implementation of autotuning in interacting tanks to emulate a bioreactor

Abstract

The set of two interacting tanks in the Chemical Engineering Lab is a prototype process that can be used to test novel and interesting control schemes. For this project a process that can be represented as a form of an either first order plus dead time (FOPDT) or a second order plus dead time (SOPDT) is tuned using a self-tuning algorithm, with Deadtime added to the control scheme to allow the simulation of a bioreactor. The algorithm uses an intelligent form of a PID controller that determines the tuning settings; thereby eliminating the need for the manually setting of the classical PID controller settings. Because there are a myriad of tuning algorithms, we followed the suggestion of Luyben (1) to provide 3 user selectable tuning settings that the user could choose from “on the fly”. These PI settings are calculated using three distinct methods; Ziegler Nichols (ZN), Tyreus Luyben (TL) and IMC methods. The auto-tuning algorithm and deadtime loop were designed, and the PLC and relay feedback tests were conducted to validate that the set up worked properly. An auto-tuning relay feedback algorithm implemented and system parameters values calculated. The algorithm was successfully able to maintain control during upsets.