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   https://doi.org/10.1002/rnc.5299  

   Fry, J. Micah ; Abou Jaoude, Dany ; Farhood, Mazen ( December 2020 , International Journal of Robust and Nonlinear Control)

   This article presents a dissipativity approach for robustness analysis using the framework of integral quadratic constraints (IQCs). The derived results apply for linear time‐varying nominal systems with uncertain initial conditions. IQC multipliers are used to describe the sets of allowable uncertainty operators, and signal IQC multipliers are used to describe the sets of allowable disturbance signals. The novel concepts of dichotomic nodes and their corresponding factorizations are introduced, which allow for the aforementioned multipliers to be general time‐varying operators. The results are illustrated via the robustness analysis of a flight controller for an unmanned aircraft system tasked to perform a Split‐S maneuver.

    

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   https://doi.org/10.1137/16M1104895  

   Mazenc, Frédéric ; Malisoff, Michael ; Özbay, Hitay ( January 2018 , SIAM Journal on Control and Optimization)
4. Robustness analysis of uncertain time‐varying systems with unknown initial conditions

   https://doi.org/10.1002/rnc.7094  

   Farhood, Mazen ( December 2023 , International Journal of Robust and Nonlinear Control)

   This paper focuses on the robustness analysis of discrete‐time, linear time‐varying (LTV) systems subject to various uncertainties, such as static and dynamic, time‐invariant and time‐varying, linear perturbations, and unknown initial conditions. The proposed approach is based on integral quadratic constraint theory and allows for a potentially more accurate characterization of the set in which the initial state resides by imposing separate constraints on the initial values of the state variables as opposed to simply requiring the initial state to lie in some ellipsoid. The adopted problem formulation facilitates the analysis of uncertain LTV systems subject to disturbance inputs that are bounded pointwise in time, and the developed results enable determining useful pointwise bounds on the performance outputs given such inputs. The main analysis result is given for eventually periodic nominal systems, which include linear time‐invariant, finite horizon, and periodic systems as special cases. The analysis conditions are expressed as linear matrix inequalities. Two additional results stemming from the main analysis theorem are provided that can be used to determine overapproximated ellipsoidal reachable sets. Finally, the utility of the proposed approach is demonstrated in an illustrative example.

    

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   Neelanjana Pal ; Diego Manzanas Lopez ; Taylor T Johnson ( October 2023 , Formal Methods for Industrial Critical Systems. FMICS 2023)