Actuator
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In control engineering actors (often also called actuators) denote the converter-related counterparts to sensors and form the control element in a control loop.
They convert signals of a closed-loop control into (mostly) mechanical work, i.e. movements to open or close valves, for example. In practice actuators are also found in the form of (electric) motors, hydraulic or pneumatic cylinders, piezo actuators (translators), ultrasonic motors, electrochemical actuators. Electromechanical lifting and adjustment systems are used in linear technology.
The write/read head (stepper motor) of a hard disk or the compensating weight in a stationary pendulum is also designated as an actuator. The positioning control is carried out in an open or closed control circuit as a rule. Actuator materials with smart character originate from the field of new materials. Through integrated actuator sensor functions they can react to modifications of specific ambient parameters with defined actuator effects and, therefore, replace expensive controlled systems with a single element. Actuators on the basis of shape memory alloys and expansion elements are temperature sensitive and are used in thermostats, for example. Smart hydrogels are also used for valves that automatically regulate the pH value, ion or substance concentrations.
