Evaluation of the Avoiding Strategies for a Prototype Sense and Avoid System of Small Size UAVs

This activity is part of a research project aiming to develop Rotary-Wing UAVs (RWUAVs) starting from small commercial rotary wing aircraft models. In this work, preliminary avoiding strategies for a prototype Sense and Avoid (SAA) system of a small-size RWUAV are presented. In addition, a simulation tool has been developed to test and validate the SAA logics, able to simulate the interactions between the SAA system, the Flight Management System (FMS) and the aircraft dynamics. Currently, the prototype SAA logics manage potential collision risks both in the presence of fixed obstacles and moving obstacles for the cruise phase only. The developed SAA algorithm acts by means of two sequential phases: if the sensed obstacle is classified dangerous (high probability of collision occurrence), an avoiding trajectory is then elaborated and commanded by the SAA to the RWUAV FMS; at the end of this phase, when the obstacle is overcome, the SAA elaborates a new trajectory in order to regain the original flight path. The tool allows to simulate autonomous missions of a reference RWUAV. It is composed by models describing the dynamic behaviour of a small-size helicopter, by flight control laws and by a flight management system that sends input signals to the autopilot control laws on the basis of the waypoints coming from a pre-defined mission, possibly modified by the SAA logics. The paper illustrates the main results of some simulation tests in order to illustrate the dynamic response of the RWUAV, the correct interaction between the FMS and the control laws, and the actions of the SAA logics in presence of obstacles along the RWUAV flight path.