Based on modelling and experimental validation of the hydropneumatic spring, a non-linear dynamic model is developed for active hydropneumatic suspensions of a special-purpose vehicle. In order to improve the system response to off-road terrain unevenness and vertical impact force, the non-linear system is transformed into a linear one by means of feedback linearization. Furthermore, a sliding mode control strategy is introduced for the purpose of raising the robustness of the system. The simulation results indicate that the present non-linear controller combining the feedback linearization with the linear control algorithm possesses high control accuracy and strong robustness, and the unique requirements for the special-purpose vehicle are therefore fairly well satisfied.

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