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Hydraulic Cartridge Valve Actuator

Double-acting hydraulic actuator for cartridge valves

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Valve Actuators

Description

Use the Hydraulic Cartridge Valve Actuator block as a pilot actuator for cartridge valves, as well as pilot-operated pressure and control valves in applications where all the forces, except spring and pressure forces, and flow consumption can be neglected. This block represents a double-acting hydraulic valve actuator driven by three pressures. The actuator drives a valve (spool, poppet, etc.) whose position depends on pressures at ports A, B, and X and the force of the spring. Pressures at ports A and B tend to open the valve, while pressure at control port X together with the spring force act to close it.

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.

Connections A, B, and X 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, with pressure at port X acting in the opposite direction.

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.

  • The clearances between the valve and the washers are not taken into account.

Dialog Box and 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.

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 or equal to 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.

 Restricted Parameters

Ports

The block has the following ports:

A

Hydraulic conserving port associated with the valve inlet.

B

Hydraulic conserving port associated with the valve outlet.

X

Hydraulic conserving port associated with the valve control terminal.

P

Physical signal port that outputs poppet displacement.

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