Efficient Deep Learning of Robust, Adaptive Policies using Tube MPC-Guided Data Augmentation

The deployment of agile autonomous systems in challenging, unstructured environments requires adaptation capabilities and robustness to uncertainties. Existing robust and adaptive controllers, such as those based on model predictive control (MPC), can achieve impressive performance at the cost of heavy online onboard computations. Strategies that efficiently learn robust and onboard-deployable policies from MPC have emerged, but they still lack fundamental adaptation capabilities. In this work, we extend an existing efficient Imitation Learning (IL) algorithm for robust policy learning from MPC with the ability to learn policies that adapt to challenging model/environment uncertainties. The key idea of our approach consists in modifying the IL procedure by conditioning the policy on a learned lower-dimensional model/environment representation that can be efficiently estimated online. We tailor our approach to the task of learning an adaptive position and attitude control policy to track trajectories under challenging disturbances on a multirotor. Evaluations in simulation show that a high-quality adaptive policy can be obtained in about 1.3 hours. We additionally empirically demonstrate rapid adaptation to in- and out-of-training-distribution uncertainties, achieving a 6.1 cm average position error under wind disturbances that correspond to about 50% of the weight of the robot, and that are 36% larger than the maximum wind seen during training.

I. Introduction

The deployment of agile robots in uncertain environments demands strong robustness and rapid onboard adaptation capabilities. Approaches based on model predictive control (MPC), such as robust/adaptive MPC [1]–[5], achieve impressive robustness and adaptation performance under real-world uncertainties, but their computational cost, associated with solving a large optimization problem online, hinders deployment on computationally constrained platforms.