In-situ source characterization for nvh analysis of the engine-transmission unit

Over the past decades, engineers have developed methods to determine critical paths for sound transmission, also known as Transfer Path Analysis (TPA). This demand stems, for instance, from the need to prevent undesired vibrations in modern vehicles. A relatively new method that allows for the characterization of a source in the assembled state is called in-situ TPA (iTPA). Generally, the excitation forces cannot be measured. Although the iTPA makes the development process more complex, it provides insight into the forces generated by active components that are transferred to the receiver structure. The vehicle dynamics as well as its vibration behavior is essentially determined by the behavior of the powertrain. For this more complex system, several challenges affect the method’s applicability, such as the accessibility to the engine mount interfaces and the modeling of coupling degrees of freedom. The aim of this paper is the characterization of the excitation source based on the engine-transmission unit using the iTPA method. It is analyzed and evaluated in terms of its accuracy and applicability. Equivalent forces of two different vehicle configurations, stiff and soft engine rubber mounts, are compared and used to predict the total vehicle vibration responses.