosch-Style SPDT Relays Wired as an H-Bridge 15

Figure 11: LabVIEW Graphical User Interface 17

Figure 12: A local user using the break out box 19

List of Tables

Table 1: Threshold and Objective Requirements 5

Table 2: Trade Study for Vibration Control System 7

Table 3: Trade Study for Controller System 8

Table 4: Trade study for Enclosure Design 9

Table 5: Cost Breakdown 21

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Introduction

Our goal was to design and build a trailer capable of safely carrying a UAV (Unmanned

Aerial Vehicle) over rough terrain to the designated launch point, and then safely releasing

the helicopter for launch. This would allow workers to effectively use a UAV helicopter

without endangering themselves. In the fall quarter, we designed the trailer, including a

gimbal, a suspension system, an enclosure, and a remote actuation system for the trailer.

We also built two proof-of-concept scale models of parts of the planned trailer, in order to

reduce the risk of going forward with the project. At the beginning of the winter quarter we

assembled a purchase list. We have since built the trailer system, encountering few major

setbacks, and keeping the project under budget. We have done a successful test of the

system, by using the trailer to carry the UAV to the launch site, remotely preparing for

launch, and remotely launching the UAV helicopter.

Problem Description

In an emergency, it may be vital to gather information in an environment that is dangerous

to human rescue workers. An unmanned aircraft, such as a UAV (Unmanned Aerial Vehicle)

helicopter, is increasingly valuable for a search and rescue operation: sensors on the aircraft

can locate trapped victims, or find the extent or source of the damage, or determine the

stability and strength of involved buildings, or locate obstacles and paths around them, all

without exposing emergency workers to dangerous environmental conditions. Armed with

the information provided by the unmanned aircraft, emergency workers can work efficiently

to rescue victims and contain the emergency, without spending unnecessary time in

dangerous conditions, and with a reduced risk of being trapped or stopped by obstacles.

However, a UAV helicopter must be launched. At present, all solutions available on the

open market require the operator to be at the launch site in order for the helicopter to be

launched. This means that the helicopter must either be launched outside the dangerous

area, which may limit the distance it can cover and the quality of information it can supply,

or the operator must venture inside the dangerous area in order to launch the UAV

helicopter. Neither solution is optimal.

We have therefore designed and built a method of remotely launching a UAV helicopter,

and built a prototype of our design. The launching apparatus and helicopter will be towed to

the launch site by a remote-controlled ATV, such as D.I.A.S I or II (Drexel Integrated ATV

System) and the launching apparatus will protect the helicopter while it is being towed.

Once at the launch site, the barrier protecting the helicopter will be automatically removed,

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the launch pad will move to a level position and be clamped in place, the helicopter will then

be ready to launch.

Constraints on Solution

Constraints for this project include the need for the trailer to fit into our available

workspace, but accommodate and support a UAV helicopter carrying its full capacity of

observational equipment. The helicopter must be protected during transit over any terrain

accessible to the ATV used to pull it, and the platform supporting the helicopter must be

level in order for the helicopter to be launched. The weight of the platform along with the

weight of the helicopter must be an acceptable payload for the ATV that tows the

apparatus. Table 1, below, details the threshold and objective goals for the project.

The towing strength of the 90cc DIAS2 could not be determined from the available ATV

literature. We therefore tested DIAS2 towing various weights on a variety of slopes. We

determined that DIAS2 could tow 850 pounds on flat ground.

Requirement Threshold Objective

Size fit through double doors Fit into standard storage pod

Minimum towing vehicle 90 cc ATV 350 cc ATV

Protect UAV during

transport Dirt road Off road

Launch prep time 2 Minutes 1 Minute

Weather protection

Shield contents from light

precipitation Shed steady rain

Launch angle of UAV

Safe angle for human pilot

+/- 5 degrees +/- 2 degrees

Able to carry 3 foot rotor, 15 lbs 6 foot rotor, 35 lbs

Table 1: Threshold and Objective Requirements

The trailer must have both manual and remote operation controls. The trailer must protect

the helicopter from rain or low tree branches, as well as from vibrations and instability

caused by transit over rough terrain and other obstacles. The helicopter must be supported

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so that it does not move within the trailer during transit. The trailer must be able to

accommodate the size and safely support the weight of the fully-loaded helicopter. The

loaded trailer must not be too heavy for the ATV to easily pull.

The helicopter platform must remain level independent of the trailer and within the launch

tolerance of the helicopter. The UAV must be deployable within 2 minutes after reaching

the launch site. The controls must be easily understood by rescue workers, easily

manipulated, and legible in low visibility conditions.

The trailer must be able to survive use through rough terrain and expected obstacles. The

manufacture cost must be less than the cost of the helicopter. The trailer and controls must

be field serviceable if the equipment breaks down.

Design Decisions

In order to design the trailer we needed to determine the best way to protect the helicopter

from vibration, to keep the helicopter level, to protect the helicopter from damage during

transit, and to control the trailer. We also needed to determine the best source for the

trailer.

We chose to use a gimbal and an innovative vibration control system, consisting of a

compressible ball between two bowls, to protect the helicopter from vibration and

movement. An outer cover made of strong fabric would protect the helicopter during

transit, and then fold back to allow the helicopter to launch. A National Instruments

Compact RIO would be used to control and monitor various functions and sensors of the

trailer system. The trailer would be a 56" x 55" deck over a trailer base sourced from a

local manufacturer.

In order to keep the helicopter level, we designed a gimbal with a counterweight to fit the

helicopter landing gear. A gimbal is a proven method for allowing free rotation of an object,

and the counterweight would ensure that the helicopter remained level. The inner frame of

the gimbal, with the helicopter mounted on it, would move independently of the outer frame

and the trailer, protecting the helicopter from tilting if the trailer encountered hills or

obstacles.

The outer frame of the gimbal would be mounted on a vibration control system, in order to

protect it from vibration. At first we considered a classic spring-dashpot system, or a

simpler system with springs but no damping, to reduce vibration. However, it was also

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necessary to protect the helicopter from sideways sliding or twisting movements, and to

reduce complexity and size we chose to combine these functions. A separate device to

allow sideways movements could make the overall structure very heavy and far more

complicated. This led to the idea of allowing the spring and dashpot to pivot and shift

horizontally, allowing for sideways and twisting movement. Another alternative would have

been multiple spring-dashpot systems, one for each axis. However, the system would have

a lower part count and be far more stable if we used a spherical system: a compressible

rubber ball. In order to force the ball to return to the center of the system, we made the

plates above and below it into curved bowls. This final design would, in theory, allow the

system to adapt to more movements than a spring-dashpot system could. In order to be

certain this would work, we built and tested a proof-of-concept demonstrator.

Spring-dashpot system Bowl-ball system Spring system

Allows for expected movement: 30%

5% 30% 5%

Ease of implementation and tuning: 20%

15% 10% 15%

Limits Vibration: 50%

50% 40% 40%

Total 70% 80% 60%

Table 2: Trade Study for Vibration Control System

Table 2 shows the trade study to determine the vibration control system. We considered

three systems: a classic spring-dashpot damper, a spring damper without a dashpot, and an

innovative design consisting of a rubber ball between two bowls, mounted at the four

corners of the helicopter platform. The bows would be further connected by springs or

cords to prevent them from separating and allowing the ball to escape. This last system

would be harder to calibrate and is associated with greater risk, but it would allow for more

twisting and turning movement than the more traditional solutions. In order to reduce risk

further, we have assembled a proof-of-concept model of the system, to demonstrate that

the design does work. Having tested the model, we determined that it transmits

approximately 5% of ground vibration, a substantial reduction which will protect the

helicopter during transit. Figure 1, below, shows the system moving both horizontally and

vertically.

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Figure 1: The vibration control system at rest, shifted horizontally, and compressed vertically

While the vibration control system was being designed, it was also necessary to consider

what system to use to control the trailer. The system would need to control the opening

and closing of the trailer enclosure, and to control the restraints that hold the helicopter in

place during transit. Several controllers were suggested, the IFI Controller, the

Lynxmotion, the Pololu, and the NI Compact RIO.

IFI Controller Lynxmotion Pololu NI Compact RIO

Availability (20%) 20% 10% 15% 17%

Voltage System (5%) 5% 5% 5% 2%

Learning Curve: Software (15%)

10% 10% 5% 5%

Learning Curve: Hardware (10%)

10% 7% 7% 10%

Cost (10%) 10% 9% 10% 5%

Communications (20%) 10% 10% 10% 20%

Known Issues (20%) 5% 10% 10% 15%

Total (100%) 70% 61% 62% 74%

Table 3: Trade Study for Controller System

Table 3 documents the alternative controller systems we considered. The readily available

controllers were evaluated for availability, the voltage system each used, their usability,

cost, and the presence of any known issues, including size, limited inputs and outputs, and

the likelihood of overheating problems. In the end, we determined that the NI Compact RIO

would be the best choice for a controller.

Choosing the trailer was also a major decision. The trailer had to be narrow enough to fit

through the doors of DASL, and had to support the weight of the enclosure and helicopter

pad.

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Hard cover over trailer

Hard cover on gimbal

Soft cover

Price (15%) 10% 5% 10%

Weight (10%) 5% 5% 10%

Complexity (15%) 10% 5% 15%

Protection from environment (30%) 30% 30% 20%

Protection from UAV hitting cover (30%)

10% 20% 30%

Total (100%) 65% 65% 85%

Table 4: Trade study for Enclosure Design

When choosing the trailer base, we had several alternatives. We could purchase a very

basic trailer designed for an ATV, consisting of a platform mounted on the wheels and hitch

needed for the ATV to tow the trailer. Table 4, above, describes the choice enclosure. On

the platform we could construct either a solid box, or a folding fabric enclosure. The solid

box would provide better protection, but would be harder to operate smoothly, and would

be much heavier than a fabric enclosure. The soft material might not provide perfect

protection, but would be simpler to design and would operate more smoothly. We could

also purchase a custom trailer complete with a solid box enclosure, which would require

fewer man-hours from the team and would be more precisely made, but would be more

expensive and would be less adaptable for later additions. A final solution would be to build

the entire trailer ourselves, which would require more man-hours from the group but would

be more adaptable.

Prototype Fabrication

At the start of the winter quarter, we had our complete preliminary purchase list. The total

cost of the material we wanted to buy came to about $10,000. Our adviser asked if we

could reduce this, naturally. Most of the costs were expected, but the gimbal brakes were

very expensive, costing about $2,600 total. We decided to take a week to consider other

alternatives. After playing with a few ideas, we realized that disk brakes from a bicycle

might work, at a fraction of the cost. We therefore changed our purchase list to use bicycle

brakes rather than the original gimbal brakes, and planned to build the gimbal first so that

the brakes could be tested early. If they did not work, we might have to go back to the

expensive brakes. The new purchase list had a total cost of $8128.55, and our adviser

approved this.

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With the budget approved, we placed orders for the needed parts. Once they came, we

immediately started work on the gimbal. The gimbal is constructed out of 8020 aluminum

beams, and we found it easy to work with. It took a bit of experimenting to determine how

to mount the brakes on the gimbal, but we soon determined a workable solution and were

able to test the brakes. The mounted brakes are shown in Figure 2, below. Initially it

looked like the brakes would work, but the axles they were mounted on did not spin freely,

so we could not be certain. Eventually the holes that held the axles had to be widened

slightly, and we were able to determine that the brakes would work well for our trailer.

Figure 2: Gimbal brakes during testing

Once the brakes were tested we could finish the gimbal (shown in Figure 3, below). The

counterweight was mounted below the center bar of the gimbal, and the gimbal was tested

to make sure it could easily bear the weight. Next we designed and installed the rails that

would hold the landing gear of the helicopter, so that the helicopter could safely sit on the

gimbal. These were made of angled aluminum stock, lined with rubber cushions to protect

the landing gear. Once the helicopter could rest on the gimbal, we were able to adjust the

position of the counterweight so that the helicopter would be held level (Figure 4, below,

shows the helicopter resting on the completed gimbal). The position of the counterweight

can be adjusted further if different sensors and parts mounted on the helicopter change the

center of gravity of the helicopter.

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Figure 3: The completed gimbal, without the counterweight

Figure 4: The helicopter on the gimbal, stabilized by the counterweight and landing gear rails

This done, we started constructing the rest of the trailer. The suspension system didn't

require much assembly, but we did have to cut the stainless steel bowls to the right size, a

process that was more difficult than we anticipated. Eventually an angle grinder was used

to make the cuts. The edges were very sharp and jagged, so we decided to order liner to

go on the edges. This purchase was not on our original purchase list, but was well within

the discretionary funds our adviser had allowed for unforeseen needs. The size and weight

of the gimbal had raised questions about whether the rubber balls would be able to support

the weight of the gimbal without bursting. In order to test this, one group member began

applying weight to one of the balls. Eventually he put the ball on the floor and stood on it,

which led us to conclude that the balls could easily support the weight of the gimbal,

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helicopter, and counterweight.

While the bowls were being cut, we began adapting the trailer base. More 8020 stock was

used to elongate the platform of the trailer, so that the entire helicopter could be enclosed.

The suspension system was mounted onto the trailer, and the gimbal installed on top of the

suspension, after a hole had been cut in the original trailer platform to allow the

counterweight to swing. The gimbal and suspension system can be seen mounted on the

trailer in Figure 5, below. While the gimbal was being built, we also prepared the ATV to

tow the trailer. This ATV does not come with a trailer hitch, because the manufacturer

intended it to be a child's ATV. We had previously tested the towing capacity of the ATV,

and now we commissioned the Drexel Machine Shop to build a trailer hitch for the ATV.

Figure 5: The gimbal and suspension system mounted on the trailer

We next designed and built the latch that would hold the landing gear in place during

transit. The latch design had been roughly outlined during the fall quarter, and in this

quarter the design was refined so it could be built. A motor was mounted to the center

strut of the gimbal, and we built a linkage to use the motor to turn the latches that would

hold the helicopter in place. The linkage was initially built out of angled aluminum stock,

but the angle made the assembly difficult, and we chose to replace several pieces with flat

aluminum straps. The longest pieces in the linkage were left as angled aluminum, to

prevent bucking, as were the bars that hold the helicopter in place. The latch was carefully

designed to keep the pieces from twisting or buckling rather than turning properly. Once

the latch was working well, we wired the latch actuation system and tested it. The latch

and actuation linkage are pictured in Figure 6, below.

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Figure 6: The latch and linkage mounted to the gimbal

The final step was to build the enclosure. We had repeatedly discussed how the folding

upper part would be built, and we finally decided on two halves with fixed right angle bends

in them, rather than the accordian folding frame we had planned during the fall semester.

The fixed design would be more robust, and simpler to actuate. We built the frame and

installed it, making sure that the hinges worked smoothly. The frame is shown in its open

and shut positions in Figures 7 and 8, below.

Figures 7 & 8: The completed enclosure frame, open and closed

Once the enclosure frame was assembled, we measured the dimensions needed for the

fabric covering, bought the necessary rip-stop nylon, and took the fabric and our

measurements to a seamstress. We deliberately increased the measurements slightly, so

that the fabric would fit loosely. This was because the fabric pattern was a fairly high-risk

part of the project, as none of us had significant experience in this area. Planning for a

loose fit mitigated the risk, as a loose covering would still adequately protect the UAV.

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The seamstress took longer than we had anticipated to deliver the enclosure covering, so

while we waited we tested the suspension and leveling systems (see Testing, below, for

more details). Once the covering arrived, we added pieces of 8020 angle to the top of one

of the enclosure sides, to keep rain from falling through the space between the doors. We

installed the fabric covering, using a combination of 8020 bolts and nuts and plastic zip-ties

to secure it. The finished trailer may be seen in Figure 9, below.

Figure 9: The fully enclosed trailer

Data Acquisition and Actuation Electronics

For the electronics portion of the project, we chose to use the National Instruments

Compact RIO. This system allows for data acquisition as well as device manipulation

through its c-series module system. The base RIO system used is the cRIO 9012. This

system allows for on-board data manipulation from our sensors as well as the ability to

actuate our motors and linear actuators that are required for our latching, braking and

enclosure sub-systems. All of the programming for the compact RIO is being performed in

National Instruments LabVIEW, specifically LabVIEW 8.5.

We have chosen to use two of their c-series modules on top of the standard Compact RIO

system. The two modules are the NI 9205 and the NI 9476. The NI 9205 is a 32 channel

analog input module. It allows for an analog signal input of ± 10V DC with 16-bit

resolution. These inputs allows for potentiometers, reed switches and momentary switches

to be imported into our labVIEW VI to determine the status of the system. The NI 9476 is a

32 channel digital output. With the ability to output 6 – 36V DC as our “Hi” and ground to

be our “Low”, the 9476 allows for control of status LEDs, relays, and motor controllers.

Each channel has a maximum current output of 250mA but outputs can be paralleled to

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increase the current output for devices that require it.

The brake portion of our system is actuated through the use of 2 SPDT Bosch-style

automotive relays and a 50kΩ potentiometer for each braking axis. The relays are wired to

function as an H-Bridge motor controller. Shown in Figure 10, the relays allow for a single

input to rotate the motor in one direction as well as another input to have the motor rotate

in reverse. Our original plans were to use solid state relays to power the motors. This

would possibly allow us to pulse the motor to have more flexibility in terms of braking

force. Unfortunately due to a misunderstanding in the suppliers catalog, the wrong solid

state relays were ordered and only function with an AC source and load. The automotive

relays were used in place of the solid state relays due to their lower cost and availability.

For future work it is recommended to replace the mechanical relays with solid state relays

due to the longer life expectancy of the solid state relays.

Figure 10: Two Bosch-Style SPDT Relays Wired as an H-Bridge

The compact RIO’s 9205 module has an input from the 50kΩ potentiometer mentioned

above to determine the status of the brake calipers. At the push of a button on the VI or a

momentary switch externally, the program will determine the current status of the brakes

(either enabled or disabled) and engage the motors until the potentiometers have reached a

certain value. Currently, this style of engaging/disengaging the brakes has proven to be

quite useful and the braking force can be adjusted just by changing the value in the

programming. On top of the standard brakes engaged/disengaged status is the addition of

a dampened braking status. This status allows for added protection against shocks during

transit. The dampened status is controlled once again by a push button on the LabVIEW VI

as well as the break out box. Once the dampened status is engaged, the only available

toggle feature is to disengage the dampened status. The brakes will then be set back to

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their engaged or disengaged status depending upon what they were at before dampening

was applied.

With the helicopter resting safely on the runner supports on the center layer of the gimbal,

increased steps must be taken to make sure that the helicopter can not be bumped off in

the presence of rough terrain. A motor driven latch system has been implemented to

prevent this from occurring. Like the brakes, Bosch-style SPDT relays were chosen power

the motor as an H-Bridge. Unlike the brakes though, SPDT micro switches are used to

determine the current status of the latch. Two micro switches are used on each latch. They

are configured such that they will give the user a status as to whether or not the latch is

engaged. At the push of a button on the VI or again with a momentary switch, the VI

determines the current state of the latch and rotates the motor the required way to change

its state. Though the current programming only relies on the input of one latch’s switches

to stop the motor, the VI shows the status of all four switches. Those four switches

determine if the left latch is locked and unlock as well as the right latch is locked in

unlocked. A switch at each state is crucial due to the ability for the latch system to “slip.”

If only one of the latch portions become unlatched instead of both, it would cause a

complete failure of a helicopter launch as the helicopter would tip over. This simply can not

be able to occur.

With all of the systems completed, the final portion of the wiring was directed towards the

enclosure. To enclose and open the trailer, four linear actuators were installed, having one

at each corner. Each linear actuator has a built in potentiometer as well as built in limit

switches. The built in potentiometers are used to monitor the current state of the enclosure

and the limit switches were used to prevent any over extension or compression of the

actuators which may cause damage to them. To actuate the linear actuators, SPDT relays

were used once again. A total of 8 were used to actuate all four corners, or two per corner.

Though the compact RIO has been an almost straight forward device, some issues have

arisen. The first of these issues are with the 9205 input module. If any inputs are called

upon in the program but left floating, the program appears to have a misunderstanding as

to what the actual status of the input currently is. This would cause the brakes or the latch

to actuate on their own instead of waiting for the external momentary switch or the button

in the VI. To remove this problem, a 10kΩ pull down resistor was put at each momentary

switch input on the 9205. This fixed the problems associated with a floating input. The

same occurred with the normally closed connector on the micro switch. Unlike the

momentary switch inputs, these terminals were put straight to ground as there should never

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be a situation in which the high voltage of the micro switch sees it.

For our power requirements, we have chosen to use two 12V sealed lead acid batteries with

21Amphour outputs. The batteries chosen, model number PSH-12180FR from Power-Sonic,

were used in a previous project by two of the group's members and has performed well

under rough conditions. This 12 volt system powers the compact RIO as well as the linear

actuators. For better control of the braking a 12 to 6 V DC to DC step down converter was

used to lower the speed of the motors but still maintain their high torque. These 6 volts is

also used to provide any voltage for potentiometers and switches as the 9205 input module

is limited to ±10V. The use of the 6V source prevents there being a situation where a

voltage exceeding its limits can be applied.

LabVIEW User Interface

Figure 11 shows the LabVIEW GUI that the remote user would see when operating the

trailer.

Figure 11: LabVIEW Graphical User Interface

The GUI is broken up into sections based upon their functions. On the left side of the

screen is the “Brakes” section. This section shows the current status of the potentiometers

on each axis as well the limits for toggling between each setting. The user has the ability to

adjust the upper and lower braking limits which determine the amount of braking applied

when the brakes are engaged as well as the limit which the brakes are considered to be off.

This section also allows for the user to engage and disengage the dampening as well as set

the limit that is considered to be dampened.

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The top portion of the GUI contains the “Latch” section. In this section, the user has the

ability to monitor each latch and determine if the current system status is correct or not. As

previously mentioned, the code is set to stop the latch motor once one side has engaged.

Though they are timed to trip the micro switches at the same time, if a switch is not tripped

due to the latching mechanism failing, the remote user will know this and will not attempt to

launch the helicopter without determining why there is this error.

The center section of the GUI contains the “Enclosure” section. Like the other sections,

there are monitors for the built in potentiometers of each corner. Once again, the user has

the ability to adjust the limits for each corner. It is recommended that corners A and C

have the same limits as well as B and D have the same limits as they actuate the same side

of the enclosure. Failure to have limits that are similar may cause binding issues and could

damage the enclosure or the linear actuators.

The lowest portion of the GUI is the switch monitor for the “break out box.” As the

breakout box consists of four momentary switches to engage different features, the remote

user can see if they are being pressed as well as set their sensitivity. Too low of a

sensitivity may cause false positives of a switch being pressed and engage or disengage a

feature that may cause damage to the system, UAV or local user. It is recommended that

these limits not be adjusted.

The final portion of the GUI shows the current active outputs of the entire system. All

functions are easily visible and arranged by their action. All of the enclosure outputs (up and

down), the latching outputs and the braking outputs are all shown. This is very useful if

there is an issue with system. If a sensor is reading incorrectly and does not allow for a

status change to jump out of its program loop, the remote user can see what portion of the

system is causing the issue and can aide in the diagnosing and correction of the problem.

Future work on the GUI would be to have an entire kill switch for the system. Currently

there is only one kill switch and it is a physical switch on the trailer at the batteries. This

kill switch would allow the remote user to disable all outputs and prevent any actuation of

the system until it was re-enabled. It also suggested having the ability to actuate any

portion of the system individually, IE have corner “A” go up or down at the push of a

button. This would aide in the determining the correct limits to use as well as if there was

any sort of fine adjusting to the braking or enclosure if necessary.

The “Break Out Box”

As the entire system needs to have the ability to be controlled locally and remotely, a

“break out box” is needed that has the ability to show the local user the current status of all

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the features as well as the ability to change their states. A Radio Shack project box was

used as the main foundation of the break out box. Momentary switches were then used to

engage/disengage braking, enclose/open the trailer, latch/unlatch the UAV, as well as

engage/disengage the dampening. Status LEDs were used to allow the user to determine

what the current state of the system is in. Though many of the features can be determined

just by looking at the trailer, features such as the brakes can not be visually determined

and the break out box would be the best way for the user to determine these statuses. All

of the momentary switches can be turned off to prevent accidental state change during

transportation. Figure 12 shows a local user using the break out box to actuate the features

of the trailer.

Figure 12: A local user using the break out box

Testing Results

Our primary tests were qualitative. We tested each system as it was built, ensuring that it

functioned as it was designed to do. We were able to measure the response of the

suspension and leveling systems, and our testing results are included below. Our final test

was a full run of the system. We took the trailer, ATV, and UAV to a Piasecki Heliport,

where we successfully used the trailer to transport and launch the UAV.

Testing: Leveling Response

To test the leveling system, we displaced the gimbal, allowed it to reach equilibrium, and

measured the final displacement. For the front-back tilt, the gimbal settled at an average of

1.6 degrees from level, with a standard deviation of 0.6 degrees. For the right-left tilt, the

gimbal settled at an average of 1.2 degrees from level, with a standard deviation of 0.3

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degrees. Our testing data can be found in Appendix A. Our project objective was to have

the final angle in any direction to be under two degrees. We therefore succeeded in

meeting our project goal for the leveling system.

Testing: Vibration Response

In order to test the vibration response of the suspension system, we used a video camera to

record the vibration response of the trailer. A yardstick was placed next to the gimbal as a

reference for displacement.

Hooke's Law states that

F=-kx (Eqn 1)

where F is the force applied, k is the spring constant of the system, and x is the

displacement. The weight of the loaded gimbal changed the displacement by 1.5 inches. As

the loaded gimbal weighs approximately 130 lbs, the weight on each ball-bowl system was

approximately 32.5 lbs. The spring constant of the ball-bowl system was therefore 620

labs/ft.

To find the damping constant, c, we must examine the decay of the vibration.

We know that

ln(x1/xn+1)=2πn(E/(1+E2)1/2) (Eqn 2)

and that

E=c/(2(mk)1/2) (Eqn 3)

Where xn and xn+1 are the maximum displacements of successive peaks, m is the mass

of the system, k is the spring constant, and c is the damping constant.

By filling in the known variables, we determined that the damping constant of this system

is approximately 0.511743 lbs-sec/ft.

The amount of vibration transmitted through the is determined by the transmissibility of

the system and may be calculated by

21

(Eqn 4)

where G is the transmissibility, k is the spring constant, w is the frequency of vibration, m is

the mass of the system, and c is the dampening constant.

The mass of the system is 32.5 lbs, as previously stated, and for the frequency we used 5

Hz, as that is the frequency used by the United States Army for testing vehicles for rough

terrain. We used this equation to calculate that the transmissibility of the system is

approximately 0.03, meaning that only 3% of the ground vibration will be transmitted to the

helicopter launch pad.

There are a few areas for error in this experiment. The largest is in the data collection

apparatus: the software available to us to process the files generated by the camera was

limited. However, we are confident that the true transmissibility of the system is less than

the 5% which was our goal. In addition, the rubber ball can be inflated and deflated to

change the transmissibility of the system, so that vibration in the trailer can be properly

managed.

Economic Analysis

Our approved budget for the project totaled $8,128 for all purchases. A rough breakdown

of the cost of materials is included in table 5, below. A full list of items purchased can be

found in appendix B.

Total Expenditures:

8020 stock $1,463

8020 fasteners $932

other hardware $1,081

actuators $614

Electrical $978

NI $282

trailer $820

Enclosure covering $516

Total Expenditures $6,686

Table 5: Cost Breakdown

22

Our total expenditures for the project turned out to be $1,442 less than we budgeted for,

which is a substantial savings. This is largely because we originally thought we would

purchase a $1400 trailer and need to pay another $600 to have it shipped, but we found a

local supplier who built it for $820. Additional savings came from overestimating the cost of

the seamstress work on the enclosure fabric.

There are parts of the structure, the enclosure frames for example, that are made from

much heavier more expensive members than were required. This was done to maintain

consistent beam sizes for design simplicity. If future versions of this system are to be built

the cost and weight could be reduced by sizing the members to their specific loads.

Project Timeline

The fall term was spent on designing the trailer and building and testing proof-of-concept

models for the leveling and suspension systems. A design freeze was in effect in early

January, and we ordered building materials early in the winter term. Building the trailer

took the rest of the winter term and the early part of the spring term. Systems were tested

as they were built to ensure smooth operation. The latter half of the spring term was spent

testing the trailer and refining the actuation system. For full details, see our Gantt chart in

Appendix C.

Teamwork Analysis

The team dynamics have been smooth and functional throughout the project, with each

person contributing strongly in his or her areas of expertise. During the design process,

Jason did most of the AutoCAD work, and planned the majority of the trailer frame. Caitlyn

had previous experience in vibrational analysis, so she focused on validating the innovative

suspension design. She also had more experience in documenting and presenting

engineering projects, so she took the lead in writing deliverables throughout the project. As

the electrical engineer, Mike designed the wiring and actuation systems.

Once the materials arrived, all three worked together to get the trailer built. Once the basic

frame and gimbal were assembled, Caitlyn worked on the latching mechanism and the

patterns for the fabric enclosure, Jason built the enclosure frame, and Mike built the

actuation system.

Social, Environmental, and Ethical Impacts

Remote deployment of UAV helicopters will have many positive impacts on society, by

keeping emergency workers safe and allowing more efficient rescue operations, which will

23

give the victims of such emergencies a greater chance of survival. However, any system

that has good impacts is likely to have potential bad impacts. This system also makes

remote surveillance easier, which may result in invasions of privacy and similar crimes. If

used in war, a UAV launch system such as this one could allow an army to direct its

weapons more effectively.

The effects of this system on the environment are negligible. Trailers are already used to

transport UAV helicopters to their launch points, and automating the trailer does not

significantly add to their environmental impact. In addition, the remote launch system may

allow more efficient response in the case of an environmental emergency.

The system we designed has many potential effects, some good and some bad. In total,

however, the good effects far outweigh the bad effects. There are therefore no serious

ethical problems with the design and manufacture of this system.

Conclusions

As of May 7th, 2008, it was agreed upon by MEM Senior Design team 10 that our project is

a success. On this date, the entire system was tested and it was confirmed that the project

met its goal: to transport a UAV safely over rough terrain and then allow for a safe launch.

Videos of our launch, along with other demonstration videos, can be viewed at the team’s

website at http://dasl.mem.drexel.edu/SeniorDesign07%2D08/public.

Not only was a completed system tested and found working, but all thresholds of our

outlined requirements were met or exceeded. Our trailer was able to be moved inside and

outside of buildings as well as transported through the use of a common rental truck. The

entire system was light enough to be towed by our target vehicle, a 90cc Polaris Sportsman

ATV with a custom hitch. The system also was able to shed rain and protect the electronics

and UAV as during an April 29th demo, inclement weather forced the team to test its

moderate rain protection capabilities.

Though are project can be considered a success, we feel multiple areas can be improved

upon. The enclosure system was highly over-designed and can be simplified through the

use of a smaller building material. The electronics and programming can also be upgraded

to reduce area as well as simplified to aide in mass production. Overall, the entire project

went as planned and has exceeded our expectations.

24

Appendix A - Leveling Sytem Testing Data

levelness - right/left

levelness - back/front

test final tilt displacement (in) angle test final tilt displacement (in) angle 1 right 5/8 0.625 2 1 front 0.31 5/16 .95 2 left 5/16 0.3125 1 2 back 0.31 5/16 .95 3 right 1/2 0.5 1.6 3 front 0.25 1/4 .8 4 left 3/4 0.75 2.4 4 back 0.56 9/16 1.7 5 left 3/4 0.75 2.4 5 front 0.38 3/8 1.2 6 right 3/16 0.1875 .6 6 back 0.44 1/16 1.4 7 left 1/2 0.5 1.6 7 back 0.38 3/8 1.2 8 left 3/8 0.375 1.2 8 front 0.31 5/16 .95 9 left 5/8 0.625 2 9 back 0.50 1/2 1.5 10 right 3/8 0.375 1.2 10 back 0.50 1/2 1.5 average 0.5 1.6 average 0.39 1.2

st. dev. 0.188654 0.603 st. dev. 0.102274 0.315

Appendix B – Approved Purchase List Appendix C – Gantt Chart

Appendix B – Approved Purchase Listunit total

part number source length qty price price

7494A1 McMaster-Carr 1 6.68 6.6885695K1 McMaster-Carr 5 1.78 8.96658K44 McMaster-Carr 8 2.35 18.8

3458 Rankin Automation 16 0.53 8.4862645K42 McMaster-Carr 8 20.85 166.81439K611 McMaster-Carr 300mm 4 31.21 124.846063K19 McMaster-Carr 8 8.02 64.161530-Lite Rankin Automation 97 7 79.54 556.78

33 335 240 240 245 255 225 1

2045 Rankin Automation 14 1.6 22.44481 Rankin Automation 32 7.3 233.63320 Rankin Automation 204 0.6 122.4

8982K83 McMaster-Carr 8' 2 18.69 37.388982K62 McMaster-Carr 1 40.33 40.33FAT 650 (ME 322-100-00)

http://www.andantex.com/brakes.html 2 1316 2632

96717A240 McMaster-Carr 1 12.76 12.7690273A583 McMaster-Carr 1 7.03 7.03Catalog #: 271-1716 Radio Shack 3 2.99 8.97 90126A030 McMaster-Carr 1 3.67 3.67

5-1367

http://www.surpluscenter.com/item.asp?UID=2007123020275974&item=5-1367&catname=electric 1 18.95 18.95

98790A030 McMaster-Carr 3 0.89 2.6794855A263 McMaster-Carr 1 6.72 6.7291113A030 McMaster-Carr 1 2.97 2.9788805K44 McMaster-Carr 1 13.19 13.199135K151 McMaster-Carr 1 13.8 13.889215K418 McMaster-Carr 1 14.69 14.69

3320 Rankin Automation 6 0.6 3.6

7587K83 McMaster-Carr 100. Ft 1 13.31 13.317587K391 McMaster-Carr 100. Ft 1 13.31 13.317587K603 McMaster-Carr 100. Ft 1 13.31 13.317587K599 McMaster-Carr 100. Ft 1 13.31 13.31

PSH-12180 FR www.batteryweb.com 2 57.95 115.9271-1716 Radio Shack 5 2.99 14.95276-270 Radio Shack 5 1.99 9.95276-271 Radio Shack 5 1.99 9.95276-272 Radio Shack 2 1.99 3.98275-625 Radio Shack 5 3.99 19.95PST-D24/12-300 Powerstream 1 106 106D-Link DWL-G820 Amazon 1 50.38 50.38330-070 Parts Express 5 2.64 13.2060-207 Parts Express 8 2.95 23.6NI 9476 National Instruments 1 299.99 299.99SSR25A Futurelec 2 14.9 29.8095-202 Parts Express 1 3.16 3.16095-212 Parts Express 1 3.75 3.75�ZX150856Y JC Whitney 1 19.99 19.99270-1809 Radio Shack 1 6.99 6.99350-056 Parts Express 3 4.9 14.7

1530-Lite Rankin Automation 145 7 118.9 832.31530-Lite Rankin Automation 97 6 79.54 477.24

105 2102 299 250 447 492 2

Rankin Automation 20 1.6 324481 Rankin Automation 24 7.3 175.24304 Rankin Automation 6 6.55 39.33320 Rankin Automation 168 0.6 100.8

1 2000 2000

http://www.hartsfabric.com/nylon.html 20 1 6.99 6.99King Upholstry 17Hrs 30/hr

4405 Rankin Automation 8 16.05 128.43320 Rankin Automation 32 0.6 19.2

FA-05-12-12

http://www.firgelliauto.com/product_info.php?cPath=76&products_id=51 4 119.99 479.96

4362 Rankin Automation 8 7.1 56.84481 Rankin Automation 16 7.3 116.83320 Rankin Automation 152 0.6 91.2

8968K611 McMaster-Carr 1 12.59 12.5991290A334 McMaster-Carr 1 9.87 9.87

90695A038 McMaster-Carr 1 3.65 3.65

88875K31 McMaster-Carr 2 10.89 21.78

5-1367

http://www.surpluscenter.com/item.asp?UID=2007123020275974&item=5-1367&catname=electric 1 18.95 18.95

9654K254 McMaster-Carr 1 13.99 13.993320 Rankin Automation 8 0.6 4.8

4 2 8Blanda Blank Ikea 8 8 64

3973A57 McMaster-Carr 2 26.23 52.461257A88 McMaster-Carr 2 11.52 23.047719T13 McMaster-Carr 1 4.36 4.363091A44 McMaster-Carr 1 28.98 28.983091A53 1 37.93 37.93

2513 https://www.blueskycycling.com 2 39.98 79.963013 https://www.blueskycycling.com 2 1.98 3.962197 https://www.blueskycycling.com 2 14.98 29.96

1610T41 McMaster-Carr 1 33.76 33.765-1367 http://www.surpluscenter.com/item.a 4 18.95 75.8SSR25A Futurelec 8 14.9 119.2275-625 Radio Shack 4 3.99 15.9657445K73 McMaster-Carr 4 5.4 21.6

Appendix C – Gantt Chart