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Mathematical Problems in Engineering
Volume 2016, Article ID 3154842, 24 pages
http://dx.doi.org/10.1155/2016/3154842
Research Article

Robust Optimal Attitude Controller for MIMO Uncertain Hexarotor MAVs: Disturbance Observer-Based

1Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, 54100 Kuala Lumpur, Malaysia
2Mechatronic Systems Laboratory, Robotic Systems Enterprise, 75250 Melaka, Malaysia
3Department of Mechanical Engineering, Graduate School of Engineering, Chiba University, Chiba Prefecture, Chiba 263-0022, Japan
4Autonomous Control Systems Laboratory Ltd., Chiba-ken, Chiba 263-8522, Japan

Received 22 October 2015; Accepted 31 March 2016

Academic Editor: Andrzej Swierniak

Copyright © 2016 Nurul Dayana Salim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper proposes a robust optimal attitude control design for multiple-input, multiple-output (MIMO) uncertain hexarotor micro aerial vehicles (MAVs) in the presence of parametric uncertainties, external time-varying disturbances, nonlinear dynamics, and coupling. The parametric uncertainties, external time-varying disturbances, nonlinear dynamics, and coupling are treated as the total disturbance in the proposed design. The proposed controller is achieved in two simple steps. First, an optimal linear-quadratic regulator (LQR) controller is designed to guarantee that the nominal closed-loop system is asymptotically stable without considering the total disturbance. After that, a disturbance observer is integrated into the closed-loop system to estimate the total disturbance acting on the system. The total disturbance is compensated by a compensation input based on the estimated total disturbance. Robust properties analysis is given to prove that the state is ultimately bounded in specified boundaries. Simulation results illustrate the robustness of the disturbance observer-based optimal attitude control design for hovering and aggressive flight missions in the presence of the total disturbance.