Height and attitude active disturbance rejection controller design of a small-scale helicopter

Small-scale helicopters are very attractive because of their unique features. However, autonomous flight control for small-scale helicopters is still a challenging work because they are naturally unstable, strongly nonlinear, and sensitive to disturbances. In this paper, we focus on the design of a height and attitude active disturbance rejection controller (ADRC) for a small-scale helicopter constructed in our lab. Firstly, a comprehensive nonlinear model for the platform is presented, which is obtained through first principles modeling and system identification. The controller is designed using backstepping technique incorporated with extended state observer (ESO), which is used to estimate the unknown disturbances. Then, the estimate is introduced into the control law to compensate for the disturbances. The design specifications of military rotorcraft are introduced to guide the controller design to achieve specified control performance. Considering the physical limitations, reference models are designed to shape the desired control responses. At last, several flight simulations are carried out to validate the effectiveness and robustness of the proposed controller. The results show that the proposed controller works well and Level 1 performance can be achieved.