This example shows an amplifier that consists of two fixed orifices, two variable orifices representing nozzles, flapper, and main valve simulated with mass, viscous friction, and centering spring. Two translational converters represent servo-actuators on both sides of the main valve. A feedback spring connects the flapper and the main valve.
The amplifier is actuated with a force source, which represents the force generated by an electromagnet. The flapper displacement causes pressure difference between converter chambers, which moves the spool. The main valve acts on the flapper in the opposite direction via a feedback spring. The amplifier comes to a steady-state position as the force equilibrium on the flapper is reached.
The plots below show the pressures acting on the spool and the position of the spool.