Universal Integral Control: An Approach Based on Mollifiers

The Universal Integral Control, introduced by H.K. Khalil (Universal integral controllers for minimum-phase nonlinear systems, IEEE Trans. Autom. Control, vol. 45, no. 3), is revisited by employing mollifiers instead of a high-gain observer for the differentiation of the output signal. The closed-loop system is a classical functional differential equation with distributed delays on which standard Lyapunov arguments are applied to study the stability. Low-pass filtering capability of mollifiers is demonstrated for a high amplitude and rapidly oscillating noise. The controller is supported by numerical simulations.