On linear/nonlinear active disturbance rejection switching control

Nonlinear active disturbance rejection control (NLADRC) is superior to linear active disturbance rejection control (LADRC) in tracking precision, anti-disturbance ability, and so on. However, there are difficulties in parameter tuning, stability analysis, performance analysis, etc, which inhibits its application. Therefore, LADRC is more popular in engineering applications. This paper presents a linear/nonlinear active disturbance rejection switching control method, which has both of the advantages of LADRC and NLADRC, and solves the problems of parameter tuning, stability analysis, etc. Firstly, the characteristics of LADRC and NLADRC are presented, and then a switching strategy is proposed. Secondly, a simple practical parameter tuning method is provided. Thirdly, the stability is analyzed through Routh criterion and Popov criterion. Simulations show that the switching control method is superior to both LADRC and NLADRC in tracking precision and anti-disturbance. The proposed method fully demonstrates the advantages of nonlinear functions in occasions when high tracking precision and strong anti-disturbance ability are needed, and is hopefully to be adopted in practical application.