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The system is called reverse acting if it is necessary to apply negative corrective action. For instance, if the valve in the flow loop was 100–0% valve opening for 0–100% control output – meaning that the controller action has to be reversed. Some process control schemes and final control elements require this reverse action.
Direct digital control is the automated control of a condition or process by a digital device (computer). [ 1 ] [ 2 ] Direct digital control takes a centralized network-oriented approach. All instrumentation is gathered by various analog and digital converters which use the network to transport these signals to the central controller.
A control system includes control surfaces which, when deflected, generate a moment (or couple from ailerons) about the cg which rotates the aircraft in pitch, roll, and yaw. For example, a pitching moment comes from a force applied at a distance forward or aft of the cg, causing the aircraft to pitch up or down.
In the 2000s, direct-acting electronic parking brakes controlled by a switch (as in the Volkswagen eGolf [3]) are becoming more common, replacing cable-actuated mechanical systems. In rallying there is often a hydraulic handbrake for the rear wheels, operated by a long, vertical lever extending to near the steering wheel.
Control reversal is an adverse effect on the controllability of aircraft.The flight controls reverse themselves in a way that is not intuitive, so pilots may not be aware of the situation; to roll to the left, they have to push the control stick to the right, the opposite of the normal direction.
A motor-driven cam (usually relatively slow-speed) and one or more micro switches form a timer mechanism. The snap-switch mechanism can be enclosed in a metal housing including actuating levers, plungers, or rollers, forming a limit switch useful for control of machine tools or electrically-driven machinery.
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The flight control system on the 777 is designed to restrict control authority beyond certain range by increasing the back pressure once the desired limit is reached. This is done via electronically controlled backdrive actuators (controlled by ACE). The protections and augmentations are: bank angle protection, turn compensation, stall ...