Asian Workshop on Aircraft Design Education

AWADE 2016 Nanjing University of Aeronautics and Astronautics (NUAA), 08-11 October 2016

http://aircraftdesign.nuaa.edu.cn/AWADE2016

THE ELECTRIC POWERED UAV DESIGN/BUILD/FLY PROJECT FOR UNDERGRADUATES AT NUAA

Xiongqing Yu Nanjing University of Aeronautics &Astronautics

College of Aerospace Engineering Yudao St, 29.

210016, Nanjing, China, e-mail: yxq@nuaa.edu.cn

Key words: Unmanned Air Vehicle, Design project, Design education, Teamwork.

Abstract: This paper presents aircraft design education practice through a design/build/fly project of remote-controlled, electric powered unmanned air vehicles. The primary goal of the project is to have students gain insight into the processes of aircraft design and developments. The project covers conceptual design, preliminary design, detail design, fabrication, and flight tests of the electric powered unmanned air vehicle. The organization of student teams, instructors, and process-monitoring is critical for success of the project. Several examples of the project are illustrated. The observations to the project are concluded.

1 INTRODUCTION Since 2004, a design/build/fly project for remote-controlled, Electric-Powered, Unmanned

Air Vehicles (EPUAVs) has been conducted at Nanjing University of Aeronautics and Astronautics (NUAA). The objectives of this project are to have the students gain insight into the processes of aircraft design and developments; to motivate the students to gain knowledge in areas including aerodynamics, structures, propulsion, flight dynamics, control and manufacture; to develop skills to solve engineering problems; and to cultivate engineering teamwork.

The project is oriented to seniors (forth year students) majoring in aircraft design and engineering, and is financially supported by the Teaching Affairs Office at NAUU[1]. Up to this point, more than 70 teams have participated in and completed the project. In this paper, the processes and organization of the project will be presented, several examples of the project will be illustrated, and, in conclusion, observations to the project will be offered.

2 PROJECT REQUIREMENTS AND PROCESS

The tasks of the project are: 1) the student team must develop a design for a remote-controlled, Electric-Powered Unmanned Air Vehicle (EPUAV); 2) the student team must finish the fabrication of the EPUAV; 3) a flight test must be demonstrated.

The basic requirements for the EPUAV are: 1) the maximum size of the EPUAV is no

24

Xiongqing Yu

25

larger than 2.5m due to transportation limitations; 2) the cost of the EPUAV fabrication is less than ￥4000 due to the limited budget; 3) the team should determine the design concept of the EPUAV and its design requirements; 4) the EPUAV project should be finished within 18 weeks.

The project is divided into six phases: 1) conceptual design, 2) preliminary design, 3）detail design, 4）fabrication, 5）flight tests, and 6) documentation and presentation.

1) Conceptual DesignIn the conceptual design phase, the major works are: (1) determining the EPUAV overall

configuration; (2) designing the fuselage configuration, wing configuration, empennage configuration, control surface configuration and landing gear layout; (3) selecting a propulsion system; (4) evaluating the design concept through the aerodynamics, propulsion, weights, performance, and stability analysis using rapid engineering methods.

Students should complete the conceptual design by the use of software and tools. For example: the CAD software CATIA is used to generate the aircraft configuration, and the program AVL[2] (a code based on vortex lattice method) and Friction[3] (a code predicting zero-lift drag) are used to evaluate the aerodynamic performance.

Usually, the conceptual design phase needs 3 weeks. The primary outputs of conceptual design phase are a 3D model of the aircraft configuration, and a document on feasibility of meeting the requirements with evaluation results for the design concept. A typical 3D model of the aircraft configuration from the project in 2016 is shown as in Fig.1.

Figure 1: 3D model of aircraft configuration in conceptual design phase

2) Preliminary DesignIn the preliminary design phase, the aircraft configuration from conceptual design phase is

evaluated by a more detailed method. The aerodynamic performance is evaluated by the panel method or other CFD software. Figure 2 is an example of aerodynamic modeling by the panel method[4]. Based on the more detailed evaluation results, the configuration is refined to improve the aerodynamic performance.

The internal and structural layout of aircraft is developed by use of CATIA during the preliminary design phase. The structural materials are selected and the structural components

Xiongqing Yu

26

are sized, based on past experience. The structural weight prediction of aircraft is refined using CATIA. The more detailed

flight performance and stability characteristics are evaluated using the refined aerodynamic and weight data.

The preliminary design phase usually needs 4 weeks. The primary outputs of preliminary design phase are 3D models of the refined aircraft configuration, and internal and structural layout, plus a document that guarantees the design requirements are met. A typical geometric model of the internal and structural layout is shown in figure 3.

Figure 2: Aerodynamic modeling by panel method in preliminary design phase

Figure 3: Geometric model of internal and structural layout

3）Detail Design In the detail design phase, all parts of the structure are designed based on the structural

layout from the preliminary design phase. The primary loads are determined and the stress

Xiongqing Yu

27

and deformation of the overall structure are predicated using MSC.Patran software. The designs for the major connecting parts of the structure are refined to make sure that the parts have enough stress. The control systems that control the motor, rudder, elevator, ailerons and landing gear are designed.

Usually, the detail design phase needs 5 weeks. The outputs of the detail design phase are the drawings of all parts and the control system. Figure 4 is an example of parts design and stress analysis.

Figure 4: Wing rib design and stress analysis.

4）Fabrication All parts are fabricated and assembled into the components in the NUAA fabrication lab

or in the cooperative factory by the team. The facility, such as laser cutting machine, drill and others are provided in the fabrication lab. Figure 5 shows students fabricating a mould for the fuselage skin, and assembling the wing and fuselage in the fabrication lab. The fabrication of the EPUAV usually takes four weeks.

Figure 5: Students fabricating the EPUAV in the lab

5）Flight tests After finishing the fabrication of the EPUAV, students can begin to test their vehicle. The

tests include: 1) propulsion system test, 2) control system test, 3) ground taxi test; 4) flight test.

Figure 6 shows students conducting the ground test of the EPUAV. Figure 7 shows the flight test of the EPUAV. The tests of the EPUAV usually take two weeks. 6）Documentation and Presentation After finishing the flight tests, students must write a report on the processes and their

achievements of the project. Also, a final presentation of the project must be delivered by each team to the instructors and the other students. The grade for each student is determined

Xiongqing Yu

28

by the team achievement, individual contribution and attendance.

Figure 6: Taxi test of the EPUAV on the lake at NUAA campus

Figure 7: Flight test of the EPUAV

3 ORGANIZATION OF THE PROJECT The EPUAV project is challenging for students, and a large amount of work must be

completed in 18 weeks. Therefore, organization is critical for success of the project. 1) TeamsEach year around five teams participate in and complete the project. Each team usually

consists of five or six students. A team leader is responsible for organizing the weekly team meeting, and coordinating the teamwork. Each student is responsible for a specific discipline, such as aerodynamics, structures, propulsion, stability and control. Each team should have weekly meetings to discuss current accomplishments, to make decisions about specific problems, and plan the next steps. All members should participate in the discussions at each team meeting. Every member is equally responsible for the team’s progress and success.

2) InstructorsThe EPUAV project is directed by a group of instructors, who are specialized in different

disciplines, such as aerodynamics, structures, propulsion, stability and control. During the project, the instructors give a series of lectures on each phase of the project; for example: an

Xiongqing Yu

29

overall project plan, conceptual design method, aerodynamic analysis method, and application of structural analysis software.

A group of teaching assistants (graduate students) also play an important role in assisting in use of the software and fabrication of the EPUAV.

3) Project monitoringIn order to complete the EPUAV project within the limited time, project monitoring is

necessary. Each team must submit a report detailing their weekly progress after which the instructors can discuss the designs with the teams, and give them advice and guidance.

The results of the conceptual design, preliminary design and detail design must be presented in a critical design review meeting to the instructors and all teams.

4 EXAMPLES OF THE PROJECTS

More than 70 teams have participated and completed the EPUAV project since 2004. Various EPUAV concepts are designed, fabricated and tested. The following are a few examples of previous EPUAV projects.

1) Flying carIn 2007, a team proposed a flying car design concept as shown in figure 8. This project

was quite challenging, especially for the design of the propulsion system which needed to drive the wheels when in car mode and the propeller when in aircraft mode. The team successfully completed the design, fabrication and tests of the flying car model. The tests showed that the flying car model could run on road like a car, and could fly like an aircraft.

(a) Configuration of the flying car

(b) Structual layout of the flying car (c) Team members and their flying car model

Xiongqing Yu

30

Figure 8: Flying car project

2) Modular aircraft conceptIn 2007, a team proposed a modular aircraft concept. The fundamental theory is that two

basic aircraft can be connected to produce a new large aircraft (derivative aircraft). In this way, a family of aircraft for different missions can be produced with low cost. The configuration of the basic aircraft is a canard configuration aircraft as shown in 9(a). The team built two of the basic aircraft, and then connected the two together to obtain a derivative aircraft which has a canard, double fuselage configuration as shown in 9(b). This derivative aircraft has new performance with longer endurance and larger payload. The flight tests showed that both the basic aircraft and the derivative aircraft had good stability and control characteristics.

(a) basic aircraft (b) derivative aircraft Figure 9: The modular concept EPUAV

3) BWB aircraft projectAircraft designers are becoming increasingly interested in the Blended Wing Body (BWB)

configuration due to its higher aerodynamic efficiency. But the stability and control characteristics of BWB configuration had not been fully explored. In 2011, a team tried to study the stability and control characteristics of the BWB concept by constructing a BWB model aircraft. They built the BWB model aircraft as shown in figure 10, and finished several flight tests. From this project, the students realized that the prediction accuracy of the center of gravity (C.G.) and aerodynamic center (A.C.) during the preliminary design of the BWB model aircraft are crucial for its stability and control. Also, special attention should be paid to the the control surface layout design od this type of aircraft. The flight tests showed that the BWB model aircraft could attain good stability and control characteristics after the team adjusted the center of gravity and modified the control surface layout.

Xiongqing Yu

31

Figure 9: EPUAV with BWB configuration

4) Joined-wing aircraft projectThe joined-wing configuration is another interesting unconventional concept that has

advantages in terms of wing structural stiffness. In 2015, a team proposed a joined-wing configuration aircraft concept for future civil transport, and built a scaled model aircraft. They used aerodynamic analysis software to investigate the aerodynamic interference between the front-wing and aft-wing, and stability and control characteristics of the joined-wing configuration. During flight test, the pilot said that it was very easy to fly the joined-wing model, and it was much like flying a model aircraft with a conventional wing configuration.

Figure 10: The EPUAV with joined-wing configuration

5 OBSERVATIONS Several important observations have been obtained from the EPUAV project during last

12 years. 1) Students have been motivated by the project to learn about aircraft design. By taking

part in the project, students not only learn to design an aircraft on paper, but they also build and fly the aircraft that they have designed. Almost all of the teams try their best to complete the project to exhibit their ability. The students have to gain knowledge in disciplines such as aerodynamics, structures, propulsion, flight dynamics, control and manufacture during the project. The instructors find that some students might take more effort and volunteer more time than the instructors expected.

2) The project has motivated student innovation. Most of the teams try to design a new ordifferent EPUAV. Some team are successful, but some teams are not, but either way, involvement in the project inspired the students to try new ideas and methods.

Xiongqing Yu

32

3) Through the project students have gained better understanding on the process of aircraftdesign and developments. All of the teams have completed the whole process including conceptual design, preliminary design, detail design, fabrication, and flight tests. Many students said that this experience was unforgettable and that it helped them to gain insight into the process of aircraft design and developments.

4) The students’ skills solving engineering problems were developed during the project.The students encountered various unexpected problems that they could not find the answers to from their books. They had to find a way to solve the problems by themselves.

5) Teamwork has been cultivated during the project. The EPUAV project is quitechallenging for the students, and a lot of work must be completed in 18 weeks. They had to learn how hold the weekly meetings to allocate the workload to the different team members, to discuss the problems they encountered, to make decisions for the design and plan for next step. At beginning of the project, students found some difficulties in teamwork. But after a few weeks, the teams worked well together. They realized that project should be well organized, and that teamwork was key factor for project success.

6) The students gained skills using industry-level software. During the project, studentslearned how to use the professional software such as CATIA, MSC.Patran and CFD. These programs were used extensively in the design and analysis of the EPUAVs. We found that most students were skillful in the use of CAD software CATIA. These skills will be very useful for the students to pursue a career in the aircraft industry.

6 SUMMARY We have carried out the EPUAV projects for more than a decade. The project is quite

challenging for students, and its process is complex. The organization of student teams, instructors, and process monitoring is critical for the success of the project. The feedback from students is quite encouraging. Most of the students said that they benefited greatly from the project. Our observations showed that the practice of the EPUAV project had fullfilled the objectives of aircraft design education.

REFERENCES [1] X. Yu. Senior Design Projects Aimed to Integration, Innovation and Practice. Journal of Nanjing University of Aeronautics & Astronautics (Social Science Edition), 2008 (in Chinese).

[2] http://web.mit.edu/drela/Public/web/avl/

[3]http://www.dept.aoe.vt.edu/~mason/Mason_f/FRICTman.pdf

[4] https://www.meil.pw.edu.pl/add/ADD/Teaching/Software/PANUKL