Flight Dynamics Model Identification of a Meso-Scale Twin-Cyclocopter in Hover

Abstract

In this paper a linear flight dynamics model of a micro twin cyclocopter is experimentally derived from flight test data and analyzed. The twin cyclocopter is a novel aerial vehicle that uses two cyclorotors spinning in the same direction to generate thrust, and a nose propeller to counter the reaction torque as well as provid additional thrust. This twin cyclocopter is unique for its size, design, and coaxial nose rotor that balances reaction torques along the vertical axis. AVICONmotion capture system was used to collect attitude and position data during perturbation maneuvers about hovering flight to excited the modes of the system. This data was used to extract a bare airframe linear time invariant f light dynamics model of the vehicle around the trim state, hover, using time-domain system identification techniques. The parameters of the model were derived using least squares between the states and control (regressors) and the outputs. The method of stepwise regression was used to add regressors to the model, and statistical metrics were used to determine the significance of the selected regressors. The model illustrates some unique flight qualities of this micro air vehicle. It is shown that the roll and yaw modes are gyroscopically coupled with a high and a low frequency mode, both of which are stable. Two different control methods for yaw are implemented and their differences quantified: thrust vectoring of the cyclorotors and differential torque of the coaxial nose. The former was shown to be more effective in controlling yaw. The coupled nature of the cyclocopter and unique configuration of control actuators presents opportunities for controls techniques to improve handling qualities.