Internal Model Control Based On Variable Domain Fuzzy Control For Time-Delay Systems

The control for processes with time-delay is always encountered in industry. Aim at this problem, this paper presents a filter time constant A self-adjusting internal model control (IMC) based on variable domain fuzzy control. A modified variable domain fuzzy control method is proposed on the basis of quantitative factor and the nature of power function contraction-expansion factor has been researched.Mainly from the following aspects the research work was carried out:1. Based on the principle of internal model control (IMC), the IMC design method was be introduced to Smith predictive control. Firstly, the filter time constant on-line self-tuning method was proposed; then, the filter time constant fuzzy rules was established according to fuzzy control theory. The closed-loop characteristics can be improved by adjusting the filter time online.2. The domain contracting (expanding) of input and output will affect the control performance. Therefore, the paper has researched on this aspect, and how to improve the performance by using it has also been studied. According to the research, the paper proposed a modified variable domain fuzzy control based on quantitative factors. Then the analysis about the relationship between control parameter (quantifiable factor) and the contraction-expansion factor was presented.3. The paper has studied the mathematical and engineering characteristics of the general contraction-expansion factor. Based on the study and variable domain fuzzy control theory, the power function contraction-expansion factor is derived. 4. For illustration, aiming at first-order and second-order time-delay processes, the simulation experiments are taken respectively, when model is accurate and inaccurate or uncertain process and disturbance exits by using different contraction-expansion factors.The simulations show that, the method proposed has better performance than the traditional fuzzy control. Not only the problems of high accuracy request for model in Smith controller,model mismatch and uncertain model have been solved, but also can obtain the better compromise control effect between and system response and robustness. Furthermore, according to the modified method, only one fuzzy control rules look-up table needs to be established in application; and the power function contraction-expansion factors are available for hardware implementation both of which are available for slow-response chemical system and rapid-response mechanical system.