Microcontroller based self-tuning digital PID controller

Abstract

Paper deals with implementation of self-tuning digital PID controller on general-purpose 8-bit Freescale 68HC908GB60 microcontroller which is a part of development board M68EVB908GB60 by Axiom Manufacturing. The process is identified using modified recursive least squares method with adaptive directional forgetting resulting in δ model representation of controlled plant. This representation was chosen in order to achieve lower sampling time periods and mainly better numerical stability of identification process. Control part of algorithm utilizes digital PID controller whose parameters are designed by pole placement method. Developed program equipment works under realtime operating system RTMON for HCS08 which was created on our department. Functionality of the controller was verified by controlling two different educational heat plants models which are used in laboratory lessons of Theory of Automatic Control subject.