The application of self-tuning PID control to HVAC systems

Various approaches to the design of self-tuners for application in HVAC systems have been proposed. Designs fall into two main categories: model-based algorithms in which the parameters of the PID controller are related to the parameters of a transfer-function model of the plant, the parameters of the model being determined in open or closed loop from step tests or estimated using a recursive parameter estimator; and empirical rule-based algorithms in which the parameters of the PID controller are determined by a set of heuristic rules. Examples of each are examined, and it is shown that good design and implementation of the supervisor is essential if self-tuning controllers are to be applied successfully to HVAC systems. The selection of suitable control loops should take account of what prior knowledge is available, and plant must be designed and commissioned properly if the advantages of self-tuning control are to be realised in practice