Digital control of unstable and integrating Time-delay processes

Abstract

Time-delay (dead time) is very often encountered in various technical systems, such as electric, pneumatic and hydraulic networks, chemical processes, long transmission lines, robotics, etc. Time-delays are mainly caused by the time required to transport mass, energy or information, but they can also be caused by processing time or accumulation. A part of time-delay systems can be unstable or have integrating properties. Typical examples of such processes are e.g. pumps, liquid storing tanks, distillation columns or some types of chemical reactors. This paper deals with a design of algorithms for digital control of the unstable and integrating time-delay processes using one suitable modification of the Smith Predictor (SP). This digital modification of the Smith Predictor is based on Linear Quadratic (LQ) method. A minimization of the quadratic criterion is realized using spectral factorization. The designed algorithms have universal usage; they are suitable for control of stable, non-minimum phase, unstable and integrating time-delay processes. The main contribution of this paper is design and simulation verification of this Smith Predictor for control of the unstable and integrating processes, because classical continuous-time Smith Predictors are not suitable for control of such processes. The designed algorithms for control of individual processes influenced by external disturbance were verified. The program system MATLAB/SIMULINK was used for simulation verification of designed algorithms. © 2014 North Atlantic University Union. All rights reserved.