The Research Of First-passage And Optimal Control On Vehicle Vibration Based On Semi-Active Suspension System

Suspension is the basic structure in cars to ride comfortable and safety. Lots of researches on semi-active suspension system have been done at home and abroad, but most of them focus on certainty system. It is necessary to discuss the character of vehicle semi-active suspension system in the frame of stochastic nonlinear dynamics theory for the road excitation is obviously stochastic excitation. This dissertation studies the complex nonlinear phenomenon in the semi-active suspension system and the control strategy using stochastic nonlinear dynamics theory. The main content is as follows:1 Applying the stochastic nonlinear dynamics theory to semi-active suspension system of vehicle considering the impact of random factors. Simplifying road excitation as gauss white noise, establish vehicle semi-active suspension system model based on stochastic nonlinear dynamics theory, considering the law of force and acceleration. The max Lyapunov exponent is calculated by quasi non-integrable Hamiltonian theory and Oseledec multiplicative ergodic theory, the local stability conditions have been obtained; the global stability conditions have also been obtained by judging the modality of the singular boundary; the stochastic Hopf bifurcation is analyzed from the sharp change of stable and joint probability densities, and the parameter condition of stochastic Hopf bifurcation have been discussed through the numerical simulation.2 A two-dimension stochastic nonlinear dynamical model of Semi-Active Suspension System has been presented considering the stochastic factor of the road. The Hamilton function is described as one dimension diffusion process by using stochastic average method, the global stability conditions is also obtained by judging the modality of the singular boundary; the backward Kolmogorov equation for reliability function and the generalized Pontryagin equation for conditional moment of the first-passage time have been established, the numerical results are given according to the classification of boundary conditions and initial conditions of these two equations. At last, the charactor of first-passage on system had been analyzed .3. The optimal control strategy aimed to obtain the maximization of reliable function have been accessed by dynamic programming principles. The optimal control laws are"bang-bang"controls which are derived from the finit control force. Numerical simulations have been done with the backward Kolmogorov equation for reliability function and the generalized Pontryagin equation for conditional moment of the first-passage time which is under control by using finite difference method. The numerical results indicated that the security enhanced when the constrained control force increasd.