The Bridge - Issue 2, 2019 - 13

Feature

Electrical and Computer Engineering and Amateur Radio

Fig. 4: High speed digital network using repurposed 2.4 GHz routers and Raspberry Pi microcomputers on amateur radio frequencies.

The rover has a biaxial tilt sensor which provides
pitch and roll signals. Short-range ultrasonic sensors
are used to avoid collisions. A tilt compensated
electronic compass with a triaxial magnetometer
measures true magnetic north for navigation.
A triaxial accelerometer and a GPS receiver sends
motion and location data. Thermal sensors are used
for assessing a disaster scene.

Fig. 5: The first and second generation semi-autonomous rover vehicles
using amateur radio frequencies.

Command and data communication for the rover
uses 1200 b/sec AFSK with Hamming error
correction on the amateur radio VHF, 2 meter
wavelength band with 5 W of RF power. Analog
video at 15 frames/second is transmitted on the
amateur radio UHF, 70 cm wavelength band with
2 W of RF power. The processor is an Intel i386EX
single board computer.

Simple reduced length vertical antennas (rubber
duckies) are employed. Subsystem and total power
consumption and the charge of the battery could
be monitored and controlled remotely. Although the
transmitted power is modest, it is more than that
available for unlicensed WiFi (0.1 W).
However, the TUARC K3TU base station uses a high
power, 50 W 2 meter control transmitter and high
gain Yagi antennas on the roof of the Engineering
Building to command and receive telemetry and
video from the rover. Unlike WiFi, an amateur radio
transmission can use high power and gain antennas
which allowed the rover to be operated while at the
Philadelphia City Hall nearly 3 miles away from our
campus. The unique rover operation garnered local
television news coverage. The rover project report is
posted on the TUARC website.
An improved, second-generation rover is now an
ECE capstone design project with a much larger 5
by 2-foot base, an articulating six-wheel design and
four Raspberry Pi microcomputers with its own local
area network. Command and data communication
remain with amateur radio but now also include an
APRS digipeater for extended range. The digital video
transmission uses the European DVB-T standard
executing on a Raspberry Pi. LIDAR augments the
ultrasonic sensors for collision avoidance and a suite
of noxious chemical sensors provides sophisticated
information about the disaster.

HKN.ORG

http://www.aprs.org https://www.arhab.org http://www.broadband-hamnet.org http://www.broadband-hamnet.org https://hkn.ieee.org/ https://hkn.ieee.org

The Bridge - Issue 2, 2019

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