The classical proportional-derivative (PD) control is relatively easy to design, but useful for fast response controllers by combining proportional control and derivative control in parallel. However, as PD control is linear, it is not able to be used to deal with non-linear plants. An answer to this problem is fuzzy-logic control, which is also a model-free control scheme and can be applied to systems where mathematical models cannot be obtained. Besides, natural heuristic rules in linguistic expressions that reflect human experiences can be applied in the control design, minimizing the design cost. Fuzzy-logic controllers (FLCs) are the control systems based on a knowledge consisting of the so-called fuzzy IF-THEN rules.