Research On Matching And Inflation/Deflating Of Suspension System In ECAS-Bus

Riding comfort and control stability has been required more and more strictly with the improvement of our life, and they have become two important performance indexes by which the vehicle succeeds more easily in the competition. The commercial vehicle with ECAS (Electronically-Controlled Air Suspension) has better performance in ride performance, tire earthing ability, control stability, less damage of road and more protection of good compared with those of leaf spring suspension. So, it is very important to research on the Inflation/Deflation, matching and control of ECAS.Firstly, the working principle and running characteristic of air spring and air suspension were introduced. Based on the parameters,such as the effective volume, internal gas pressure, effective area and bearing mass and so on , the thermodynamic basic theory was adapt, the gas state in the air spring was analyzed, the non-linear elastic model of the air spring was built.Secondly, the mathematic equations and dynamic models of 2 degrees-of-freedom of quarter vehicle model and 8 degrees-of-freedom of whole vehicle model were created by Newton, the frequency analysis was done to the whole vehicle model. According to the whole vehicle model, the RMS of acceleration in the seat was regarded as the objection, the damping coefficient of front and rear suspension was treated as design variable, the suspension damping ratio, the dynamic flexibility and dynamic load were accepeted as constraint condition, in order that the matching of suspension stiffness and damping was optimized. The optimization results improved the riding comfort and dynamic load of tire of the vehicle.Thirdly, inflation/deflation characteristic of Isovolumetric vessel and variodenser vessel were used in research on inflation/deflation of ECAS bus. the theoretical derivation of inflation/deflation working conditions of height-positon holding the line + variable load and working condition of height-positon switching + constant load was carried out. In the previous working condition, the curve of air spring stiffness—period of intake/exhaust(switching time of solenoid valve) was gotten by theoretical derivation, and the function was fitted out of the curve.In the latter working condition, the curve of air spring stiffness—period of intake/exhaust(switching time), height—period of intake/exhaust and height—stiffness were by theoretical derivation, and the functions were fitted out of the curves. The test of the latter was done late on it. The results of inflation/deflation in ECAS bus were different matchings of height and damping, and the processes of them had relations with the processes of controlling.Lastly, on the functions of air spring stiffness, height and period of intake/exhaust, the relation of air spring stiffness and optimal damping coefficient of adjustable damper, Fuzzy—PID control system was designed, then controller experiment was done in the bench test and vehicle test. The control effect was better that performance index—vertical acceleration value in the seat of ECAS under Fuzzy—PID control was obviously decreased.