A load-sensing hydraulic system is an energy-saving fluid power transmission that supplies "on-demand" flow at a prescribed pressure margin greater than load pressure. In the paper, based on bond graph methodology, a complex and non-linear load-lensing (LS) hydraulic system model is constructed, in which the dynamic behaviours of an LS valve are taken into account. Moreover, a series of experiments are performed to validate the model. Two reduced models based on activity index analysis are

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... ned to achieve a balance between accuracy and complexity. The results indicate that the system order and computation time can be reduced. By quantifying the relative importance of the elements based on activity index analysis, it shows that the inner leakage of the pump plays a major role in system dynamics due to its correlation to the damping coefficient. Furthermore, the results prove the rationality of representing LS pump dynamics with a fourth-order differential equation and the fact that the dynamics of LS valves have not been well-covered in the literature. Highlights • Bond graph modelling of the load-sensing hydraulic system. • Valid bond graph model verified by a series of experiments. • Two reduced models achieving a balance between accuracy and complexity. • The rationality representing the LS pump dynamic with a fourth-order differential equation.