An actuator that converts gas energy into mechanical energy to achieve reciprocating or rotary motion. Pneumatic actuators that realize linear reciprocating motion are called cylinders; those that realize rotary motion are called pneumatic motors. According to the control information from the controller, it is the element that completes the control effect on the controlled object. It converts electrical energy or fluid energy into mechanical energy or other forms of energy, and changes the mechanical motion state or other states (such as temperature, pressure, etc.) of the controlled object according to the control requirements. It acts directly on the controlled object and can play the role of "hand" and "foot".