A Temperature Controller for VAV Air-Handling Units Based on Simplified Physical Models

Abstract

A feedforward controller based on simplified physical models is described for air-handling units to supplement conventional PI control. Inverse static models of the controlled processes produce feedforward control action and the PI feedback loop compensates for modeling errors and unmeasured disturbances. The models are configurable from plant design information and they operate using the sensor signals typically available to an air-handling unit controller. The incorporation of feedforward 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 and models, and presents results from tests carried out using a simulated air-handling unit.

Multiplexed optimization for complex air conditioning systems

“…As defined by Eqn. (11), the tracking errors are calculated as the integrated absolute values of the temperature deviations between the setpoints and the actual measurements. It should be noted that the stabilities are compared under the same control settings.…”

“…When the set-points for both the chilled water temperature and the supply air temperature are changed simultaneously, a significant disturbance might be added to the control loop of the supply air temperature, where a PI control is generally adopted [10]. If the control parameters of the controller are not well tuned (always true in practice), a large variation or even oscillations may occur in the supply air temperature [10,11].…”

Multiple fuzzy model-based temperature predictive control for HVAC systems

“…Recently, some complex control strategies based on the classical control concepts have been proposed in attempts to improve the system performance. Among those works, Salsbury [3] described a feedforward control scheme based on a simplified physical model as a supplement of the conventional PI feedback control. Kasahara et al [4] proposed a robust PID control scheme to deal with the model uncertainty caused by changing characteristics of the plant.…”

Estimating airflow rates in air-handling units from actuator control signals

“…Many monitoring and control schemes proposed for use in air conditioning systems assume that measurements of the airflow rates are available; for example, ventilation control schemes [1][2][3][4], supply air temperature control schemes [5,6], return fan control schemes [7,8] and fault detection and diagnosis schemes for airhandling units [9][10][11]. However, airflow rates are often not measured in practice.…”