On active disturbance rejection control for lower-triangular systems with mismatched nonlinear uncertainties and unknown time-varying control coefficients

2021 ◽  
Author(s):  
Ping Liu ◽  
Sen Chen ◽  
Zhi-Liang Zhao
Keyword(s):  
Disturbance Rejection ◽  
Time Varying ◽  
Active Disturbance Rejection Control ◽  
Active Disturbance Rejection ◽  
Triangular Systems ◽  
Disturbance Rejection Control ◽  
Nonlinear Uncertainties ◽  
Lower Triangular ◽  
Control Coefficients

scholarly journals On active disturbance rejection control for lower-triangular nonlinear uncertain systems with mismatched uncertainties and unknown control coefficients

2021 ◽  
Author(s):  
Ping Liu ◽  
Sen Chen ◽  
Zhi-Liang Zhao
Keyword(s):  
Disturbance Rejection ◽  
Uncertain Systems ◽  
Active Disturbance Rejection ◽  
Disturbance Rejection Control ◽  
Mismatched Uncertainties ◽  
Nonlinear Uncertain Systems ◽  
Unknown Control Coefficients ◽  
Lower Triangular ◽  
Unknown Control ◽  
Control Coefficients

Abstract The paper investigates the control problem for a class of lower-triangular nonlinear uncertain systems with mismatched uncertainties and unknown values of control coefficients. Based on the signs of control coefficients rather than the nominal values or the approximative mathematical expressions, a new active disturbance rejection control is proposed. The design procedure can be concluded by three steps: determining the equivalent integrators chain form, constructing the extended state observer to estimate the total disturbance, and designing a dynamical system to let the actual input track the ideal input. Then under a mild assumption for mismatched uncertainties and unknown control coefficients, the paper rigorously analyzes the bounds of tracking error, estimating error and the error between the actual and ideal inputs. The presented theoretical results reveal the strong robustness of the proposed method to mismatched uncertainties and uncertain control input coefficients. Moreover, the tuning law of observer parameter and the parameter of dynamical input design is theoretically shown.

A Novel Time-Varying Spectrum Based Approach to Active Disturbance Rejection Control

2017 ◽  
Author(s):  
Zhiqiang Pu ◽  
Xiangmin Tan ◽  
Ruyi Yuan ◽  
Jianqiang Yi
Keyword(s):  
Disturbance Rejection ◽  
Parameter Tuning ◽  
Stability And Convergence ◽  
Time Varying ◽  
Active Disturbance Rejection Control ◽  
Loop Control ◽  
Active Disturbance Rejection ◽  
State Dependent ◽  
Disturbance Rejection Control ◽  
Improved Performance

This paper presents a comprehensive framework for developing a novel time-varying spectrum based active disturbance rejection control (TVS-ADRC) technique. It complements conventional linear or nonlinear ADRC by introducing time-varying components, including time-varying extended state observer, time-varying tracking differentiator, and time-varying feedback, to offer better design flexibility and improved performance in command filtering, disturbance observation, and closed-loop control. First, skeleton stability and convergence analysis is introduced based on differential algebraic spectral theory. Then parameter tuning is categorized into two time-varying principles: a time-based profile and a state-dependent function, and a unified parameterization approach is given by assigning time-varying eigenvalues. Typical applications are pointed out which demonstrate great advantages of TVS-ADRC in consideration of varying plant or environment features and physical limits in practical systems. Challenges and future work for the TVS-ADRC technique are also summarized in the end.

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