(57) A hydraulic control system is disclosed comprising two actuators operating in parallel
or tandem each having a separate supply of hydraulic fluid and two electrohydraulic
servo control valves interposed between each actuator and its respective hydraulic
supply, each control valve having two operating coils for the electrical operation
thereof, the said coils being connected to four electrical control lanes in such a
manner that each lane is connected to one coil of a control valve asociated with one
actuator and with one coil of a control valve associated with the other actuator.
Feedback control of the valves is preferably provided to equalise hydraulic imbalance,
the valves for each actuator having differing overlap characteristics such that the
feedback signal may apply selectively to the valves of one or other actuator.
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