Documentation

4-Way Ideal Valve

Hydraulic 4-way critically-centered valve

Library

Directional Valves

Description

The 4-Way Ideal Valve block represents a 4-way critically-centered valve, where initial openings of all four variable orifices are equal to zero. This significantly simplifies the model of a 4-way directional valve and makes it especially suitable for real-time and HIL (hardware-in-the-loop) simulation, where such assumption is applicable.

The flow rate is computed with the equation:

q=xCDb1ρ(pSabs(pApB))sign(pApB)

where

qFlow rate
xValve displacement, –xmax <= x <= xmax
bOrifice width, b = Amax / xmax
AmaxMaximum orifice area
xmaxValve maximum opening
CDFlow discharge coefficient
ρFluid density
pSPressure supply
pA,pBPressures at the load ports A and B, respectively

Connections A and B are conserving hydraulic ports associated with the valve load ports. Connections P and S are the physical signal input ports that provide supply pressure and valve displacement values, respectively.

Basic Assumptions and Limitations

  • The valve is of a critically-centered type, that is, all initial openings are equal to zero.

  • The return pressure is assumed to be very low and can be treated as a zero pressure.

  • All the orifices are assumed to have the same shape and size, that is, the valve is symmetrical.

Dialog Box and Parameters

Valve passage maximum area

Specify the area of a fully opened valve. The parameter value must be greater than zero. The default value is 5e-5 m^2.

Valve maximum opening

Specify the maximum displacement of the control member. The parameter value must be greater than zero. The default value is 0.005 m.

Flow discharge coefficient

Semi-empirical parameter for valve capacity characterization. Its value depends on the geometrical properties of the valve, and usually is provided in textbooks or manufacturer data sheets. The default value is 0.7.

Global Parameters

Parameter determined by the type of working fluid:

  • Fluid density

Use the Hydraulic Fluid block or the Custom Hydraulic Fluid block to specify the fluid properties.

Ports

The block has the following ports:

A

Hydraulic conserving port associated with the actuator connection port.

B

Hydraulic conserving port associated with the actuator connection port.

P

Physical signal port that controls the supply pressure.

S

Physical signal port that controls spool displacement.

Examples

The Hydraulic Closed-Loop Actuator with Fixed-Step Integration example is an example of using this valve, along with other blocks optimized for real-time and HIL simulation.

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