Katlanabilir kanatlara sahip bir insansız hava aracının tasarımı, üretimi ve testleri
Design, manufacturing and testing on unmanned air vehicle with foldable wings
Yazar: İREM ÖZGÜR
Danışman: PROF. DR. GÖKHAN İNALHAN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Uçak ve Uzay Mühendisliği Ana Bilim Dalı / Uçak ve Uzay Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Uçak Mühendisliği = Aircraft Engineering
Dizin: Model uçaklar = Model aircraft

Özet:
İnsansız hava aracı sistemleri, son yıllarda kullanım alanlarının artması ile beraber sıklıkla tercih edilen sistemler haline gelmişlerdir.  Yer istasyonu ve haberleşme modülleri sayesinde görev gerçekleştirilen insansız sistemler, insanlar için tehlikeli ve zor durumlarda kullanılmak üzere tasarlanırlar.  Çoğunlukla askeri amaçlar doğrultusunda üretiliyor olsalar da sivil ve ticari alanlarda faaliyet göstermektedirler. Askeri görevlerde özellikle keşif, gözetleme ve istihbarat amacı ile operasyon gerçekleştiren insansız sistemler aynı zamanda doğal afet durumlarında arazi tarama, paket teslimatı, ya da tarımsal ihtiyaçlar doğrultusunda kullanılırlar.

İnsansız hava araçlarının kullanımında karşılaşılan problemlerden biri uçuşa başlamak için bir kalkış pisti ihtiyacıdır. Sabit kanatlı sistemler yüksek menzil kapasiteleri ve uzun uçuş süreleri için tercih ediliyor olsalar da engebeli arazilerde göreve başlayamamaktadırlar. Ayrıca bu tarz sabit kanatlı insansız hava araçları kanat boyutları nedeni ile hacimsel olarak depolama ve taşıma esnasında çok fazla yer kaplamaktadırlar. 

Bu tez çalışması belirtilen probleme çözüm sağlayabilecek katlanır kanatlara sahip ve tüp bir katapulttan fırlatılan bir İHA tasarımını, üretimini ve testlerini kapsamaktadır. KKİHA adı verilen sistem, tandem yani çift kanatlı taşıyıcı yüzeye sahip, arkadan itişli motor yönlendirme mekanizması ile tahrik edilen bir platformdur. Kuyruk konfigürasyonu olarak konvansiyonel tip kuyruk yapısı seçilen sistemin yatay kuyruğu kanat gibi taşıma üretmekte ve bu sayede kanadın boyutsal kısıtları nedeni ile tek başına yetersiz kaldığı kuvveti iki taşıyıcı kanat birlikte sağlamaktadır. Ayrıca motorunun bağlı olduğu yönlendirme mekanizması kontrol yüzeyleri ile çalışarak sistemin manevra kabiliyetini arttırmaktadır.

Genel konfigürasyonu belirlenen sistemin, bu çalışma kapsamında tasarımı yapılmış ve ağırlık tahminlerine göre aerodinamik analizleri ve uçuş karakteristiğini belirlemek adına performans hesapları gerçekleştirilmiştir. Belirlenen analiz sonuçlara göre piyasadan kolaylıkla ulaşılabilecek düşük maliyetli elektronik ekipman seçimleri yapılmış ve platforma entegre edilmek üzere temin edilmiştir. Bunların yanında platforma entegre edilmek üzere kanat katlama ve motor yönlendirme mekanizma tasarımları gerçekleştirilmiştir.

Tasarlanan sistemin, uçuş testlerinde kullanılmak üzere prototip üretimi yapılmıştır. Üretimde maliyeti düşük, yüksek mukavemete sahip bir kanat üretim metodolojisi geliştirilmiştir. Geliştirilen yöntemi ile üretilen prototipin boyutsal konfigürasyonu test etmek amacı ile uçuş testleri gerçekleştirilmiş. Test sırasında manuel olarak kullanılan sistemin testleri başarı ile sonuçlanmıştır.

Abstract:
Recent years, when the area of application increases, usage of unmanned aerial vehicle (UAV) is also increases. Unmanned aerial vehicles can be controlled with remote controller via radio signals or they can be operated autonomously. Generally, UAVs are used on military operations especially with the purpose of intelligence, surveillance and reconnaissance (ISR) missions during day time or night. Besides that, they can be used on civil or commercial applications; for example, searching terrain after natural disaster, object transportation, aerial photography or agricultural purposes. 

The main reason behind the development of unmanned vehicles are reduce risks on the pilot's life on the hazardous circumstances, therefore UAVs are developed for using on dangerous and critical missions. Thanks to operating air vehicles without human in them; weight of the system will be reduced. Thus, endurance of vehicles is increased; and also, its range capacity is enhanced.  According to usage purposes such as range constraints, there are variety of design configuration of UAV systems, but it can be possible to separate them in two groups: fixed wing and rotary wing system. 

Despite, these advantages of the UAV systems, there is a problem that necessity of take off field on fixed wing vehicles. When emergency situations occur, systems cannot be started mission on rugged terrains. Also because of the wing area, these vehicles need high volume for both transportation and storage. Therefore, it is necessary that the UAVs should be mobile and easy to deploy.

Scope of this thesis is offering a solution for this problem via the design of foldable wing uav which can fit into a tube launcher with the aspect of system engineering.  Due to foldable wings, platform needs smaller space, and this provides convenience while carrying. In addition to that, system uses launcher instead of taking off from ground, and that launcher can be operated from ground or any other aerial vehicle. Furthermore, low construction weights provide departed by hand. As a result of this, integrating landing gear is not necessity; body without landing gear reduces the drag force on the vehicle.

Due to these advantages of tube-launched system, design requirements were defined, and the first requirement of suggested system is launched from tube whose radius is 20 cm. Also, it should be carried by one person, so its maximum take-off weight is determined as 6 kg. Cruise speed of vehicle should be 24 m/s and minimum endurance is defined as 10 minute.  

According to these requirements, uav was designed. Design of uav is complex and needs knowledge about on many fields which are related with each other.  System design life cycle composed of mainly four phases which are conceptual design, preliminary design, detailed design, test and evaluation. Lifecyle iteration continues until final design of vehicle meets the requirements. This thesis work covers all these design phases, for suggested unmanned system.

In that manner, initial sizing was made. System should fit into tube catapult; so its chord should not be bigger than the width of the body. Moreover, because of length of the body, wing span is limited. Hence, one small wing cannot generate enough lift force and extra lifting surfaces becomes requisite. Therefore, wing configuration of the vehicle is chosen as a tandem configuration, and platform has also a single vertical tail.

There will be a camera with the purpose of surveillance applications in front of the body; therefore, pusher electrical propulsion is used, and electric motor is operated with a thrust vectoring control mechanism (TVC). TVC mechanism enables to enhance the maneuverability of the vehicle.  After defining the concept and fundamental dimensions of the platform; initial weight is estimated. During estimations,the production methodology of the prototype and market survey on avionics which is possible to use on vehicle were considered. 

According to weight data, wing and tail profiles are determined. For wing NACA 4412, for horizontal tail NACA 2411 is chosen among the different profiles, considering their 2D analysis and aerodynamic coefficients. Then, in the detailed design phase final weights and center of gravity is determined and results are used on aerodynamic analysis. 

XFLR5 software used for aerodynamic analysis and fundamental parameters are obtained like lifting, drag coefficient and trim angle and cruise velocity.  For the 5225 gr aerial vehicle whose detailed sizes determined, cruise velocity found 23.8 m/s which meets related requirement.

After finishing detailed design of the platform, subsystems are designed by taking consideration of estimated weight cost. Foldable mechanisms are designed separately for wing and tail. Wing folding mechanisms also has a closing one for using diving motion. While diving wing will close with the certain angle and motion will be regulated by TVC and tail.

Avionics which are used on aerial vehicle are chosen accordingly result of the marketing survey which covers the specifications like easily accessible, cost effective and lighter from equivalent ones. For the propulsion system motor there is limited product on market, therefore most suitable motor chosen from between limited options, which generates 7.3 kg thrust. In addition, it is decided that two lipo batteries which are connected in series, will be used on prototype, because single battery cover high volume. Instead of single large battery, two small batteries are more convenient to placed them in the body.

When vehicle weight calculations and design process completed, it necessary to calculate performance theoretically with using aerodynamic analysis results; in order to specify flight characteristics of vehicle. These calculations show that suggested design meets the requirements.

This study offers two different production methodology for wing manufacturing which is the most important component of vehicle. One of them is using 3D printers and produced wings from polylactic acid material. Second methodology is manufactured from sandwich composite. Fast prototyping, less time consuming and cost-efficient methodology is chosen for test prototype. Carbon-fiber sandwich composite production process only takes time on the molding phase; after molding completed, manufacturing time can be optimized. However, 3D printers lead to lots of problem such as time consuming or lower strength comparatively even if this is not foreseen.  

Because, there is not any chance of testing prototype on wind tunnel, especially testing performance of wing configuration and the manufacturing method of them, these features tested with real flight. As a result of that system manufacturing methodology and its geometrical configuration become successful.