Study On Parameter Identification,model Development And Optimization Methods Of Semi-active Hydraulic Engine Mount

Vehicle body's lightweight is an unavoidable trend with the development of the automotive technology.Reduction on vehicle mass and increase in the engine unit power both undermine the automobile NVH performance.Therefore,a proper design of the powertrain mounting system is essential to improve the comfort.Performance of engine mounts have evolved from the rubber mount to the hydraulic style.And semi-active or active control engine mounts are more preferred rather than passive control ones,with its better dynamic characteristic adaptability in different operating conditions.Moreover,the semi-active engine mount is one of the most promising NVH technologies.The main work of this paper provides theoretical and experimental research on a semi-active engine mount,where the nonlinear modeling,the parameter identification,the structural optimization and the vehicle matching are all considered due to its significant value either theoretically or practically.The main content of the thesis is as following:(1)According to the development and evolution of semi active engine mounts,a new theory to classify semi active engine mounts is proposed.Comparisons of semi active engine mount's dynamic characteristics under different structural forms are performed,providing the theoretical evidence of the semi active engine mount design.(2)Genetic algorithm is then used to identify parameters of semi active engine mounts.The empirical formula method is employed at the first-time identification of the semi active engine mounts' parameters,from which results are taken as the initial value of the genetic algorithm parameter identification.The results of genetic algorithm parameter identification method and feature point parameter identification method are compared,indicating that the genetic algorithm parameter identification is superior.(3)Based on the dynamic characteristic experiment and the parameter identification.A modified lumped parameter model of a semi active engine mount with variable-stiffness decoupling membrane is established by implementing the polynomial response surface method and other data fitting method to describe and predict the amplitude variable dynamic characteristic of the semi active engine mount.(4)Based on the parameter sensitivity analysis of a semi active engine mount with throttle controlling,the non-dominated sorting genetic algorithm(NSGA-II)with elite strategy is used to optimize the multi-objective structure design issue of the semi active engine mount to maximize the vibration isolation at different frequency bands.And a single degree of freedom vibration isolation test is hence conducted to verify the optimization.(5)After evaluating the index of the vibration isolation performance of semi active engine mounts,a 6-DOF(degree-of-freedom)powertrain model,a 13-DOF model including the powertrain,vehicle body and engine mounting system are established respectively.Natural frequencies,energy decoupling rates and the system response of the hydraulic engine mount or the semi-active engine mount under idle condition are simulated separately.The vibration isolation effect of the semi active engine mount is confirmed by simulation and vehicle testing results.