Pressure compensated hydraulic system having differential pressure control

A method of controlling a hydraulic system wherein plural control valves each have a variable metering orifice through which hydraulic fluid flows between an inlet port providing for connection to a pump and a respective work port providing for connection to a respective actuator, comprising the steps of:

• using a compensator to control flow of fluid from the variable metering orifice to the work port of each control valve in response to a differential in pressures acting on opposite first and second sides of the compensator, wherein the first side receives a pressure at the downstream side of the variable metering orifice;
• providing a load sense pressure corresponding to the greatest pressure amongst the work ports;
• and
• using a differential pressure controller having a first inlet connected to the pump supply port and a second inlet connected to the load sense passage, the differential pressure controller having a first operational mode in which load sense pressure at the second inlet is supplied to an outlet of the differential pressure controller and a second operational mode in which flow from the first inlet is metered to the outlet of the differential pressure controller to provide a differential control output pressure at the outlet of the differential pressure controller, and
• wherein the outlet of the differential pressure controller is connected to (a) a pump control port to which can be connected the control port of a variable displacement pump that produces an output pressure of the pump that is a predefined amount greater than the pressure supplied to the control port of the pump, and/or (b) the second side of the pressure compensating valve of at least one of the plural control valves.

A valve assembly comprising:

• multiple working sections, each working section having a movable control spool and a compensator downstream of an inlet of the control spool,
• an input conduit for supplying fluid to the working sections,
• a load sense conduit adapted to receive a pressure signal from the working section outputting a highest pressure, and
• a control mechanism connected to the input conduit and the load sense conduit and provide an output pressure in response to a fixed setting or variable input actuation of an associated input.