چكيده به لاتين
Improving and optimizing the design of the powertrain mounting system is one of the methods for improving the performance of noise-vibration-hardness or, in short, the NVH of the vehicle. In this research, the aim is to find the optimum stiffness coefficients for each of the engine mount in three directions. At first, the engine and the gearbox were modeled as a rigid model with 6 degrees of freedom, and the engine mounts were modeled in the Kelvin-voight model. An algorithm for calculating the natural frequency of the engine was designed. Then in the next step, by designing a reverse method and using the proposed natural frequency, the designer proceeded to calculate the permissible range for the engine mount stiffness coefficients. This range is also selected by factors such as the behavior of the engine in a idle RPM environment. In the conventional method, the natural frequency of the set is as far away as possible from the vibrational excitation frequency of the engine in idle RPM to prevent the phenomenon of vibration resonance.
In the next step, the optimization technique was used to determine the decoupling vibration modes theory. To optimize the genetic algorithm in MATLAB software was used. In this optimization, the stiffness coefficients of the engine mounts as problem variables, the range of stiffness coefficients and the engine natural frequencies were considered as problem constraints and the matrix of the decoupling of the modes by the kinetic energy matrix of the modes as the objective function. After verifying the model with reference literature, the optimization of the engine mounts class on the EF7-TC engine was considered. The results show that the decoupling of the modes in optimum state compared to the non-optimal state up to 65% and the system response as an index of displacement and rotation of the center of mass of the engine have been using optimized stiffness coefficients improved. There is also a new coordinate system, other than the TRA coordinates, that helps improve optimal results. The results of the natural frequency decoupling from the excitation frequencies and decoupling of the modes have been improved by using the optimized parameters and new coordinate system, respectively, by 21% and 23%.
