Dynamic Analysis Of Hydro-Pneumatic Suspensions System

Suspension is an important part of modern vehicle, on the ride comfort and safety have agreat impact. Furthermore, for some military vehicles, suspension performance has a directimpact on the vehicle’s mobility, flexibility and accuracy of target hit.Hydro-pneumaticsuspension as the car suspension device is promising.Suspension of the elastic element, andother parts of hydraulic systems have a smaller size and quality, it can be better arranged inthe car and no single shock absorber.Several countries with advanced automotive technologyattaches great importance to this area.China is relatively lagging behind in this regard, inparticular, there is a great gap between foreign countries in the active control of thehydro-pneumatic suspension. Therefore, in this study, hydro-pneumatic suspension weretaken as research object，and with Matlab/Simulink system simulation and analysis，characteristics of hydro-pneumatic suspension’s non-linear stiffness and nonlinear dampingwere deeply investigated, a passive hydro-pneumatic suspension model was established; Onthis basis, a active hydro-pneumatic suspension model with three different control methodswas established,and investigation in the performance of the suspension was carried out andgood results were obtained. Details are as follows:1. Introduction to hydro-pneumatic suspension working principle and several workstate.According to the working principle of the hydro-pneumatic suspension with double airchamber, considering the local pressure loss and thefriction between the piston and thecylinder, it is established that a hydro-pneumatic suspension of non-linear mathematicalmodel.On this basis, the hydro-pneumatic suspension is simulated under the low, mid andhigh frequency excitation.2. It is derived that the dynamics equation of who a quarter of the body ofhydro-pneumatic suspension system. For the non-linear mathematical model of thehydro-pneumatic suspension,the dynamic model of passive suspension was established andsuspension of the structure parameters were optimized,simulate the hydro-pneumaticsuspension system of which optimized the parameters.3.The PID controller, fuzzy controller and fuzzy PID controller’s basic principles isdescribed.PID controller’input is vertical body acceleration,and the proportional, integral anddifferential coefficient is determined with trial method through computer simulation. Fuzzy controller’input is vertical body velocity and acceleration,and according to people’s habits ofmind,a fuzzy controller of hydro-pneumatic suspension is designed with fuzzy logic toolbox.Fuzzy PID controller’input is vertical body velocity and acceleration,and according to the PIDcontroller’s parameters on system response of the impact of the law, a fuzzy PID controller ofhydro-pneumatic suspension is designed.4. Through the active suspension system dynamic equations,adding to three differentcontrollers,a system dynamics simulation model was established.In order to draw the targetcurve of the suspension performance,so the active suspension system under two differenttypes of road surface excitation is simulated. Analyze the results in the time domain andfrequency domain,and compare advantages and disadvantages of various control strategies indifferent excitation.