Higher-Order System Identification and Control Design for a Coaxial Rotorcraft

The edm aerotec CoAX 600 rotorcraft was converted to an uncrewed aerial vehicle at the Technical University of Munich. In this work, a higher-order physics-based model of the system was identified based on flight test data and blade element momentum theory (BEMT). The paper describes the higher-order model structure and the system identification techniques used in the process. The validated model was used for control design and pilot training purposes. The simulation model consists of a physics-based model structure developed by coupling a dynamic rotor model with a rigid-body fuselage. Aerodynamic models for both the fuselage and the coaxial rotors contain unknown parameters that were estimated based on flight test data using a Maximum-Likelihood parameter estimation method in the time domain. The nonlinear model was linearized in hover, and the linearized model was used for control design and stability analysis. The design and validation of the flight controller are also discussed in the paper. The physics-based model allows for the comprehensive interpretation of the estimated parameters and the involved aerodynamic phenomena. Furthermore, it reduces the number of parameters estimated from flight data.