Design of an optimised dual fuzzy logic speed controller for high performance electric drives

The paper describes a novel method for the design of an optimised fuzzy log ic speed controller. The approach is based on the analysis of the system be haviour in the error state-space. The final control structure, in a form of a dual fuzzy logic controller, is arrived at in two stages. The first stag e encompasses design of a PID-like fuzzy controller, while the second stage consists of placing an additional fuzzy controller in parallel with the PI D-like fuzzy controller. The resulting dual controller is characterised wit h high performance in the wide range of operating conditions, and with smal l number of parameters that can be adjusted using optimisation methods. Tun ing can be performed either independently for the PID-like fuzzy controller and the additional fuzzy controller (using a simple Nelder-Mead optimisati on method), or simultaneously (using genetic algorithms). Both possibilitie s are discussed and the results are compared. The controller is developed a nd tested for a plant comprising a vector controlled induction motor drive.