Aerospace and Electronic Systems Magazine October 2017 - 48

Electronics and Vision System of a Projectile-Drone Hybrid System

Figure 15.

Picture of the middle part of the GLMAV in the anechoic measurement
chamber and measured 3D radiation pattern.

ence of batteries hiding some radiation directions. Their placement
in the middle part revealed an interaction between the dipoles and
the metallic guides supporting the sliding platform. Radiation measurements at 2.45 GHz were performed in the anechoic chamber
of the ISL for antenna placement in the middle part (Figure 15).
Figure 16 depicts that the better radiation is obtained by polyethylene guides supporting the sliding platform instead of metallic ones.
Finally, the antenna were integrated near the polyethylene rods
in the GLMAV, and the latter was fired on the ISL proving ground,
validating the well operation of the antenna after firings.

SENSOR AND OPTICAL PRISM
The GLMAV observation system is composed of two elements:
the image sensor and the associated optical device. The system
performance is directly correlated with the selection of these two
components.
The choice of the Point Grey Chameleon camera was motivated for three reasons: the USB 2.0 bus interfaced directly with

the Gumstix port, the CCD Sony ICX 445 image sensor, and the
reduced volume. In addition, the camera is low cost and is easily
available on the shelf.
The choice of the optical device was governed by its ability
of visualizations vertically at a height of 100 m and horizontally
at a distance of 10 m. The use of an optical prism for dividing the
visualization area in two zones was preferred compared with the
use of two cameras. The schematic of the optical prism principle
is given in Figure 17. The advantage of this setup is to simultaneously acquire two views on the sensor. The limitation of the transmission by WiFi to images at the VGA quality is possible because
only the interest zones of 640 pixels × 480 pixels are extracted
from the image.
The choice of optics was based on several criteria, including
the aperture, the resolution, and the volume. The resolution must
be sufficient to view a scene at 100 m and identify a face at a
distance of 10 m ahead of the GLMAV. Three lenses with focal
lengths of 3.6 mm, 6 mm, and 8 mm were considered. A test setup
was built for comparing the performance of each lens. Two patterns were located orthogonally at 10 m and 100 m from the setup.
These static tests (Figure 18, left) allowed the choice of the 8-mm
focal length lens and the optimization of the prism dimensions to
embed the observation system in the plastic dome, which is the
projectile nose of the GLMAV. Figure 18 (right) presents the vision
system and the associated electronics to enable the transmission
of signals.

PROCESSING AND SOFTWARE MANAGEMENT
The program for image acquisition, processing, and transmission
is structured according to the architecture "client and server." The
server, that is to say the program on the onboard Gumstix system, runs respecting real-time constraints. It manages the camera

Figure 16.

Measured radiation patterns in the horizontal cutting plane (for metal rods, polyethylene rods, and polyethylene rods with springs) and in vertical cutting
planes (polyethylene rods with springs).

IEEE A&E SYSTEMS MAGAZINE

OCTOBER 2017

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine October 2017