Design of nonlinear PID-smith predictor controllers with large time delays

The process with large time delay exhibit poor stability and significant overshoot with a conventional Smith Predictor or by using a simple PID controller. This is mainly because the additional phase lag contributed by the time delay tends to destabilize the closed loop system. In this work, an improvement by introducing a non-linear PID controller in a Smith predictor compensator is proposed. Therefore, it's important to note that the method can guarantee a small time response and a little overshoot than the conventional Smith predictor controller for a bounded non-linear gain in the sector. Finally, a numerical example is presented to show the applicability and performances of the proposed design.