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Current automobile users have increasingly high demands for vehicle comfort, which has led to greater challenges in the vibration and noise performance requirements of the entire vehicle. As an automotive engineer specializing in mount design, I have gained a deeper understanding of the mounting system after years of work.
The mounting system supports the powertrain installation in the vehicle, controls the displacement of the powertrain, and isolates vibrations transmitted from the powertrain to the vehicle, all concentrated in one system. The durability and vibration isolation of the mounting system are two essential performance considerations during the design process. However, the challenges encountered in optimizing these two performances have become increasingly prominent and require urgent solutions, mainly reflected in the following aspects:
1. Traditional mount design assumes that the powertrain is installed on the ground, calculating the rigid body modes and decoupling rates of the powertrain mounted to the ground. The calculation results, especially the frequencies of the rotating rigid body modes, differ significantly from actual vehicle test results, necessitating more mount development based on real vehicles. The reason lies in the fact that traditional calculations assume the ground’s stiffness to be infinite, which greatly differs from the actual vehicle body stiffness. Even with tools to calculate subsystem performance and manually optimize mount parameters, the performance state of the entire vehicle remains unknown, and the consistency of the system’s performance with that of the entire vehicle cannot be measured, risking adjustments after the real vehicle is completed.
2. Traditional mount design software lacks optimization capabilities, requiring continuous adjustments of the mount dynamic stiffness based on experience and constant trial calculations for performance. Each powertrain typically has three mounts, with at least 18 variables, necessitating a large number of repeated trial calculations, which are not only time-consuming but also difficult to satisfy multiple design objectives simultaneously, making it challenging to determine the optimal solution.
3. After determining the parameters of the mounting system, it is also necessary to consider the impact of manufacturing and installation factors on the mounting system, minimizing the effects of manufacturing and assembly deviations on the performance of the mounting system, which involves robustness analysis. Relying on traditional tools and methods is time-consuming and labor-intensive.
Therefore, it is imperative to seek a mounting design software that can perform optimization calculations while achieving subsystem performance and overall vehicle performance objectives.
An expert in vehicle vibration and noise from a well-known domestic automotive joint venture recommended a powertrain mount design expert system called Vehicle-based Mount Design Expert System (VMD). VMD is a set of expert systems for powertrain mount design developed based on mature theoretical models, combining the latest theoretical research results and practical application cases, and is an optimization software for mounting system design based on vehicle response.
Based on multiple case validations, the VMD expert system effectively addresses the aforementioned issues, and I would like to share the following profound insights:
1. In response to the significant differences between the powertrain mounted on the ground and that mounted on the vehicle body, the VMD expert system includes systems such as the vehicle body and suspension, allowing for the design of the mounting system based on the entire vehicle, while directly obtaining the vibration performance of the entire vehicle, thus establishing a direct link between system design and overall vehicle performance;
It can analyze the energy distribution of the powertrain and vehicle body.
2. The mounting system design process is a continuous iterative optimization process that requires a large number of repeated trial calculations for multiple variables. VMD can simultaneously conduct multi-objective design optimization for overall vehicle vibration performance, rigid body modes, and decoupling rates, automatically seeking optimal solutions, significantly saving calculation time and improving efficiency, while maximizing the simultaneous satisfaction of multiple target requirements;
And can conduct comparative analysis of various optimization schemes.
3. The VMD expert system also includes a robustness design module that can assess the impact of each mounting position and dynamic stiffness on the overall vehicle vibration performance, helping designers quickly identify key positions and dynamic stiffness of critical mounts for relatively precise control, reducing fluctuations in overall vehicle vibration performance caused by assembly and rubber manufacturing errors, ensuring stability of performance during vehicle operation. It meets the requirement of a 6σ normal distribution for sample distribution, satisfying robustness requirements.
In summary, the VMD expert system can achieve powertrain mount optimization design based on overall vehicle performance, improve calculation efficiency, and conduct robustness analysis of the optimization design results, thereby meeting the professional requirements for mounting system design.
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