Development and Validation of a Cross-Over Control Algorithm for Counter-Rotating Multi-Rotor Systems

The region where two counter-rotating propellers cross over each other significantly influences the instantaneous aerodynamics, affecting the noise and vibrations. Implementing a blade cross-over angular position controller can aid in detailed aerodynamic and acoustic studies, enabling performance optimization. This work developed and validated a cross-over angular position control algorithm for mechanically decoupled multi-rotor systems. The algorithm is integrated with an angular speed controller, offering algorithmic simplicity and ease of implementation. The robustness of the proposed algorithm was evaluated by testing the algorithm in counter-rotating side-by-side and co-axial propeller configurations. The controller’s performance was further assessed at two different inter-rotor spacings and across varying speeds corresponding to different aerodynamic interaction regimes. To independently verify the controller’s performance, a post-validation technique was developed using a high-speed camera and image processing techniques to identify the cross-over angular position. Experimental results demonstrate successful cross-over angular position control within $\pm 2^{\circ }$ at low (600) to high (1875) RPM and $\pm 4^{\circ }$ at the highest 2000 RPM across all tested configurations and inter-rotor spacing values.