According to the different control media used by the actuator, it can be divided into three types: pneumatic, electric and hydraulic actuators. According to the form of output displacement, there are two types of actuators: corner type and linear type. According to the law of action, the actuator can be divided into three types: switch type, integral type and proportional type. According to the input control model, the actuator can be divided into several categories, such as air pressure signal, DC current signal, electrical contact on-off signal, pulse signal, etc.