1. An autotuning method using an integral of a relay feedback response wherein the autotuning method is implemented by a proportional integral derivative controller, the method comprising the steps of: integrating a process data to significantly remove the effects of harmonics wherein the proportional integral derivative controller integrates the process data; and computing an ultimate gain wherein the proportional integral derivative controller computes the ultimate gain by K c ⁢ ⁢ u = 2 ⁢ hp π 2 ⁢ b wherein b is an amplitude of a y b ({tilde over (t)})−y bm signal wherein h is a relay amplitude wherein p is a period of a relay feedback oscillation.