Zephyr: A High Altitude Long Endurance Unmanned Air Vehicle ...

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The sensor was powered using an external power supply and was controlled by aservo actuator. The servo was connected to the vane and could be controlledexternally to make the vane move and replicate the movements it would face onboard<strong>Zephyr</strong>. The movement of the vane caused the brush to move along the resistive trackwithin the potentiometer casing thus changing the voltage output which could bemonitored outside the chamber. An oscilloscope was also connected to the sensor toenable and voltage to be seen on screen as well as on the voltmeter. This allowed anyvoltage spikes to be seen easily rather than having to be read from the voltmeter(Appendix 4).4.3 ResultsBoth tests were completed without any problems. The voltages recorded were asexpected and there was no spiking evident in either test at any temperatures. Theprevious sensor lost contact at -83C, -74C and 70C but the modified sensor keptcontact at all times.Although the testing was supposed to be conducted at 50 mbar, there was a problemwith the chamber meaning that it could not get to a low temperature at such a lowpressure. It was decided that the temperature was the most important variable and thatincreasing the pressure by 50 mbar to 100 mbar would not affect the results greatly.The first test which was conducted in order to compare results with the previoussensor was mostly completed at 50 mbar (see Appendix 5).52
After the tests were completed successfully, I decided to test the sensor further byleaving it in the chamber overnight at -100C with the servo constantly moving thevane. This would enable us to find if the sensor would be able to endure constantmovement at such a cold temperature. The sensor would never have conditions thisharsh on the aircraft so if it managed to survive the overnight test it would giveconfidence that it would definitely work onboard the aircraft.After 15 hours at -100°C, the vane was still working and still outputting the correctvoltages. It was then switched off to see if the potentiometer would freeze when not inuse (the original sensor lost contact due to the freezing of the lubricant) and thenswitched on again to see if it would lose contact, but again it performed perfectly.Once all the tests had been completed and the sensor being tested was removed fromthe chamber, the sensor was examined to see if it had suffered any wear. It was notedthat there was no damage to any part of the equipment, and even though there was nolubricant between the brush and the track, there was no damage to the resistive track.4.4 ConclusionAfter testing the modified angle of attack sensor, it was concluded that it performedbetter than the original sensor and does not lose contact (which would have caused thevoltage to spike to 0V). With that in mind, it was recommended that the modifiedsensor should be used instead of the original angle of attack sensor onboard <strong>Zephyr</strong>.53
Page 1 and 2:
Zephyr:A High Altitude Long Enduran
Page 3 and 4:
AcknowledgementsI’d like to thank
Page 5 and 6:
ContentsChapter 1 - Introduction an
Page 7 and 8: Chapter 1Introduction and Backgroun
Page 9 and 10: 1.1 History of ZephyrZephyr is a li
Page 11 and 12: The Zephyr 5 project continued with
Page 13 and 14: airframe, with the main aim to impr
Page 15 and 16: 1.2 Environmental IssuesDuring the
Page 17 and 18: order to function, they may not thu
Page 19 and 20: 1.2.3 Cosmic RaysCosmic rays are en
Page 21 and 22: wind speeds. This is to ensure that
Page 23 and 24: crystalline silicon cells and can b
Page 25 and 26: which are then insulated. In order
Page 27 and 28: motion of the aircraft including ro
Page 29 and 30: Within the portable cabins the crew
Page 31 and 32: Simple payloads instructions withou
Page 33 and 34: In the event that the wing does not
Page 35 and 36: Graph 4 shows radiosonde density da
Page 37 and 38: 3.2 NIOSH Lifting EquationThe hand
Page 39 and 40: Variable Description MultiplierD (c
Page 41 and 42: Using the given values, the corresp
Page 43 and 44: 3.3 Airspeed SensorThe current airs
Page 45: 12VSensorPCBZenerDiodeFigure 8. Dia
Page 48 and 49: 3.4 PayloadThe payload is the carry
Page 50 and 51: where λ is the wavelength, c is th
Page 52 and 53: 3.5 Angle of Attack SensorThe angle
Page 54 and 55: The magnetic sensor seemed much mor
Page 56 and 57: Chapter 4Angle of Attack Experiment
Page 60 and 61: It has to be noted however, that on
Page 62 and 63: experience the atmospheric conditio
Page 65 and 66: 5.2.1 Aerial PhotographyThe most co
Page 67 and 68: meaning that these cameras can be u
Page 69 and 70: Infoterra have a project called Far
Page 71 and 72: it out for long endurance missions.
Page 73 and 74: Figure 18. QinetiQ’s Zephyr5.4 Co
Page 75 and 76: where it is needed rather than havi
Page 77 and 78: Appendix 3Schematic diagram of the
Page 79 and 80: Appendix 5The results table for the
Page 81 and 82: BibliographyQinetiQ Documents[1] St
Page 83: [19] Encyclopedia Britannica, 2004.
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