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# ANALYST : EM compatibility ANALYsis & Statistical Techniques in aeronautics

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Citation: Morio, J.; Junqua, I.; Bertuol, S.; Parmantier, J.-P. Optimisation of segregation distances between electric cable-bundles bundles embedded in a structure. Appl. Sci. 2021, 1, 0. https://doi.org/ Received: Accepted: Published: Publisher's Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. possible open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecom-mons.org/licenses/by/ 4.0/). Abstract: This paper presents the optimisation of the segregation distance between two electric 1 cable-bundles installed in an aircraft structure under electromagnetic compatibility constraints. We 2 first describe the problem formulation where a probabilistic constraint has to be verified during the 3 optimisation process. To overcome the nonlinearity of the constraint function and guarantee the 4 algorithm convergence, we propose a joint approach between Monte Carlo sampling and Kriging 5 surrogate to estimate the optimum distance with a low computational cost. This methodology is 6 tested on a realistic use-case of distance segregation between cable-bundles. 7

Due to the large amount of electrical equipment aboard modern aircraft, several EMC problems appear which can be tackled by filtering disturbances at the equipment inputs and shielding cable links (braiding, covering, over-braiding). Among the others, the segregation between interfering cables or bundles of cables becomes crucial to ensure that coupling constraints will not exceed the equipment susceptibility threshold. The aim of this work is to statistically characterize the coupling between cable bundles and its minimization by optimization under stochastic constraints. The Monte Carlo method is used, and an interpolation scheme based on Smolyak grids is investigated to accelerate the computation.

Modern aircraft hosts a large number of electric systems. Due to the transition to a More Electrical Aircraft, future platforms will use even more electric systems. This increases the complexity of the EWIS design from an EMC point of view. When possible, segregation between potentially interfering cables or bundles is a convenient solution to avoid EMC problems. Due to the huge number of installation configurations, the evaluation of the minimal segregation distance between two interacting bundles can be unfeasible. To overcome this situation, a specialized tool has been developed, based on a statistical approach for the analysis of the interaction between couples of bundles. In the paper, the different modules needed for this analysis are detailed and described. Some canonical analysis are then reported to show the capabilities of the tool.

Due to the large amount of electrical equipment aboard modern aircraft, several EMC problems appear which can be tackled by filtering disturbances at the equipment inputs and shielding cable links (braiding, covering, over-braiding). Among the others, the segregation between interfering cables or bundles of cables becomes crucial to ensure that coupling constraints will not exceed the equipment susceptibility threshold. The aim of this work is to statistically characterize the coupling between cable bundles and its minimization by optimization under stochastic constraints. The Monte Carlo method is used, and an interpolation scheme based on Smolyak grids is investigated to accelerate the computation.

Segregation rules are one of the three solutions to overcome EMC problems together with filtering of disturbances at the equipment inputs and shielding of cable links (braiding, covering, over-braiding, etc.). These rules enable mass reduction in the selection of cables and optimal route definition in which compatible cables (having similar levels of susceptibility and emissivity) can be installed inside the same bundles or nearby bundles, in the aircraft. The main parameters influencing the design of these "routes" are the distance that separate the routes from each other and the distance from the electrical structure, in order to avoid the effects of friction, electrical arcing (in the event of damage the insulators) and electromagnetic (EM) stresses [1]. Compatibility to environmental constraints [2] is usually obtained by the installation of filters or EM shields. Internal EMC constraints between the "routes" are solved by the application of a minimum distance ensuring that EM coupling constraints will not exceed equipment susceptibility thresholds. We suggest that, to the first order, this minimum distance is determined by modeling a pair of routes of similar length, adjusting and optimizing the segregation distance between them as shown in Figure 1. In this problem, this distance will vary mainly with the nature of the routes (EM sensitive versus EM not-sensitive) but also with the distance of each "route" from the nearest electrical reference, the coupling length and the crossing angle between two routes (as the routes can travel in parallel or cross each other with an angle). Figure 1. Principle for determining the minimum distance between two "routes" Two questions result from this approach: • How to determine this minimum distance considering the large number of configurations that are required? • If it is not possible to respect this minimum distance in the real aircraft installation, what level confidence can we give to lower distances in order to have their installation accepted? The second question is motivated by a significant number of requests for exemption from the cable design teams who have to deal with modifications of the 3D model of the aircraft and from the installation teams who cannot install the harnesses as specified, generally for mechanical reasons. To this extend, we propose to generate segregation distance tables when designing these routes to assess the level of acceptance of exemption distances.