Looks at the development of a tuning method for use with the PI controllers that are being used to control first-order heating, ventilating, and air conditioning (HVAC) processes. The tuning method is developed in two stages, the first stage applies to fast-acting actuators, while the second stage is specific to the electric actuators found in many HVAC systems. The tuning method is derived from control theory using pole-zero cancellation and root locus techniques. To accommodate constant-velocity actuators, such as gear-motors, the method is empirically modified from simulation data. The tuning method was tested experimentally on a humidification control system. Experiments showed that the tuning method was capable of producing smooth, quick, critically damped responses with a time-delayed, first-order process that included a constant-velocity actuator.

KEYWORDS: controls, building services, heating, ventilation, air conditioning, motors, programmable controllers