Aeromechanics and Control of a Shrouded Rotor Micro Air Vehicle in Hover and in Edgewise Flow

Abstract

Shrouded rotors are efficient in hover but are quite sensitive to disturbances in external flow. In this paper, the dynamics and control of a shrouded rotor micro air vehicle is studied in hover and when it is subjected to edgewise gust. The importance of incorporating a hingeless rotor in a shrouded rotor configuration was shown and was flight-tested in hover using a proportional-integral attitude feedback controller. In edgewise flow, the shrouded rotor produced up to 300% higher pitching moment than the unshrouded rotor. To counter this pitching moment, the control moments were about 80–100% higher for the shrouded rotor. Time domain attitude dynamics identification of the vehicle, restrained in translation, was conducted with and without the flybar. It was shown to be desirable to incorporate a flybarless rotor for improved maneuverability and hover efficiency. A linear quadratic regulator (LQR) controller was developed based on the extracted attitude dynamics model. Gust disturbance rejection capabilities of the controller were tested with the vehicle in edgewise flow using a spherical gimbal setup. The shrouded vehicle was found to tolerate up to 2 m/s of edgewise gusts, whereas the unshrouded configuration could reject gusts of up to 4.8 m/s.