The increasing pressure on fuel economy has brought car manufacturers to implement solutions that improve vehicle efficiency, such as downsized engines, cylinder deactivation and advanced torque lock-up strategies. However, these solutions have a major drawback in terms of noise and vibration comfort. Downsized engines and lock-up strategies lead to the use of the engine at lower RPMs, and the reduced number of cylinders generates higher torque irregularities. Since the torque generated by the engine is transferred through flexible elements (clutch, torsional damper, gearbox, transmission, tire), these also impact the energy that is transferred to the vehicle body and perceived by the driver. This phenomenon leads to low frequency behavior, for instance booming noise and vibration.
This paper presents a combined test and CAE modelling approach (1D/3D) to reverse engineer a vehicle equipped with a CPVA (centrifugal pendulum vibration absorber). The objectives were to fully understand and predict vehicle behavior with respect to the drivetrain torsional oscillations and low frequency booming noise and vibration. For this purpose, the procedure was divided in two phases: testing and modelling. The testing phase was used to get insight into the vehicle behavior, noise sources and noise transfer paths, using operational measurements. Moreover, dedicated component tests were carried out to obtain parameters to be used in the modelling phase, with the CPVA being the most complex and important component. The modelling phase used the test results as input to build a full vehicle model and to validate the booming noise results. The final model was fit for sensitivity studies and was also used to evaluate the performance of the CPVA, which is dedicated to the reduction of lock-up booming noise. Such an approach is a first step which can accelerate the SDPD (system driven product development) into a consolidated MBSE (model based system engineering) framework.
