In order to further expand the flight envelope of quadrotors under actuator failures, we design a nonlinear sensor-based fault-tolerant controller to stabilize a quadrotor with failure of two opposing rotors in the high-speed flight condition (> 8m/s). The incremental nonlinear dynamic inversion (INDI) approach which excels in handling model uncertainties is adopted to compensate for the significant unknown aerodynamic effects. The internal dynamics of such an underactuated system have been analyzed, and subsequently stabilized by re-defining the control output. The proposed method can be generalized to control a quadrotor under single-rotor-failure and nominal conditions. For validation, flight tests have been carried out in a large-scale open jet wind tunnel. The position of a damaged quadrotor can be controlled in the presence of significant wind disturbances. A linear quadratic regulator (LQR) approach from the literature has been compared to demonstrate the advantages of the proposed nonlinear method in the windy and high-speed flight condition.

中文翻译：

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两个相对转子完全丢失的四旋翼增量非线性容错控制

为了进一步扩大执行器故障下四旋翼飞行器的飞行包线，我们设计了一种基于非线性传感器的容错控制器，以在高速飞行条件下（> 8m / s）稳定具有两个相对旋翼故障的四旋翼飞行器。采用在处理模型不确定性方面表现出色的增量非线性动力反演（INDI）方法来补偿显着的未知气动效应。这种欠驱动系统的内部动力学已经过分析，随后通过重新定义控制输出来稳定。所提出的方法可以推广到在单转子故障和标称条件下控制四旋翼飞行器。为了验证，已在大型开放式喷气风洞中进行了飞行测试。在存在严重风扰的情况下，可以控制损坏的四旋翼飞行器的位置。比较了文献中的线性二次调节器 (LQR) 方法，以证明所提出的非线性方法在有风和高速飞行条件下的优势。