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A revolution in mobile hydraulic equipment is occurring. Conventional hydraulic spool valves with hydromechanical pressure compensators are being replaced by valve assemblies with four valve independent metering with electronically-controlled pressure compensation. In the system described here, two of the four independent valves are active during metering. This new topology offers significant advantages due to the two degrees of freedom provided. One of these degrees of freedom used to control velocity is more fully described in a related paper. In this paper, it is shown how the second degree of freedom can be used to control pressure in an actuator workport or minimize velocity errors due to valve coefficient errors. Workport pressure control can be used to limit maximum or minimum workport pressures (e.g. prevent cavitation). Given certain criteria, an optimal solution can be obtained.

A revolution in mobile hydraulic equipment is occurring. Conventional hydraulic spool valves with hydromechanical pressure compensators are being replaced by valve assemblies with four valve independent metering with electronically-controlled pressure compensation. In the system described here, two of the four independent valves are active during metering. This new topology offers significant advantages due to the two degrees of freedom provided. In this paper, the theory behind a new method of flow control based upon load feedback is presented for two of the five distinct metering modes. In addition, a new algorithm for setting the supply pressure is presented which is also based upon load feedback.