Lockheed Martin Vertical Take-off and Landing Design Project and

Competition Final ReportTeam Members:

Thomas Sullivan, EE/COEJordan Billet, EE

Kai Sen Lathrop, MEKevin Osman, ME

Kirin Elahi, MEChristopher Rumasczak, ME

Sponsors:Lockheed Martin

Society of Hispanic Professional EngineersBinghamton University, State University of New York

August 25, 2014

Table of ContentsList of Figures: 3

Executive Summary 4

Introduction 5

Problem Statement 5

Pickup Mechanism 6

A. Initial Conceptual Pick-up Mechanism 6

B. Pick-up Mechanism Design 9

C. Testing 11

D. Final Design 13

Landing Gear Design 16

Flight Control Board 20

Motor, ESC, and Propeller Selection 21

Battery and Flight Time 24

Frame 25

Tuning and Flight Practice 26

Conclusion 28

Appendix 29

A. Budget 29

B. Schedule 31

i. Gantt Chart 31

ii. Timetable Strategy 34

C. Pickup Mechanism Assembly Schematics 35

List of Figures:Figure 1: Competition Arena........................................................................................................6Figure 2: Hopper Mechanism Concept........................................................................................7Figure 3: Mechanical Sweeper Concept......................................................................................8Figure 4: Mechanical Iris..............................................................................................................8Figure 5: Pickup Mechanism Pahl Beitz Chart..........................................................................9Figure 6: Pickup Mechanism Pahl Beitz Analysis......................................................................9Figure 7: Makerbot Replicator 2x..............................................................................................10Figure 8: Early Hopper Build.....................................................................................................10Figure 9: Revised Hopper Design...............................................................................................11Figure 10: Hopper with cable guides.........................................................................................12Figure 11: Amperage / Thrust Test Instrument.......................................................................13Figure 12: Final Build of the Pickup Mechanism.....................................................................14Figure 13: Final Pikckup Mechanism Assembly......................................................................15Figure 14: Mechanism Deploying 2-point Tennis Ball.............................................................16Figure 15: Initial Landing Gear Design.....................................................................................17Figure 16: Landing Gear Schematic..........................................................................................17Figure 17: Secondary Landing Gear Design.............................................................................18Figure 18: Tertiary Landing Gear Design.................................................................................18Figure 19: Final Landing Gear Concept...................................................................................19Figure 20: Fiber Glass Motor Mount.........................................................................................19Figure 21: Laser Cut Steel Motor Mount..................................................................................19Figure 22: Final Landing Gear Design......................................................................................20Figure 23: NAZE32 mounted on 3-D platform.........................................................................21Figure 24: Cobra CM-2217/20 Motor Propeller Data..............................................................23Figure 25: Cobra CM-2217/20 Motor Specifications...............................................................24Figure 26: Turnigy Plush 25 Amp ESC.....................................................................................24Figure 27: Flight time calculation..............................................................................................25Figure 28: Hobbyking X525 V3 600mm Quadcopter Frame..................................................26Figure 29: Fabricated Aluminum Frame..................................................................................26Figure 30: Final PID Settings.....................................................................................................28Figure 31: Initial Budget............................................................................................................30Figure 32: Final Budget...............................................................................................................31Figure 33: Gantt Chart...............................................................................................................33Figure 34: Gantt Chart...............................................................................................................34Figure 35: Timetable Strategy....................................................................................................35

Executive Summary

While vertical takeoff and landing poses additional difficulties as compared to conventional methods, there still lies a demand for such technology. When there is a need to take off without access to a runway, VTOL’s disadvantages can be overlooked. With the recent rapid increased use of unmanned aerial vehicles (UAVs), VTOL has been widely implemented into many UAVs due to the increased portability and flexibility that such a system offers the user. UAVs now also use VTOL’s ability to hover and land in conjunction with integrated systems and mechanisms as a means of surveillance and reconnaissance.

Though these features can prove to be valuable, VTOL is a very complex system. Because of this, designing a UAV capable of VTOL is a very difficult process. A popular variant is a multi-rotor aircraft which further increases the complexity of the system due to the need for complex controls and sensors in order to properly fly. In this competition, the challenge is to do just that, design a multi-rotor UAV with the added challenge of the ability to collect a payload.

Introduction

Under the sponsorship and consultation of Lockheed Martin and the Society of Professional Hispanic Engineers (SHPE), the Binghamton University team was able to compete in the Boeing Vertical Takeoff and Landing (VTOL) competition. The project of building a Quadcopter with a tennis ball pick-up mechanism from start to finish was volunteer to be completed by the team through the collaboration of each member of the multi-disciplinary engineering team. The main goal of the project was to design and build a Quadcopter through the utilization of knowledge and skills from Mechanical Engineering, Electrical Engineering and Computer Engineering. This project integrated the planning, brainstorming, designing, and fabrication of a functioning Quadcopter and a pick-up mechanism which was to be entered into the competition.

Problem Statement

The Boeing Vertical Takeoff and Landing competition asks student teams to create a Quadcopter that takes off from a designated platform and performs the task of lifting tennis balls of different weights and then dropping them in the designated drop zone. Each student team is given 15 minutes to pick up as many tennis balls as possible ranging in weight and drop them off in the drop zone. The tennis balls have different point values associated with their weight. The yellow balls (60g) are worth 3 points, the green balls (180g) 2 points and the red balls (300g) 1 point. The drop zone can have no larger than a 12’’ diameter. The pick-up zone and drop zone must be at least 50 feet away from each other and the take-off area is half between the two. The competition zone must at least be 15 feet away from an walls, as shown in figure 1.The Quadcopter is required to use at least one particular battery and part number (Turnigy nano-tech 4000mAh 3S 35-70C Lipo Pack), all other components of the Quadcopter were determined by the team through calculation and experimentation so that the most efficient Quadcopter can be built and designed.

Figure 1: Competition Arena

Pickup MechanismA. Initial Conceptual Pick-up Mechanism

Based on the competition requirements and scoring rules, the team brainstormed pick-up mechanism ideas. Three initial design concepts were chosen to be further explored based on the team’s judgment of their feasibility and efficiency at scoring potential points; a hopper mechanism, a mechanical sweeper, and a mechanical iris. One of the three conceptual designs was selected using a Pahl and Beitz evaluation to be revised and built.

The hopper mechanism concept (figure 1) was inspired by the function of tennis ball hoppers. Unlike a commercial tennis ball hopper, this mechanism requires a method to not only pick up tennis balls, but it must also drop them off. To achieve this, the cables on the bottom of the hopper change in tension with the assistance of a servo. When the cable is loose, the tennis balls are able to enter and fall out of the hopper, and when the cable is taunt, the tennis balls are held within the hopper.

Figure 2: Hopper Mechanism Concept

The mechanical sweeper concept (figure 2) relies on a scoop that moves linearly to capture tennis balls within the mechanism. The motor used to close this mechanism would rely on a rack and pinion gear system and guiding rods to close and open the sweeper.

Figure 3: Mechanical Sweeper Concept

The mechanical iris concept originates (figure 3) from the closing shutter in a camera lens. The center is covered by five blades that open and close through rotation of the outer ring. Many of the mechanism components would have to be printed individually in order to construct an iris large enough to fit tennis balls.

Figure 4: Mechanical Iris

The Pahl and Beitz analysis (figure 4) emphasized five different categories with individual weighting factors based on significance. The first category, efficiency, considered each mechanism’s operational time to successfully pick up and drop off the tennis balls. The second category, easy to build, considered the feasibility of building a functional final prototype before

the competition date. The third category, ease of use, considered how easily the pilot could operate the mechanism. The fourth category, reliability, considered the potential repeatability of the mechanism’s operation before failure. The last category, ease of fixing, considered how easy fixing the system would be in the case of part failure. After the team voted and averaged the scores for each conceptual design under each category, the hopper mechanism was chosen to be implemented in the final solution.

Figure 5: Pickup Mechanism Pahl Beitz Chart

Additionally the concept of designing a secondary system to lower the pick-up mechanism was explored. The reason behind theoretically lowering the pickup mechanism from the body of the quadcopter was to reduce the force applied to the unweighted tennis balls with high point value due to the thrust of the propellers. This concept was considered as a team using a Pahl and Beitz chart (figure 5), and it was decided that the theoretical benefits were outweighed by the complexity and extra weight a lowering system would impose. A final test of this concept was further explored in order to make a final decision.

Figure 6: Pickup Mechanism Pahl Beitz Analysis

B. Pick-up Mechanism Design

The mechanical hopper was largely designed through iterative functional prototyping through the use of Makerbot Replicator 2x (figure 6). This tool allowed the team to 3D-Print in ABS plastic multiple iterations of most of the components that made up the mechanical hopper and efficiently test revisions to the design.

Figure 7: Makerbot Replicator 2x

The bottom half of the pick-up mechanism was printed and assembled to test the operation by hand (shown in figure 7). From this iteration of the design, a friction was observed in the bend which caused an uneven taunt to the cable that could potentially cause the tennis ball to be stuck. To resolve this, two design changes were made; a thinner nylon cable was used, and instead of a single strand of cable, the cable was split into two strands entering the bottom of the hopper (shown in figure 8).

Figure 8: Early Hopper Build

During the concept phase of this design, it was believed that a ratcheting system would be required to hold the necessary amount of tension within the system. This belief was debunked through attaching a high torque servo to the cable using a 3D-Printed spool and observing that the servo motor could hold the cable in a state of tension with the maximum anticipated payload. By removing the need for a ratcheting system, the design was greatly simplified (figure 8) and reduced in overall weight.

Figure 9: Revised Hopper Design

Final revisions were made to implement upper and lower cable guides (shown in figure 9) to direct the motion of the cable and guarantee that the slack would travel equally into the bottom two cables. The cable guides also double as the mounting points for a flexible metal bicycle cable housing that could be lubricated to reduce friction.

Figure 10: Hopper with cable guides

The rods and mounting bars were cut out of standard sized aluminum in order to improve the structural rigidity of the hopper in the case of impacts during flight. The aluminum was also light enough to allow for the overall vehicle design to be less than twice the available thrust, which provided for optimum pilot control.

C. Testing

The strategy for approaching the pickup zone was determined through a measured thrust test. In order to determine if a lowering pickup mechanism would be beneficial, the minimum height the active propellers could be from the ground before the 3 point unweighted tennis balls would be pushed out of the pickup zone was found. In order to measure an approximate thrust, a testing instrument was built with a multimeter, single brushless motor and propeller. The multimeter read the supplied amperage (shown in figure 10), which was used to replicate the same amount of thrust on a scale to measure the resultant thrust.

Figure 11: Amperage / Thrust Test Instrument

The supplied power was increased until the unweighted tennis balls rolled away at two set heights, 3ft and 6ft. The resultant thrust that caused the displacement of the tennis balls is shown in table 1. The maximum allowable thrust for a single motor and propeller combination was in the range of 127-166g. All four motors and propellers creating this thrust individually would not feasibly lift any vehicle off the ground with or without the 80g load of the tennis ball.

Test Height Amps * 10-2 Resulting Thrust (g)

3 ft 1.37 166

6 ft 0.94 127

The results of the test proved that a statically mounted pickup mechanism would be the best approach for maximizing the potential points during competition. Additionally a static system is simple and relatively lighter in weight to a retracting mounting, which also improves the handling of the vehicle.

D. Final Design

Table 01: Amperage/thrust test data

The final design preformed repeatedly with all weighted tennis ball types. After extensive practice of piloting the quadcopter and operating the pickup mechanism, the nylon cables stretched. The tension levels of the system were adjustable through a metal pinch that bound the two lower cables to the spooling cable, allowing the mechanism to preform consistently.

Figure 12: Final Build of the Pickup Mechanism

The final design includes seven 3D-Printed components, eight standard screw and nut fastener combinations, and eight aluminum simple aluminum components. The servo used in the mechanism is a Towardpro MG996R high torque servo motor. The components were press fit in place, then cotter pins were later installed to allow for components to be exchanged in the case that they break. The mechanism was rigidly connected to the quadcopter with four long M4 bolts through the aluminum connecting bars.

Figure 13: Final Pikckup Mechanism Assembly

Competition Performance

The hopper pick-up mechanism performed consistently and well during the 15 minute competition. Despite worries over the high torque servo motor overheating after extended use, the servo did not fail during competition and the spare servo motor did not have to be installed. The pick-up mechanism carried 17 points worth of tennis balls out of the pick-up zone and brought them to the drop-off zone. The pickup mechanism deployed all of the tennis balls towards the collection bucket, but only 5 points worth of tennis balls actually made it into the scoring container. A possible improvement for the pickup mechanism would be to add aiming guides for more accurately deploying the payload.

Figure 14: Mechanism Deploying 2-point Tennis Ball

Figure 15: Initial Landing Gear Design

Figure 16: Landing Gear Schematic

Landing Gear Design

The landing gear design was amongst one of the most important aspects of the project because it was what protected the sensitive and vital parts of our quadcopter including the pickup mechanisms, propellers, servo motor, etc. The landing gear needed to be able to withstand an extensive amount of impact and distribute the resulting loads evenly throughout each of the four landing gears in order to function appropriately.

After several test runs, it became clear that this particular task of the project had proven to be one of the most trouble-some of tasks. Many parts had been damaged during these test runs. Some parts were easily replaced such as the propellers while other parts such as the pickup mechanism had to undergo complete reconstruction due to excessive damage. After proposing various ideas, the fifth design had proven to be the most reliable and safe.

The first design that was implemented utilized the landing supports provided by the Hobbyking X525 V3 Quadcopter Frame. The landing legs were made of black glass fiber. After the pickup mechanism was made however, 3D printed extensions were bolted onto the landing legs in order to protect the mechanism and absorb the shock/impact of landing (labeled as “Landing Feet” in the detailed drawing depicted below). After one or two test runs, the 3D printed landing feet snapped as well

Figure 17: Secondary Landing Gear Design

Figure 18: Tertiary Landing Gear Design

as one of the fiber glass legs. This design led to the realization that the sharp corners on the extended legs propagated cracks and a totally different design for leg extenders should be addressed.

In order to evenly distribute stress across the landing gears, the next design offered rounded edges. The figure below is a CAD of our landing gear that was tested as well. The fiberglass legs were used again. This time, the 3D-printed extensions were rounded and bolted onto the legs. After a few attempts however, the 3D-printed extenders snapped and it was noted realized that 3D-printed material was not a good shock absorber for this amount of impact.

The third design had suggested steering away from the fiberglass legs and replacing them with aluminum rods to support each of the four legs during impact. The aluminum rods would be connected to the quadcopter via the 3D-printed rod adapters shown in the figure below. Lastly, pipe insulation would be zip-tied to the bottom of the rods in order to absorb the impact and distribute the stress evenly. This design was not utilized since it the rod adapters connecting the rods to the frame were made of ABS (3D-printing material). This design led to the conclusion that no parts of the landing gear should be made of ABS and a new perspective should be considered when brainstorming ideas for this prolonging dilemma.

The landing gear shown below differentiated from the previous designs and led to a major breakthrough in the landing gear dilemma. Each of the four legs had two parallel sheets bolted together in an “L” shape in order to support the major impact of each landing. During the test runs it was noted that the weight of the aluminum rods were an issue and consumed a lot of battery power. And with no rubber-like material to serve as an initial dampener, there was a lot of stressed imposed on the quadcopter. As a result, the pickup mechanism had cracked and one of the motor mounts had snapped, and new laser cut, 1/8 inch hot rolled steel motor mounts replaced the original fiber glass motor mounts for durability. Images of the above described landing gear design and motor mount comparison are shown below.

Figure 19: Final Landing Gear Concept

Figure 20: Fiber Glass Motor Mount

Figure 21: Laser Cut Steel Motor Mount

Shown below is the final landing gear design. It is almost identical to the previously portrayed design, however a few inches of the aluminum extenders were shaven down. To make up for the lost length, cut-outs of tennis balls were used to make up for the lost length. This allowed the Quadcopter to be light enough to take off vertically, durable enough to embrace hard impact, and allowed the tennis ball material to cushion most of the stress from landing. As shown below the length of the landing gear allowed the material to dampen the impact absorb the initial shock of each land, yet allowed the pickup mechanism close enough to the ground to pick up tennis balls. This design had proven its usefulness during the competition when it prevented the quadcopter from

getting damaged as it hit the

gymnasium wooden floors at a rather rapid rate.Figure 22: Final Landing Gear Design

Flight Control BoardInitially we thought the flight board should be where we allocate a good portion of our

budget to. This turned out not to be the case, and going with a “keep the design simple approach” would have been a better strategy and is what we ended up doing in the end.

After doing much research we found that the APM 2.6 had very great reviews and we thought that it would be a great choice. This controller offered G.P.S. capabilities that were advertised to make the flight more stable and be more intuitive for the operator. Once we received the board we ran into a number of issues implementing it. Most of them coming from the complex firm where and tuning of the PID settings. After working with this controller for a couple weeks the team got in contact with another student that has work with quad copters for a number of years as a hobby. His recommendation was to go with an open sourced flight controller the NAZE 32. We gave it a shot because this controller was only about $25 when the higher end one we had and could not get to work was $250. After receiving this flight control board we had our copter airborne within hours and fine-tuned within the next couple days. Two big lessons learned here are.

1. Keeping a design simple is a great approach to many challenges with a tight time schedule because the implementation of a complex idea is very hard with limited time and resources.

2. The best information will normally come from someone with experience rather than other sources that may be bias or not applicable to a certain application.

Figure 23: NAZE32 mounted on 3-D platform

Motor, ESC, and Propeller Selection

In choosing the proper motors for the Quadcopter, the desired flight performance of the Quadcopter along with the current providing capabilities of the battery were considered. A set of low KV rating motors with large propellers was the best motor-propeller combination for a Quadcopter that required a lot of thrust and did not need to be agile, whereas a set of high KV rating motors with small propellers was the best motor-propeller combination for a Quadcopter that required a high level of agility, but a low amount of thrust. Agility was not required from our Quadcopter so a motor with a low KV rating with a large propeller seemed to be the best choice, however too much thrust and the tennis balls would scatter before the Quadcopter would be able to successfully capture them. It was required to generate an amount of thrust suitable to not only hover effectively, but also to lift one or more tennis balls while still maintaining stable flight.

The amount of thrust required was decided upon so that the Thrust to Weight ratio was greater than one. The total weight of the Quadcopter was 994 grams, and it was designed to be able to pick up two of the 300 gram tennis balls without losing any capability of flight, so it was determined that the total amount of thrust required to be generated by the motor-propeller combination must exceed 1594 grams.

To generate the amount of thrust required to allow the Quadcopter to hover demanded the motors to draw a certain amount of current from the battery. The battery used was the Turnigy nano-tech 4.0 4000mAh 35-70C High Discharge Li-Po battery. The maximum continuous supplied current rating of the battery was determined by multiplying 4000 mAh by 35, the C-rating, which gave 140 Amps of continuous current. This meant that all of the electrical components present on the Quadcopter could draw no more than 140 Amps continuously in order to ensure safe operation.

With the aforementioned criteria taken into consideration, the Cobra CM 2217/20 motors were chosen along with 11 inch propellers with 4.5 inch pitch. This motor-propeller combination was advertised to yield 1012 grams of thrust per motor- propeller combination as shown below.

Figure 24: Cobra CM-2217/20 Motor Propeller DataMultiplying by four for each motor-propeller combinations gave a total advertised thrust

of 4048 grams which would provide the Quadcopter with a more than suitable amount of thrust. The maximum continuous current listed for the motors was listed as 20 Amps as listed below. Multiplying by four gave the total maximum continuous current that would be drawn from the four motors. With an 80 Amp maximum current draw from the motors, and a combined current draw of around 5 Amps by the flight controller and servo motor, the total maximum amount of current that could potentially be drawn from the battery was well within the 140 Amp maximum continuous current rating of the battery.

Figure 25: Cobra CM-2217/20 Motor Specifications

The Cobra CM 2217/20 motors were therefore a suitable motor choice for the Quadcopter, and needed ESCs to transform the DC supplied by the battery to three phase AC, which was required by the three phase brushless motors. The ESCs needed to be able to handle the distribution of at least 20 Amps of current to each of the motors continuously, therefore the Turnigy Plush 25 Amp Electronic Speed Controllers were chosen in order to safely and reliably route power to the motors, and to the servo motor, used to control the pickup mechanism, using the built in BECs (battery eliminator circuits) of the ESCs. An image of the ESC with BEC connector is shown below.

Figure 26: Turnigy Plush 25 Amp ESC

Battery and Flight Time

The only restriction of the parts to be chosen for the Quadcopter was the battery, which was the Turnigy nano-tech 4.0 4000mAh 35-70C High Discharge Li-Po battery. The main objective was to maximize the total time that the Quadcopter could fly on a single battery in order to minimize the number of battery changes. The estimated value for the total flight time was calculated by approximating the total current draw from each of the four motor-propeller combinations to be 40 Amps, half that of the maximum continuous current the motors drew from the battery, multiplying the 40 Amps by 11.1 Volts, the voltage supplied by the battery, to get the total power drawn from the battery. Then, the total energy of the battery was calculated by multiplying 4000 mAh by the total voltage across the battery. Finally, the calculated total energy of the battery was divided by the total power to give the total approximated flight time. The calculated values are shown below.

Figure 27: Flight time calculation

During the 15 minute long competition, only two battery changes were necessary, which showed that the approximated flight time was accurate for the duration of the competition.

Frame

The preliminary frame choice was the Hobbyking X525 V3 600mm quadcopter frame (Figure 1). This frame seemed to be a wise choice for several reasons. The arms are made of lightweight aluminum while the other components are fiber glass, resulting in a low total weight which would require less thrust, thus lowering the chance of blowing away the low weight, high point payloads. The modular design of was an added benefit which gave us the ability to change out broken parts in case any damage occurred due to test flights and tuning. Another key feature of the fame was the included shock absorbing landing gear. The spring-loaded mounts gave us the availability to either design our pickup mechanism around them or modify them in order to reduce impact stressed on the mechanism. Last but certainly not least was the cost factor. With a relatively low budget for multiple big tag items, choosing an inexpensive frame gave the budget more wiggle room to use higher quality choices for some of the more crucial components.

Figure 28: Hobbyking X525 V3 600mm Quadcopter FrameA mere five days before the competition date, catastrophe struck. While practicing and

tuning, the quadcopter crashed, bending an arm, and breaking multiple frame components. With no time to order a new frame online and wait for it to ship, and very little money left in the budget, we decided that the only option was to build a new frame from raw materials. Using aluminum square tubing and sheet aluminum, we built a rugged, simplified, heavier version of the Hobbyking frame. While although the new frame’s weight proved more difficult to approach lighter weight balls, the controllability was improved dues to the increased moment of inertia.

Figure 29: Fabricated Aluminum Frame

Tuning and Flight Practice

Once the quadcopter was fully assembled, the Acro NAZE32 flight control board along with the Turnigy Plush 25 Amp Electronic Speed Controllers had to be tuned and calibrated for flight. The NAZE32 used the Crossplatform configuration tool, Cleanflight, a Google Chrome Add-On, for tuning and calibration. Before the flight controller was tuned and the ESC’s were calibrated, the propellers were removed from the Quadcopter. This was a necessary step which was carefully taken prior to every tuning/calibration in order to avoid damaging/destroying the Quadcopter, and to avoid the possibility of injury.

The initial phase of tuning/calibration included customizing the NAZE32 to control our particular Quadcopter rotor arrangement. Within Cleanflight, there were offered multiple different flying modes depending on the type of aircraft that was to be controlled. Since our particular machine was a Quadcopter arranged in the X-configuration, that choice was selected. Cleanflight offered the user the ability to calibrate the accelerometer and gyroscope present in the NAZE32 by prompting the user to move and rotate the Quadcopter about its various axes. Next came perhaps the most critical phase of tuning/calibration, which was ensuring that the NAZE32 was successfully receiving the commands sent by the Turnigy 9x 9 channel transmitter, and that upon reception, the flight controller was interpreting those commands properly. This was done by means of a feature offered in the Cleanflight software which allowed the user to increase throttle, pitch, yaw, and roll via the input joysticks on the transmitter. It was at this stage in the tuning where it was most important for the propellers to be removed from the motor armatures because during this part of tuning the user is prompted to move the joysticks to their maximum positions so the flight controller can properly calibrate the ESC’s to send the correct amount of current to the correct motor. Both the direction as well as the speed of the rotation of the motors was monitored for the duration of this stage of tuning to ensure their proper performance. Another feature offered by Cleanflight was the customization of different flight modes that the operator could switch between during operation of the Quadcopter. The user could choose which frequency band to allocate to the different modes of flight on a designated channel of transmission. Different flight modes were experimented with over the course of tuning, however the particular flight mode which was found to be most reliable was Angle mode, which used the flight controller’s accelerometer and gyroscope to keep the Quadcopter level when the user is not providing any inputs to the system.

This mode of flight required calibration, however, and proved to be one of the more challenging aspects of the project. In this stage of tuning, the flight controller’s PID (Proportional-Integral-Derivative) settings had to be customized to the specific design of our Quadcopter.

Each of the three settings were modifiable coefficients responsible for the control of the Quadcopter, and each of the coefficients served a unique purpose in error mitigation. The P part of the PID controller produces an output value that is proportional to the current error value, and this control coefficient is the most responsible for the stability of the system. A P value that is

too high will result in an over-sensitive system. Too low a P value and the system will seem sluggish and unresponsive to any user inputs. The I part of the PID controller produces an output based on the sum of the instantaneous error over a period of time, and this control coefficient allows settling time to be reached more rapidly than in a strictly proportional control system. In other words, the I value effects how quickly the system corrects error. The D part of the PID controller produces an output based on the slope of the error over a given amount of time, and primarily serves to amplify user input.

In order to effectively tune the Quadcopter, each of the PID coefficients were adjusted starting with the P setting. Once the P setting was set to an optimal value, and the Quadcopter could hover stably, the I and D parameters were modified until the Quadcopter was fully controllable. The final settings for the PID coefficients were set in Cleanflight, and a picture of those settings are shown below.

Figure 30: Final PID SettingsUpon completion of successfully tuning the Quadcopter, the final and perhaps most

challenging phase of the project began; practicing piloting the Quadcopter. Although the Quadcopter was fully controllable, and operational, piloting the Quadcopter effectively proved to be very challenging and demanded a lot of time to be devoted to practicing. Pilot practice involved setting down a group of tennis balls in a dedicated circular area, and hovering over the balls until it was suitable for the pilot to descend on top of a ball, lock it into the pickup mechanism by flipping a switch on the transmitter, take off with the ball, hover over a five gallon bucket, and then release the captured ball into the bucket. The piloting practice attempted to model the environment of the competition as closely as possible, while making it more difficult for the pilot during testing than it would be during competition.

Conclusion

Despite all of the time spent on practicing piloting, in order to have performed better during the competition more piloting practice was necessary. During competition, 5 balls were successfully dropped in the drop zone, and another 6 were dropped close to, but did not land in the drop zone. Out of all of the teams to have competed, the Binghamton University team placed second, which a great achievement was considering all of the other teams consisted of senior engineering students competing for a grade, while the Binghamton University team was comprised of juniors all of which were not competing for a grade. Also, the Binghamton University team was the only other team to have successfully engineered a fully functional Quadcopter which accomplished all required tasks and met all project requirements. An even greater achievement though, was the technical and professional skills that were developed by all members as a result of being involved with this project. The collaboration of engineering students from different backgrounds allowed for each member to understand the unique importance of their teammate’s respective engineering fields of study, and to reinforce the effectiveness of teamwork. This project also allowed each member to experience the progression of a technical project from start to finish, to witness and cope with unforeseen issues, and to complete the project while remaining within the constraints of a fixed budget and deadline.

The Binghamton University team would like to thank all of the Lockheed Martin staff members for their consultation, time, and for providing us with all of the opportunities and learning experiences this project has offered us.

AppendixA. Budget

The initial and final budget is shown in figures 2 and 3 below. Figure 2 documents the initial budget that was made at the start of the project and does not include tax estimates or shipping costs. The final budget is shown in figure 3 and totals $855. 89. From the initial budget to the final budget there was an increase of roughly $200, this increase was due to unforeseen malfunctions with parts that could not be assumed at the start of the project, it also accounts for the design changes that the pick-up mechanism underwent in order to make the Quadcopter as efficient as possible. A requirement of the project was to adhere to the $1000 budget set down, which the Quadcopter successful did.

Figure 31: Initial Budget

Component QuantityCost (Each)

Total Cost: Tax Shipping

Grand Total Hardware: Tax:

controller (2.6+ apm) 1 $159.99 $159.99 $0.00 $0.00 $159.99 $4.98 $0.00

GPS Unit 1 $79.99 $79.99 $0.00 $14.19 $94.18 $3.78 $0.30

Motors 6 $30.99 $185.94 $0.00 $17.25 $203.19 $5.98 $0.48

ESCs 6 $13.60 $81.60 $6.53 $5.00 $93.13

Frame 1 $17.30 $1.38 $2.25 $20.93

Propellers 8 $3.16 $25.28 $0.00 $13.30 $38.58 $5.99 $0.48

Transmitter/Receiver 1 $79.35 $79.35 $0.00 $12.75 $92.10 $4.49 $0.36

Hardware/Misc. 1 $41.81 $41.81 $2.95 $0.00 $44.76 $6.63 $0.53

Battery 2 33.7 67.4 0 11.63 79.03 $9.96 $0.80

Naze 32 Flight Control Board 1 30 $41.81 $2.95

Total $671.26 $10.86 $64.74 $855.89

Figure 32: Final Budget

B. Schedulei. Gantt chart

On the following pages is the Gantt chart used by the team for the duration of the project. Most of the tasks had been completed either one day before or the day that it had been due. The milestones of the Gantt chart had been finished on time (some of which include the Preliminary Design Report, the Critical Design Report and the Final Design Report). However some tasks had taken longer than expected. Two tasks that were noted to take the longest had been the final design of the pickup mechanism and the landing gear design. The landing gears had been one of the most serious issues of the project and had resulted in constant damaging of the pick-up mechanism. Because of this, the landing gear and the pickup mechanism simultaneously were under constant revision and replacement.

Figure 33: Gantt chart

Figure 34: Gantt Chart

ii. Timetable StrategyDepicted below is the planned strategy undergone during the competition. Each run

assumed in this table that the pickup mechanism would only pick up one ball at a time. Only one of the runs was an exception and was projected to earn a score of four points (two red tennis balls). The reason for this exception was that by chance two red tennis balls were going to be right next to each other during at least one instance of this competition). This timetable assumed that the pickup mechanism had been successful in picking up both balls. Seventeen points were not earned during this competition however. Although the quadcopter had picked up and dropped each ball at the approximate times during the competition, the task of dropping the balls at the appropriate drop-off zone had proven to be harder than expected.

Figure 35: Timetable Strategy

C. Pickup Mechanism Assembly Schematics