The core of the model is represented by the proportional directional valves which convey the flow to the remote actuators (Figure 2 left side, model in AMESim). In this kind of environment each element represents a function; the elements can be connected and exchange variables following a power port approach. The movement of the main spool is an input of the model (the user control signal), while the movement of the check valves and local compensators are due to the equilibrium of each single spool under the action of pressure and spring effect