Experimental Rattle Source Characterisation Using Matrix Inversion on a Reception Plate

Minimizing rattle noises is becoming increasingly important for hybrid and electrical vehicles as masking from the internal combustion engine is missing and in view of the functional requirements of the office-like interiors of next generation automated vehicles. Rattle shall therefore be considered in the design phase of component systems. One hurdle is the modelling of the excitation mechanisms and its experimental validation. In this work we focus on excitation by loose parts having functional clearances such as gear systems or ball sensors in safety belt retractors. These parts are excited by relatively large low frequency displacements such as road-induced movements of the car body or low order rigid body engine vibrations generating multiple impacts with broad band frequency content. Direct measurement of the impact forces is in many cases not possible. An experimental procedure to measure the multi-degree-of-freedom rattle impact forces in component systems is presented based on a reception plate transfer matrix inversion. The investigated component is mounted on the reception plate and rattle is induced by direct low frequency rigid body excitation of the reception plate. It is shown that the low frequency spectral content of the rattle impacts, which is masked by the direct shaker excitation response, can be recovered using an iterative time-frequency post-processing loop. Experimental validation is carried out in a laboratory setting.