Digital systems
Control

Control is a process, using a feedback to reach desired goal (feedback control). The goal of the control is to reach and ensure desired value of controlled (output) value (e.g. room temperature, tank level) or the desired time behavior (e.g. temperature behavior according to weekly plan or a temperature in chemical reactor according to specifications). The desired value must be assured not only after desired value change, but under disturbances, acting to a system, as well. The disturbances typically do have an unpredictable characteristic, e.g. thermal loss or increase in heated room (outdoor temperature change, window opening, draught, wall and room insolation, presence of persons or powered electric equipment).

Fig. 8.16: Control system setup