Unmanned Aerial Vehicles (UAVs) perform a variety of missions.
They are used by the military and law enforcement. They are used for
environmental research, agriculture, and search and rescue just to name a few.
This paper will focus on two small commercially available UAVs. One of them is the
DJI Inspire1 Quadcopter used for aerial photography and full motion video. The other
one is the Immersion RC Vortex 250 Pro drone used for First Person View (FPV)
racing.
Both of this vehicles are light weight and commercially available
quadcopters. However, their designs, sensor selection and placement differ
depending on their specific missions.
The Inspire1 Quadcopter is designed to take 12-megapixel photos
and produce 4K video. The reason I have chosen this vehicle for aerial
photography and video is its versatility and its unique design. The Quadcopter
design allows the UAV to “hover and stare” which is a perfect feature for image
and video collection. The carbon fiber aero frame is light weight. This allows
for increased battery life and longer flight times due to overall weight
reduction. The smart power management system uses algorithms to estimate the
remaining flight distance and time need to return to base and sends this
information to the pilot. Retractable quadcopter arms with propellers on top
lock in a lowered position when the UAV is on the ground, acting as landing
gear. The arms retract in the up position in flight to allow for 360- degree
unobstructed view for the camera to shoot videos and take pictures. The Inspire1
features auto takeoff and landing modes, allowing for easy handling with
minimal operator training.
This UAV fulfills its mission of aerial video and photo production
due to its high resolution camera sensor and its attachment via an incorporated
3-axis gimbal. It uses brushless servo motors that allow the camera to remain
steady and to be locked on the subject regardless of the UAV maneuvering, which
is important for clear photos. One radio transmitter allows the pilot to
maneuver the UAV and another transmitter permits simultaneous inflight tilting
of the camera to adjust the angle. A real-time picture can be presented to the
pilot on a mobile phone, tablet or HDMI monitor, allowing the user to monitor the
framing from the ground. This capability is provided by the use of the DJI
Lightbridge system within the flight electronics, which features a range of up
to 1.2 miles. The camera gimbal positioning also allows for easy interchanging
of the camera if necessary.
Another sensor which comes in handy during photography missions is
a GPS-based stabilization system, which allows UAV to hover in position even in
crosswind conditions. The GPS also allows the UAV to automatically return
“home” in case of signal loss. It works even if the operator is travelling in
the car or on the boat allowing the return-to-home point to move anywhere
operator proceeds.
The GPS sensor will also allow geo map reference and latitude/
latitude, time and date signatures on the aerial photos. This feature may be an
important factor in some missions, such as real estate imaging, surveillance,
security, and reconnaissance. The user can see where the UAV is located at any
time during flight using live map, which also shows the most recent UAV route. The
UAVs maximum speed is 50 mph, which is fast for such a small vehicle (Aguilar, 2014).
The high definition camera produces video and still images and
features a 1/2.3" CMOS sensor with a 94-degree field of view lens. It
allows for a wide view with an excellent resolution. The camera pans a full
360-degrees, which means that no matter which way the quadcopter turns, the
camera can remain locked on the subject ("Inspire1," n.d.). Figure
1 displays Inspire1 UAV.
Figure 1. Inspire1 with camera sensor.
Adapted from “DJI Inspire1 Quadcopter.” (n.d.). Retrieved from
http://www.bhphotovideo.com/c/product/1097099-REG/dji_inspire_1.html/prm/alsVwDtl
Copyright by DJI.
As we can see, for the mission it is designed, The Inspire1 is an
excellent vehicle. The sensor positioning and stabilization allows it to take
pictures and shoot video. The lightweight airframe and power conservation
system give the vehicle longer on site times. The high definition camera is
excellent for the mission requirements. The GPS sensor is a great addition not
only for the vehicle tracking and operator’s situational awareness, but also
for easy geo reference of the pictures and videos taken by the UAV.
Next UAV to be discussed is The Vortex 250 Pro Racing Quadcopter
Drone by ImmersionRc. This UAV was specially designed for First Person View
(FPV) racing. Its small size, strong airframe, light weight (only 415g without
battery), and fast speeds due to custom race motors allowing it to compete on
the racing circuit. The specially designed skid frame is strong enough to
withstand rough landings. The UAVs carbon arms are deigned tough to survive a
collision with opponents or objects. It also features a lost UAV alarm is case
the vehicle crashes, which allows the user to easily locate the quadcopter.
Figure 2 displays Vortex 250 drone.
Figure 2. Vortex 250 PFV UAV with
forward looking camera placement. Adapted from “ImmersionRC Vortex 250 Pro
racing drone.” (n.d.). Retrieved from
http://www.quadcopters.co.uk/immersionrc-vortex-250-pro-racing-drone-2147-p.asp
Copyright by ImmestionRC.
The Spironet 5.8Ghz antenna allows for a reliable connection with
the pilot. The Fast F3 processor gives the vehicle the ability to be more
responsive to pilot inputs and is able to have a sharp turning ratio. The flight
camera is essentially the eyes of the racer. It is important that it is located
on the nose of the UAV to provide the pilot with the direct view of what is in
front. This sensor placement will allow the racer to avoid the obstacles and
follow a precise flight path. This UAV includes a FatShark 700TVL v2 CMOS
flight camera. It is securely mounted on the front of the UAV. To protect the
sensor from impact it is mounted on a Carbon- fiber plate. The mount also
dampens the camera vibration. The camera tilt can be adjusted to allow the pilot
see the best field view. For the purpose of racing the high definition images
are not as important as for the previous missions, so camera definition is not
as good as the one used in Inspire1 UAV. However, the camera may be quickly
swapped for a high definition one such as Go Pro Hero due to the quick release
mechanism.
The UAV features a wireless video control. NexWaveRF 5.8Ghz
transmitter with Raceband and can broadcast on up to 40 channels. The transmit
channel can be easily changed via remote control. The system allows up to eight
racer to fly together and is controlled via an on-screen display (OSD) so
choosing the clearest channel is done through the flight transmitter. The
Fatshark FPV Goggles allow the pilot to see the picture from the vehicle, as if
he was flying in it. The BlackBox flight data storage can hold up to two
megabytes of flash memory for race review ("Vortex 250," n.d.).
The FPV goggles are displayed in the Figure 3.
Figure 3. First Person View goggles used
with Vortex 250. Adapted from “Cutting edge FPV racing.”(n.d.). Retrieved from
http://www.bladehelis.com/VortexPro. Copyright by ImmersionRC.
Since it is important for the pilot to see and analyze the video in
real time, the Vortex UAV is equipped with the full-graphic OSD, which delivers
in-flight updates of critical parameters. A real-time interface supports
artificial horizons, fighter-jet style instrument panel and a display of flight
information. The UAV status such as battery voltage, communication link are
some of the parameters displayed to the pilot ("Cutting edge FPV,"
n.d.).
A strong airframe, high flight speed, and radio link reliability are
important parameters to consider for a racing drone. A minimal number of
sensors onboard allows for a simple, lightweight, and maneuverable
vehicle. Camera sensor placement with
the forward view allows the pilot to see what is in front. Secure and protected
sensor location is important to prevent damage in case of crash or collision.
As we can see, sensor placement and specific design
characteristics of the UAV varies deepening on its mission requirements. It is
important to take into consideration the specific tasks the vehicle is designed
to perform and consider the sensor placement, datalink capacity, and airframe
construction.
References
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