Nonlinear disturbance rejection of a flexible robot

2001 ◽  
Author(s):  
M. Brocker
Keyword(s):  
Disturbance Rejection ◽  
Flexible Robot ◽  
Nonlinear Disturbance

Robust Attitude Control for Quadrotors Based on Parameter Optimization of a Nonlinear Disturbance Observer

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Shatadal Mishra ◽  
Todd Rakstad ◽  
Wenlong Zhang
Keyword(s):  
Flight Control ◽  
Attitude Control ◽  
Disturbance Rejection ◽  
Disturbance Observer ◽  
Control Unit ◽  
Nonlinear Disturbance Observer ◽  
Wave Disturbances ◽  
Active Disturbance Rejection ◽  
Exogenous Disturbances ◽  
Nonlinear Disturbance

This paper presents a nonlinear disturbance observer (NDOB) for active disturbance rejection in the attitude control loop for quadrotors. An optimization framework is developed for tuning the parameter in the NDOB structure, which includes the infinity-norm minimization of the weighted sum of noise-to-output transfer function and load disturbance sensitivity function. Subsequently, the minimization generates an optimal value of the parameter based on the tradeoff between disturbance rejection and noise propagation in the system. The proposed structure is implemented on PIXHAWK, a real-time embedded flight control unit. Simulation tests are carried out on a custom built, high-fidelity simulator providing physically accurate simulations. Furthermore, experimental flight tests are conducted to demonstrate the performance of the proposed approach. The system is injected with step, sinusoidal, and square wave disturbances, and the corresponding system tracking performance is recorded. Experimental results show that the proposed algorithm attenuates the disturbances better compared to just a baseline controller implementation. The proposed algorithm is computationally cheap, an active disturbance rejection technique and robust to exogenous disturbances.

Robust composite nonlinear feedback control for spacecraft rendezvous systems under parameter uncertainty, external disturbance, and input saturation

2018 ◽  
Vol 234 (2) ◽  
pp. 143-155
Author(s):  
Hasan Namdari ◽  
Firouz Allahverdizadeh ◽  
Alireza Sharifi
Keyword(s):  
Feedback Control ◽  
Disturbance Rejection ◽  
Closed Loop ◽  
Input Saturation ◽  
Lyapunov Theory ◽  
System Stability ◽  
Nonlinear Feedback Control ◽  
Nonlinear Feedback ◽  
Composite Nonlinear Feedback ◽  
Nonlinear Disturbance

This paper presents a new robust composite nonlinear feedback control law for accurate, smooth, and fast regulation in the presence of parameter uncertainties, external disturbances, and input saturation for a class of spacecraft rendezvous systems. The novel proposed method consists of the original composite nonlinear feedback part for good transient performance plus a nonlinear disturbance rejection part for reducing the steady-state error stemming from variable disturbances and simultaneously producing feasible control input. The nonlinear disturbance rejection relies on sliding-mode observer for disturbance estimation. Closed-loop system stability has been proved with the Lyapunov theory. Simulation results show the closed-loop stability and superior control performance.

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