Linearizing PID Loop Control PDF

Although many articles have discussed proper control valve and damper selection for linear response, the attention has focused on selecting control components to reduce the inherent nonlinear behavior rather than using direct digital controls (DDC) for linearizing the behavior. This article addresses a method for achieving predictable linear response for supply duct pressure control, economizer damper control and steam heat exchanger leaving water temperature control using PID (proportional plus integral plus derivative) control loops. Using this technique normalizes PID loops, which prevents the need for tuning many common HVAC PID loops.