 Another heuristic tuning method is formally known as the Ziegler–Nichols method, introduced by John G. Ziegler and Nathaniel B. Nichols in the 1940s.As in the method above, the formula_38 and formula_39 gains are first set to zero.The proportional gain is increased until it reaches the ultimate gain, formula_50, at which the output of the loop starts to oscillate constantly.