Modeling and Control of UAV Bearing Formations with Bilateral High-level Steering

Abstract

Abstract-In this paper we address the problem of controlling the motion of a group of UAVs bound to keep a formation defined in terms of only relative angles (i.e., a bearing-formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g., exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing-formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information.The controller still leaves the possibility to impose group motions tangent to the current bearing-formation. These can be either autonomously chosen by the robots because of any additional task (e.g., exploration), or exploited by an assisting human co-operator. For this latter 'human-in-the-loop' case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g., limited field-of-view, are also considered.

Human-Collaborative Schemes in the Motion Control of Single and Multiple Mobile Robots

“…In the experiments presented in [34] a human operator controls a group of aerial robots that use onboard cameras to measure the relative angles between themselves while the velocity is still estimated using an external motion capture system.…”

Bearing-only formation control using an SE(2) rigidity theory

“…If (G, p, ψ) is rigid then one could, for instance, exploit the distributed estimation strategy illustrated in [1] for recovering the quantity T (ψ j −ψ i ) from the measured bearings. Alternatively, one could make use of the geometric arguments of [20] for algebraically obtaining T (ψ j − ψ i ) from the available bearings. An example of this algebraic procedure for the case of 3 agents is given in the proof of Proposition II.10.…”

An Open-Source Hardware/Software Architecture for Quadrotor UAVs

“…On top of this basic setup the system permits the easy addition of onboard exteroceptive sensor, as done, e.g., in [3,2] by using onboard monocular cameras. The use of an onboard RGB-D sensor is currently under development.…”

“…The challenge is rather on how to exploit these systems as a flexible platform for implementing and validating complex and higherlevel tasks, often involving multiple robots interacting at the same time in partially structured or unstructured environments. Some examples in this sense can be found in, e.g., [14,12,2].…”