Numerische und experimentelle Untersuchungen zur Optimierung der Sensorik von adaptiven Steuerungen an doppelwandigen Leichtbaustrukturen

Abstract

Noise, radiated from vibrating structures, is coming increasingly into focus in engineering. In vehicles, the impact on humans can be loss of comfort and also health effects. Therefore active structures are more often used in civil aviation, to achieve the optimum balance between lightweigth design and noise reduction. Active elements like piezoelectric ceramics are integrated in such lightweight structures. The placement of the sensors is of vital importance to the quality of the structure. In this thesis, numerical and experimental investigations are conducted in order to optimize the positions of sensors in double-walled ligthweigth structures. Those double-walled structures show poor sound transmission characteristics in the low-frequency domain. The performance of the adaptive control strongly depends on causality and coherence. Further, the number and the placement of the reference sensors are of great importance, especially at complex acoustic excitations. A numerical parametric study on the sound transmission is performed by means of the variation of the key system parameters in a generic simulation model. Different sensors are implemented in the simulation and evaluated at various types of excitations. The number of necessary reference sensors can be evaluated by a singular value decomposition of the auto power density matrix. Differences can be shown in the use of reference signals from the primary and secondary plate and the cavity. In an acoustical transmission test facility, a subset of sensor concepts are realized and measured under point force and diffuse excitation. The findings are compared to the simulative predictions and a qualitativ agreement can be shown.