Flight Control Laws Clearance Based on Coverage-granted Multi-strategy Adaptive Global Optimization
Creators: name:  R. RODRIGUEZ ROBLES 
name:   G. VELASCO BARCENILLA 
name:   A. ANTON DIEZ 
name:   N. OUJJA GHANAM 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: FLIGHT DYNAMICS
GNC
AVIONICS
OPTIMIZATION

description: Since the introduction of the first non-experimental digital fly-by-wire system, the exponential growth of the embedded control systems computing power has enabled the military aerospace industry to develop more efficient and agile aircraft. Generally, modern fighters are designed to be inherently unstable for the sake of manoeuvrability and agility, requiring the use of Flight Control Laws (CLAW) to artificially augment aircrafts stability and also to provide safety-critical flight envelope protection functions. The safe operation of these highly augmented aircraft with complex non-linear dynamic characteristics relies on a Clearance of CLAW, a validation and verification process which encompasses a set of Flight Mechanics and Handling Qualities analyses, in which the controllers robustness to plant models uncertainties and sensor measurement errors is evaluated. This assessment usually results in hundreds of millions of cases to analyse, as it must cover all operational flight conditions, aircraft configurations and many other relevant parameters that lie within the target operational envelopes, considering all possible detected and un-detected failures that might occur in service, ensuring there are no potential unsafe conditions left unexplored. The application of global optimization algorithms has demonstrated to be a very effective technique to increase the probability of finding hidden problems arising from parameter combinations and manoeuvres that are not covered in the framework of a typical grid-based Clearance. However, considering the nature of global optimization techniques, a proper balance between exploitation and exploration is of paramount importance to ensure the adequate coverage of the optimization domain while still being able to find local cliff edge problems in the Flight Control Laws clearance. This work presents the features of a coverage-granted Multi-strategy Adaptive Global Optimization algorithm with inter-clearance-criteria information eXchange (MAGO-X) developed by Airbus Defence and Space S.A.U that enable not only to find all violations of the Clearance requirements, including the worst-case scenarios, but also to ensure an adequate exploration and coverage of the optimization space, which is an essential feature to comply with the airworthiness requirements. This ad hoc hybrid optimization algorithm has been developed from [1] to provide excellent exploration vs exploitation capabilities for optimization problems with Multi-Input Multi-Output (MIMO) black-box cost functions that perform a noncompliance measurement of each one of the Clearance requirements. In this paper, we will firstly describe the functionalities of MAGO-X algorithm of [1] which provide an excellent balance between exploration (coverage) and exploitation of the optimization space. We will present coverage evidences of the proposed optimization-based integral methodology of the flight control laws and flight mechanics a Eurofighter Typhoons Clearance. Finally, conclusions, lessons learned and future lines of work will be enumerated.