Performance Analysis of Active Disturbance Rejection Control for Complex Articulated Ornithopter

This paper presents the design and performance analysis of the attitude control of an ornithopter that replicates the flapping wing motion of a bird. The flapping wing motion induces periodic vibrations and increases model uncertainty, making it essential to study attitude control strategies that exhibit high robustness to external disturbances specific to ornithopters. This study focuses on analyzing the attitude control performance of an ornithopter using active disturbance rejection control (ADRC), a controller that estimates disturbances using an observer and employs control actions to eliminate them. A baseline controller, namely the proportional-integral (PI) controller, is designed for comparative analysis, while the ADRC complements for the control input command of the baseline controller. The aircraft used in the experiments is self-designed and manufactured, equipped with active wing torsion mechanism and elevator as control inputs for roll and pitch axes, respectively. Aerodynamic coefficients related to control effectiveness are obtained through wind tunnel experiments. The analysis primarily evaluates the attitude control performance, including attitude command tracking, vibration in control signals, and robustness to external disturbances. The results demonstrate that the ADRC significantly reduces command tracking errors compared to the PI controller. Additionally, the ADRC effectively reduces high-frequency vibration in the control input, thereby improving roll control performance.