Research On The Optimal Design Of Engine Mounts By Minimizing Transmitted Power Flow Based On Identifying Excitation And Admittance Matrix

Low-end cars in our country always use 4-cylinder 4-stroke engine.Due to the less number of cylinders,there exists heavy unbalanced forces and torques while the engine is running.With the development of automotive technology on light weighting,the rigidity of car body decreases.It aggravates the coupled vibration between the engine and the car body,and brings about more power transmission to car body through engine mounts.Rational design of the engine mounts plays an important role in interior vibration and noise reduction.For optimal design of the engine mount system,researches mostly focus on these two approaches:decoupling method and Transfer Path Analysis?TPA?method.Combining the application in real project,minimizing transfer power was adopted in this paper to optimize the engine mount system.The car body was modeled as flexible body,and the admittance matrix was employed to represent dynamic behavior of car body.By testing the parameters of the engine,the mounts and the admittance matrix between three mounting points,and identifying the equivalent excitation forces at the c.g.of the powertrain,the vibration equation of the coupled system can be established by using Lagrange's methodology.The vibrational response and transmitted power flow in each direction through each mount can be solved in frequency domain.The overall transmitted power flow in frequency band of 50Hz-200Hz was chosen to be objective function,and Particle Swarm Optimization algorithm was employed to minimize it and get the optimum solution for stiffness of the engine mounts.As shown in the research,the transmitted power flow was reduced at most of the concerned frequency band,especially in 50Hz-150Hz.The overall transmitted power flow was reduced about 5.2dB after optimization,which is 4.8dB more than the optimization by TRA decoupling method.Robust analysis of the optimum system shows that the 1^st natural frequency is most sensitive to the stiffness error of left mount,the 6^thh natural frequency is most sensitive to the stiffness error of right mount,and the overall transmitted power flow is most sensitive to the stiffness error of rear mount.