Extended state observer tuning for time-delay systems in the framework of internal model control

Active disturbance rejection control (ADRC) is a powerful tool in practical applications, which attracts wide attention in recent years. However, there are few systematic and useful tuning methods for it. In this paper, the linear ADRC for the typical first-order-plus-time-delay process is transformed into an internal model control (IMC) structure to perform insightful analysis. The corresponding controller, the filter, the multiplicative uncertainty and the complementary sensitivity function within the IMC framework are obtained, respectively. Then, the robust stability criterion in the frequency domain is employed to quantitatively investigate the effects of the parameters of the extended state observer (ESO), the key component of ADRC, on the closed-loop stability. According to the analysis, two tuning guidelines for the ESO are presented explicitly. Numerical simulations are used to validate the effectiveness of the proposed results.