Actuator
An actuator is a part of certain actuators that are used for automatic control and regulation .
The electrically (with motors , see also electromotive drives for pipeline fittings ), pneumatically or hydraulically driven actuators are, for example, valves , cocks or slides that change the mass flow in technical systems .
species
A general distinction can be made between actuators:
- according to the type of auxiliary energy used (pneumatic, hydraulic, electric, electromagnetic, manual or a mixed form),
- according to the type of actuator to be driven (pipe fitting, machine part, heating valve, etc.),
- according to the construction principle (piston, membrane, motor, magnetic coil, handwheel or hand lever, etc.),
- according to the type of positioning movement (straight, pivoting (90 ° or 60 °) or rotating).
According to DIN 19226, the term actuator is divided into the two sub-terms of control drives and regulating drives.
Control drives
Control drives, which work as the last link in a control chain, are mainly used to open / close actuators.
Variable speed drives
The task of regulating drives, on the other hand, is to be integrated in control loops and, in the event of malfunctions in the controlled system, to transmit the control commands from the controller to an actuator so that the control deviation remains as small as possible. A distinction is also made here between controls in 3-point operation (open-stop-close) and continuous controls with a constant control signal.
Definition of terms
The actuators for pipe fittings are of particular importance. Therefore, the term actuator is often used as a synonym for valve drive . These are also available in a similar form for other pipe fittings (flaps, gate valves, etc.). The term actuator, however, as a generic term, refers to all actuators.
In many cases an additional positioner is assigned to the actuator . This positioner then has the current position of the actuator as a feedback. This achieves better control quality and standardizes the control-related task.
In some areas, when the task is basically the same, one speaks of a servo instead of an actuator , mostly driven by a servomotor .
literature
- Joachim Gräfer: " Actuators for automation technology ", in industrial valves, 4th year September 1996