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Hydraulic 4-way critically-centered valve
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:
$$q=x{C}_{D}b\sqrt{\frac{1}{\rho}\left({p}_{S}-abs\left({p}_{A}-{p}_{B}\right)\right)}sign\left({p}_{A}-{p}_{B}\right)$$
where
q | Flow rate |
x | Valve displacement, –x_{max} <= x <= x_{max} |
b | Orifice width, b = A_{max} / x_{max} |
A_{max} | Maximum orifice area |
x_{max} | Valve maximum opening |
C_{D} | Flow discharge coefficient |
ρ | Fluid density |
p_{S} | Pressure supply |
p_{A,}p_{B} | Pressures 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.
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.
Specify the area of a fully opened valve. The parameter value must be greater than zero. The default value is 5e-5 m^2.
Specify the maximum displacement of the control member. The parameter value must be greater than zero. The default value is 0.005 m.
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.
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.
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.