The Magazine of IEEE-Eta Kappa Nu October 2017 - 25

A Student-Built Fixed-Wing UAS for Simulated Search-and-Rescue Missions

Fig. 4. Target identified and extracted

model that elects k colors that represent the pixel space
with the least error. The result of the kMeans clustering
is identification of the two colors with the highest pixel
spaces, the color of the target's background, and symbol
color. Figure 4 depicts a target, a blue "H" on a red star",
that has been identified and extracted by the computervision algorithms.

Communications

Communications on the UAS is handled by four
transmitters/receivers. Telemetry data is handled by an
RFDesign 900+ radio operating at 915 MHz. Featuring
high output power and high receiver sensitivity, these
radios were paired with low-gain antennas allowing for
a high degree of freedom in radio orientation. Manual
override for the flight controls operate on the 2.4-GHz
band and features a one-way communication link from
the remote control to the UAS. First-person view (FPV)
video and image transfer are handled by two separate
radios operating on the 5.8-GHz band. Both radios are
configured to operate at different frequencies within the
5.8-GHz band. Due to the limitations of the WiFi-based
radios for image transfer, directional antennas are used,
requiring the implementation of an antenna tracker on
the GCS. Due to the long ranges, Ubiquiti Network's
AirMax technology is used which modifies the existing
802.11 standard to allow for higher losses and higher
latencies. Average in-flight data rates are ~2.5 MB/s
which allows for real-time image transfers.
Link budgets for the radio systems are used to tune the
radios and ensure an operational range of 1 km. Figure
5 shows a diagram of the communication links utilized
by the UAS.

VI. GCS
The GCS is a portable control center that provisions the
facilities needed to interact with the aircraft. Architecturally,
it consists of at least two computers, a router, and the radio
components needed to communicate with the aircraft.
THE BRIDGE // Issue 3 2017

Fig. 5. Communications diagram

One of the computers is dedicated toward operating a
ground station application, Mission Planner [16]. This
open-source software is used to plan flights and monitor
the health (location, airspeed, battery voltage, etc.) of
the aircraft. Figure 6 shows the user interface of Mission
Planner.
Another computer is utilized to interface the onboard
computer. Interfacing the onboard computer is facilitated
by the router which forms an 802.11N wireless point-topoint link between the aircraft and the GCS. A secure shell
is established over this communication link for remotely
interacting with an imaging camera. Images captured by
the camera are synchronized on the GCS computers over
a combination of Windows Network Sharing (Samba) and
File Transfer Protocol SSL (FTPS). IP addresses of all systems
on the router's network are statically assigned beforehand.

VII. Aircraft
When determining the type of airframe that would best
suit the needs and functions of UHDT, both the multirotor and fixed-wing airframe designs were taken into
consideration. Upon analysis, a fixed-wing airframe
offered a longer flight time compared to a multi-rotor
airframe, and for that primary reason, the commercial-offthe-shelf My Twin Dream (MTD) fixed-wing air frame was
selected. The MTD airframe is made of high-quality EPO
foam and equipped with fiberglass rods that run through
the wings for support. The internal volume of the stock
MTD is large enough to house all of the components
necessary for both the electronics and image-processing
subsystems with modifications to the airframe to
properly house each component in their respective
positions. The proper position for each component was
determined by minimizing the overall moment produced
by all components while maintaining an overall center
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Table of Contents for the Digital Edition of The Magazine of IEEE-Eta Kappa Nu October 2017