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Iconic Diagrams\Hydraulics\Valves\Basic Valves


Domains: Continuous. Size: 1-D. Kind: Iconic Diagrams (Hydraulics).



This model describes a 4/3-way proportional control valve with second order spool dynamics.


The spool position is indicated by the variable sp:

sp = -1

Flow from p to b and a to t

-1 < sp < 0

Partial flow from p to b and a to t


sp = 0

No flow

0 < sp < 1

Partial flow from p to a and b to t

sp = 1

Flow from p to a and b to t


The flow through the valves is described as laminar/turbulent flow through an orifice. A detailed description of the flow equations can be found in the description of the model TwoTwoWayDirectionalValve.


In the neutral spool position (sp = 0) all valves are closed. A positive overlap indicates that the spool must travel a certain distance before the valves open. A negative overlap indicates that the valves are already open in the neutral position. A 4/3-way directional control valve with negative overlap could therefore also be indicated by the figure below.


The overlap is indicated by the parameter overlap, which is given as a fraction of the spool position. Note that overlap is only active in the neutral position. For the spool position equal to 1 or -1 the valves are completely open or completely closed.


The spool position sp is a function of the input signal spoolpos:


sp = SO(f,d,discrete(spoolpos))


where SO is a second order transfer function to model the spool dynamics. The function is characterized by the bandwidth (f) and damping (d). The valve input position spoolpos should be limited to the range between -1 and 1.


The 4/3-way proportional control valve is implemented with various spool centre configurations. The configurations are shown in the picture below:


When you drag and drop a model in the editor, you will be asked which implementation you want to choose. During modeling you can easily change the spool center configuration:

1.Select the valve model.
2.Click the right mouse button to open the right mouse menu.
3.Click Edit Implementation and choose another implementation




pp, pt, pa, pb,

All terminals of the valve.



fixed volume flow out pp

fixed volume flow out pt

fixed volume flow out pa

fixed volume flow out pb





position of the spool valve: 0 =closed, 1 = open

0 <= spoolpos <= 1





Nominal flow at nominal pressure per edge, spool in the open position [m3/s], Q_nom > 0


Nominal flow at nominal pressure per edge with, spool in the closed position, Q_nom_central > 0





Leakage flow at nominal pressure per edge [m3/s], Q_leak > 0

Nominal pressure per edge [Pa], p_nom > 0

Valve overlap as  percentage of full stroke, -1 < overlap < 1.

Natural frequency, f > 0.