The Gravity Drained Tanks Process
ABSTRACT: This case study considers the control of liquid level in a gravity drained tanks process. Like the heat exchanger, the gravity drained tanks displays a typical self regulating process behavior. That is, the measured process variable (PV) naturally seeks a steady operating level if the controller output (CO) and major disturbances are held constant for a sufficient length of time.
Dynamic "Bump" Testing of the Gravity Drained Tanks Process
ABSTRACT: We introduced the gravity drained tanks process in a previous article and established that it displays a self regulating behavior. We also learned that it exhibits a nonlinear behavior, though to a lesser degree than that of the heat exchanger. Our control objective is to maintain liquid level in the lower tank at set point in spite of unplanned and unmeasured disturbances. The controller will achieve this by manipulating the inlet flow rate into the upper tank.
Graphical Modeling of Gravity Drained Tanks Step Test
ABSTRACT: We have explored the manual mode (open loop) operation and behavior of the gravity drained tanks process and have worked through the first two steps of the controller design and tuning recipe. Here we present step 3 of our recipe and focus on a graphical analysis of the step test data. Next we will explore modeling of the doublet test data using software.
Modeling Gravity Drained Tanks Data Using Software
ABSTRACT: We have investigated a graphical analysis method for fitting a first order plus dead time (FOPDT) dynamic model to step test data for both the heat exchanger and the gravity drained tanks processes in previous articles. Describing process behavior with an approximating FOPDT dynamic model is the third step of our controller design and tuning recipe. Thus, it is a critical step for quickly achieving desired controller performance while avoiding time consuming and expensive trial and error methods.