Aircraft have a manufacturer prescribed operating flight envelope for safe operation. exceeding
these limits can result in unrecoverable departures or even structural failure. Numerous
commercial aircraft accidents in the past have been attributed to loss-of-control
(LOC) resulting from exceeding the safe operating flight envelope. Hence, real-time knowledge
of the safe operating flight envelope is essential for safe flight operation, a problem
known as dynamic flight envelope assessment. This dissertation explores dynamic flight
envelope assessment from a control theoretic perspective. Two notions of the flight envelope,
namely, the reachable sets and the region-of-attraction analysis are investigated. The
NASA generic transport model (GTM) aircraft dynamics is used as an application problem.
Linear and nonlinear techniques for flight envelope assessment are formulated in the
linear matrix inequality (LMI) and sum-of-squares (SOS) framework, respectively. LMI
and SOS problems are computationally tractable convex optimization problems for which
many semi-definite programming solvers are available.
This thesis also investigated fault detection and isolation strategies. Commercial jet transport
aircrafts make extensive use of active controls. Faults or failures in the flight control
system (FCS) elements like sensors or control effectors can lead to catastrophic failure.
Model-based fault detection and isolation (FDI) filters can provide analytical redundancy
by reliably detecting such faults in the system. Practical application of model-based FDI
filters is limited so far due to poor performance, false alarms and missed detection arising
out of uncertain dynamics of the aircraft, effect of nonlinearities in the system and the influence
of closed-loop controllers. An application of closed-loop metrics to assess worst
case FDI filter performance in the presence of a controller and uncertain dynamics is presented.
Longitudinal GTM dynamics are considered. An H∞ FDI filter and a geometric
filter design are compared using the metrics and the results validated through simulation.
This research was expanded to include synthesis, real-time implementation and flight validation
of robust FDI filters for a small uninhabited aerial vehicle. The influence of different
closed-loop controllers on FDI filter performance is investigated. A comparison is
presented between simulation of the predicted FDI filter performance and flight experiment
University of Minnesota Ph.D. dissertation. December 2010. Major: Aerospace Engineering and Mechanics. Advisor:Prof. Gary J. Balas. 1 computer file (PDF);xvii, 180 pages, appendices A-B. Ill. (some col.)
Dynamic flight envelope assessment with flight safety applications..
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.