Dragonfly micro-UAV
From ElanVital
Author: Patricia Chandliss
Editor: Amber Kingston
Contents |
Abstract
The Dragonfly micro-UAV is a robotic surveillance drone whose primary objectives are high-quality wide-angle imagery on a discreet and low-profile vehicle with versatile flight characteristics. The Dragonfly accomplishes all these objectives by mimicking the Earth arthropod the true dragonfly (considered one of the most accomplished of fliers and hunters in the insect kingdom) in both shape and capabilities.
Specifications
The Dragonfly is composed of a mesh carbon fiber shell for its superior strength-to-weight ratios, coated in a clear weatherproof resin seal. The body layout generally follows that of the seminal arthropod; with a head containing the imagery payload, a thorax to which the wings and their driving force are attached, and an abdomen or tail which contains the rechargeable battery and wireless antenna.
Imagery
Imagery is gathered through a compound lens architecture shaped generally after the paired compound eyes of the arthropod. Each "eye" contains approximately 800 lenses on a curved surface which allows their combined field of view to cover the entire hemisphere of possible angles. In practice, however, there is about a forty degree cone obstruction immediately to the rear of the "head" which is caused by the UAV's body. Quality is on a par with mid-level digital cameras in well-lit environments; in low-light conditions, quality may drop considerably though many image-manipulation software will have algorithms which can compensate considerably for lack of clarity and artificial artifacts.
The compound lens architecture provides several advantages in both pre- and post-image processing as well as morphological structure.
Each lens is a simple, fixed focal length convex surface capable of gathering about a 75-degree field of view. This allows it to be incredibly thin and laid almost directly upon the photoreceptor substrate. Thus, the UAV's "payload" is essentially a sheet of less than a millimeter's thickness molded to an underlying frame, perfect for miniature applications such as on the Dragonfly.
Because each lens is capturing its own imagery, the hundreds of overlapping views allows for manual focus determination. This is considered a post-processing step. Software can calculate which lens captured the clearest imagery for an object which the user wishes to focus on, and discards image data from other lenses which would blur it. Thus, a snapshot or video of a scene (and, note, that this would be a 260-degree view in all directions of a 3-dimensional axis, not on a single plane) may be "panned" through on the X and Y axes to bring different items in the fore and backgrounds into focus, and even artificially adjust the depth of field. (Note, that this is NOT to be confused with zoom. The Dragonfly may not "zoom" except in the most original sense, of actually moving closer to the target object.)
Audio
Audio pick-up is available as a standard modification on the Model A UAV and as an optional modification on the Model B. The microphone is capable of picking up conversations at casual volumes from up to 5 meters away...beyond that, legibility drops at an exponential rate due to the physical limitations of the microphone. Ideally, the dragonfly is at rest when attempting to eavesdrop - however, in the case where it may be in flight at the time, an audio processor automatically filters out the frequencies which the wings emit at the time, yielding a less-than-ideal, but still understandable recording.
Flight Capabilities
The dragonfly arthropod is an extremely acrobatic flyer, capable of making nearly 90-degree corners in all directions with almost no loss of speed, a maximum sustained airspeed of 35-40 mph (making it the fastest flying Earth insect), and sustaining a perfectly stabilized hover. The arthropod accomplishes this by coordinating its two pairs of wings in four wingstroke types (see Appendix B). The micro-UAV mimics these four wingstrokes, powered by artificial polymer muscles. (See section on Navigation for the role of the autopilot in wingstroke selection and synchronization.)
The UAV has a basic on-board autopilot. Depending on the model, the autopilot may only provide the most basic navigational capabilities, or a wider range of flight behaviors for the UAV.
- Coordinates wing movement. This includes not only synchronization and angling of wings with each stroke, but also includes determining which of the 4 types of wingstrokes (see Flight Capabilities) would best accomplish the maneuvers requested.
- Coordinates landing and takeoff. The tips of the UAV's "legs" utilize Van der Waals forces to allow the Dragonfly to "perch" upon any available surface.
There are two ways in which the Dragonfly navigates:
- Waypoints. The Dragonfly may navigate via an uploaded set of navigational waypoints, relative to the base station. Due to the limitations of the on-board microprocessor power and memory capacity, the UAV is unable to navigated itself through a given set of obstacles - instead, if there is a door one wishes to navigate through, one must provide the appropriate waypoints so that when the UAV flies in a straight line between them, it will not hit the door's sides.
- Manual control. An operator may provide manual direction to a Dragonfly using a joystick or keyboard controls. This is most likely the most natural and often used mode for directing the UAV.
Communications
The UAV communicates with a base station via a wireless transmitter located in the tail, or "abdomen". The transmitter performs two-way communications - downstream carries imagery data, metadata tags, and basic telemetry such as relative position coordinates, status of onboard systems, and acknowledgments; upstream carries navigational directives and system commands.
Depending on the model, the maximum range for receipt of imagery is 1,000 feet or 2,500 feet without interference. If either the base station or the UAV is inside a building, the building's materials may shorten the range of transmission. If there is enough interference to affect communications, imagery - which requires a larger bandwidth - may be affected first. Thus, in cases where no clear imagery may be obtained, one might still be able to issue navigational commands to the Dragonfly and receive flight telemetry. If all communications are cut off, the Dragonfly will either perch upon the first surface it can find which is above sixteen feet from the ground level, or else return by following precisely the path it had taken away from its original launch point (which method it selects needs to be set during pre-flight checks).
Endurance
Depending on the model, the Dragonfly has an average endurance of 1-1.5 hours or 2-3 hours depending on how much of its power is being used for flight, the most draining feature of the UAV. There are several aspects of its design which contribute to this endurance time or which may extend it:
- Mesh carbon fiber frame: Carbon fiber has superior strength-to-weight ratios which makes it the ideal material to form the UAV's shell. A drawback is the lack of EM shielding in case it is being used in an area where Celestians are known to frequent; however, between the system's ultra-low wattage and its ability to simply rise above the distance in which the Celestian reaction may occur, it was deemed an acceptable trade-off to maintain the UAV's maneuverability and flight-worthiness.
- Transparent solar cells: The wings are composed of transparent solar cells which automatically charge when there is at least 3,000 lux of light. At maximum output and with constant UAV operation, the solar cells can expand the Dragonfly's endurance by another 2-3 hours. If the UAV is at rest and is in standby mode (i.e. - all systems are shut down but for wake-on-magic-packet detection) it may be recharged via solar cells completely in 3-4 hours. This is three times as long as charging by conventional wall-outlet adapter.
Models
There are two models currently in production, one aimed toward urban environments with longer endurance, and the the second for applications in the Wild where the environment is much more unpredictable.
Model A
Intended generally for urban applications where navigation is primarily around and through man-made structures, the Model A is both physically smaller and has a shorter range of communication, though this also translates into a longer endurance time. Due to size limitations, it is built with a more basic processor and, thus, a more limited autopilot.
General stats
- Length: 3 inches
- Operational distance with video: approx. 1000 feet
- Endurance: 2-3 hours
Model B
Intended generally for usage in the Wild where navigation is trickier depending on the local flora and fauna, the Model B is physically larger and has a longer range of communication, but lower endurance. Built with a more advanced processor, the autopilot functions have also been expanded to include more "defensive" behavior, such as ensuring that it maintains at least a certain amount of airspace between itself and all other obstructions - including dodging attempts to snatch or swat it, though its success will vary depending on the speed of the attack.
General stats
- Length: 5 inches
- Operational distance with video: approx. 1500 feet
- Endurance: 1-1.5 hours
