Experts explain the basic control strategy of crane multi way valve
Two basic control strategies of multi spool valve. Because of the flexibility of the two oil port control, the two oil port can be controlled by flow control, pressure control or flow pressure respectively. Two simple control strategies are introduced.
(1) the direction of the multi way valve in the entire work process to maintain the same
We know that for truck cranes, excavators, loaders, etc., its hydraulic cylinders in the entire work process load direction always remain unchanged. The control strategy of the double valve core is discussed with the example of the hydraulic cylinder of the crane.
In the working process of the crane, the load direction remains the same, so we can adopt the control strategy of the hydraulic cylinder rod control and the flow control of the rod cavity.
Rodless cavity flow control is by detecting the connected to the non rod chamber side of the valve before and after both sides of the differential pressure, according to the required flow into or out of, the calculated valve opening size; rod side chamber with pressure control, so that the side of to maintain a low pressure, the more energy efficient.
Because we use the flow control in the cavity, so the original control system used in the balance valve can be used to replace a liquid control one-way valve. This can eliminate the system caused by the balance valve is not stable, so as to improve the stability of the system.
(2) the change of the load direction of the multi way valve in the working process
In this case, to take the oil side pressure control, the oil side flow control, in the hydraulic cylinder rod chamber side with the pressure control, no rod cavity side of the flow control. If the load is constant, we can use the hydraulic control check valve to replace the hydraulic control check valve, which can improve the stability of the system. Into the oil side with a pressure controller to maintain a lower reference pressure, on the one hand, improve the efficiency of the system, on the other hand makes the system cavitation does not occur.
Multi way reversing valve in order to make the load changes in the direction of working mechanism can get good control, another PI controller will be applied to the rod chamber of the pressure controller, when the load direction changes, no rod chamber of the pressure will decrease; if still rod chamber to maintain a very low pressure, when the load is large, hydraulic cylinder will to move in the opposite direction. At this time we can use to monitor the increase in PI controller without the rod chamber pressure changes, when the PI controller detects that the rod chamber pressure is lower than the set reference value, multi valve will improve the rod chamber pressure controller set pressure, thus ensuring the system work properly.