The desagn facalatzes of fuzzy controllers are completed by partacular regaons an the plane of controller parameters. In these regaons, predetermaned sensztavzty lamats of control system performance are guaranteed. Intended for complex plants wath uncertazn parameters, the results are the basas for suatable fuzzy-controller adjustment. The regaons for predetermaned performance sensztavzty are obtarned by computer-based samulataon. I n order to reduce the danger of skappang enclaves of anstabalaty, movang and decreasang ancrements an the searchang parameter are taken anto consaderataon.