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NANYANG TECHNOLOGICAL UNIVERSITY

SEMESTER 2 EXAMINATION 2009-2010

AE4106 – UNMANNED AERIAL VEHICLES

April/May 2010 Time Allowed: 2 hours INSTRUCTIONS 1. This paper contains THREE (3) questions and has FOUR (4) pages. 2. Answer ALL questions. Write down each step clearly for full credit. 3. This is a CLOSED-BOOK Examination. 4. Marks for each question are as indicated. 1(a) The diagram in Figure (a) below shows the plan view of a butterfly with fully

extended wings. At the instant just before flapping down, the leading edges of both wings of the respective pairs are shifted forward (solid lines in Figure (b)), and the trailing edge of the fore wing is connected with the leading edge of the hind wing.

The flapping is performed around a flapping axis, a line connecting the hinges of the

fore and hind wings. The flapping axis is tilted by an angle of about 30 deg from the body axis, as shown in Figure (b).

(a) planform or the maximum wing span

(b) profile change in ii side view.

Figure 1: Butterfly

Note: Question No. 1 continues on page 2.

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Use this information and Figure 1, explain the mechanism of flapping wing aerodynamics of this butterfly. Draw some diagrams and/or illustrations to complement your explanation.

(25 marks)

(b) You have been tasked to design the new high-altitude, long-endurance surveillance unmanned aerial vehicle (HALE UAV). One of the possible design layouts is the joined wing as shown in figure 2 below. Using the knowledge learned in class, give comment and justify this applicability of this design layout in comparison to the conventional one.

(10 marks)

(a) Top view (b) Front view

Figure 2: Joined wing design layout

Note: Question No. 2 continues on page 3.

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2(a) High Altitude Long Endurance (HALE) UAV is designed to fly at very high altitude, often reaching twice of the passenger transport aircraft cruise altitude, for a long duration of time, sometimes in the order of days. (i) For a fixed-wing HALE UAV with conventional configuration and equipped

with a turbojet engine what are the important design considerations to achieve the mission objectives?

(5 marks)

(ii) Based on the aerodynamic considerations for long endurance in part 2i., describe the likely wing characteristics of such UAV.

(5 marks)

(iii) Discuss the appropriateness and challenges associated with the use of solar cell or fuel cell for HALE UAV

(5 marks)

(b) A UAV is initially designed to have conventional configuration (cylindrical fuselage, straight symmetrical wing, horizontal tail, vertical fin in rear above the fuselage). Due to its functional requirement change, the designer considers modifying the UAV by installing its fin, together with its rudder, on the bottom part of the fuselage while keeping everything else the same, including the distance of the fin’s aerodynamic center behind the aircraft’s center of mass. Give qualitative assessment (with supportive arguments) on the effects of the modification on the static lateral-directional stability and lateral-directional control of the aircraft in comparison to the original design.

(5 marks)

(c) What are the necessary UAV flight control components to allow for autonomous way-point flight operation? Sketch in a block diagram the interconnection between these components in an autonomous way-point navigation system.

(5 marks)

(d) UAV can be categorized based on its level of autonomy.

(i) What are three differences between Remotely Piloted Vehicle (RPV) and autonomous UAV?

(5 marks)

(ii) Describe the level of autonomy of UAV and how this affects the associated operator’s role.

(5 marks)

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3(a) You are developing a UAV capable of conducting a reconnaissance mission autonomously. An autopilot is ready but you need to install navigation systems (sensors). What kinds of navigation systems (sensors) do you recommend to install in the UAV for the mission? Briefly describe your navigation systems.

(10 marks)

(b) Discuss advantages and disadvantages of INS (Inertial Navigation System) compared to GPS (Global Positioning System).

(5 marks) (c) For the mission in (a), the UAV with a EO/IR camera needs to fly at an altitude of

1500 m, and a nominal look-down angle of 45 degrees as shown in Figure 3.

Figure 3: Front view of the UAV

(i) If the camera had a FOV (Field of View) of 7 degrees, can you find the area

on the ground covered by the 7-degree by 7-degree FOV (scene)? (5 marks)

(ii) How many FOVs (scenes) are required for square km (1 by 1 km)?

(5 marks)

(iii) If the mission were to search an area 5km by 5 km in extent, and the clutter were high, an operator would need 20 sec search time per FOV (scene). Sketch your search pattern and find the minimum endurance time (in sec) the UAV requires to fly and search the assigned 25 km2 area.

(5 marks)

End of Paper

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