An Anti-wind Modeling Method of Quadrotor Aircraft and Cascade Controller Design Based on Improved Extended State Observ
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ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555
An Anti-wind Modeling Method of Quadrotor Aircraft and Cascade Controller Design Based on Improved Extended State Observer Houyin Xi, Dong Zhang*, Tao Zhou, Yunxiao Yang, and Qiang Wei Abstract: Wind disturbance may significantly reduce the flight control performance of quadrotors when flying. In order to meet high performance flight control requirements, this paper presents a quadrotor anti-wind model (QAWM) and a flight control scheme for quadrotors. The QAWM takes the influence of aerodynamic effects on the propeller, gyroscopic effect and wind disturbance into account. The model can represent more flight states including not only hovering but also flight in windy conditions even maneuver flight. A cascade control scheme with an improved extended state observer (IESO) is adopted to decompose the quadrotor flight control problem into position control loop and attitude control loop. In the attitude control loop, the IESO is used to estimate the unmodeled dynamics, parameter uncertainties and external disturbances, as well as compensate the angular velocity control. In addition, the stability of IESO and the closed loop system are proved. Simulation and experimental results show the effectiveness of the nonlinear quadrotor model and control scheme, and the control scheme can effectively improve the flight performance of quadrotors under wind disturbance even maneuver flight. Keywords: Cascade control, maneuver flight, quadrotor, IESO, wind disturbances.
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INTRODUCTION
Quadrotor aircrafts are a new type of unmanned aerial vehicles(UAVs), which have four direct current(DC) motors divided into two pairs spinning in opposite direction [1]. Compared with traditional UAVs, quadrotors are simple and efficient in structure, enabling them to maneuver, vertical take-off and land (VTOL) and hover. Therefore, they are widely used in such fields as load transportation [2], urban monitoring [3], precision agriculture [4] and flight performance [5], etc. Quadrotors are an under-actuated system with six degrees of freedom (position and attitude) that are controlled by only four inputs [6]. Although quadrotors have great advantages in flight efficiency, volume, safety and other aspects than traditional UAVs, when operating in outdoor environments, like forest fire surveillance and maneuver flight, quadrotors would be easily affected by wind field [7]. In addition, quadrotors are an under-actuated nonlinear coupling system with certain parameters which are dependent on the characteristics of the flight [8]. These factors make the control system design more complicated. Therefore, the development of anti-wind disturbance controller of quadrotors is meaningful, which should take
model nonlinearities and uncertainties into consideration. Some related academic institutions have reported much progress and demonstrated some flight capabilities of quadrotors. However, the reported results have not yet reached the theoretical potential of quadrotors. This is mainly due to th
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