Unified Interpretation of Active Disturbance Rejection Control for Electrical Drives

Variable structure active disturbance rejection control (ADRC), represented by generalized ADRC (GADRC) and cascaded ADRC (CADRC), has attracted extensive attention due to its superior disturbance rejection performance. This brief investigates a unified interpretation of GADRC and CADRC. To be specific, GADRC and CADRC can be interpreted as a class of generalized proportional-integral-derivative (PID) controller in series with a low-pass filter. Moreover, the transfer functions of disturbance estimation for the generalized extended state observer (GESO) and cascaded ESO (CESO) of the first-order system can be regarded as a class
$Q$
-filter with relative degree 2, from which the equivalence between them can be established. Besides, the selection principles of GESO orders and CESO levels are established based on the disturbance type. Finally, some relevant simulations are performed to present the performance differences between first-order ADRC, second-order GADRC, two-level CADRC and their generalized PID controllers for speed electric drive system. The results show that the ADRC controllers have similar disturbance rejection capability to the corresponding generalized PID controllers, which will provide guidelines for circuit and system engineers to tune generalized PID parameters.