MICRO AIR VEHICLE
ABSTRACT       In the last decade researchers have developed increasingly sophisticated unmanned airvehicles (UAV) for mil...
CONTENTS1. INTRODUCTION2. MAVs3. DESIGN ASPECTS4. PROPULSION5. FLIGHT CONTROL AND STABILITY6. COMMUNICATION AND NAVIGATION...
INTRODUCTION       The concept of micro-sized Unmanned Aerial Vehicles (UAVs) or micro Air Vehicles(MAVs) has gained incre...
MAVs       The MAV has a variety of potential uses in military operations, including localreconnaissance, fire control, an...
PROPULSION       Having explored the predicted lift-to-drag ratio and propeller efficiency for the MAV, wenow consider the...
DESIGN ASPECTS       The simplest design is an MAV that can remain within the line of sight of a small basestation that tr...
MAVs       The MAV has a variety of potential uses in military operations, including localreconnaissance, fire control, an...
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Transcript of "Micro new12"

  1. 1. MICRO AIR VEHICLE
  2. 2. ABSTRACT In the last decade researchers have developed increasingly sophisticated unmanned airvehicles (UAV) for military applications. Increased demands for intelligence are spawning thedevelopment of a smaller next-generation UAV called the micro air vehicle, or MAV. Small enoughto fit in the palm of your hand, an MAV would have an operating range of several kilometers andtransmit detailed pictures back to a portable base station. Potential applications for MAVs, bothmilitary and civilian, are numerous. For most military applications, MAVs would be controlledby local users, operating covertly, to supply real-time data. This article focuses on a militarysurveillance application that uses either visible or mid-wavelength infrared imaging sensors. Asdesigned, the MAV would fly in a low Reynolds-number regime at airspeeds of 10 to 15 m/sec.Propulsion would be provided by a combination of an electric motor with either an advancedlithium battery or fuel cell, or by a miniature MEMS engine, which is a more efficient option.Because of the close coupling between vehicle elements, system integration would be asignificant challenge, requiring tight packaging and multifunction components to meet masslimitations. Next, we see the robust schemes for the detection of extreme MAV attitudes, whereno horizon is visible, and for the detection of horizon estimation errors, due to external factorssuch as video transmission noise.
  3. 3. CONTENTS1. INTRODUCTION2. MAVs3. DESIGN ASPECTS4. PROPULSION5. FLIGHT CONTROL AND STABILITY6. COMMUNICATION AND NAVIGATION7. OPTICAL SENSORS8. CONCLUSION9. REFERENCES
  4. 4. INTRODUCTION The concept of micro-sized Unmanned Aerial Vehicles (UAVs) or micro Air Vehicles(MAVs) has gained increasing interest over the past few years, with the principal aim of carrying outsurveillance missions. The primary payload of these tiny aircraft (~15 centimetres or 6 incheswingspan) is usually a miniature image sensor. Operating in an approximate radius of 600 metresfrom the launch point, μAVs are used to acquire real-time visual information for a wide range ofapplications. According to DARPA (Defense Advanced Research project Agency), μAVs are“six-degree-of-freedom aerial robots, whose mobility can deploy a useful micro payloadto a remote or otherwise hazardous location where it may perform any of a variety of missions,including reconnaissance and surveillance, targeting, tagging and bio-chemical sensing.”Equipped with small video cameras and transmitters, MAVs have great potential for surveillanceand monitoring tasks in areas either too remote or too dangerous to send human scouts.Operational MAVs will enable a number of important missions, including chemical/radiationspill monitoring, forest-fire reconnaissance, visual monitoring of volcanic activity, surveys ofnatural disaster areas, and even inexpensive traffic and accident monitoring. Additional on-boardsensors can further augment MAV mission profiles to include, for example, airborne chemicalanalysis. In the military, one of the primary roles for MAVs will be as small-unit battlefieldsurveillance agents, where MAVs can act as an extended set of eyes in the sky for military unitsin the field. Virtually undetectable from the ground, MAVs could penetrate potential terroristcamps and other targets prior to any action against those targets, significantly raising the chancefor overall mission success. There is now great interest in developing Micro-Air Vehicles(MAVs) that are very small with both fixed and flapping wing designs. As the size of theseMAVs decrease, the amount of thrust and lift that can be generated by the wing will alsodecrease, limiting the weight and payload capacity of the MAV. For very small MAVs withfixed wing designs, this will require critical air velocities that limit the maneuverability of theMAV. Thus, flapping wing designs can be more desirable, enabling the MAV to fly at airvelocities approaching 0 (i.e., hovering), much like a rotorcraft structure. However, the flappingmotion associated with these wing designs can produce thrust and lift forces that are moreunsteady than fixed wing MAVs, which requires new measurement techniques for assessing thetransient characteristics of these forces as a function of the flapping wing design.
  5. 5. MAVs The MAV has a variety of potential uses in military operations, including localreconnaissance, fire control, and detection of intruders. Law enforcement organizations could useMAVs for hostage rescue, border patrol, traffic surveillance, and riot control. For most of theseapplications, a swarm of MAVs could provide wide-area coverage. Much of the appeal of theMAV for covert operations comes from its small size. To determine how “invisible” the MAVwould be on the battlefield, we examined the various means of detection available to potentialadversaries. To the human eye, an MAV in flight would resemble a small bird. MAV radarsignatures would be similar to those of small birds and are thus likely to be lost in clutter.Furthermore, the projected MAV airspeed of 10 to 15 m/sec is below the minimum detectablevelocity for most radars. Infrared search-and-track units would be able to detect an MAV only atshort ranges because of its low power. For an electrically powered MAV, the acoustic signaturewould be dominated by the aerodynamic noise of the propeller, and would be audible only atclose range. An MAV powered by an internal-combustion engine with a muffler could achievesimilar acoustic performance.
  6. 6. PROPULSION Having explored the predicted lift-to-drag ratio and propeller efficiency for the MAV, wenow consider the power required to fly one. Figure 7 shows the flight power (airspeed timesthrust), shaft power, and electric power needed for a range of MAV sizes, with the requirementsfor our baseline 15-cm wingspan highlighted. For conservative choices of lift-to-drag ratio andCL, the baseline flight power is 1.25 W. For a propeller efficiency of 50%, the baseline shaftpower is 2.5 W. If we use an electric motor with 60% efficiency, the baseline electrical power is4.2 W. These values, however, provide only enough power for level flight, and they must bedoubled so that the MAV can turn, climb, and fly in gusty air. To produce this power, weconsidered a variety of efficient and lightweight propulsion systems, including electric motorspowered by batteries or fuel cells, internal-combustion engines, turbines, compressed gas, andpower plants using flywheels or capacitors for energy storage. The majority of these systemsproved inadequate. Compressed gas is not likely to provide enough endurance, and flywheelsand capacitors require significant development to be practical. Microsize turbines underdevelopment at MIT could offer robust performance and be used to generate thrust or electricalpower; however, they require more than three years of development . Fuel cells, particularlythose combining atmospheric oxygen with hydrogen generated by using chemical hydride ormethanol oxidation, have promise, but none have been built in the MAV-size range.Consequently, we focused on the most promising near-term candidates for power—battery-driven electric propulsion and internal-combustion engines. Battery-driven electric propulsionhas three advantages: it avoids the need for consumable fuel, is more reliable than internal-combustion engines, and is quiet. Small electric motors with adequate power densities areavailable.
  7. 7. DESIGN ASPECTS The simplest design is an MAV that can remain within the line of sight of a small basestation that tracks the vehicle, maintains the communications link, and performs navigationcalculations. A vehicle that flies behind buildings or hills—beyond the line of sight—mustdepend on some other approach to communications and needs an independent means ofnavigation. One configuration that meets these requirements stores data on board with laterreadout when the vehicle returns to line of sight. Another configuration includes an overheadcommunications relay. Without a line of sight for navigation, alternative navigation approachessuch as dead reckoning, inertial navigation, and the Global Positioning System (GPS) might betapped, with the latter two depending on the availability of small components. Intelligencegathering around or within buildings requires a hovering vehicle with a sophisticated navigationsystem. Alternatively, the MAV might be able to perch, or fasten itself to a fixed object, or turninto a crawler for local sensing. Combined hovering-flying vehicle possibilities includeconventional main rotortail rotor helicopters, coaxial rotors, propulsiondriven rotors, ducted fans,and tail-sitter airplanes. For some applications, the vehicle would need to be fully autonomousand able to respond to the data received by onboard sensors.
  8. 8. MAVs The MAV has a variety of potential uses in military operations, including localreconnaissance, fire control, and detection of intruders. Law enforcement organizations could useMAVs for hostage rescue, border patrol, traffic surveillance, and riot control. For most of theseapplications, a swarm of MAVs could provide wide-area coverage. Much of the appeal of theMAV for covert operations comes from its small size. To determine how “invisible” the MAVwould be on the battlefield, we examined the various means of detection available to potentialadversaries. To the human eye, an MAV in flight would resemble a small bird. MAV radarsignatures would be similar to those of small birds and are thus likely to be lost in clutter.Furthermore, the projected MAV airspeed of 10 to 15 m/sec is below the minimum detectablevelocity for most radars. Infrared search-and-track units would be able to detect an MAV only atshort ranges because of its low power. For an electrically powered MAV, the acoustic signaturewould be dominated by the aerodynamic noise of the propeller, and would be audible only atclose range. An MAV powered by an internal-combustion engine with a muffler could achievesimilar acoustic performance.

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