Definition of proportional valve hysteresis

The hysteresis is an important static indicator of the proportional valve, which is defined as the 

percentage of the instruction difference between the widest points of the two "flow vs instruction

 curves" of instructions 0-100% and 100%-0

The existence of hysteresis will reduce the repeatability of open loop control system.

For the closed-loop control system, the proportional valve hysteresis is too large,

resulting in system vibration and closed-loop control failure.

The source and circumvention of hysteresis

The hysteresis mainly comes from the friction force between the spool and

the valve body and the static hydraulic force. For the direct drive valve driven

by proportional electromagnet, the hysteresis and friction hysteresis of proportional

electromagnet are also important sources of proportional valve hysteresis.