Omnidirectional Dual-Arm Aerial Manipulator with Proprioceptive Contact Localization for Landing on Slanted Roofs

TL;DR

The paper tackles robust perching and landing of aerial manipulators on inclined urban roofs where exteroceptive sensing can be unreliable. It introduces an omnidirectional dual-arm aerial manipulator with a proprioceptive contact localization pipeline based on a momentum-based torque observer, enabling blind assessment of surface inclination prior to touchdown. Flight tests demonstrate landings on surfaces up to 30.5 degrees with an average inclination estimation error of 2.87 degrees across nine experiments, validating the approach's accuracy and reliability. This sensorless geometry learning approach reduces dependence on vision or LIDAR and broadens UAM capabilities for urban operations.

Abstract

Operating drones in urban environments often means they need to land on rooftops, which can have different geometries and surface irregularities. Accurately detecting roof inclination using conventional sensing methods, such as vision-based or acoustic techniques, can be unreliable, as measurement quality is strongly influenced by external factors including weather conditions and surface materials. To overcome these challenges, we propose a novel unmanned aerial manipulator morphology featuring a dual-arm aerial manipulator with an omnidirectional 3D workspace and extended reach. Building on this design, we develop a proprioceptive contact detection and contact localization strategy based on a momentum-based torque observer. This enables the UAM to infer the inclination of slanted surfaces blindly - through physical interaction - prior to touchdown. We validate the approach in flight experiments, demonstrating robust landings on surfaces with inclinations of up to 30.5 degrees and achieving an average surface inclination estimation error of 2.87 degrees over 9 experiments at different incline angles.

Figures (11)

• Figure 1: Mosaic image of the dual-arm aerial manipulator in different configurations, showcasing the omnidirectional workspace.
• Figure 2: A. The dual-arm omnidirectional aerial manipulator and its main reference frames with axes colored red, green, and blue (RGB) for the X-, Y-, and Z-axes, respectively, B. Kinematics of a single manipulator arm, with axis of rotation of $q_1$ coinciding with the body x-axis.
• Figure 3: Close up view of the pivot joint mechanism that enables omnidirectional motion about the UAM's centre of mass. A) shows key components inside the front axle block, including the planetary gear mechanism. B) shows the full pivot joint assembly with the axle blocks and servo.
• Figure 4: Top view of the aerial manipulator's out-of-the-plane motion.
• Figure 5: Three-dimensional workspace plots of the novel aerial manipulator. The blue line marks the workspace outline and the grey points are sampling points. The left plot shows the workspace in the YZ-plane. The right plot shows the workspace in the XZ-plane, i.e. the out-of-plane reach.