A Novel Coaxial Dual-Propeller Omnidirectional Tiltrotor Aircraft: Design and Control

To address the challenges in achieving plug-and-play functionality for tiltrotor aircraft, this article proposes a novel coaxial dual-propeller omnidirectional architecture that redefines modularity and operational flexibility. Unlike conventional designs requiring laborious offline calibration of thrust and reaction torque coefficients, our system employs a self-decoupling rotor configuration with coaxial propellers rotating synchronously in opposite directions. This design inherently cancels reaction torques and gyroscopic moments, eliminating the need for torque coefficient identification and retaining only the thrust coefficient as a dynamically coupled parameter. We further propose a hierarchical adaptive control framework that incorporates real-time thrust coefficient estimation based on translational dynamics. By integrating an online recursive least-squares estimator, the system autonomously adapt to different modules, including varying propeller geometries and payloads, without manual parameter tuning. This unified hardware–software codesign ensures seamless compatibility across component swaps. Experimental validation on a fully functional tiltrotor prototype demonstrates three key capabilities: 1) accurate 6-degree-of-freedom trajectory tracking with a position RMSE below 5 cm across varying tasks; 2) stable online thrust coefficient estimation under diverse configurations; and 3) significantly reduced setup time compared to conventional calibration-based systems.