Multi-objective Combination Optimization of Automobile Subframe Dynamic Stiffness

Subframe is an important part of automobile chassis, which is connected with body, suspension control arm, powertrain mount, etc. The dynamic stiffness value of the connection point is an important performance index of the subframe, which affects the vibration of the vehicle body. This paper introduces the basic concept and related theory of dynamic stiffness, derives the theoretical formula of dynamic stiffness, and analyzes the frequency response of the key points of the subframe. In view of the fact that the dynamic stiffness of the subframe of a certain vehicle model is not up to the standard at some connection points, the dynamic stiffness CAE simulation analysis is carried out to determine the frequency range of insufficient dynamic stiffness and the connection points that need to be optimized. The combination optimization method combining size optimization and shape optimization is adopted, and genetic algorithm is used to set multiple mass constraints with multiple shape variables and size variables as design variables, so as to achieve the goal of optimizing the dynamic stiffness of the subframe. The simulation test shows that the dynamic stiffness of each key point of the subframe can basically meet the target requirements under the constraint of 15% increase in the mass of the subframe.