The paper proposes a development method for PI-fuzzy controllers of Mamdani-type and of Takagi-Sugeno-type meant for two classes of second-order systems. The controllers are developed by starting from basic PI controllers tuned in terms of the Extended Symmetrical Optimum method, followed by applying the modal equivalences principle resulting in useful development steps. The developed fuzzy controllers belong to the class of low cost automation solutions. The controllers and development method are validated by two case studies and digital simulation results that can correspond to the speed control of an electrical drive.