Active aircraft fault detection, accommodation and evaluation of performance reduction

Abstract

One of the principal issues which must be overcome for the safe integration of Unmanned Aerial Vehicles (UAVs) in both militarian and civilian airspaces is how to increase their level of reliability, [1],[2]. In order to improve it and considering that Flight Control Systems were involved in numerous incidents [3], reference [4] suggests to incorporate emerging technologies such as Self-Repairing Flight Control Systems (SRFCS). In this thesis Fault Detection and Diagnosis (FDD) and Fault Tolerant Control (FTC) are understood in this sense. Within the recon gurable ight control problem, the aims of this project are to analyse the conditions in which the aircraft is able to continue its mission in the event of control surface failures and to determine failure induced conditions which will a ect the vehicle in future ight conditions. The recon gurable control scheme relies on information from Integrated Vehicle Health Management (IVHM) and/or from a FDD system. For that reason, a FDD system which is capable to detect, isolate and estimate the occurrence of one or several control surface failures is implemented. The Fault Accommodation scheme consists in the simultaneous implementation of a new operating point after the failure and a Fault Tolerant Control. The oper- ating point computation in faulty mode is based on the aircraft analytical model and considered as an optimal recon guration strategy of the healthy actuators. The boundaries in which the aircraft will be capable to carry on ying in faulty mode are also determined. The control recon guration is performed with a con- trol allocation scheme, providing recon guration when the aircraft is subjected to actuator failures, thereby improving manoeuvrability and survivability of the degraded aircraft. Finally, the reduction of the aircraft ight performance is analysed. For that reason, the contrast of attainable moment subset, the degraded turn performance and the ying qualities after the occurrence of the fault are evaluated. Apart from the evaluation of the degraded performance, analysing the attainable moment subset under faulty conditions is interesting as it can be used in the recon- guration problem. Besides, the degraded turn performance problem is addressed with the objective of being implemented real-time in order to inform to the recon- gurable guidance system, which will guide the aircraft along a trajectory that is compatible with the new ying properties of the aircraft.