title: Combined feedforward and model-assisted active disturbance rejection control for non-minimum phase system.
abstract: Control of the non-minimum phase (NMP) system is challenging, especially in the presence of modelling uncertainties and external disturbances. To this end, this paper presents a combined feedforward and model-assisted Active Disturbance Rejection Control (MADRC) strategy. Based on the nominal model, the feedforward controller is used to produce a tracking performance that has minimum settling time subject to a prescribed undershoot constraint. On the other hand, the unknown disturbances and uncertain dynamics beyond the nominal model are compensated by MADRC. Since the conventional Extended State Observer (ESO) is not suitable for the NMP system, a model-assisted ESO (MESO) is proposed based on the nominal observable canonical form. The convergence of MESO is proved in time domain. The stability, steady-state characteristics and robustness of the closed-loop system are analyzed in frequency domain. The proposed strategy has only one tuning parameter, i.e., the bandwidth of MESO, which can be readily determined with a prescribed robustness level. Some comparative examples are given to show the efficacy of the proposed method. This paper depicts a promising prospect of the model-assisted ADRC in dealing with complex systems.
authors.affiliation: State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China. Electronic address: sunli12@mails.tsinghua.edu.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.affiliation: State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China. Electronic address: lidongh@tsinghua.edu.cn.
authors.forename: Donghai
authors.initials: D
authors.lastname: Li
authors.affiliation: Center for Advanced Control Technologies, Cleveland State University, Cleveland, OH 44115, United States. Electronic address: z.gao@ieee.org.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Department of Mathematics, Baylor University, Waco, TX 76798, USA. Electronic address: Zhao_Yang@baylor.edu.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Yang
authors.affiliation: National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA. Electronic address: teddy__zhao@hotmail.com.
authors.forename: Shen
authors.initials: S
authors.lastname: Zhao
keywords: Active disturbance rejection control (ADRC); Extended state observer (ESO); Inverse response; Non-minimum phase (NMP) system