Nico-Philipp Walz

A Comprehensive Fuzzy Uncertainty Analysis of a Controlled Nonlinear System With Unstable Internal Dynamics

Fuzzy uncertainty analyses disclose a deeper insight and provide a better understanding of complex systems with highly interdependent parameters. In contrast to probability theory, fuzzy arithmetic is concerned with epistemic uncertainties, which originate from a lack of knowledge or from idealizing assumptions in the modeling process. Direct fuzzy arithmetic can be used to illustrate how parameter uncertainties propagate through a system. In contrast, inverse fuzzy arithmetic can be used to identify admissible parameter uncertainties that obey defined error bounds. In addition, fuzzy arithmetic is capable of providing global sensitivity analyses. Therefore, an improved formulation for inverse analyses as well as a new concept for the computation of global sensitivities is presented. These tools are used here to assess the model-based feed-forward control of a nonlinear system with unstable internal dynamics.This article is available in the ASME Digital Collection at http://dx.doi.org/10.1115/1.4030810.

A GENERALIZED INFLUENCE MEASURE FOR FUZZY UNCERTAINTY ANALYSIS

The influence measures defined within the Transformation Method of fuzzy arithmetic have proven useful for the analysis of systems with epistemic uncertainties. This contribution presents a generalized formulation of these influence measures so that they are applicable for uncertainty analysis in a universal sense where the uncertainties are described by fuzzy numbers or intervals. Formulas are derived exemplarily for the Transformation Method although the measures are likewise independent of the solution method applied.

Simulative and experimental investigations on pressure-induced structural vibrations of a rear muffler

The periodically blown out exhaust gas of a combustion engine may excite structural vibrations of the exhaust system. In addition to the noise of the orifice, these vibrations contribute to the overall noise radiation of the exhaust system. In this work, the excitation of structural vibrations of a rear muffler via the acoustic path is investigated both in experiments and simulations. In both cases transfer functions from the acoustic pressure at the inlet to the structural deflection on the surface of the rear muffler are determined and compared to each other. For the simulation an FE-FE (finite element) coupling is applied to account for the fluid-structure interaction. To efficiently predict the fluid-structure coupled behavior, a model reduction technique for the finite element method based on the Craig-Bampton method and the Rubin method is presented. In a last step, the sound radiation is evaluated by solving the exterior acoustic problem with the fast multipole boundary element method. For this purpose, the results of the FE computation are used as boundary datum.