Fault Tolerant Unmanned Air Vehicle Autopilot Design In Presence of Instrumentations Malfunctions

This paper presents a fault tolerant autopilot design for an Unmanned Air Vehicles (UAV). The safety of aircraft has been and will continue to be an important issue in the avionic industries. UAVs have assuming prominent roles in both the commercial and military aerospace industries in recent years. Fault is a physical defect, imperfection, malfunction, or flaw that occurs in some hardware components or instrumentation of UAVs. It is caused by numerous problems occurring at specification, implementation, and fabrication stages of the designing process. It can also be caused by external factors such as environmental disturbances. Fault tolerance is the state-of-the-art solution to build a system that is able to continue performing its intended functions in spite of fault existence. The fault tolerant system decreases the reliability but improves the systemperformance to prevent it from catastrophic problems. In this paper we present a fault tolerant autopilot design for an UAV. This autopilot, in addition to its role in the stability augmentation, attitude control, and flight path control, it tolerates faults or malfunctions which occur in UAV instrumentations such as: GPS, pressure altimeter, and air velocity sensors. The methodology to design a fault tolerant autopilot system is developed here. It consists of two main steps or algorithms. The first step is the fault detection which is the algorithms and processes that detect the fault when it happens in the UAV instrumentations. The second step is the fault masking and isolating mechanism which checks all the instruments signals and eliminates the breakdown instrument from the system data by ignoring its signals. It is also the process of changing the operation mode in order to minimize the effect of fault on the system by modifying or replacing faulty signal using redundant instrument or using the data fusion when more than one source of data is available. In this work, a Matlab model has been designed for a UAV. A suitable autopilot which performs the stability augmentation, attitude control, and flight path control has been developed. Finally, the autopilot is equipped with the fault detection algorithm, the isolation and reconfiguration algorithm which consider some preselected faults or instruments malfunctions. Thesimulation results have shown how the UAV can continue its mission in presence of some faults.

کلیدواژه ها:

Fault Tolerance ، Autopilot ، UAV ، Instrumentations Malfunctions