Tying Knots in the Air: Reducing the Number of Quadrotors for Aerial Knot Formation
Tongshu Wu, Edward Caleb Lopez Tarazona, Diego S. D'Antonio, David Saldaña
AI summary
Problem
Autonomous midair knot formation is hindered by the complex dynamics of flexible cables and the excessive number of robots required by existing grid-based methods. This work addresses how to minimize the robot team size while strictly preserving the knot's topological structure.
Approach
The method employs a Loop Consistency Filter to identify the minimal set of support robots required to maintain knot topology from a grid diagram, then reconstructs smooth, physically feasible trajectories using a spring-damper model and straightening forces.
Key results
- Reduces required quadrotor count by at least 50% compared to baseline grid methods
- Introduces a Loop Consistency Filter for minimal topology-preserving support selection
- Reconstructs continuous Cartesian trajectories via spring-damper and straightening forces
- Demonstrates first experimental midair knot formation with physical quadrotors
Why it matters
Enables scalable, efficient aerial cable manipulation for logistics, construction, and payload securing without relying on rigid connectors.
Abstract
Knots provide compact, lightweight, and me- chanically stable configurations that are invaluable for aerial transportation and construction. However, autonomous knot formation in midair remains an open challenge due to the dexterity and complexity of manipulating flexible cables. In this paper, we present a method for midair knot formation that employs two types of aerial robots: lifting robots, which hold the cable endpoints, and support robots, which stabilize intermediate spans to enable interlacing. Our approach focuses on minimizing the number of support robots required while ensuring that the knot’s topology is preserved. Our method proceeds in three stages: (i) encode the knot projection as a grid of directional segments and crossings, (ii) apply our Loop Consistency Filter (LCF) to identify the minimal set of support robots required to preserve topology, and (iii) reconstruct continuous Cartesian trajectories using a cable model governed by a spring–damper force and a straightening force. Our results show a reduction in the required robots to form a knot of at least fifty percent compared to the baseline grid-based method. We demonstrate that our method is effective on actual robots, enabling the formation of knots with multiple quadrotors.