PI tuning and robustness analysis for air handler discharge air temperature control

The paper presents a PI tuning strategy for air handler discharge air temperature control in building comfort application. It recommends using a 5 min settling time with no overshoot as the design criterion to select PI gain values, and recommends that a PI controller should be retuned when the settling time is larger than 20 min. This tuning strategy avoids unnecessary tuning while providing acceptable control performance for building comfort control. The paper further concludes that PI tuning can be done by adjusting proportional gain only and keeping the reset time constant for air handler discharge air temperature control. The proportional gain can be calculated based on the system sum of time constant and delay, and system static gain in typical applications. Inclusion of the time constant in the equation is recommended for uncommon applications where the delay is large. Regression equations are given based on simulation results for both typical applications and uncommon applications. The PI tuning strategy proposed in the paper can be reliably used in PI auto tuning since it uses less model information and adjusts less gain values than existing tuning algorithms.

► The paper presents a PI tuning strategy for AHU discharge air temperature control.
► 5 min settling time with no overshoot is used as the design criterion.
► PI tuning adjusts proportional gain only and keeps the reset time constant.
► The tuning equations include sum of time constant and delay and static gain.
► The tuning equations are given based on regression of simulation results.