scholarly journals Intelligent Observer-Based Feedback Linearization for Autonomous Quadrotor Control

2018 ◽  
Vol 7 (4.35) ◽  
pp. 904 ◽  
Author(s):  
Izzuddin M. Lazim ◽  
Abdul Rashid Husain ◽  
Nurul Adilla Mohd Subha ◽  
Mohd Ariffanan Mohd Basri

The presence of disturbances can cause instability to the quadrotor flight and can be dangerous especially when operating near obstacles or other aerial vehicles. In this paper, a hybrid controller called state feedback with intelligent disturbance observer-based control (SF-iDOBC) is developed for trajectory tracking of quadrotor in the presence of time-varying disturbances, e.g. wind. This is achieved by integrating artificial intelligence (AI) technique with disturbance observer-based feedback linearization to achieve a better disturbance rejection capability. Here, the observer estimates the disturbances acting on the quadrotor, while AI technique using the radial basis function neural network (RBFNN) compensates the disturbance estimation error. To improve the error compensation of RBFNN, the k-means clustering method is used to find the optimal centers of the Gaussian activation function. In addition, the weights of the RBFNN are tuned online using the derived adaptation law based on the Lyapunov method, which eliminates the offline training. In the simulation experiment conducted, a total of four input nodes and five hidden neurons are used to compensate for the error. The results obtained demonstrate the effectiveness and merits of the theoretical development. 

2019 ◽  
Vol 42 (2) ◽  
pp. 272-284 ◽  
Author(s):  
Rongsheng Xia ◽  
Qingxian Wu ◽  
Shuyi Shao

This paper presents a disturbance observer-based robust optimal flight control strategy for near space vehicle (NSV) attitude system with external time-varying disturbance generated by an exogenous system. For the purpose of eliminating the effect of the disturbance, nonlinear disturbance observer (NDO) technique is used and the disturbance estimation error is guaranteed to be globally exponential convergence. Then, based on the disturbance estimation result and desired trajectory signal, a steady state control input is presented and the optimal tracking problem of original system with external disturbance can be converted into the optimal regulation problem of a nominal error system. Furthermore, a single network-based adaptive dynamic programming (ADP) method is applied to obtain the corresponding optimal feedback control law. Finally, all the signals in closed-loop system are proved to be uniformly ultimately bounded (UUB) and the tracking error can converge to a sufficiently small bound. Simulation tests about NSV attitude system are given to verify the effectiveness of proposed robust optimal flight control scheme.


Author(s):  
Wen Xinyu ◽  
Zhang Junjie ◽  
Yao Xiuming

A disturbance rejection approach is presented for a class of uncertain systems subject to sinusoidal disturbance with unknown frequency. The proposed disturbance estimation method includes two types of observers that are connected in cascade form. The disturbance property is excited through an auxiliary filter, and then a frequency factor observer is constructed to generate the information required by full-order state observer. Thus, with the disturbance and system state estimation values, the composite control structure including a cascade disturbance observer (CDO) and a robust feedback controller is designed. As a result, the uncertain system with unknown-frequency sinusoidal component can be controlled within the disturbance observer-based control (DOBC) framework, where the asymptotic stability performance can be guaranteed.


2019 ◽  
Vol 42 (3) ◽  
pp. 339-350 ◽  
Author(s):  
Qibing Jin ◽  
Wu Cai ◽  
Xinghan Du

In this paper, a modified multivariable disturbance observer-based (MDOB) design method is proposed to improve disturbance rejection performance for multiple-input-multiple-output (MIMO) processes with multiple time delays. Two important issues in MDOB control are studied here: computation of the inverse model and design of the filter. First, to reduce the influence of time delays, the nominal process is factorized as a diagonal time delay matrix and a remaining transfer function matrix, and the remaining part is used to design the inverse model in MDOB. Considering the difficulty of matrix inversion, the Nyquist set is used to describe the dynamic of the inverse model, and accordingly, the simplified inverse model is obtained by the curve fitting technique. In addition, to guarantee the properness and stability of the simplified inverse model, a compensator is introduced. Rules for selecting compensator parameters are given. Finally, with the proposed inverse model and compensator, the filter [Formula: see text] is optimized by minimizing the H∞ norm of the disturbance estimation error. The filter constants are determined by fully consider the disturbance rejection performance and robustness of the system. Simulation examples are presented to illustrate the effectiveness and merits of the proposed method.


2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Xinkai Chen

Inspired by sliding mode techniques, a nonlinear exact disturbance observer is proposed. The disturbance and its derivatives up to the second order are assumed to be bounded. However, the bounds of the disturbance and its derivatives are unknown, and they are adaptively estimated online during the observation of the disturbances. The exact convergence of the disturbance observer to the genuine disturbance is assured theoretically. The convergence speed of the disturbance estimation error is controlled by design parameters. The proposed method is robust to the type of disturbance and is easy to be implemented. Computer simulation results show the superiority and effectiveness of the proposed formulation.


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