Actuator is a device that acts in accord with a control signal and performs a change of its state, for example the drive, which ensures movement or controlling of mechanism or system according to the control signal.
Actuators can be classified according to their physical principles:
With respect to the type of output variable, we can classify actuators into two categories. The first type can operate in two discrete states; for example:
The second type of actuator has output variable, which changes between two limiting states; for example: