Research on optimal control, stabilization and computational algorithms for aerospace applications

The research carried out in the areas of optimal control and estimation theory and its applications under this grant is reviewed. A listing of the 257 publications that document the research results is presented

Self-Triggered and Event-Triggered Set-Valued Observers

This paper addresses the problem of reducing the required network load and computational power for the implementation of Set-Valued Observers (SVOs) in Networked Control System (NCS). Event- and self-triggered strategies for NCS, modeled as discrete-time Linear Parameter-Varying (LPV) systems, are studied by showing how the triggering condition can be selected. The methodology provided can be applied to determine when it is required to perform a full (``classical'') computation of the SVOs, while providing low-complexity state overbounds for the remaining time, at the expenses of temporarily reducing the estimation accuracy. As part of the procedure, an algorithm is provided to compute a suitable centrally symmetric polytope that allows to find hyper-parallelepiped and ellipsoidal overbounds to the exact set-valued state estimates calculated by the SVOs. By construction, the proposed triggering techniques do not influence the convergence of the SVOs, as at some subsequent time instants, set-valued estimates are computed using the \emph{conventional} SVOs. Results are provided for the triggering frequency of the self-triggered strategy and two interesting cases: distributed systems when the dynamics of all nodes are equal up to a reordering of the matrix; and when the probability distribution of the parameters influencing the dynamics is known. The performance of the proposed algorithm is demonstrated in simulation by using a time-sensitive example

Phase-field modelling of failure in hybrid laminates

In this paper, the complex failure process of unidirectional hybrid laminates under uniaxial loading condition is reproduced and investigated by a one-dimensional phase-field model. The key ingredients of the approach, describing the mechanical response of a hybrid composite made of two different layers, are: (i) a phase-field method, based on a variational formulation of brittle fracture with regularised approximation of discontinuities for the two layers, (ii) cohesive law for the adhesive interface that connects the layers and (iii) robust and consolidated numerical strategy for the solution of the non-linear discretised problem. Explicit and well detailed simulations are shown for four peculiar failure mechanisms and the outcomes validated against experimental results available in literature. The model is able to discriminate among these different failure mechanisms according to the geometrical and mechanical properties of the hybrid composite. Both delamination of the adhesive interface is followed and crack patterns within the materials are fully determined. Finally, the proposed approach opens new perspective studies in higher dimension settings