An introduction to electric thruster modeling for stratospheric airship

The stratospheric airship uses the electric thrusters composed of motors and large diameter propellers to generate the forward thrust and heading manipulation torque. As the actuators of flight control, electric thrusters have an important impact on the station-keeping and flight-control performance. Due to the high-altitude environment and low-speed flight of big volumetric stratospheric airships, the operating of electric thrusters is significantly different from that of electric aircraft, which makes the analysis and modeling of electric thrusters difficult. In this paper, the characteristics of motors and propellers for stratospheric airship is analyzed at first. Then, the propeller and motor model expressions are summarized respectively, mainly concentrating on the relationship between torque, thrust, advance speed and rotational speed. Benefited from the methods in the field of marine propellers, a quantitative characterization method for the interaction between propeller and airship hull is introduced. Through the mechanical motion equation of the motor, the dynamic matching model between the motor output electromagnetic torque and the propeller load torque is described. An example is used to illustrate the modeling process. Finally, some of the challenging issues in engineering practice are discussed.