Dynamic Modeling of Rotor Flapping Dynamics of an Unmanned Helicopter and Investigation of Applicability of System Identification and Control using Approximate Model

Mathematical Modeling of the main rotor dynamics is very important in modeling of unmanned helicopters, and its quality and performance will play an effective role in ability of the model to behave the same as a real helicopter. There are different methods for modeling rotor dynamics which are different from each other in simplifying assumptions and relations complexity. In most investigations, the complete unmanned helicopter dynamic modeling is performed, applied and evaluated which decreases the concentration on main rotor modeling and its quality. In this paper, main rotor dynamics have been modeled independently using 2 different methods (theoretical method based on blade element theory and approximate method using 1st order dynamics for flapping). Considering complexities arisen in theoretical modeling method, using similarly behaving approximate model will make the final model more applicable. To do this, using system identification technique, the probability of using approximate model instead of theoretical one (which is a closer model to real rotor dynamics) has been investigated. After that, a robust control system is designed based on approximate model and its successful implementation in controlling the theoretical model, shows that it is possible to control the theoretical model using much simpler approximate one.