Redundant ehv fault detector

Abstract From the Canadian patent

Plural servo actuators are coupled to provide a redundant system for operating a common output device. Each servo actuator has plural servo valves each having one active output that causes controlled opposite operation of the output device and one passive output. A fault detector coupled to each servo actuator compares the sum of the passive output pressures with the pressures of two other fluid signals in one, case the supply and return fluid signals and in another case the two active output signals of the servo valves, to detect the condition thereof. A convenient checkout system and a fluid by-pass mechanism also are provided in the fault detector.