The proportional valve is also known as an electro-hydraulic proportional valve. It is a type of hydraulic valve that converts the input electrical signal into force or displacement in proportion, thereby enabling continuous control of parameters such as pressure and flow. The proportional valve consists of a DC proportional solenoid and a hydraulic valve. The hydraulic valve part is not significantly different from a general hydraulic valve, but the DC proportional solenoid and the electromagnets used in general solenoid valves are different. Using a proportional solenoid allows for displacement output and suction output proportional to the given current. Proportional valves can be classified into three major categories based on their control parameters: proportional pressure valves, proportional flow valves, and proportional direction valves.