Glossary · Automation fundamentals, platforms and components
Actuator
Also known as: Final control element
German: Stellglied
In industrial automation, an actuator is a device that converts a control signal into a physical action, such as motion, force, a valve position or heat input. Motors, pneumatic cylinders, control valves and heaters are typical actuators.
- Automation components
In one sentence
An actuator converts a control signal into a physical action such as motion, force or a valve position, for example a motor, cylinder or valve.
Example
A PLC output energizes a solenoid valve, and the pneumatic cylinder behind it pushes a carton off the conveyor.
How it applies
- Engineering: Actuators are sized for the required force, speed and duty cycle and selected for the environment (temperature, IP code (degree of protection), explosion protection). The control loop sends the Manipulated variable to the actuator.
- Commissioning: Direction of motion, end positions and fail positions (open, closed, last position) are checked against the design before automatic operation.
- Maintenance: Actuators contain moving parts and often Stored energy in springs, air or hydraulics, so isolation steps matter.
- Documentation: Describe each actuator's function, fail position and energy sources, and make sure lockout instructions cover every energy the actuator can hold.
Actuator vs. sensor
A Sensor measures a physical quantity and reports it to the controller; an actuator acts on the process. Together with the controller they close the loop: sensor, controller, actuator, process. In German the list term "Stellglied" is often translated as "final control element" in process control.