On performance and tuning of PID controllers in HVAC systems

This paper describes the effects of disturbances and process time delays on control performance. Their relationships to HVAC control systems are discussed. The relationships between tuning rules based on open-loop parameters and those based on ultimate parameters are then studied. It reveals that the Ziegler-Nichols rules based on ultimate parameters are more conservative than those based on open-loop parameters. The modified relationships between the normalised time delay and the ultimate parameters can be used as a guideline for further adjustment of the control parameters.<
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