1.2 Control engineering terminology
The terms of control engineering are described here using the example of a level control.
The control loop consists of:
controlled systems are any system, installation or equipment whose behaviour is to be managed by closed loop control.
In this example, the tank (1).
Measuring elements are all kinds of sensors that detect the process values in the control loop. In this example, a level sensor (2).
The controller (3) is the component that performs the actual control. It triggers actuators to carry out actions.
Actuators are components that influence the process on behalf of the controller. In this example, a control valve with drive (4) at the tank inlet.
The control system consists of the controller and the comparing element. If necessary, the measuring element and actuator can also be counted as part of the control system.
Level control components:
2 level sensor
4 control valve
Elements and measured variables in control loop as block diagram
Measured variables in the control loop are:
controlled variable x
In this example, the actual level in the tank (feedback value).
reference variable w
In this example, the desired level (setpoint).
manipulating variable y / controller output variable y
In this case, the inflow into the tank or the control signal output by the controller to the actuator.
disturbance variable z
In this example, the drainage from the tank.
actuating variable / control difference e
Variation of the controlled variable x (feedback value) from the desired reference variable w (setpoint).
This video introduces you to another example to discover the components of a feedback control system and how they interact with each other.