Multiple-model Based Intelligent Control Techniques for Lti Systems with Unknown External Delays Part I: Known Rational Component

In this two-set paper, an intelligent control framework which allows maintaining a conceptually simple control design methodology while simultaneously explicitly dealing with uncertainty in both rational component of the plant and delay is presented. This first part is devoted to the Smith Predictor (SP) based control of systems with known rational component and uncertain delay. Thus, as the mismatch between the actual delay of the plant and the nominal one used in the control structure increases, the closed-loop performance degrades accordingly, even potentially causing instability. In this paper, an intelligent frame to reduce the ‘a priori’ knowledge of the plant delay required in the design of SP controllers is proposed. The intelligent frame is composed of a set of different plant delay models running in parallel along with a high level supervision algorithm which selects the one that best describes the actual delay of the plant at each time interval to be used for control purposes. In this way, the designer can design the control of the system based on its delay-free part while the appropriate tuning of the delay of the Smith Predictor is performed by the intelligent supervisor. As a consequence, like simulation examples show, the closed-loop performance of the system is improved without the ‘a priori’ requirement of an accurate knowledge of the value for the time delay.