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 adopted by companies such as Texas Instruments and Danfoss and made available on various proprietary industrial platforms. The idea of ADRC, however, can be integrated with the existing control technologies seamlessly, as shown in this paper. It is shown a modularized ADRC design for set-point tracking of motion control such that better uncertainty rejection can be implemented without any change in the existing proportional-derivative (PD) control with linear observer. We prove that certain integration of the observer's error can serve as an estimation for the “total disturbance” in low frequency range. 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 with experimental results for a 1-degree of freedom robotic manipulator, where desired set-point tracking performance in position control is achieved under unknown mass variations and sudden external disturbances.