Unsteady Aerodynamic Parameter Estimation for Multirotor Helicopters

Today, multirotor helicopters (MRHs) play an important role in a broad range of applications such as transportation, observation and construction, and the safety of MRH flight is a matter of great concern. This study contributes to clarifying an aerodynamic aspect that enables the prediction of MRH behavior in unsteady conditions through flight tests. In working towards a comprehensive mathematical model that determines unsteady aerodynamics, a quadcopter is equipped with a data acquisition system to gather flight data including acceleration, angular rates, flow angles, airspeed and rotational speed. Based on the data collected, the combined blade element momentum theory is utilized to calculate steady and unsteady aerodynamic parameters. It is found that the experimental aerodynamic coefficients agree well with the theoretical results for steady forward flight. However, the conventional theory was insufficient to model the aerodynamic parameters under unsteady conditions. A new model to predict aerodynamic parameters under unsteady flight is proposed and validated on the basis of the flight data.