In the flight control system of F/A-18, where is the servo-loop closed? I mean which of these two scenarios happen: 1-The position of the actuator and servo-valve ram are sent to the flight control computer and the servo-loop is closed there in the software, 2-the servo-loop is closed near actuator that means the actuator has an interface that receives a command and compares it with the actual position. If the second scenario is what happens, the interface is digital or analog?
Ram position feedback is sent back to the relevant channel in one of the two flight control computers via wire carrying an analogue signal. If it is a leading edge flap, aileron or rudder it is done twice. The big surfaces (Trailing Edge Flap and Horizontal Stab) are quad redundant. The signal is processed on a printed circuit board inside the box. There is negative feedback occurring via an operational amplifier type circuit.