First the most important definitions regarding control processes should be given. They are defined by the German Industry Standard DIN 19226.
: One or several input parameters influence one or several output parameters in a system, based on regularities which are relevant to the system and are either measured or predefined.
: The parameters being controlled are constantly measured. The result is compared with the reference variables and then the parameters are adjusted correspondingly.
Each control loop contains at least one series connection of controller (governor) and control path. In a control loop, a distinction has to be made between command response and disturbance response.
is the reaction of the controlled parameter in the control loop to a
change in the command (target) value
is characterized by the reaction of the controlled parameter to a
change in the disturbance variable