Suppressing High-Frequency External Disturbance in Active Disturbance Rejection Control

Active disturbance rejection control (ADRC) is a popular general control approach whose basic idea has intrinsic relationship with model-based fault diagnosis. This paper investigates the ability of suppressing high-frequency external disturbance of low-order linear ADRC. It finds when the linear ADRC system is stable, the ability can be described with Bode diagram. For the plants with low-pass property, the ability depends on the plant. Furthermore, this paper finds an example that linear ADRC suppresses an external disturbance with unbounded derivative. Thus, in ADRC, the total disturbance may have unbounded derivative.