What is the structure principle of electric proportional valve?

The structural principle of the electric proportional valve is:

When the input signal increases, the air supply solenoid valve pilot valve 1 is reversed, and the exhaust solenoid pilot valve 7 is in the reset state, then the supply air pressure enters the pilot chamber 5 from the SUP port through the valve 1, the pilot chamber pressure rises, and the air pressure Acting on the top of the diaphragm 2, the air supply valve core 4 connected to the diaphragm 2 is opened, and the exhaust valve core 3 is closed to generate output pressure. This output pressure is fed back to the control loop 8 via the pressure sensor 6 . Here, a quick comparison and correction with the target value is performed until the output pressure is proportional to the input signal, so as to obtain a change proportional to the change of the output pressure and the input signal. Since there is no nozzle baffle mechanism, the valve is insensitive to impurities and has high reliability.