Disturbance observer-based control schemes for quadrotors – a tutorial

In this article, an analysis and synthesis of widely used linear disturbance observer based robust control approaches are presented. The main objective of this article is to provide an exhaustive comparison of disturbance observer based robust control approaches and to handle the structural details of each approach for gaining insight about the complexity of each approach. Toward this goal, nine performances and robustness equations portraying useful insights for understanding and analyzing control systems are derived by examining their common and equivalent block diagrams. Four of them are selected as gang of four equations, namely complementary sensitivity function, sensitivity function, disturbance sensitivity function and noise sensitivity function. Robustness and disturbance rejection performance analysis of all linear disturbance observer based control schemes and classical feedback control scheme are done using gang of four equations. With these representations, two tables discussing all prime issues and facilitating the selection of the best approach are obtained. Our research stipulates critical facts and figures of each scheme by considering the derived gang of four equations, which can be used for choosing the most appropriate disturbance observer based control approach for a given robust control problem. It is concluded that the uncertainty disturbance estimator approach is superior when time delay type uncertainty is involved in the model. Unfolding this is critical as time delay is an inevitable fact in most industrial control systems. The findings also emphasize that time domain disturbance observer based control approach is proficient if there is no process time delay.

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Synchronizing Spatiotemporal Chaos via a Composite Disturbance Observer-Based Sliding Mode Control

Mathematical Problems in Engineering ◽

10.1155/2014/693268 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7

Author(s):

Congyan Chen ◽

Shi Qiu

Keyword(s):

Sliding Mode Control ◽

Disturbance Observer ◽

Sliding Mode ◽

Spatiotemporal Chaos ◽

Practical Application ◽

Control Effort ◽

Synchronization Errors ◽

Mode Control ◽

System A ◽

Control Schemes

The sliding mode control schemes are investigated to synchronize two spatiotemporal chaotic systems, which are two arrays of a large number of coupled chaotic oscillators. Firstly, sliding mode manifolds with the desired performance are designed. The asymptotic convergence to the origin of the synchronization errors is also proved. However, the terms from parameter fluctuations in equivalent controls are usually impossible to be measured directly. So we regard them as lumped disturbances, but, for practical application, it is difficult to obtain the upper bound of lumped disturbances in advance which often results in a conservative sliding mode control law with large control effort, causing a large amount of chattering. To reduce the chattering and improve the performance of the system, a disturbance observer is designed to estimate the lumped disturbances. A composite synchronization controller that consists of a sliding mode feedback part and a feedforward compensation part based on disturbance observer is developed. The numerical simulation results are presented to show the effectiveness of the proposed methods.

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