Low Cost Air Data Computer for UAV in-flight Experimentation

The Italian Aerospace Research Centre (CIRA) is carrying out a national research project, named TECVOL, which aims at developing relevant technologies for fully autonomous flight of fixed unmanned aerial vehicles, from take-off to landing, including mid-air flight and collision avoidance functionalities. Such technologies are tested in flight by means of an experimental set-up constituted by a flying platform, named FLARE (Flying Laboratory for Aerospace Researches), and a Ground Control Station (GCS). The flying platform is an experimental ultra light aircraft with designed empty weight of 281 Kg, max take-off weight of 450 Kg, max speed s/l about 218 km/h, cruising speed about 190 km/h, wing area of 13.2 m2, wing span of 9.6 m and maximum engine power of 100 hp. The FLARE vehicle is also equipped with an avionic system able to put in operation the algorithms developed in the TECVOL project, whereas the ground control station is dedicated, and thus suitably equipped, to supervision and on-line setting of the in-flight experiments. All the critical components of the equipment are Commercial-Off-The-Shelf (COTS) elements. This paper presents the design, development, integration and flight testing of a low cost air data computer (ADC), developed in the framework of TECVOL project. The main aim of this ADC is to provide accurate and reliable data to the Flight Control System (FCS) during the critical flight phases of take-off and landing. The requirements of the ADC are firstly discussed, because they drove the on board sensors selection. These requirements concern mainly the system size and weight and its performances (in terms of data accuracy, output rate and latency) which are essentially determined by the performances required to the flight control system. The choice to realize a custom air data computer is motivated by the absence of any commercial off the shelf ADC able to fit system requirements, because commercial ADCs are generally designed to provide cockpit information and not to be enslaved to a FCS. The software/hardware architecture of the ADC and its integration on board the flying platform are then described. The algorithms developed to compute air data (i.e., altitudes, true air speed, indicated air speed and Mach number) and to perform model based self-diagnostic of the ADC are also presented. This paper also describes the testing process, which includes both laboratory and in-flight tests. Laboratory tests have been carried out using an Air Data Test Set in order to check, before flight, the algorithms and the performances of the sensor setup. Flight tests have been performed for in-flight calibration of the air data computer. In order to demonstrate the effectiveness of the proposed system, in the paper it will be also presented the performances of the proposed ADC during an UAV autonomous mission.