| As people’s requirements for driving experience increase,active suspension has become a research hotspot in the automotive field.As a kind of active suspension,air active suspension can take into account the ride comfort and handling stability of the vehicle.However,the air active suspension adopts graded stiffness control,and the purpose of adjustment is mainly to control the height of the vehicle,which limits its ability to improve the damping performance.In order to achieve stepless control of stiffness without changing the height of the vehicle body,a research on the damping pillar of the air active suspension was carried out.In this paper,the designed magnetorheological damping strut is used as the actuator of the active suspension,and a multi-objective control strategy based on hybrid fuzzy control is designed for the active suspension,which improves the handling stability while ensuring ride comfort.The main research work of the thesis is as follows:Firstly,a design scheme of combining magnetorheological materials with air active suspension damping struts is proposed,and the structural parameters of the damping struts are determined.Make prototypes according to the design plan,carry out bench tests,test the damping characteristics and stiffness characteristics of the prototypes,and verify the performance of the prototypes.Secondly,the mathematical model of the suspension system is established,and the mathematical models of the damping unit and the elastic unit of the damping pillar are respectively established,and the mathematical model of the damping pillar is identified based on the data obtained from the test,and accurate mathematics is established according to the identification results model.In addition,a road input model and a vehicle suspension dynamics model were established to lay the foundation for subsequent active suspension control.Third,a multi-objective control strategy based on hybrid fuzzy control is designed.According to the control objectives,the suspension control is divided into three control modes: comfort mode,safety mode and performance mode.A switching control system and four control modes for different suspension indexes are designed.The fuzzy controller selects the fuzzy controller according to the needs of the control mode,and calculates the coordination coefficient between the fuzzy controllers through the genetic algorithm,so as to obtain the force that can optimize multiple indexes at the same time.The stiffness controller is used to solve the optimal stiffness under the working conditions to achieve the goal of stepless control of stiffness.Finally,the control performance of the multi-objective control strategy based on hybrid fuzzy control and the advantages of stepless control of suspension stiffness are verified.Simulink and Carsim are used to simulate the random road input conditions,impact road input conditions,and emergency braking.Simulation of four working conditions of working conditions and double shifting working conditions to analyze the control effect of the control strategy under a variety of working conditions.The simulation results show that compared with the vertical fuzzy control alone,when the multi-objective control strategy is in the comfort mode,the damping ability is improved due to the participation of the stiffness controller,and the rms value of the vehicle body vertical acceleration is reduced under random road input conditions.When the multi-objective control strategy is in the safe mode,the vehicle has good handling and stability.Under random road input conditions,the vehicle body roll angle acceleration and the dynamic load of the right front wheel are reduced by 16.3%and 17.6%,respectively;When the target control strategy is in the performance mode,the effect of restraining the body change is good.The root mean square value of the pitch acceleration of the body and the body roll acceleration under the impact road are reduced by 14.9% and 9.91% respectively,which improves the suspension to suppress the body’s pitch motion and The ability to roll motion;the rms value of the pitch acceleration of the body under emergency braking conditions is reduced by 13.3%,which improves the ability to suppress the pitch motion of the body;the rms value of the pitch acceleration of the body under the double-line shifting conditions is reduced23.4%,which improves the ability to restrain the body’s roll motion.The research results show that the multi-objective control strategy based on hybrid fuzzy control can take into account the comfort and handling stability of the vehicle under different working conditions. |
