Optimization method for powertrain mounting systems with uncertain parameters

This paper presents an interval optimization method to improve the design robustness of the decoupling layout and frequency allocation of powertrain mounting systems (PMSs). The effects of the uncertainties or variations of the powertrain inertia properties and design parameters on the optimization results are considered in the optimization process. Generally, it is difficult and costly to determine statistical information with sufficient precision for uncertain parameters, so here interval numbers are used to describe the uncertain parameters and only the bounds of them are required. Robustness indices of interval reliability and interval possibility degree are suggested for characterizing the robustness of PMS decoupling layout and frequency allocation respectively. The interval optimization problem is transformed to an equivalent deterministic one based on the robustness indices. The optimization results of a PMS show that the interval optimization method can significantly increase the robustness of the frequency allocation, especially in vertical and pitch directions. This will decrease the possibility of resonance between the powertrain and other parts, such as the wheel, car body, and frame. In contrast to the deterministic optimization method, although the decoupling ratios obtained by the proposed method decrease slightly, the interval optimization results can meet the decoupling layout requirement from the viewpoint of engineering.