Optimal Control For Nonlinear Vibration Of Vehicle Suspension System

With increased requirements of vehicle performance, the optimization of the suspension system based on the linear vibration model has not been able to meet the user’s requirements of the vehicle handling and stability, comfort and safety. In addition, because of the memory characteristics of the materials, spring and damper of the suspension system show the dynamic characteristics of fractional order differential.In order to study the nonlinearity of the suspension system, to characterize the fractional order and to analyze the influence of the fractional order characteristics on the suspension system, the 1/4 vehicle nonlinear dynamic model of single degree of freedom suspension system with fractional-order derivative is built. An optimal control method is presented by using control parameters and applied to the control of nonlinear vibration of vehicle suspension system. The approximately solution is obtained by averaging method. The stability is analyzed and the range of control parameters is gained on the premise of existence of stable solution of the system. The genetic algorithm is used to optimize the control parameters and to find out the optimal values. Taking the attenuation rate and vibration energy of suspension system as objective functions and the stable control parameters as constraint conditions, the optimal control of suspension system has a good control performance.Then, an optimal control method based on linear control parameters is applied to a two degree of freedom suspension system. The amplitude-frequency response is obtained by averaging method. The influencing factors of the nonlinear characteristics of suspension system and the effect of control parameters on the nonlinear vibration of the suspension system are analyzed. The simulation results show that the control parameters of velocity plays the main control role. It can not only suppress the vibration amplitude, but also eliminate the nonlinear characteristic of suspension system.Finally, the influence of linear control parameters, fractional order and fractional coefficient on the vibration of two degree of freedom suspension system with fractional derivative is studied. The nonlinear suspension system based on linear control parameters simulation model is constructed in MATBLAB/Simulink. Simulation analysis of suspension system under single frequency harmonic excitation and random excitation is discussed.