HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Artificial Intelligence, Fuzzy Logic and ControlFigure 6-10. Feedback with inverse, model and adjustment functionsTransfer function models use an open-loop Laplace transform descriptionof the process response to a step input. This is a common controlmodeling approach but is limited to linear and simplistic dynamicmodeling.Time series models involve the open-loop response of the processto a vector of impulses. These are empirically determined and consist ofabout 30 elements. More precision is possible but matrix/vector algebrais required. This is the most common modeling approach used formodel-based control.Nonlinear phenomenological models are design-based simulatorsfor nonlinear or nonstationary processes. Their control intelligencecomes with modeling and computational complexity.Internal Mode ControlThis is a type of modeling that uses open-loop, step-responseLaplace transfer functions. The basic structure is shown in Figure 6-11. Asimple first-order-plus-dead-time representation is shown in Figure 6-12.©2001 by The Fairmont Press, Inc. All rights reserved.