Research On Control And Simulation Of Vehicle Active Suspension

Suspension system is an important part of the vehicle traveling system. It influences ride comfort and handing safety of vehicle mostly. Compared with the passive suspension, the active suspension has more superior properties. According to the motion of the vehicle and the condition of the road, the vehicle active suspension can voluntarily adjust the body posture to make the suspension system always in the optimum damping state. Therefore, it has important practical significance of studying and promoting the vehicle active suspension system.Based on the reference of domestic and foreign vehicle active suspension control theory, this paper focuses on the active suspension control strategy in order to improve the vehicle ride comfort. Furthermore, the Matlab/Simulink software is ued to build and simulate the active suspension model. Specific research work is following:Firstly, this paper determined the RMS value of the body vertical acceleration, suspension dynamic deflection and dynamic tyre road as the perfomance evaluation indicators of suspension system. For random road, it established the mathematical and simulating model of grade C road, which is the form of integrate white noise. After simplifying the suspension system, the 2-DOF and 4-DOF dynamic model based on active suspension were established. With the analytical method of the state space, it established the state equation of the system.Secondly, the 2-DOF suspension system model was chosen as the research object. To solve the difficulty of determining the weight matrix of the linear quadratic regulator(LQR), an improved optimal control method — Genetic Algorithm Linear Quadratic Regulator was presented. This method used global research of genetic algorithm(GA) to determine the weight matrix of LQR control, which can simplify the optimizing process of Q 、 R and N. The Simulation results showed that: after using genetic algorithm to optimize the weight matrix of LQR,the suspension quadratic performance index J gets a relatively large decline. It can effectively reduce the vibration of the vehicle’s vertical direction and improve the vehicle ride comfort.Finally, the 4-DOF suspension system model was chosen as the research object. Based on the fuzzy control theory, this paper designed a two-dimensional fuzzy controller of the active suspension. This fuzzy controller uesd the vertical vibration speed error and error variation of the vertical body at the front suspension(rear suspension) as the input. To improve the adaptive ability of fuzzy controller, the method for obtaining the domain stretch factor by fuzzy reasoning was presented. Then, the variable universe fuzzy controller of active suspension based on the conventional fuzzy controller was designed. The simulation results showed that, compared with the passive suspension, the active suspension using the fuzzy control strategy and the variable universe fuzzy control strategy in this paper can effectively reduce the vehicle vibration, pitching of the vehicle body.The two control strategy both improved vehicle ride comfort and the variable universe fuzzy control strategy was better.