Dynamic Compensation for Control of a Rotary wing UAV Using Positive Position Feedback

This paper presents a novel compensation method for the coupled fuselage-rotor mode of a Rotary wing Unmanned Aerial Vehicle (RUAV). The presence of stabilizer bar limits the performance of attitude control of an RUAV. In this paper, a Positive Position Feedback (PPF) is introduced to increase the stability margins and allow higher control bandwidth. The identified model is used to design a PPF controller to mitigate the presence of stabilizer bar. Parameters for the linear RUAV model are obtained by performing linear system identification about a few selected points. This identification process gives complete RUAV dynamics and is suitable for designing a Stability Augmentation System (SAS) of an RUAV. The identified parameters of an RUAV model are verified using experimental flight data and can be used to obtain the nonlinear model of an RUAV. The performance of the proposed algorithm is tested using a high-fidelity RUAV simulation model, which is validated through experimental flight data. The closed-loop response of the rotorcraft indicates that the desired attitude performance is achieved while ensuring that the coupled fuselage-rotor mode is effectively compensated without penalizing the phase response.