A combination open-loop and feedback control of mercury flow was used with this valve. Figure 2 shows a block diagram of the control. The open -loop path provided the main control, while the feedback loop served merely as a trimming control to eliminate any error. ... In a flight system, the mercury flow control valve would be actuated by an electric motor with only open-loop (programmed) control .
|Author||:||United States. National Aeronautics and Space Administration|