Aerospace and Electronic Systems Magazine September 2016 - 2

In This Issue - Technically
FLIGHT TEST AND EVALUATION OF A PROTOTYPE SENSE AND AVOID SYSTEM ONBOARD A SCANEAGLE UNMANNED
AIRCRAFT
The inability of an unmanned aircraft to sense and avoid (SAA) other aircraft is one of the main obstacles to the routine and
regular use of UAS for commercial and civil applications in non-segregated civilian airspace. The aim of a SAA system is to
provide a means of complying with the regulatory requirement to "see and avoid" other aircraft to enable the integration of
an unmanned aircraft into the national airspace system so that the UAS can be used routinely and regularly for commercial
and civilian applications. This article presents the flight test and evaluation results that were undertaken by Project ResQu of
Queensland Australia to develop and flight-test a SAA system for the ScanEagle unmanned aircraft. The restrictive SWaP requirements of small UAS provided our main challenge in the migration of a SAA system from a Cessna 172R to a ScanEagle
unmanned aircraft. Demonstrating SAA technology and quantifying its performance are important steps towards SAA's ultimate aim.

ONBOARD VISUAL SENSE AND AVOID SYSTEM FOR SMALL AIRCRAFT
In this article we present a feasible solution for an onboard vision-only sense and avoid (SAA) system for unmanned airplanes,
which considers only one intruder at a time. Sense and avoid technology is one of the most important features to be developed
before these aircraft can be integrated into common airspace. Most commercial applications based on unmanned aircraft are
cost sensitive, and use small airplanes. It is imperative that this affordable SAA system fit within these aircrafts. Due to the cost,
weight, and power restrictions of the small testbed airplanes, the SAA system components chosen were a monocular camera,
as the input sensor, along with kilo-processor chips for processing. The detection system uses the multi-fovea approach in
order to minimize the computational cost of sophisticated image processing algorithms. Preliminary flight test results with two
small size aircrafts (intruder and own) are conducted, proving the applicability of the proposed methods as proof of concept.
However, the system needs further development before it may be implemented in a commercial product.

AN AUTONOMOUS QUADROTOR AVOIDING A HELICOPTER IN LOW-ALTITUDE FLIGHTS
Drones are the first robots to arrive in smart cities, and collision avoidance with helicopters is among the first barriers to the
widespread use of drones. Communication radios capable of broadcasting traffic information are regarded as a promising solutions to the sense and avoid (SAA) problem for small unmanned aircraft systems (sUAS), especially for high speed flights
where long-range remote sensing is not possible. In this article, we develop a hybrid safety controller to analyze collision
avoidance between a quadrotor and a helicopter. The safety controller is capable of incorporating vehicle dynamics, wind
disturbance, communication delay, and sensor uncertainty, to enable a small quadrotor to perform optimal collision avoidance
with a high-speed helicopter, in autonomous navigations. Simulation shows the effectiveness of the controller.

AN ADVANCED SENSE AND COLLISION AVOIDANCE STRATEGY FOR UNMANNED AERIAL VEHICLES IN LANDING PHASE
The presence of multiple aircraft flying in a shared airspace, such as during a landing phase, raises the risk of conflict and
collision. Moreover, maintaining a safe distance between different airplanes is required for an unmanned aerial vehicle (UAV)
to complete a safe landing. To address this problem, a minimum cost-based sense and avoid (SAA) strategy is proposed to
generate a collision-free trajectory from the initial point to the destination. Firstly, the flight space is modeled as a gridded environment, in which the biogeography-based optimization (BBO) approach is exploited to generate the resolution logic in the
presence of multiple intruders. Secondly, considering that the safety of UAV is directly related to the dynamic constraints, the
differential flatness technique is developed to smoothen the optimal trajectory. Lastly, an energy-based controller is designed
such that the UAV is capable of following the collision-free trajectory. Numerical simulation studies are carried out and presented in this article to illustrate the effectiveness of the developed scheme.

PROOF-OF-CONCEPT AIRBORNE SENSE AND AVOID SYSTEM WITH ACAS-XU FLIGHT TEST
The ability to sense and avoid (SAA) both cooperative and non-cooperative air traffic remains a significant technological barrier
to safe integration of unmanned aircraft system (UAS) into the national airspace system (NAS). To address this need, a team of
government and industry partners developed and successfully flight-tested a SAA system using a Predator® B UAS platform in
2014. This article describes the SAA systems that were flown, how they performed and lessons learned for future development.

IEEE A&E SYSTEMS MAGAZINE

SEPTEMBER 2016

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine September 2016