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Fluid Power Pro

Tag Archive: valve

Proportional control calculation. Part 2.

Part 2. Proportional control in the regeneration mode.

Regen mode - proportional control

Fig.1. Regeneration mode schematic

See also:
Part 1. Proportional control of double acting hydraulic cylinder.
Online calculator for cylinder proportional control.

The goal of the calculation is definition of a cylinder velocity at the current operating voltage at the valve’s solenoid.
For calculations we need to know: cylinder and valve parameters (take them from manufacturer catalog), values of forces at cylinder rod (load) and pressure drop at return line (can be assumed as zero if unknown).

Summary:
2.1. Regeneration mode schematic
2.2. Regeneration Mode: Cylinder extension calculation
2.2.1. Balance of forces at the cylinder
2.2.2. Spool lands ratio and pressure drops at the spool lands
2.2.3. Hydraulic cylinder extension. System pressure calculation
2.2.4. Flow through spool lands: max. and at current voltage
2.3. Hydraulic cylinder retraction calculation
2.4. Final words….

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Valve’s middle position configurations

Here are the practical advises to select the configuration of the middle position of 4-ways 3 positions directional valves. There are more than 250 configurations of the flow ways usually used in the practice, but in this quick review let see the generic configurations only.

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All ports are separated from each other:

mid_pos_01

Configuration notes:

  • This spool configuration is used where two or more operations are performed by a single pump or an accumulator. Pump output is available for other valves and actuators with this center condition.
  • Closed port P prevents the loss of fluid from the pump or accumulator when the spool crosses center. Avoid fixed displacement pumps for this configuration. More info about close circuits you can find here.
  • The spool-type valves are not zero-leaking devices. In actual use, leakage oil across the spool lands pressurizes A and B ports, possibly causing a single rod cylinder to extend trough piston/annular area difference. By the same reason this configuration is not for holding applications.

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