Development of a fault tolerant EMAS for MALE UAV

This paper describes the activities carried out by Alenia Aermacchi and Pisa University for the development of a fault-tolerant Electro-Mechanical Actuator System (EMAS) for a Medium Altitude Long Endurance (MALE) UAV application. Provided that the faulttolerance characteristics of an EMAS for aircraft application depends on the whole flight control system architecture, the attention is here focused on the safety analysis and the architecture definition of the single actuator, aiming to point out the effects of the architectural choices on EMAS reliability. The proposed EMAS is developed to be a selfmonitoring equipment. It comprehends a 3-phase permanent magnet synchronous motor with related mechanical transmission and a digital Actuator Control Unit (ACU) implementing both closed-loop functions and health-monitoring algorithms, so that the EMAS is able to be fail-operative in case of some electrical/electronic faults (e.g. power switch fault, motor phase fault) and to revert in fail-safe mode in case of other faults. The goal of the ongoing research program is to develop a demonstrator EMAS with high technological readiness level, capable to be qualified and certified for a new vehicle.