This presentation was made at the NAFEMS Americas "Creating the Next Generation Vehicle" held on the 14th of November in Troy.

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process.

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process.

Resource Abstract

The objective of powertrain Noise Vibration and Harshness (NVH) development is to achieve the desired level of NVH refinement in an efficient manner. Computer Aided Engineering (CAE) is an important part of the NVH development process because it increases development- and design validation efficiency. Integration of CAE tools for System Simulation and Design Optimization enables multi-objective design optimization across multiple physical domains. This paper presents a case study to illustrate the usage of these CAE tools for powertrain NVH optimization.



The NVH error state addressed in this case study is “creep rattle” which manifests itself as objectionable rattle noise inside the passenger compartment of a vehicle when vehicle speed is low, the transmission is in low gear, and the engine operates at idle speed and low load. High torsional vibrations in the powertrain cause “creep rattle”. A powertrain torsional CAE model was developed to identify the root cause of the high torsional vibrations. The model consists of the mechanical components of the powertrain and the engine speed controller. System simulation shows that high torsional vibrations occur when a powertrain torsional mode of vibration is excited by the main engine torque harmonic at the selected engine speed set point. Powertrain system resonance and thus “creep rattle” only occurs when vehicle drag is low. Low vehicle drag causes the powertrain torsional damper to operate in its “Idle-Neutral” operating range instead of its “Idle-Drive (Creep)” operating range. The CAE analysis shows the importance of considering variability in vehicle operating conditions (in this case vehicle drag) in the NVH optimization process. A CAE workflow for design robustness- and trade-off investigations was established that ensures NVH target compliance for both “Idle-Drive (Creep)” and “Idle-Neutral”. The CAE workflow takes into account variability in vehicle drag and variability in powertrain design parameters including engine speed and load. In the future, the CAE workflow will be extended to operating conditions such as vehicle acceleration and engine “start/stop”.