Nonlinear Flight Dynamics and Control of a Fixed-Wing Micro Air Vehicle: Numerical, System Identification and Experimental Investigations

The flight dynamics of Micro Air Vehicles (MAVs) exhibit significant nonlinear characteristics, which cannot be ignored in simulation or analysis. In this study, a full nonlinear simulation of the flight dynamics characteristics of a fixed-wing MAV is performed. To strengthen the developed nonlinear mathematical modeling, the MAV's mass properties and propulsion characteristics are experimentally investigated. Moreover, the aerodynamic characteristics of the designed fixed-wing MAV are experimentally measured in a wind tunnel. The experimental aerodynamics investigation includes the propeller wash effect and the same flight conditions of the MAV. These measured data are fed to the nonlinear flight dynamics model to improve its accuracy and ensure the nonlinear aerodynamics effect on the flight dynamics. The enhanced model is then validated against response experimental measurements of the MAV in the wind tunnel that is free to pitch at different control inputs and initial conditions. Furthermore, it is compared to the response of the system identification model. The nonlinear simulation and dynamic testing investigations indicate many nonlinear phenomena, such as the appearance of the limit cycle in the longitudinal flight. This paper shows that the aerodynamic center of MAV with a low aspect ratio in the low Reynolds number regime of flow can move as a response to flap deflection. The validated nonlinear mathematical model was used to evaluate the MAV's dynamics, design and evaluate a PID controller in flight conditions similar to the MAV's actual flying mission. Moreover, the presented model can be used for flapping-wing MAVs using time-dependent experimental measurements.