Application of improved fuzzy-tuned and fuzzy controllers in variable-speed drives

In the first part of the paper a novel improved fuzzy-tuned PI controller (IFPIC) is developed, which is based on the combination of the principles of conventional PI control and fuzzy logic. The IPFIC resembles a traditional type of PI controller, whose parameters are, however, tuned by using a fuzzy parameter self-tuning mechanism. This leads to an improved performance of the transient and steady-state behaviour of the closed-loop system, which involves a variable-speed DC drive. In the second part of the paper the results of a comprehensive series of digital simulations are presented for a fuzzy-controlled DC machine. It is shown that the performance of the IPFIC is superior to that of optimised PI controllers. The influence of the rule base is investigated and the effects of parameter uncertainty are also discussed. In the last part of the paper three interacting fuzzy controllers are applied in a variable-speed DC drive. It is believed that this is the first paper which gives the results of the application of three interacting fuzzy controllers. It is shown that the results are also in good agreement with those obtained by the application of other types of self-tuning controllers.