Multiposition Valve Actuator

Multiposition actuator in an isothermal liquid system

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• Simscape / Fluids / Valve Actuators

  Simscape / Fluids / Isothermal Liquid / Valves & Orifices / Valve Actuators & Forces / Valve Actuators

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Description

The Multiposition Valve Actuator block models a multiposition actuator in an isothermal liquid system. It can be used in combination with the 2-Way Directional Valve (IL), 3-Way Directional Valve (IL), or 4-Way 3-Position Directional Valve (IL) blocks. The actuator position is influenced by the input signal and switching time, and not by loading.

Two-Position Actuator Movement

Actuation begins when the signal at port A exceeds 50% of the Nominal signal value. After the time period set by the Switching-on time parameter, the actuator begins to move toward the Push-pin stroke limit. When the input signal at port A falls below 50% of the Nominal signal value, the actuator reverses its direction after the time period set by the Switching-off time parameter. The motion can be interrupted mid-stroke.

Actuator position

In the image above, t_de is the Switching-on time, which is equal to the time periods t_ae and t_ve. In region t_ae, the actuator moves at constant acceleration with parabolic displacement. In region t_ve, the actuator moves linearly, with constant velocity, toward full push-pin extension. The actuator switches direction when the control signal is off:

1. t_dr is a transitional no-displacement time period set by the Switching-off time.

2. t_ar is a period of acceleration with parabolic displacement.

3. t_vr is period of linear displacement toward the actuator Initial position.

When Actuator positions is set to 2, the Actuator travel direction parameter sets the direction of the push-pin motion.

The actuator motion can be interrupted at any time. If the push-pin motion is disrupted mid-stroke, the switch-on and switch-off times are adjusted proportionally to the push-pin position, relative to the push-pin stroke.

Three-Position Actuator Movement

When Actuator positions is set to 3, the signal at port A moves the actuator in a positive direction and the signal received at port B moves the actuator in a negative direction. Only one signal, from one port, is processed at a time. To switch control between ports A and B, or between positive and negative displacement control, the actuator must first move to a neutral position. If the push-pin motion is disrupted mid-stroke, the switch-on and switch-off times are adjusted proportionally to the push-pin position, relative to the push-pin stroke. The actuator motion can be interrupted at any time.

When controlled by the signal at port A, the three-position actuator has the same displacement profile as the two-position actuator when Actuator travel direction is set to Positive. When controlled by the signal at port B, it has the same profile as the two-position actuator when Actuator travel direction is set to Negative.

Ports

Input

A — Input signal

physical signal

Input port, specified as a physical signal.

When Actuator positions is set to 2, this port can either control negative or positive actuator movement, according to the Actuator orientation setting.

When Actuator positions is set to 3, this port receives a physical signal that corresponds to a positive actuator displacement direction.

B — Input signal

physical signal

Input port for negative actuator displacement, received as a physical signal.

Dependencies

To enable this port, set Actuator positions to 3.

Output

S — Actuator position, in m

physical signal

Actuator position in m, specified as a physical signal.

Parameters

Actuator positions — Number of valve position signals

2 (default) | 3

Number of valve position signals. When set to 2, the actuator receives one signal and sets one position signal. When set to 3, the actuator receives a positive and a negative signal and sets one position signal.

Push-pin stroke — Maximum push-pin extension

0.01 m (default) | positive scalar

Maximum push-pin extension.

Switching-on time — Signal transition time period

0.1 s (default) | positive scalar

Transitional time period before the actuator begins to move. The period begins after the input signal rises above 50% of the Nominal signal value.

Switching-off time — Signal transition time period

0.1 s (default) | positive scalar

Transitional time period before the actuator reverses motion. The period begins after the input signal falls below 50% of the Nominal signal value.

Nominal signal value — Nominal signal for fully extended actuator

24 (default) | positive scalar

Nominal signal for fully extended actuator. The actuator motion is triggered when the input signal reaches 50% of the Nominal signal value.

Initial position — Actuator starting position

Retracted (default) | Extended | Neutral

Starting position of the actuator. Retracted and Extended correspond to the actuator push-pin stroke limits.

When Actuator positions is set to 2, the Initial position default is Retracted. When Actuator positions is set to 3, the Initial position default is Neutral. Neutral corresponds to the middle of the Push-pin stroke.

Actuator orientation — Direction of actuator motion

Positive (default) | Negative

Direction of the actuator motion in response to the physical signal input. The Positive setting corresponds to push-pin extension.

Dependencies

To enable this parameter, set Actuator positions to 2.

Model Examples

Sequencing Circuit for Two Rotary Actuators

A sequencing circuit that is based on four check valves installed in the pressure and return lines of the second rotary actuator. The cracking pressure of the meter-in check valves is set high enough to prevent flow into rotary actuator 2 while rotary actuator 1 is rotating, but lower than the pressure that develops once rotary actuator 1 reaches its hard stop. As a result, rotary actuator 2 starts moving only after rotary actuator 1 completes its stroke.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.