Robust Backstepping Control for Small Helicopter

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Copyright: Roy, Tushar Kanti
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Abstract
This thesis is concerned with robust control theory and its application to the autonomous flight control system of small-scale unmanned autonomous helicopters. The goal of this thesis is to control a small-scale unmanned helicopter for different flight modes in the presence of external disturbances. The control approach is based on the backstepping control theory. Backstepping is a nonlinear control design method that provides an alternative to feedback linearization. It is based on Lyapunov theory, the control laws and a Lyapunov function are derived simultaneously. This Lyapunov function is used to guarantee the stability of the closed-loop system. Firstly, a robust backstepping control technique for the heave motion of a small-scale unmanned helicopter to automatic height control is proposed. In general, the control of a small-scale helicopter is a difficult task, because its system is highly nonlinear, coupled and sensitive to the control inputs and external disturbances. For simplicity, only vertical flight motion is focused on in this study. The influences of external wind gusts and the ground effect are taken into account within the heave motion model. When the performance of the proposed control method is examined in a computer simulation model, it is shown that it can achieve the desired height and compensate the effect of external wind gusts and the ground effect. Secondly, the horizontal position control for the linearized version of the non-linear model representing a small unmanned helicopter with external wind gusts is considered. Based on the Lyapunov stability theory, a stable robust backstepping controller is derived. For comparison purposes, another controller is also designed based on the linear quadratic regulator (LQR) criteria. To test their performances a computer simulation is conducted, which shows that the proposed controller has rapid horizontal position tracking and a good gust attenuation capability. Finally, a robust controller for the nonlinear system of a small-scale unmanned autonomous helicopter with unknown external wind gusts is considered. The robust backstepping control law is derived from the Lyapunov stability analysis which guarantees that the unknown external parameter estimation error is bounded. The proposed controller has the ability to stabilise the helicopter system and successfully achieves our control objective.
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Author(s)
Roy, Tushar Kanti
Supervisor(s)
Garratt, Matt
Pota, Hemanshu
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Publication Year
2012
Resource Type
Thesis
Degree Type
Masters Thesis
UNSW Faculty
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