A proportional-integral-derivative controller (PID controller or a three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control. To explore the application of PID controllers to the room temperature and humidity control system, an engineer can consider a single-zone cooling system as shown in the attached diagram of Air Conditioning PID. It is due to the fact that cooling and heating modes are found to perform nearly the same under most circumstances. The controlled plant measures 10m by 10m by 2.7m and is furnished with an air-handling unit consisting of the cooling coil and the humidifier to control room air temperature and humidity.
