Research On Dynamic Characteristics And Control Of Air Suspension System For Passenger Car

Aiming at the problem that it is difficult to coordinate the control of vehicle ride comfort and handling stability,this paper takes the semi-active air suspension of 1 / 4 car body as the research object.Based on the fuzzy PID control strategy optimized by genetic algorithm and the sliding mode control strategy with the ideal sky and ground shed as the reference model,three controllers with different emphases,namely,the comfort mode controller,the motion mode controller and the comprehensive mode controller,are designed to improve the vehicle ride comfort,handling stability and comprehensive performance.According to the switching theory,the mode switching system is designed,and the controller mode is switched in real time according to the change of road conditions,so that the vibration damping performance of the suspension can be optimized.The main contents of this study are as follows:(1)A damping pillar composed of air spring and damping adjustable shock absorber is designed.The theoretical knowledge of aerodynamics and fluid mechanics is used to design and calculate the damping pillar.The simulation model of shock absorber and air spring is established by simulation software MATLAB / Simulink.The external characteristics of shock absorber are simulated under sinusoidal excitation signal,and the influencing factors of shock absorber characteristics are analyzed.The vertical stiffness characteristics and frequency characteristics of air spring are studied.(2)The semi-active air suspension model of a quarter car body with two degrees of freedom,the time domain and frequency domain model of road input and the composite road input model are established.The switching theory is applied to establish the damping multi-mode switching system.According to the change of driving conditions,when the switching conditions are met,the corresponding suspension controller mode is automatically switched.The controller changes the length of the plunger valve core by controlling the stepper motor,so as to adjust the damping force of the shock absorber and make the suspension system in the optimal damping mode to obtain better damping performance.(3)The damping controllers are established to improve ride comfort,handling stability and comprehensive performance.Among them,the comfortable mode controller and the motion mode controller are established based on the fuzzy PID controller optimized by genetic algorithm,and the integrated mode controller is established based on the sliding mode controller with the ideal skyscraper as the reference model.Comfort mode controller is mainly used to reduce the vertical acceleration of the body and improve the ride comfort;the motion mode controller is mainly used to reduce the dynamic deformation of the wheel,increase the adhesion between the tire and the ground,reduce the probability of the wheel jumping off the ground,and improve the handling stability of the vehicle.The integrated mode controller can simultaneously improve the body acceleration and wheel dynamic deformation indexes and improve the comprehensive performance.The simulation results show that compared with the passive suspension,the semiactive suspension based on the combined control of multiple control modes reduces the vertical acceleration of the body and the dynamic deformation of the wheel by 22.83 %and 23.36 %,respectively,and improves the ride comfort and the operation stability of the vehicle.