A robust self-tuning PID-type control for time-varying process in the pharmaceutical industry

Abstract

In this work, we present a comparison between three PID-type controllers designed via different methods for a process with time-varying properties. Such a process is commonly encountered in the process industry, with prevalence in the chemical, food and pharmaceutical manufacturing industries. The controllers are varying in complexity from operator level (rule-based) to expert tuning (computer-aided design) and beyond state of art (generalized fractional-order control). Experimental tests indicate the feasibility of the controllers for variations in time constant with varying operation conditions originating from physical changes in the process. This is rather a common problem in practice and highly relevant for control engineering. Furthermore, an analysis of the system properties reveals the opportunity to operate in closed loop in a self-tuning manner, which avoids the necessity to re-design the controller parameter values.