| With the development of C hina’s economy, the requirements of customers for the comfort, stability and safety of cars are also rising. Shock absorber is the key factor that influences the above indexes, therefore the research on shock absorber has important significance. Traditional hydraulic shock absorber can’t meet people’s demands because of its performance defects. Hence this thesis designed a mono-tube pneumatic shock absorber which has superior performance, and research on its damping characteristics was conducted by simulation and experiments. The main research contents are as follows:(1) The 7 degree of freedom vehicle vibration model is simplified to get the 1/4 vehicle vibration model, and the simplified model is analyzed to obtain the best damping suspension system matching principle. It provides guidance for damping design. The evaluation criteria for suspension system performance is established and three evaluation indexes are obtained, including vertical acceleration of vehicle body, the relative dynamic load of wheel, the dynamic deflection of suspension. This provides reference for evaluation of the shock absorber performance.(2) The motion process and working principle of the mono-tube pneumatic shock absorber are analyzed to obtain the oil circulation model and the force model in different stroke. The mathematical model of the damping force is established. The deformation of the valve plate under the action of the oil pressure is calculated. It’s the key parameter to solve the damping force.(3) The simulation model of damping characteristics of mono-tube pneumatic shock absorber is established by using Matlab/Simulink to study the influence of structure parameters on the damping characteristics, the result shows that: the air chamber pressure, the through hole diameter and the valve plate number and the valve plate thickness which are the key parameters for damping adjustment have great influence on the damping characteristic s; the properties of the oil and the diameter of the piston rod also have influence on the damping characteristics to some extent; the air chamber volume and the piston diameter have relatively little influence on the damping characteristics.(4) According to the requirement of the shock absorber test ing standard, the experimental bench used for the shock absorber testing has been designed and built. The controlling strategies of the shock absorber were studied to obtain the feed-forward and feedback controlling model of its displacement, velocity and acceleration, and make the test bench bandwidth up to 35 Hz to meet the standard requirements. By using the test bench to research on the mono-tube pneumatic shock absorber, the correctness of its simulation model has proved. Also, through doing research on the key structural parameters, the results from simulation have proved to be true and the model has proved to be accurate. Finally, the research on the acceleration attenuation of the mono-tube pneumatic shock absorber was carried out to prove that it has excellent vibration attenuation characteristics and stable operating characteristic. |
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