Study On Fractional-order Models And Application Of Magneto-rheological Damper In Vehicle Suspension

With the improvement of people's living conditions and the progress of vehicle technology,vehicle has become an indispensable traffic tool in daily life,the consumers have higher requirement to the comfort of automobile.The vehicle suspension system plays a decisive role in the ride comfort,reasonable selection of the material,parameters of suspension and control way,which can greatly improve the driving safety and ride comfort.Magneto-rheological(MR)damper-based suspensions have become a hot point in the field of vehicle vibration control,because they have some attractive characters such as low energy consumption,high security,and fast response.However,the existing model of magneto-rheological damper is either complex or inaccurate,which hinders the application of magneto-rheological damper.Therefore in this dissertation,the subsection fractional-order model of MR damper,the active control and parameters optimization of fractional-order vehicle suspension system are studied by adopting the methods of theoretical analysis,experimental test and numerical simulation.The main studies of this dissertation are as follows:(1)The definitions and properties of fractional-order derivative are introduced.The influence of the order and coefficient of fractional-order derivative on the system is researched based on the single degree-of-freedom fractional-order isolation system,and the concept of equivalent damping coefficient and equivalent stiffness coefficient are introduced.Then,the single degree-of-freedom fractional-order isolation system is optimized based on the optimal control theory and the approximate analytical method.Finally,the response of optimization system is compared with the response of original system through numerical simulation,and the results indicate that the method presented in this paper to optimize the fractional-order system is feasible.(2)The test data of MR damper under different conditions is obtained by using HT-9711 type material fatigue testing machine and DC constant-current power source.Then,the subsection fractional order model of MR damper is presented,and the parameters of the model are identified.At last,the correctness and accuracy of the model are proven by the numerical simulation.(3)The simplified dynamic model of the fractional-order vehicle suspension system is built,based on the vehicle suspension system containing MR damper.Then,the fractional-order vehicle suspension system is optimized by using the optimal control algorithm and particle swarm optimization algorithm respectively.At last,the response of optimization vehicle suspension system is compared with the response of original vehicle suspension system through numerical simulation.The results indicate that the ride comfort is improved in the premise that guarantees the driving safety after the fractional-order vehicle suspension system is optimized by using this method.