| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 106 === This paper aims to propose a strategy for quad-rotors flight control under rotor failure. The proposed control strategy consists of two stages – FDI (fault detection and isolation) part and the FTC (fault tolerant control) part. The control method takes normal flight as well as abnormal flight into consideration. The algorithm that switches the control law between the aforementioned two cases relies on the FDI result. As a consequence, the accuracy of the FDI becomes one of the important issues for field safety flight control. To achieve the FDI, a model based method for fault detection and fault estimation is developed. As for the fault detection, an adaptive boundary of the residues generated from the nonlinear observer is applied, and the fault alarm is going to be triggered if any of the residues exceeds prescribed upper/lower bounds. On the other hands, the update law of fault estimation is formed within the stability analysis of state estimation error, which requires the application of the nonlinear observer. With the combination of the results from fault detection and fault estimation, the judgment in deciding whether the fault actually happens or not could be made. While fault happening, a control strategy that stabilizes the system and keeps the trajectory ability of the quad-rotor is required. To this aim, a coordinate transformation scheme is applied, which corrects the target angles for the quad-rotor to follow a desired trajectory. Furthermore, in order to achieve robust flight during the external wind perturbation, the sliding mode control (SMC) theory is used. Finally, simulations are applied to illustrate the effectiveness and feasibility of the fault control strategy. Numerical results show that the proposed method is able to achieve robust flight even in the presence of rotor failures.
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