Abstract
Precise trajectory control near ground is difficult for multi-rotor drones, due to the complex ground effects caused by interactions between multi-rotor airflow and the environment. Conventional control methods often fail to properly account for these complex effects and fall short in accomplishing smooth landing. In this paper, we present a novel deep-learning-based robust nonlinear controller (Neural-Lander) that improves control performance of a quadrotor during landing. Our approach blends together a nominal dynamics model coupled with a Deep Neural Network (DNN) that learns the high-order interactions. We employ a novel application of spectral normalization to constrain the DNN to have bounded Lipschitz behavior. Leveraging this Lipschitz property, we design a nonlinear feedback linearization controller using the learned model and prove system stability with disturbance rejection. To the best of our knowledge, this is the first DNN-based nonlinear feedback controller with stability guarantees that can utilize arbitrarily large neural nets. Experimental results demonstrate that the proposed controller significantly outperforms a baseline linear proportional-derivative (PD) controller in both 1D and 3D landing cases. In particular, we show that compared to the PD controller, Neural-Lander can decrease error in z direction from 0.13m to zero, and mitigate average x and y drifts by 90% and 34% respectively, in 1D landing. Meanwhile, Neural-Lander can decrease z error from 0.12m to zero, in 3D landing. We also empirically show that the DNN generalizes well to new test inputs outside the training domain.
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URL
https://arxiv.org/abs/1811.08027
