The majority of commercial and open-source autopilot software for uncrewed aerial vehicles rely on the tried and tested extended Kalman filter (EKF) to provide the state estimation solution for the inertial navigation system (INS). While modern implementations achieve remarkable robustness, it is often due to the careful implementation of exception code for a multitude of corner cases along with significant skilled tuning effort. In this paper, we use the data wealth of the ArduPilot community to identify and highlight the most common real-world challenges in INS state estimation, including sensor self-calibration, robustness in static conditions, global navigation satellite system (GNSS) outliers and shifts, and robustness to faulty inertial measurement units (IMUs). We propose a novel equivariant filter (EqF) formulation for the INS solution that exploits a Semi-Direct-Bias symmetry group for multi-sensor fusion with self-calibration capabilities and incorporates equivariant velocity-type measurements. We augment the filter with a simple innovation-covariance inflation strategy that seamlessly handles GNSS outliers and shifts without requiring coding of a whole set of exception cases. We use real-world data from the Ardupilot community to demonstrate the performance of the proposed filter on known cases where existing filters fail without careful exception handling or case-specific tuning and benchmark against the ArduPilot’s EKF3, the most sophisticated EKF implementation currently available.

The research community presented significant advances in many different Visual-Inertial Navigation System (VINS) algorithms to localize mobile robots or hand-held devices in a 3D environment. While authors of the algorithms of-ten do compare to, at that time, existing competing approaches, their comparison methods, rigor, depth, and repeatability at later points in time have a large spread. Further, with existing simulators and photo-realistic frameworks, the user is not able to easily test the sensitivity of the algorithm under examination with respect to specific environmental conditions and sensor specifications. Rather, tests often include unwillingly many polluting effects falsifying the analysis and interpretations. In addition, edge cases and corresponding failure modes often remain undiscovered due to the limited breadth of the test sequences. Our unified evaluation framework allows, in a fully automated fashion, a reproducible analysis of different VINS methods with respect to specific environmental and sensor parameters. The analyses per parameter are done over a multitude of test sets to obtain both statistically valid results and an average over other, potentially polluting effects with respect to the one parameter under test to mitigate biased interpretations. The automated performance results per method over all tested parameters are then summarized in unified radar charts for a fair comparison across authors and institutions.

Monocular Visual-Inertial Odometry (VIO) has become ubiquitous for navigation of autonomous Micro Air Vehicles (MAVs). Yet, state-of-the-art VIO is still very failure-prone, which can have dramatic consequences. To prevent this, VIO must be able to re-initialize in mid-air, either during a free fall or on a constant velocity trajectory after attitude control has been re-established. However, for both of these trajectories, the visual scale cannot be observed with VIO batch initializers because of the absence of acceleration change. We propose to use a small and lightweight laser-range finder (LRF) and a scene facet model to initialize vision-based navigation at the right scale under any motion condition and over any scene structure. This new range constraint is integrated into a visual-inertial bundle-adjustment initializer. We evaluate our approach in simulation, including robustness to various parameters, and demonstrate on real data how this approach can address midair state estimation failure in real-time.

We propose an approach to the throw-and-go (TnG) problem for micro air vehicles (MAVs) using visual and inertial sensors. The key challenge is the fast on-board initialization of the visual odometry (VO) system, which usually requires user input to recover the visual scale. Our approach is based on the identification of the gravity vector from the acceleration data computed with images of the ground during in free fall. This enables scaling of the poses reconstructed with visual information. The proposed framework use inertial data to control the MAV attitude so the ground is visible after the throw. Using image to image homography a metric scale is estimated with which the MAV's height is propagated. Unlike existing literature, this approach requires no additional sensor nor user input or pre-throw assumptions and can recover from any initial attitude. We show results on both simulation and real data.