Self-tuning control of an air-handling plant

The control system for the air-handling plant of a large building must be designed to cope with a wide range of operating conditions since the outside air temperature and humidity are subject to significant, periodic changes from day to night and from season to season. The presence of non-linearities in valves and actuators, and the variations in the gain and dynamics of heating and air-conditioning coils with the operating point make the control problem particularly challenging. Since the heating and cooling coils, the boiler and the water chiller are frequently designed to be as small as possible, to reduce the capital costs and restrict energy consumption, the plant may operate with its actuators very close to saturation for long periods of time. The controllers must be able to cope with considerable process non-linearities. The authors consider the use of self-tuning controllers in air handling systems, two methods are compared