The Matching Research Of Air Suspension’s Stiffness And Damping

With the increasing demand for riding comfort, vehicles with air suspension system are getting more and more attention. Reasonable matching of air suspension springs and shock absorbers enable the car to get a good riding comfort and handle stability.This thesis is on the basis of a large passenger car air suspension. First through analyzing the characteristic curve of air spring, the paper gets the formula of air spring force and relative displacement. Thesis establishes the rear random road excitation in MATLAB/Simulink, and gets the differential equation of linear kinetic suspension system by linear processing of the air spring force. And the 1/2 simulation model is established in MATLAB/Simulink. Substitute the formula of air spring force and relative displacement into the dynamic differential equation of the nonlinear suspension kinetic Equations rack system, and thesis establishes its half car simulation model in MATLAB/Simulink. By comparing simulation analysis of linear and nonlinear models, results show that nonlinear air suspension system is more real to show cars vibration.Then, based on the 1/2 car model of nonlinear air suspension system, according to damping ratio formula, thesis obtains the damping range of front shock absorber and rear shock absorber. By settling the damping of the rear shock absorber while changing the front, and changing the rear while settling the front, thesis analyses the simulating results of the ride data evaluation, and shrinks the damping range of front shock absorber and rear shock absorber in different conditions. According to this range, thesis combines m function with MATLAB/Simulink, and obtains the 3D diagram of front and rear shock absorber damping and car vertical acceleration, the front and rear damping in minimum acceleration are also obtained by searching at the same time.Finally, by changing the damping of shock absorber, thesis simulates the vibration characteristics of the system before and after controlling the damping. theresults show the effectiveness of controlling.This study showed that: compared with the linear air suspension, nonlinear air suspension is more close to the real vibration of the car. The damping before and after changing is matched with stiffness, and 3 better damping values of full load, half load and no-load are obtained. By changing the damping in different working conditions, it is confirmed that the suspension system after controlling performs better than the original air suspension system.