Two basic control strategies of double valve core multiple reversing control valves. Due to the flexibility of the multiple reversing control valves, double reversing valve core two oil mouth control , two oil mouths can respectively take the flow control, pressure control or flow control. Now we will introduce two kinds of simple control strategy.
(1)The load direction of the multiple directional control valves remains the same in the whole working process
As we all know, for truck crane, excavator, loader, etc, the load direction of the hydraulic cylinder in the process of the whole work always remains unchanged. The following will discuss the double control strategy of valve core of the crane luffing hydraulic cylinder as an example.
The load direction of the crane luffing cylinder in the working process always remains the same, so we can adopt the strategy of the hydraulic cylinder rod control with pressure control and the rodless cavity with flow control.
The rodless cavity flow control, through measurement and connection to the rodless cavity side valve on both sides of the differential pressure, then according to the required inlet and outlet flow to calculate the valve core opening size; The rod cavity side uses pressure control, making the side to maintain at a low pressure and more energy saving and efficient.
Since we have adopted the flow control in the rodless cavity, therefore, the original balance valve used in control system can be replaced with a hydraulic controlled check valve. It can eliminate the unstability from the balance valve so as to improve the system stability.
(2) The load direction pf the multiple directional control valve in the working process changes. In this case, take "the inlet oil side pressure control, outlet oil side flow control".In the hydraulic cylinder rod cavity side pressure control, rodless cavity side have flow control. Such as load direction remains the same, because the oil side adopted flow control, we can use the bidirectional balance valve hydraulic control one-way valve to replace, so as to improve the stability of the system. Suction side pressure controller to maintain a low pressure of reference, on one hand, it can improve the efficiency of system, on the other hand, the system will not occur air-pocket.
Multiple directional control valves in order to make the direction of the load change job agencies can be well-controlled, another PI controller will be used to sucker rod cavity pressure controller, when the direction of the load changes, the rodless cavity pressure will be decreased; If you still will have the rod chamber to maintain a low pressure, when the load is very big, the hydraulic cylinder will move to the reverse direction. At this point, we can increase the PI controller monitors the change of the rodless cavity pressure, when PI controller detected rodless cavity pressure is lower than the reference set, multiple directional control valves will improve the rod chamber pressure controller set pressure, so as to guarantee the normal work of the system.
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