Heading rate controller for unmanned helicopters based on modified ADRC

A modified heading rate active disturbance rejection controller (ADRC) for miniature unmanned helicopters is presented to improve the transient performance and adaptability of working conditions. First, a tail-locking mathematical model is introduced, and the amplification factor is defined. Second, a standard ADRC controller is presented. Because the amplification factor plays an important role in both parts of the content and is primarily influenced by the main rotor speed, an online forgetting factor recursive least square algorithm is used to identify it, and the identification result is condensed into a function of the main rotor speed, adapting to various working conditions. This function is also included in the proposed ADRC controller to supplement the standard scheme. Finally, experiments were conducted on a small electric helicopter. A reduction of approximately 40% in the transient time (compared with an off-the-shelf PID controller) was achieved in the experiment. The comparative results show that the proposed ADRC scheme outperforms the classic PID and standard ADRC schemes in terms of transient performance and adaptability to working conditions.