A TEMPERATURE CONTROLLER FOR VAV AIR-HANDLING UNITS BASED ON SIMPLIFIED PHYSICAL MODELS

A feedforward controller based on simplified physical models is descri bed for air-handling units to supplement conventional PI control. Inve rse static models of the controlled processes produce feedforward cont rol action and the PI feedback loop compensates for modeling errors an d unmeasured disturbances. The models are configurable from plant desi gn information and they operate using the sensor signals typically ava ilable to an air-handling unit controller. The incorporation of feedfo rward control reduces the reliance on the feedback loop and makes the tuning of the PI controller less critical. Low gain (default) control parameters may then be used in the feedback loop, thereby eliminating the need for on-site tuning. This paper describes the control scheme a nd models, and presents results from tests carried out using a simulat ed air-handling unit.