Simplified computation of robust stability region for DOB-based control system with parametric uncertainty

Abstract

Motivated by the conservatism and complexity of the existing robust stability analysis method for disturbance observer (DOB)-based control system, a robust stability analysis method, addressing parametric uncertainty, is proposed for different relative order processes with time delay. By Bounded Phase Condition, a simplified Generalised Kharitonov Theory is proposed for stability analysis of inner loop, replacing the redundant stability verification of generalised Kharitonov segment polynomial by stabilising the end points of the segment polynomial. Then, based on the simplified theorem and the stability equation method, all the feasible low pass filter (LPF) parameters that stabilised the inner-loop can be obtained. It is the first time that all the feasible LPF parameters are given for different relative order. Furthermore, the proposed method is extended to ensure the stability of outer loop and obtain the admissible range of controller parameter. Simulation studies present how to obtain the stability region and demonstrate the validity of the proposed method.