The Ziegler-Nichols method is used to tune the continuoustime
controller. In this kind of tuning is necessary be found the
value of the gain Ker which makes the system critically stable
using an integral gain equal to zero (Ti = 00). With the value
of Ken the parameters in (16) are calculated as K = 0.45Ker
and Ti = Per/1.2, where Per is the system critical oscillation
period with gain Ker [6] .