MARS-Dragonfly: Agile and Robust Flight Control of Modular Aerial Robot Systems

TL;DR

This paper presents a novel control framework for Modular Aerial Robot Systems (MARS) that enhances agility, stability, and reconfigurability through a new mechanical design and a virtual quadrotor abstraction, validated in simulations and real-world tests.

Contribution

It introduces a comprehensive control approach combining passive docking, a force-torque virtual model, and a predictive allocation pipeline for MARS, enabling agile and stable flight across various configurations.

Findings

Successful real-world demonstration of MARS with 40° peak pitch.

Stable docking, locking, and separation achieved in experiments.

Average position error of 0.0896 meters in real-world tests.

Abstract

Modular Aerial Robot Systems (MARS) comprise multiple drone units with reconfigurable connected formations, providing high adaptability to diverse mission scenarios, fault conditions, and payload capacities. However, existing control algorithms for MARS rely on simplified quasi-static models and rule-based allocation, which generate discontinuous and unbounded motor commands. This leads to attitude error accumulation as the number of drone units scales, ultimately causing severe oscillations during docking, separation, and waypoint tracking. To address these limitations, we first design a compact mechanical system that enables passive docking, detection-free passive locking, and magnetic-assisted separation using a single micro servo. Second, we introduce a force-torque-equivalent and polytope-constraint virtual quadrotor that explicitly models feasible wrench sets. Together, these abstractions capture the full MARS dynamics and enable existing quadrotor controllers to be applied across different configurations. We further optimize the yaw angle that maximizes control authority to enhance agility. Third, building on this abstraction, we design a two-stage predictive-allocation pipeline: a constrained predictive tracker computes virtual inputs while respecting force/torque bounds, and a dynamic allocator maps these inputs to individual modules with balanced objectives to produce smooth, trackable motor commands. Simulations across over 10 configurations and real-world experiments demonstrate stable docking, locking, and separation, as well as effective control performance. To our knowledge, this is the first real-world demonstration of MARS achieving agile flight and transport with 40 deg peak pitch while maintaining an average position error of 0.0896 m. The video is available at: https://youtu.be/yqjccrIpz5o