In this study, a flight control design strategy based on incremental nonlinear dynamic inversion (INDI) and smoothing algorithm is presented. The INDI is an enhanced version of the nonlinear dynamic inversion technique with a better robust performance. It reduces the aircraft model dependence via the feedback information of the state derivative, that is, angular acceleration for the aircraft attitude motion (or angular velocity related to the wind axis parameters). However, the state derivatives cannot always be obtained by direct measurement, thus they need to be estimated on-line. Moreover, taking into account that INDI requires one-step delay of state derivative and the fact that the inertial measurement unit (IMU) operates faster than the flight control computer (FCC), there will be additional information that can be used to improve the estimation. Therefore, a fixed-lag smoothing algorithm based on a discrete Kalman filter is proposed for angular velocity and angular acceleration estimation. The smoother utilizes the state variable from the sensor measurement and thus dealing with noise and delay.

中文翻译：

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使用增量非线性动态反演和固定滞后平滑估计的飞行控制设计

在这项研究中，提出了一种基于增量非线性动态反演（INDI）和平滑算法的飞行控制设计策略。INDI 是非线性动态反演技术的增强版本，具有更好的鲁棒性。它通过状态导数的反馈信息，即飞机姿态运动的角加速度（或与风轴参数相关的角速度）来降低飞机模型的依赖性。然而，状态导数不能总是通过直接测量获得，因此需要在线估计它们。此外，考虑到INDI需要状态导数的一步延迟以及惯性测量单元（IMU）的运行速度比飞控计算机（FCC）快，将有额外的信息可用于改进估计。因此，提出了一种基于离散卡尔曼滤波器的固定滞后平滑算法用于角速度和角加速度估计。平滑器利用来自传感器测量的状态变量，从而处理噪声和延迟。