Integrated structural parameter and robust controller design for attitude tracking maneuvers

Abstract

Complex nonlinearity and strong coupling in the pitch-yaw-roll of a rotorcraft make it difficult for the attitude control of unmanned aerial vehicles, especially in the presence of wind disturbances and plant uncertainties. To confront these problems, this paper presents a control scheme of two sequential steps, structural parameter determination and robust controller design, in order to achieve the desired attitude regulation performance and disturbance attenuation capability. For the structural parameter design, key structural parameters are specified such that the open-loop transfer functions, from torque inputs to angular velocities, exhibit positive-real properties in particular frequency ranges to incorporate robustness into the controller design. Then, a dual-loop structured controller is designed using dynamic inversion approaches and singular perturbation techniques. The controlled inner loop provides adequate decoupling such that the outer loop may control each Euler angle independently, and proportional-derivative control is used in each outer loop to achieve a desired attitude tracking performance. The effectiveness of the control scheme is verified via an attitude tracking example.