Discrete-time advanced PID control systems for unknown time delay systems and their applications

PID control schemes have been used widely in most process control systems represented by chemical processes for a long time. Indeed, they are easy for most engineers in many industries to understand and for the use of various systems, whose properties are obscure. However, conventional PID control schemes have not been so available for the systems whose system parameters and time delays are unknown. The purpose of this paper is to consider advanced PID control schemes in discrete-time systems with unknown time delays. Two control schemes, that is, compound PID control systems with a local feedback compensator and a pre-compensator are proposed, and they are extended to explicit-type self-tuning PID control schemes. Furthermore, these methods are applied to a pressure-control system to show their effectiveness. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (3): 50–57, 1997