Hydraulic 4-Port Cartridge Valve Actuator

(To be removed) Double-acting hydraulic valve actuator driven by four pressures

The Hydraulics (Isothermal) library will be removed in a future release. Use the Isothermal Liquid library instead. (since R2020a)

For more information on updating your models, see Upgrading Hydraulic Models to Use Isothermal Liquid Blocks.

Library

Valve Actuators

Description

The Hydraulic 4-Port Cartridge Valve Actuator block represents a double-acting hydraulic valve actuator driven by four pressures. Use it as a pilot actuator for cartridge valves, pilot-operated pressure and control valves, and similar devices. A schematic diagram of the 4-port cartridge valve actuator is shown in the following illustration.

The actuator drives a valve (spool, poppet, and so on) whose position depends on pressures at ports A, B, X, and Y and the spring force. Pressures at ports A and B tend to open the valve, while pressures at control ports X and Y, together with the spring force, act to close it. The model does not account for flow consumption and loading forces, except spring and pressure forces.

Inertial properties of the actuator are accounted for by adding a first order lag between the steady-state and actual valve displacements. The lag is simulated with the combination of the PS Gain and PS Integrator blocks, enveloped by the unity feedback.

The valve remains closed as long as the aggregate pressure force is lower than the spring preload force. The poppet is forced off its seat as the preload force is reached and moves up proportionally to pressure increase until it passes the full stroke.

The force acting on the poppet and the poppet displacement are computed with the following equations:

$F_{P} = p_{A} \cdot A_{A} + p_{B} \cdot A_{B} - p_{X} \cdot A_{X} - p_{Y} \cdot A_{Y}$

$x_{s} = {\begin{array}{l} 0 & for F_{P} < = F_{P R} \\ (F_{P} - F_{P R}) / k_{s p r} & for F_{P R} < F_{P} < F_{P R} + k_{s p r} \cdot x_{\max} \\ x_{\max} & for F_{P} > = F_{P R} + k_{s p r} \cdot x_{\max} \end{array}$

$x = x_{s} \frac{1}{T s + 1}$

where

F_P	Pressure force acting on the poppet
p_A, p_B, p_X, p_Y	Pressures at ports A, B, X, and Y, respectively
A_A, A_B, A_X, A_Y	Areas at ports A, B, X, and Y, respectively. Areas at ports A and Y are block parameters. Area at port X is specified by its ratio to that at port A, A_A / A_X. Area at port B is determined as A_B = A_X – A_A.
x	Actual poppet displacement
x_s	Steady-state poppet displacement
x_max	Full stroke
F_PR	Spring preload force
k_spr	Spring rate

Connections A, B, X, and Y are hydraulic conserving ports associated with the actuator ports. Connection P is a physical signal port whose output corresponds to poppet displacement. Pressures applied at ports A and B move the poppet in the positive or negative direction, depending on the value of the Actuator orientation parameter. Pressures at ports X and Y act in the opposite direction to pressures at ports A and B.

Basic Assumptions and Limitations

The flow consumption associated with the valve motion is assumed to be negligible.
The inertia, friction, and hydraulic axial forces are assumed to be small and are not taken into account.

Parameters

Port A poppet area: Effective poppet area at port A. The parameter value must be greater than zero. The default value is 3.3e-4 m^2.
Port A to port X area ratio: Ratio between poppet areas at port A and port X. The parameter value must be greater than zero. The default value is 0.66.
Port Y piston area: Effective piston area at port Y. The parameter value must be greater than zero. The default value is 1.65e-4 m^2.
Preload force: Spring preload force. The default value is 26 N.
Spring rate: Spring rate. The default value is 1.4e4 N/m.
Poppet stroke: Maximum poppet stroke. The parameter value must be greater than zero. The default value is 5e-3 m.
Poppet-seat initial gap: Initial gap between the poppet and the seat. The parameter value must be greater than or equal to zero. The default value is 0.
Time constant: Time constant of the first-order lag. The default value is 0.01 s.
Actuator orientation: Specifies actuator orientation with respect to the globally assigned positive direction. The actuator can be installed in two different ways, depending upon whether it moves the poppet in the positive or in the negative direction when pressure is applied at its inlet. If pressures applied at ports A and B move the poppet in the negative direction, set the parameter to Acts in negative direction. The default value is Acts in positive direction.