*3.2.1.4 Characteristic variables* |Δen*•*Δen�*1*|

The magnitude of the absolute value of the ratio of the error change at the current moment to the error change at the previous moment is defined as the characteristic variable describing the local change trend of the system error. It also indirectly indicates the effect of early control. If the ratio is large, it indicates that the effect of early control is not significant; if the ratio is small, it indicates that the effect of early control is significant.

*Overview of Some Intelligent Control Structures and Dedicated Algorithms DOI: http://dx.doi.org/10.5772/intechopen.91966*
