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New Method for Decoupling the Powertrain Roll Mode to Improve Idle Vibration

FCA US LLC-Syed F. Haider, Ahmad Abbas, Francisco Sturla
Published 2019-06-05 by SAE International in United States
Modern engines have high torque outputs and have low RPM due to increased demand for fuel efficiency. Vibrations caused by such engines have to be mitigated. Decoupling the roll mode from the remaining five rigid body modes results in a response which is predominantly about the torque roll axis (TRA) and helps reduce vibrations. Therefore, placing the mounts on the TRA early in the design phase is crucial. Best NVH performance can be obtained by optimizing the powertrain mount parameters viz; Position, Orientation and Stiffness. Many times, packaging restricts the mounts to be placed about the TRA resulting in degradation in NVH performance. Assuming that the line through the engine mount (Body side) centers is the desired TRA, we propose a novel method of shifting the TRA by adding mass modifying the powertrain inertia such that the new TRA is parallel to and on top to the desired TRA. This in turn will decouple the roll mode and reduce vibrations. This problem is formulated as an optimization problem. The numerical examples presented in this paper…
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Mount Rate Robust Optimization for Idle Shake Performance

General Motors Corporation-Thomas Wang, Francisco Sturla, Vicente Cepeda Salazar
Published 2004-03-08 by SAE International in United States
Analytical study of vehicle idle shake performance is standard NVH work within the vehicle development process. Robust design for idle shake performance takes variations into account besides nominal design based performance evaluation. In other words, in addition to the nominal design, Robust Design includes additional evaluations that may incorporate variation due to manufacturing, usage or the environment.This paper presents an example of how to obtain a robust design through performing Robust Optimization on idle shake performance with respect to powertrain mount rates and their tolerance variation. The paper describes a two-phase process that has been systematically implemented to analytically obtain a robust design. In the first phase, performance variation assessment is conducted. Then a Robust Optimization is performed to obtain a robust design. The goal is not only to move the performance onto target, but also to desensitize the system performance to the noises and the anticipated variations (e.g. mount rate variation).
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