978-1-61284-798-6/11/$26.00 ©2011 IEEE 5A6-1 MODELING CONFLICTS RESOLUTION OF UNMANNED AIRCRAFT SYSTEM USING A LIGHTWEIGHT DURATION CALCULUS Diogo Branquinho Ramos 1,2 , Rovedy Aparecida Busquim e Silva 1 , Inaldo Capistrano Costa 1,3 , Emilia M. Colonese 1 and José Maria Parente de Oliveira 1 1 Aeronautics Institute of Technology (ITA) Pç. Mal. Eduardo Gomes, 50, São José dos Campos, SP, Brazil 2 National Institute for Space Research (INPE), Av. dos Astronautas, 1758, São José dos Campos, SP, Brazil 3 Federal University of Maranhão, Av. Dr. Anselmo, 2008 Campus VII, Codó, MA, Brazil Abstract Over the last two decades, an interesting area of Brazilian military and civil sectors is the Unmanned Aircraft Vehicle (UAV) development. This article tackles the modeling of conflicts resolution of Unmanned Aircraft System (UAS) using a lightweight Duration Calculus (DC) to verify if the temporal specification and design of the system is correct and to ensure formally that the system implementation meets all its requirements. Moreover, the article proposes a formal modeling (using DC) of a conflicts resolutions set of rules, adapted from Free Flight concept in Communications, Navigation and Surveillance/Air Traffic Management (CNS/ATM). In the adapted approach to UAS, each UAV is surrounded by an imaginary space of two cylinders, which form, respectively, the protected zone and the alert zone. The major contribution of this article is structuring a new scenario application of the conflicts resolution to UAS through formal modeling, using the DC technique to confirm that the models could be implemented without deadlocks and unreachable states, as well as with satisfaction of temporal restrictions. Furthermore, this work uses the state-of- the-art practices in formal methods, including a model checking tool to ensuring correct real-time requirements specification of a real-time critical system. Introduction It became extremely important for the Brazilian military and civil sectors the deployment of Unmanned Aircraft Vehicle (UAV). This vehicle type can be employed in military and civil recognition and surveillance missions, data link, natural resources, energy and oil pipelines monitoring, border security, public safety among others [1]. The authors have developed features related to low cost missions of UAV, in order to reduce time between missions, to provide fast conflict resolutions and graceful maintenance. In this context some missions require that UAV set their procedures at the same time, acting as UAS, where each UAV performs a specific function in the mission context. For example, a first UAV performs the data link functionality, a second UAV follows a moving target and a third UAV approach (attack or intercept) the target. Hence, trajectories conflicts must be rapidly solved avoiding collisions between UAVs operating in a same region, ensuring that each UAV is able to fulfill the “Sense-and-Avoid” (S&A) [2], i.e., monitor all the surroundings of an UAV to maintain the S&A of a collision. To ensure that critical systems with real-time characteristics operate safely, it is necessary to establish a rigorous requirements specification. Real-time Systems (RTS) need to react to certain input stimuli within given time bounds. There are many embedded safety-critical applications and each requires real-time specification techniques. The focus of this paper is on the formal modeling of the conflicts rules resolutions for UAS. Furthermore, we suggest a set of conflicts rules resolutions adapted from the Free Flight Concept in Communications, Navigation and Surveillance/Air Traffic Management (CNS/ATM), but with centralized control in an UAS Control Station, the Duration Calculus (DC) application in formal