Question

what is saturation and non saturation of a controller

Answer 1

In literal sense, Saturation or non Saturation of a controller is related to maximum and minimum limits of a response a controller can achieve.

Saturation is basically a non linear response because the output is fixed for a controller outside the bounds of linear responses.

Due to this reason when saturation cannot be avoided, controller performance decreases.

For example a control valve cannot be more open than Fully Open, this is saturation

An equipment cannot consumr more electricity than supplied.

When the operation is in the limits of response the scenario is called non saturation of controllers.