Kroneld P., Liedes T., Nevala K., Marjanen Y.

The aim of this study was to create a model of selective hydro-pneumatic suspension element (gas spring and a fluid damper). The model is intended as a basis for a full vehicle selective suspension simulation model. When defining and testing the damping rates for different kinds of terrains, advanced numerical simulation models are very valuable. Also, when investigating different kinds of control algorithms for selecting the optimal damping rate, a model of a selective shock absorber is required. The model was created using MATLAB/Simulink block diagram representation. The model takes account to fluid mechanics, thermodynamics, friction and non-linearities of various sub-elements. Also the electrical system of the driving actuator was modelled. The parameters of the model were chosen so that the model could be scaled for different size of shock absorbers. A set of parameter values were measured from an experimental hydro-pneumatic suspension system and the behaviour of the model and the real system were compared. As a result, a parameterized, non-linear model of a selective hydro-pneumatic suspension element was obtained. The model serves as a sub-model for a full vehicle simulation models and provides an input for a control algorithm to select the damping rate.