Add-On Module of Active Disturbance Rejection for Set-Point Tracking of Motion Control Systems

Active disturbance rejection control (ADRC) as a standalone motion solution has been made available in recent years on various industrial platforms. The idea of ADRC, however, can be integrated with the existing control technologies seamlessly, as shown in this paper. A modularized ADRC design is proposed in this particular work for set-point tracking task in motion control, such that better uncertainty rejection can be obtained without any change in the existing proportional-derivative control with a linear observer. It is proven that a certain extended state of the observer, i.e., the integration of the observer error, can serve as an estimation for the 'total disturbance' in low-frequency range by only tuning the augmented gain. This enables the estimation and cancellation of the 'total disturbance' to be incorporated into the existing control loop. Also, a comparison between the methods with and without such 'module' is discussed. The proposed ADRC is implemented and validated experimentally using a laboratory manipulator, where the desired set-point tracking performance in position control is achieved under unknown mass variations and sudden external disturbances.